Miscellany

Jai Ganesh · 2023-05-19 15:08:47

1779) Gastroenteritis

Gist

What is gastroenteritis? Gastroenteritis is an inflammation of the lining of the stomach and intestines. The main symptoms include vomiting and diarrhea. It is usually not serious in healthy people, but it can sometimes lead to dehydration or cause severe symptoms.

Details

Gastroenteritis, also known as infectious diarrhea and gastro, is an inflammation of the gastrointestinal tract including the stomach and intestine. Symptoms may include diarrhea, vomiting, and abdominal pain. Fever, lack of energy, and dehydration may also occur. This typically lasts less than two weeks. It is not related to influenza, even though in the U.S. it is sometimes called the "stomach flu".

Gastroenteritis is usually caused by viruses; however, gut bacteria, parasites, and fungi can also cause gastroenteritis. In children, rotavirus is the most common cause of severe disease. In adults, norovirus and Campylobacter are common causes. Eating improperly prepared food, drinking contaminated water or close contact with a person who is infected can spread the disease. Treatment is generally the same with or without a definitive diagnosis, so testing to confirm is usually not needed.

For young children in impoverished countries, prevention includes hand washing with soap, drinking clean water, breastfeeding babies instead of using formula, and proper disposal of human waste. The rotavirus vaccine is recommended as a prevention for children. Treatment involves getting enough fluids. For mild or moderate cases, this can typically be achieved by drinking oral rehydration solution (a combination of water, salts and sugar). In those who are breastfed, continued breastfeeding is recommended. For more severe cases, intravenous fluids may be needed. Fluids may also be given by a nasogastric tube. Zinc supplementation is recommended in children. Antibiotics are generally not needed. However, antibiotics are recommended for young children with a fever and bloody diarrhea.

In 2015, there were two billion cases of gastroenteritis, resulting in 1.3 million deaths globally. Children and those in the developing world are affected the most. In 2011, there were about 1.7 billion cases, resulting in about 700,000 deaths of children under the age of five. In the developing world, children less than two years of age frequently get six or more infections a year. It is less common in adults, partly due to the development of immunity.

Signs and symptoms

Gastroenteritis usually involves both diarrhea and vomiting. Sometimes, only one or the other is present. This may be accompanied by abdominal cramps. Signs and symptoms usually begin 12–72 hours after contracting the infectious agent. If due to a virus, the condition usually resolves within one week. Some viral infections also involve fever, fatigue, headache and muscle pain. If the stool is bloody, the cause is less likely to be viral and more likely to be bacterial. Some bacterial infections cause severe abdominal pain and may persist for several weeks.

Children infected with rotavirus usually make a full recovery within three to eight days. However, in poor countries treatment for severe infections is often out of reach and persistent diarrhea is common. Dehydration is a common complication of diarrhea. Severe dehydration in children may be recognized if the skin color and position returns slowly when pressed. This is called "prolonged capillary refill" and "poor skin turgor". Abnormal breathing is another sign of severe dehydration. Repeat infections are typically seen in areas with poor sanitation, and malnutrition. Stunted growth and long-term cognitive delays can result.

Reactive arthritis occurs in 1% of people following infections with Campylobacter species. Guillain–Barré syndrome occurs in 0.1%. Hemolytic uremic syndrome (HUS) may occur due to infection with Shiga toxin-producing Escherichia coli or Shigella species. HUS causes low platelet counts, poor kidney function, and low red blood cell count (due to their breakdown). Children are more predisposed to getting HUS than adults. Some viral infections may produce benign infantile seizures.

Cause

Viruses (particularly rotavirus (in children) and norovirus (in adults)) and the bacteria Escherichia coli and Campylobacter species are the primary causes of gastroenteritis. There are, however, many other infectious agents that can cause this syndrome including parasites and fungus. Non-infectious causes are seen on occasion, but they are less likely than a viral or bacterial cause. Risk of infection is higher in children due to their lack of immunity. Children are also at higher risk because they are less likely to practice good hygiene habits. Children living in areas without easy access to water and soap are especially vulnerable.

Viral

Rotaviruses, noroviruses, adenoviruses, and astroviruses are known to cause viral gastroenteritis. Rotavirus is the most common cause of gastroenteritis in children, and produces similar rates in both the developed and developing world. Viruses cause about 70% of episodes of infectious diarrhea in the pediatric age group. Rotavirus is a less common cause in adults due to acquired immunity. Norovirus is the cause in about 18% of all cases. Generally speaking, viral gastroenteritis accounts for 21–40% of the cases of infectious diarrhea in developed countries.

Norovirus is the leading cause of gastroenteritis among adults in America accounting for about 90% of viral gastroenteritis outbreaks. These localized epidemics typically occur when groups of people spend time proximate to each other, such as on cruise ships, in hospitals, or in restaurants. People may remain infectious even after their diarrhea has ended. Norovirus is the cause of about 10% of cases in children.

Bacterial

In some countries, Campylobacter jejuni is the primary cause of bacterial gastroenteritis, with half of these cases associated with exposure to poultry. In children, bacteria are the cause in about 15% of cases, with the most common types being Escherichia coli, Salmonella, Shigella, and Campylobacter species. If food becomes contaminated with bacteria and remains at room temperature for a period of several hours, the bacteria multiply and increase the risk of infection in those who consume the food. Some foods commonly associated with illness include raw or undercooked meat, poultry, seafood, and eggs; raw sprouts; unpasteurized milk and soft cheeses; and fruit and vegetable juices. In the developing world, especially sub-Saharan Africa and Asia, cholera is a common cause of gastroenteritis. This infection is usually transmitted by contaminated water or food.

Toxigenic Clostridium difficile is an important cause of diarrhea that occurs more often in the elderly. Infants can carry these bacteria without developing symptoms. It is a common cause of diarrhea in those who are hospitalized and is frequently associated with antibiotic use. Staphylococcus aureus infectious diarrhea may also occur in those who have used antibiotics. Acute "traveler's diarrhea" is usually a type of bacterial gastroenteritis, while the persistent form is usually parasitic. Acid-suppressing medication appears to increase the risk of significant infection after exposure to a number of organisms, including Clostridium difficile, Salmonella, and Campylobacter species. The risk is greater in those taking proton pump inhibitors than with H2 antagonists.

Parasitic

A number of parasites can cause gastroenteritis. Giardia lamblia is most common, but Entamoeba histolytica, Cryptosporidium spp., and other species have also been implicated. As a group, these agents comprise about 10% of cases in children. Giardia occurs more commonly in the developing world, but this type of illness can occur nearly everywhere. It occurs more commonly in persons who have traveled to areas with high prevalence, children who attend day care, men who have physical relationship with men, and following disasters.

Transmission

Transmission may occur from drinking contaminated water or when people share personal objects. Water quality typically worsens during the rainy season and outbreaks are more common at this time. In areas with four seasons, infections are more common in the winter. Worldwide, bottle-feeding of babies with improperly sanitized bottles is a significant cause. Transmission rates are also related to poor hygiene, (especially among children), in crowded households, and in those with poor nutritional status. Adults who have developed immunities might still carry certain organisms without exhibiting symptoms. Thus, adults can become natural reservoirs of certain diseases. While some agents (such as Shigella) only occur in primates, others (such as Giardia) may occur in a wide variety of animals.

Non-infectious

There are a number of non-infectious causes of inflammation of the gastrointestinal tract. Some of the more common include medications (like NSAIDs), certain foods such as lactose (in those who are intolerant), and gluten (in those with celiac disease). Crohn's disease is also a non-infectious cause of (often severe) gastroenteritis. Disease secondary to toxins may also occur. Some food-related conditions associated with nausea, vomiting, and diarrhea include: ciguatera poisoning due to consumption of contaminated predatory fish, scombroid associated with the consumption of certain types of spoiled fish, tetrodotoxin poisoning from the consumption of puffer fish among others, and botulism typically due to improperly preserved food.

In the United States, rates of emergency department use for noninfectious gastroenteritis dropped 30% from 2006 until 2011. Of the twenty most common conditions seen in the emergency department, rates of noninfectious gastroenteritis had the largest decrease in visits in that time period.

Pathophysiology

Gastroenteritis is defined as vomiting or diarrhea due to inflammation of the small or large bowel, often due to infection. The changes in the small bowel are typically noninflammatory, while the ones in the large bowel are inflammatory. The number of pathogens required to cause an infection varies from as few as one (for Cryptosporidium) to as many as {10}^{8} (for Vibrio cholerae).

Diagnosis

Gastroenteritis is typically diagnosed clinically, based on a person's signs and symptoms. Determining the exact cause is usually not needed as it does not alter the management of the condition.

However, stool cultures should be performed in those with blood in the stool, those who might have been exposed to food poisoning, and those who have recently traveled to the developing world. It may also be appropriate in children younger than 5, old people, and those with poor immune function. Diagnostic testing may also be done for surveillance. As hypoglycemia occurs in approximately 10% of infants and young children, measuring serum glucose in this population is recommended. Electrolytes and kidney function should also be checked when there is a concern about severe dehydration.

Dehydration

A determination of whether or not the person has dehydration is an important part of the assessment, with dehydration typically divided into mild (3–5%), moderate (6–9%), and severe (≥10%) cases. In children, the most accurate signs of moderate or severe dehydration are a prolonged capillary refill, poor skin turgor, and abnormal breathing. Other useful findings (when used in combination) include sunken eyes, decreased activity, a lack of tears, and a dry mouth. A normal urinary output and oral fluid intake is reassuring. Laboratory testing is of little clinical benefit in determining the degree of dehydration. Thus the use of urine testing or ultrasounds is generally not needed.

Differential diagnosis

Other potential causes of signs and symptoms that mimic those seen in gastroenteritis that need to be ruled out include appendicitis, volvulus, inflammatory bowel disease, urinary tract infections, and diabetes mellitus. Pancreatic insufficiency, short bowel syndrome, Whipple's disease, coeliac disease, and laxative abuse should also be considered. The differential diagnosis can be complicated somewhat if the person exhibits only vomiting or diarrhea (rather than both).

Appendicitis may present with vomiting, abdominal pain, and a small amount of diarrhea in up to 33% of cases. This is in contrast to the large amount of diarrhea that is typical of gastroenteritis. Infections of the lungs or urinary tract in children may also cause vomiting or diarrhea. Classical diabetic ketoacidosis (DKA) presents with abdominal pain, nausea, and vomiting, but without diarrhea. One study found that 17% of children with DKA were initially diagnosed as having gastroenteritis.

Jai Ganesh · 2023-05-20 14:26:57

1780) Microform

Summary

Microform, also called Microcopy, or Microrecord, is any process, photographic or electronic, for reproducing printed matter or other graphic material in a much-reduced size, which can then be re-enlarged by an optical apparatus for reading or reproduction. Microform systems provide durable, extremely compact, and easily accessible file records.

The earliest large-scale commercial use of greatly reduced-size copying onto narrow rolls of film (microfilm) resulted from the introduction of the Recordak system by the Eastman Kodak Company in 1928. Continuous, automatic cameras photographed documents on 16-millimetre film, and the first use was for copying checks in bank transit or clearing work. But it soon spread to a great variety of other applications in business, government, and education; and 35-millimetre film was used as well as 16-millimetre.

The science of microphotography burgeoned in the late 20th century, with scores of processes and a variety of miniaturizations being introduced. Generally speaking, a microform may be in the form of continuous media, such as roll or cartridge microfilm, or in that of individual and physically separate records, such as film chips (microfilm containing coded microimages, to be used in automatic retrieval systems) or microfiche (a sheet of microfilm displaying at the top a title or code readable with the naked eye). Use of the microform permits considerable space saving. The microform usually utilizes photographic techniques; however, other methods such as video magnetic tape recording have been used. Most microform techniques also permit the document file to be duplicated easily for dissemination or filing in different places.

Automated equipment for unit records or continuous media is also available to handle microforms at high speeds. Such equipment typically stores the microform image with a corresponding address number in the machine file. Given a request for a copy, the equipment automatically selects the proper image from the file and prepares a copy, either a printed paper copy of the original or a microform copy, depending upon the equipment. Some automated microform systems also include the indexing information in machine-coded form with the image. This permits a mechanized index search to be made; in some cases it can result in rapid delivery of copies of those records selected in response to the index query.

Details

Microforms are scaled-down reproductions of documents, typically either films or paper, made for the purposes of transmission, storage, reading, and printing. Microform images are commonly reduced to about 4% or 1⁄25 of the original document size. For special purposes, greater optical reductions may be used.

Three formats are common: microfilm (reels), microfiche (flat sheets), and aperture cards. Microcards, also known as "micro-opaques", a format no longer produced, were similar to microfiche, but printed on cardboard rather than photographic film.

Uses

Systems that mount microfilm images in punched cards have been widely used for archival storage of engineering information.

For example, when airlines demand archival engineering drawings to support purchased equipment (in case the vendor goes out of business, for example), they normally specify punch-card-mounted microfilm with an industry-standard indexing system punched into the card. This permits automated reproduction, as well as permitting mechanical card-sorting equipment to sort and select microfilm drawings.

Aperture card mounted microfilm is roughly 3% of the size and space of conventional paper or vellum engineering drawings. Some military contracts around 1980 began to specify digital storage of engineering and maintenance data because the expenses were even lower than microfilm, but these programs are now finding it difficult to purchase new readers for the old formats.

Microfilm first saw military use during the Franco-Prussian War of 1870–71. During the Siege of Paris, the only way for the provincial government in Tours to communicate with Paris was by pigeon post. As the pigeons could not carry paper dispatches, the Tours government turned to microfilm. Using a microphotography unit evacuated from Paris before the siege, clerks in Tours photographed paper dispatches and compressed them to microfilm, which were carried by homing pigeons into Paris and projected by magic lantern while clerks copied the dispatches onto paper.

Additionally, the US Victory Mail, and the British "Airgraph" system it was based on, were used for delivering mail between those at home and troops serving overseas during World War II. The systems worked by photographing large amounts of censored mail reduced to thumb-nail size onto reels of microfilm, which weighed much less than the originals would have. The film reels were shipped by priority air freight to and from the home fronts, sent to their prescribed destinations for enlarging at receiving stations near the recipients, and printed out on lightweight photo paper. These facsimiles of the letter-sheets were reproduced about one-quarter the original size and the miniature mails were then delivered to the addressee. Use of these microfilm systems saved significant volumes of cargo capacity needed for war supplies. An additional benefit was that the small, lightweight reels of microfilm were almost always transported by air, and as such were delivered much more quickly than any surface mail service could have managed.

Libraries began using microfilm in the mid-20th century as a preservation strategy for deteriorating newspaper collections. Books and newspapers that were deemed in danger of decay could be preserved on film and thus access and use could be increased. Microfilming was also a space-saving measure. In his 1945 book, The Scholar and the Future of the Research Library, Fremont Rider calculated that research libraries were doubling in space every sixteen years. His suggested solution was microfilming, specifically with his invention, the microcard. Once items were put onto film, they could be removed from circulation and additional shelf space would be made available for rapidly expanding collections. The microcard was superseded by microfiche. By the 1960s, microfilming had become standard policy.

In 1948, the Australian Joint Copying Project started; the intention to film records and archives from the United Kingdom relating to Australia and the Pacific. Over 10,000 reels were produced, making it one of the largest projects of its kind.

Around the same time, Licensed Betting Offices in the UK began using microphotography as a means of keeping compact records of bets taken. Betting shop customers would sometimes attempt to amend their betting slip receipt to attempt fraud, and so the microphotography camera (which also generally contained its own independent time-piece) found use as a definitive means of recording the exact details of each and every bet taken. The use of microphotography has now largely been replaced by digital 'bet capture' systems, which also allow a computer to settle the returns for each bet once the details of the wager have been 'translated' into the system by an employee. The added efficiency of this digital system has ensured that there are now very few, if indeed any, betting offices continuing to use microfilm cameras in the UK.

Visa and National City use microfilm (roll microfilm and fiche) to store financial, personal, and legal records.

Source code for computer programs was printed to microfiche during the 1970s and distributed to customers in this form.

Additionally, microfiche was used to write out long casework for some proofs such as the four color theorem.

Additional Information

Microforms are microreproductions of documents for transmission, storage, reading and printing. Microform images are commonly reduced about 25 times from the original document size. For special purposes, greater optical reductions may be used. All microform images may be provided as positives or negatives, more often the second. Microforms often come in three formats: microfilm (reels), aperture cards and microfiche (flat sheets). Microcards were similar to microfiche, but printed on paper cardboard rather than photographic films.

In the middle of the twentieth century, microforms became popular in library communities. Periodicals, books, and other collections were converted into microform. However, digital preservation has become increasingly popular, causing the decline of microform preservation.

Microform in the twentieth century

Microfom is used primarily for the preservation of documents, images, architectural or technological drawings, maps, and other forms of information. While microform was a primary preservation method in the twentieth century, digital preservation has increasingly become popular since.

Despite the increasing popularity of digital preservation, microform is still in use today in various institutions such as libraries and archives for a number of reasons.

First, filmed images are analog images of the original, reduced in size, and users can access the information with a simple equipment such as a magnifier. Digital technologies, however, require much more complex devices. Furthermore, when computer programs are updated, the original digital data may become inaccessible. Furthermore, the life span of CDs, DVDs, and other digital storage devices is still uncertain. For these reasons, digital preservation requires constant data migration. On the other hand, microforms are expected to last about 500 years, if they are properly preserved.

While microform has a number of advantages, it lacks some functions digital preservation that has: search capability; quick data transfer from one location to another location; massive storage capacity; easy manipulation of data.

To remedy some of those disadvantages, data preserved in microform are also digitized. At some institutions, users can choose to access information storage in various formats. For example, the Library of Congress in the U.S. provides copies of their collection in various formats. Users can choose and request from the followings:

* 35mm microfilm
* film to paper
* original filming
* photocopying
* cartographic scanning
* digital images to CD-ROM
* all formats of photographic reproduction

Today, libraries and archives use multiple preservation medium including paper, microform, and digital medium. The same information is often preserved in multiple formats. Since each format has its own advantages and disadvantages, all of these formats will be used in the near future.

Jai Ganesh · 2023-05-21 00:17:06

1781) Concrete

Gist

Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material.

Concrete is the most commonly used man-made material on earth. It is an important construction material used extensively in buildings, bridges, roads and dams. Its uses range from structural applications, to paviours, kerbs, pipes and drains.

Concrete is a composite material, consisting mainly of Portland cement, water and aggregate (gravel, sand or rock). When these materials are mixed together, they form a workable paste which then gradually hardens over time.

Summary

Concrete, in construction, is a structural material consisting of a hard, chemically inert particulate substance, known as aggregate (usually sand and gravel), that is bonded together by cement and water.

Among the ancient Assyrians and Babylonians, the bonding substance most often used was clay. The Egyptians developed a substance more closely resembling modern concrete by using lime and gypsum as binders. Lime (calcium oxide), derived from limestone, chalk, or (where available) oyster shells, continued to be the primary pozzolanic, or cement-forming, agent until the early 1800s. In 1824 an English inventor, Joseph Aspdin, burned and ground together a mixture of limestone and clay. This mixture, called portland cement, has remained the dominant cementing agent used in concrete production.

Aggregates are generally designated as either fine (ranging in size from 0.025 to 6.5 mm [0.001 to 0.25 inch]) or coarse (from 6.5 to 38 mm [0.25 to 1.5 inch] or larger). All aggregate materials must be clean and free from admixture with soft particles or vegetable matter, because even small quantities of organic soil compounds result in chemical reactions that seriously affect the strength of the concrete.

Concrete is characterized by the type of aggregate or cement used, by the specific qualities it manifests, or by the methods used to produce it. In ordinary structural concrete, the character of the concrete is largely determined by a water-to-cement ratio. The lower the water content, all else being equal, the stronger the concrete. The mixture must have just enough water to ensure that each aggregate particle is completely surrounded by the cement paste, that the spaces between the aggregate are filled, and that the concrete is liquid enough to be poured and spread effectively. Another durability factor is the amount of cement in relation to the aggregate (expressed as a three-part ratio—cement to fine aggregate to coarse aggregate). Where especially strong concrete is needed, there will be relatively less aggregate.

The strength of concrete is measured in pounds per square inch or kilograms per square centimetre of force needed to crush a sample of a given age or hardness. Concrete’s strength is affected by environmental factors, especially temperature and moisture. If it is allowed to dry prematurely, it can experience unequal tensile stresses that in an imperfectly hardened state cannot be resisted. In the process known as curing, the concrete is kept damp for some time after pouring to slow the shrinkage that occurs as it hardens. Low temperatures also adversely affect its strength. To compensate for this, an additive such as calcium chloride is mixed in with the cement. This accelerates the setting process, which in turn generates heat sufficient to counteract moderately low temperatures. Large concrete forms that cannot be adequately covered are not poured in freezing temperatures.

Concrete that has been hardened onto imbedded metal (usually steel) is called reinforced concrete, or ferroconcrete. Its invention is usually attributed to Joseph Monier, a Parisian gardener who made garden pots and tubs of concrete reinforced with iron mesh; he received a patent in 1867. The reinforcing steel, which may take the form of rods, bars, or mesh, contributes tensile strength. Plain concrete does not easily withstand stresses such as wind action, earthquakes, and vibrations and other bending forces and is therefore unsuitable in many structural applications. In reinforced concrete, the tensile strength of steel and the compressional strength of concrete render a member capable of sustaining heavy stresses of all kinds over considerable spans. The fluidity of the concrete mix makes it possible to position the steel at or near the point where the greatest stress is anticipated.

Another innovation in masonry construction is the use of prestressed concrete. It is achieved by either pretensioning or posttensioning processes. In pretensioning, lengths of steel wire, cables, or ropes are laid in the empty mold and then stretched and anchored. After the concrete has been poured and allowed to set, the anchors are released and, as the steel seeks to return to its original length, it compresses the concrete. In the posttensioning process, the steel is run through ducts formed in the concrete. When the concrete has hardened, the steel is anchored to the exterior of the member by some sort of gripping device. By applying a measured amount of stretching force to the steel, the amount of compression transmitted to the concrete can be carefully regulated. Prestressed concrete neutralizes the stretching forces that would rupture ordinary concrete by compressing an area to the point at which no tension is experienced until the strength of the compressed section is overcome. Because it achieves strength without using heavy steel reinforcements, it has been used to great effect to build lighter, shallower, and more elegant structures such as bridges and vast roofs.

In addition to its potential for immense strength and its initial ability to adapt to virtually any form, concrete is fire resistant and has become one of the most common building materials in the world.

Details

Concrete is a composite material composed of fine and coarse aggregate bonded together with a fluid cement (cement paste) that hardens (cures) over time. Concrete is the second-most-used substance in the world after water, and is the most widely used building material. Its usage worldwide, ton for ton, is twice that of steel, wood, plastics, and aluminium combined.[citation needed] Globally, the ready-mix concrete industry, the largest segment of the concrete market, is projected to exceed $600 billion in revenue by 2025. This widespread use results in a number of environmental impacts. Most notably, the production process for cement produces large volumes of greenhouse gas emissions, leading to net 8% of global emissions. Other environmental concerns include widespread illegal sand mining, impacts on the surrounding environment such as increased surface runoff or urban heat island effect, and potential public health implications from toxic ingredients. Significant research and development is being done to try to reduce the emissions or make concrete a source of carbon sequestration, and increase recycled and secondary raw materials content into the mix to achieve a circular economy. Concrete is expected to be a key material for structures resilient to climate disasters, as well as a solution to mitigate the pollution of other industries, capturing wastes such as coal fly ash or bauxite tailings and residue.

When aggregate is mixed with dry Portland cement and water, the mixture forms a fluid slurry that is easily poured and molded into shape. The cement reacts with the water through a process called concrete hydration that hardens over several hours to form a hard matrix that binds the materials together into a durable stone-like material that has many uses. This time allows concrete to not only be cast in forms, but also to have a variety of tooled processes preformed. The hydration process is exothermic, which means ambient temperature plays a significant role in how long it takes concrete to set. Often, additives (such as pozzolans or superplasticizers) are included in the mixture to improve the physical properties of the wet mix, delay or accelerate the curing time, or otherwise change the finished material. Most concrete is poured with reinforcing materials (such as rebar) embedded to provide tensile strength, yielding reinforced concrete.

In the past, lime based cement binders, such as lime putty, were often used but sometimes with other hydraulic cements, (water resistant) such as a calcium aluminate cement or with Portland cement to form Portland cement concrete (named for its visual resemblance to Portland stone). Many other non-cementitious types of concrete exist with other methods of binding aggregate together, including asphalt concrete with a bitumen binder, which is frequently used for road surfaces, and polymer concretes that use polymers as a binder. Concrete is distinct from mortar. Whereas concrete is itself a building material, mortar is a bonding agent that typically holds bricks, tiles and other masonry units together.

Etymology

The word concrete comes from the Latin word "concretus" (meaning compact or condensed), the perfect passive participle of "concrescere", from "con-" (together) and "crescere" (to grow).

Properties

Concrete has relatively high compressive strength, but much lower tensile strength. Therefore, it is usually reinforced with materials that are strong in tension (often steel). The elasticity of concrete is relatively constant at low stress levels but starts decreasing at higher stress levels as matrix cracking develops. Concrete has a very low coefficient of thermal expansion and shrinks as it matures. All concrete structures crack to some extent, due to shrinkage and tension. Concrete that is subjected to long-duration forces is prone to creep.

Tests can be performed to ensure that the properties of concrete correspond to specifications for the application.

The ingredients affect the strengths of the material. Concrete strength values are usually specified as the lower-bound compressive strength of either a cylindrical or cubic specimen as determined by standard test procedures.

The strengths of concrete is dictated by its function. Very low-strength—14 MPa (2,000 psi) or less—concrete may be used when the concrete must be lightweight. Lightweight concrete is often achieved by adding air, foams, or lightweight aggregates, with the side effect that the strength is reduced. For most routine uses, 20 to 32 MPa (2,900 to 4,600 psi) concrete is often used. 40 MPa (5,800 psi) concrete is readily commercially available as a more durable, although more expensive, option. Higher-strength concrete is often used for larger civil projects. Strengths above 40 MPa (5,800 psi) are often used for specific building elements. For example, the lower floor columns of high-rise concrete buildings may use concrete of 80 MPa (11,600 psi) or more, to keep the size of the columns small. Bridges may use long beams of high-strength concrete to lower the number of spans required. Occasionally, other structural needs may require high-strength concrete. If a structure must be very rigid, concrete of very high strength may be specified, even much stronger than is required to bear the service loads. Strengths as high as 130 MPa (18,900 psi) have been used commercially for these reasons.

Energy efficiency

The cement produced for making concrete accounts for about 8% of worldwide CO2 emissions per year (compared to, e.g., global aviation at 1.9%). The two largest sources of CO2 are produced by the cement manufacturing process, arising from (1) the decarbonation reaction of limestone in the cement kiln (T ≈ 950 °C), and (2) from the combustion of fossil fuel to reach the sintering temperature (T ≈ 1450 °C) of cement clinker in the kiln. The energy required for extracting, crushing, and mixing the raw materials (construction aggregates used in the concrete production, and also limestone and clay feeding the cement kiln) is lower. Energy requirement for transportation of ready-mix concrete is also lower because it is produced nearby the construction site from local resources, typically manufactured within 100 kilometers of the job site. The overall embodied energy of concrete at roughly 1 to 1.5 megajoules per kilogram is therefore lower than for many structural and construction materials.

Once in place, concrete offers a great energy efficiency over the lifetime of a building. Concrete walls leak air far less than those made of wood frames. Air leakage accounts for a large percentage of energy loss from a home. The thermal mass properties of concrete increase the efficiency of both residential and commercial buildings. By storing and releasing the energy needed for heating or cooling, concrete's thermal mass delivers year-round benefits by reducing temperature swings inside and minimizing heating and cooling costs. While insulation reduces energy loss through the building envelope, thermal mass uses walls to store and release energy. Modern concrete wall systems use both external insulation and thermal mass to create an energy-efficient building. Insulating concrete forms (ICFs) are hollow blocks or panels made of either insulating foam or rastra that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.

Fire safety

Concrete buildings are more resistant to fire than those constructed using steel frames, since concrete has lower heat conductivity than steel and can thus last longer under the same fire conditions. Concrete is sometimes used as a fire protection for steel frames, for the same effect as above. Concrete as a fire shield, for example Fondu fyre, can also be used in extreme environments like a missile launch pad.

Options for non-combustible construction include floors, ceilings and roofs made of cast-in-place and hollow-core precast concrete. For walls, concrete masonry technology and Insulating Concrete Forms (ICFs) are additional options. ICFs are hollow blocks or panels made of fireproof insulating foam that are stacked to form the shape of the walls of a building and then filled with reinforced concrete to create the structure.

Concrete also provides good resistance against externally applied forces such as high winds, hurricanes, and tornadoes owing to its lateral stiffness, which results in minimal horizontal movement. However, this stiffness can work against certain types of concrete structures, particularly where a relatively higher flexing structure is required to resist more extreme forces.

Earthquake safety

As discussed above, concrete is very strong in compression, but weak in tension. Larger earthquakes can generate very large shear loads on structures. These shear loads subject the structure to both tensile and compressional loads. Concrete structures without reinforcement, like other unreinforced masonry structures, can fail during severe earthquake shaking. Unreinforced masonry structures constitute one of the largest earthquake risks globally. These risks can be reduced through seismic retrofitting of at-risk buildings, (e.g. school buildings in Istanbul, Turkey).

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Jai Ganesh · 2023-05-21 18:16:05

1782) Silver coin

Silver coins are considered the oldest mass-produced form of coinage. Silver has been used as a coinage metal since the times of the Greeks; their silver drachmas were popular trade coins. The ancient Persians used silver coins between 612–330 BC. Before 1797, British pennies were made of silver.

As with all collectible coins, many factors determine the value of a silver coin, such as its rarity, demand, condition and the number originally minted. Ancient silver coins coveted by collectors include the Denarius and Miliarense, while more recent collectible silver coins include the Morgan Dollar and the Spanish Milled Dollar.

Other than collector's silver coins, silver bullion coins are popular among people who desire a "hedge" against currency inflation or store of value. Silver has an international currency symbol of XAG under ISO 4217.

Origins and early development of silver coins

The earliest coins in the world were minted in the kingdom of Lydia in Asia Minor around 600 BC. The coins of Lydia were made of electrum, which is a naturally occurring alloy of gold and silver, that was available within the territory of Lydia. The concept of coinage, i.e. stamped lumps of metal of a specified weight, quickly spread to adjacent regions, such as Aegina. In these neighbouring regions, inhabited by Greeks, coins were mostly made of silver. As Greek merchants traded with Greek communities (colonies) throughout the Mediterranean Sea, the Greek coinage concept soon spread through trade to the entire Mediterranean region. These early Greek silver coins were denominated in staters or drachmas and its fractions (obols).

More or less simultaneously with the development of the Lydian and Greek coinages, a coinage system was developed independently in China. The Chinese coins, however, were a different concept and they were made of bronze.

In the Mediterranean region, the silver and other precious metal coins were later supplemented with local bronze coinages, that served as small change, useful for transactions where small sums were involved.

The coins of the Greeks were issued by a great number of city-states, and each coin carried an indication of its place of origin. The coinage systems were not entirely the same from one place to another. However, the so-called Attic standard, Corinthian standard, Aiginetic standard and other standards defined the proper weight of each coin. Each of these standards were used in multiple places throughout the Mediterranean region.

In the 4th century BC, the Kingdom of Macedonia came to dominate the Greek world. The most powerful of their kings, Alexander the Great eventually launched an attack on the Persian Empire, defeating and conquering it. Alexander's Empire fell apart after his death in 323 BC, and the eastern mediterranean region and western Asia (previously Persian territory) were divided into a small number of kingdoms, replacing the city-state as the principal unit of Greek government. Greek coins were now issued by kings, and only to a lesser extent by cities. Greek rulers were now minting coins as far away as Egypt and central Asia. The tetradrachm (four drachms) was a popular coin throughout the region. This era is referred to as the hellenistic era.

While much of the Greek world was being transformed into monarchies, the Romans were expanding their control throughout the Italian Peninsula. The Romans minted their first coins during the early 3rd century BC. The earliest coins were - like other coins in the region - silver drachms with a supplementary bronze coinage. They later reverted to the silver denarius as their principal coin. The denarius remained an important Roman coin until the Roman economy began to crumble. During the 3rd century AD, the antoninianus was minted in quantity. This was originally a "silver" coin with low silver content, but developed through stages of debasement (sometimes silver washed) to pure bronze coins.

Although many regions ruled by Hellenistic monarchs were brought under Roman control, this did not immediately lead to a unitary monetary system throughout the Mediterranean region. Local coinage traditions in the eastern regions prevailed, while the denarius dominated the western regions. The local Greek coinages are known as Greek Imperial coins.

Apart from the Greeks and the Romans, other peoples in the Mediterranean region also issued coins. These include the Phoenicians, the Carthaginians, the Jews, the Celts and various regions in the Iberian Peninsula and the Arab Peninsula.

In regions to the East of the Roman Empire, that were formerly controlled by the Hellenistic Seleucids, the Parthians created an empire in Persia. The Parthians issued a relatively stable series of silver drachms and tetradrachms. After the Parthians were overthrown by the Sassanians in 226 AD, the new dynasty of Persia began the minting of their distinct thin, spread fabric silver drachms, that became a staple of their empire right up to the Arab conquest in the 7th century AD.

Evolution

Silver coins have evolved in many different forms through the ages; a rough timeline for silver coins is as follows:

* Silver coins circulated widely as money in Europe and later the Americas from before the time of Alexander the Great until the 1960s.
* 16th - 19th centuries: World silver crowns, the most famous is arguably the Mexican 8 reales (also known as Spanish dollar), minted in many different parts of the world to facilitate trade. Size is more or less standardized at around 38mm with many minor variations in weight and sizes among different issuing nations. Declining towards the end of the 19th century due to the introduction of secure printing of paper currency. It is no longer convenient to carry sacks of silver coins when they can be deposited in the bank for a certificate of deposit carrying the same value. Smaller denominations exist to complement currency usability by the public.
* 1870s - 1930s: Silver trade dollars, a world standard of its era in weight and purity following the example of the older Mexican 8 Reales to facilitate trade in the Far East. Examples: French Indochina Piastres, British Trade Dollar, US Trade Dollar, Japanese 1 Yen, Chinese 1 Dollar. Smaller denomination exists to complement currency usability by the public.
* 1930s - 1960s: Alloyed in circulating coins of many different governments of the world. This period ended when it was no longer economical for world governments to keep silver as an alloying element in their circulating coins.
* 1960's -1970's: Some circulating coins still used silver in their composition, such as 1965-70 Kennedy half dollar coins, which were debased from 90% silver to 40% silver. However, as silver's metal value continued to increase, resulting in additional hoarding by the public, these coins were eventually debased entirely to cupronickel clad coinage.
* 1960s - current: Modern crown sized commemoratives, using the weight and size of the old world crowns.
* 1980 - current: Modern silver bullion coins, mainly from 39 mm - 42 mm diameter, containing 1 troy ounce (31.103 g) of pure silver in content, regardless of purity. Smaller and bigger sizes exist mainly to complement the collectible set for numismatics market. Some are also purchased as a mean for the masses to buy a standardized store of value, which in this case is silver.

Advantages of silver coinage

Silver coins were among the first coins ever used, thousands of years ago. The silver standard was used for centuries in many places of the world. There were multiple reasons for using silver instead of other materials for coins:

* Silver has market liquidity, is easily tradable, and typically has a low spread between buy and sell prices.
* Silver is easily transportable. The elements silver and gold have a high value to weight ratio.
* Silver can be divided into small units without losing significant value; precious metals can be coined from bars, and later melted down into bars again.
* A silver coin is fungible: that is, one unit or piece of the same denomination and origin is equivalent to another.
* Most silver coin have a certain standard weight, or measure, making it easy to infer the weight of a number of coins from their number.
* A silver (alloy) coin is durable and long lasting (pure silver is relatively soft and subject to wear). A silver coin is not subject to decay.
* A silver coin has intrinsic value, although the price of silver bullion coins is subject to market swings and general inflation. Silver has always been a rare metal.
* Because silver is less valuable than gold, it is more practical for small, everyday transactions.

Cultural traditions

A silver coin or coins sometimes are placed under the mast or in the keel of a ship as a good luck charm. This tradition probably originated with the Romans. The tradition continues in modern times, for example, officers of USS New Orleans placed 33 coins heads up under her foremast and mainmast before she was launched in 1933 and USS Higgins, commissioned in 1999, had 11 coins specially selected for her mast stepping.

Jai Ganesh · 2023-05-22 13:15:14

1783) Smoke

Summary

Smoking is the act of inhaling and exhaling the fumes of burning plant material. A variety of plant materials are smoked, but the act is most commonly associated with tobacco as smoked in a cigarette, cigar, or pipe. Tobacco contains nicotine, an alkaloid that is addictive and can have both stimulating and tranquilizing psychoactive effects. The smoking of tobacco, long practiced by American Indians, was introduced to Europe by Christopher Columbus and other explorers. Smoking soon spread to other areas and today is widely practiced around the world despite medical, social, and religious arguments against it.

Details

Smoke is a suspension of airborne particulates and gases emitted when a material undergoes combustion or pyrolysis, together with the quantity of air that is entrained or otherwise mixed into the mass. It is commonly an unwanted by-product of fires (including stoves, candles, internal combustion engines, oil lamps, and fireplaces), but may also be used for pest control (fumigation), communication (smoke signals), defensive and offensive capabilities in the military (smoke screen), cooking, or smoking (tobacco, cannabis, etc.). It is used in rituals where incense, sage, or resin is burned to produce a smell for spiritual or magical purposes. It can also be a flavoring agent and preservative.

Smoke inhalation is the primary cause of death in victims of indoor fires. The smoke kills by a combination of thermal damage, poisoning and pulmonary irritation caused by carbon monoxide, hydrogen cyanide and other combustion products.

Smoke is an aerosol (or mist) of solid particles and liquid droplets that are close to the ideal range of sizes for Mie scattering of visible light.

Chemical composition

The composition of smoke depends on the nature of the burning fuel and the conditions of combustion. Fires with high availability of oxygen burn at a high temperature and with a small amount of smoke produced; the particles are mostly composed of ash, or with large temperature differences, of condensed aerosol of water. High temperature also leads to production of nitrogen oxides. Sulfur content yields sulfur dioxide, or in case of incomplete combustion, hydrogen sulfide. Carbon and hydrogen are almost completely oxidized to carbon dioxide and water. Fires burning with lack of oxygen produce a significantly wider palette of compounds, many of them toxic. Partial oxidation of carbon produces carbon monoxide, while nitrogen-containing materials can yield hydrogen cyanide, ammonia, and nitrogen oxides. Hydrogen gas can be produced instead of water. Contents of halogens such as chlorine (e.g. in polyvinyl chloride or brominated flame retardants) may lead to the production of hydrogen chloride, phosgene, dioxin, and chloromethane, bromomethane and other halocarbons. Hydrogen fluoride can be formed from fluorocarbons, whether fluoropolymers subjected to fire or halocarbon fire suppression agents. Phosphorus and antimony oxides and their reaction products can be formed from some fire retardant additives, increasing smoke toxicity and corrosivity. Pyrolysis of polychlorinated biphenyls (PCB), e.g. from burning older transformer oil, and to lower degree also of other chlorine-containing materials, can produce 2,3,7,8-tetrachlorodibenzodioxin, a potent carcinogen, and other polychlorinated dibenzodioxins. Pyrolysis of fluoropolymers, e.g. teflon, in presence of oxygen yields carbonyl fluoride (which hydrolyzes readily to HF and CO2); other compounds may be formed as well, e.g. carbon tetrafluoride, hexafluoropropylene, and highly toxic perfluoroisobutene (PFIB).

Pyrolysis of burning material, especially incomplete combustion or smoldering without adequate oxygen supply, also results in production of a large amount of hydrocarbons, both aliphatic (methane, ethane, ethylene, acetylene) and aromatic (benzene and its derivates, polycyclic aromatic hydrocarbons; e.g. benzopyrene, studied as a carcinogen, or retene), terpenes. It also results in the emission of a range of smaller oxygenated volatile organic compounds (methanol, acetic acid, hydroxy acetone, methyl acetate and ethyl formate) which are formed as combustion by products as well as less volatile oxygenated organic species such as phenolics, furans and furanones. Heterocyclic compounds may be also present. Heavier hydrocarbons may condense as tar; smoke with significant tar content is yellow to brown. Combustion of solid fuels can result in the emission of many hundreds to thousands of lower volatility organic compounds in the aerosol phase. Presence of such smoke, soot, and/or brown oily deposits during a fire indicates a possible hazardous situation, as the atmosphere may be saturated with combustible pyrolysis products with concentration above the upper flammability limit, and sudden inrush of air can cause flashover or backdraft.

Presence of sulfur can lead to formation of gases like hydrogen sulfide, carbonyl sulfide, sulfur dioxide, carbon disulfide, and thiols; especially thiols tend to get adsorbed on surfaces and produce a lingering odor even long after the fire. Partial oxidation of the released hydrocarbons yields in a wide palette of other compounds: aldehydes (e.g. formaldehyde, acrolein, and furfural), ketones, alcohols (often aromatic, e.g. phenol, guaiacol, syringol, catechol, and cresols), carboxylic acids (formic acid, acetic acid, etc.).

The visible particulate matter in such smokes is most commonly composed of carbon (soot). Other particulates may be composed of drops of condensed tar, or solid particles of ash. The presence of metals in the fuel yields particles of metal oxides. Particles of inorganic salts may also be formed, e.g. ammonium sulfate, ammonium nitrate, or sodium chloride. Inorganic salts present on the surface of the soot particles may make them hydrophilic. Many organic compounds, typically the aromatic hydrocarbons, may be also adsorbed on the surface of the solid particles. Metal oxides can be present when metal-containing fuels are burned, e.g. solid rocket fuels containing aluminium. Depleted uranium projectiles after impacting the target ignite, producing particles of uranium oxides. Magnetic particles, spherules of magnetite-like ferrous ferric oxide, are present in coal smoke; their increase in deposits after 1860 marks the beginning of the Industrial Revolution. (Magnetic iron oxide nanoparticles can be also produced in the smoke from meteorites burning in the atmosphere.) Magnetic remanence, recorded in the iron oxide particles, indicates the strength of Earth's magnetic field when they were cooled beyond their Curie temperature; this can be used to distinguish magnetic particles of terrestrial and meteoric origin. Fly ash is composed mainly of silica and calcium oxide. Cenospheres are present in smoke from liquid hydrocarbon fuels. Minute metal particles produced by abrasion can be present in engine smokes. Amorphous silica particles are present in smokes from burning silicones; small proportion of silicon nitride particles can be formed in fires with insufficient oxygen. The silica particles have about 10 nm size, clumped to 70–100 nm aggregates and further agglomerated to chains. Radioactive particles may be present due to traces of uranium, thorium, or other radionuclides in the fuel; hot particles can be present in case of fires during nuclear accidents (e.g. Chernobyl disaster) or nuclear war.

Smoke particulates, like other aerosols, are categorized into three modes based on particle size:

* nuclei mode, with geometric mean radius between 2.5 and 20 nm, likely forming by condensation of carbon moieties.
* accumulation mode, ranging between 75 and 250 nm and formed by coagulation of nuclei mode particles
* coarse mode, with particles in micrometer range

Most of the smoke material is primarily in coarse particles. Those undergo rapid dry precipitation, and the smoke damage in more distant areas outside of the room where the fire occurs is therefore primarily mediated by the smaller particles.

Aerosol of particles beyond visible size is an early indicator of materials in a preignition stage of a fire.

Burning of hydrogen-rich fuel produces water vapor; this results in smoke containing droplets of water. In absence of other color sources (nitrogen oxides, particulates...), such smoke is white and cloud-like.

Smoke emissions may contain characteristic trace elements. Vanadium is present in emissions from oil fired power plants and refineries; oil plants also emit some nickel. Coal combustion produces emissions containing aluminium, math, chromium, cobalt, copper, iron, mercury, selenium, and uranium.

Traces of vanadium in high-temperature combustion products form droplets of molten vanadates. These attack the passivation layers on metals and cause high temperature corrosion, which is a concern especially for internal combustion engines. Molten sulfate and lead particulates also have such effect.

Some components of smoke are characteristic of the combustion source. Guaiacol and its derivatives are products of pyrolysis of lignin and are characteristic of wood smoke; other markers are syringol and derivates, and other methoxy phenols. Retene, a product of pyrolysis of conifer trees, is an indicator of forest fires. Levoglucosan is a pyrolysis product of cellulose. Hardwood vs softwood smokes differ in the ratio of guaiacols/syringols. Markers for vehicle exhaust include polycyclic aromatic hydrocarbons, hopanes, steranes, and specific nitroarenes (e.g. 1-nitropyrene). The ratio of hopanes and steranes to elemental carbon can be used to distinguish between emissions of gasoline and diesel engines.

Many compounds can be associated with particulates; whether by being adsorbed on their surfaces, or by being dissolved in liquid droplets. Hydrogen chloride is well absorbed in the soot particles.

Inert particulate matter can be disturbed and entrained into the smoke. Of particular concern are particles of asbestos.

Deposited hot particles of radioactive fallout and bioaccumulated radioisotopes can be reintroduced into the atmosphere by wildfires and forest fires; this is a concern in e.g. the Zone of alienation containing contaminants from the Chernobyl disaster.

Polymers are a significant source of smoke. Aromatic side groups, e.g. in polystyrene, enhance generation of smoke. Aromatic groups integrated in the polymer backbone produce less smoke, likely due to significant charring. Aliphatic polymers tend to generate the least smoke, and are non-self-extinguishing. However presence of additives can significantly increase smoke formation. Phosphorus-based and halogen-based flame retardants decrease production of smoke. Higher degree of cross-linking between the polymer chains has such effect too.

Visible and invisible particles of combustion

The unaided eye detects particle sizes greater than 7 µm (micrometres). Visible particles emitted from a fire are referred to as smoke. Invisible particles are generally referred to as gas or fumes. This is best illustrated when toasting bread in a toaster. As the bread heats up, the products of combustion increase in size. The fumes initially produced are invisible but become visible if the toast is burnt.

An ionization chamber type smoke detector is technically a product of combustion detector, not a smoke detector. Ionization chamber type smoke detectors detect particles of combustion that are invisible to the naked eye. This explains why they may frequently false alarm from the fumes emitted from the red-hot heating elements of a toaster, before the presence of visible smoke, yet they may fail to activate in the early, low-heat smoldering stage of a fire.

Smoke from a typical house fire contains hundreds of different chemicals and fumes. As a result, the damage caused by the smoke can often exceed that caused by the actual heat of the fire. In addition to the physical damage caused by the smoke of a fire – which manifests itself in the form of stains – is the often even harder to eliminate problem of a smoky odor. Just as there are contractors that specialize in rebuilding/repairing homes that have been damaged by fire and smoke, fabric restoration companies specialize in restoring fabrics that have been damaged in a fire.

Jai Ganesh · 2023-05-23 14:44:02

1784) Coach (sport)

Gist

A person who teaches and trains an athlete or performer.

Details

An athletic coach is a person coaching in sport, involved in the direction, instruction, and training of a sports team or athlete.

History

The original sense of the word coach is that of a horse-drawn carriage, deriving ultimately from the Hungarian city of Kocs where such vehicles were first made. Students at the University of Oxford in the early nineteenth century used the slang word to refer to a private tutor who would drive a less able student through his examinations just like horse driving.

Britain took the lead in upgrading the status of sports in the 19th century. For sports to become professionalized, "coacher" had to become established. It gradually professionalized in the Victorian era and the role was well established by 1914. In the First World War, military units sought out the coaches to supervise physical conditioning and develop morale-building teams.

Effectiveness

John Wooden had a philosophy of coaching that encouraged planning, organization, and understanding, and that knowledge was important but not everything when being an effective coach. Traditionally coaching expertise or effectiveness has been measured by win–loss percentage, satisfaction of players, or years of coaching experience, but like in teacher expertise those metrics are highly ambiguous. Coaching expertise or effectiveness describes good coaching, which looks at coaching behaviour, dispositions, education, experience, and knowledge.

A widely used definition of effective coaching is "the consistent application of integrated professional, interpersonal, and intrapersonal knowledge, to improve athletes competence, confidence, connection, and character in specific coaching contexts".

Knowledge

Coaches require descriptive knowledge and procedural knowledge that relate to all aspects of coaching, with expert coaches using tacit knowledge more freely. Teachers knowledge has been categorized, like coaches knowledge with various terms being used. Many categories falling under content knowledge, pedagogical knowledge, pedagogical-content knowledge. When considering the need to build relationships with others and athletes, interpersonal knowledge has been included. Then when considering professional development requiring the skills to learn from experience while utilizing reflective practice, intrapersonal knowledge has been included.

It is rare in professional sport for a team not to hire a former professional player, but playing and coaching have different knowledge bases. The combination of professional, interpersonal, and intrapersonal knowledge can lead to good thinking habits, maturity, wisdom, and capacity to make reasonable judgements.

Professionalism

The subject, sport, curricular, and pedagogical knowledge all fall under this category of professional coaches knowledge. Including the "ologies" of sports science like; sport psychology, sport biomechanics, sport nutrition, exercise physiology, motor control, critical thinking, sociology, strength and conditioning, and sporting tactics, with all the associated sub areas of knowledge. This category of knowledge is what most coach education has been focused on but this alone is not enough to be an effective coach.

Coaching is not just about sport specific skills and education, especially when taking a holistic approach. Keeping sports people safe, and healthy while participating are responsibilities of a coach as well as awareness of social factors like the relative age effect.

Interpersonality

Much of coaching involves interacting with players, staff, community, opposition, and then family members in youth sport. The relationships built in a sports team influence the social interactions which can affect player performance and development, fan culture, and in professional sport, financial backing. Effective coaches have knowledge that helps in all social contexts to make the best of each situation, with the coach–athlete relationship. being one of the most crucial to get right.

Excellent communication skills are imperative for coaches in order to provide their athletes with the adequate skills, knowledge and mental as well as tactical ability.

Intrapersonality

A coaches ability to improve relies on professional development in continued learning which uses a combination of evaluation and reflective practice. Their recognition of personal ethical views and disposition are also elements of intrapersonal knowledge. The understanding of oneself and ability to use introspection and reflection are skills that take time to develop, using deliberate practice in each changing context. Coaching expertise requires this knowledge much like teachers as each experience can confirm or contradict a prior belief in player performance. The internal and external framing of a coaches role can impact their reflection, suggesting perspective can be a limitation promoting the idea of a coaching community for feedback.

Athlete outcomes

The coaching behavior assessment system has been used to show that coaching knowledge and behavior have significant influence on participants psychological profile affecting self-esteem, motivation, satisfaction, attitudes, perceived competence, and performance. For a coach to be seen as effective, the people they work with should be improving, with expert coaches being able to sustain that over an extended period of time. There are various areas of development that can be categorized, which was first done with a 5 C's model: competence, confidence, connection, character and compassion and was then later shortened to a 4 C's model by combining character and compassion.

People's competence can relate to their sport-specific technical and tactical skills, performance skills, improved health and fitness, and overall training habits. Their confidence relating to an internal sense of overall positive self-worth. Having a good connections is the positive bonds and social relationships with people inside and outside of the sporting context. Then character is respect for the sport and other participating showing good levels of morality, integrity, empathy, and responsibility.

The competence of a person is linked to leadership and centered around becoming a self-reliant member of a sports team and society in the coaching context. Competencies have guided much of sport psychology supporting positive youth development.

The self-determination theory suggests an environment that supports autonomous decision making, can help develop competence, confidence, and connection to others affecting motivation. Effective coaches therefore create supportive environments while building good relationships with the people they coach.

Support staff

In professional sports, a coach is usually supported by one or more assistant coaches and a specialist team including sports scientists. The staff may include coordinators, a strength and conditioning coach, sport psychologist, physiotherapist, nutritionist, biomechanist, or sports analyst.

Context

The sport, environment, and context of coaching changes just like teaching. It is critical to understand the differences in sport [56] with recreational, developmental, and elite have been 3 suggested categories. This has been reduced to participation and performance by some. These different coaching context alter the trajectories of long term athlete development, affecting the prescription of training patterns and management of social influences

When integrating the suggested participation and performance contexts with age, 4 categories have been suggested to represent the various coaching contexts. The sampling years which are participation coaches for children. The recreational years which are participation coaches for adolescents and adults. The specializing years which are performance coaches for young adolescents. Then the investment years which are the coaches for older adolescents and adults.

Jai Ganesh · 2023-05-24 13:43:17

1785) Teacher

Gist

A person whose job is to teach, especially in a school or college.

Summary

Teaching is the profession of those who give instruction, especially in an elementary school or a secondary school or in a university.

Measured in terms of its members, teaching is the world’s largest profession. In the 21st century it was estimated that there were about 80 million teachers throughout the world. Though their roles and functions vary from country to country, the variations among teachers are generally greater within a country than they are between countries. Because the nature of the activities that constitute teaching depends more on the age of the persons being taught than on any other one thing, it is useful to recognize three subgroups of teachers: primary-school, or elementary-school, teachers; secondary-school teachers; and university teachers. Elementary-school teachers are by far the most numerous worldwide, making up nearly half of all teachers in some developed countries and three-fourths or more in developing countries. Teachers at the university level are the smallest group.

The entire teaching corps, wherever its members may be located, shares most of the criteria of a profession, namely (1) a process of formal training, (2) a body of specialized knowledge, (3) a procedure for certifying, or validating, membership in the profession, and (4) a set of standards of performance—intellectual, practical, and ethical—that is defined and enforced by members of the profession. Teaching young children and even adolescents could hardly have been called a profession anywhere in the world before the 20th century. It was instead an art or a craft in which the relatively young and untrained women and men who held most of the teaching positions “kept school” or “heard lessons” because they had been better-than-average pupils themselves. They had learned the art solely by observing and imitating their own teachers. Only university professors and possibly a few teachers of elite secondary schools would have merited being called members of a profession in the sense that medical doctors, lawyers, or priests were professionals; in some countries even today primary-school teachers may accurately be described as semiprofessionals. The dividing line is imprecise. It is useful, therefore, to consider the following questions: (1) What is the status of the profession? (2) What kinds of work are done? (3) How is the profession organized?

Details

A teacher, also called a schoolteacher or formally an educator, is a person who helps students to acquire knowledge, competence, or virtue, via the practice of teaching.

Informally the role of teacher may be taken on by anyone (e.g. when showing a colleague how to perform a specific task). In some countries, teaching young people of school age may be carried out in an informal setting, such as within the family (homeschooling), rather than in a formal setting such as a school or college. Some other professions may involve a significant amount of teaching (e.g. youth worker, pastor).

In most countries, formal teaching of students is usually carried out by paid professional teachers. This article focuses on those who are employed, as their main role, to teach others in a formal education context, such as at a school or other place of initial formal education or training.

Duties and functions

A teacher's role may vary among cultures.

Teachers may provide instruction in literacy and numeracy, craftsmanship or vocational training, the arts, religion, civics, community roles, or life skills.

Formal teaching tasks include preparing lessons according to agreed curricula, giving lessons, and assessing pupil progress.

A teacher's professional duties may extend beyond formal teaching. Outside of the classroom teachers may accompany students on field trips, supervise study halls, help with the organization of school functions, and serve as supervisors for extracurricular activities. They also have the legal duty to protect students from harm, such as that which may result from bullying, sexual harassment, racism or abuse. In some education systems, teachers may be responsible for student discipline.

Competences and qualities required by teachers

Teaching is a highly complex activity. This is partially because teaching is a social practice, that takes place in a specific context (time, place, culture, socio-political-economic situation etc.) and therefore is shaped by the values of that specific context. Factors that influence what is expected (or required) of teachers include history and tradition, social views about the purpose of education, accepted theories about learning, etc.

Competences

The competences required by a teacher are affected by the different ways in which the role is understood around the world. Broadly, there seem to be four models:

* the teacher as manager of instruction;
* the teacher as caring person;
* the teacher as expert learner; and
* the teacher as cultural and civic person.

The Organisation for Economic Co-operation and Development has argued that it is necessary to develop a shared definition of the skills and knowledge required by teachers, in order to guide teachers' career-long education and professional development. Some evidence-based international discussions have tried to reach such a common understanding. For example, the European Union has identified three broad areas of competences that teachers require:

* Working with others
* Working with knowledge, technology and information, and
* Working in and with society.

Scholarly consensus is emerging that what is required of teachers can be grouped under three headings:

* knowledge (such as: the subject matter itself and knowledge about how to teach it, curricular knowledge, knowledge about the educational sciences, psychology, assessment etc.)
* craft skills (such as lesson planning, using teaching technologies, managing students and groups, monitoring and assessing learning etc.) and
* dispositions (such as essential values and attitudes, beliefs and commitment).

Qualities:

Enthusiasm

It has been found that teachers who showed enthusiasm towards the course materials and students can create a positive learning experience. These teachers do not teach by rote but attempt to invigorate their teaching of the course materials every day. Teachers who cover the same curriculum repeatedly may find it challenging to maintain their enthusiasm, lest their boredom with the content bore their students in turn. Enthusiastic teachers are rated higher by their students than teachers who didn't show much enthusiasm for the course materials.

Teachers that exhibit enthusiasm are more likely to have engaged, interested and energetic students who are curious about learning the subject matter. Recent research has found a correlation between teacher enthusiasm and students' intrinsic motivation to learn and vitality in the classroom. Controlled, experimental studies exploring intrinsic motivation of college students has shown that nonverbal expressions of enthusiasm, such as demonstrative gesturing, dramatic movements which are varied, and emotional facial expressions, result in college students reporting higher levels of intrinsic motivation to learn. But even while a teacher's enthusiasm has been shown to improve motivation and increase task engagement, it does not necessarily improve learning outcomes or memory for the material.

There are various mechanisms by which teacher enthusiasm may facilitate higher levels of intrinsic motivation. Teacher enthusiasm may contribute to a classroom atmosphere of energy and enthusiasm which feeds student interest and excitement in learning the subject matter. Enthusiastic teachers may also lead to students becoming more self-determined in their own learning process. The concept of mere exposure indicates that the teacher's enthusiasm may contribute to the student's expectations about intrinsic motivation in the context of learning. Also, enthusiasm may act as a "motivational embellishment", increasing a student's interest by the variety, novelty, and surprise of the enthusiastic teacher's presentation of the material. Finally, the concept of emotional contagion may also apply: students may become more intrinsically motivated by catching onto the enthusiasm and energy of the teacher.

Interaction with learners

Research shows that student motivation and attitudes towards school are closely linked to student-teacher relationships. Enthusiastic teachers are particularly good at creating beneficial relations with their students. Their ability to create effective learning environments that foster student achievement depends on the kind of relationship they build with their students. Useful teacher-to-student interactions are crucial in linking academic success with personal achievement. Here, personal success is a student's internal goal of improving themselves, whereas academic success includes the goals they receive from their superior. A teacher must guide their student in aligning their personal goals with their academic goals. Students who receive this positive influence show stronger self-confidence and greater personal and academic success than those without these teacher interactions.

Students are likely to build stronger relations with teachers who are friendly and supportive and will show more interest in courses taught by these teachers. Teachers that spend more time interacting and working directly with students are perceived as supportive and effective teachers. Effective teachers have been shown to invite student participation and decision making, allow humor into their classroom, and demonstrate a willingness to play.

Teaching qualifications

In many countries, a person who wishes to become a teacher must first obtain specified professional qualifications or credentials from a university or college. These professional qualifications may include the study of pedagogy, the science of teaching. Teachers, like other professionals, may have to, or choose to, continue their education after they qualify, a process known as continuing professional development.

The issue of teacher qualifications is linked to the status of the profession. In some societies, teachers enjoy a status on a par with physicians, lawyers, engineers, and accountants, in others, the status of the profession is low. In the twentieth century, many intelligent women were unable to get jobs in corporations or governments so many chose teaching as a default profession. As women become more welcomed into corporations and governments today, it may be more difficult to attract qualified teachers in the future.

Teachers are often required to undergo a course of initial education at a College of Education to ensure that they possess the necessary knowledge, competences and adhere to relevant codes of ethics.

There are a variety of bodies designed to instill, preserve and update the knowledge and professional standing of teachers. Around the world many teachers' colleges exist; they may be controlled by government or by the teaching profession itself.

They are generally established to serve and protect the public interest through certifying, governing, quality controlling, and enforcing standards of practice for the teaching profession.

Professional standards

The functions of the teachers' colleges may include setting out clear standards of practice, providing for the ongoing education of teachers, investigating complaints involving members, conducting hearings into allegations of professional misconduct and taking appropriate disciplinary action and accrediting teacher education programs. In many situations teachers in publicly funded schools must be members in good standing with the college, and private schools may also require their teachers to be college members. In other areas these roles may belong to the State Board of Education, the Superintendent of Public Instruction, the State Education Agency or other governmental bodies. In still other areas Teaching Unions may be responsible for some or all of these duties.

Professional misconduct

Misconduct by teachers, especially sexual misconduct, has been getting increased scrutiny from the media and the courts. A study by the American Association of University Women reported that 9.6% of students in the United States claim to have received unwanted sexual attention from an adult associated with education; be they a volunteer, bus driver, teacher, administrator or other adult; sometime during their educational career.

A study in England showed a 0.3% prevalence of sexual abuse by any professional, a group that included priests, religious leaders, and case workers as well as teachers. It is important to note, however, that this British study is the only one of its kind and consisted of "a random ... probability sample of 2,869 young people between the ages of 18 and 24 in a computer-assisted study" and that the questions referred to "sexual abuse with a professional," not necessarily a teacher. It is therefore logical to conclude that information on the percentage of abuses by teachers in the United Kingdom is not explicitly available and therefore not necessarily reliable. The AAUW study, however, posed questions about fourteen types of sexual harassment and various degrees of frequency and included only abuses by teachers. "The sample was drawn from a list of 80,000 schools to create a stratified two-stage sample design of 2,065 8th to 11th grade students". Its reliability was gauged at 95% with a 4% margin of error.

In the United States especially, several high-profile cases such as Debra LaFave, Pamela Rogers Turner, and Mary Kay Letourneau have caused increased scrutiny on teacher misconduct.

Chris Keates, the general secretary of National Association of Schoolmasters Union of Women Teachers, said that teachers who have gender with pupils over the age of consent should not be placed on the gender offenders register and that prosecution for statutory math "is a real anomaly in the law that we are concerned about." This has led to outrage from child protection and parental rights groups. Fears of being labelled a pedophile or hebephile has led to several men who enjoy teaching avoiding the profession. This has in some jurisdictions reportedly led to a shortage of male teachers.

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Jai Ganesh · 2023-05-25 13:09:42

1786) Heaven

Gist

The abode of God, the angels, and the spirits of the righteous after death; the place or state of existence of the blessed after the mortal life.

Summary

Heaven, or the heavens, is a common religious cosmological or transcendent supernatural place where beings such as deities, angels, souls, saints, or venerated ancestors are said to originate, be enthroned, or reside. According to the beliefs of some religions, heavenly beings can descend to Earth or incarnate and earthly beings can ascend to Heaven in the afterlife or, in exceptional cases, enter Heaven without dying.

Heaven is often described as a "highest place", the holiest place, a Paradise, in contrast to hell or the Underworld or the "low places" and universally or conditionally accessible by earthly beings according to various standards of divinity, goodness, piety, faith, or other virtues or right beliefs or simply divine will. Some believe in the possibility of a heaven on Earth in a world to come.

Another belief is in an axis mundi or world tree which connects the heavens, the terrestrial world, and the underworld. In Indian religions, heaven is considered as Svarga loka, and the soul is again subjected to rebirth in different living forms according to its karma. This cycle can be broken after a soul achieves Moksha or Nirvana. Any place of existence, either of humans, souls or deities, outside the tangible world (Heaven, Hell, or other) is referred to as the otherworld.

At least in the Abrahamic faiths of Christianity, Islam, and some schools of Judaism, as well as Zoroastrianism, heaven is the realm of Afterlife where good actions in the previous life are rewarded for eternity (hell being the place where bad behavior is punished).

Details

Heaven, in many religions, is the abode of God or the gods, as well as of angels, deified humans, the blessed dead, and other celestial beings. It is often conceived as an expanse that overarches the earth, stretching overhead like a canopy, dome, or vault and encompassing the sky and upper atmosphere; the Sun, Moon, and stars; and the transcendent realm beyond.

Overview

In most cultures, heaven is synonymous with order: it contains the blueprints for creation, the mandate by which earthly rulers govern, and the standards by which to measure beauty, goodness, and truth. In religious thought and poetic fancy, heaven is not only a place but also a state of being. As such it is characterized negatively as freedom from hunger, thirst, pain, deprivation, disease, ignorance, and strife and positively as complete contentment, perfect knowledge, everlasting rest, ineffable peace, communion with God, and rapturous joy. Heaven is also understood as the reward for a life well lived, the fulfillment of the heart’s deepest desire, and the ultimate reference point for all human striving and hope.

In ancient cosmologies, heaven is situated in the extreme west or east, on a faraway island or mountaintop, or in astral realms. Plurality and even redundancy is the rule, as multiple heavens overlap with earthly paradises and astronomical spheres. Many myths of the origin of heaven recount that in the beginning heaven and earth were closely wedded; the present condition of estrangement, marked by the withdrawal of the gods and by suffering, sin, and death, is the result of a catastrophic event for which human ancestors or rival heavenly powers are to blame. A desire to recapture lost intimacy with heaven suffuses the literature of the world’s religions, but there is enormous variety in how different traditions conceive of the longed-for realization of human hopes.

World mythology abounds in stories of attempts to invade heaven, such as the flight of Icarus, the Hindu legend of the conquest of heaven by the asura (demon) king Bali, and countless variations on the story of Babel, a man-made tower reaching to heaven (Genesis 11:1–9). Such attempts almost always come to a bad end. Shamans, prophets, kings, and visionaries may visit heaven by way of a dream, trance, or extraordinary summons, but the usual route is by death. Most cultures see the road to heaven as fraught with dangers and trials, such as bridges that narrow to a razor’s edge, rivers filled with waters of death, and hostile powers who seek to block the soul’s ascent. All such ordeals are open to moral and psychological interpretation. In world literature the drama of the perilous journey to heaven has appeared in many forms, including epic, allegory, satire, science fiction, and fantasy. Notable examples are Dante’s masterpiece, The Divine Comedy (early 14th century), the 16th-century Chinese comic novel Xiyouji (“The Journey to the West”), John Bunyan’s The Pilgrim’s Progress (1678), Mark Twain’s Extract from Captain Stormfield’s Visit to Heaven (1909), and C.S. Lewis’s Perelandra (1943).

Earning a place in heaven usually requires meritorious activity, such as almsgiving, caring for the sick, performing sacrifices or other sacramental rites pleasing to the heavenly powers, exhibiting heroic virtue as a warrior, ascetic, or martyr, or enduring great suffering. Some traditions believe that merit can be transferred by means of pious actions performed on behalf of the dead. Yet many take the view that heaven is attainable only as the free gift of a divine being. Adherents of Pure Land Buddhism, for example, rely upon the vow of Amitabha Buddha to bring to Sukhavati (the Pure Land, or Western Paradise) all who sincerely call upon his name; the Lutheran trusts in justification by faith alone; and popular piety in general looks to the protection of powerful heavenly patrons.

Descriptions of heaven vie for superlatives, for here everything must be the best imaginable: from the delectable boar that feeds the crowds of Valhalla (the heavenly abode in Norse mythology), boiled every day and coming alive again every evening, to the perfumed paradise extolled by the Buddhist Sukhavati-vyuha sutras, which coruscates with precious stones, peacocks, parasols, and lotus blossoms, never knowing extremes of climate nor discord of any kind. Heaven may be characterized as a garden (nature perfected) or a city (society perfected) or both at once; it may be a realm of mystical tranquility or of heightened activity. In broad strokes the imagery is universal, with light being the privileged symbol; yet the details are often culture-specific, with the occupations most valued by a given society receiving pride of place, as in the hunters’ paradises of Australian Aboriginal mythology, the Platonic heaven for contemplatives, the bureaucratic heavens of imperial China, and the rabbinic Heavenly Academy.

Heaven in world religions and history:

Ancient Mesopotamia

Creation myths of ancient Mesopotamia typically begin with the separation of heaven and earth, giving rise to a three-story universe that includes heaven above, earth in the middle, and the underworld below. The high gods reign in the heavens as an assembly or council. Earth is the realm of mortal humans, whose purpose is to serve the gods by providing them with sacred dwellings, food, and tribute; it is also populated by minor gods and demons who play a role in magic. At death human beings descend to the underworld, a dreary land of no return; only a few exceptional human heroes are permitted to enter heaven.

In the epic of Gilgamesh, a cycle of Sumerian and Akkadian legends about the king of the Mesopotamian city-state Uruk, Gilgamesh searches unsuccessfully for immortality only to have the sober truth of human mortality brought home: “When the gods created mankind, death for mankind they allotted, life in their own hands retaining.” Good relations with heaven were nonetheless considered vital to the well-being of the living. The Gilgamesh epic suggests that the social order of Uruk was threatened not only by Gilgamesh’s unrealistic ambition to conquer death but also by his unwillingness to enter into sacred marriage with the goddess Ishtar (Sumerian: Inanna), whose temple was the centre of civic and cultic life. Concern for good relations with heaven is reflected as well in the massive body of Mesopotamian texts devoted to celestial observation, astronomical theory, and astrological lore, all of which served to discern and cope with the perceived influence of heaven on human affairs.

Egypt

An even greater emphasis on the ruler’s role as guarantor of right relations with heaven characterized ancient Egyptian civilization throughout its 3,000-year history. The king shared with the sun god Re and the sky god Horus responsibility for defending order against chaos, and he was granted the privilege of enjoying renewable life as part of the great cosmic circuit. That this renewable life depended on massive cultic support is evident from monumental tombs, grave goods, and elaborate mortuary rituals.

Heaven was visualized mythically as the divine cow on whose back the sun god withdrew from earth; as the falcon-headed god Horus whose glittering eyes formed the Sun and Moon; or as the goddess Nut arching over the earth. A happy afterlife, however, could take place in any number of locations: in the fertile Field of Reeds, as a passenger in the solar bark, in the extreme west or east, or among the circumpolar stars. The Pyramid Texts envision a happy afterlife for royalty alone; the dead king is identified with Osiris as well as with the triumphant rising sun. The Coffin Texts and the Book of the Dead, in which the afterlife is to some degree “democratized,” identify all the deceased with Osiris in his capacity as judge and ruler of the underworld.

Judaism

True to its Middle Eastern origins, ancient Judaism at first insisted on the separateness of heaven and earth and had little to say about the prospect of a heavenly afterlife: “The heavens are the LORD’s heavens, but the earth he has given to human beings” (Psalm 115:16). Heaven (in Hebrew, the plural šāmayim) was a vast realm above the earth, supported by a hard firmament of dazzling precious stone, which kept the upper waters from mingling with the waters beneath. The Sun, Moon, and stars were set in the firmament, and windows could open to let down rain, snow, hail, or dew from the celestial storehouses. God, the maker of heaven and earth, was enthroned in the highest reach of heaven; from there he intervened in the affairs of his creatures and revealed through Moses and the prophets his sovereignty, providential care, and cultic and moral demands. Surrounding the divine throne was a heavenly host of solar, astral, and angelic beings. These celestial beings shared many attributes with the gods and goddesses of Canaanite and Mesopotamian polytheism, but the emerging monotheism of the Hebrew Scriptures demanded exclusive commitment to one God, referred to as The Lord, to whom all powers in heaven and on earth were subject.

In ancient Judaism, as in other Middle Eastern religions of the period, the cosmos had a three-story structure. God dwelt in heaven and was also present in the Temple of Jerusalem, his palace on earth. The underworld (Hebrew: She’ōl), to which human beings were consigned at death, was seemingly outside God’s jurisdiction. This picture changed dramatically, however, in response to the Babylonian Exile and the destruction of the First Temple in 586 BCE, as the conviction began to take hold that there must be no limit to God’s power to vindicate his people even after death. During the postexilic period, the experience of foreign rule intensified longing for future deliverance, encouraged speculation influenced by Persian and Greco-Roman models of cosmology, angelology, and immortality, and produced martyrs whose claim on a heavenly afterlife seemed particularly strong. Thus the Book of Daniel, considered the latest composition in the Hebrew Bible, contains this prophecy:

Many of those who sleep in the dust of the earth shall awake, some to everlasting life, and some to shame and everlasting contempt. Those who are wise shall shine like the brightness of the sky, and those who lead many to righteousness, like the stars for ever and ever. (12:2–3)

While belief in a heavenly afterlife became widespread in the Hellenistic Age (323–30 BCE), no single model predominated, but rather a profusion of images and schemes, including resurrection of the dead, immortality of the soul, and transformation into an angel or star. Visionary journeys through the heavens (conceived as a hierarchy of spheres) became a staple of apocalyptic literature, and Jewish mystics produced a vast theosophical lore concerning heavenly palaces, angelic powers, and the dimensions of God’s body. Traces of this heaven mysticism can still be found in the Jewish prayer book (siddur).

Classical Rabbinic Judaism, which emerged after the destruction of the Second Temple (70 CE) and established the main lines on which Jewish eschatology would develop, admitted a plurality of images for heaven; the expression ʿolam ha-ba (“the world to come”) refers both to the messianic age and to the heavenly estate to which the righteous ascend at death. After death, righteous souls await the resurrection in the heavenly Garden of Eden or hidden under the divine throne. Jewish liturgy piles praise upon praise in exaltation of the name and kingship of God, who “rides the highest heavens,” blesses his people eternally, judges, redeems, and “maintains His faith to those asleep in the dust.” The Sabbath is understood to be a preview of heaven, anticipating the wedding feast at the end of time, when the work of creation will be complete and the captivity of Zion will end.

Christianity

Christianity began as one of many Jewish apocalyptic and reform movements active in Palestine in the 1st century CE. These groups shared an intense conviction that the new heavens and new earth prophesied by Isaiah (Isaiah 65:17) were close at hand. They believed that history would soon find its consummation in a world perfected, when the nations would be judged, the elect redeemed, and Israel restored.

Jewish and Christian conceptions of heaven developed side by side, drawing from shared biblical and Greco-Roman sources. The liturgy of Temple, synagogue, and eucharistic service informed images of heaven, for in worship the community symbolically ascends to the heavenly Jerusalem, a realm of perpetual adoration and intercession for the needs of the world, where angels never cease to sing “Holy, holy, holy is the LORD of hosts” (Isaiah 6:3).

Christians believe that the estrangement between heaven and earth ended with the Incarnation, Passion, Resurrection, and Ascension of Christ: “in Christ God was reconciling the world to himself” (2 Corinthians 5:19). Sharing in Christ’s deathless divine life are the members of his mystical body, the church (Greek: ekklēsia), which is the communion of saints both living and dead. The Virgin Mary, regarded as Queen of Heaven, tirelessly intercedes for the faithful, including sinners who seek her protection.

Traditional Christian theology teaches that communion with God is the chief end for which human beings were made and that those who die in a state of grace are immediately (or after a period of purification) admitted to the bliss of heaven, where they become like God (1 John 3:2), see God face to face (1 Corinthians 13:12), and see all things in God. With the resurrection of the dead, beatitude will embrace the whole person—body, soul, and spirit. The social dimension of this beatitude is expressed in the last book of the New Testament, Revelation to John, with its vision of the blessed multitudes adoring God, who dwells in their midst, in a city of bejeweled splendour (21–22). Worship, fellowship, and creative pursuits all form part of the composite Christian picture of heaven, but the emphasis on domestic happiness and never-ending spiritual progress in heaven is largely a modern innovation.

Islam

The Qurʾān, which according to Islamic tradition has its original in heaven, frequently calls attention to the heavens as a sign of God’s sovereignty, justice, and mercy. When the earth was just formed and the sky a mere vapour, God commanded them to join together, and they willingly submitted (sura 41:11–12). God then completed his creation by forming the sky into seven firmaments, adorning the lower firmament with lights, and assigning to everything its just measure. The seven heavens and the earth perpetually celebrate God’s praise (sura 17:44) and by their majestic design provide evidence that God indeed has the power to raise the dead and to judge them on the last day.

Before the resurrection, the souls of the dead are thought to dwell in an intermediate state, experiencing a preview of their future condition of misery or bliss. On the Day of Judgment, heaven will be split asunder, the mountains will crumble to dust, the earth will give up its dead, and each person will undergo a final test. The righteous, with faces beaming, will pass the test easily, passing through hell with ease. In gardens of bliss they will recline on royal couches, clothed in fine silk and shaded by fruit trees of every description. Immortal youths will serve them cool drinks and delicacies, and ever-virgin companions with lustrous eyes will join them. They will also be reunited with their faithful offspring, and peace will reign.

Being in God’s presence is the chief delight of paradise, according to Muslim philosophers and mystics, and the greater one’s degree of blessedness, the closer one will be to God. Accounts of the Prophet Muhammad’s ascent through the seven heavens to the very throne of God are taken as revealing his uniquely favoured status. Although Sufis (Islamic mystics) speak of an ecstatic “annihilation” (fanāʾ) in the presence of God, the emphasis within mainstream Islamic traditions on God’s transcendence has discouraged the development of eschatology focusing on divinization or beatific union with God.

Hinduism

In Hinduism (a comparatively modern term that covers manifold religious practices and worldviews of the peoples of South Asia), heaven is the perennial object of myth, ritual practice, and philosophical speculation. The most ancient religious texts, the Vedas (1500–1200 BCE), depict heaven as the domain of sky gods such as Indra, the thunder god; Surya, the Sun; Agni, the sacrificial fire; Soma, the heavenly elixir (embodied on earth as an intoxicating plant); Varuna, the overseer of cosmic order; and Yama, the first human to die. Ritual sacrifice was deemed essential for world maintenance, and funeral rites ensured that the spirit of the deceased would ascend to the “world of the fathers” on high. Rebirth in heaven depended upon having male householder descendants to sponsor the necessary rites.

During the period of the early Upanishads (800–500 BCE), a group of itinerant sages turned from the sacrificial ritualism of Vedic tradition to develop the rudiments of classical Hindu soteriology (the theological doctrine of salvation). These sages taught that the entire phenomenal world is caught up in an endless cycle of birth and death (samsara) propelled by desire. A person’s station in life is determined by actions performed in previous lives (karma). To be reborn in heaven (svarga) is pleasant but impermanent; even the gods must eventually die. The ultimate goal is to escape this perishing life and attain union with the infinite spirit (brahman).

The Upanishadic path of liberation required practicing spiritual disciplines beyond the capacity of ordinary householders. But by the beginning of the 2nd millennium, the mystical asceticism of the Upanishads had been absorbed into the great stream of devotional Hinduism. The result was the appearance of new forms of religious literature, such as the Bhagavadgita and the Puranas, in which salvation takes the form of personal union with the divine, thus opening a broad way to heaven (or, rather, to the heaven beyond all heavens) to those who entrust themselves to the protection of a deity.

Buddhism

Buddhism began in the early 5th century BCE in northeast India as a renunciant movement seeking liberation from samsara through knowledge and spiritual discipline. The Buddha Gotama, the founder of the religion, is the paradigm of an enlightened being who has entered parinibbana (complete nibbana [Sanskrit nirvana]), the state in which the causes of all future existence have been eliminated. Classical Buddhist cosmology describes six realms of rebirth within an incalculably vast system of worlds and eons. One may be reborn as an animal, a human, a hungry ghost, a demigod, a denizen of one of the horrific hell realms, or a god in one of the pleasurable heaven realms. All of these births partake of the impermanence that characterizes samsara. Thus, heaven, in the sense of a celestial realm, is not the goal of spiritual practice. Yet Buddhist tradition speaks of celestial beings of limitless wisdom and compassion, such as Amitabha Buddha and the bodhisattva Avalokiteshvara, who have dedicated their abundant merit to the cultivation of heavenlike Pure Lands for the salvation of sentient beings. Devotees reborn in these paradisiacal realms find there the ideal conditions for attaining enlightenment.

Other heavens

Most, if not all, cultures possess multiple images of heaven and paradise, which coexist in unsystematic profusion. Mount Olympus, the Elysian Fields, and the Isles of the Blessed in Greek and Roman mythology constitute just one example. In Chinese civilizations, conformity to the “way of heaven” (tiandao) is a perennial ideal that appears in a variety of traditions. It is evident in ancient practices of sacrifice and divination, in Confucian teachings on discerning the will of heaven (tianming; literally “heaven’s mandate”) within the nexus of social relations, in Daoist teachings on harmonizing with the way of heaven as manifest in nature, in popular Daoist legends of the Ba Xian (“Eight Immortals”), who travel to heaven by means of alchemy and yoga, and also in innumerable Chinese Buddhist and sectarian movements dedicated to the cult of heaven.

In some traditions, heaven seems to recede into the background. Native American cultures, for example, are oriented toward the totality of earth, sky, and the four directions rather than toward heaven alone. Although heaven is not typically the abode of the blessed dead in Native American mythology, the stars, Sun, Moon, clouds, mountaintops, and sky-dwelling creators figure significantly. The Christian-influenced prophetic visions characteristic of revitalization movements such as the 19th-century Ghost Dance and the religion of Handsome Lake are fervently millenarian, proclaiming the advent of an eschatological paradise to be accompanied by the return of the dead and the restoration of tribal life.

New models of heaven in the modern West have been influenced by ideals of progress, evolution, social equality, and domestic tranquility. The 19th-century Spiritualist movement, adapting the doctrines of the Swedish scientist and theologian Emanuel Swedenborg and of the German physician Franz Anton Mesmer, mixed clairvoyance with science to describe heavenly spheres, radiant with luminiferous ether, where the spirits worked for causes such as abolition, temperance, feminism, and socialism and pursued opportunities for self-improvement. Utopian communities sought to bring this progressive heaven to practical realization on earth. Consolation literature, epitomized in the United States by Elizabeth Stuart Phelps’s novel The Gates Ajar (1868), portrayed heaven as an intimate realm of family reunions.

Belief in heaven persists despite age-old criticisms: that it is an irrational, wish-fulfilling fantasy, a symptom of alienation, and an evasion of responsibility for bettering the real world. Defenders of the doctrine insist, on the contrary, that belief in heaven has a morally invigorating effect, endowing life with meaning and direction and inspiring deeds of heroic self-sacrifice. Whatever be the case, familiarity with the iconography of heaven is indispensable to understanding Western literature and art, including the poetry of Dante, Edmund Spenser, William Shakespeare, John Milton, John Donne, George Herbert, Henry Vaughan, Thomas Traherne, John Bunyan, and William Blake, as well as the paintings of Fra Angelico, Luca Signorelli, Sandro Botticelli, Correggio, Jan van Eyck, and Stefan Lochner. Much the same can be said for other cultures: in every historical period, depictions of heaven provide a revealing index of what a society regards as the highest good. Hence the study of heaven is, in its broadest application, the study of ultimate human ideals.

Jai Ganesh · 2023-05-26 00:37:14

1787) Walking

Gist

Walking isn’t always the quickest way to make it from point A to point B. But it’s not just about quick transport: The benefits of walking for your body and mind are numerous.

Summary

The Physical Activity Guidelines for Americans recommend that adults get at least 150 minutes of moderate-intensity aerobic physical activity or 75 minutes of vigorous-intensity physical activity, or an equivalent combination each week. The guidelines also recommend that children and adolescents be active for at least 60 minutes every day. Following these guidelines can contribute to overall health, and decrease the risk of chronic diseases such as heart disease, cancer or diabetes.

Walking is a great way to get the physical activity needed to obtain health benefits. Walking does not require any special skills. It also does not require a gym membership or expensive equipment. A single bout of moderate-to-vigorous physical activity can improve sleep, memory, and the ability to think and learn. It also reduces anxiety symptoms.

Details

Walking is an activity that ranges from a competitive sport, usually known as race walking, to a primary and popular form of outdoor recreation and mild aerobic exercise.

Racewalking

The technique followed in the track-and-field sport of racewalking requires that a competitor’s advancing foot touch the ground before the rear foot leaves the ground, and for this reason the sport is sometimes known as heel-and-toe racing. In all countries in the world—with the exception of England—and in the Olympic Games the advancing leg must also be straightened briefly while that foot is in contact with the ground.

Walking as a competitive sport dates from the latter half of the 19th century, although stories of individual walking feats were recorded much earlier. A 7-mile (11-km) walking event was introduced by the Amateur Athletic Club of England at its championships in 1866. During the 1870s and ’80s, professional races were held indoors in New York City in which athletes competed around the clock but were permitted to eat, rest, or nap. The winner was the contestant who covered the greatest distance in six days.

Walking races of 10 miles and 3,500 metres were added to the men’s Olympic program in 1908. Since 1956, however, the Olympic distances have been 20 and 50 km. A women’s 10-km walk was introduced at the 1992 Games; at the 2000 Games the women’s walking event was extended to 20 km.

Recreational and fitness walking

Organized noncompetitive walking is extremely popular in the United States and Europe. Millions participate for the relaxation and exercise it offers. Walking for recreation or fitness is differentiated from hiking by its shorter distances, less challenging settings, and the lack of need for specialized equipment. Walking can simply be an unorganized meander around a local park or trail for relaxation or a daily regimen of several miles that is undertaken for health benefits.

The shoes needed for comfortable recreational walking vary by conditions and the type of walk undertaken. While distance walkers often use conventional hiking boots, particularly in colder weather, shorter-distance recreational walking can comfortably be done in lighter shoes similar to those worn by runners.

Walking is the preferred exercise of a significant segment of the population of North America and Europe. Its health benefits are well documented, ranging from better overall cardiovascular health to the promotion of healthy weight loss, stress relief, and a reduction in the risk of some forms of cancer by up to 40 percent. One major attraction of fitness walking is its less strenuous nature, which reduces the likelihood of the types of injuries more commonly seen in such high-impact sports as running. Fitness walking is an ideal form of exercise for senior citizens and others who need to exercise but prefer a more gentle means of doing so.

Recreational walkers often utilize short sections of trails designed for long-distance hikers. However, not all walking trips are short. Some organized walks last for days and cover distances in excess of 50 miles. Through the efforts of organized walking associations, recreational walkers have established a sizeable trail network of their own in cities and rural areas. In the United States, the American Volkssport Federation is an umbrella organization made up of more than 500 local walking clubs nationwide that promote recreational walking and organize group walks or rambles. In Canada, the Canadian Volkssport Federation is home to another 100 local walking clubs that promote recreational walking in their areas. In Great Britain, the British Walking Federation oversees approximately 40 walking clubs nationwide.

Additional Information

Walking (also known as ambulation) is one of the main gaits of terrestrial locomotion among legged animals. Walking is typically slower than running and other gaits. Walking is defined by an 'inverted pendulum' gait in which the body vaults over the stiff limb or limbs with each step. This applies regardless of the usable number of limbs—even arthropods, with six, eight, or more limbs, walk.

Difference from running

The word walk is descended from the Old English wealcan "to roll". In humans and other bipeds, walking is generally distinguished from running in that only one foot at a time leaves contact with the ground and there is a period of double-support. In contrast, running begins when both feet are off the ground with each step. This distinction has the status of a formal requirement in competitive walking events. For quadrupedal species, there are numerous gaits which may be termed walking or running, and distinctions based upon the presence or absence of a suspended phase or the number of feet in contact any time do not yield mechanically correct classification. The most effective method to distinguish walking from running is to measure the height of a person's centre of mass using motion capture or a force plate at mid-stance. During walking, the centre of mass reaches a maximum height at mid-stance, while running, it is then at a minimum. This distinction, however, only holds true for locomotion over level or approximately level ground. For walking up grades above 10%, this distinction no longer holds for some individuals. Definitions based on the percentage of the stride during which a foot is in contact with the ground (averaged across all feet) of greater than 50% contact corresponds well with identification of 'inverted pendulum' mechanics and are indicative of walking for animals with any number of limbs, although this definition is incomplete. Running humans and animals may have contact periods greater than 50% of a gait cycle when rounding corners, running uphill or carrying loads.

Speed is another factor that distinguishes walking from running. Although walking speeds can vary greatly depending on many factors such as height, weight, age, terrain, surface, load, culture, effort, and fitness, the average human walking speed at crosswalks is about 5.0 kilometres per hour (km/h), or about 1.4 meters per second (m/s), or about 3.1 miles per hour (mph). Specific studies have found pedestrian walking speeds at crosswalks ranging from 4.51 to 4.75 km/h (2.80 to 2.95 mph) for older individuals and from 5.32 to 5.43 km/h (3.31 to 3.37 mph) for younger individuals; a brisk walking speed can be around 6.5 km/h (4.0 mph). In Japan, the standard measure for walking speed is 80 m/min (4.8 km/h). Champion racewalkers can average more than 14 km/h (8.7 mph) over a distance of 20 km (12 mi).

An average human child achieves independent walking ability at around 11 months old.

Health benefits

Regular, brisk exercise of any kind can improve confidence, stamina, energy, weight control and life expectancy and reduces stress. It can also decrease the risk of coronary heart disease, strokes, diabetes, high blood pressure, bowel cancer and osteoporosis. Scientific studies have also shown that walking, besides its physical benefits, is also beneficial for the mind, improving memory skills, learning ability, concentration, mood, creativity, and abstract reasoning. Sustained walking sessions for a minimum period of thirty to sixty minutes a day, five days a week, with the correct walking posture, reduce health risks and have various overall health benefits, such as reducing the chances of cancer, type 2 diabetes, heart disease, anxiety disorder and depression. Life expectancy is also increased even for individuals suffering from obesity or high blood pressure. Walking also improves bone health, especially strengthening the hip bone, and lowering the harmful low-density lipoprotein (LDL) cholesterol, and raising the useful high-density lipoprotein (HDL) cholesterol. Studies have found that walking may also help prevent dementia and Alzheimer's. Walking at a pace that increases ones heart rate to 70% of their maximum heart rate, also known as the "fat-burning heart rate" can cause the body to utilize its fat reserves for energy leading to fat loss. An individual's maximum heart rate can be calculated by subtracting their age from 220.

The Centers for Disease Control and Prevention's fact sheet on the "Relationship of Walking to Mortality Among U.S. Adults with Diabetes" states that those with diabetes who walked for two or more hours a week lowered their mortality rate from all causes by 39 percent. Women who took 4,500 steps to 7,500 steps a day seemed to have fewer premature deaths compared to those who only took 2,700 steps a day. "Walking lengthened the life of people with diabetes regardless of age, gender, race, body mass index, length of time since diagnosis and presence of complications or functional limitations." It has been suggested that there is a relationship between the speed of walking and health, and that the best results are obtained with a speed of more than 2.5 mph (4.0 km/h).

New research in 2022 led to the recommendation that a commuter should walk at least 6000 steps, each weekday throughout a year, to reach optimal health effects.

Governments now recognize the benefits of walking for mental and physical health and are actively encouraging it. This growing emphasis on walking has arisen because people walk less nowadays than previously. In the UK, a Department of Transport report found that between 1995/97 and 2005 the average number of walk trips per person fell by 16%, from 292 to 245 per year. Many professionals in local authorities and the National Health Service are employed to halt this decline by ensuring that the built environment allows people to walk and that there are walking opportunities available to them. Professionals working to encourage walking come mainly from six sectors: health, transport, environment, schools, sport and recreation, and urban design.

One program to encourage walking is "The Walking the Way to Health Initiative", organized by the British walkers association The Ramblers, which is the largest volunteer led walking scheme in the United Kingdom. Volunteers are trained to lead free Health Walks from community venues such as libraries and doctors' surgeries. The scheme has trained over 35,000 volunteers and has over 500 schemes operating across the UK, with thousands of people walking every week. A new organization called "Walk England" launched a web site in June 2008 to provide these professionals with evidence, advice, and examples of success stories of how to encourage communities to walk more. The site has a social networking aspect to allow professionals and the public to ask questions, post news and events, and communicate with others in their area about walking, as well as a "walk now" option to find out what walks are available in each region. Similar organizations exist in other countries and recently a "Walking Summit" was held in the United States. This "assembled thought-leaders and influencers from business, urban planning and real estate, (along with) physicians and public health officials", and others, to discuss how to make American cities and communities places where "people can and want to walk". Walking is more prevalent in European cities that have dense residential areas mixed with commercial areas and good public transportation.

Jai Ganesh · Yesterday 00:42:47

1788) Jogging

Gist

Jogging is the activity of running at a slow, regular speed, especially as a form of exercise. (UK)

Jogging, form of running at an easy pace, particularly popular from the 1960s in the United States.

Summary

Jogging is a form of running at an easy pace, particularly popular from the 1960s in the United States. There, an estimated 7,000,000 to 10,000,000 joggers sought fitness, weight loss, grace, physical fulfillment, and relief from stress by jogging. Joggers expend from 10 to 13 calories per minute in this exercise (compared with approximately 7 to 9 calories per minute for tennis).

The popularity of this activity was given substantial impetus by the publication of the book Jogging (1967) by Bill Bowerman, a University of Oregon track coach, and W.E. Harris, a heart specialist. The practice of jogging originated in New Zealand when an Olympic track coach, one Dr. Lydiard, suggested it as a conditioning activity for retired Olympic runners; Bowerman observed the activity there and was impressed.

Jogging has been endorsed by many medical authorities for its value as a heart exercise and for general physical conditioning, usually to be practiced on alternate days. Other medical authorities, however, warn that fallen arches, shin splints, sweat miliaria, strained Achilles tendons, bruised heels, and knee and back ailments can result from jogging—usually done on hard surfaces with the feet striking the ground from 600 to 750 times per mile. Warm-up exercises before jogging, properly designed shoes, loose clothing, proper jogging technique, and general good health—as well as sensible objectives—are necessary for safe pursuit of the activity. The U.S. National Jogging Association was formed in 1968 to promote the pastime.

Details

Jogging is a form of trotting or running at a slow or leisurely pace. The main intention is to increase physical fitness with less stress on the body than from faster running but more than walking, or to maintain a steady speed for longer periods of time. Performed over long distances, it is a form of aerobic endurance training.

Definition

Jogging is running at a gentle pace; its definition, as compared with running, is not standard. In general, jogging speed is between 4 and 6 miles per hour (6.4 and 9.7 km/h) Running is sometimes defined as requiring a moment of no contact to the ground, whereas jogging often sustains the contact.

History

The word jog originated in England in the mid-16th century. The etymology of the word is unknown, but it may be related to shog or have been a new invention. In 1593, William Shakespeare wrote in Taming of the Shrew, "you may be jogging whiles your boots are green". At that point, it usually meant to leave.

The term jog was often used in English and North American literature to describe short quick movements, either intentional or unintentional. It is also used to describe a quick, sharp shake or jar. Richard Jefferies, an English naturalist, wrote of "joggers", describing them as quickly moving people who brushed others aside as they passed. This usage became common throughout the British Empire, and in his 1884 novel My Run Home, the Australian author Rolf Boldrewood wrote, "Your bedroom curtains were still drawn as I passed on my morning jog."

In the United States jogging was called "roadwork" when athletes in training, such as boxers, customarily ran several miles each day as part of their conditioning. In New Zealand during the 1960s or 1970s, the word "roadwork" was mostly supplanted by the word "jogging", promoted by coach Arthur Lydiard, who is credited with popularizing jogging. The idea of jogging as an organised activity was mooted in a sports page article in The New Zealand Herald in February 1962, which told of a group of former athletes and fitness enthusiasts who would meet once a week to run for "fitness and sociability". Since they would be jogging, the newspaper suggested that the club "may be called the Auckland Joggers' Club"—which is thought to be the first use of the noun "jogger". University of Oregon track coach Bill Bowerman, after jogging with Lydiard in New Zealand in 1962, started a joggers' club in Eugene in early 1963. He published the book Jogging in 1966, popularizing jogging in the United States.

Exercise

Jogging may also be used as a warm up or cool down for runners, preceding or following a workout or race. It is often used by serious runners as a means of active recovery during interval training. For example, a runner who completes a fast 400 meter repetition at a sub-5-minute mile pace (3 minute km) may drop to an 8-minute mile jogging pace (5 minute km) for a recovery lap.

Jogging can be used as a method to increase endurance or to provide a means of cardiovascular exercise but with less stress on joints or demand on the circulatory system.

Benefits

According to a study by Stanford University School of Medicine, jogging is effective in increasing human lifespan, and decreasing the effects of aging, with benefits for the cardiovascular system. Jogging is useful for fighting obesity and staying healthy.

The National Cancer Institute has performed studies that suggest jogging and other types of aerobic exercise can reduce the risk of lung, colon, breast and prostate cancers, among others. It is suggested by the American Cancer Society that jogging for at least 30 minutes five days a week can help in cancer prevention.

While jogging on a treadmill will provide health benefits such as cancer prevention, and aid in weight loss, a study published in BMC Public Health reports that jogging outdoors can have the additional benefits of increased energy and concentration. Jogging outdoors is a better way to improve energy levels and advance mood than using a treadmill at the gym.

Jogging also prevents muscle and bone damage that often occurs with age, improves heart performance and blood circulation and assists in preserving a balanced weight gain.

A Danish study released in 2015 reported that "light" and "moderate" jogging were associated with reduced mortality compared to both non-jogging and "strenuous" jogging. The optimal amount per week was 1 to 2.4 hours, the optimal frequency was less than or equal to 3 times per week and the optimal speed was "slow" or "average". A recent meta-analysis on running/jogging and mortality, including more than 230,000 participants found that runners were at 27% lower risk of death than non-runners, during 5.5-35 year follow-ups.

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Jai Ganesh · Today 00:27:46

1789) Running

Gist

Running is the act of a person, animal, or thing that runs.

Summary

Running is footracing over a variety of distances and courses and numbering among the most popular sports in nearly all times and places. Modern competitive running ranges from sprints (dashes), with their emphasis on continuous high speed, to grueling long-distance and marathon races, requiring great endurance.

Running is also a popular noncompetitive recreation that can produce important physiological benefits.

Details

Running is the way in which people or animals travel quickly on their feet. It is a method of travelling on land. It is different to walking in that both feet are regularly off the ground at the same time. Different terms are used to refer to running according to the speed: jogging is slow, and sprinting is running fast.

Running is a popular form of exercise. It is also one of the oldest forms of sport. The exercise is known to be good for health; it helps breathing and heartbeat, and burns any spare calories. Running keeps a person fit and active. It also relieves stress. Running makes a person thirsty, so it is important to drink water when running.

Benefits of running

* Fitness – From wanting to lose weight to trying to fight disease and aging, there are lots of health benefits to running.
* Mental health – Whether to help depression or find some time to think, there are large mental benefits to running as well.
* Running is also fun and does not need special equipment to do it. When running, the muscles, lungs, brain, heart and other organs get better.
* Running is often used as cross-training for many sports, especially ones that require sustained endurance.

Ways to avoid injuries

Running injuries are quite common among runners. Many running injuries can be reduced through proper training, wearing of the correct gear and awareness of the running environment.

Physical

* Before going on a long run, do not forget to have a five-minute warm-up and some stretching exercises.
* After going on a long run, do not forget to have ten-minutes of cool-down with some stretching exercises.
* In the short term, try running on a flat surface. In the long term coaches recommend cross-country running.
* Running in a way to reduce loading on legs. One method is to use a treadmill, the better is to run in minimal shoes.
These allow the runner's feet to feel the ground and so not inadvertently overload the foot/ankle. Over-cushioned shoes prevent the foot from feeling what it is doing and can also damage ones shins and knees. This topic has been very controversial. There are countless coaches, runners, and scientists who argue that minimal shoes are a main culprit in injuries in runners. They highly recommend shoes that offer stability and cushioning. Many runners with injuries have found that switching to cushioned shoes has improved/cured them of their injuries.

Environmental

* In hot climates, it is better to run in the morning. This will help to reduce fatigue and heat stress.
* Do not run when pollution levels are high.
* Run in the shade if possible, wear sunglasses, apply sunscreen and try to avoid direct sun rays.
* Too much clothing can produce sweating, which causes the body to lose heat quickly. Dress in layers. Wear the correct footwear.
* When running in cold weather wear hat, gloves and clothing that covers your neck.

Racing

Running is a part of many forms of competitive racing. Most running races test speed, endurance or both. Track and field races are usually divided into sprints, middle-distance races and long-distance races. Races held off the track may be called cross-country races. A marathon is run over 42 kilometres.

Footraces have probably existed for most of human history. They were an important part of the ancient Olympic Games.

Additional Information

Running is a method of terrestrial locomotion allowing humans and other animals to move rapidly on foot. Running is a type of gait characterized by an aerial phase in which all feet are above the ground (though there are exceptions). This is in contrast to walking, where one foot is always in contact with the ground, the legs are kept mostly straight and the center of gravity vaults over the stance leg or legs in an inverted pendulum fashion. A feature of a running body from the viewpoint of spring-mass mechanics is that changes in kinetic and potential energy within a stride co-occur, with energy storage accomplished by springy tendons and passive muscle elasticity. The term running can refer to any of a variety of speeds ranging from jogging to sprinting.

Running in humans is associated with improved health and life expectancy.

It is hypothesized that the ancestors of humankind developed the ability to run for long distances about 2.6 million years ago, probably to hunt animals. Competitive running grew out of religious festivals in various areas. Records of competitive racing date back to the Tailteann Games in Ireland between 632 BCE and 1171 BCE, while the first recorded Olympic Games took place in 776 BCE. Running has been described as the world's most accessible sport.

Description

Running gait can be divided into two phases regarding the lower extremity: stance and swing. These can be further divided into absorption, propulsion, initial swing, and terminal swing. Due to the continuous nature of running gait, no certain point is assumed to be the beginning. However, for simplicity, it will be assumed that absorption and footstrike mark the beginning of the running cycle in a body already in motion.

Footstrike

Footstrike occurs when a plantar portion of the foot makes initial contact with the ground. Common footstrike types include forefoot, midfoot, and heel strike types. These are characterized by initial contact of the ball of the foot, ball and heel of the foot simultaneously and heel of the foot respectively. During this time, the hip joint is undergoing extension from being in maximal flexion from the previous swing phase. For proper force absorption, the knee joint should be flexed upon the footstrike, and the ankle should be slightly in front of the body. Footstrike begins the absorption phase as forces from initial contact are attenuated throughout the lower extremity. Absorption of forces continues as the body moves from footstrike to midstance due to vertical propulsion from the toe-off during a previous gait cycle.

Midstance

Midstance is when the lower extremity limb of focus is in knee flexion directly underneath the trunk, pelvis, and hips. At this point, propulsion begins to occur as the hips undergo hip extension, the knee joint undergoes extension, and the ankle undergoes plantar flexion. Propulsion continues until the leg is extended behind the body and toe-off occurs. This involves a maximal hip extension, knee extension, and plantar flexion for the subject, resulting in the body being pushed forward from this motion, and the ankle/foot leaves the ground as the initial swing begins.

Propulsion phase

Most recent research, particularly regarding the footstrike debate, has focused solely on the absorption phases for injury identification and prevention. The propulsion phase of running involves the movement beginning at midstance until toe off. From a full stride length model however, components of the terminal swing and footstrike can aid in propulsion. Set up for propulsion begins at the end of the terminal swing as the hip joint flexes, creating the maximal range of motion for the hip extensors to accelerate through and produce force. As the hip extensors change from reciporatory inhibitors to primary muscle movers, the lower extremity is brought back toward the ground, although aided greatly by the stretch reflex and gravity. Footstrike and absorption phases occur next with two types of outcomes. This phase can be only a continuation of momentum from the stretch reflex reaction to hip flexion, gravity, and light hip extension with a heel strike, which does little to provide force absorption through the ankle joint. With a mid/forefoot strike, loading of the gastro-soleus complex from shock absorption will serve to aid in plantar flexion from midstance to toe-off. As the lower extremity enters the midstance, actual propulsion begins. The hip extensors continue contracting with help from the acceleration of gravity and the stretch reflex left over from maximal hip flexion during the terminal swing phase. Hip extension pulls the ground underneath the body, pulling the runner forward. During midstance, the knee should be in some degree of knee flexion due to elastic loading from the absorption and footstrike phases to preserve forward momentum. The ankle joint is in dorsiflexion at this point underneath the body, either elastically loaded from a mid/forefoot strike or preparing for stand-alone concentric plantar flexion. All three joints perform the final propulsive movements during toe-off. The plantar flexors plantar flex, pushing off from the ground and returning from dorsiflexion in midstance. This can either occur by releasing the elastic load from an earlier mid/forefoot strike or concentrically contracting from a heel strike. With a forefoot strike, the ankle and knee joints release their stored elastic energy from the footstrike/absorption phase. The quadriceps group/knee extensors go into full knee extension, pushing the body off of the ground. At the same time, the knee flexors and stretch reflex pull the knee back into flexion, adding to a pulling motion on the ground and beginning the initial swing phase. The hip extensors extend to the maximum, adding the forces pulling and pushing off of the ground. The hip extensors' movement and momentum also contribute to knee flexion and the beginning of the initial swing phase.

Swing phase

Initial swing is the response of both stretch reflexes and concentric movements to the propulsion movements of the body. Hip flexion and knee flexion occur, beginning the return of the limb to the starting position and setting up for another foot strike. The initial swing ends at midswing when the limb is again directly underneath the trunk, pelvis, and hip with the knee joint flexed and hip flexion continuing. Terminal swing then begins as hip flexion continues to the point of activation of the stretch reflex of the hip extensors. The knee begins to extend slightly as it swings to the anterior portion of the body. The foot then makes contact with the ground with a foot strike, completing the running cycle of one side of the lower extremity. Each limb of the lower extremity works opposite to the other. When one side is in toe-off/propulsion, the other hand is in the swing/recovery phase preparing for footstrike. Following toe-off and the beginning of the initial swing of one side, there is a flight phase where neither extremity is in contact with the ground due to the opposite side finishing terminal swing. As the footstrike of the one hand occurs, the initial swing continues. The opposing limbs meet with one in midstance and midswing, beginning the propulsion and terminal swing phases.

Upper extremity function

The upper extremity function serves mainly in providing balance in conjunction with the opposing side of the lower extremity. The movement of each leg is paired with the opposite arm, which serves to counterbalance the body, particularly during the stance phase. The arms move most effectively (as seen in elite athletes) with the elbow joint at approximately 90 degrees or less, the hands swinging from the hips up to mid-chest level with the opposite leg, the Humerus moving from being parallel with the trunk to approximately 45 degrees shoulder extension (never passing the trunk in flexion) and with as little movement in the transverse plane as possible. The trunk also rotates in conjunction with arm swing. It mainly serves as a balance point from which the limbs are anchored. Thus trunk motion should remain mostly stable with little motion except for slight rotation, as excessive movement would contribute to transverse motion and wasted energy.

Footstrike debate

Recent research into various forms of running has focused on the differences in the potential injury risks and shock absorption capabilities between heel and mid/forefoot footstrikes. It has been shown that heel striking is generally associated with higher rates of injury and impact due to inefficient shock absorption and inefficient biomechanical compensations for these forces. This is due to pressures from a heel strike traveling through bones for shock absorption rather than being absorbed by muscles. Since bones cannot disperse forces easily, the forces are transmitted to other parts of the body, including ligaments, joints, and bones in the rest of the lower extremities up to the lower back. This causes the body to use abnormal compensatory motions in an attempt to avoid serious bone injuries. These compensations include internal rotation of the tibia, knee, and hip joints. Excessive compensation over time has been linked to a higher risk of injuries in those joints and the muscles involved in those motions. Conversely, a mid/forefoot strike has been associated with greater efficiency and lower injury risk due to the triceps surae being used as a lever system to absorb forces with the muscles eccentrically rather than through the bone. Landing with a mid/forefoot strike has also been shown to properly attenuate shock and allow the triceps surae to aid in propulsion via reflexive plantarflexion after stretching to absorb ground contact forces. Thus a mid/forefoot strike may aid in propulsion. However, even among elite athletes, there are variations in self-selected footstrike types. This is especially true in longer distance events, where there is a prevalence of heel strikers. There does tend however to be a greater percentage of mid/forefoot striking runners in the elite fields, particularly in the faster racers and the winning individuals or groups. While one could attribute the faster speeds of elite runners compared to recreational runners with similar footstrikes to physiological differences, the hip, and joints have been left out of the equation for proper propulsion. This raises the question of how heel-striking elite distance runners can keep up such high paces with a supposedly inefficient and injurious foot strike technique.

Stride length, hip and knee function

Biomechanical factors associated with elite runners include increased hip function, use, and stride length over recreational runners. An increase in running speeds causes increased ground reaction forces, and elite distance runners must compensate for this to maintain their pace over long distances. These forces are attenuated through increased stride length via increased hip flexion and extension through decreased ground contact time and more energy being used in propulsion. With increased propulsion in the horizontal plane, less impact occurs from the decreased force in the vertical plane. Increased hip flexion allows for increased use of the hip extensors through midstance and toe-off, allowing for more force production. The difference even between world-class and national-level 1500-m runners has been associated with more efficient hip joint function. The increase in velocity likely comes from the increased range of motion in hip flexion and extension, allowing for greater acceleration and speed. The hip extensors and extension have been linked to more powerful knee extension during toe-off, contributing to propulsion. Stride length must be appropriately increased with some degree of knee flexion maintained through the terminal swing phases, as excessive knee extension during this phase along with footstrike has been associated with higher impact forces due to braking and an increased prevalence of heel striking. Elite runners tend to exhibit some degree of knee flexion at footstrike and midstance, which first serves to eccentrically absorb impact forces in the quadriceps muscle group. Secondly it allows for the knee joint to contract concentrically and provides significant aid in propulsion during toe-off as the quadriceps group is capable of producing large amounts of force. Recreational runners have been shown to increase stride length through increased knee extension rather than increased hip flexion, as exhibited by elite runners, which provides an intense braking motion with each step and decreases the rate and efficiency of knee extension during toe-off, slowing down speed. Knee extension, however, contributes to additional stride length and propulsion during toe-off and is seen more frequently in elite runners as well.

Good technique

Leaning forward places a runner's center of mass on the front part of the foot, which avoids landing on the heel and facilitates the use of the spring mechanism of the foot. It also makes it easier for the runner to avoid landing the foot in front of the center of mass and the resultant braking effect. While upright posture is essential, a runner should maintain a relaxed frame and use their core to keep posture upright and stable. This helps prevent injury as long as the body is neither rigid nor tense. The most common running mistakes are tilting the chin up and scrunching shoulders.

Stride rate and types

Exercise physiologists have found that the stride rates are extremely consistent across professional runners, between 185 and 200 steps per minute. The main difference between long- and short-distance runners is the length of stride rather than the rate of stride.

During running, the speed at which the runner moves may be calculated by multiplying the cadence (steps per minute) by the stride length. Running is often measured in terms of pace, expressed in units of minutes per mile or minutes per kilometer (the inverse of speed, in mph or km/h). Some coaches advocate training at a combination of specific paces related to one's fitness in order to stimulate various physiological improvements.

Different types of stride are necessary for different types of running. When sprinting, runners stay on their toes bringing their legs up, using shorter and faster strides. Long-distance runners tend to have more relaxed strides that vary.

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