Posts by Jai Ganesh

Jai Ganesh · Dark Discussions at Cafe Infinity

2395) Robert Burns Woodward

Gist:

Work

Nature is full of organic substances—a large and highly diverse array of chemical compounds that contain the basic element carbon. Building, or synthesizing, organic substances using chemical methods is important in both scientific and industrial contexts. Synthesis often entails complicated, multistep processes. Robert Woodward mastered these processes and, in the 1950s and 1960s, successfully synthesized a large number of substances: quinine, cholesterol, cortisone, several antibiotic substances, and chlorophyll, the substance that gives leaves their green color.

Summary:

Robert Burns Woodward (born April 10, 1917, Boston, Mass., U.S.—died July 8, 1979, Cambridge, Mass.) was an American chemist best known for his syntheses of complex organic substances, including cholesterol and cortisone (1951), strychnine (1954), and vitamin B12 (1971). He was awarded the Nobel Prize for Chemistry in 1965, “for his outstanding achievements in the art of organic chemistry.”

Early life and education

Woodward’s early years are often told as the story of a boy-genius. He was an autodidact who, even as a child, had a passion for chemistry. At age 14, Woodward bought a copy of Ludwig Gattermann’s Practical Methods of Organic Chemistry and requested issues of chemistry journals from Verlag Chemie of Berlin. Later in life he did nothing to discourage a persistent legend that he had performed all the experiments in Gattermann’s book.

Woodward entered the Massachusetts Institute of Technology in 1933, then lost interest in, and patience with, the undergraduate routine and dropped out. Not wishing to lose such a gifted student, James Flack Norris, an organic chemistry professor, tracked down Woodward in the food technology department. Norris interceded, and Woodward was allowed to fulfill his course requirements by examination. In just four years Woodward obtained both bachelor’s and doctoral degrees. Upon graduation, he spent the summer of 1937 at the University of Illinois, leaving in the fall to join the chemistry department at Harvard University, where he remained until his death in 1979. Woodward was married in 1938 to Irja Pullman and in 1946 to Eudoxia Muller; he had two daughters from the first marriage and a daughter and son from the second.

Scientific career

The chemistry of natural products was Woodward’s base for a broad engagement in organic chemistry. During World War II, Woodward worked on the structural elucidation of penicillin, and he and William Doering sought synthetic routes to quinine. In 1948 Woodward published the structure of strychnine, beating English chemist Robert Robinson in the competition to solve this difficult chemical puzzle. During the 1950s, Woodward collaborated with the pharmaceutical company Pfizer, Inc., on the structural analysis of a new series of antibiotics: terramycin, aureomycin, and magnamycin.

Woodward was known among his colleagues for his aggressive use of the latest analytic tools. He strongly believed in the utility of instruments such as spectrophotometers in organic synthesis. Such instruments could routinely assist the chemist in the characterization of compounds, and they suggested new generalizations about the relationship of structure to physical properties. Indeed, Woodward’s early theoretical pursuits centred on the use of two types of physical data—ultraviolet absorption (1941–42) and optical rotatory dispersion (1961). Both of these generalizations about spectra and structure created new utility for routine spectroscopic measurements. These instrumental techniques altered the traditional, complementary relationship between synthesis and structural determination and reduced the latter to a relatively commonplace procedure.

Nevertheless, Woodward’s achievements in the field of structure determination remain milestones in organic chemistry: penicillin (1945), patulin (1948), strychnine (1947), ferrocene (1952), cevine (1954), gliotoxin (1958), ellipticine (1959), calycanthine (1960), oleandomycin (1960), streptonigrin (1963), and tetrodotoxin (1964). With the American biochemist Konrad Bloch, he also first proposed the correct biosynthetic pathway to the steroid hormones in living organisms.

Woodward undertook and completed one of the first total syntheses of the steroids cholesterol and cortisone (1951) and then the related terpene lanosterol (1954). In 1954 syntheses of strychnine and lysergic acid were announced, followed in 1956 by a synthesis of reserpine that has become a model of elegant technique and has been used for the commercial production of this tranquilizer. Subsequent achievements included the synthesis of chlorophyll (1960), tetracycline (1962), colchicine (1963), and cephalosporin C (1965). In a large-scale collaboration with Albert Eschenmoser of the Federal Institute of Technology in Zürich, Woodward completed in 1971 the synthesis of the complicated coenzyme vitamin B12 (cyanocobalamin) by a sequence of more than 100 reactions. The work on vitamin B12 led to the recognition and formulation, with the American chemist Roald Hoffmann, of the concept of conservation of orbital symmetry, explicating a broad group of fundamental reactions. These Woodward-Hoffman rules were probably the most important theoretical advance of the 1960s in organic chemistry. At the time of his death, Woodward was working on the synthesis of erythromycin.

Woodward lived between the worlds of academy and industry. During his career, he held consultancies with Eli Lilly and Company, Merck & Co., Inc., Mallinckrodt Pharmaceuticals, Monsanto Company, Polaroid Corporation, and Pfizer. In 1963 Ciba (later Ciba-Geigy Ltd., now Novartis International AG), a Swiss pharmaceutical firm, set up the Woodward Research Institute in Basel. He then held dual appointments as director of the institute and as Donner Professor of Science at Harvard. Between Basel and Cambridge, more than 400 graduate and postdoctoral students trained in Woodward’s laboratories.

The Woodward style

Woodward’s talks and lectures on organic chemistry were fastidious, well prepared, and long. Careful precision was the hallmark of his chemical work as well. Woodward was known for his innovative thinking on the theory of organic chemistry. Throughout his career, he demonstrated that the understanding of chemical reaction mechanisms made possible the planning and successful execution of extended sequences of reactions to build up complex compounds. The requisite intellectual discipline, largely initiated by Woodward, did indeed become a major endeavour in organic chemistry.

Woodward’s genius lay not in the creation of new reagents—that is, new synthetic methods—but in his power to marshal all the available facts and solve even the most intricate of puzzles. He had an enormous capacity for information and superb mental organization. Given the set of data on a structure or the planning of a synthesis, Woodward brought to bear a most remarkable ability to see the entire problem at once and to solve it systematically. His brilliance lay in the quality and depth of his thought, his painstaking preparations, and his chemical intuition. Woodward’s work was central to the chemical thought of the times, and his influence on other organic chemists was arguably greater than that of any other in his era.

Details

Robert Burns Woodward (April 10, 1917 – July 8, 1979) was an American organic chemist. He is considered by many to be the preeminent synthetic organic chemist of the twentieth century, having made many key contributions to the subject, especially in the synthesis of complex natural products and the determination of their molecular structure. He worked closely with Roald Hoffmann on theoretical studies of chemical reactions. He was awarded the Nobel Prize in Chemistry in 1965.

Early life and education

Woodward was born in Boston, Massachusetts, on April 10, 1917. He was the son of Margaret Burns (an immigrant from Scotland who claimed to be a descendant of the poet, Robert Burns) and her husband, Arthur Chester Woodward, himself the son of Roxbury apothecary, Harlow Elliot Woodward.

His father was one of the many victims of the 1918 influenza pandemic.

From a very early age, Woodward was attracted to and engaged in private study of chemistry while he attended a public primary school, and then Quincy High School, in Quincy, Massachusetts. By the time he entered high school, he had already managed to perform most of the experiments in Ludwig Gattermann's then widely used textbook of experimental organic chemistry. In 1928, Woodward contacted the Consul-General of the German consulate in Boston (Baron von Tippelskirch), and through him, managed to obtain copies of a few original papers published in German journals. Later, in his Cope lecture, he recalled how he had been fascinated when, among these papers, he chanced upon Diels and Alder's original communication about the Diels–Alder reaction. Throughout his career, Woodward was to repeatedly and powerfully use and investigate this reaction, both in theoretical and experimental ways. In 1933, he entered the Massachusetts Institute of Technology (MIT), but neglected his formal studies badly enough to be excluded at the end of the 1934 fall term. MIT readmitted him in the 1935 fall term, and by 1936 he had received the Bachelor of Science degree. Only one year later, MIT awarded him the doctorate, when his classmates were still graduating with their bachelor's degrees. Woodward's doctoral work involved investigations related to the synthesis of the female sex hormone estrone. MIT required that graduate students have research advisors. Woodward's advisors were James Flack Norris and Avery Adrian Morton, although it is not clear whether he actually took any of their advice. After a short postdoctoral stint at the University of Illinois, he took a Junior Fellowship at Harvard University from 1937 to 1938, and remained at Harvard in various capacities for the rest of his life. In the 1960s, Woodward was named Donner Professor of Science, a title that freed him from teaching formal courses so that he could devote his entire time to research.

Research and career:

Early work

The first major contribution of Woodward's career in the early 1940s was a series of papers describing the application of ultraviolet spectroscopy in the elucidation of the structure of natural products. Woodward collected together a large amount of empirical data, and then devised a series of rules later called the Woodward's rules, which could be applied to finding out the structures of new natural substances, as well as non-natural synthesized molecules. The expedient use of newly developed instrumental techniques was a characteristic Woodward exemplified throughout his career, and it marked a radical change from the extremely tedious and long chemical methods of structural elucidation that had been used until then.

In 1944, with his post doctoral researcher, William von Eggers Doering, Woodward reported the synthesis of the alkaloid quinine, used to treat malaria. Although the synthesis was publicized as a breakthrough in procuring the hard to get medicinal compound from Japanese occupied southeast Asia, in reality it was too long and tedious to adopt on a practical scale. Nevertheless, it was a landmark for chemical synthesis. Woodward's particular insight in this synthesis was to realize that the German chemist Paul Rabe had converted a precursor of quinine called quinotoxine to quinine in 1905. Hence, a synthesis of quinotoxine (which Woodward actually synthesized) would establish a route to synthesizing quinine. When Woodward accomplished this feat, organic synthesis was still largely a matter of trial and error, and nobody thought that such complex structures could actually be constructed. Woodward showed that organic synthesis could be made into a rational science, and that synthesis could be aided by well-established principles of reactivity and structure. This synthesis was the first one in a series of exceedingly complicated and elegant syntheses that he would undertake.

Later work and its impact

Culminating in the 1930s, the British chemists Christopher Ingold and Robert Robinson among others had investigated the mechanisms of organic reactions, and had come up with empirical rules which could predict reactivity of organic molecules. Woodward was perhaps the first synthetic organic chemist who used these ideas as a predictive framework in synthesis. Woodward's style was the inspiration for the work of hundreds of successive synthetic chemists who synthesized medicinally important and structurally complex natural products.

Jai Ganesh · This is Cool

2447) Laughing Gas

Gist

Laughing gas is the common name for nitrous oxide (N2O), a colorless gas with a slightly sweet odor and taste that is used medically as an anesthetic and pain reliever, particularly in dentistry and surgery. It is also used as a propellant in whipped cream, as an oxidizer in rocket engines, and has recreational uses for its euphoric effects. In the environment, it is a powerful greenhouse gas and a major contributor to ozone depletion.

N2O is called laughing gas because inhaling it produces euphoric, giggling effects due to its anesthetic properties. This colloquial name was given by Humphry Davy, and the gas's ability to cause a brief "high" is why it's used recreationally.

Summary

Nitrous oxide (dinitrogen oxide or dinitrogen monoxide), commonly known as laughing gas, nitrous, or factitious air, among others, is a chemical compound, an oxide of nitrogen with the formula N2O. At room temperature, it is a colourless non-flammable gas, and has a slightly sweet scent and taste. At elevated temperatures, nitrous oxide is a powerful oxidiser similar to molecular oxygen.

Nitrous oxide has significant medical uses, especially in surgery and dentistry, for its anaesthetic and pain-reducing effects, and it is on the World Health Organization's List of Essential Medicines. Its colloquial name, "laughing gas", coined by Humphry Davy, describes the euphoric effects upon inhaling it, which cause it to be used as a recreational drug inducing a brief "high". When abused chronically, it may cause neurological damage through inactivation of vitamin B12. It is also used as an oxidiser in rocket propellants and motor racing fuels, and as a frothing gas for whipped cream.

Nitrous oxide is also an atmospheric pollutant, with a concentration of 333 parts per billion (ppb) in 2020, increasing at 1 ppb annually. It is a major scavenger of stratospheric ozone, with an impact comparable to that of CFCs. About 40% of human-caused emissions are from agriculture, as nitrogen fertilisers are digested into nitrous oxide by soil micro-organisms. As the third most important greenhouse gas, nitrous oxide substantially contributes to global warming. Reduction of emissions is an important goal in the politics of climate change.

(CFC: Chlorofluorocarbons).

Details:

Nitrous oxide (laughing gas) is a sedative healthcare providers use to keep you comfortable during procedures. It’s a colorless, faintly sweet-smelling gas that you breathe in through a nosepiece. Unlike other sedation options, you can drive shortly after receiving nitrous oxide.

What is nitrous oxide (laughing gas)?

Nitrous oxide (N20) — commonly known as laughing gas — is a type of short-acting sedative. It’s a colorless, slightly sweet-smelling gas that you breathe in through a mask or nosepiece.

Physicians and dentists have been using nitrous oxide since the mid-19th century — and it’s still one of the most common inhaled sedatives used today. It’s fast-acting and it wears off quickly, making it an ideal sedation option for short or minor procedures.

What does laughing gas do?

Nitrous oxide slows down your nervous system and induces a sense of calm and euphoria. It reduces anxiety and helps you stay comfortable during medical or dental procedures. It doesn’t fully put you to sleep, so you’ll still be able to respond to your provider’s questions or instructions.

Despite its name, laughing gas might not make you laugh. (But then again, it could.) Everyone responds a little differently.

Nitrous oxide takes effect quickly. Within three to five minutes, you might feel:

* Calm.
* Relaxed.
* Happy.
* Giggly.
* Mildly euphoric.
* Light-headed.
* Tingling in your arms and legs.
* Heaviness, like you’re sinking deeper into the exam chair or table.

Who shouldn’t use nitrous oxide sedation?

Laughing gas is a safe medical and dental sedation option for most people, from children to adults. But it might not be right for kids under the age of 2 and those with:

* Certain respiratory conditions, like chronic obstructive pulmonary disease (COPD).
* Stuffy nose (nasal congestion).
* Vitamin B12 deficiency.
* Severe psychiatric conditions.

Ask your healthcare provider whether you’re a candidate for nitrous oxide sedation.

Treatment Details:

What should I expect if I’m getting laughing gas?

Your healthcare provider will talk with you and answer any questions before your procedure. They’ll ask you to sign a consent form so you can receive nitrous oxide.

When it’s time for your procedure, your provider will:

* Place a mask over your nose and mouth. (If you’re getting laughing gas at your dentist’s office, they’ll give you a smaller mask that only covers your nose.)
* Open a tank valve to allow nitrous oxide and oxygen to flow into your mask. (They’ll start with a very low dose to see how you respond.)
* Adjust the dosage until you feel the desired effects.
* Do your procedure. (In many cases, your provider will also give you local anesthesia before beginning. This is because nitrous oxide reduces pain but won’t totally eliminate it. So, it’s common to combine it with other forms of anesthesia.)
* Stop the flow of laughing gas once your procedure is over.
* Ask you to breathe in pure oxygen through your mask until you feel alert again.
* Remove the mask from your face.
* Monitor you for a few minutes before releasing you to go home.

It’s normal to feel a little nervous if you’ve never had laughing gas before. The good news is that you’ll be able to tell your provider if you develop undesirable side effects. If you start to feel dizzy or nauseous, your provider can simply adjust the dosage until it feels comfortable to you.

How long does laughing gas last?

The effects of nitrous oxide last until your provider turns off the gas flow. Once this happens, it takes about 5 to 10 minutes for the sedative to leave your system and for your headspace to return to normal. Due to the short-acting nature of nitrous oxide, you can drive shortly after your procedure.

Additional Information

Nitrous oxide (N2O), one of several oxides of nitrogen, is a colourless gas with pleasant, sweetish odour and taste, which when inhaled produces insensibility to pain preceded by mild hysteria, sometimes laughter. (Because inhalation of small amounts provides a brief euphoric effect and nitrous oxide is not illegal to possess, the substance has been used as a recreational drug.) Nitrous oxide was discovered by the English chemist Joseph Priestley in 1772; another English chemist, Humphry Davy, later named it and showed its physiological effect. A principal use of nitrous oxide is as an anesthetic in surgical operations of short duration; prolonged inhalation causes death. The gas is also used as a propellant in food aerosols. In automobile racing, nitrous oxide is injected into an engine’s air intake; the extra oxygen allows the engine to burn more fuel per stroke. It is prepared by the action of zinc on dilute nitric acid, by the action of hydroxylamine hydrochloride (NH2OH·HCl) on sodium nitrite (NaNO2), and, most commonly, by the decomposition of ammonium nitrate (NH4NO3).

nitrous-oxide-molecule-529553256-58a3b96b3df78c47588cbca7.jpg

Jai Ganesh · Dark Discussions at Cafe Infinity

Cold Quotes - II

1. Good is positive. Evil is merely privative, not absolute: it is like cold, which is the privation of heat. All evil is so much death or nonentity. Benevolence is absolute and real. So much benevolence as a man hath, so much life hath he. - Ralph Waldo Emerson

2. Continuous eloquence wearies. Grandeur must be abandoned to be appreciated. Continuity in everything is unpleasant. Cold is agreeable, that we may get warm. - Blaise Pascal

3. What is absurd and monstrous about war is that men who have no personal quarrel should be trained to murder one another in cold blood. - Aldous Huxley

4. When I was in the White House, I was confronted with the challenge of the Cold War. Both the Soviet Union and I had 30,000 nuclear weapons that could destroy the entire earth and I had to maintain the peace. - Jimmy Carter

5. As love without esteem is capricious and volatile; esteem without love is languid and cold. - Jonathan Swift

6. We are not interested in the fact that the brain has the consistency of cold porridge. - Alan Turing

7. If you take a reasonable amount of vitamin C regularly, the incidence of the common cold goes down. If you get a cold and start immediately, as soon as you start sneezing and sniffling, the cold just doesn't get going. - Linus Pauling

8. When I am working on a book or a story, I write every morning as soon after first light as possible. There is no one to disturb you, and it is cool or cold, and you come to your work and warm as you write. - Ernest Hemingway.

Jai Ganesh · Science HQ

Sublimation

Gist

Sublimation is the process where a substance transitions directly from a solid to a gas without becoming a liquid first. It is an endothermic process, meaning it requires energy, and can be seen in everyday examples like the disappearance of dry ice (CO2) and the evaporation of snow on a cold, dry day without melting. The opposite process, where a gas turns directly into a solid, is called deposition.

Sublimation is the process where a solid turns directly into a gas without becoming a liquid first. Common examples include dry ice (solid carbon dioxide), which turns into gas at room temperature, and mothballs (naphthalene), which slowly release a gas that repels moths.

Summary

Sublimation is the transition of a substance directly from the solid to the gas state, without passing through the liquid state. The verb form of sublimation is sublime, or less preferably, sublimate. Sublimate also refers to the product obtained by sublimation. The point at which sublimation occurs rapidly (for further details, see below) is called critical sublimation point, or simply sublimation point. Notable examples include sublimation of dry ice at room temperature and atmospheric pressure, and that of solid iodine with heating.

The reverse process of sublimation is deposition (also called desublimation), in which a substance passes directly from a gas to a solid phase, without passing through the liquid state.

Technically, all solids may sublime, though most sublime at extremely low rates that are hardly detectable under usual conditions. At normal pressures, most chemical compounds and elements possess three different states at different temperatures. In these cases, the transition from the solid to the gas state requires an intermediate liquid state. The pressure referred to is the partial pressure of the substance, not the total (e.g. atmospheric) pressure of the entire system. Thus, any solid can sublime if its vapour pressure is higher than the surrounding partial pressure of the same substance, and in some cases, sublimation occurs at an appreciable rate (e.g. water ice just below 0 °C).

For some substances, such as carbon and math, sublimation from solid state is much more achievable than evaporation from liquid state and it is difficult to obtain them as liquids. This is because the pressure of their triple point in its phase diagram (which corresponds to the lowest pressure at which the substance can exist as a liquid) is very high.

Sublimation is caused by the absorption of heat which provides enough energy for some molecules to overcome the attractive forces of their neighbors and escape into the vapor phase. Since the process requires additional energy, sublimation is an endothermic change. The enthalpy of sublimation (also called heat of sublimation) can be calculated by adding the enthalpy of fusion and the enthalpy of vaporization.

Details:

Definition of Sublimation

Sublimation is the process in which a solid directly changes into a gas without passing through the liquid phase. This process occurs when the temperature and pressure of the solid are raised to a point where the molecules have enough energy to break free from the intermolecular forces holding them in place and escape into the gas phase.

Sublimation Point

The sublimation point is the temperature and pressure at which the solid and gas phases of a substance are in equilibrium. At this point, the vapor pressure of the solid is equal to the pressure of the gas. The sublimation point is typically higher than the melting point of a substance.

Working Principle of Sublimation

Sublimation is the process in which a solid directly changes into a gas without passing through the liquid phase. This process occurs when the temperature and pressure of the solid are raised to a point where the molecules of the solid have enough energy to break free from the intermolecular forces holding them together and escape into the gas phase.

Sublimation is a process that occurs when a solid directly changes into a gas without passing through the liquid phase. This process has a number of applications, including freeze drying, desalination, purification, and 3D printing.

Characteristics of Sublimation

Sublimation is the process by which a solid directly changes into a gas without passing through the liquid phase. This process is the opposite of deposition, in which a gas directly changes into a solid. Sublimation is a physical change, meaning that the chemical composition of the substance does not change.

The following are some of the characteristics of sublimation:

* It occurs at a temperature and pressure below the triple point of the substance. The triple point is the temperature and pressure at which the three phases of a substance (solid, liquid, and gas) can coexist in equilibrium.
* It is a relatively slow process. This is because the molecules of a solid are more tightly packed together than the molecules of a gas, and it takes more energy to break these bonds.
* It is more common for substances with a high vapor pressure. Vapor pressure is the pressure exerted by the vapor of a substance when it is in equilibrium with its liquid or solid phase. Substances with a high vapor pressure are more likely to sublime because their molecules are more likely to escape from the solid or liquid phase.
* It can be used to purify substances. Sublimation can be used to separate a solid from impurities that have a lower vapor pressure. The solid is heated until it sublimes, and the impurities are left behind.
* It is used in a variety of applications. Sublimation is used in a variety of applications, including:

** Freeze-drying: Sublimation is used to remove water from food and other products.
** Dye sublimation printing: Sublimation is used to print images on fabrics and other materials.
** Vacuum coating: Sublimation is used to coat surfaces with a thin layer of metal or other material.

Examples of Sublimation

Some common examples of sublimation include:

* Dry ice (solid carbon dioxide) sublimes at atmospheric pressure. This is why dry ice “smokes” when it is exposed to air.
* Iodine sublimes at a temperature of 114°C (237°F). This is why iodine crystals disappear when they are heated.
* Naphthalene (mothballs) sublimes at a temperature of 80°C (176°F). This is why mothballs slowly disappear over time.

Sublimation is a unique and interesting physical change that has a variety of applications. By understanding the characteristics of sublimation, we can use this process to our advantage in a variety of ways.

Applications of Sublimation

Sublimation is the process of a solid turning directly into a gas without passing through the liquid phase. This process is used in a variety of applications, including:

Dye Sublimation Printing

Dye sublimation printing is a digital printing technology that uses heat to transfer dye onto materials such as paper, fabric, and plastic. This process is often used for creating high-quality prints on t-shirts, mugs, and other promotional items.

3D Printing

Sublimation is used in 3D printing to create objects from a digital file. In this process, a filament of plastic is heated until it melts and is then deposited layer by layer to create a three-dimensional object.

Food Processing

Sublimation is used in the food processing industry to remove moisture from food products. This process helps to preserve food and extend its shelf life.

Pharmaceuticals

Sublimation is used in the pharmaceutical industry to create drugs and other pharmaceutical products. This process allows for the precise control of the drug’s dosage and purity.

Electronics

Sublimation is used in the electronics industry to create thin films of metal and other materials. These films are used in a variety of electronic devices, such as transistors and capacitors.

Textile Printing

Sublimation printing is a digital printing technology that uses heat to transfer dye onto fabrics. This process is often used for creating high-quality prints on t-shirts, sportswear, and other textiles.

Other Applications

Sublimation is also used in a variety of other applications, including:

* Cosmetics: Sublimation is used to create makeup and other cosmetic products.
* Art: Sublimation is used to create prints on canvas, paper, and other materials.
* Industrial: Sublimation is used to create labels, decals, and other industrial products.

Sublimation is a versatile process that has a wide range of applications. It is a powerful tool that can be used to create high-quality products in a variety of industries.

Additional Information

Sublimation, in physics, is the conversion of a substance from the solid to the gaseous state without its becoming liquid. An example is the vaporization of frozen carbon dioxide (dry ice) at ordinary atmospheric pressure and temperature. The phenomenon is the result of vapour pressure and temperature relationships. Freeze-drying of food to preserve it involves sublimation of water from the food in a frozen state under high vacuum.

Sublimation is the process of changing a solid into a gas without passing through the liquid phase. To sublime a substance, a certain energy must be transferred to the substance via heat (q) or work (w). The energy needed to sublime a substance is particular to the substance's identity and temperature and must be sufficient to do all of the following:

* Excite the solid substance so that it reaches its maximum heat (energy) capacity (q) in the solid state.
* Sever all the intermolecular interactions holding the solid substance together
* Excite the unbonded atoms of the substance so that it reaches its minimum heat capacity in the gaseous state

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#10669. What does the term in Biology Endemism mean?

#10670. What does the term in Biology Endocrine gland mean?

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#5465. What does the adjective certifiable mean?

#5466. What does the adjective ceremonious mean?

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#2527. What does the medical term Cerebral circulation mean?

Jai Ganesh · Jokes

Q: Why don't Americans eat snails?
A: Because they like "Fast Food".
* * *
Q: What do you call a pig thief?
A: A hamburglar.
* * *
Q: How did the burger propose to a fry?
A: With an onion ring.
* * *
Q: Why did the french fry win the race?
A: Because it was fast food!
* * *
Q: Why is it called "Fast Food"?
A: It's called "fast" food because you're supposed to eat it really fast. Otherwise, you might actually taste it.
* * *

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#9806.

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#6301.

Jai Ganesh · Exercises

Hi,

2652.

Jai Ganesh · Dark Discussions at Cafe Infinity

2394) Richard Feynman

Gist:

Work

Following the establishment of the theory of relativity and quantum mechanics, an initial relativistic theory was formulated for the interaction between charged particles and electromagnetic fields. This needed to be reformulated, however. In 1948 in particular, Richard Feynman contributed to creating a new quantum electrodynamics by introducing Feynman diagrams: graphic representations of various interactions between different particles. These diagrams facilitate the calculation of interaction probabilities.

Summary

Richard Phillips Feynman (May 11, 1918 – February 15, 1988) was an American theoretical physicist. He is best known for his work in the path integral formulation of quantum mechanics, the theory of quantum electrodynamics, the physics of the superfluidity of supercooled liquid helium, and in particle physics, for which he proposed the parton model. For his contributions to the development of quantum electrodynamics, Feynman received the Nobel Prize in Physics in 1965 jointly with Julian Schwinger and Shin'ichirō Tomonaga.

Feynman developed a pictorial representation scheme for the mathematical expressions describing the behavior of subatomic particles, which later became known as Feynman diagrams and is widely used. During his lifetime, Feynman became one of the best-known scientists in the world. In a 1999 poll of 130 leading physicists worldwide by the British journal Physics World, he was ranked the seventh-greatest physicist of all time.

He assisted in the development of the atomic bomb during World War II and became known to the wider public in the 1980s as a member of the Rogers Commission, the panel that investigated the Space Shuttle Challenger disaster. Along with his work in theoretical physics, Feynman has been credited with having pioneered the field of quantum computing and introducing the concept of nanotechnology. He held the Richard C. Tolman professorship in theoretical physics at the California Institute of Technology.

Feynman was a keen popularizer of physics through both books and lectures, including a talk on top-down nanotechnology, "There's Plenty of Room at the Bottom" (1959) and the three-volumes of his undergraduate lectures, The Feynman Lectures on Physics (1961–1964). He delivered lectures for lay audiences, recorded in The Character of Physical Law (1965) and QED: The Strange Theory of Light and Matter (1985). Feynman also became known through his autobiographical books Surely You're Joking, Mr. Feynman! (1985) and What Do You Care What Other People Think? (1988), and books written about him such as Tuva or Bust! by Ralph Leighton and the biography Genius: The Life and Science of Richard Feynman by James Gleick.

Details

Richard Feynman (born May 11, 1918, New York, New York, U.S.—died February 15, 1988, Los Angeles, California) was an American theoretical physicist who was widely regarded as the most brilliant, influential, and iconoclastic figure in his field in the post-World War II era.

Feynman remade quantum electrodynamics—the theory of the interaction between light and matter—and thus altered the way science understands the nature of waves and particles. He was co-awarded the Nobel Prize for Physics in 1965 for this work, which tied together in an experimentally perfect package all the varied phenomena at work in light, radio, electricity, and magnetism. The other cowinners of the Nobel Prize, Julian S. Schwinger of the United States and Tomonaga Shin’ichirō of Japan, had independently created equivalent theories, but it was Feynman’s that proved the most original and far-reaching. The problem-solving tools that he invented—including pictorial representations of particle interactions known as Feynman diagrams—permeated many areas of theoretical physics in the second half of the 20th century.

Born in the Far Rockaway section of New York City, Feynman was the descendant of Russian and Polish Jews who had immigrated to the United States late in the 19th century. He studied physics at the Massachusetts Institute of Technology, where his undergraduate thesis (1939) proposed an original and enduring approach to calculating forces in molecules. Feynman received his doctorate at Princeton University in 1942. At Princeton, with his adviser, John Archibald Wheeler, he developed an approach to quantum mechanics governed by the principle of least action. This approach replaced the wave-oriented electromagnetic picture developed by James Clerk Maxwell with one based entirely on particle interactions mapped in space and time. In effect, Feynman’s method calculated the probabilities of all the possible paths a particle could take in going from one point to another.

During World War II Feynman was recruited to serve as a staff member of the U.S. atomic bomb project at Princeton University (1941–42) and then at the new secret laboratory at Los Alamos, New Mexico (1943–45). At Los Alamos he became the youngest group leader in the theoretical division of the Manhattan Project. With the head of that division, Hans Bethe, he devised the formula for predicting the energy yield of a nuclear explosive. Feynman also took charge of the project’s primitive computing effort, using a hybrid of new calculating machines and human workers to try to process the vast amounts of numerical computation required by the project. He observed the first detonation of an atomic bomb on July 16, 1945, near Alamogordo, New Mexico, and, though his initial reaction was euphoric, he later felt anxiety about the force he and his colleagues had helped unleash on the world.

At war’s end Feynman became an associate professor at Cornell University (1945–50) and returned to studying the fundamental issues of quantum electrodynamics. In the years that followed, his vision of particle interaction kept returning to the forefront of physics as scientists explored esoteric new domains at the subatomic level. In 1950 he became professor of theoretical physics at the California Institute of Technology (Caltech), where he remained the rest of his career.

Five particular achievements of Feynman stand out as crucial to the development of modern physics. First, and most important, is his work in correcting the inaccuracies of earlier formulations of quantum electrodynamics, the theory that explains the interactions between electromagnetic radiation (photons) and charged subatomic particles such as electrons and positrons (antielectrons). By 1948 Feynman completed this reconstruction of a large part of quantum mechanics and electrodynamics and resolved the meaningless results that the old quantum electrodynamic theory sometimes produced. Second, he introduced simple diagrams, now called Feynman diagrams, that are easily visualized graphic analogues of the complicated mathematical expressions needed to describe the behaviour of systems of interacting particles. This work greatly simplified some of the calculations used to observe and predict such interactions.

In the early 1950s Feynman provided a quantum-mechanical explanation for the Soviet physicist Lev D. Landau’s theory of superfluidity—i.e., the strange, frictionless behaviour of liquid helium at temperatures near absolute zero. In 1958 he and the American physicist Murray Gell-Mann devised a theory that accounted for most of the phenomena associated with the weak force, which is the force at work in radioactive decay. Their theory, which turns on the asymmetrical “handedness” of particle spin, proved particularly fruitful in modern particle physics. And finally, in 1968, while working with experimenters at the Stanford Linear Accelerator on the scattering of high-energy electrons by protons, Feynman invented a theory of “partons,” or hypothetical hard particles inside the nucleus of the atom, that helped lead to the modern understanding of quarks.

Feynman’s stature among physicists transcended the sum of even his sizable contributions to the field. His bold and colourful personality, unencumbered by false dignity or notions of excessive self-importance, seemed to announce: “Here is an unconventional mind.” He was a master calculator who could create a dramatic impression in a group of scientists by slashing through a difficult numerical problem. His purely intellectual reputation became a part of the scenery of modern science. Feynman diagrams, Feynman integrals, and Feynman rules joined Feynman stories in the everyday conversation of physicists. They would say of a promising young colleague, “He’s no Feynman, but….” His fellow physicists envied his flashes of inspiration and admired him for other qualities as well: a faith in nature’s simple truths, a skepticism about official wisdom, and an impatience with mediocrity.

Feynman’s lectures at Caltech evolved into the books Quantum Electrodynamics (1961) and The Theory of Fundamental Processes (1961). In 1961 he began reorganizing and teaching the introductory physics course at Caltech; the result, published as The Feynman Lectures on Physics, 3 vol. (1963–65), became a classic textbook. Feynman’s views on quantum mechanics, scientific method, the relations between science and religion, and the role of beauty and uncertainty in scientific knowledge are expressed in two models of science writing, again distilled from lectures: The Character of Physical Law (1965) and QED: The Strange Theory of Light and Matter (1985).

When Feynman died in 1988 after a long struggle with cancer, his reputation was still mainly confined to the scientific community; his was not a household name. Many Americans had seen him for the first time when, already ill, he served on the presidential commission that investigated the 1986 explosion of the space shuttle Challenger. He conducted a dramatic demonstration at a televised hearing, confronting an evasive NASA witness by dunking a piece of rubber seal in a glass of ice water to show how predictable the failure of the booster rocket’s rubber seal might have been on the freezing morning of Challenger’s launch. He added his own appendix to the commission’s report on the disaster, emphasizing the space agency’s failures of risk management.

He achieved a growing popular fame after his death, in part because of two autobiographical collections of anecdotes published in the years around his passing, “Surely You’re Joking, Mr. Feynman!”: Adventures of a Curious Character (1985) and “What Do You Care What Other People Think?”: Further Adventures of a Curious Character (1988), which irritated some of his colleagues by emphasizing his bongo playing and his patronage of a topless bar more than his technical accomplishments. Other popular books appeared posthumously, including Six Easy Pieces: Essentials of Physics Explained by Its Most Brilliant Teacher (1994) and Six Not-So-Easy Pieces: Einstein’s Relativity, Symmetry, and Space-Time (1997), and his life was celebrated in an opera (Feynman [2005], by Jack Vees), a graphic novel (Feynman [2011], by Jim Ottaviani and Leland Myrick), and a play (QED [2001], by Peter Parnell), the latter of which was commissioned by and starred Alan Alda.

Jai Ganesh · Jai Ganesh's Puzzles

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#10667. What does the term in Geography Cliffed coast mean?

#10668. What does the term in Geography Climate mean?

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#5463. What does the noun bottleful mean?

#5464. What does the adjective bouncy mean?

Jai Ganesh · This is Cool

2446) Constellation

Gist

A constellation is a group of stars that appear to form a pattern or picture in the night sky, named after animals, mythological figures, or objects. These patterns are created by drawing lines between stars from our perspective on Earth, though the stars themselves are often not physically close to each other and are simply in the same direction in the sky. There are 88 officially recognized constellations that astronomers use to map the sky and locate other celestial objects.

A constellation is a group of stars that forms a recognizable pattern in the night sky, often named after a mythological figure, animal, or object. These patterns are created by stars that may be very far apart in reality but appear to be close together from Earth's perspective. There are 88 official constellations recognized by the International Astronomical Union.

Summary

A constellation is an area on the celestial sphere in which a group of visible stars forms a perceived pattern or outline, typically representing an animal, mythological subject, or inanimate object.

The first constellations were likely defined in prehistory. People used them to relate stories of their beliefs, experiences, creation, and mythology. Different cultures and countries invented their own constellations, some of which lasted into the early 20th century before today's constellations were internationally recognized. The recognition of constellations has changed significantly over time. Many changed in size or shape. Some became popular, only to drop into obscurity. Some were limited to a single culture or nation. Naming constellations also helped astronomers and navigators identify stars more easily.

Twelve (or thirteen) ancient constellations belong to the zodiac (straddling the ecliptic, which the Sun, Moon, and planets all traverse). The origins of the zodiac remain historically uncertain; its astrological divisions became prominent c. 400 BC in Babylonian or Chaldean astronomy. Constellations appear in Western culture via Greece and are mentioned in the works of Hesiod, Eudoxus and Aratus. The traditional 48 constellations, consisting of the zodiac and 36 more (now 38, following the division of Argo Navis into three constellations) are listed by Ptolemy, a Greco-Roman astronomer from Alexandria, Egypt, in his Almagest. The formation of constellations was the subject of extensive mythology, most notably in the Metamorphoses of the Latin poet Ovid. Constellations in the far southern sky were added from the 15th century until the mid-18th century when European explorers began traveling to the Southern Hemisphere. Due to Roman and European transmission, each constellation has a Latin name.

In 1922, the International Astronomical Union (IAU) formally accepted the modern list of 88 constellations, and in 1928 adopted official constellation boundaries that together cover the entire celestial sphere. Any given point in a celestial coordinate system lies in one of the modern constellations. Some astronomical naming systems include the constellation where a given celestial object is found to convey its approximate location in the sky. The Flamsteed designation of a star, for example, consists of a number and the genitive form of the constellation's name.

Other star patterns or groups called asterisms are not constellations under the formal definition, but are also used by observers to navigate the night sky. Asterisms may be several stars within a constellation, or they may share stars with more than one constellation. Examples of asterisms include the teapot within the constellation Sagittarius, or the Big Dipper in the constellation of Ursa Major.

Details

A constellation, in astronomy, is any of certain groupings of stars that were imagined—at least by those who named them—to form conspicuous configurations of objects or creatures in the sky. Constellations are useful in assisting astronomers and navigators to locate certain stars.

From the earliest times the star groups known as constellations, the smaller groups (parts of constellations) known as asterisms, and also individual stars have received names connoting some meteorological phenomena or symbolizing religious or mythological beliefs. At one time it was held that the constellation names and myths were of Greek origin; this view has now been disproved, and an examination of the Hellenic myths associated with the stars and star groups in the light of the records revealed by the deciphering of Mesopotamian cuneiforms leads to the conclusion that in many, if not all, cases the Greek myth has a Mesopotamian parallel.

The earliest Greek work that purported to treat the constellations as constellations, of which there is certain knowledge, is the Phainomena of Eudoxus of Cnidus (c. 395–337 bce). The original is lost, but a versification by Aratus (c. 315–245 bce), a poet at the court of Antigonus II Gonatas, king of Macedonia, is extant, as is a commentary by Hipparchus (mid-2nd century bce).

Three hundred years after Hipparchus, the Alexandrian astronomer Ptolemy (100–170 ce) adopted a very similar scheme in his Uranometria, which appears in the seventh and eighth books of his Almagest, the catalog being styled the “accepted version.” The names and orientation of the 48 constellations therein adopted are, with but few exceptions, identical with those used at the present time.

The majority of the remaining 40 constellations that are now accepted were added by European astronomers in the 17th and 18th centuries. In the 20th century the delineation of precise boundaries for all the 88 constellations was undertaken by a committee of the International Astronomical Union. By 1930 it was possible to assign any star to a constellation.

Additional Information

A constellation is a grouping of stars which form a pattern in the sky that is traditionally named after its apparent form or identified with a mythological figure. Modern use of constellations includes identification of general locations for stars and galaxies (i.e. the Andromeda Galaxy). As for which constellation is the most popular, I think that depends upon who you are asking. If you mean which constellation is the one that most people know about, I think that Andromeda might be a good answer, given its famous inhabitant, the Andromeda Galaxy (otherwise known as Messier 31). Regarding how constellations are formed, the fact is that they are not formed by any physical process, nor do the stars that make up a constellation generally have any association with each other. Constellations are usually just chance alignments of stars which appear to be near each other from our vantage point. Finally, yes there is at least one famous red giant star in a constellation. The constellation Taurus contains the red giant star Aldebaran.

Jai Ganesh · This is Cool

Intergalactic space

Gist

Intergalactic space is the vast, extremely low-density region between galaxies. While it is nearly a vacuum, it contains the intergalactic medium (IGM), a tenuous, hot plasma of ionized hydrogen, along with occasional stars and dark matter, all organized in a cosmic filamentary structure. This gas, though sparse, makes up most of the matter in the universe, and is heated enough by events like galactic mergers and active galactic nuclei to be detectable through the X-rays and UV light it emits or absorbs.

Intergalactic space is the vast expanse between galaxies, which is extremely low in density and close to a perfect vacuum. While it may seem empty, it contains a very thin gas called the intergalactic medium (IGM), consisting mostly of hot, ionized hydrogen, along with heavier elements and a small number of stray stars. This matter is hot enough for electrons to be stripped from the hydrogen atoms.

Summary

The space between stars is known as interstellar space, and so the space between galaxies is called intergalactic space. These are the vast empty spaces that sit between galaxies. For example, if you wanted to travel from the Milky Way to the Andromeda galaxy, you would need to cross 2.5 million light-years of intergalactic space.

Intergalactic space is as close as you can get to an absolute vacuum. There's very little dust and debris, and scientists have calculated that there's probably only one hydrogen atom per cubic meter. The density of material is higher near galaxies, and lower in the midpoint between galaxies.

Galaxies are connected by a rarefied plasma that is thought to posses a cosmic filamentary structure, which is slightly denser than the average density of the Universe. This material is known as the intergalactic medium, and it's mostly made up of ionized hydrogen. Astronomers think that the intergalactic medium is about 10 to 100 times denser than the average density of the Universe.

This intergalactic medium can actually be seen by our telescopes here on Earth because it's heated up to tens of thousands, or even millions of degrees. This is hot enough for electrons to escape from hydrogen nuclei during collisions. We can detect the energy released from these collisions in the X-ray spectrum. NASA's Chandra X-Ray Observatory - a space telescope designed to search for X-rays - has detected vast clouds of hot intergalactic medium in regions where galaxies are colliding together in clusters.

Details

Intergalactic space is the physical space between galaxies. Generally free of dust and debris, intergalactic space is very close to a vacuum. The average density of the Universe is less than one atom per cubic meter. The density of the Universe, however, is clearly not uniform; it ranges from relatively high density in galaxies (including very high density in structures within galaxies, such as planets, stars, and black holes) to extremely rarefied conditions in vast voids that have lower density than the Universe's average.

Surrounding and stretching between galaxies, there is a rarefied gas that is thought to possess a cosmic filamentary structure and that is slightly denser than the average density in the Universe. This material is called the intergalactic medium (IGM) and is mostly ionized hydrogen (i.e. a plasma) consisting of equal numbers of electrons and protons. The IGM is thought to exist at a density of 10 to 100 times the average density of the Universe (10 to 100 hydrogen atoms per cubic meter). It reaches densities as high as 1000 times the average density of the Universe in rich clusters of galaxies.

The reason the IGM is thought to be mostly ionized gas is that its temperature is thought to be quite high by terrestrial standards (though some parts of it are only "warm" by astrophysical standards). As gas falls into the Intergalactic Medium from the voids, it heats up to temperatures of {10}^{5} to {10}^{7} K, which is too hot for hydrogen nuclei to retain their electrons. At these temperatures, it is called the Warm-Hot Intergalactic Medium (WHIM). Computer simulations indicate that on the order of half the atomic matter in the universe might exist in this warm-hot, rarefied state. When gas falls from the filamentary structures of the WHIM into the galaxy clusters at the intersections of the cosmic filaments, it can heat up even more, reaching temperatures of {10}^{8} K or more.

Additional Information

The vast voids between galaxies can stretch millions of light-years across and may appear empty. But these spaces actually contain more matter than the galaxies themselves.

"If you took a cubic meter, there would be less than one atom in it," Michael Shull, an astronomer at the University of Colorado Boulder, told Live Science. "But when you add it all up, it's somewhere between 50 and 80% of all the ordinary matter out there."

So, where did all this matter come from? And what's it up to?

The matter between galaxies — often called the intergalactic medium, or IGM for short — is mostly hot, ionized hydrogen (hydrogen that has lost its electron) with bits of heavier elements such as carbon, oxygen and silicon thrown in. While these elements typically don't glow bright enough to be seen directly, scientists know they're there because of the signature they leave on light that passes by.

In the 1960s, astronomers first discovered quasars — incredibly bright and active galaxies in the distant universe — and shortly thereafter, they noticed that the light from the quasars had missing pieces. These pieces had been absorbed by something in between the quasar and the astronomers' telescopes — this was the gas of the IGM. In the decades since, astronomers have discovered vast webs and filaments of gas and heavy elements that collectively contain more matter than all the galaxies combined. Some of this gas was likely left over from the Big Bang, but the heavier elements hint that some of it comes from old stardust, spewed out by galaxies.

While the most-remote regions of the IGM will be eternally isolated from neighboring galaxies as the universe expands, more "suburban" regions play an important role in galaxy life. The IGM under the influence of a galaxy's gravitational pull slowly accumulates onto the galaxy at a rate of about one solar mass (equal to the mass of the sun) per year, which is about the rate of star formation in the disk of the Milky Way.

"IGM is the gas that feeds star formation in galaxies," Shull said. "If we didn't still have gas falling in, being pulled in by gravity, star formation would slowly grind to a halt as the gas [in the galaxy] gets used up."

To probe the IGM, astronomers also have started looking at fast radio bursts that come from distant galaxies. Using both this technique and by examining quasar light, astronomers continue to study the characteristics of the IGM to determine its varying temperatures and densities.

"By measuring the temperature of the gas, you can get a clue as to its origins," Shull said. "It allows us to know how it got heated and how it got there."

Although gas is pervasive between galaxies, it isn't the only thing out there; astronomers have also found stars. Sometimes called intergalactic or rogue stars, these stars are thought to have been flung from their birth galaxies by black holes or collisions with other galaxies.

In fact, stars sailing the void might be fairly common. A 2012 study published in The Astrophysical Journal reported more than 650 of these stars at the edge of the Milky Way, and by some estimates, there could be trillions out there.

Jai Ganesh · Dark Discussions at Cafe Infinity

Cold Quotes - I

1. Every man has his secret sorrows which the world knows not; and often times we call a man cold when he is only sad. - Henry Wadsworth Longfellow

2. Every gun that is made, every warship launched, every rocket fired, signifies in the final sense a theft from those who hunger and are not fed, those who are cold and are not clothed. - Dwight D. Eisenhower

3. If... many influential people have failed to understand, or have just forgotten, what we were up against in the Cold War and how we overcame it, they are not going to be capable of securing, let alone enlarging, the gains that liberty has made. - Margaret Thatcher

4. My words in her mind: cold polished stones sinking through a quagmire. - James Joyce

5. I come from - I came from Wales, and it's a strong, butch society. We were in the war and all that. People didn't waste time feeling sorry for themselves. You had to get on with it. So my credo is get on with it. I don't waste time being soft. I'm not cold, but I don't like being, wasting my time with - life's too short. - Anthony Hopkins

6. A career is wonderful, but you can't curl up with it on a cold night. - Marilyn Monroe

7. I don't know why you use a fancy French word like detente when there's a good English phrase for it - cold war. - Golda Meir

8. Women tend to be more intuitive, or to admit to being intuitive, and maybe the hard science approach isn't so attractive. The way that science is taught is very cold. I would never have become a scientist if I had been taught like that. - Jane Goodall.

Jai Ganesh · Jai Ganesh's Puzzles

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#2526. What does the medical term Motor control mean?

Jai Ganesh · Jokes

Q: What did the butter say to the bread?
A: I'm on a roll!
* * *
Q: What do you call it when a mother and child bake bread together?
A: A labor of loaf.
* * *
Q: Why does everyone need bread and water?
A: Loaf makes the world go round.
* * *
Two Biscuits walking across Union Street, One gets hit by a bus.
The other one says, Oh Crumbs!
* * *
You know, when stuck in a jam, you're the bun I want to be with!
* * *

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

#9805.

Jai Ganesh · Jai Ganesh's Puzzles

Hi,

6300.

.

Jai Ganesh · Exercises

Hi,

2651.

Jai Ganesh · Dark Discussions at Cafe Infinity

2393) Julian Schwinger

Gist:

Work

Following the establishment of the theory of relativity and quantum mechanics, an initial relativistic theory was formulated for the interaction between charged particles and electromagnetic fields. However, partly because the electron’s magnetic moment proved to be somewhat larger than expected, the theory had to be reformulated. Julian Schwinger solved this problem in 1948 through “renormalization” and thereby contributed to a new quantum electrodynamics.

Summary

Julian Seymour Schwinger (born Feb. 12, 1918, New York, N.Y., U.S.—died July 16, 1994, Los Angeles, Calif.) was an American physicist and joint winner, with Richard P. Feynman and Tomonaga Shin’ichirō, of the Nobel Prize for Physics in 1965 for introducing new ideas and methods into quantum electrodynamics.

Schwinger was a child prodigy, publishing his first physics paper at age 16. He earned a bachelor’s degree (1937) and a doctorate (1939) from Columbia University in New York City, before engaging in postdoctoral studies at the University of California at Berkeley with physicist J. Robert Oppenheimer. Schwinger left Berkeley in the summer of 1941 to accept an instructorship at Purdue University, West Lafayette, Ind., and in 1943 he joined the Radiation Laboratory at the Massachusetts Institute of Technology, where many scientists had been assembled to help with wartime research on radar. In the fall of 1945 Schwinger accepted an appointment at Harvard University and in 1947 became one of the youngest full professors in the school’s history. From 1972 until his death, Schwinger was a professor in the physics department at the University of California at Los Angeles.

Schwinger was one of the participants at the meeting held in June 1947 on Shelter Island, Long Island, N.Y., at which reliable experimental data were presented that contradicted the predictions of the English theoretical physicist P.A.M. Dirac’s relativistic quantum theory of the electron. In particular, experimental data contradicted Dirac’s prediction that certain hydrogen electron stationary states were degenerate (i.e., had the same energy as certain other states) as well as Dirac’s prediction for the value of the magnetic moment of the electron. Schwinger made a quantum electrodynamical calculation that made use of the notions of mass and charge renormalization, which brought agreement between theory and experimental data. This was a crucial breakthrough that initiated a new era in quantum field theory. Richard Feynman and Tomonaga Shin’ichirō independently had carried out similar calculations, and in 1965 the three of them shared the Nobel Prize. Their work created a new and very successful quantum mechanical description of the interaction between electrically charged entities and the electromagnetic field that conformed with the principles of Albert Einstein’s special theory of relativity.

Schwinger’s work extended to almost every frontier of modern theoretical physics. He had a profound influence on physics both directly and through being the academic adviser for more than 70 doctoral students and more than 20 postdoctoral fellows, many of whom became the outstanding theorists of their generation.

Details

Julian Seymour Schwinger (February 12, 1918 – July 16, 1994) was a Nobel Prize-winning American theoretical physicist. He is best known for his work on quantum electrodynamics (QED), in particular for developing a relativistically invariant perturbation theory, and for renormalizing QED to one loop order. Schwinger was a physics professor at several universities.

Schwinger is recognized as an important physicist, responsible for much of modern quantum field theory, including a variational approach, and the equations of motion for quantum fields. He developed the first electroweak model, and the first example of confinement in 1+1 dimensions. He is responsible for the theory of multiple neutrinos, Schwinger terms, and the theory of the spin-3/2 field.

Biography:

Early life and career

Julian Seymour Schwinger was born in New York City, to Ashkenazi Jewish parents, Belle (née Rosenfeld) and Benjamin Schwinger, a garment manufacturer, who had emigrated from Poland to the United States. Both his father and his mother's parents were prosperous clothing manufacturers, although the family business declined after the Wall Street Crash of 1929. The family followed the Orthodox Jewish tradition. Julian's older brother Harold Schwinger was born in 1911, seven years before Julian who was born in 1918.

Schwinger was a precocious student. He attended the Townsend Harris High School from 1932 to 1934, a highly regarded high school for gifted students at the time. During high school, Julian had already started reading Physical Review papers by authors such as Paul Dirac in the library of the City College of New York, in whose campus Townsend Harris was then located.

In the fall of 1934, Schwinger entered the City College of New York as an undergraduate. CCNY automatically accepted all Townsend Harris graduates at the time, and both institutions offered free tuition. Due to his intense interest in physics and mathematics, Julian performed very well in those subjects despite often skipping classes and learning directly from books. On the other hand, his lack of interest for other topics such as English led to academic conflicts with teachers of those subjects.

After Julian had joined CCNY, his brother Harold, who had previously graduated from CCNY, asked his ex-classmate Lloyd Motz to "get to know [Julian]". Lloyd was a CCNY physics instructor and Ph.D. candidate at Columbia University at the time. Lloyd made the acquaintance, and soon recognized Julian's talent. Noticing Schwinger's academic problems, Lloyd decided to ask Isidor Isaac Rabi who he knew at Columbia for help. Rabi also immediately recognized Schwinger's capabilities on their first meeting, and then made arrangements to award Schwinger with a scholarship to study at Columbia. At first Julian's bad grades in some subjects at CCNY prevented the scholarship award. But Rabi persisted and showed an unpublished paper on quantum electrodynamics written by Schwinger to Hans Bethe, who happened to be passing by New York. Bethe's approval of the paper and his reputation in that domain were then enough to secure the scholarship for Julian, who then transferred to Columbia. His academic situation at Columbia was much better than at CCNY. He was accepted into the Phi Beta Kappa society and received his B.A. in 1936.

During Schwinger's graduate studies, Rabi felt that it would be good for Julian to visit other institutions around the country, and Julian was awarded a travelling fellowship for the year 37/38 which he spent at working with Gregory Breit and Eugene Wigner. During this time, Schwinger, who previously had already had the habit of working until late at night, went further and made the day/night switch more complete, working at night and sleeping during the day, a habit he would carry throughout his career. Schwinger later commented that this switch was in part a way to retain greater intellectual independence and avoid being "dominated" by Breit and Wigner by simply reducing the duration of contact with them by working different hours.

Schwinger obtained his PhD overseen by Rabi in 1939 at the age of 21.

During the fall of 1939 Schwinger started working at the University of California, Berkeley under J. Robert Oppenheimer, where he stayed for two years as an NRC fellow.

Career

After having worked with Oppenheimer, Schwinger's first regular academic appointment was at Purdue University in 1941. While on leave from Purdue, he worked at the MIT Radiation Laboratory instead of at the Los Alamos National Laboratory during World War II. He provided theoretical support for the development of radar. After the war, Schwinger left Purdue for Harvard University, where he taught from 1945 to 1974. In 1966 he became the Eugene Higgins professor of physics at Harvard.

Schwinger developed an affinity for Green's functions from his radar work, and he used these methods to formulate quantum field theory in terms of local Green's functions in a relativistically invariant way. This allowed him to calculate unambiguously the first corrections to the electron magnetic moment in quantum electrodynamics. Earlier non-covariant work had arrived at infinite answers, but the extra symmetry in his methods allowed Schwinger to isolate the correct finite corrections.

Schwinger developed renormalization, formulating quantum electrodynamics unambiguously to one-loop order.

In the same era, he introduced non-perturbative methods into quantum field theory, by calculating the rate at which electron–positron pairs are created by tunneling in an electric field, a process now known as the "Schwinger effect." This effect could not be seen in any finite order in perturbation theory.

Schwinger's foundational work on quantum field theory constructed the modern framework of field correlation functions and their equations of motion. His approach started with a quantum action and allowed bosons and fermions to be treated equally for the first time, using a differential form of Grassman integration. He gave elegant proofs for the spin-statistics theorem and the CPT theorem, and noted that the field algebra led to anomalous Schwinger terms in various classical identities, because of short distance singularities. These were foundational results in field theory, instrumental for the proper understanding of anomalies.

In other notable early work, Rarita and Schwinger formulated the abstract Pauli and Fierz theory of the spin-3/2 field in a concrete form, as a vector of Dirac spinors, Rarita–Schwinger equation. In order for the spin-3/2 field to interact consistently, some form of supersymmetry is required, and Schwinger later regretted that he had not followed up on this work far enough to discover supersymmetry.

Schwinger discovered that neutrinos come in multiple varieties, one for the electron and one for the muon. Nowadays there are known to be three light neutrinos; the third is the partner of the tau lepton.

In the 1960s, Schwinger formulated and analyzed what is now known as the Schwinger model, quantum electrodynamics in one space and one time dimension, the first example of a confining theory.

Having supervised 73 doctoral dissertations, Schwinger is known as one of the most prolific graduate advisors in physics. Four of his students won Nobel prizes: Roy Glauber, Benjamin Roy Mottelson, Sheldon Glashow and Walter Kohn (in chemistry).

Schwinger had a mixed relationship with his colleagues, because he always pursued independent research, different from mainstream fashion. In particular, Schwinger developed the source theory, a phenomenological theory for the physics of elementary particles, which is a predecessor of the modern effective field theory. It treats quantum fields as long-distance phenomena and uses auxiliary 'sources' that resemble currents in classical field theories. The source theory is a mathematically consistent field theory with clearly derived phenomenological results. The criticisms by his Harvard colleagues led Schwinger to leave the faculty in 1972 for UCLA. It is a story widely told that Steven Weinberg, who inherited Schwinger's paneled office in Lyman Laboratory, there found a pair of old shoes, with the implied message, "think you can fill these?". Based on Schwinger's source theory, Weinberg set the underpinnings of the effective field theory, that is more appreciated among physicists. In spite of the shoes incident, Weinberg gave the credit to Schwinger for the inspiration.

At UCLA, and for the rest of his career, Schwinger continued to develop the source theory and its various applications. After 1989 Schwinger took a keen interest in the non-mainstream research of cold fusion. He wrote eight theory papers about it. He resigned from the American Physical Society after their refusal to publish his papers. He felt that cold fusion research was being suppressed and academic freedom violated. He wrote, "The pressure for conformity is enormous. I have experienced it in editors' rejection of submitted papers, based on venomous criticism of anonymous referees. The replacement of impartial reviewing by censorship will be the death of science."

In his last publications, Schwinger proposed a theory of sonoluminescence as a long-distance quantum radiative phenomenon associated not with atoms, but with fast-moving surfaces in the collapsing bubble, where there are discontinuities in the dielectric constant. The mechanism of sonoluminescence now supported by experiments focuses on superheated gas inside the bubble as the source of the light.

Schwinger was jointly awarded the Nobel Prize in Physics in 1965 for his work on quantum electrodynamics (QED), along with Richard Feynman and Shin'ichirō Tomonaga. Schwinger's awards and honors were numerous even before his Nobel win. They include the first Albert Einstein Award (1951), the U.S. National Medal of Science (1964), honorary D.Sc. degrees from Purdue University (1961) and Harvard University (1962), and the Nature of Light Award of the U.S. National Academy of Sciences (1949). In 1987, Schwinger received the Golden Plate Award of the American Academy of Achievement.

Jai Ganesh · This is Cool

2445) Nitric Oxide

Gist

Nitric oxide (NO) is a colorless gas with the chemical formula NO, which acts as an important signaling molecule in the human body and is also an air pollutant. In the body, it relaxes blood vessels to improve blood flow, aids in neurotransmission, and plays a role in immune responses and other cellular processes. Industrially, it is a source of pollution and can be produced by high temperatures or chemical reactions.

Nitric oxide is used for medical purposes, such as treating respiratory failure in newborns and helping with erectile dysfunction, and is also used in industrial applications. In the body, it's crucial for vasodilation (widening blood vessels), which helps regulate blood flow, blood pressure, and other physiological processes.

Summary

Nitric oxide (nitrogen oxide, nitrogen monooxide, or nitrogen monoxide) is a colorless gas with the formula NO. It is one of the principal oxides of nitrogen. Nitric oxide is a free radical: it has an unpaired electron, which is sometimes denoted by a dot in its chemical formula (•N=O or •NO). Nitric oxide is also a heteronuclear diatomic molecule, a class of molecules whose study spawned early modern theories of chemical bonding.

An important intermediate in industrial chemistry, nitric oxide forms in combustion systems and can be generated by lightning in thunderstorms. In mammals, including humans, nitric oxide is a signaling molecule in many physiological and pathological processes. It was proclaimed the "Molecule of the Year" in 1992. The 1998 Nobel Prize in Physiology or Medicine was awarded for discovering nitric oxide's role as a cardiovascular signalling molecule. Its impact extends beyond biology, with applications in medicine, such as the development of sildenafil (Viagra), and in industry, including semiconductor manufacturing.

Nitric oxide should not be confused with nitrogen dioxide (NO2), a brown gas and major air pollutant, or with nitrous oxide (N2O), an anesthetic gas.

Details

Nitric oxide (NO) is a colorless, odorless gas molecule that plays a crucial role in various physiological processes within the human body. It was first discovered in the 18th century, but its significance in biological systems wasn’t fully understood until the late 20th century.

In the body, NO acts as a signaling molecule, participating in the regulation of numerous functions, including vasodilation (the widening of blood vessels), neurotransmission, immune response, and the regulation of inflammation. One of its most notable roles is in the regulation of blood pressure, where it helps to relax and widen blood vessels, thereby improving blood flow.

What is nitric oxide?

Nitric oxide (NO) is a molecule composed of one nitrogen atom and one oxygen atom. It is a colorless and odorless gas at room temperature. It is a crucial signaling molecule in the body involved in various physiological processes.

One of its primary roles is as a vasodilator, meaning it relaxes and widens blood vessels, leading to increased blood flow. This function is vital for regulating blood pressure and delivering oxygen and nutrients to tissues throughout the body.

Nitric oxide also acts as a neurotransmitter. Additionally, it plays a role in the immune system, helping to combat pathogens and regulate inflammation.

Synthesis

NO is synthesized in the body through a process involving the conversion of the amino acid arginine into nitric oxide and citrulline. This synthesis is catalyzed by a family of enzymes called nitric oxide synthases (NOS).

There are three isoforms of nitric oxide synthase:

* Endothelial NOS (eNOS): Found primarily in endothelial cells lining blood vessels, eNOS produces nitric oxide in response to various physiological stimuli, such as shear stress and certain hormones.
* Neuronal NOS (nNOS or NOS1): Present in neurons of the central and peripheral nervous systems, nNOS is involved in neurotransmission and neuromodulation, synthesizing nitric oxide in response to calcium influx during neuronal activation.
* Inducible NOS (iNOS or NOS2): Induced in response to inflammatory stimuli, such as cytokines and bacterial endotoxins, iNOS produces large amounts of NO for immune defense mechanisms and inflammation regulation.

The synthesis of nitric oxide by nitric oxide synthases involves several steps:

* L-arginine binding: The enzyme binds the substrate L-arginine, along with other cofactors such as tetrahydrobiopterin (BH4) and oxygen (O2).
* Conversion to L-citrulline and nitric oxide: Through a series of enzymatic reactions involving the cofactors and molecular oxygen, nitric oxide synthase catalyzes the conversion of L-arginine into nitric oxide and L-citrulline.
* Release of nitric oxide: Once synthesized, NO is released from the enzyme and diffuses freely across cell membranes to exert its physiological effects.

Functions

NO is a versatile molecule with numerous functions in the human body. Some of its key functions include:

* Vasodilation: NO acts as a potent vasodilator, meaning it relaxes and widens blood vessels. This helps to improve blood flow and regulate blood pressure.
* Neurotransmission: Serves as a signaling molecule in the nervous system, facilitating communication between nerve cells (neurons). It plays a role in neurotransmission, synaptic plasticity, and other neurological processes.
* Immune response: It is involved in the immune system’s defense against pathogens. It helps to regulate inflammation and can be produced by immune cells to kill invading bacteria, viruses, and parasites.
* Regulation of platelet function: Helps to regulate platelet aggregation, which is important for preventing excessive blood clotting and maintaining cardiovascular health.
* Smooth muscle relaxation: It relaxes smooth muscles found in various organs and tissues, including the gastrointestinal tract, airways, and urinary bladder. This relaxation helps to regulate processes such as digestion, breathing, and urination.
* Angiogenesis: It plays a role in angiogenesis, the formation of new blood vessels from existing ones. This process is important for tissue repair, wound healing, and the growth of tumors.
* Penile erection: It is a key mediator of penile erection. It stimulates the relaxation of smooth muscle cells in the erectile tissue of the male reproductive organ, leading to increased blood flow and the attainment of an erection.
* Regulation of mitochondrial function: It can modulate mitochondrial respiration and energy production within cells, influencing cellular metabolism and overall energy balance.
* Regulation of gene expression: It can also act as a signaling molecule within cells to regulate gene expression and various cellular processes, including cell proliferation, differentiation, and apoptosis (programmed cell death).

NO rich foods

There are several foods that are naturally rich in nitrates, which can be converted into NO in the body. These foods include:

* Leafy greens: Spinach, kale, arugula, and other leafy greens are high in nitrates.
* Celery: Celery is another vegetable that contains nitrates and can contribute to nitric oxide production.
* Garlic: Garlic contains compounds that can stimulate nitric oxide production and promote cardiovascular health.
* Citrus fruits: Oranges, lemons, and other citrus fruits are rich in vitamin C, which can help support nitric oxide production.
* Pomegranate: Pomegranate juice and seeds contain antioxidants and nitrates that may support NO levels and cardiovascular health.
* Watermelon: Watermelon contains an amino acid called citrulline, which can be converted into arginine, a precursor to nitric oxide.
* Nitrates in Vegetables: Nitrates are compounds found in certain vegetables that can be converted into NO in the body. Examples of nitrate-rich vegetables include spinach, arugula, kale, beetroot, and lettuce.
* Beets and Beetroot Juice: Beets and beetroot juice are well-known for their high nitrate content, which can be converted into nitric oxide.
* Dark Chocolate: Dark chocolate contains flavonoids, which have been shown to support nitric oxide production and cardiovascular health.

Interaction with other drugs

NO can interact with various drugs due to its role as a signaling molecule in many physiological processes. Some interactions include:

* Blood pressure medications: NO donors or drugs that increase NO levels, such as nitroglycerin or other nitrate medications, can enhance the effects of blood pressure-lowering medications like antihypertensives. This interaction can lead to excessive hypotension (low blood pressure).
* Erectile dysfunction drugs: Drugs used to treat erectile dysfunction, such as sildenafil (Viagra), tadalafil (Cialis), and vardenafil (Levitra), work by enhancing the effects of NO, leading to vasodilation and improved blood flow. Combining these drugs with other NO donors or medications that increase NO levels can potentiate their effects and may cause a dangerous drop in blood pressure.
* Anticoagulants and antiplatelet drugs: NO inhibits platelet aggregation and can increase bleeding risk. Combining NO donors or medications that increase NO levels with anticoagulants (e.g., warfarin, heparin) or antiplatelet drugs (e.g., aspirin, clopidogrel) may further enhance the risk of bleeding.
* Drugs affecting nitric oxide synthesis: Medications that affect the synthesis of NO, such as inhibitors of NO synthase (NOS), may interact with drugs that rely on NO signaling for their effects. These interactions can affect cardiovascular function, neurotransmission, and immune response.
* Alpha-blockers: Alpha-blockers, used to treat conditions like benign prostatic hyperplasia (BPH) and hypertension, can interact with NO donors or drugs that increase NO levels, leading to additive effects on blood pressure lowering.
* Drugs affecting cytochrome P450 enzymes: Some drugs can affect the activity of cytochrome P450 enzymes, which are involved in the metabolism of NO donors and other drugs. Interactions with these drugs can alter the metabolism and effectiveness of medications that affect NO levels.

Side effects

While NO is essential for various physiological functions in the body, including vasodilation and neurotransmission, excessive intake or production of nitric oxide can lead to potential complications. Here are some of the possible complications associated with taking excessive amounts of nitric oxide:

* Hypotension: Excessive nitric oxide can cause a significant drop in blood pressure (hypotension). This can lead to symptoms such as dizziness, lightheadedness, fainting, and in severe cases, shock.
* Headaches: Increased levels of nitric oxide can cause headaches, which may range from mild to severe and can be debilitating for some individuals.
* Increased bleeding risk: NO can inhibit platelet aggregation and contribute to increased bleeding risk. Excessive nitric oxide production may lead to prolonged bleeding and difficulty in clot formation.
* Worsening of respiratory conditions: In individuals with certain respiratory conditions such as asthma, excessive nitric oxide production can exacerbate symptoms by causing airway dilation and inflammation.
* Nitric oxide toxicity: In rare cases, excessive exposure to NO gas, particularly in industrial or occupational settings, can lead to toxicity, causing respiratory distress, lung damage, and even death.
* Formation of reactive nitrogen species: Excessive nitric oxide can react with other molecules in the body to form reactive nitrogen species, such as peroxynitrite, which can contribute to oxidative stress, tissue damage, and inflammation.

Additional Information

Nitric oxide (NO) is a colourless toxic gas that is formed by the oxidation of nitrogen. Nitric oxide performs important chemical signaling functions in humans and other animals and has various applications in medicine. It has few industrial applications. It is a serious air pollutant generated by automotive engines and thermal power plants.

Nitric oxide is formed from nitrogen and oxygen by the action of electric sparks or high temperatures or, more conveniently, by the action of dilute nitric acid upon copper or mercury. It was first prepared about 1620 by the Belgian scientist Jan Baptista van Helmont, and it was first studied in 1772 by the English chemist Joseph Priestley, who called it “nitrous air.”

Nitric oxide liquefies at −151.8 °C (−241.2 °F) and solidifies at −163.6 °C (−262.5 °F); both the liquid and the solid are blue in colour. The gas is almost insoluble in water, but it dissolves rapidly in a slightly alkaline solution of sodium sulfite, forming the compound sodium dinitrososulfite, Na2(NO)2SO3. It reacts rapidly with oxygen to form nitrogen dioxide, NO2. Nitric oxide is a relatively unstable, diatomic molecule that possesses a free radical (i.e., an unpaired electron). The molecule can gain or lose one electron to form the ions NO− or NO+.

In the chemical industry, nitric oxide is an intermediate compound formed during the oxidation of ammonia to nitric acid. An industrial procedure for the manufacture of hydroxylamine is based on the reaction of nitric oxide with hydrogen in the presence of a catalyst. The formation of nitric oxide from nitric acid and mercury is applied in a volumetric method of analysis for nitric acid or its salts.

Though it is a toxic gas at high concentrations, nitric oxide functions as an important signaling molecule in animals. It acts as a messenger molecule, transmitting signals to cells in the cardiovascular, nervous, and immune systems. The nitric oxide molecule’s possession of a free radical makes it much more reactive than other signaling molecules, and its small size enables it to diffuse through cell membranes and walls to perform a range of signaling functions in various bodily systems. The body synthesizes nitric oxide from the amino acid L-arginine by means of the enzyme nitric oxide synthase.

The main site of the molecule’s synthesis is the inner layer of blood vessels, the endothelium, though the molecule is also produced by other types of cells. From the endothelium, nitric oxide diffuses to underlying smooth muscle cells and causes them to relax. This relaxation causes the walls of blood vessels to dilate, or widen, which in turn increases blood flow through the vessels and decreases blood pressure. Nitric oxide’s role in dilating blood vessels makes it an important controller of blood pressure. Nitric oxide is also produced by neurons (nerve cells) and is used by the nervous system as a neurotransmitter to regulate functions ranging from digestion to blood flow to memory and vision. In the immune system, nitric oxide is produced by macrophages, which are a type of leukocyte (white blood cell) that engulfs bacteria and other foreign particles that have invaded the body. The nitric oxide released by macrophages kills bacteria, other parasites, and tumour cells by disrupting their metabolism.

Nitric oxide’s role in regulating blood flow and pressure is used by modern medicine in several ways. The drug nitroglycerin has been used since the late 19th century to relieve the condition known as angina pectoris, which is caused by an insufficient supply of blood to the heart muscle. Nitroglycerin was long known to achieve its therapeutic effect by dilating the coronary arteries (thereby increasing the flow of blood to the heart), but why it did so remained unknown until the late 1980s, when researchers realized that the drug serves to replenish the body’s supply of nitric oxide, more of which is then available to relax, and thereby widen, the coronary blood vessels.

Nitric oxide is an important component of the air pollution generated by automotive engines and thermal power-generating plants. When a mixture of air and hydrocarbon fuel is burned in an internal-combustion engine or a power plant, the ordinarily inert nitrogen in the air combines with oxygen at very high temperatures to form nitric oxide. The nitric oxide and hydrocarbon vapours emitted by automotive exhausts and power-plant smokestacks undergo complex photochemical reactions in the lower atmosphere to form various secondary pollutants called photochemical oxidants, which make up photochemical smog. Nitric oxide combines with water vapour in the atmosphere to form nitric acid, which is one of the components of acid rain. Heightened levels of atmospheric nitric oxide resulting from industrial activity were also one of the causes of gradual depletion of the ozone layer in the upper atmosphere. Sunlight causes nitric oxide to react chemically with ozone (O3), thereby converting the ozone to molecular oxygen (O2).

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Jai Ganesh · Dark Discussions at Cafe Infinity

Coin Quotes - I

1. All the perplexities, confusion and distress in America arise, not from defects in their Constitution or Confederation, not from want of honor or virtue, so much as from the downright ignorance of the nature of coin, credit and circulation. - John Adams

2. Peace and justice are two sides of the same coin. - Dwight D. Eisenhower

3. Leadership is the other side of the coin of loneliness, and he who is a leader must always act alone. And acting alone, accept everything alone. - Ferdinand Marcos

4. Silver and gold are not the only coin; virtue too passes current all over the world. - Euripides

5. If you call yourself a leader, then you have to be decisive. If you're decisive, then you have the chance to be a leader. These are two sides to the same coin. - Narendra Modi

6. German and European unification are two sides of the same coin. - Helmut Kohl

7. When the machine had been fastened with a wire to the track, so that it could not start until released by the operator, and the motor had been run to make sure that it was in condition, we tossed a coin to decide who should have the first trial. Wilbur won. - Orville Wright

8. I said, yet again, for Germany, Europe is not only indispensable, it is part and parcel of our identity. We've always said German unity, European unity and integration, that's two parts of one and the same coin. But we want, obviously, to boost our competitiveness. - Angela Merkel.

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