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#26 2017-11-03 00:41:06

ganesh
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Registered: 2005-06-28
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Re: Miscellany

26) Great Wall Of China

The Great Wall of China is a series of fortifications made of stone, brick, tamped earth, wood, and other materials, generally built along an east-to-west line across the historical northern borders of China to protect the Chinese states and empires against the raids and invasions of the various nomadic groups of the Eurasian Steppe. Several walls were being built as early as the 7th century BC; these, later joined together and made bigger and stronger, are now collectively referred to as the Great Wall. Especially famous is the wall built 220–206 BC by Qin Shi Huang, the first Emperor of China. Little of that wall remains. Since then, the Great Wall has on and off been rebuilt, maintained, and enhanced; the majority of the existing wall is from the Ming Dynasty.

Other purposes of the Great Wall have included border controls, allowing the imposition of duties on goods transported along the Silk Road, regulation or encouragement of trade and the control of immigration and emigration. Furthermore, the defensive characteristics of the Great Wall were enhanced by the construction of watch towers, troop barracks, garrison stations, signaling capabilities through the means of smoke or fire, and the fact that the path of the Great Wall also served as a transportation corridor.

The Great Wall stretches from Dandong in the east, to Lop Lake in the west, along an arc that roughly delineates the southern edge of Inner Mongolia. A comprehensive archaeological survey, using advanced technologies, has concluded that the Ming walls measure 8,850 km (5,500 mi). This is made up of 6,259 km (3,889 mi) sections of actual wall, 359 km (223 mi) of trenches and 2,232 km (1,387 mi) of natural defensive barriers such as hills and rivers. Another archaeological survey found that the entire wall with all of its branches measure out to be 21,196 km (13,171 mi).

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#27 2017-11-05 01:10:53

ganesh
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Registered: 2005-06-28
Posts: 23,372

Re: Miscellany

27) The Four Largest Islands of Japan

The Japanese archipelago consists of nearly 7,000 islands. However, roughly 97% of Japan's landmass (377,835 sq km / 234,776 sq. miles) is comprised of the four main islands: Hokkaido, Honshu, Kyushu, and Shikoku.

The Japanese archipelago consists of thousands of islands, but the Japan of world maps -- the bow-shaped country in the Pacific curling around the east coast of continental Asia -- is made up of four main islands: Hokkaido, Honshu, Kyushu and Shikoku. Honshu is the largest, roughly the size of Minnesota, followed by Hokkaido, Kyushu and Shikoku. Each island offers something a little different for the tourist, but the four are unified by Japan's technology and hospitality.

Honshu

When you look at a map of Japan, you can see the divides between its four main land masses. Honshu is central, with Tokyo in the central part of the island. The main island is also home Osaka, Kobe, Kyoto and Nagoya, and the majority of Japan's population lives here. Most international flights to Japan arrive through Tokyo or Osaka, so Honshu is the most frequently visited island, partly by default. Its large cities take some getting used to for the traveler, but with great reward. Starting a Honshu trip in Osaka makes sense, as Kobe, Kyoto and the spectacular Nara are only an hour away by train, some high-speed, some commuter. All major cities in Honshu are connected by rail, though flying on the longer trips -- Hiroshima to Tokyo, for example -- might be more economical.

Hokkaido

Hokkaido is the dot on the Japanese "j," the second-largest and northernmost island. Hokkaido's largest city is Sapporo, where the well known Japanese beer of the same name comes from, and most Hokkaido vacations begin here. The island is known for its natural landscape, with an abundance of national parks and festivals celebrating its earthly beauty. Hokkaido's Winter Festival brings visitors from around the world and around Japan to the region each year, and the Hokkaido's mountains draw skiers and snowboarders to their deep, pristine powder.

Kyushu

Kyushu is Japan's third-largest island and the southernmost of the main four. Despite being separated by a small gulf from Honshu, Kyushu is well-connected by rail and bus service to Honshu. Kyushu's largest city is Fukuoka, the fourth-largest city in Japan, an industrial metropolis on the northern edge of Kyushu. While Fukuoka is the central hub of the island, it's by no means the most interesting city. Nagasaki is smaller, but quaint, with old stone streets, trolleys, shopping and museums. Kumamoto, two hours south of Fukuoka, is an old fortress city, with one of Japan's oldest and best-maintained feudal castles and walls evoking the Japan of the nation's nightly historical dramas.

Shikoku

The smallest of Japan's four main islands, Shikoku has a bit of a little-sibling complex. It doesn't boast mountains as big as those in northern Honshu or Hokkaido, and it doesn't have the same near-tropical climate as southern Kyushu. So Shikoku is modest, offering tourists a tamer version of the busier tourist regions of Japan. Its natural scenery is its key draw, with smallish mountains under 6,000 feet that appeal to outdoors enthusiasts in moderate physical shape. Each year, Shikoku is home to a Buddhist pilgrimage, as pilgrims, mostly from around Japan, come to circumnavigate the island. In the past, pilgrims walked clockwise around the island and some disappeared forever in the mountainside forests; now, motorways and cell phones make disappearing almost impossible, but the festival remains strongly rooted in the Shikoku consciousness.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#28 2017-11-07 23:01:17

ganesh
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Registered: 2005-06-28
Posts: 23,372

Re: Miscellany

28) Laser

A laser is a coherent and focused beam of photons; coherent, in this context, means that it is all one wavelength, unlike ordinary light which showers on us in many wavelengths.

The acronym laser stands for "light amplification by stimulated emission of radiation." Lasers work as a result of resonant effects. The output of a laser is a coherent electromagnetic field. In a coherent beam of electromagnetic energy, all the waves have the same frequency and phase.

In a basic laser, a chamber called a cavity is designed to internally reflect infrared (IR), visible-light, or ultraviolet (UV) waves so they reinforce each other. The cavity can contain gases, liquids, or solids. The choice of cavity material determines the wavelength of the output. At each end of the cavity, there is a mirror. One mirror is totally reflective, allowing none of the energy to pass through; the other mirror is partially reflective, allowing approximately 5 percent of the energy to pass through. Energy is introduced into the cavity from an external source; this is called pumping.

As a result of pumping, an electromagnetic field appears inside the laser cavity at the natural (resonant) frequency of the atoms of the material that fills the cavity. The waves reflect back and forth between the mirrors. The length of the cavity is such that the reflected and re-reflected wave fronts reinforce each other in phase at the natural frequency of the cavity substance. Electromagnetic waves at this resonant frequency emerge from the end of the cavity having the partially-reflective mirror. The output may appear as a continuous beam, or as a series of brief, intense pulses.

The ruby laser, a simple and common type, has a rod-shaped cavity made of a mixture of solid aluminum oxide and chromium. The output is in pulses that last approximately 500 microseconds each. Pumping is done by means of a helical flash tube wrapped around the rod. The output is in the red visible range.

A blue laser has a shorter wavelength than the red laser, and the ability to store and read two to four times the amount of data.

The helium-neon laser is another popular type, favored by electronics hobbyists because of its moderate cost. As its name implies, it has a cavity filled with helium and neon gases. The output of the device is bright crimson. Other gases can be used instead of helium and neon, producing beams of different wavelengths. Argon produces a laser with blue visible output. A mixture of nitrogen, carbon dioxide, and helium produces IR output.

Lasers are one of the most significant inventions developed during the 20th century. They have found a tremendous variety of uses in electronics, computer hardware, medicine, and experimental science.

laser-experiment.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#29 2017-11-10 07:49:33

ganesh
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Re: Miscellany

29) United Nations

Overview

The United Nations is an international organization founded in 1945.  It is currently made up of 193 Member States.  The mission and work of the United Nations are guided by the purposes and principles contained in its founding Charter.

Member States

Each of the 193 Member States of the United Nations is a member of the General Assembly.  States are admitted to membership in the UN by a decision of the General Assembly upon the recommendation of the Security Council.

Main Organs

The main organs of the UN are the General Assembly, the Security Council, the Economic and Social Council, the Trusteeship Council, the International Court of Justice, and the UN Secretariat.  All were established in 1945 when the UN was founded.

Leadership

The Secretary-General of the United Nations is a symbol of the Organization's ideals and a spokesman for the interests of the world's peoples, in particular the poor and vulnerable. The current Secretary-General of the UN, and the ninth occupant of the post, is Mr. António Guterres of Portugal, who took office on 1 January 2017. The UN Charter describes the Secretary-General as "chief administrative officer" of the Organization.

Secretariat

The Secretariat, one of the main organs of the UN, is organized along departmental lines, with each department or office having a distinct area of action and responsibility. Offices and departments coordinate with each other to ensure cohesion as they carry out the day to day work of the Organization in offices and duty stations around the world.  At the head of the United Nations Secretariat is the Secretary-General.

Funds, Programmes, Specialized Agencies and Others

The UN system, also known unofficially as the "UN family", is made up of the UN itself and many affiliated programmes, funds, and specialized agencies, all with their own membership, leadership, and budget.  The programmes and funds are financed through voluntary rather than assessed contributions. The Specialized Agencies are independent international organizations funded by both voluntary and assessed contributions.

united_nations_logo_295.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#30 2017-11-14 02:01:59

ganesh
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Registered: 2005-06-28
Posts: 23,372

Re: Miscellany

30) Angstrom (Angstrom unit)

The angstrom, also known as the angstrom unit, is a measure of displacement equal to 0.0000000001 meter

. It is sometimes used to express wavelength s of visible light, ultraviolet (UV) light, X rays, and gamma rays.


The visible-light spectrum extends from approximately 7700 angstroms (red light) to 3900 angstroms (violet light). This corresponds to frequencies of 390 to 770 terahertz (THz), where 1 THz = 10 12 Hz. Ultraviolet radiation, X rays, and gamma rays have progressively shorter wavelengths and higher frequencies. Some gamma rays have wavelengths less than
0.0001

angstrom.

The angstrom is not often used nowadays. It has been largely superseded by the nanometer (nm), which is 10 times larger; 1 nm = 10 angstroms =

m.

wavelength-color.PNG


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#31 2017-11-18 14:43:32

ganesh
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Re: Miscellany

31) Bathyscaphe

Bathyscaphe, navigable diving vessel, developed by the Swiss educator and scientist Auguste Piccard (with assistance in later years from his son Jacques), designed to reach great depths in the ocean.

The first bathyscaphe, the FNRS 2, built in Belgium between 1946 and 1948, was damaged during 1948 trials in the Cape Verde Islands. Substantially rebuilt and greatly improved, the vessel was renamed FNRS 3 and carried out a series of descents under excellent conditions, including one of 4,000 metres (13,000 feet) into the Atlantic off Dakar, Senegal, on February 15, 1954. A second improved bathyscaphe, the Trieste, was launched on August 1, 1953, and dived to 3,150 metres (10,300 feet) in the same year. In 1958 the Trieste was acquired by the United States Navy, taken to California, and equipped with a new cabin designed to enable it to reach the seabed of the great oceanic trenches. Several successive descents were made into the Pacific by Jacques Piccard, and on January 23, 1960, Piccard, accompanied by Lieutenant Don Walsh of the U.S. Navy, dived to a record 10,916 metres (35,814 feet) in the Pacific’s Mariana Trench.

The bathyscaphe consists of two main components: a steel cabin, heavier than water and resistant to sea pressure, to accommodate the observers; and a light container called a float, filled with gasoline, which, being lighter than water, provides the necessary lifting power. The cabin and float are closely linked. On the surface, one or more ballast tanks filled with air provide enough lift to keep the bathyscaphe afloat. When the ballast tank valves are opened, air escapes and is replaced by water, making the whole device heavy enough to start its descent. The gasoline is in direct contact with the sea water and so is compressed at a rate almost exactly in proportion to the prevailing depth. Thus, the bathyscaphe gradually loses buoyancy as it descends, and the speed of its descent tends to increase rapidly. To slow down or to begin the reascent, the pilot releases ballast that consists essentially of iron shot stored in silos and held in place by electromagnets.

bathyscaphe_Trieste.jpg


It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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#32 Yesterday 19:43:39

ganesh
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Registered: 2005-06-28
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Re: Miscellany

32) Gulf of Mexico

Gulf of Mexico, Spanish Golfo de México, partially landlocked body of water on the southeastern periphery of the North American continent. It is connected to the Atlantic Ocean by the Straits of Florida, running between the peninsula of Florida and the island of Cuba, and to the Caribbean Sea by the Yucatán Channel, which runs between the Yucatán Peninsula and Cuba. Both of these channels are about 100 miles (160 km) wide. The gulf’s greatest east-west and north-south extents are approximately 1,100 and 800 miles (1,800 and 1,300 km), respectively, and it covers an area of some 600,000 square miles (1,550,000 square km). To the northwest, north, and northeast it is bounded by the southern coast of the United States, while to the west, south, and southeast it is bounded by the east coast of Mexico.

Physical Features

Physiography and geology

The Gulf of Mexico consists of several ecological and geologic provinces, chief of which are the coastal zone, the continental shelf, the continental slope, and the abyssal plain. The coastal zone consists of tidal marshes, sandy beaches, mangrove-covered areas, and many bays, estuaries, and lagoons. The continental shelf forms an almost continuous terrace around the margin of the gulf; its width varies from a maximum of more than 200 miles (320 km) to a minimum of about 25 miles (40 km). Off the west coast of Florida as well as off the Yucatán Peninsula, the continental shelf consists of a broad area composed primarily of carbonate material. The remainder of the shelf consists of sand, silt, and clay sediments. On the shelf and on the slope that dips downward to the abyssal plain, buried salt domes occur at various depths; economically important deposits of oil and natural gas are associated with them. The abyssal plain, which forms the floor of the gulf, consists of a large triangular area near the centre, bounded by abrupt fault scarps toward Florida and the Yucatán Peninsula and by more gentle slopes to the north and west. The basin is unusually flat, having a gradient of only about 1 foot (0.3 metre) in every 8,000 feet (2,440 metres). The deepest point is in the Mexico Basin (Sigsbee Deep), which is 17,070 feet (5,203 metres) below sea level. From the floor of the basin rise the Sigsbee Knolls, some of which attain heights of 1,300 feet (400 metres); these are surface expressions of the buried salt domes.

Hydrology

The southeastern portion of the gulf is traversed by a riverlike current that becomes the main source of the North Atlantic Gulf Stream; this is the principal current moving oceanic waters through the gulf. Water from the Caribbean enters through the Yucatán Channel, the floor of which forms a sill (submarine ridge between basins) at about 1 mile (1.6 km) beneath the surface, and flows out in a clockwise direction via the Straits of Florida. Meandering masses of water, called loop currents, break off from the main stream and also move clockwise into the northeastern part of the gulf. Both seasonal and annual variations occur in these loop currents. A less well-defined pattern exists in the western gulf. There the currents are relatively weak, varying appreciably in intensity with season and location. There is extreme variability in both current direction and speed on the continental shelf and in the coastal waters of the gulf, where currents are subjected to seasonal and annual variations caused not only by major circulation patterns but also by changes in the prevailing wind direction.

The various rivers flowing into the Gulf of Mexico drain a land area roughly double that of the gulf, and the salinity of the gulf is subject to wide variations. In the open gulf the salinity is comparable to that of the North Atlantic, about 36 parts per thousand. This proportion, however, varies markedly during the year in coastal waters, particularly near the outflow of the broad delta region of the Mississippi River. During periods when the volume of the Mississippi’s flow is greatest, salinities as low as 14 to 20 parts per thousand occur as far as some 20 to 30 miles (30 to 50 km) offshore.

Sea surface temperatures in February vary between 64 °F (18 °C) in the northern gulf and 76 °F (24 °C) off the Yucatán coast. In the summer, surface temperatures of about 90 °F (32 °C) have been measured, but the usual variation is nearly the same as that experienced in February. Bottom-water temperatures of about 43 °F (6 °C) have been recorded near the northern part of the Yucatán Channel. The thickness of the isothermal layer (a surface layer of water of constant temperature) varies from about 3 to more than 500 feet (1 to more than 150 metres), depending on seasonal and local conditions as well as on location. The tidal range is small, averaging less than two feet in most places; in general, only diurnal tides occur—i.e., one period of high water and one of low water during each tidal day (24 hours and 50 minutes).

Climate

The climate of the gulf region varies from tropical to subtropical. Of particular note are the often-devastating hurricanes (tropical cyclones) that strike the region nearly every year. The hurricane season officially runs from June 1 to November 30, during which time meteorologic and oceanographic conditions are conducive for hurricanes to develop anywhere in the gulf. Particularly damaging hurricanes included one in Galveston, Texas, in 1900 and another in and around New Orleans in 2005. Hurricanes spawned in the North Atlantic may also move through the gulf at that time, often picking up strength.

Economic Aspects

Biological resources

The shores of the Gulf of Mexico are a major habitat for waterfowl and shorebirds. Substantial colonies of noddies, boobies, pelicans, and other seabirds winter along the coasts of Mexico and Cuba, as well as on offshore islands. There is a marked absence of marine mammals; the only one of significance, the Caribbean manatee, is diminishing in number.

The gulf waters contain huge populations of fish, particularly along the continental shelf. Commercial fishing is of major economic importance and supplies roughly one-fifth of the total catch in the United States. Shrimps, flounder, red snappers, mullet, oysters, and crabs are the most important commercial species for human consumption. In addition, a large quantity of the fish caught is used to provide fish protein concentrate for animal feeds; menhaden provide the bulk of this catch.

Mineral resources

The shallow continental shelf regions of the Gulf of Mexico contain large deposits of petroleum and natural gas. These deposits have been developed extensively since the 1940s and provide a substantial proportion of domestic needs in the United States. Offshore wells have been drilled primarily in the waters off the coasts of Texas and Louisiana and off Mexico in the Bay of Campeche. Sulfur is also extracted from wells drilled on the continental shelf off Louisiana. Oyster shells are obtained from the shallow waters of the Texas Gulf Coastal Plain and from bays and estuaries. These are used in the chemical industry as a source of calcium carbonate and also provide material for building roads.

Recreation

The coastal waters of the Gulf of Mexico are used extensively for sport fishing, especially for red snappers, flounder, and tarpon. Boating, swimming, and scuba diving also are popular recreations. The Gulf Coast has become a popular tourist destination, especially during winter. Tourism has developed primarily since World War II and has become one of the major components of the regional economy. In addition, the coastal areas, particularly in Florida, have developed into large retirement communities.

The impact of human activity

Shifting demographic patterns in the United States since 1950 have brought millions of new residents to the gulf region. This growing population has increased the demand for fresh water and generated large quantities of sewage and industrial waste (including heavy metals and polychlorinated biphenyls), much of which have been discharged directly into gulf waters or indirectly by rivers draining into the gulf. Offshore drilling has brought oil spills that, on occasion, have fouled beaches and destroyed marine life. More damaging, however, have been modern agricultural practices in much of the United States and Mexico, resulting in runoff contaminated with tremendous amounts of chemical pesticides, herbicides, and fertilizers. Blooms of red algae (Rhodophyta) and regions of oxygen depletion (hypoxia) have increased in frequency, size, and duration; these occurrences have been tied to the introduction into the gulf of large amounts of phosphates and nitrogen, particularly from the outflow of the Mississippi River. Off Louisiana, erosion and changes in relative sea level have caused the submergence of large areas of coastal wetlands; and pollution, siltation, and filling have resulted in the destruction of large areas of the gulf’s mangroves and many of its coral reefs.

Study And Exploration

After Christopher Columbus first made contact with the region in 1492, waves of Spanish explorers entered the gulf and penetrated into the North American interior. By 1600 the major physical features had been discovered, and a system of towns, silver mines, and missions had been established around the gulf shore. Little scientific study of the gulf was carried out until the 20th century, but since then the gulf has come to resemble something of a vast natural laboratory. Major marine research centres are located throughout the region, notably in Texas, Louisiana, and Florida. The gulf has become renowned for the diversity of its marine biota and the dynamics of its numerous barrier beaches; and, because of its vast oil reserves, the stratigraphy of its continental shelf has been studied by geophysicists and seismologists to a greater degree than perhaps that of any other oceanic basin. The frequent occurrence of hurricanes and other tropical storms in the gulf also has made it the focus of much research in climatology.

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It is no good to try to stop knowledge from going forward. Ignorance is never better than knowledge - Enrico Fermi. 

Nothing is better than reading and gaining more and more knowledge - Stephen William Hawking.

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