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so last time, tetra was being enlightened by mc - kun about definitions. this actually arises from mc - kun using prime numbers as a motivating example. primes are megas important in mathematics and even more important today. the entire branch of mathematics called number theory is all about studying the properties of prime numbers. they ’ re so useful that we ’ ve done stuff like extend the notion of prime elements to algebraic structures called rings or apply analytic techniques to learn more about them, but we ’ ll stick with elementary number theory for now. now, for hundreds of years, we ’ d been studying number theory only because it ’ s cool and mathematicians love prime numbers. last time, i mentioned some examples of math preceding useful applications. well, number theory is a really good example of that, because in the 70s, we found a use for it, which is its main use today, in cryptography. there have been some new techniques using some algebra as well, but for the most part, modern cryptography relies on the hardness of factoring primes. neat! okay, so we ’ re back to the original question that mc - kun tries to get tetra to answer, which is, what is a prime number? definition. an integer $ p $ is prime if and only if $ p \ geq 2 $ and the only positive divisors of $ p $ are 1 and itself. mc - kun explains that the motivation for excluding 1 from the definition of a prime number is because we want to be able to say that we can write every number as a unique product of prime numbers. this is very useful, because now we know we can break down every number like this and we can tell them apart because they ’ re guaranteed to have a unique representation. this is called unique prime factorization. theorem. let $ a > 0 $ be an integer. then we can write $ a = p _ 1p _ 2 \ cdots p _ k $ for some primes $ p _ 1, \ dots, p _ k $. this representation is unique up to changing the order of terms. we can show this by induction on $ a $. we ’ ve got $ a = 2 $ so that ’ s pretty obvious. so let ’ s say that every integer $ k \ lt a $ can be decomposed like this and suppose we can ’ t decompose $ a $ into prime numbers, assuming $ a $ itself isn ’ t already a prime since it would just be its own
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common divisor of the two numbers, which is just the largest number that divides both of them. we ’ ll denote this by $ \ gcd ( a, b ) $. so since $ p _ i $ is a factor of $ n $, we ’ ve got $ \ gcd ( n, p _ i ) = p _ i $. but then that gives us $ p _ i = \ gcd ( n, p _ i ) = \ gcd ( p _ i, 1 ) = 1 $ by a lemma that says that for $ a = qb + r $, we have $ \ gcd ( a, b ) = \ gcd ( b, r ) $. this means that we have $ p _ i = 1 $, which is a contradiction, since 1 isn ’ t a prime number, and so i guess there are actually infinitely many primes. so the nice thing is that we won ’ t run out of prime numbers anytime soon, which is very useful because as we get more and more computing power, we ’ ll have to increase the size of the keys we use in our cryptosystems. luckily, because factoring is so hard, we don ’ t need to increase that size very much before we ’ re safe for a while. or at least until we develop practical quantum computers.
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is defined as heading in the opposite direction of the flow of electrons, thus we get an electric current in which the p - type silicon is an anode and the n - type silicon a cathode. mechanism by which application of a current produces light since exposing a pn junction diode to light produces an electric current just like a solar battery, the reverse should also hold true, i. e. applying an external electric current in the opposite direction should cause light to emit from the pn junction. this phenomenon does in fact occur. making the n - type silicon the cathode and the p - type silicon the anode produces light. this is known as a light - emitting diode ( led ). however, light emission from such rudimentary leds is inefficient, making them ill suited for practical applications. only after creating pn junctions using semiconductor materials made of the compounds gallium arsenide, gallium phosphide, and gallium arsenide phosphide did leds become practical. semiconductor lasers also use pn junctions the semiconductor laser is another technology that uses pn junctions. creating a pn junction within a semiconductor brings about " population inversion " by means of the electrons that flow into n - type silicon and the electron holes in p - type silicon. by skillfully placing two perpendicular mirrors with cleavage planes of semiconductor crystal on either end of the pn junction, we can intensify light by making it bounce back and forth between the planes, thus producing a laser beam comprising light with uniform phase and direction. such semiconductor lasers are also called laser diodes. these devices are only about 300 micrometers square and 80 micrometers thick. laser diodes using gallium arsenide phosphide, which emit a laser beam with a wavelength of 700 nanometers, are being mass produced for use in compact disc ( cd ) players and laser beam printers.
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1. the unit of frequency. 4. ( zoology ) lacking a tail or taillike appendage. 12. piece of solid food for dipping in a liquid. 15. resinlike substance secreted by certain lac insects. 16. ornamental objects of no great value. 17. any of various primates with short tails or no tail at all. 18. to make a mistake or be incorrect. 19. third month of the revolutionary calendar ( november and december ). 20. god of the earth. 21. ( anatomy ) of or relating to the fauces. 23. ( norse mythology ) one of the aesir known for his beauty and skill with bow and skis. 24. type genus of the phocidae. 26. the jewish rite of circumcision performed on a male child on the eighth day of his life. 27. a state in new england. 29. become imbued. 31. a state in east central united states. 32. port city of denmark in eastern jutland. 36. a white soft metallic element that tarnishes readily. 37. a soft white precious univalent metallic element having the highest electrical and thermal conductivity of any metal. 39. a rare silvery ( usually trivalent ) metallic element. 41. an island republic on nauru island. 42. a family of birds of the suborder oscines. 46. a ballplayer who is batting. 48. an informal term for a father. 49. the seventh month of the moslem calendar. 51. any of various young herrings ( other than brislings ) canned as sardines in norway. 52. jordan ' s port. 54. a city in northwestern turkey. 55. small cubes with 1 to 6 spots on the faces. 56. fallow deer. 60. a hard brittle blue - white multivalent metallic element. 61. a loloish language. 62. a fraudulent business scheme. 64. indonesian statesman who obtained the independence of indonesia from the netherlands in 1949 and served as president until ousted by suharto in a coup d ' etat ( 1901 - 1970 ). 69. ( akkadian ) god of wisdom. 71. small terrestrial lizard of warm regions of the old world. 74. title for a civil or military leader ( especially in turkey ). 75. ( used especially of glances ) directed to one side with or as if with doubt or suspicion or envy. 78. toward the mouth or oral region. 79. an advanced law
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tim turner, the reliability center business development manager at the college of nanoscale science and engineering ( cnse ), albany, ny, blogs about the potential of resistive memory and the reliability challenges the must be overcome. resistive memory, rram or memristors is a hot topic right now. rram has the potential for single digit nano parameters ( speed as fast as 1 ns, area per bit as small as 5 square nm ) and is non - volatile. the technology is based on the formation of a small conductive filament inside an insulator. the filament is formed the first time using a high voltage. after that, set or reset transformation ( conductive to non - conductive or visa versa ) is accomplished by moving one or a few atoms an atomic scale distance. this can be done with a low voltage ( less than a volt ). this small movement gives a repeatable set or reset that can withstand many cycles. conduction in the filament appears to be due to oxygen vacancies existing in a percolation path through the insulator. a small electric field in the reverse direction causes the migration of these oxygen vacancies in a mechanism similar to electromigration of al or cu atoms in a metal line. momentum exchange between electrons and the vacancies appears to be the driving force. the vacancies do not have to move far to open the small filament. an oxygen vacancy moves an atomic scale distance and the tiny filament opens, allowing an insulator to exist between points in the filament. forcing a forward voltage can move the oxygen vacancy back into the area where the filament is conductive. this small movement can give a 100x change in the conduction through the dielectric. this is the state change that can be interpreted as the digital signal stored on the memory cell. the material set used for rram is cmos compatible. rram cells have been made out of cu / hfox, al / alox / pt, tin / alox / pt or even al / alox / cnt ( carbon nano tubes ). most of the work reported to date has been on arrays where the cell is similar to a dram, using one transistor and one capacitor. the rram cell starts with a capacitor, then forms the filament in the capacitor dielectric. the advantage this technology has is the smaller size of the capacitor. there is
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##een and brattain ’ s invention of the bipolar, point - contact transistor took many unexpected twists and turns. shockley did not put all his eggs in the field - effect basket. not to be outdone by bardeen and brattain, shockley secretly worked on a different bipolar device. within a short time, his patent for the bipolar junction transistor had wiped out all commercial interest in the point - contact transistor. shockley remained committed to the value of his field - effect theory, but was unable to make a go of it. more than 15 years of material technology advances would be needed before the first practical fet appeared. today, 75 years after lilienfeld ’ s work, metal - oxide silicon ( mos ) transistors, which are built around field - effect principles, dominate semiconductor electronics. lilienfield acknowledged as pioneer in an address to the american institute of physics in 1988, bardeen acknowledged the great credit due lilienfeld for his pioneering efforts to make the semiconductor amplifier. in the 1920s, lilienfeld could not have understood the physics of the field - effect semiconductor amplifier, as the quantum theory of solids was still several years away. nevertheless, he had a good intuitive feel for a new approach to electronics. in bardeen ’ s own words, “ lilienfeld had the basic concept of controlling the flow of current in a semiconductor to make an amplifying device. it took many years of theory development and material technology to make his dream a reality. ”
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shaped somewhat like a vast twisted snake swallowing its own tail. it is the world ’ s largest superconductor and the only one of its type in the world. it costs the government ¥5 billion a year to run. the technology started with secret military research in the soviet union and, separately, the united states and great britain, just after world war ii. until today, the most dramatic demonstration of fusion power the world has seen has been purely destructive : the testing of hydrogen bombs set off by atomic bombs and, of course, the nuclear weapons used against the cities of hiroshima and nagasaki in august 1945. nuclear fission splits nuclei to create energy and nuclear fusion joins them to do the same thing. the first fusion device made for peaceful purposes was the tokamak, which was invented by leonid zakharov in russia in 1951. nuclear fission for peaceful use began in 1958 after a united nations conference in geneva on peaceful uses of atomic energy. since then, japan, the european union and the united states have made great efforts to modify and improve the machine. the tokamak is still widely regarded as the most promising fusion device, but there are other similar devices in the world, including one in naka, ibaraki prefecture, and at the culham centre for fusion energy near oxford, england. the tokamak has reached temperatures of 500 million degrees celsius in experiments, more than 30 times hotter than the sun. nuclear power for peaceful use has developed rapidly and there are now 400 nuclear fission power plants around the world. by contrast, the aim of constructing fusion reactors to generate electricity is still in the research and development phase. “ replicating the fusion of helium and hydrogen that powers the sun, in earthly conditions, means generating temperatures beyond 100 million degrees celsius, ” explains yamada. “ this creates plasma, the fourth state of matter after solids, liquids and gases. ” all stars, our sun included, are made of plasma. flashes of lightning are natural plasma and so too are the spectacular northern lights. artificial plasma, at much lower pressure, is present inside neon lights and plasma television screens. “ the extreme temperatures inside the lhd mean the plasma must not be allowed to touch the walls of the device. if it did, ( the walls ) would melt. ” herein lies the main difficulty with the lhd. researchers must create materials strong enough to withstand fusion at temperatures many times hotter than the sun. plasma at extremely high temperatures creates wild, unstable reactions and would irreparably damage any machine made
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” herein lies the main difficulty with the lhd. researchers must create materials strong enough to withstand fusion at temperatures many times hotter than the sun. plasma at extremely high temperatures creates wild, unstable reactions and would irreparably damage any machine made to contain it that uses existing materials. yamada demonstrates this process by heating a circular fluorescent tube inside a microwave oven in a nifs display area. when he takes it out, it casts a purplish glow and is warm to the touch. he says, “ the glass walls of the tube cool the plasma. when a similar reaction occurs inside the sun, its vast gravitational pull keeps the plasma from shooting in all directions. “ once new materials have been invented, the way will be open to constructing fusion reactors able to generate electricity, using easily obtained resources that will never run out. the raw materials needed for creating plasma in fusion reactions, are lithium and deuterium, which can be extracted from seawater. ” one widespread modern use of lithium, is in mobile phones. the amount commonly used in each phone is about 0. 3 grams. together with the deuterium taken from 3 liters of seawater, a fusion reaction equivalent to 22, 000 kilowatt - hours of electric power could be created. this amount of electricity would supply a typical family in a developed country for a couple of years. or to put it another way, one liter of seawater contains enough deuterium to provide the energy content, when fused with tritium, of more than 500 liters of petroleum. fusion power plants of the future, producing a million kilowatts, would need about a tenth of a ton of deuterium and 10 tons of lithium a year as fuel. seawater covers over 70 percent of our planet and rates of extraction for hundreds of fusion reactors around the globe would never exhaust supplies. plasma inside the lhd is prevented from touching the walls by a magnetic field created inside the sinuous innards of the machine. it is done by means of a twisting, orange - hued metal alloy, wound 450 times and coiling round the outer walls of the giant tube. the coil is exposed to an electromagnetic force reaching 1, 000 tons per meter. beforehand the coil and supporting structure are cooled to minus 270 c. when cooled the structure typically shrinks 2 mm. the machine is built to tolerate a shrinkage of 2 cm. hydrogen gas is heated and injected into the machine. after reaching 10, 000 c, the hydrogen molecules disintegrate into atoms.
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the latest news from academia, regulators research labs and other things of interest posted : december 7, 2009 super cool atom thermometer ( nanowerk news ) as physicists strive to cool atoms down to ever more frigid temperatures, they face the daunting task of developing new, reliable ways of measuring these extreme lows. now a team of physicists has devised a thermometer that can potentially measure temperatures as low as tens of trillionths of a degree above absolute zero. their experiment is reported in the current issue of physical review letters and highlighted with a viewpoint in the december 7 issue of physics. physicists have developed a new thermometry method suitable for measuring temperatures of ultracold atoms. ( illustration : alan stonebraker ) physicists can currently cool atoms to a few billionths of a degree, but even this is too hot for certain applications. for example, richard feynman dreamed of using ultracold atoms to simulate the complex quantum mechanical behavior of electrons in certain materials. this would require the atoms to be lowered to temperatures at least a hundred times colder than what has ever been achieved. unfortunately, thermometers that can measure temperatures of a few billionths of a degree rely on physics that doesn ' t apply at these extremely low temperatures. now a team at the mit - harvard center for ultra - cold atoms has developed a thermometer that can work in this unprecedentedly cold regime. the trick is to place the system in a magnetic field, and then measure the atoms ' average magnetization. by determining a handful of easily - measured properties, the physicists extracted the temperature of the system from the magnetization. while they demonstrated the method on atoms cooled to one billionth of a degree, they also showed that it should work for atoms hundreds of times cooler, meaning the thermometer will be an invaluable tool for physicists pushing the cold frontier. source : american physical society translate this article : check out these other trending stories on nanowerk :
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very irregular, sharing features with properly random processes. this idea is colloquially known as chaos theory, and it all goes back to poincare and his oscar award. well, that ’ s the story that historians of mathematics used to tell. around 1990, however, june barrow - green found a copy of poincare ’ s prize - winning memoir in the depths of the mittag - leffler institute in sweden. she realised that when he submitted his work he had overlooked the chaotic solutions. he spotted the error before the memoir was published, and paid to have the original version destroyed and a corrected version printed. his initial oversight lay undiscovered for a century. building on poincare ’ s discovery, we now know that the three - body problem does not have simple solutions. even so, vast progress has been made on the many - body problem in special cases ; for example, when all of the bodies have the same mass. this is seldom a realistic assumption in celestial mechanics, but it is sensible for some models of elementary particles, such as electrons. in 1993, cristopher moore at the sante fe institute found a solution to the three - body problem in which the bodies play follow - my - leader along the same orbit. even more surprising is the shape of the orbit – a figure of eight. stranger than imagination in 2000, the spanish mathematician carles simo used a computer to show that this configuration is stable : it persists after small disturbances. indeed, it remains stable even when the three masses are slightly different, so, somewhere in the universe, there might be three stars of almost identical mass, chasing each other along a figure - of - eight path. the same year, douglas heggie of edinburgh university estimated that the number of such triple stars lies somewhere between one per galaxy and one per universe. the figure - of - eight orbit is a planetary dance in which the bodies return to the same positions but swap their identities, each occupying the location that the body in front of it has vacated. this kind of orbit is called a choreography. using a computer, simo has found a huge number of choreographies, which can involve a large number of bodies. the solar system is, was, and will be, far stranger than we imagine. consider the comet oterma. a century ago, oterma ’ s orbit was well outside that of jupiter. after a close encounter with the giant planet, its orbit shifted inside that of jupiter. after another close encounter, it switched
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2025-12-25T20:50:09.621695
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the nobel prize in physics 2001 eric a. cornell, wolfgang ketterle, carl e. wieman bose - einstein condensation in a dilute gas ; the first 70 years and some recent experiments eric a. cornell held his nobel lecture december 8, 2001, at aula magna, stockholm university. he was presented by professor mats jonson, chairman of the nobel committee for physics. summary : fundamental ideas behind creating bose - einstein condensate ( bec ) in a gas are outlined. starting with heisenberg ' s uncertainty principle, the formation of bose - einstein condensate ( bec ) is explained as occurring when the interatomic spacing is comparable to thermal de broglie wavelength. the conditions for creating bec in a gas are described, and the necessary ingredients for creating bec in a gas are listed in an " ultra cold alkali tool kit ". copyright © nobel web ab 2001 credits : kamera communications ( webcasting ) read the nobel lecture pdf 447 kb copyright © the nobel foundation 2001 from les prix nobel. the nobel prizes 2001, editor tore frangsmyr, [ nobel foundation ], stockholm, 2002 mla style : " eric a. cornell - nobel lecture : bose - einstein condensation in a dilute gas ; the first 70 years and some recent experiments ". nobelprize. org. 22 may 2013 http : / / www. nobelprize. org / nobel _ prizes / physics / laureates / 2001 / cornell - lecture. html
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using an ultra - bright electron source, scientists at the university of toronto have recorded atomic motions in real time, offering a glimpse into the very essence of chemistry and biology at the atomic level. their recording is a direct observation of a transition state in which atoms undergo chemical transformation into new structures with new properties. using a new tool called a quantum simulator — based on a small - scale quantum computer —... a massive telescope buried in the antarctic ice has detected 28 extremely high - energy... a fried breakfast food popular in spain provided the inspiration for the development of doughnut - shaped droplets that may provide scientists with a new approach for studying fundamental issues in physics, mathematics, and materials. the doughnut - shaped droplets, a shape known as toroidal, are formed from two dissimilar liquids using a simple rotating stage and an injection needle. the massive ball of iron sitting at the center of earth is not quite as " rock - solid " as has been thought, say two stanford university mineral physicists. by conducting experiments that simulate the immense pressures deep in the planet ' s interior, the researchers determined that iron in earth ' s inner core is only about 40 % as strong as previous studies estimated. graphene has dazzled scientists ever since its discovery more than a decade ago. but one long - sought goal has proved elusive : how to engineer into graphene a property called a band gap, which would be necessary to use the material to make transistors and other electronic devices. new findings by massachusetts institute of technology researchers are a major step toward making graphene with this coveted property. with the hand of nature trained on a beaker of chemical fluid, the most delicate flower structures have been formed in a harvard university laboratory — and not at the scale of inches, but microns. these minuscule sculptures, curved and delicate, don ' t resemble the cubic or jagged forms normally associated with crystals, though that ' s what they are. rather, fields of flowers seem to bloom from the surface of a submerged glass slide. a new joint innovation by the national physical laboratory and the university of cambridge could pave the way for redefining the ampere in terms of fundamental constants of physics. the world ' s first graphene single - electron pump provides the speed of electron flow needed to create a new standard for electrical current based on electron charge. described as the " most beautiful experiment in physics, " richard feynman emphasized how the diffraction of individual particles at a grating is an unambiguous demonstration of
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needed to create a new standard for electrical current based on electron charge. described as the " most beautiful experiment in physics, " richard feynman emphasized how the diffraction of individual particles at a grating is an unambiguous demonstration of wave - particle duality and contrary to classical physics. a research team recently used carefully made fluorescent molecules and nanometric detection accuracy to provide clear and tangible evidence of the quantum behavior of large molecules in real time. bubble baths and soapy dishwater and the refreshing head on a beer : these are foams, beautiful yet ephemeral as the bubbles pop one by one. now, a team of researchers has described mathematically the successive stages in the complex evolution and disappearance of foamy bubbles, a feat that could help in modeling industrial processes in which liquids mix or in the formation of solid foams such as those used to cushion bicycle helmets. an international team of physicists has found the first direct evidence of pear - shaped nuclei in exotic atoms. the findings could advance the search for a new fundamental force in nature that could explain why the big bang created more matter than antimatter — a pivotal imbalance in the history of everything. from powerful computers to super - sensitive medical and environmental detectors that are faster, smaller, and use less energy — yes, we want them, but how do we get them? in research that is helping to lay the groundwork for the electronics of the future, university of delaware scientists have confirmed the presence of a magnetic field generated by electrons which scientists had theorized existed, but that had never been proven until now. physicists working with optical tweezers have conducted work to provide an all - in - one guide to help calculate the effect the use of these tools has on the energy levels of atoms under study. this effect can change the frequency at which atoms emit or absorb light and microwave radiation and skew results ; the new findings should help physicists foresee effects on future experiments. physicists in switzerland have demonstrated one of the quintessential effects of quantum optics — known as the hong - ou - mandel effect — with microwaves, which have a frequency that 100, 000 times lower than that of visible light. the experiment takes quantum optics into a new frequency regime and could eventually lead to new technological applications. the allure of personalized medicine has made new, more efficient ways of sequencing genes a top research priority. one promising technique involves reading dna bases using changes in electrical current as they are threaded through a nanoscopic hole. now, a
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technological applications. the allure of personalized medicine has made new, more efficient ways of sequencing genes a top research priority. one promising technique involves reading dna bases using changes in electrical current as they are threaded through a nanoscopic hole. now, a team led by university of pennsylvania physicists has used solid - state nanopores to differentiate single - stranded dna molecules containing sequences of a single repeating base. an international research team led by astronomers from the max planck institute for radio astronomy used a collection of large radio and optical telescopes to investigate in detail a pulsar that weighs twice as much as the sun. this neutron star, the most massive known to date, has provided new insights into the emission of gravitational radiation and serves as an interstellar laboratory for general relativity in extreme conditions. using uniquely sensitive experimental techniques, scientists have found that laws of quantum physics — believed primarily to influence at only sub - atomic levels — can actually impact on a molecular level. the study shows that movement of the ring - like molecule pyrrole over a metal surface runs counter to the classical physics that govern our everyday world. in a process comparable to squeezing an elephant through a pinhole, researchers at missouri university of science and technology have designed a way to engineer atoms capable of funneling light through ultrasmall channels. their research is the latest in a series of recent findings related to how light and matter interact at the atomic scale. cancer cells that can break out of a tumor and invade other organs are more aggressive and nimble than nonmalignant cells, according to a new multi - institutional nationwide study. these cells exert greater force on their environment and can more easily maneuver small spaces. one simple phenomenon explains why practical, self - sustaining fusion reactions have proved difficult to achieve : turbulence in the superhot, electrically charged gas, called plasma, that circulates inside a fusion reactor can cause the plasma to lose much of its heat. this prevents the plasma from reaching the temperatures needed to overcome the electrical repulsion between atomic nuclei. until now. lawrence berkeley national laboratory ’ s sound - restoration experts have done it again. they ’ ve helped to digitally recover a 128 - year - old recording of alexander graham bell ’ s voice, enabling people to hear the famed inventor speak for the first time. the recording ends with bell saying “ in witness whereof, hear my voice, alexander graham bell. ” researchers at university of california, santa barbara in collaboration with colleagues at the ecole polytechnique in france, have conclusively identified auger recombination
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2025-12-25T20:50:09.857189
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bell saying “ in witness whereof, hear my voice, alexander graham bell. ” researchers at university of california, santa barbara in collaboration with colleagues at the ecole polytechnique in france, have conclusively identified auger recombination as the mechanism that causes light - emitting diodes ( leds ) to be less efficient at high drive currents. a harvard university - led team of researchers has created a new type of nanoscale device that converts an optical signal into waves that travel along a metal surface. significantly, the device can recognize specific kinds of polarized light and accordingly send the signal in one direction or another. the planet - hunting kepler telescope has discovered two planets that seem like ideal places for some sort of life to flourish. according to scientists working with the nasa telescope, they are just the right size and in just the right place near their star. the discoveries, published online thursday, mark a milestone in the search for planets where life could exist. throughout decades of research on solar cells, one formula has been considered an absolute limit to the efficiency of such devices in converting sunlight into electricity : called the shockley - queisser efficiency limit, it posits that the ultimate conversion efficiency can never exceed 34 % for a single optimized semiconductor junction. now, researchers have shown that there is a way to blow past that limit. scientists in australia have recently demonstrated that ultra - short durations of electron bunches generated from laser - cooled atoms can be both very cold and ultra - fast. the low temperature permit sharp images, and the electron pulse duration has a similar effect to shutter speed, potentially allowing researchers to observe critical but quick dynamic processes, such as the picosecond duration of protein folding. a university of missouri engineer has built a system that is able to launch a ring of plasma as far as two feet. plasma is commonly created in the laboratory using powerful electromagnets, but previous efforts to hold the super - hot material through air have been unsuccessful. the new device does this by changing how the magnetic field around the plasma is arranged. physicists operating an experiment located half a mile underground in minnesota reported this weekend that they have found possible hints of dark - matter particles. the cryogenic dark matter search experiment has detected three events with the characteristics expected of dark matter particles.
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subdomain_quantum_optics
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2025-12-25T20:50:09.858297
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the conviction that nothing exists — it is possible to name a set that has no elements. ) david hilbert, the dean of mathematics at the dawn of the century, had thought that such a reduction was possible and posed it as a challenge. but hilbert was doomed to failure here. the reason for this, at a basic level, is self - reference. sentences like “ this sentence is false ” turn out to pose a nasty set of technical challenges that make it impossible to fully express mathematical knowledge as a consequence of logical axioms — things that are held, on their face, to be true. godel, an austrian logician who would become a good friend of albert einstein ’ s after both of them settled in princeton, proved this in a 1931 paper, whose consequences were later strengthened by turing. godel ’ s incompleteness theorem says that in any sufficiently strong logical system ( meaning one that is rich enough to express mathematics ), it is impossible to prove that the axioms — the assumptions — of the system do not lead to a contradiction. the importance of godel ’ s incompleteness theorems for artificial intelligence is something that remains hotly debated. one school of thought, as ernest nagel and james newman wrote in 1956, holds that incompleteness means “ that the resources of the human intellect have not been, and cannot be, fully formalized, and that new principles of demonstration forever await invention and discovery. ” the other school of thought says, basically, “ don ’ t worry about it! ” the best - known recent exponent of this school is ray kurzweil, who claims, without much evidence, that “ there is an essential equivalence between a computer and the brain. ” kurzweil ’ s overheated triumphalism aside ( he seems determined to prove that careful thought is not necessary to be human by displaying a tremendous lack of care himself ), this is not a question that we need to resolve to say something about what current progress in artificial intelligence is doing to the idea of truth. even if nagel and newman are right and human intellect cannot be fully formalized, computer scientists have come a long way since john mccarthy first enunciated the aim of formalizing common sense. computer scientists have worked to come up with formal descriptions of the everyday world. here is a short list, taken from the stanford encyclopedia of philosophy of some of scenarios they ’ ve tried to encode : the baby scenario, the bus ride scenario, the chess board scenario, the ferryboat connection scenario, the furniture assembly
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subdomain_quantum_computing
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2025-12-25T20:50:10.070659
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world. here is a short list, taken from the stanford encyclopedia of philosophy of some of scenarios they ’ ve tried to encode : the baby scenario, the bus ride scenario, the chess board scenario, the ferryboat connection scenario, the furniture assembly scenario, the hiding turkey scenario, the kitchen sink scenario, the russian turkey scenario, the stanford murder mystery, the stockholm delivery scenario, the stolen car scenario, the stuffy room scenario, the ticketed car scenario, the walking turkey scenario, and the yale shooting anomaly. let ’ s take the last of these — the yale shooting anomaly, which aims to formally codify the fact that an unloaded shotgun, if loaded and then shot at a person, would kill the person. classical logic dealt with things like “ 1 + 1 = 2 ” which are true, ( or false, like 1 = 0 ) for all time. they were true, are true, and always will be true. it doesn ’ t allow for things to happen. but to encode common - sense knowledge, computer scientists need a way to allow for events to take place. they also need ways to encode spatial locations. some of this had been worked out in a rigorous but limited way, in what philosophers call modal logic, which was first enunciated by c. i. lewis in 1918. but modal logic was too limited for computer scientists to use in semireal world systems. in the languages that computer scientists have come up with, as in the yale shooting anomaly, they were unable to preclude the possibility that the shotgun would spontaneously unload itself. it ’ s not that computer scientists think that that will happen ; it ’ s that they struggle to formalize how it can ’ t. ( since the yale shooting anomaly was first stated in 1986, many solutions have been proposed, but it remains an area of research. ) a central challenge computer scientists face is what ’ s called the ramification problem : how to codify that fact that if i walk into a room, my shirt does, too. this is paralleled by the “ frame problem, ” first enunciated by mccarthy in 1969, which is the “ problem of efficiently determining which things remain the same in a changing world. ” these problems are considerably harder than careless cheerleaders like kurzweil make them out to be. the central result of logicians in the 20th century was that, in the end, it will always be necessary to extend your axioms — things you just assume to be true without
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subdomain_quantum_cryptography
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<urn:uuid:bbdae031-edd1-48b3-8f6f-ab3d827c60c4>
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2025-12-25T20:50:10.071656
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polishing characteristics and problems pyrrhotite, chalcopyrite, magnetite and pentlandite. kambalda, western australia the section has been partially polished with 6µm diamond paste. individual grains of pyrrhotite ( brown ) are clearly seen due to differential polishing. crystals in some orientations still retain many polishing pits ( black ) whereas others are well polished. chalcopyrite ( yellow, centre bottom ) and magnetite ( light grey, bottom right ) are present. pentlandite ( pale yellow - brown, centre right and close to a diagonal fracture ) has higher reflectance than pyrrhotite and is just visible within the largest pyrrhotite crystal as small pentlandite flame - like exsolution bodies along a fracture - dark grey area ( bottom right ) is silicate, black areas are polishing pits. coarse features, especially grain boundaries, are well shown after initial polishing, but fine features are still difficult to see. llmenite and haematite. kimberlite pipe. unknown provenance this section has been polished with 1µm diamond paste, but shows extensive plucking. host magnesium - rich ilmenite crystals ( brown ) carry lath - shaped haematite exsolution bodies ( blue - grey ). plucked areas ( black ) have the same size, shape and orientation as the haematite, suggesting that it has been preferentially removed. if more than one phase is plucked in a section then it becomes difficult to estimate modal percentages. bornite, stromeyerite, chalcocite, pyrite and tetrahedrite group mineral. unknown provenance this section has been polished with ¼ µm diamond paste. although the section is scratch - free has enormous relief and hence shows strong shadows about the harder phases. euhedral to subhedral pyrite ( pale yellow, high reflectance ), a tetrahedrite group mineral ( light grey, centre and top centre ) and quartz ( dark grey, bottom centre ) show high relief against the softer copper and silver sulphides. bornite ( brown - red, left ) has an symplectite - like intergrowth with, and inclusions of, chalcocite ( light blue ). stromeyerite ( light lilac - grey, centre right ) also is complexly intergrown with chalcocite. although relief accentuates the symplectite texture of the softer phases, they remain poorly polished
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subdomain_quantum_materials
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HuggingFaceFW/fineweb-edu
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<urn:uuid:d428ba0b-4614-4133-b826-530cea6eea73>
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2025-12-25T20:50:10.075785
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w3c working draft 23 january 2003, http : / / www. w3. org / tr / rdf - concepts [ pascal1 ] " what meaning means ", fabian pascal http : / / www. inconcept. com / jcm [ pascal2 ] " something to call one ' s own ", fabian pascal, http : / / www. dbdebunk. com / fp6a. htm [ riggs ] " xml and free text ", k. r. riggs, journal of the american society for information science and technology, v53, n 6, 2002, 526 - 528 [ schema ] xml schema, w3c org, www. w3. org / xml / schema [ sowa ] knowledge representation, john f. sowa, brooks cole, 2000 [ xirql ] xirql : a query language for information retrieval in xml documents, fuhr, n. großjohann, k. http : / / www. is. informatik. uni - duisburg. de / bib / xml / fuhr _ grossjohann _ 01. html. en [ xml - ql ] xml - ql : a query language for xml, alin deutsch, mary fernandez, daniela florescu, alon levy, dan suciu, http : / / www. w3. org / tr / note - xml - ql / # issues this article previously appeared in the journal of conceptual modeling, may 2003. ken roger riggs, ph. d - ken roger riggs, ph. d. is a computer scientist and a professor of cis at florida a & m university. his degrees are in philosophy ( indiana university ), computer science ( u. of central florida ) and electrical and computer engineering ( u. of miami ). he has been involved in a mix of practice, research and teaching since 1976. his interest in models is both practical and pedagogical. his recent published work includes papers on ai, databases, datamining and xml marking. other recent publications address conceptual modeling related issues in software engineering ( refactoring ) and programming languages.
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subdomain_quantum_field_theory
| 0.631313
| 455
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HuggingFaceFW/fineweb-edu
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<urn:uuid:15747714-b61b-4b8a-81e9-47335d512148>
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2025-12-25T20:50:10.246249
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a material made from fibers or thread by weaving, knitting, felting etc. as any cloth. 1. to make, build or construct by assembling parts or manufacturing. 2. to make from raw material. external front of a building that faces the street or courtyard and is usually used to describe bigger, elegant buildings. fasade materials include wood, brick, glass, masonry, aluminum, etc. 1. the side of a wall covering that faces away from the framing ; for example in an a - b plywood panel, the face would be the a side. 2. an exterior, exposed surface on a structure. 3. any surface of a thing. 4. the outward appearance of anything. the dollar amount, shown on a document. exterior decorative surface, which is made of brick that is not rendered, painted or plastered and is made of various brick materials, including clay, to give a desired effect. applies to the direction of the grain on the face of a veneer - faced panel, which is also called the long dimension of the panel. since the greatest strength and firmness is parallel to the face grain, it is normal to run the face grain across the supports. hardening process for the surface of materials. as an example, the hardening of carbon steel is accomplished by first heating the steel to approximately 1200 degrees f. and then it is immersed in powdered carbon. when some of the carbon is absorbed into the molecular structure of the steel, the surface or face of the steel is hardened. also referred to as the face ply, it is the outer layer when there are two or more layers. face line lines that are made of strong string, which is stretched out and attached to staked boards, so that masons can follow the straightness of it when building masonry walls. nails, which are hammered at right angles ( perpendicular ) to the work surface. also called direct nailing. the side of the material where the weld was applied, which has the exposed weld. face plate holds the work to be turned on a lathe. the plate is then fastened to the lathe headstock, which is the part of the lathe that turns the work. also referred to as the face layer, it is the outer layer when there are two or more layers. additional weld material, which is added to the face of the weld. front of a concrete block. coverings, designed to protect the entire face of a worker when a sander, grinder, etc.
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subdomain_quantum_materials
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HuggingFaceFW/fineweb-edu
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<urn:uuid:4845eb11-16bf-45e5-a4d5-f851bb3fb797>
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2025-12-25T20:50:10.414634
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are two or more layers. additional weld material, which is added to the face of the weld. front of a concrete block. coverings, designed to protect the entire face of a worker when a sander, grinder, etc. are being used. a transparent eye panel allows the worker to be protected from small particles, which are being thrown, while being able to see. the dollar amount shown on a document. measurement of the air velocity as measured at the face of the inlet or outlet in an hvac system. the outer veneer on a piece of plywood. the front wall of a structure or, alternately, a retaining wall. masonry structure that has different types of material as backing and facing, such as brick on concrete, bonded together. veneer covered structural wall. real estate professional who aids in a transaction but does not have an agency relationship with that party and can be known as an intermediary or transaction broker. 1. ease of doing or making ; absence of difficulty. 2. a building or special room, constructed for a specific function. 1. covering of contrasting material to decorate or protect a building ; a finished wall surface. 2. smoothing ; finishing. specifically made brick, in a special color or texture, for the outside or facing wall of a building. a reproduction or exact copy or architecturally a reproduction of a building style. alternately, the electronic transfer of an exact image of a document or picture, referred to as a " fax ". the purchase of the accounts receivable of a business or alternately, taking the accounts receivable of a business as collateral for a loan. the ratio of the maximum strength of a piece of material or a part to the probably maximum load to be applied to it. if a maximum of 2, 000 pounds can be tolerated, a load of 500 pounds will have a 4 to one factor of safety. the edge of any fabricated item that has been prepared in a factory, such as the long edge of wallboard panels, coming from a factory covered with paper. fade. 1. to become less distinct. to lose color or brilliance. 2. to disappear slowly. to wane. also spelled faggot, the term refers to a bundle of sticks or branches to be used for fuel, or alternately, a bundle of iron or steel pieces to be hammered or rolled, at welding temperature, into bars. temperature measurement, named after its discoverer daniel fahrenheit 1686 - 1736, in which 32 degrees is the freezing point and
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subdomain_quantum_materials
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HuggingFaceFW/fineweb-edu
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<urn:uuid:4845eb11-16bf-45e5-a4d5-f851bb3fb797>
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2025-12-25T20:50:10.419233
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generating and guiding laser signals. they also helped determine the properties of quantum dot materials. quantum dots, which emit the light that creates lasers, are nanometer - size semiconductor structures in which the presence or absence of a quantum electron can be used to store information. " we tried to modify the bandgap and lasing wavelength in order to control the optical properties of the quantum - dot structures, " says soo, who hopes to continue her work in the area by setting up the photoluminescent system that can characterize this nano - material structure. using labview software, negro and oh integrated the new equipment to a central computer, then merged data from two or more machines so that the experimental results could be plotted in one graph on the computer screen. " without the computer, it would have taken an entire day to generate a graph, " says negro. " with the computer, we generated the same graph in two seconds. " in addition to gaining valuable experience in the lab, the students realized other benefits from their summer internship. " this opened a wide variety of options for me, " says negro, who hopes to take advantage of the university ' s presidential scholarship program, which offers a tuition - free fifth year of study to students with a 3. 75 undergraduate gpa. " working in a lab requires a lot of patience and dedication, " says oh. " it has enabled me to see what it would be like to be a graduate student. it has also shown me what i ' m lacking, and that will help me know what electives to choose the next two years. " posted on wednesday, december 01, 2004
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subdomain_quantum_optics
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HuggingFaceFW/fineweb-edu
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2025-12-25T20:50:10.640461
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brookhaven national laboratory has what is currently one of the highest energy particle accelerators on the planet. the relativistic heavy ion collider ( rhic ) hosts collisions between the nuclei of gold atoms that are moving at roughly 99 percent of the speed of light, creating a quark soup similar to the one that existed immediately after the big bang. but the scientists running the experiments started noticing something funny about the data : instead of expanding evenly outward, the collision debris were ellipsoidal ( think a 3 - d ellipse ). what was even stranger was that this sort of behavior had already been described, for a gas of lithium atoms at the opposite end of the temperature spectrum, at a fraction of a microkelvin. as these groups were talking about a collaboration, things got stranger still when string theorists started citing this work, since the behavior had already been predicted through their work — a fact that the physicists weren ' t aware of until a science reporter called to ask what they thought about it. the tale of this unlikely collaboration unfolded at the american association for the advancement of science meeting, where the introductory remarks described just how far apart these systems are. in terms of temperature, the rhic and chilled lithium differ by 19 orders of magnitude ( that ' s a factor of 1019 ). when it comes to density, the difference is an astonishing 25 orders of magnitude. meanwhile, the bit of string theory that describes the normal, four - dimensional ( 3 - d + time ) behavior of these systems can be predicted by modeling a four - dimensional sphere wrapped around a five dimensional black hole. quantum viscosity runs hot and cold the cold atomic cloud is probably easiest to understand, although john thomas of duke, who does the work, claimed that, when dragged to wine tastings with his wife ' s friends, " i wait until everyone ' s sufficiently drunk before explaining what we do. " his short description is that he makes bowls of light ; in principle, the first steps in his system involve the sort of laser cooling that our chris lee has described in the past. this can only get things down to a bit under a kelvin above absolute zero, but thomas then loosens the laser trap, and a few atoms evaporate off, taking most of the remaining heat with them. the end result is an atomic cloud at one - tenth of a microkelvin. the 6li atoms that he uses have up and down spins that form an analog of the cooper pairs of electrons that cause high - temperature supercondu
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subdomain_quantum_materials
| 0.653359
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:4b3439ec-7a03-4190-bead-e890fe4fe4c9>
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2025-12-25T20:50:10.729167
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with them. the end result is an atomic cloud at one - tenth of a microkelvin. the 6li atoms that he uses have up and down spins that form an analog of the cooper pairs of electrons that cause high - temperature superconductivity, so his system allows theorists to test some of their ideas in an accessible experimental system. but it also has interesting properties when in a magnetic field. at a specific magnetic field strength, the interactions between the paired atoms start to go asymptotic and, when at a very precise point, the interactions vanish and quantum effects dominate. when the laser trap is released again, the atoms expand elliptically, displaying essentially the smallest amount of quantum viscosity possible. because the system is experimentally possible, they were able ( on the advice of string theorists — more on that below ) to measure both the viscosity and entropy, and found that they were related directly to one divided by four?. out at the other end of the temperature spectrum, the collisions in the rhic were producing what brookhaven ' s barbara jacack termed " quark soup. " in normal matter, quarks interact by exchanging gluons with a limited number of partners. but, at the densities that exist immediately after these collisions, quarks can exchange multiple gluons with multiple partners, leading to longer - range interactions that are more similar to those in a liquid. two aspects of the behavior seen by rhic ' s detectors, however, were a bit surprising. the first is the ellipsoidal expansion that marks the behavior of perfect quantum liquids that we mentioned above. the second is that, although radiation can pass across the small cluster of quark soup, the actual quarks, it appeared, could not. jacack likened the fact that even the heavy charm quark didn ' t make it across the collision to a set of bowling pins stopping an incoming ball. like thomas, talking to string theorists allowed jacack and her team to look for some specific properties — in this case, shock waves of a particular type — of the quark soup. so far, it ' s looking like they ' re there. rhic is about to undergo a retrofit that should make it easier to study this, and the stimulus package may have some money for the doe that could accelerate the work. the theory needs a five - dimensional black hole, but reality may not clifford johnson of usc then spoke about how a specific application of string theory helped tie everything together
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subdomain_quantum_materials
| 0.663573
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HuggingFaceFW/fineweb-edu
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<urn:uuid:4b3439ec-7a03-4190-bead-e890fe4fe4c9>
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2025-12-25T20:50:10.730399
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, and the stimulus package may have some money for the doe that could accelerate the work. the theory needs a five - dimensional black hole, but reality may not clifford johnson of usc then spoke about how a specific application of string theory helped tie everything together. as he described it, quantum chromodynamics ( qcd ) works very well at describing the interactions of a limited number of particles, and its successes in the early 1970s caused researchers to abandon an earlier version of string theory. but qcd doesn ' t work that well at the densities seen in the rhic, where ensembles of particles have emergent behavior — as johnson noted, a single water molecule isn ' t wet ; that ' s a property that emerges from a population of water molecules. and this, along with a few other vexing problems, has allowed string theory back in the game. " string theory, " johnson said, " having failed to explain something, got resurrected a few years on and was used to explain everything, " or at least provide a quantum description of gravity. he got interested in the problem of describing quantum black holes, which are far smaller than the macroscopic ones we ' ve observed in space. based on their emission of quantum radiation, they have to have an internal structure, one that our lack of a quantum gravity is preventing us from probing. ( during the questions, it became clear that johnson is one of the few people hoping that the lhc does spawn a small black hole. ) it turns out, using the math of string theory, it ' s easy to examine a five - dimensional black hole simply by wrapping a four - dimensional sheet around it. when you do that, however, a lot of three - dimensional qcd behavior pops out of the equations — " the bugs of string theory become features, " as johnson put it. in the extra dimensions, gravitons get pulled towards, and then bounce off, the black hole, undergoing interference as they do. that interference apparently describes the behavior seen in both of these real - world systems. johnson was emphatic that this doesn ' t mean that the experiments that have used these string theory models are a test of the theory ; rather, it means that the predictions of string theory are being used to guide experiments, which is a measure of its utility. as for whether there ' s really an extradimensional black hole tucked away in these conditions, johnson described himself as " agnostic. " it may be possible, he said, to find a way to describe this
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subdomain_quantum_field_theory
| 0.643198
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HuggingFaceFW/fineweb-edu
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2025-12-25T20:50:10.731779
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an efficient solar harvest solar power could be harvested more efficiently and transported over longer distances using tiny molecular circuits based on quantum mechanics, according to research inspired by new insights into natural photosynthesis. incorporating the latest research into how plants, algae and some bacteria use quantum mechanics to optimize energy production via photosynthesis, ucl scientists have set out how to design molecular circuitry that is 10 times smaller than the thinnest electrical wire in computer processors. published in nature chemistry, the report discusses how tiny molecular energy grids could capture, direct, regulate and amplify raw solar energy. solar fuel production is all about energy from light being absorbed by an assembly of molecules ; this electronic excitation is subsequently transferred to a suitable acceptor. for example, in photosynthesis, antenna complexes capture sunlight and direct the energy to reaction centers that then carry out the associated chemistry. in photosynthesis chlorophyll captures sunlight and directs the energy to special proteins that help make oxygen and sugars. this is no different in principle than a solar cell. in natural systems energy from sunlight is captured by colored molecules called dyes or pigments, but it is only stored for a billionth of a second. this leaves little time to route the energy from pigments to the molecular machinery that produces fuel or electricity. the key to transferring and storing energy very quickly is to harness the collective quantum properties of antennae, which are made up of just a few tens of pigments. recent studies have identified quantum coherence and entanglement between the excited states of different pigments in the light - harvesting stage of photosynthesis. although this stage of photosynthesis is highly efficient, it remains unclear exactly how or if these quantum effects are relevant. dr alexandra olaya - castro, co - author of the paper from ucl ’ s department of physics and astronomy said : “ on a bright sunny day, more than 100 million billion red and blue colored photons strike a leaf each second. ” “ under these conditions plants need to be able to both use the energy that is required for growth but also to get rid of excess energy that can be harmful. transferring energy quickly and in a regulated manner are the two key features of natural light harvesting systems. “ by assuring that all relevant energy scales involved in the process of energy transfer are more or less similar, natural antennae manage to combine quantum and classical phenomena to guarantee efficient and regulated capture, distribution and storage of the sun ’ s energy. ” summary of lessons from nature about concentrating and
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subdomain_quantum_computing
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HuggingFaceFW/fineweb-edu
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<urn:uuid:5650b21a-52be-4f3e-bbd4-894e5d1fd662>
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2025-12-25T20:50:10.940158
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the study of motion is often called kinematics. we will begin our study with one dimensional kinematics. we will later expand to 2 and 3 dimensional kinematics after we have studied vectors. we can give the position of an object in relation to a reference point. there are a number of variables we can use for position, such as x, d, or s. the official metric unit for position is the meter ( abbreviated m ). the meter was first defined in terms of the circumference of the earth on a meridian passing through paris. it is now defined in terms of the speed of light. when working with other scales, it might be convenient to use other metric units such as the nanometer ( nm ), the centimeter ( cm ), and the kilometer ( km ). we will often use exponential notation. exponential notation is convenient for expressing very large and small numbers. for instance, 12, 300 would be expressed as 1. 23 x 10, 000 or 1. 23 x 104 so 3. 14 km = 3140 m = 3. 14 x 103 m for small numbers, 0. 000345 = 3. 45 x 10 - 4 a micrometer, 1 μm = 10 - 6 m the width of a human hair on average is 10 μm. this would be 10 x 10 - 6 m. the wavelength of a helium - neon laser is 633 nm = 633 x 10 - 9 m = 6. 33 x 10 - 7 m the common metric units are given in powers or 3. the kilometer is 1000 m. although the 100 centimeters = 1 meter it is not actually a common unit. 1 millimeter = 1mm = 10 - 3 m 1 micrometer = 1um = 10 - 6 m 1 nanometer = 1nm = 10 - 9 m 1 picometer = 1pm = 10 - 12 m 1 femotometer = 1fm = 10 - 15 m also known as a fermi except for kilometer, we often do not use the larger metric prefixes for distance. but they are used for frequencies and other units in physics. 1 kilometer = 1 km = 1000 m = 103 m megameter = 1mm = 106 m gigameter = 1gm = 109 m terrameter = 1 tm = 1012 m common british imperial units for measuring distance include the inch, the foot, the yard, and the mile. an easy way to remember the conversion from meters to miles can be remembered in terms of track and field. the loop in a track
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subdomain_quantum_metrology
| 0.631876
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HuggingFaceFW/fineweb-edu
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<urn:uuid:627b76b2-d80d-4591-b9b8-01ec5ccc1148>
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2025-12-25T20:50:10.970371
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5 m due east. as displacement has both a magnitude and a direction, we call it a vector. we measure time in seconds. we will use the variable t for time. the elapsed time for a certain action would be δt. the greek letter delta, δ, is used to represent a change in a quantity. if we are talking about a reoccurring event ( such as the orbit of the earth around the sun ) we talk about the period of time t, with a capitol t. for longer periods of time we will often use the conventional minutes, hours, days, or years. for shorter periods of time will often use exponential notation or may use milliseconds, microseconds, picoseconds, or femtoseconds. for instance, chemical reactions may often take place on the picosecond timescale. just as when you dance under a strobe like at a cool school dance you can see your movements in stop action. scientists use pulsed lasers with picosecond and femtosecond pulses to examine dynamics at the molecular level. speed and velocity building on changes in position and changes in time, we can examine the rate at which these changes in position take place. how fast are we moving? you probably use the terms speed and velocity interchangeably in your everyday vernacular, but in physics they have distinct meanings. speed is a scalar and has no direction. speed can be defined as speed = distance / elapsed time velocity is a vector. we could consider velocity to be speed in a given direction. to calculate the average velocity over a period of time, we use displacement and elapsed time. where v is velocity, x is position, t is time. the greek letter delta, δ, means a change in a quantity, such as the change in position or the change in time. the bar over the velocity v means the terms in averaged. for instance, δx = xf – xo, or the change is position equals the difference of the final position and the original positions. our first set of problems will involve the above kinematic equation. problem solving method when solving physics problems, it is useful to follow a simple problem solving strategy. although at first, it may be easy to solve some problems in your head, by following this strategy you will develop good problem solving habits. just as you must develop good habits by brushing your teeth every day, you should attempt to follow the following methodology for solving physics problems. the
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subdomain_quantum_metrology
| 0.615089
| 512
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<urn:uuid:627b76b2-d80d-4591-b9b8-01ec5ccc1148>
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2025-12-25T20:50:10.972421
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general chemistry / periodicity and electron configurations blocks of the periodic table the periodic table does more than just list the elements. the word periodic means that in each row, or period, there is a pattern of characteristics in the elements. this is because the elements are listed in part by their electron configuration. the alkali metals and alkaline earth metals have one and two valence electrons ( electrons in the outer shell ) respectively. these elements lose electrons to form bonds easily, and are thus very reactive. these elements are the s - block of the periodic table. the p - block, on the right, contains common non - metals such as chlorine and helium. the noble gases, in the column on the right, almost never react, since they have eight valence electrons, which makes it very stable. the halogens, directly to the left of the noble gases, readily gain electrons and react with metals. the s and p blocks make up the main - group elements, also known as representative elements. the d - block, which is the largest, consists of transition metals such as copper, iron, and gold. the f - block, on the bottom, contains rarer metals including uranium. elements in the same group or family have the same configuration of valence electrons, making them behave in chemically similar ways. causes for trends there are certain phenomena that cause the periodic trends to occur. you must understand them before learning the trends. effective nuclear charge the effective nuclear charge is the amount of positive charge acting on an electron. it is the number of protons in the nucleus minus the number of electrons in between the nucleus and the electron in question. basically, the nucleus attracts an electron, but other electrons in lower shells repel it ( opposites attract, likes repel ). shielding effect the shielding ( or screening ) effect is similar to effective nuclear charge. the core electrons repel the valence electrons to some degree. the more electron shells there are ( a new shell for each row in the periodic table ), the greater the shielding effect is. essentially, the core electrons shield the valence electrons from the positive charge of the nucleus. electron - electron repulsions when two electrons are in the same shell, they will repel each other slightly. this effect is mostly canceled out due to the strong attraction to the nucleus, but it does cause electrons in the same shell to spread out a little bit. lower shells experience this effect more because they are smaller and allow the electrons to interact more. coulomb ' s
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subdomain_quantum_materials
| 0.658606
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:7ab562e2-c61b-4988-9c51-24c5b3cb1d20>
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2025-12-25T20:50:11.288090
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canceled out due to the strong attraction to the nucleus, but it does cause electrons in the same shell to spread out a little bit. lower shells experience this effect more because they are smaller and allow the electrons to interact more. coulomb ' s law coulomb ' s law is an equation that determines the amount of force with which two charged particles attract or repel each other. it is, where is the amount of charge ( + 1e for protons, - 1e for electrons ), is the distance between them, and is a constant. you can see that doubling the distance would quarter the force. also, a large number of protons would attract an electron with much more force than just a few protons would. trends in the periodic table most of the elements occur naturally on earth. however, all elements beyond uranium ( number 92 ) are called trans - uranium elements and never occur outside of a laboratory. most of the elements occur as solids or gases at stp. stp is standard temperature and pressure, which is 0° c and 1 atmosphere of pressure. there are only two elements that occur as liquids at stp : mercury ( hg ) and bromine ( br ). bismuth ( bi ) is the last stable element on the chart. all elements after bismuth are radioactive and decay into more stable elements. some elements before bismuth are radioactive, however. atomic radius leaving out the noble gases, atomic radii are larger on the left side of the periodic chart and are progressively smaller as you move to the right across the period. conversely, as you move down the group, radii increase. atomic radii decrease along a period due to greater effective nuclear charge. atomic radii increase down a group due to the shielding effect of the additional core electrons, and the presence of another electron shell. ionic radius for nonmetals, ions are bigger than atoms, as the ions have extra electrons. for metals, it is the opposite. extra electrons ( negative ions, called anions ) cause additional electron - electron repulsions, making them spread out farther. fewer electrons ( positive ions, called cations ) cause fewer repulsions, allowing them to be closer. | ionization energy is the energy required to strip an electron from the atom ( when in the gas state ). ionization energy is also a periodic trend within the periodic table organization. moving left to right within a period or upward within a group, the first ionization energy generally increases. as the
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subdomain_quantum_materials
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| 512
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<urn:uuid:7ab562e2-c61b-4988-9c51-24c5b3cb1d20>
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2025-12-25T20:50:11.289073
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an electron from the atom ( when in the gas state ). ionization energy is also a periodic trend within the periodic table organization. moving left to right within a period or upward within a group, the first ionization energy generally increases. as the atomic radius decreases, it becomes harder to remove an electron that is closer to a more positively charged nucleus. ionization energy decreases going left across a period because there is a lower effective nuclear charge keeping the electrons attracted to the nucleus, so less energy is needed to pull one out. it decreases going down a group due to the shielding effect. remember coulomb ' s law : as the distance between the nucleus and electrons increases, the force decreases at a quadratic rate. it is considered a measure of the tendency of an atom or ion to surrender an electron, or the strength of the electron binding ; the greater the ionization energy, the more difficult it is to remove an electron. the ionization energy may be an indicator of the reactivity of an element. elements with a low ionization energy tend to be reducing agents and form cations, which in turn combine with anions to form salts. electron affinity | electron affinity is the opposite of ionization energy. it is the energy released when an electron is added to an atom. electron affinity is highest in the upper left, lowest on the bottom right. however, electron affinity is actually negative for the noble gasses. they already have a complete valence shell, so there is no room in their orbitals for another electron. adding an electron would require creating a whole new shell, which takes energy instead of releasing it. several other elements have extremely low electron affinities because they are already in a stable configuration, and adding an electron would decrease stability. electron affinity occurs due to the same reasons as ionization energy. electronegativity is how much an atom attracts electrons within a bond. it is measured on a scale with fluorine at 4. 0 and francium at 0. 7. electronegativity decreases from upper right to lower left. electronegativity decreases because of atomic radius, shielding effect, and effective nuclear charge in the same manner that ionization energy decreases. metallic character metallic elements are shiny, usually gray or silver colored, and good conductors of heat and electricity. they are malleable ( can be hammered into thin sheets ), and ductile ( can be stretched into wires ). some metals, like sodium, are soft and can be cut with a knife. others, like iron,
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subdomain_quantum_materials
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<urn:uuid:7ab562e2-c61b-4988-9c51-24c5b3cb1d20>
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2025-12-25T20:50:11.290102
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in the karlsruhe physics course one defines the term " substance - like " quantity : let my cite the definition from a paper by falk, herrmann and schmid : " there is a class of physical quantities whose characteristics are especially easy to visualize : those extensive physical quantities to which a density can be assigned. these include electric charge, mass, amount of substance ( number of particles ), and others. because of the fundamental role these quantities play throughout science and because such quantities can be distributed in and flow through space, we give them a designation of their own : substance - like. " are there examples of extensive quantities, which are not substance - like? i think volume is one example, since it seems to make no sense to assign a density to it, are there others? now the authors write that a quantity can only be conserved if it is substance - like, let my cite this from an other publication : f. herrmann, writes : " it is important to make clear that the question of conservation or non - conservation only makes sense with substance - like quantities. only in the context of substance - like quantities does it make sense to ask the question of whether they are conserved or not. the question makes no sense in the case of non - substance - like quantities such as field strength or temperature. " so my second question is : why has a conserved quantity to be substance like? it would be great if one could give me a detailed explanation ( or a counterexample if he thinks the statement is wrong ). are there resources where the ideas cited above are introduced with some higher degree of detail and rigour?
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subdomain_quantum_materials
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<urn:uuid:38e7da68-52df-433a-bb58-c531417c0521>
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2025-12-25T20:50:12.253727
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and q ) is equiv. to ( q and p ) | | association ( 1 ) | | [ p ∨ ( q ∨ r ) ] [ ( p ∨ q ) ∨ r ] | | p or ( q or r ) is equiv. to ( p or q ) or r | | association ( 2 ) | | [ p ∧ ( q ∧ r ) ] [ ( p ∧ q ) ∧ r ] | | p and ( q and r ) is equiv. to ( p and q ) and r | | distribution ( 1 ) | | [ p ∧ ( q ∨ r ) ] [ ( p ∧ q ) ∨ ( p ∧ r ) ] | | p and ( q or r ) is equiv. to ( p and q ) or ( p and r ) | | distribution ( 2 ) | | [ p ∨ ( q ∧ r ) ] [ ( p ∨ q ) ∧ ( p ∨ r ) ] | | p or ( q and r ) is equiv. to ( p or q ) and ( p or r ) | | double negation | | p ¬¬p | | p is equivalent to the negation of not p | | transposition | | ( p → q ) ( ¬q → ¬p ) | | if p then q is equiv. to if not q then not p | | material implication | | ( p → q ) ( ¬p ∨ q ) | | if p then q is equiv. to either not p or q | | material equivalence ( 1 ) | | ( p ↔ q ) [ ( p → q ) ∧ ( q → p ) ] | | ( p is equiv. to q ) means, ( if p is true then q is true ) and ( if q is true then p is true ) | | material equivalence ( 2 ) | | ( p ↔ q ) [ ( p ∧ q ) ∨ ( ¬q ∧ ¬p ) ] | | ( p is equiv. to q ) means, either ( p and q are true ) or ( both p and q are false ) | | exportation | | [ ( p ∧ q ) → r ] [ p → ( q → r ) ] | | from ( if p and q are true then r is true ) we can prove ( if q is true then r is true, if p is true ) | | importation | | [ p
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subdomain_quantum_cryptography
| 0.608821
| 502
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<urn:uuid:abf62f4b-025d-4eed-a076-36ebb98d1a56>
| 2
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2025-12-25T20:50:12.305834
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what is an ssl certificate? the secure sockets layer ( ssl ) protects data transferred over http using encryption enabled by a servers ssl certificate. an ssl certificate is an electronic file that uniquely identifies individuals and web sites and enables encrypted communications. an ssl certificate contains a public key and a private key. a public key is used to encrypt information and a private key is used to decipher it. when a browser points to a secured domain, an ssl handshake authenticates the server and the client and establishes an encryption method and a unique session key. they can begin a secure session that guarantees message privacy and message integrity. ssl certificates serve as a kind of digital passport or credential. typically, the " signer " of a certificate is a " certificate authority " ( ca ), such as verisign. encryption, the process of transforming information to make it unintelligible to all but the intended recipient, forms the basis of data integrity and privacy necessary for e - commerce. customers submit sensitive information and purchase goods or services via the web only when they are confident that their personal information is secure. the solution for businesses that are serious about online transactions is to implement a trust infrastructure based on encryption technology. the diagram below illustrates the process that guarantees protected communications between a web server and a client. all exchanges of ssl certificates occur within seconds, and require no action by the consumer.
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subdomain_quantum_cryptography
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| 293
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<urn:uuid:fcd9cc22-0603-4b83-b0e2-026b0c2b8006>
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2025-12-25T20:50:12.376778
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of solar gases at temperatures as high as 5 million degrees k ( 9 million deg. f ). while the sun is more than 99. 9 percent hydrogen and helium, it carries significant quantities of carbon, iron, calcium, silicon, and other elements. heavier elements have more protons ( carbon is 6, iron is 26 ) in their nuclei than do lighter elements ( hydrogen is 1, helium is 2 ). that means that as electrons are stripped from heavier atoms, the charge of the larger number of protons is devoted to the few remaining electrons. it takes ever more energy to strip off another electron. as a result, light from energetic atoms acts like a tracer that reveals where the sun is hot and at what temperatures. this is important to dissecting activities from the sun ' s corona - its outer atmosphere - through the transition region and to the chromosphere and photosphere - the visible " surface. " the challenge is that the x - ray emissions are so energetic that they pass through materials rather than being reflected as visible light would be. the usual trick to making x - ray images is called grazing incidence reflection. just as light will reflect off clear glass ( or a rock will skip on a pond ) if it strikes at a shallow angle, x - rays will reflect - and be focused - if they, too, strike at an even shallower angle. several x - ray telescopes, such as, the advanced x - ray astrophysics facility use this. the mssta works by a different effect. its multi - layer mirrors comprise an ultrasmooth mirror coated by up to 100 layers of heavy elements like tungsten spaced by layers of lightweight elements like carbon. in effect, the layers work like a bragg crystal, which will reflect x - rays. everything is extremely smooth, on the order of 0. 1 nm ( a 10 billionth of a meter, or 1 / 250 millionth of an inch ). these reflect a little bit of the x - rays at the surface of each layer pair. the choice of materials and the thickness of the layers determine precisely which wavelength is making the x - rays interfere with each other reflection. in this way, the scientists can fine tune a telescope to observe in a narrow band of wavelengths ( a spectral band ) or even one wavelength. that makes it possible to measure the temperature of the solar atmosphere. to observe the sun in several wavelengths at once, several telescopes must be flown together. this unique approach makes it possible to use conventional optical layouts - like the hubble space
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subdomain_quantum_materials
| 0.606973
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:1b899863-c049-49a1-879d-ec0ca252ae61>
| 1
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2025-12-25T20:50:12.434519
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winner : quantum leap quantum - dot lasers from japan ' s qd laser will make high - speed " fiber to the home " networks simpler, cheaper, and more power - efficient image : qd laser collecting the dots one of qd laser ’ s achievements, as shown in these atomic - force microscope images, was to double the dot density in its quantum - dot lasers, from 30 billion [ left ] to 60 billion [ right ] dots per square centimeter. this is part of ieee spectrum ' s special report : winners & losers 2009, the year ' s best and worst of technology. japanese start - up qd laser ’ s yasuhiko arakawa [ left ] and mitsuru sugawara oversaw the 15 - year effort to commercialize a temperature - stable semiconductor laser. suppose you had a dog whose personality fluctuated with the weather. on cool, crisp mornings, he ’ s a champ, fetching, rolling over, and shaking hands at your slightest command. but as the sun climbs higher and the day warms up, he becomes less and less responsive, and you have to ply him with doggy treats to get him to obey. and during heat waves? forget about it — he barely plays dead unless you double or triple his kibble ration. while you could excuse such behavior in fido, something remarkably similar goes on all the time with the semiconductor lasers used in cd and dvd players and in optical communications. these tiny devices are incredibly sensitive to heat. even a small rise in temperature causes the electrons within to move around faster and migrate out of the laser ’ s active layer — the thin slice of semiconducting material where the electrons recombine with positively charged holes to make light. as a result, the laser ’ s light output fluctuates, and it needs stronger and stronger electrical currents to keep lasing. at 85 °c, the device might need two or three times as much current to produce the same amount of light as at 25 °c. to get around that shortcoming, developers of semiconductor lasers must either cool them or introduce extra circuitry that maintains the device ’ s output even as the temperature fluctuates. but those workarounds increase both the cost of making the lasers and the power they consume. ever since this problem came to light, researchers have been hunting for a semiconductor laser that is inherently stable. one promising technology, first proposed 27 years ago, is the quantum - dot laser. such a device tightly confines the electrons and holes within many nanoscale
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subdomain_quantum_computing
| 0.656773
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:39bf3941-13df-439d-8fa6-4ff05697693e>
| 0
| 0.6
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2025-12-25T20:50:12.557001
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this problem came to light, researchers have been hunting for a semiconductor laser that is inherently stable. one promising technology, first proposed 27 years ago, is the quantum - dot laser. such a device tightly confines the electrons and holes within many nanoscale blobs, or dots, of semiconducting material. with enough dots — millions or billions, that is — lasing will occur and steady output maintained, regardless of external temperature. while researchers can now grow these devices using standard molecular - beam epitaxy equipment, mass - producing them has been very tricky. the japanese start - up qd laser, of tokyo, a joint venture of fujitsu and mitsui venture capital corp., has finally succeeded. its quantum - dot lasers use inexpensive substrates made from gallium arsenide ( gaas ) and boast an industry - leading density of 60 billion dots per square centimeter [ see images, ” collecting the dots ” ]. compared with the conventional indium - phosphide lasers now used in optical networks, qd laser ’ s devices will consume just half the power while transmitting up to 10 gigabits of data per second at a wavelength of 1. 3 micrometers. best of all, they will generate the same output at any temperature from – 40 to 100 °c. to mass - produce the gaas laser chips, qd laser has partnered with one of japan ’ s leading consumer - electronics firms, which will use the same production lines on which it currently cranks out conventional red lasers for dvd and cd players, video - game consoles, and other products. ( qd laser says it will reveal the name of its partner later this year. ) the initial shipments of laser chips are destined for an unnamed optical equipment vendor, which sometime this spring will begin offering the world ’ s first optical transceivers incorporating a quantum - dot laser. fujitsu will almost certainly buy the transceivers for use in optical lans and fiber - to - the - home networks. the quantum - dot laser has long been envisioned as a successor to the quantum - well laser, itself an improvement on earlier laser designs because it confined the injected electrons to an extremely thin layer — no more than tens of nanometers thick — of active material. that way, it required less current to induce lasing. but like the ” bulk ” semiconductor lasers it superseded, the quantum - well laser is sensitive to temperature. in the active layer of a bulk semiconductor laser, which you can picture as a fat, rectangular
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subdomain_quantum_optics
| 0.636067
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:39bf3941-13df-439d-8fa6-4ff05697693e>
| 1
| 0.6
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2025-12-25T20:50:12.557997
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, it required less current to induce lasing. but like the ” bulk ” semiconductor lasers it superseded, the quantum - well laser is sensitive to temperature. in the active layer of a bulk semiconductor laser, which you can picture as a fat, rectangular slab, the electrons and holes move in three dimensions, and that makes their interactions hard to control. in a quantum - well laser, they can move in only two dimensions, but electrostatic fields tend to build up, pulling the electrons away from the holes. in both cases, an increase in temperature makes the electrons more unruly. researchers began looking at ways to confine the electrons even further. in 1980, yasuhiko arakawa, a 28a ¿ ¿ year - old associate professor at the university of tokyo, had an epiphany. ” i thought, if we fix the position of each electron by confining it in a small box, the energy distribution will not be affected by temperature, ” arakawa recalled in a recent interview at his office at the university of tokyo. each ” box ” would be a semiconducting nanosize crystal into which electrons and holes would be injected. the box would effectively prevent the electrons and holes from being thermally excited to higher energy states. he presented his quantum - box laser idea at the annual meeting of the japanese society of applied physics in march 1981. then, collaborating with another professor, hiroyuki sakaki, he published a paper on the topic in the 1 june 1982 issue of applied physics letters. the two researchers followed up with a series of experiments in which they confined electrons using 30 - tesla magnets and demonstrated that the devices worked the same over a wide temperature range. ” but i thought it would be impossible to fabricate such nanostructures until the 21st century, ” arakawa says. the quantum - box laser concept didn ’ t exactly set the world on fire. some people found it interesting but not particularly useful, while others concluded that the boxes would be structurally unstable. his early work ” attracted almost no one to the field, ” says arakawa, now an ieee fellow. today, he adds, thousands of researchers worldwide are working to advance the field. just three years after arakawa and sakaki ’ s paper, a research group at france ’ s centre national d ’ etudes des telecommunications ( cnet ) noticed a strange phenomenon in the ” superlattices ” they were trying to build out of extremely thin alternating layers of indium arsenide and gallium ars
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subdomain_quantum_optics
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HuggingFaceFW/fineweb-edu
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<urn:uuid:39bf3941-13df-439d-8fa6-4ff05697693e>
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2025-12-25T20:50:12.559294
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research group at france ’ s centre national d ’ etudes des telecommunications ( cnet ) noticed a strange phenomenon in the ” superlattices ” they were trying to build out of extremely thin alternating layers of indium arsenide and gallium arsenide. studying their handiwork under an electron microscope, they noticed that some of the indium arsenide had formed tiny regular blobs atop the underlying layer of gallium arsenide. each blob, it turned out, was a quantum dot. the french team didn ’ t actually produce lasing from their weird structure, but it was a start. in 1994, a team at the tokyo institute of technology and a collaboration of the technical university of berlin, russia ’ s ioffe physico - technical institute, and the max planck institute of microstructure physics independently demonstrated the first quantum - dot lasers. ( at that point, the quantum - dot versus quantum - box terminology was still in flux, with the german - russian team using the former term and the japanese using the latter. eventually, arakawa says, the world settled on quantum dot. ” now even i call them quantum dots, ” he says. ) but it ’ s one thing to create an experimental device in the lab and another thing to mass - produce a laser that operates reliably, can be manufactured cheaply, and performs a useful function. qd laser ’ s president and ceo, mitsuru sugawara, and his colleagues began chipping away at the problem of commercialization in 1994. sugawara was then a research physicist at fujitsu, aiming to develop a temperature - stable laser that emitted at 1. 3 µm, the best wavelength for optical communications. ” we weren ’ t interested in quantum dots per se, ” sugawara recalled in an interview last fall. like the cnet group, he and his team had been working on superlattices when they noticed quantum dots forming spontaneously, sugawara says, ” like water beading up on a waxed car. ” after realizing what they ’ d done, they set to work on building a laser. ” we knew that to produce lasing, we had to increase the density of the dots, so we started to study how to grow them intentionally, ” he says. five years later, in 1999, they demonstrated their first quantum - dot laser with a wavelength of 1. 3 µm. in a perfect world, the fujitsu group would have continued to make steady progress,
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subdomain_quantum_optics
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<urn:uuid:39bf3941-13df-439d-8fa6-4ff05697693e>
| 3
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2025-12-25T20:50:12.560200
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arakawa ’ s labs at the university of tokyo. there are currently 30 scientists and engineers involved, including five at the university of tokyo. after its founding, the starta ¿ ¿ up continued to work on boosting the lasers ’ dot density. ” we thought we could keep adding more layers, but we realized that wasn ’ t enough, ” sugawara says. using proprietary techniques, researchers at qd laser and tokyo university eventually succeeded in doubling the dot density, from 30 billion dots per square centimeter to 60 billion. sugawara brings out two atomic - force microscope images of quantum dots. the first shows a sparsely dotted surface. ” everyone can make this density, ” he says. then, pointing to the second image, which is crowded with dots, he says, ” but only we can make this. ” qd laser isn ’ t the first company to bring a quantum - dot laser to market. that distinction belongs to innolume, a start - up based in dortmund, germany, and santa clara, calif. since 2007 it has sold quantum - dot ” comb ” lasers, which can emit tens to hundreds of colors over a range of wavelengths. the devices are potentially suitable for optical computing, laser television, and biomedical applications. but innolume has yet to find a wide market for its products. qd laser will do better because its corporate backers have the muscle to see that it does. fujitsu has already agreed to replace the standard indium - phosphide lasers in its optical networking systems with qd laser ’ s gallium - arsenide lasers. but even fujitsu had to be convinced that the new devices would be as reliable as existing lasers. ” the communications market is very conservative, ” sugawara notes. to make its products more palatable to optical equipment makers like fujitsu, his company spent months tailoring the quantum - dot laser ’ s output power and performance so that they matched those of a conventional laser. the resulting laser can seamlessly replace an indium - phosphide laser in an optical transceiver, with no significant redesign required. with telecom giant nippon telegraph and telephone corp. adding 3 million fiber - to - the - home connections each year, sugawara thinks his company could claim 5 to 10 percent of the japanese market by 2011. qd laser is also working on lasers for long - distance communications of up to 20 kilometers. at press time, the company was wrapping up reliability tests and planned to begin selling in the spring.
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subdomain_quantum_optics
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| 512
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<urn:uuid:39bf3941-13df-439d-8fa6-4ff05697693e>
| 5
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2025-12-25T20:50:12.562522
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green light, you similarly start with a 1064 - nm laser and double the frequency to get a 532 - nm wavelength. quantum - dot lasers could also be used in laser tv sets, medical devices, and tiny portable projectors that fit in your cellphone. in the next couple of decades, arakawa says, we ’ ll see quantum dots showing up in quantum computers and other it devices [ for more on quantum computing, see ” dot to dot design, ” ieee spectrum, september 2007 ]. but why stop there? quantum - dot researchers have been looking at ways to use quantum dots in biochemical sensors, solar cells, and other technologies. it ’ s a future arakawa modestly refers to as ” quantum dots for everything. ” for more articles, go to winners & losers 2009 special report. snapshot : a laser that ’ s right on the dot goal : to commercialize a reliable and inexpensive semiconductor laser that ’ s also immune to temperature changes. why it ’ s a winner : these high - speed, low - power, temperature - stable lasers are equally applicable to optical networking and consumer electronics. who : qd laser, a joint venture of fujitsu and mitsui venture capital corp., and university of tokyo where : tokyo and atsugi, japan staff : 30 scientists and engineers budget : us $ 14 million when : spring 2009
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subdomain_quantum_metrology
| 0.602262
| 276
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<urn:uuid:39bf3941-13df-439d-8fa6-4ff05697693e>
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2025-12-25T20:50:12.564243
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key : " s : " = show synset ( semantic ) relations, " w : " = show word ( lexical ) relations display options for sense : ( gloss ) " an example sentence " - s : ( n ) burning, combustion ( the act of burning something ) " the burning of leaves was prohibited by a town ordinance " - s : ( n ) burn, burning ( pain that feels hot as if it were on fire ) - s : ( n ) combustion, burning ( a process in which a substance reacts with oxygen to give heat and light ) - s : ( n ) electrocution, burning ( execution by electricity ) - s : ( n ) burning, burning at the stake ( execution by fire ) - s : ( n ) burning ( a form of torture in which cigarettes or cigars or other hot implements are used to burn the victim ' s skin ) - s : ( v ) burn, fire, burn down ( destroy by fire ) " they burned the house and his diaries " - s : ( v ) burn, glow ( shine intensely, as if with heat ) " the coals were glowing in the dark " ; " the candles were burning " - s : ( v ) burn, combust ( undergo combustion ) " maple wood burns well " - s : ( v ) bite, sting, burn ( cause a sharp or stinging pain or discomfort ) " the sun burned his face " - s : ( v ) burn, combust ( cause to burn or combust ) " the sun burned off the fog " ; " we combust coal and other fossil fuels " - s : ( v ) burn ( feel strong emotion, especially anger or passion ) " she was burning with anger " ; " he was burning to try out his new skies " - s : ( v ) burn, incinerate ( cause to undergo combustion ) " burn garbage " ; " the car burns only diesel oil " - s : ( v ) burn ( execute by tying to a stake and setting alight ) " witches were burned in salem " - s : ( v ) burn ( spend ( significant amounts of money ) ) " he has money to burn " - s : ( v ) burn ( feel hot or painful ) " my eyes are burning " - s : ( v ) cauterize, cauterise, burn ( burn, sear, or freeze ( tissue ) using a hot iron or electric current or a caustic agent ) " the surgeon cauterized the wart " - s :
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subdomain_quantum_materials
| 0.6035
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:b7d333b6-37c7-4c8d-b36c-b98513ee6cbd>
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| 0.6
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2025-12-25T20:50:12.839136
|
it can be tuned for specific applications. the cation distribution in the ferrite nanoparticles was investigated using x ray absorption ( xa ) and x - ray magnetic circular dichroism ( xmcd ) at the fe l2, 3 and co l2, 3 edges, measured at als beamline 4. 0. 2. an xmcd spectrum is obtained as the difference between two xa spectra measured in opposite external magnetic fields. magnetite has an inverse spinel crystal structure, which contains tetrahedral ( td ) and octahedral ( oh ) sites accommodating fe2 + and fe3 + cations. each specific cation in the spinel structure generates a unique xmcd signature determined by its valence state ( number of d electrons ), site symmetry ( i. e., td or oh ), and moment direction, which can be computed using atomic multiplet calculations. by fitting a weighted sum of these calculated spectra to the measured xmcd spectra, the site occupations of the fe cations can be obtained. the biogenic materials show a striking change with increasing co amount, namely a decrease in intensity of the leading negative peak in the fe l3 edge, which implies that co is predominantly replacing fe2 + cations in octahedral sites. similarly, the site occupancy and oxidation state of the co can be directly assessed by examining the co l2, 3 xa and xmcd spectra. the close similarity with the spectra for synthetically produced cofe2o4 thin films confirmed that the bacteria were able to suitably accommodate co in the ferrite structure with the co2 + residing primarily on oh sites. the xmcd measurements indicate a dramatic enhancement in the magnetic properties of biogenically produced nanoparticles when large quantities of co are introduced into the spinel structure, a major advance over previous biomineralization studies. inclusion of other transition metals into the spinel structure by fe ( iii ) - reducing bacteria to tailor the magnetic properties of nanoferrites could lead to a suite of materials required for different technological uses. the successful production of highly ordered crystalline nanoparticulate ferrites demonstrates the potential for scaled - up industrial manufacture of nanoparticles using environmentally benign and energy - efficient methodologies. research conducted by v. s. coker, n. d. telling, r. a. d. pattrick, c. i. pearce, j. r. lloyd, f. tuna
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subdomain_quantum_materials
| 0.605754
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:b285fa31-c270-460d-bc87-d9f735919786>
| 1
| 0.6
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2025-12-25T20:50:12.877511
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speaker drum or air particles. either way, the signal ends up looking like an erratic wavelike squiggle. but when you listen to the sound produced from that squiggle, you can clearly distinguish all the instruments in a symphony orchestra, playing discrete notes at the same time. that ' s because the erratic squiggle is, effectively, the sum of a number of much more regular squiggles, which represent different frequencies of sound. " frequency " just means the rate at which air molecules go back and forth, or a voltage fluctuates, and it can be represented as the rate at which a regular squiggle goes up and down. when you add two frequencies together, the resulting squiggle goes up where both the component frequencies go up, goes down where they both go down, and does something in between where they ' re going in different directions. the dft does mathematically what the human ear does physically : decompose a signal into its component frequencies. unlike the analog signal from, say, a record player, the digital signal from an mp3 player is just a series of numbers, representing very short samples of a real - world sound : cd - quality digital audio recording, for instance, collects 44, 100 samples a second. if you extract some number of consecutive values from a digital signal - - 8, or 128, or 1, 000 - - the dft represents them as the weighted sum of an equivalent number of frequencies. ( " weighted " just means that some of the frequencies count more than others toward the total. ) the application of the dft to wireless technologies is fairly straightforward : the ability to break a signal into its constituent frequencies lets cell - phone towers, for instance, disentangle transmissions from different users, allowing more of them to share the air. the application to data compression is less intuitive. but if you extract an 8x8 block of pixels from an image, each row or column is simply a sequence of eight numbers - - like a digital signal with eight samples. the whole block can thus be represented as the weighted sum of 64 frequencies. if there ' s little variation in color across the block, the weights of most of those frequencies will be zero or near zero. throwing out the frequencies with low weights allows the block to be represented with fewer bits but little loss of fidelity. demanet points out that the dft has plenty of other applications, in areas like spectroscopy, magnetic resonance imaging, and quantum computing. but ultimately, he says, " it ' s
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subdomain_quantum_metrology
| 0.635837
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:0b27cdae-7df5-46b7-81b6-0cd8f59a6b4d>
| 1
| 0.6
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2025-12-25T20:50:13.406051
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" inexactness " or the " uncertainty " principle, as formulated by physicist werner heisenberg, is an end often seen as the beginning. it reflects t. s. eliot ' s observation : " what she gives, gives with such supple confusions that the giving famishes the craving ". in 1927, heisenberg showed that uncertainty is inherent in quantum mechanics. it is impossible to simultaneously measure certain properties — position and momentum. in the quantum world, matter can take the form of either particle or waves. fundamental elements are neither particles nor waves, but can behave as either and are merely different theoretical ways of picturing the quantum world. the profound beauty of inexactness transects science, mathematics, method, philosophy, linguistics and faith. inexactness marks an end to certainty. in seeking to measure one property more precisely and accurately, the ability to measure the other property is undermined. the act of measurement negates elements of our knowledge of the system. it undermines scientific determinism, implying that human knowledge about the world is always incomplete, uncertain and highly contingent. inexactness challenges causality. as heisenberg observed : " ' if we know the present, then we can predict the future ', it is not the consequences, but the premise that is false. as a matter of principle we cannot know all determining elements of the present ". inexactness questions methodology. experiments can only prove what they are designed to prove. inexactness is a theory based on the practical constraints of measurement. inexactness and quantum mechanics challenge faith as well as concepts of truth and order. they imply a probabilistic world of matter, where we cannot know anything with certainty but only as a possibility. it removes the newtonian elements of space and time from any underlying reality. in the quantum world, mechanics are understood as a probability without any causal explanation. albert einstein refused to accept that positions in space - time could never be completely known and quantum probabilities did not reflect any underlying causes. he did not reject the theory but the lack of reason for an event. writing to max born, he famously stated : " i, at any rate, am convinced that he [ god ] does not throw dice. " but as stephen hawking later remarked in terms that heisenberg would have recognised : " not only does god play dice, but … he sometimes throws them where they cannot be seen. " allusive and subtle, the power
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subdomain_quantum_mechanics
| 0.652789
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:ed736ee9-2a75-4454-81c7-081d914289c1>
| 0
| 0.6
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2025-12-25T20:50:13.457455
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throw dice. " but as stephen hawking later remarked in terms that heisenberg would have recognised : " not only does god play dice, but … he sometimes throws them where they cannot be seen. " allusive and subtle, the power of inexactness draws on its metaphorical property which has allowed it to penetrate diverse fields such as art theory, financial economics and even popular culture. at one level, heisenberg ' s uncertainty principle is taken to mean the act of measuring something changes what is observed. but at another level, intentional or unintentionally, werner heisenberg is saying something about the nature of the entire system — the absence of absolute truths, the lack of certainty and the limits to our knowledge. inexactness is linked with different philosophical constructs. nineteenth - century danish philosopher søren kierkegaard differentiated between objective truths and subjective truths. objective truths are filtered and altered by our subjective truths, recalling the interaction between observer and event central to heisenberg ' s theorem. inexactness is related to linguistic philosophies. in the tractatus logico - philosophicus, ludwig wittgenstein anticipates inexactness arguing that the structure of language provides the limits of thought and what can be said meaningfully. the deep ambiguity of inexactness manifests itself in other ways : the controversy over the term itself and heisenberg ' s personal history. heisenberg ' s principle is various referred to as ungenauigkeit ( meaning inexactness ), unscharfe ( blurred or lacking clarity ) or unbestimmtheit ( indeterminate ). in translation, the ambiguity and differences in meaning are accentuated. playwright michael franyn suggested : indeterminability. it was not until the publication of the 1930 english - language version of heisenberg ' s textbook, the physical principles of the quantum theory that the term uncertainty ( unsicherheit ) was used and widely adopted. in 1941, during the second world war, werner heisenberg and niels bohr, the danish physicist and his former teacher, met in occupied denmark. in michael franyn ' s 1998 play copenhagen, margrethe, bohr ' s wife, poses the essential question, which is debated in the play : " why did he [ heisenberg ] come to copenhagen? " the play repeats their meeting three times, each with different outcomes. as heisenberg, the character
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subdomain_quantum_mechanics
| 0.653812
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:ed736ee9-2a75-4454-81c7-081d914289c1>
| 1
| 0.6
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2025-12-25T20:50:13.458406
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the entire physical universe is made up of pure energy and vibration. when you have the insight to see everything as vibration, the nature of the universe is revealed to you. light is vibration. the entire electromagnetic wave spectrum of visible light produces different colors. colors are simply waves vibrating at different frequencies. on one end of the spectrum you have red, on the other end you have violet. red has the longest wavelength and the lowest frequency, violet has the shortest wavelength and the highest frequency. there are two kinds of electrical lighting that you can find when you visit an electronic store. warm light and cool light. warm light contains a greater mixture of lower frequency color waves such as yellow and orange. cool light contains a greater mixture of higher frequency color waves such as green and blue. light is crucial in its environmental effect upon work, play, rest and other life activities. it controls stimulation, relaxation and energy level. since warm light is more relaxing than cool light, you might decide to use it for the ambience it creates. have you ever used only warm lights in a room and thought that you could make the place more relaxing or stimulating simply by increasing or decreasing the light intensity? but it doesn ’ t work that way. increasing the light intensity of warm light does not make it a lot more stimulating. higher energy levels require higher rate of vibration. it is not the magnitude but the frequency of the vibration that determines it ’ s energy level. is it any wonder that blue flame is hotter than yellow flame? health is vibration. cold, damp and dark places with lack of airflow are breeding grounds for bacteria, whereas sunny places with abundance of airflow eliminate unhealthy micro organisms. the second type of environment is healthier than the first because it is high vibration while the other is low vibration. although sunlight is biologically beneficial, too much of it causes heatstroke. the energy turns from being constructive to destructive. the key here is balance. too much of something beyond the rightful amount causes instability. this is what all sickness and disease does. it seeks to weaken or destabilize vibration. the more vibrant and stable a person is, the more alive and constructive he / she are. the more lackluster and unstable he / she is, the less alive and / or the more ( self ) destructive. ever wonder why you have always been told to drink warm water and not to drink cold one when you were sick? when the body is sick, there are things within that are clogging up the system and slowing
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subdomain_quantum_optics
| 0.659476
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:69d20b89-c15e-4207-9e40-3818e27f33f2>
| 0
| 0.6
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2025-12-25T20:50:14.101484
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bodies ” at every level, physical and non - physical, has a profound influence on our ability to attract positive experiences. the higher your vibration, the more of a “ magnet ” you become as a result of the thoughts you hold in your mind. by holding only thoughts of the “ things ” you wish to manifest into your experience, and keeping your vibrations high in the ways we discussed previously, you will find your wishes will manifest much more quickly. when you learn to see everything as vibration different in terms of rate and stability, you will understand what you need in order to obtain the desired effect in any situation. it is all about balancing vibrations. there are lots more aspects of physical reality than those mentioned here where this principle is applied to. once you are aware of this principle and always think in terms of vibration, you can understand practically everything that happens in the physical world. this is one of the governing dynamics that allows you to make sense of everything. having this awareness is like seeing the world in code, like the matrix. - persistence of will manifests what you desire - affecting probable outcomes with your mind - casting magic spells and intention manifestation - shared reality - cooperative mental creation - actively defend your beliefs against conflict - mentally uniting with your desire by giving thanks for it - speaking your intention gives it more power - letting extremes guide you to balance of mind - purchasing the best things in life for yourself - everything is formed by vibration and geometry
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subdomain_quantum_materials
| 0.606977
| 289
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HuggingFaceFW/fineweb-edu
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<urn:uuid:69d20b89-c15e-4207-9e40-3818e27f33f2>
| 2
| 0.6
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2025-12-25T20:50:14.103315
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an instrument to measure the altitude of an object above a fixed level. generally, mean sea level is used for the reference level. mid - level cloud ( bases generally 2000 - 8000m ), made up of grey, puffy masses, sometimes appearing in parallel waves or bands. an indicatorof mid - level instability. altocumulus can take on various forms such as aclenticularis, ac undulatus, ac castellanus, altocumulus ' mackerel sky '. a middle level cloud with vertical development that forms from altocumulusclouds. it is composed primarily of ice crystals in its higher portions andcharacterised by its turrets, protuberances or crenulated tops. mid - level cloud composed of water droplets and ice crystals. usuallygives the sun a watery or dimly visible appearance. a local wind that flows up the side of valleys due to increased heating alongthe valley walls. often the anabatic wind results in cumulus clouds along theridges either side of the valley. see also katabatic winds. a device used to measure wind speed. the departure of an element from its long - term average for the locationconcerned. for example, if the average maximum temperature for melbourne in june is 14 degrees and on one particular day the temperature only reaches 10 degrees, than the anomaly for that day is - 4. a large scale atmospheric circulation system in which the winds rotate anticlockwise in the southern hemisphere ( clockwise in northern hemisphere ). anticyclones are areas of high atmospheric pressure and are generallyassociated with light winds and stable weather conditions. interchangeablewith high pressure system. rotation in the opposite sense as the earth ' s rotation, i. e., anticlockwise in
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subdomain_quantum_metrology
| 0.630144
| 360
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HuggingFaceFW/fineweb-edu
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<urn:uuid:1f2052ca-130e-43ae-ae93-421e6e25982d>
| 0
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2025-12-25T20:50:14.595862
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ulbrich : glossary abrasion : a roughening or scratching of a surface due to abrasive wear. on aluminum parts, also known as a rub mark or traffic mark. abrasion - resistant steels ( ar ) : a family of steel products developed for those applications involved in sliding and / or impact abrasion. abrasive wear : the removal of material from a surface when hard particles slide or roll across the surface under pressure. the particles may be loose or may be part of another surface in contact with the surface being worn. contrast with adhesive wear. accelerated corrosion test : a test conducted under controlled conditions that are considerably more severe than those natural conditions whose effects are presumably being investigated. the advantages of such a test is the relatively short time required. results are useful for qualitative comparisons, but are not reliable for predicting anticipated life in actual service. accordion reed steel : hardened, tempered, polished and blued or yellow flat steel with dressed edges. carbon content about 1. 00 %. material has to possess good flatness, uniform hardness and high elasticity. acid steel : steel melted in a furnace with an acid bottom and lining and under a slag containing an excess of an acid substance such as silica. acid - brittleness : brittleness resulting from pickling steel in acid ; hydrogen, formed by the interaction between iron and acid, is partially absorbed by the metal, causing acid brittleness. age - hardening : a process of aging that increases hardness and strength and usually decreases ductility. ( see precipitation heat treatment ) air - hardening steel : a steel containing sufficient carbon and other alloying elements to harden fully during cooling in air or other gaseous mediums from a temperature above its transformation range. such steels attain their martensitic structure without going through the quenching process. additions of chromium, nickel, molybdenum and manganese are effective toward this end. the term should be restricted to steels that are capable of being hardened by cooling in air in fairly large sections, about 2 in. or more in diameter. aircraft quality : denotes material for important or highly stressed parts of aircraft for other similar purposes ; such materials are extremely high quality requiring closely controlled, restrictive and special practices in their manufacture. aging : a process generally accelerated by temperature, wherein changes in mechanical properties occur in certain metals. these changes generally raise room temperature hardness, tensile and yield strength, while lowering ductility. aisi : american iron and steel institute. published steel
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subdomain_quantum_materials
| 0.627572
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:b0e5e007-1e3a-4733-9cae-b375addf603a>
| 0
| 0.6
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2025-12-25T20:50:14.881080
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. aging : a process generally accelerated by temperature, wherein changes in mechanical properties occur in certain metals. these changes generally raise room temperature hardness, tensile and yield strength, while lowering ductility. aisi : american iron and steel institute. published steel products manual to stainless and heat resisting steels which provides information concerning tolerances, chemical analysis, definitions of technical terms and other related subjects which have been developed in the manufacture and use of stainless steels. alclad : composite sheet produced by bonding either corrosion - resistant aluminum alloy or aluminum of high purity to base metal of structurally stronger aluminum alloy. the coatings are anodic to the core so they protect exposed areas of the core electrolytically during exposure to corrosive environment. alloy : a material that has metallic properties and is composed of two or more chemical elements of which at least one is a metal ( i. e. steel is an alloy of carbon in iron ; stainless steel is an alloy of carbon, chromium and sometimes nickel in iron. ) alloying elements : those elements in alloys which are deliberately added during melting and refining to enhance the properties of that alloy. alloy steel : an iron - based mixture is considered to be an alloy steel when manganese is greater than 1. 65 %, silicon over 0. 5 %, copper above 0. 6 %, or other minimum quantities of alloying elements such as chromium, nickel, molybdenum, or tungsten are present. an enormous variety of distinct properties can be created for the steel by substituting these elements in the recipe. alpha brass : a copper - zinc alloy containing up to 38 % of zinc. used mainly for cold working. alpha bronze : a copper - tin alloy consisting of the alpha solid solution of tin in copper. commercial forms contain 4 or 5 % of tin. this alloy is used in coinage, springs, turbine, blades, etc. alpha iron : the polymorphic form of iron, stable below 1670°f, has a body centered cubic lattice, and is magnetic up to 1410°°f. aluminizing : forming an aluminum or aluminum alloy coating on a metal by hot dipping, hot spraying, or diffusion. annealing : a process involving heating to a temperature at or above critical and cooling at a controlled rate, usually applied to induce softening. the process could alter mechanical properties, physical properties or micro structure. anodizing : ( aluminum adic oxide coating ) a process of coating aluminum by anodic treatment resulting in a thin film of
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subdomain_quantum_materials
| 0.680541
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:b0e5e007-1e3a-4733-9cae-b375addf603a>
| 1
| 0.6
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2025-12-25T20:50:14.882033
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aluminum standards and data provides definitions for welding and brazing : welding is the " joining of two or more pieces of aluminum by applying heat or pressure, or both, with or without filler metal to produce a localized union through fusion or recrystallization across the interface ". brazing is the " joining of metals by fusion of nonferrous alloys that have melting points above 425 degrees c ( 800 degrees f ) but lower than those of the metals being joined. this may be accomplished by means of a torch ( torch brazing ), in a furnace ( furnace brazing ), or by dipping a molten flux bath ( dip or flux brazing ). " according to the asm specialty handbook : aluminum and aluminum alloys : " brazing, by definition, employs filler metal having a liquidus above 450 degrees c ( 840 degrees f ) and below the solidus of the base metal. brazing is distinguished from soldering by the melting point of the filler metal : solders melt below 450 degrees c ( 840 degrees f ). brazing differs from welding in that no substantial amount of the base metal is melted during brazing. thus the temperatures for brazing aluminum are intermediate between those for welding and soldering. also, brazed aluminum assemblies generally are between welded and soldered assemblies in strength and resistance to corrosion " since soldering is done below 450 degrees c ( 840 degrees f ), aluminum filler alloys are not used in soldering aluminum. instead, solders for aluminum alloys are often zinc, tin, cadmium and lead.
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subdomain_quantum_materials
| 0.622923
| 314
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HuggingFaceFW/fineweb-edu
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<urn:uuid:f049bcb0-e1fe-4191-b6bb-715b491d5a7b>
| 0
| 0.6
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2025-12-25T20:50:15.079573
|
learn something new every day more info... by email information traveling across a computer network or another type of telecommunications network typically comes in packets. packets are smaller, " bite - sized " pieces of a larger chunk of information. although telecommunication technology is generally reliable and seamless from the end - user ' s point of view, that is only because the computer does the dirty work. it constantly sifts through the packets, looking for fraudulent and corrupt data, discarding it when found. a burst error is a string of corrupt data, measured as the length between — and including — the first and last error signals. for example, imagine sending a packet containing all of the letters of the alphabet, a through z. if the recipient ' s computer " opens " the packet and finds that the first letter in the sequence is " q " and the last letter in the sequence is " r, " that is a burst error. the " burst " of data in the packet is corrupt. although in the example the first and last letters are defined as corrupt, that does not mean that every letter within the packet is damaged. imagine that every other letter is as it should be ; only position one, " a, " and position 26, " z, " have been damaged. the number of correct bits of information between the damaged ends is called the guard band. in this case, the guard band would be 24, because there are 24 correct letters separating the two damaged ones. measuring the length of a burst error is simple. it is defined as the number of individual bits separating the very first occurrence of the error from the last occurrence, including the initial and final incorrect bits. in the previous example, the length of the burst error would be 26. the causes of a burst error can vary widely. it is not always possible to measure them accurately. generally, this corruption can occur through any number of sources, including signal degradation, packet loss, other types of network failure, or sending failure on the part of the computer. in networking, as in the real world, sometimes things go wrong. fortunately, most forms of networking provide built in error - checking mechanisms, allowing a receiving computer to compare the actual received data against an impression of the data that was sent, allowing it to recognize whether something has gone wrong along the way.
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subdomain_quantum_cryptography
| 0.617335
| 468
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HuggingFaceFW/fineweb-edu
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<urn:uuid:387c10d5-b18a-4363-880e-d1cc5b368edd>
| 0
| 0.6
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2025-12-25T20:50:15.257585
|
what we perceive in the world is highly influenced by what we are looking for. that is old news. now european researchers have used this theory to create a convincing and engaging ‘ mixed reality ‘, and they have put together a cookbook so others can do it, too. that is new news. reality is wysiwyg : what you see is what you get. but what you see depends largely on what you are looking for. in a famous experiment, a group of volunteers observed a video of two teams, one dressed in black and one in white, passing a ball between them. the volunteers had to count the number of times the ball was passed directly from one player in black to another player in black. they performed the task excellently. what they failed to notice was the man in the gorilla suit who walked on screen and jumped up and down during the game. it proved that what you see is strongly influenced by what you are looking for. in ophthalmology, researchers have found the eye does not see everything you perceive ; neural processing fills in parts of the scene by inferring from those bits that are observed. in quantum physics, researchers discovered that particles change behaviour depending on whether you are looking at them or not. in field after field researchers have discovered that perception is not linear ; it is fuzzy ; and it can be strongly influenced by carefully choosing the right cues. the cues do not necessarily require complex technology. the wii, a very popular gaming platform, abandoned the arms race of ever - more powerful processors and graphics cards and instead incorporated a simple motion sensor. now users ' gestures and reflexes drive the game, changing the pastime from a solitary, passive experience into an active, social one. those two additions, sociability and physicality, dramatically enhance the sense of experienced reality engendered by the game. this is very interesting. up to now technologies, such as virtual and mixed reality, were thought by most to rely on more power, more technologically advanced interfaces, more animation and textures ; but it now seems mixed reality is more powerfully and realistically evoked by combining perceptual dimensions with novel technologies in order to create a greater depth of experience. “ the greater the combination of senses engaged, the greater the chance of the user feeling immersed or present in the experience, ” explains rod mccall, a researcher at the fraunhofer institute and coordinator of the ipcity project. in ipcity, a major eu - funded mixed reality project, researchers studied dozens of technologies to find
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subdomain_quantum_optics
| 0.618286
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:ce8edb2f-38e3-4b9c-b541-ad6a4ce07fd5>
| 0
| 0.6
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2025-12-25T21:10:54.511818
|
light scattering system nanobiophysics core facility has a full set of light scattering equipment from wyatt including multiangle light scattering ( mals ) device, dynamic light scattering ( dls ) device, and hplc system ( agilent ) linked to mals. light scattering is a non - invasive technique for characterizing macromolecules and a wide range of particles in solution. in contrast to most methods for characterization, it does not require outside calibration standards. in this sense it is an absolute technique. wyatt technology instruments make two different types of light scattering measurements for absolute molecular characterization : * classical light scattering : here, the intensity of the scattered light is measured as a function of angle. for the case of macromolecules, this is often called rayleigh scattering and can yield the molar mass, rms radius, and second virial coefficient ( a2 ). for certain classes of particles, classical light scattering can yield the size, shape, and structure. * quasi - elastic ( qels ) or dynamic light scattering ( dls ) : in a qels measurement, time - dependent fluctuations in the scattered light signal are measured using a fast photon counter. qels measurements can determine the hydrodynamic radius of macromolecules or particles. light scattering is a technique that can be applied in either batch or chromatography mode. in either instance the sample may be recovered at the end of the measurement. since light scattering provides the weight - averaged molar mass for all molecules in solution, it is generally more useful to utilize the chromatography mode, though each technique has its advantages. although absolute molecular weights can be determined also via mass spectrometry, membrane osmometry, and sedimentation equilibrium ( analytical centrifugation ), only light scattering covers so broad a range of macromolecules including their oligomeric states. most importantly, light scattering permits measurement of the solution properties of macromolecules. while a sedimentation equilibrium run may require 72 hours, a size exclusion chromatography / light scattering study may be completed in well under an hour, and a batch mode analysis in a few minutes. these comparatively short run times coupled with the absolute determination of molar mass, size, and a2 make light scattering the method of choice for accurate and fast macromolecular characterization. for more information go to www. wyatt. com core facility will help you with obtaining free downloads of manuals, tutorials and software.
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subdomain_quantum_metrology
| 0.617906
| 505
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HuggingFaceFW/fineweb-edu
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<urn:uuid:383315da-e20e-4bfd-8cad-7c0c4da0230a>
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2025-12-25T21:10:54.538350
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a concept defined by sartre in being and nothingness as the " in - itself ", of which humans are in the mode of not being. this can be more easily understood when considering it in relation to the temporal dimension of past : one ' s past is what one is in the sense that it co - constitutes oneself. however, to say that one is only one ' s past would be to ignore a significant part of reality ( the present and the future ), while saying that one ' s past is only what one was, would entirely detach it from them now. a denial of one ' s own concrete past constitutes an inauthentic lifestyle, and the same goes for all other kinds of facticity ( having a body — e. g. one that doesn ' t allow a person to run faster than the speed of sound — identity, values, etc. ). facticity is both a limitation and a condition of freedom. it is a limitation in that a large part of one ' s facticity consists of things one couldn ' t have chosen ( birthplace, etc. ), but a condition in the sense that one ' s values most likely will depend on it. however, even though one ' s facticity is " set in stone " ( as being past, for instance ), it cannot determine a person : the value ascribed to one ' s facticity is still ascribed to it freely by that person. as an example, consider two men, one of whom has no memory of his past and the other remembers everything. they have both committed many crimes, but the first man, knowing nothing about this, leads a rather normal life while the second man, feeling trapped by his own past, continues a life of crime, blaming his own past for " trapping " him in this life. there is nothing essential about his committing crimes, but he ascribes this meaning to his past. however, to disregard one ' s facticity when one, in the continual process of self - making, projects oneself into the future, would be to put oneself in denial of oneself, and would thus be inauthentic. in other words, the origin of one ' s projection will still have to be one ' s facticity, although in the mode of not being it ( essentially ). another aspect of facticity is that it entails angst, both in the sense that freedom " produces " angst when limited by facticity, and in the sense that the lack
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subdomain_quantum_mechanics
| 0.615285
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:4a11b0a2-0262-4b69-9d8a-f6d2255053f1>
| 4
| 0.6
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2025-12-25T21:10:54.655321
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coupled with its environment seems to be sufficient to make claims. the flow of internal states in such system, guided and limited by associative memory, is similar to the stream of consciousness. minimal requirements for an artificial system that will claim to be conscious were given in form of specific architecture named articon. (... ) nonverbal discrimination of the working memory states of the articon gives it the ability to experience different qualities of internal states. analysis of the inner state flows of such a system during typical behavioral process shows that qualia are inseparable from perception and action. the role of consciousness in learning of skills, when conscious information processing is replaced by subconscious, is elucidated. arguments confirming that phenomenal experience is a result of cognitive processes are presented. possible philosophical objections based on the chinese room and other arguments are discussed, but they are insufficient to refute claims articon ’ s claims. conditions for genuine understanding that go beyond the turing test are presented. articons may fulfill such conditions and in principle the structure of their experiences may be arbitrarily close to human. ( shrink ) this paper speculates upon the reasons for peter drucker ' s ongoing and vigorous denial of the relevance of business ethics. it contemplates whether drucker consciously, or even perhaps subconsciously, associates the aims of business ethics with the aims of those associated with the arbeitsfreude movement in germany prior to the outbreak of the second world war. if this is the case the paper questions whether drucker ' s distaste for some of the more notorious outcomes of that movement in germany are reflected in (... ) his hostility to business ethics. drucker ' s reflections regarding the social responsibilities of business are discussed, as are the limitations which he imposes upon such corporate social responsibility. drucker ' s distinction between societal ethics and individual ethics are also discussed. ( shrink ) this paper evaluates the claim that it is possible to use nature ’ s variation in conjunction with retention and selection on the one hand, and the absence of ultimate groundedness of hypotheses generated by the human mind as it knows on the other hand, to discard the ascription of ultimate certainty to the rationality of human conjectures in the cognitive realm. this leads to an evaluation of the further assumption that successful hypotheses with specific applications, in other words heuristics, seem to (... ) have a firm footing because they were useful in another
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subdomain_quantum_mechanics
| 0.603347
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:5608ec65-3b09-4b1c-a3ca-d563c5e0d570>
| 12
| 0.6
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2025-12-25T21:10:55.399595
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into believing in less. although i think that flanagan ' s attempt to link the psychological and sociocultural levels of analysis via the concept of transcendence is scientifically premature, his attempt at a naturalistic spirituality raises questions of definition that scholars of religion need to take seriously. ( shrink ) in this article, i discuss the manner in which dieter henrich ’ s theory of subjectivity has emerged from the fundamental questions of german idealism, and in what manner and to what extent this theory effects a reinstatement of metaphysics. in so doing, i shall argue that henrich ’ s position represents a viable refutation of the attempt of the physicalist explanation of the world to prove the concept of the subject to be superfluous. henrich ’ s metaphysics of subjectivity is primarily focused on the ‘ ultimate (... ) questions ’ which also compose “ the deep levels of our subjectivity ” and concern the factors that should promote stability in our emotional, moral and intellectual life. i argue with henrich that the indisputable facticity of our conscious life is worthy of our special consideration and interpretation, explanation and clarification, just as the deeper meaning ( the individual and collective subconscious structure ) hidden beneath the layers of apparent comprehensibility calls for urgent investigation. such interpretation and elucidation of life ’ s meaning has a tripartite character : first, it consists of clarification of the totality of human experience together with the realities playing a part in it ; second, it builds on the process by which the contents of experience are cognized, and the knowledge thereof which results ; thirdly, it embraces the transcendental precondition enabling each and every one of us to consciously lead our lives — for life, in a human sense, does not merely happen to one. henrich ’ s metaphysical foundation of subjectivity is compared with kolak ‘ s position, according to which individual consciousness is not insular, but integrated into the totality of overall unity that some have called “ the universal self ”, “ the noumenal self ”. ( shrink ) there are a number of reasons to be interested in building humanoid robots. they include ( 1 ) since almost all human artifacts have been designed to easy for humans to interact with, humanoid robots provide backward compatibility with the existing human constructed world, ( 2 ) humanoid robots provide a natural form for humans to operate through telepresence since they have the same kinematic design as humans themselves, ( 3 ) by
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subdomain_quantum_field_theory
| 0.615372
| 512
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:5608ec65-3b09-4b1c-a3ca-d563c5e0d570>
| 16
| 0.6
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2025-12-25T21:10:55.406073
|
the scene : scientist jian chen adjusts optics mounted for an experiment at one of several pulse laser laboratories housed at slac. ( pulse is a joint slac / stanford university laser science institute. ) in this experiment, a small fleck of sample material is held in a special “ diamond anvil cell ” and torqued to pressures up to 12 gigapascals — 120, 000 times greater than atmospheric pressure, similar to conditions deep inside the earth. chen and colleagues then use three separate, highly precise beams of pulsed laser light, bouncing variously through the specialized optics, to measure the behavior of electrons in the material under pressure. experiments of this sort give scientists clues about the nature and dynamics of the atomic world that could aid in developing new materials with exotic properties. the shot : canon 5d mk ii, 17 - 35mm / f2. 8l lens @ 17mm, f / 7. 1. iso 200, 1 / 40 sec exposure. three lights ( all speedlites ), one triggered with a pocket wizard ii, the others with optical slaves : one camera left ( close, with a red gel ), one camera right ( at full power, to cast the hard shadows ), and one camera left ( farther from the camera, with grid, visible in frame ) to illuminate chen. used a tripod and remote trigger for this one. ( all while wearing the same goggles chen is wearing … tough way to shoot! )
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subdomain_quantum_optics
| 0.62317
| 295
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HuggingFaceFW/fineweb-edu
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<urn:uuid:aa900d17-ee05-43a1-9828-f3db9c23769c>
| 0
| 0.6
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2025-12-25T21:10:55.473871
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mobility / stability statistics for 2011 - 2012 definitions of terms used the total ( cumulative ) number of students in membership at any time during the academic year. instructional program service type ( ipst ) : services provided by schools and / or districts for students identified as belonging to one or more of the categories below. students with disabilities : students who have been formally identified as having physical or health conditions that may have a significant impact on the student ’ s ability to learn and therefore warrant placing the student on an individual educational program ( iep ). limited english proficient : this designation encompasses all students identified as either non - english proficient or limited english proficient. non - english proficient is defined as a student who speaks a language other than english and does not comprehend, speak, read, or write english. limited english proficient is defined as a student who comprehends, speaks, reads, or writes some english, but whose predominant comprehension or speech is in a language other than english. districts must provide language services to all limited english proficient students. student qualifies for either the free or reduced lunch program. the federal national school lunch act establishes eligibility for the reduced price lunch program for families with income up to 185 percent of the federal poverty level ( in 2009, this amount was $ 39, 220 for a family of four ). families with income up to 130 percent of the federal poverty level qualify for the free lunch program ( in 2009 this amount was $ 27, 560 for a family of four ). students enrolled in a specially designed program for children who are, or whose parent or spouse is a migratory agricultural worker, and who, in the preceding 36 months, in order to obtain, or accompany such parent or spouse in order to obtain, temporary or seasonal employment in agricultural work has moved from one school district to another. students that are identified by the school as failing, or most at risk of failing, to meet the state ’ s challenging student academic achievement standards on the basis of multiple, educationally related, objective criteria established by the school. according to the mckinney act, a “ homeless individual ” : lacks a fixed, regular, and adequate nighttime residence. gifted and talented : students who have been formally identified, using district - wide procedures aligned with cde guidelines, as being endowed with a high degree of exceptionality or potential in mental ability, academics, creativity, or talents ( visual, performing, musical arts, or leadership. for additional information, e - mail :
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subdomain_quantum_materials
| 0.606563
| 494
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HuggingFaceFW/fineweb-edu
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<urn:uuid:78bbb2d7-43c3-4072-b7ea-bb86a3593f19>
| 0
| 0.6
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2025-12-25T21:10:55.957731
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about seven years ago, a brain scientist was working with primate brain signals three floors underground. the scientist was using special neurological amplifiers that amplified micro - volt signals. he called me to solve a strange, sporadic noise problem that had appeared in his amplifier outputs. his laboratory had been in operation for many years before this problem appeared. when confronted with a mysterious problem, i always ask one particular question : " what is changed, what is different? " but in this case, the answer was nothing. connecting up a scope, i soon saw a signal on the screen that coincided with a noise from a speaker connected to a neural amplifier output. we heard a distinctive " click ” sound. by slowing the horizontal time period to one second / division, we could see the entire several - millisecond - long noise pulse. but this was no ordinary noise pulse - - it was actually a perfect bipolar square wave. envision a single period of a full sine wave on a scope screen, then convert that same wave pattern to fit a bipolar square wave. that ' s exactly what it was. every few seconds it appeared, but each time, the starting and ending polarity was flipped. there was no question this was an intelligently generated signal - - but from where? soon, a pattern was discernible. pulse spacing was a consistent 5. 5 seconds. remember, this laboratory was about 60 feet underground. the building had corrugated steel plates as the base, with three reinforced concrete floors up above. line of sight with the local radar dish required that you travel through wet dirt, steel, rock, and reinforced concrete for about two miles at a slight upward angle to reach the local airport dish. and microwaves will not travel through any of these materials very well. certain types of microwave sources contain a property few engineers know about - - scalar energy. scalar electromagnetic waves have the e and b fields in phase, unlike normal electromagnetic waves where e and b fields are typically 90 degrees out of phase. there is another interesting characteristic of scalar waves - - they are not stopped by shielding, even by a faraday cage. when e and b fields are in phase, they do not interact with metal molecules like conventional rf does, which makes shielding useless. usually, only distance can stop scalar waves. based on the waveform period, there could be only one source of this signal. i called the local international airport tracon group, which stands for tracking and control. my one question to the engineer on duty was simply this
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subdomain_quantum_optics
| 0.624478
| 512
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:d693ac58-a8f8-4e56-b0ae-f9ef0568c695>
| 0
| 0.6
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2025-12-25T21:10:56.059344
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a user - interface for proofs and certified software by janet bertot, yves bertot, yann coscoy, healfdene goguen and francis montagnac by making it possible to express the properties of procedures and functions, proofs assistants can be used to help develop certified software. however, these proof assistants are often complicated to use and deserve real user - interfaces to make software development feasible. since 1990, the croap team at inria sophia - antipolis has been studying the development of user - interfaces for theorem provers to reduce this level of complication. we have implemented a powerful prototype, ctcoq, that has been used successfully in the development of certified algorithms for program manipulation or polynomial mathematics. the last version of this proof environment has been released in february 1997. the semantics of programs can be mathematically described using relations between inputs and outputs or using functions from the domain of inputs to the domain of outputs. when these relations and functions are formally described, it is possible to use a computer to check mechanically some of their properties. this leads to the perspective of checking that programs fulfil a formal specification and ultimately to zero - default software. since the correction of a given program may rely on an arbitrarily complex corpus of mathematics, the system used for the verification needs to have very powerful proving capabilities. to date, only the systems known as theorem provers or proof checkers provide enough mathematical capabilities for this task. the coq proof assistant is one such proof checker ( see previous article ). it uses type theory to express the properties of functions and encode powerful mathematical tools such as recursion and algebraic structures. intuitively, the types used in a programming language like pascal or c make it possible to verify simple consistency properties between the components of a software. when using language with more expressive types, the properties that can be expressed using types can actually cover the complete specification of a software system. the ctcoq user - interface is an independent front - end for the coq proof assistant. it uses technologies from the domain of programming environments to help the proof developer in several ways. the first element taken from programming environment technology is the use of syntax directed tools. these tools use a precise description of the proof assistant ' s syntax to help in the rapid construction of syntactically correct logical sentences, specifications, and proof commands. for instance, syntax directed menus make it possible to perform transformations on expressions or commands that respect the syntactic correctness of these expressions, thus
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subdomain_quantum_computing
| 0.613842
| 512
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:a67667a3-9a44-48a3-9476-dff878b94636>
| 0
| 0.6
|
2025-12-25T21:10:56.174808
|
help in the rapid construction of syntactically correct logical sentences, specifications, and proof commands. for instance, syntax directed menus make it possible to perform transformations on expressions or commands that respect the syntactic correctness of these expressions, thus reducing the time spent in correcting low - level errors. syntax aware tools also make it easier to recognize usual mathematical notations and render them using multiple - font display, in a wysiwyg fashion. these tools make semantic manipulation of data possible, with interpretation of the user ' s pointing or dragging gestures using the mouse. for instance, pointing at an expression can be interpreted guiding the proof process towards this expression. in the same realm, dragging an expression can be used to rearrange data when the algebraic properties make it possible. other tools taken from programming environments use the analysis of dependence graphs between functions, mathematical objects, and proof commands. this analysis can lead to quicker tools to help finding and correcting errors in specifications, thus making the development of completely proved software quicker. powerful analyses also make it possible to extract natural language presentation from proofs data structures, thus making the results of proof developments understandable by mathematicians and engineers outside the community of coq and ctcoq users. the ctcoq proof environment has been used successfully in the development of algorithms for symbolic computation, trajectory planning, and program partial evaluation. future research around this user - interface aims on one side at a better integration with symbolic computation and computer algebra systems and on the other side at a better use of dependency graphs to make large proof maintenance and re - engineering feasible. publication references for this research can be found at : http : / / www. inria. fr / croap / publications. html the ctcoq system can be retrieved by following the instructions found at : http : / / www. inria. fr / ctcoq / ctcoq - eng. html yves bertot - inria tel : + 33 4 9365 7739
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subdomain_quantum_computing
| 0.612141
| 402
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HuggingFaceFW/fineweb-edu
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<urn:uuid:a67667a3-9a44-48a3-9476-dff878b94636>
| 1
| 0.6
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2025-12-25T21:10:56.175646
|
mind whose nature is to think and a material body whose nature is to be spatially extended causally interact? – no longer arises. moreover, many philosophers even reject huxley ’ s event - dualism in favor of psychophysical event - identities. according to one version of non - reductive physicalism, for instance, every concrete mental event ( every event token ) is identical to a concrete physical event, although there are no one - one correlations between mental and physical properties ( event types ). since fear is identical to the neurophysiological event which causes the increased heart rate, fear causes the increased heart rate, too, and epiphenomenalism seems avoided. however, the charge of epiphenomenalism re - arises in a different guise. there is a forceful intuition that events cause what they cause in virtue of some of their properties. suppose a soprano sings the word “ freedom ” at a high pitch and amplitude, causing a nearby window to shatter. the singing which causes the shattering is both the singing of a high c and the singing of the word “ freedom. ” intuitively, only the former, not the latter, is causally relevant for the singing ’ s causing the shattering : “ meaningful sounds, if they occur at the right pitch and amplitude, can shatter glass, but the fact that the sounds have meaning is irrelevant to their effect. the glass would shatter if the sounds meant something completely different or if they meant nothing at all ” ( dretske 1989, 1 - 2 ). if events cause their effects in virtue of some of their properties but not in virtue of others, the question arises whether mental events ( even if they are identical to physical events ) cause their effects in virtue of their mental, their physical or both kinds of properties. if mental events cause their effects only in virtue of their physical properties, then their being mental events is causally irrelevant and mental properties are, in a certain sense, epiphenomena ( three reasons for thinking that mental properties are causally irrelevant are discussed in section 4b ). following brian mclaughlin, one can thus distinguish between event - or token - epiphenomenalism on the one hand and property - or type - epiphenomenalism on the other ( see mclaughlin 1989, 1994 ). according to the event - or token - epiphenomenalism defended by huxley, concrete physical events are causes, but mental events cannot cause anything. according to the kind of property - or type - epip
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subdomain_quantum_mechanics
| 0.608364
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:bc08d6f0-964c-4257-b3be-da849d757dd4>
| 4
| 0.6
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2025-12-25T21:10:56.542261
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mclaughlin 1989, 1994 ). according to the event - or token - epiphenomenalism defended by huxley, concrete physical events are causes, but mental events cannot cause anything. according to the kind of property - or type - epiphenomenalism that threatens modern non - reductive physicalism, events are causes in virtue of their physical properties, but no event is a cause in virtue of its mental properties. if event - epiphenomenalism is wrong, mental events can be causes ; but if they are causes solely in virtue of their physical properties, property - epiphenomenalism is still true, and some consider this to be no less disconcerting than huxley ’ s original epiphenomenalism ( see arguments in favor of a philosophical theory typically focus on its advantages compared to other theories — that it can explain more phenomena or that it provides a more economical or a more unifying explanation of the relevant phenomena. there are no arguments for epiphenomenalism in that sense. epiphenomenalism is just not an attractive or desirable theory. rather, it is a theory of last resort into which people are pushed by the feeling that all the alternatives are even less plausible. even epiphenomenalists admit that, from the first - person point of view of a thinking and feeling subject, they don ’ t like it. why, then, do people embrace epiphenomenalism? epiphenomenalism required an intellectual climate in which two apparently discordant beliefs about the world were equally well entrenched : a dualism with respect to mind and body on the one hand and a scientific naturalism or mechanism concerning the body on the other. to most thinkers of the eighteenth and nineteenth century, it seemed obvious that human beings enjoy a mental life that resists incorporation into a purely materialist ontology. our thoughts, sensations, desires etc. just seemed to be too dissimilar from ordinary physical phenomena for them to be “ nothing but ” physical phenomena. at the same time, however, science saw the advent of a decidedly naturalistic attitude towards the human body, motivated by the successes of mechanistic physics in other areas and characterized by a desire to identify the underlying causal structure of every observed phenomenon in terms of matter and motion alone. in particular, neurophysiological research was unable to reveal any mental influence upon the brain or the body. eventually, with the demise of vitalism regarding the forces governing animate
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subdomain_quantum_mechanics
| 0.607844
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:bc08d6f0-964c-4257-b3be-da849d757dd4>
| 5
| 0.6
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2025-12-25T21:10:56.543282
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contrast, ( 2 ) and ( 3 ) concern laws. since “ laws are linguistic ” ( davidson 1970, 215 ) and thus an intensional affair, particular events fall under laws “ only as described. ” ( 2 ) says that whenever two events c and e are related as cause and effect, there are descriptions “ dc ” and “ de ” of c and e, respectively, under which c and e instantiate a causal law, although there may be descriptions “ d * c ” and “ d * e ” under which they do not instantiate a causal law ( although “ d * c caused d * e ” is nevertheless a true singular causal statement ). given this, it is easy to see why davidson thinks that ( 1 ), ( 2 ), and ( 3 ) entail that mental events which causally interact with other events must be identical to physical events. by ( 1 ), some mental event m causes or is caused by a physical event p. by ( 2 ), m and p must therefore instantiate a strict causal law. that is, there must be descriptions “ dm ” and “ dp ” of m and p, respectively, such that “ dm - events cause dp - events ” ( or “ dp - events cause dm - events ” ) is a strict causal law. by ( 3 ), this can only be a physical law. hence, “ dm ” and “ dp ” must belong to the vocabulary of physics. since events are mental or physical “ only as described ” and since m has with “ dm ” at least one physical description, m must thus be a physical event ( davidson 1970, 224 ). however, while causation may admittedly be an extensional relation between particular events, many philosophers have argued that which causal relations an event enters into is determined by which event - types it falls under. the singing ’ s being the singing of a high c, it seems, is causally relevant for its causing the shattering, while its being the singing of the word “ freedom ” is not. according to anomalous monism, davidson ’ s critics claim, only the strict laws of physics can be causal laws, and hence events seem to be causally related only in virtue of falling under physical event - types, rendering mental event - types causally irrelevant : davidson ’ s argument for anomalous monism shows that any causal relation involving a mental event and a physical event holds only because a strict physical law subsumes the two events
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subdomain_quantum_optics
| 0.627069
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:bc08d6f0-964c-4257-b3be-da849d757dd4>
| 9
| 0.6
|
2025-12-25T21:10:56.548598
|
physical event - types, rendering mental event - types causally irrelevant : davidson ’ s argument for anomalous monism shows that any causal relation involving a mental event and a physical event holds only because a strict physical law subsumes the two events under physical kinds or descriptions. the fact that the mental event is a mental event, or that it is the kind of mental event that it is, appears to be entirely immaterial to the causal relation. [... ] individual mental events [... ] do have causal efficacy, but only because they fall under physical kinds, and the mental kinds that they are have [... ] nothing to say about what causal relations they enter into. the causal structure of the world is wholly determined by the physical kinds and properties instantiated by events of this world. ( kim 2003b, 126 ) this is a prominent objection against anomalous monism ( see, for example, honderich 1982 ; kim 1989a, 1993a ; sosa 1993 ). anomalous monism may avoid token - or event - physicalism, but it seems to succumb to type - or property - epiphenomenalism : mental events, by being identical to physical events, are causally efficacious, but that they are the kind of mental event they are adds nothing to their causal efficacy ( for responses on behalf of anomalous monism see campbell 1997, 1998 ; davidson 1993 ; lepore & loewer 1987 ; mclaughlin 1989 ). anti - individualism or externalism holds that the content of mental states and the meaning of some natural language terms is a relational, or extrinsic, rather than a local, or intrinsic, property ( see burge 1979 ; putnam 1975 ). what are local or relational properties? suppose sarah weighs 110 pounds, is four foot five, has blond hair and is taller than jack. the first three properties seem to be local in the sense that they supervene upon sarah ’ s internal make - up and sarah can acquire or loose them only if she herself undergoes some change. the fourth property, in contrast, seems to be relational in the sense that sarah has it only by courtesy of certain external facts, namely, only if there is someone else, jack, who is smaller than she is. if jack grows tall enough, sarah loses the property of being taller than jack, although she herself does not undergo any change. according to hilary putnam, meanings of natural kind terms are relational properties ( see putnam 1975
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subdomain_quantum_mechanics
| 0.615281
| 512
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:bc08d6f0-964c-4257-b3be-da849d757dd4>
| 10
| 0.6
|
2025-12-25T21:10:56.549698
|
, who is smaller than she is. if jack grows tall enough, sarah loses the property of being taller than jack, although she herself does not undergo any change. according to hilary putnam, meanings of natural kind terms are relational properties ( see putnam 1975 ). what sarah means by an utterance of, say, “ water, ” “ tiger, ” “ elm, ” or “ gold ” is not determined solely by her internal make - up, but also by her environment. consequently, such terms can mean different things in the mouth of molecularly identical twins that are indistinguishable with regard to their local properties. meanings “ just ain ’ t in the head, ” as putnam famously put it. moreover, the contents of the corresponding thoughts seem to be relational properties, too : what sarah believes when she has a belief she would express as, say, “ water is wet ” is determined by the way the world is and not solely by how things are “ inside ” her. tyler burge went even further and argued that natural kind terms are not the only terms whose meaning is determined by external factors and that not only differences in the physical environment can affect the meaning of a term or the content of a belief, but also differences in a subject ’ s historical, linguistic, or social environment ( see burge 1979 ). externalism or anti - individualism makes mental causation problematic. causality seems to be an entirely local affair in the sense that a system ’ s behavior apparently supervenes upon its internal make - up. consequently, two systems exactly alike in all internal respects will behave in exactly the same way, so that relational properties like being a genuine dollar coin or being a photo of sarah do not seem to make a difference to the behavior of, say, a vending machine or a scanner : as long as the piece of metal inserted into a vending machine has a certain set of local properties, the vending machine will exhibit a certain behavior, no matter whether the piece of mental inserted is a genuine dollar coin or a counterfeit, and a scanner will produce a certain distribution of pixels on the screen, no matter whether the object scanned is a photo of sarah or a piece of paper locally indistinguishable from a photo of sarah. the assumption that causation is a local affair, when combined with externalism or anti - individualism, leads to epiphenomenalism : the meaning or content of a mental state, being a relational property, threatens to be as irrelevant for our
|
subdomain_quantum_materials
| 0.646698
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:bc08d6f0-964c-4257-b3be-da849d757dd4>
| 11
| 0.6
|
2025-12-25T21:10:56.550910
|
that causation is a local affair, when combined with externalism or anti - individualism, leads to epiphenomenalism : the meaning or content of a mental state, being a relational property, threatens to be as irrelevant for our behavior as the property of being a genuine dollar coin is for the behavior of a vending machine. in order to avoid epiphenomenalism, we must either eschew anti - individualism or show how relational mental properties can make a causal difference. jerry fodor tried to explicate a notion of “ narrow content ” according to which the mental states of intrinsically indistinguishable subjects must have the same contents, although their relationally individuated “ wide contents ” may differ ( see fodor 1987, ch. 1, 1991 ). since narrow contents supervene upon the intrinsic make - up of a subject, fodor held, the charge of epiphenomenalism can be avoided. however, he has recently given up on this idea because it proved extremely difficult to say exactly what narrow contents are ( see fodor 1995 ). frank jackson and philip pettit argue that relational properties can be causally relevant in virtue of figuring in so called “ program explanations, ” although strictly speaking the causal work is done solely by local properties ( see, for example, jackson & pettit 1990 ). in a similar vein, lynne rudder baker and tyler burge claim that the charge of epiphenomenalism “ just melts away ” ( baker 1993, 93 ) if we acknowledge that our explanatory practice which undoubtedly treats explanations in terms of relational properties as causal explanations trumps any metaphysical armchair argument to the contrary ( see baker 1993, 1995 ; burge 1993 ). and fred dretske argues that while the triggering causes of behavior are always local, relational mental properties can make a causal difference in virtue of being structuring causes of behavior, that is, in virtue of structuring a causal system in such a way that the occurrence of a triggering neurophysiological cause causes a given behavioral effect ( see, for example, dretske 1988 ). most philosophers nowadays defend some version of non - reductive physicalism. according to non - reductive physicalism, all scientifically respectable entities are physical entities, where entities which cannot be straightforwardly reduced to physical entities — mental events or properties, for instance — are physical at least in the broad sense that they superven
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subdomain_quantum_field_theory
| 0.610579
| 512
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HuggingFaceFW/fineweb-edu
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the elm and the expert : mentalese and its semantics. cambridge, ma : mit press. - foster, j. ( 1996 ). the immaterial self. london : routledge. - haggard, p. & eimer, m. ( 1999 ). on the relation between brain potentials and the awareness of voluntary movements. experimental brain research, 126, 128 - 133. - hodgson, s. ( 1965 ). time and space : a metaphysical essay. london : longmans, green. - honderich, t. ( 1982 ). the argument for anomalous monism. analysis, 42, 59 - 64. - huxley, t. h. ( 1874 ). on the hypothesis that animals are automata, and its history. fortnightly review, 22, 555 - 580. reprinted in collected essays : volume i, method and results, 195 - 250. london : macmillan 1893. - huxley, t. h. ( 1898 ). hume with helps to the study of berkeley. new york : d. appleton and company. - hyslop, a. ( 1998 ). methodological epiphenomenalism. australasian journal of philosophy, 76, 61 - 70. - jackson, f. ( 1982 ). epiphenomenal qualia. philosophical quarterly, 32, 127 - 136. - jackson, f. & pettit, p. ( 1990 ). program explanation : a general perspective. analysis, 50, 107 - 117. - james, w. ( 1879 ). are we automata? mind, 4, 1 - 22. - keller, i. & heckhausen, h. ( 1990 ). readiness potentials preceding spontaneous motor acts : voluntary vs. involuntary control. electroencephalography and clinical neurophysiology, 76, 351 - 361. - kim, j. ( 1989a ). the myth of nonreductive materialism. proceedings of the american philosophical association, 63, 31 - 47. reprinted in supervenience and mind : selected philosophical essays, 265 - 284. cambridge : cambridge university press 1993. - kim, j. ( 1993a ). can supervenience and ‘ non - strict laws ’ save anomalous monism?, mental causation, ed. j. heil & a. mele, 19 - 26. oxford : clarendon press. - kim, j. ( 1998 ). mind in a physical world : an essay on the mind -
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mind, ed. s. guttenplan, 277 - 288. oxford : blackwell. - mill, j. s. ( 1865 ). an examination of sir william hamilton ’ s philosophy. collected works of john stuart mill, vol. 9, ed. j. m. robson. toronto : university of toronto press, 1979. - miller, j. & trevena, j. ( 2002 ). cortical movement preparation and conscious decisions : averaging artifacts and timing biases. consciousness and cognition, 11, 308 - 313. - pauen, m. ( 2006 ). feeling causes. journal of consciousness studies, 13, 129 - 152. - pockett, s., banks, w. & gallagher, s. ( 2006 ). does consciousness cause behavior? cambridge, ma : mit press. - popper, k. & eccles, j. ( 1977 ). the self and its brain. new york : springer. - putnam, h. ( 1975 ). the meaning of ‘ meaning ’. minnesota studies in the philosophy of science, 7, 131 - 193. reprinted in mind, language, and reality : philosophical papers, vol. 2, 215 - 271. cambridge : cambridge university press 1975. - robinson, w. ( 1982 ). causation, sensations and knowledge. mind, 91, 524 - 540. - robinson, w. ( 2003 ). epiphenomenalism, the stanford encyclopedia of philosophy ( spring 2003 edition ), hrsg. v. e. zalta, url = < >. - robinson, w. ( 2004 ). understanding phenomenal consciousness. cambridge : cambridge university press. - robinson, w. ( 2006 ). knowing epiphenomena. journal of consciousness studies, 13, 85 - 100. - russell, b. ( 1948 ). human knowledge : its scope and limits. london : allen & unwin. - sosa, e. ( 1993 ). davidson ’ s thinking causes, mental causation, ed. j. heil & a. mele, 41 - 50. oxford : clarendon press. - staudacher, a. ( 2006 ). epistemological challenges to qualia - epiphenomenalism. journal of consciousness studies, 13, 153 - 175. - taylor, a. ( 1927 ). plato : the man and his work. new york : macveagh. - taylor, r. ( 1963 ). metaphysics. englewood cliffs :
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four laws that drive the universe by peter atkins ( oxford university press, usa, hardcover, 9780199232369, 130pp. ) publication date : november 2007 written by peter atkins, one of the worlds leading authorities on thermodynamics, this powerful and compact introduction explains what these four laws are and how they work, using accessible language and virtually no mathematics. guiding the reader a step at a time, atkins begins with zeroth ( so named because the first two laws were well established before scientists realized that a third law, relating to temperature, should precede them - - hence the jocular name zeroth ), and proceeds through the first, second, and third laws, offering a clear account of concepts such as the availability of work and the conservation of energy. atkins ranges from the fascinating theory of entropy ( revealing how its unstoppable rise constitutes the engine of the universe ), through the concept of free energy, and to the brink, and then beyond the brink, of absolute zero. c. p. snow once remarked that not knowing the second law of thermodynamics is like never having read a work by shakespeare. this brief but brilliant book introduces general readers to one of the cornerstones of modern science, four laws that are as integral to the well - educated mind as such great dramatic works as hamlet or macbeth.
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2025-12-25T21:10:56.589100
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these rings ( 20 µm across ) have color created by the width of the slits ( see black and white inset ). for example, yellow is produced with slits that are each 90 nm wide. the technique uses light funneling to catch and trap particular wavelengths. researchers at the university of michigan ( u. s. a. ) have found a way to lock in structural color using sub - wavelength structures ( scientific reports 3, 1194 ). if the technique can be developed further, it could be used with e - readers and other reflective displays, as well as for sensors and hyperspectral imagers. diffraction gratings provide structural color, but the predominant color changes with viewing angle. instead of using gratings on the order of the wavelengths, and on the surface of the material, the researchers went vertical. group leader jay guo explains, " light is funneled into the nanocavity, whose width is much, much smaller than the wavelength of the light. " surprisingly the longer wavelengths of light get trapped in narrower grooves. to demonstrate their device, the researchers etched nanoscale grooves in glass and coated the grooved glass plate with a thin layer of silver. when light hits the grooved surface, the transverse electric component creates a polarization charge at the metal slit surface, boosting the local electric field near the slit, which preferentially pulls in the transverse magnetic component of a particular wavelength of light. the demonstrated optical device has high absorption, as large as 96 percent in the visible spectrum, with colors that don ’ t change over a + / - 80 degree viewing angle. the device also demonstrated wide color tunability throughout the entire visible spectrum and pixel sizes smaller than the diffraction limit. right now, the new device can make static pictures. even static displays, however, can be attractive with bright sunlight - visible color in low - energy - consumption reflective displays.
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defined the distance between the imported chemical pigment and the biological blue - green ( cyan, to be more precise ) pigment of the jellyfish protein in such a way that the interplay between the two dyes resulted in a completely novel kind of fluorescent chimeric biomolecule. because of the extreme proximity of the two luminescent groups the pale lavender of the synthetic amino acid can no longer be detected ; instead, the typical blue - green color of the fluorescent protein dominates. " what is special here, and different from the natural gfp, is that, thanks to the synthetically incorporated amino acid, the fluorescence can be excited with a commercially available black - light lamp in place of an expensive dedicated laser apparatus, " explains sebastian kuhn, who conducted these groundbreaking experiments as part of his doctoral thesis. according to skerra, the design principle of the novel bio - molecule, which is characterized by a particularly large and hard to achieve wavelength difference between excitation and emitted light, should open numerous interesting applications : " we have now demonstrated that the technology works. our strategy will enable the preparation of customized fluorescent proteins in various colors for manifold future purposes. " this research project was financially supported by the german research foundation ( dfg ) as part of the excellence cluster " munich center for integrated protein science " ( cips - m ). on the net :
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2025-12-25T21:10:57.272995
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bill scanlon, nrel january 02, 2013 | 3 comments it takes outside - the - box thinking to outsmart the solar spectrum and set a world record for solar cell efficiency. the solar spectrum has boundaries and immutable rules. no matter how much solar cell manufacturers want to bend those rules, they can ' t. so how can we make a solar cell that has a higher efficiency than the rules allow? that ' s the question scientists in the iii - v multijunction photovoltaics group at the u. s. department of energy ' s ( doe ) national renewable energy laboratory ( nrel ) faced 15 years ago as they searched for materials they could grow easily that also have the ideal combinations of band gaps for converting photons from the sun into electricity with unprecedented efficiency. a band gap is an energy that characterizes how a semiconductor material absorbs photons, and how efficiently a solar cell made from that material can extract the useful energy from those photons. " the ideal band gaps for a solar cell are determined by the solar spectrum, " said daniel friedman, manager of the nrel iii - v multijunction photovoltaics group. " there ' s no way around that. " but this year, friedman ' s team succeeded so spectacularly in bending the rules of the solar spectrum that nrel and its industry partner, solar junction, won a coveted r & d 100 award from r & d magazine for a world - record multijunction solar cell. the three - layered cell, sj3, converted 43. 5 % of the energy in sunlight into electrical energy — a rate that has stimulated demand for the cell to be used in concentrator photovoltaic ( cpv ) arrays for utility - scale energy production. last month, that record of 43. 5 % efficiency at 415 suns was eclipsed with a 44 % efficiency at 947 suns. both records were verified by nrel. this is nrel ' s third r & d 100 award for advances in ultra - high - efficiency multijunction cells. cpv technology gains efficiency by using low - cost lenses to multiply the sun ' s intensity, which scientists refer to as numbers of suns. friedman says earlier success with multijunction cells — layered semiconductors each optimized to capture different wavelengths of light at their junctions — gave nrel a head start. the sj3 cells fit into the market for utility - scale cpv projects. they ' re designed for application under sunlight concentrated to 1, 000 times its
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subdomain_quantum_materials
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introduction to integrals the definite integral the definite integral is a convenient notation used the represent the left - hand and right - hand approximations discussed in the previous section. f ( x ) dx means the area of the region bounded by f, the y - axis and the lines x = a and x = b. writing f ( x ) dx is equivalent to writing on the interval [ a, b ], but it is a much more compact way of doing so. note also the similarity between the two expressions. this should serve as a clear reminder that the definite integral is just the limit of right - hand and left - hand approximations. unlike the indefinite integral, which represents a function, the definite integral represents a number, and is simply the signed area under the curve of f. the area is considered " signed " because according to the method of calculating the areas by subdivisions, the regions located below the x - axis will be counted as negative, and the regions above will be counted as positive. negative regions cancel out positive regions, and the definite integral represents the total balance between the two over the given interval. for example, find based on the picture of the region being considered, it should be clear that the answer is zero. here, the negative region is exactly the same size as the positive region : properties of the definite integral the definite integral has certain properties that should be intuitive, given its definition as the signed area under the curve : - cf ( x ) dx = c f ( x ) dx - f ( x ) + g ( x ) dx = f ( x ) dx + g ( x ) dx is on the interval f ( x ) dx = f ( x ) dx + f ( x ) dx this means that we can break up a graph into convenient units and find the definite integral of each section and then add the results to find the total signed area for the whole region. the fundamental theorem of calculusthe fundamental theorem of calculus, or " ftc ", offers a quick and powerful method of evaluating definite integrals. it states : if f is an antiderivative of f, then f ( x ) dx = f ( b ) - f ( a ) x 2 dx = ( 1 ) 3 - ( 0 ) 3 = often, a shorthand is used that means the same as what is written above : x 2 dx = x 3 = one interpretation of the ftc is that the area under the graph of the derivative is equal to
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subdomain_quantum_field_theory
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2025-12-25T21:10:57.511537
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this weather balloon is full of helium gas. it is surrounded by earth ' s atmosphere, which is mostly nitrogen and oxygen gasses. helium is " lighter " ( less dense ) than nitrogen or oxygen, so the balloon will rise when the scientist lets go of it. click on image for full size image courtesy of the university corporation for atmospheric research. gas is one of the four common states of matter. the three others are liquid, solid, and plasma. there are also some other exotic states of matter that have been discovered in recent years. the air in earth ' s atmosphere is mostly a mixture of different types of gases. a gas usually has much lower density than a solid or liquid. a quantity of gas doesn ' t have a specific shape ; in this way it is like a liquid and different from a solid. if a gas is enclosed in a container, it will take on the shape of the container ( a liquid will too ). the volume of a gas changes if the temperature or pressure changes. there are several scientific laws, called the " gas laws ", that describe how the volume, temperature, and pressure of a gas are related. the molecules or atoms in a gas are much further apart than in a solid or a liquid. gas molecules or atoms are usually flying around at very high speeds, occasionally bouncing off each other or the walls of the container the gas is in. when a gas is cooled or placed under high pressure, it can condense and turn into a liquid. if a liquid boils or evaporates, it will become a gas. under some circumstances, usually very low pressure, a solid can turn directly into a gas ( without first melting and becoming a liquid ). when a solid turns directly into a gas, it is called " sublimation ". most of the air in earth ' s atmosphere is either nitrogen or oxygen gas. balloons are often filled with helium gas ; since helium is lighter ( less dense ) than air, helium balloons " float " or rise up in air. when liquid water boils or evaporates, it turns into a gas called " water vapor ". most of the gas in the atmospheres of the giant planets jupiter and saturn is hydrogen gas. in recent years, carbon dioxide gas has become quite famous because of its role in the greenhouse effect and global warming. shop windows to the universe science store! our online store includes fun classroom activities for you and your students. issues of nesta ' s quarterly journal, the earth scientist are also full of classroom activities on different
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2025-12-25T21:10:57.715675
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role in the greenhouse effect and global warming. shop windows to the universe science store! our online store includes fun classroom activities for you and your students. issues of nesta ' s quarterly journal, the earth scientist are also full of classroom activities on different topics in earth and space science! you might also be interested in : solid is one of the four common states of matter. the three others are gas, liquid, and plasma. there are also some other exotic states of matter that have been discovered in recent years. unlike liquids... more plasma is known as the fourth state of matter. the other three states are solid, liquid and gas. almost everything is made up of atoms ( your dog, your science book, this computer... ). the atom has a nucleus... more density is a measure of how much mass is contained in a given unit volume ( density = mass / volume ). put simply, if mass is a measure of how much ‘ stuff ’ there is in an object, density is a measure of how... more most things around us are made of groups of atoms connected together into packages called molecules. molecules are made from atoms of one or more elements. some molecules are made of only one type of... more a snowman, glass of water and steam might look very different but they are made of the same stuff! just like any substance, water has three different forms, called states : solid, liquid and gas. the state... more have you ever left a glass of water out for a long time? did you notice that the water disappears after a few days? that ' s because it evaporated! evaporation is when water passes from a liquid to a gas.... more there is more nitrogen gas in the air than any other kind of gas. about four out of five of the molecules in earth ' s atmosphere is nitrogen gas! a molecule of nitrogen gas is made up of two nitrogen atoms.... more
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just ask antoine! - a substance which is not normally found in a living thing. - xenon. xe. - element 54, a colorless, inert gas used to fill cathode ray tubes. - a very high energy form of electromagnetic radiation ( though not as high energy as gamma rays ). x - rays typically have wavelengths from a few picometers up to 20 nanometers. x - rays easily penetrate soft tissue, which makes them useful in medical imaging and in radiation therapy. - x - ray crystallography. - determination of three dimensional arrangement of atoms in a crystal by analysis of x - ray diffraction patterns. - x - ray diffraction pattern. - interference patterns created by x - rays as they pass through a solid material. studying x - ray diffraction patterns gives detailed information on the three - dimensional structure of crystals, surfaces, and atoms. - x - ray spectrum. x - ray spectra. - a set of characteristic x - ray frequencies or wavelengths produced by a substance used as a target in an x - ray tube. each element has a characteristic x - ray spectrum, and there is a strong correlation between atomic number and the frequencies of certain lines in the x - ray spectrum. - x - ray tube. - a cathode ray tube that focuses energetic streams of electrons on a metal target, causing the metal to emit x - rays.
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subdomain_quantum_materials
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<urn:uuid:74237f6d-6f51-4ed9-b068-b8dcfc0b31fa>
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2025-12-25T21:10:57.831568
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dynamic update. or, that functional programming gives the best way to understand mutation. this just seems wrong to me. monads are notoriously difficult to understand, mutation is intuitively easy to understand. that is, i would say : we already understood mutation, now we look at it from a different perspective to try better understand how to combine it with other effects. of course what i just wrote may not be what it means to ‘ “ really ” understand mutation / dynamic update ’. nevertheless, i would suggest that to “ really ” understand something entails proving theorems about it that go beyond particular usage examples — at least, not just “ this program gives the correct output on this sample input ” but “ this program part works on all inputs regardless of the rest of the program ”. as soon as we humans who get bored easily try to prove such theorems, we want to capture repeated patterns in our reasoning so as to avoid repeating them. ( hoare logic for reasoning about imperative programs is a great and successful example of such capture, even though it treats mutation specifically and not as a special case of a side effect. ) maybe understanding mutation even entails being confident in a program part that uses mutation and no other side effect, regardless of what side effects occur in the rest of the program. one question i asked yesterday ( last night ) is whether the analogy between quantification and shift / reset yielded insight independent of what kind of semantics one gave for shift / reset : shift / reset can be understood operationally, as a reduction calculus. can quantification? but maybe this is just what qr is. in general, is the transformation to lf a kind of operational semantics? i would answer yes, yes, yes. i take at least 3 lessons from programming - language semantics into natural - language semantics : first, there are different kinds of semantics, not only denotational but also operational and axiomatic, each good for different purposes. operational makes it more obvious how much time and space a program will take ; denotational makes it easier to substitute equals for equals in a larger program. second, we should relate the different kinds of semantics. for example, i ’ m a big fan of olivier danvy ’ s work on mechanically turning denotational semantics ( well, definitional interpreters ) into operational semantics or back. imagine putting towers into a vending machine and getting qr out or vice versa! finally, it is worth applying specific ideas such as monads in denotational semantics
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subdomain_quantum_computing
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<urn:uuid:8273d07f-0654-48a0-821a-96b5185d6549>
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2025-12-25T21:10:58.028785
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semantics ( well, definitional interpreters ) into operational semantics or back. imagine putting towers into a vending machine and getting qr out or vice versa! finally, it is worth applying specific ideas such as monads in denotational semantics and evaluation contexts in operational semantics. is it only from the point of view of continuations that one can understand ( best ) a programming language that contains control and state? continuations are the best denotational account of control. it makes it easy to prove that the following expressions can be substituted for each other : ( shift c ( and ( c ( mother ' john ) ) ( c ( mother ' mary ) ) ) ) ; john and mary ' s mother ( mother ( shift c ( and ( c ' john ) ( c ' mary ) ) ) ) ; john ' s mother and mary ' s mother do continuations help us understand / reason about order of evaluation per se, or do they help us reason about order of evaluation in the context of a compositional semantics? the latter, and thus the former, no? : ) in general, should the monad / continuation approach give us insights into natural language meaning ( empirically relevant insights ), or should it give us insights into how to analyze natural language meaning in a certain way, compositional semantics? the latter, and thus the former, no? : ) : ) it seems to me that the analogy between computational side effects and “ apparently noncompositional ” linguistic phenomena could be insightful in the first way, and that these insights would be conceptually prior to any implementation in terms of monads / continuations. sure, if i were patenting all this then i would claim an implementation in terms of monads / continuations as “ a preferred embodiment ” of the analogy. take weak crossover. the insight is that evaluation order matters. you and ken used continuations to capture this compositionally. but now your account of order - sensitivity is order - independent. this is what we need for traditional, bottom - up compositional semantics. but why do we still want this? or, what is the status of such a semantics? it is often said that a compositional semantics is necessary for humans to understand novel utterances. but i think it is apparent that weak crossover arises not because humans learn a compositional semantics which simulates order - sensitivity, but rather because of the actual order - sensitivity of processing ( we hear from left to right ). what kind of semantic system captures this directly? you probably
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subdomain_quantum_computing
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<urn:uuid:8273d07f-0654-48a0-821a-96b5185d6549>
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an entity built for data storage services. these are not available for use outside the boundaries of the application and are often encapsulated behind a services layer. domain model. an object that represents an entity in the problem domain, which may also be annotated or extended to support some application features such as validation or authentication. because these models need to be shared between the server and client browser, they are sometimes contained within view models and used directly for data - binding in html forms. application models and service models are variations of domain models. eavesdropping. exploiting a web application using a network data capture utility to find and record http requests and responses between a website and a client. eavesdropping can lead to disclosure of sensitive information such as passwords, personal, or financial information, and can potentially allow the execution of spoofing, tampering and message replay attacks. flow diagram. a diagram that defines the pages in the site, actions available on those pages, and navigation between pages. this diagram reflects the user stories identified in the requirements. forms authentication. forms authentication enables user and password validation for web applications that do not require windows authentication. form model. an entity that represents all of the fields in an html form that is specific to a controller action. it contains only the data that is passed into the action. generally, this corresponds to whatever form is posting back to the server. form models ( sometimes called request models ) are a special case of view models. view models are more generic in that they may also include additional data needed to render a page. a form model might end up being a property on another view model. fragment identifier. the portion of a url identified by the hash ( # ). with regard to browser navigation, hyperlinks include them to make the hyperlink unique. when used in conjunction with the hashchange event, page content is able to change without performing a full - page reload. given - when - then template. a helpful template for defining acceptance criteria that include the context of the test ( given ), the action being tested ( when ), and the expected outcome ( then ). this template provides clear and concise documentation that can be understood by team members and can be used to generate both manual and automated test scripts. jquery selectors. a syntactical aspect of jquery that allows you to select all dom elements based on specific criteria ( tag name, id, attribute name, value, and more ). once the selection
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subdomain_quantum_cryptography
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encryption algorithm more random and less susceptible to attack. sandboxing. technique that allows components of the application to be tested before the entire application is complete. it also makes testing more robust by preventing software defects in one module from blocking or affecting the testing of other modules. single - page interface ( spi ) pattern. a pattern for web applications that reduces the number of full - page reloads during user navigation. when a user performs an action, such as selecting a hyperlink, which traditionally requires the site to load a new web page, the application instead modifies the current web page without reloading it. single - page interface web application. web application where the user is only required to perform a full - page load once. from that point on, all page changes and data loading is performed without a full - page reload. hotmail, office live, and twitter are examples of single - page interface web applications. sliding expiration. a pre - determined amount of time where an authenticated user can use the site. the amount of time is reset whenever the user makes a new request to the server. the advantage of using a sliding expiration is that it does not force the user to authenticate again if he or she maintains a reasonable level of activity in the application. otherwise, the user would be redirected to the authentication page after a fixed amount of time had elapsed after the initial authentication. static web application. web sites consisting of static html pages, css, and images. as each page is navigated to, the browser performs a full - page reload. structure. the html of the page as it relates to the hierarchy of elements that make up the page, rather than the visual appearance or layout of the ui. topic. the message between the publisher and subscriber in a pub / sub environment. this message, also often referred to as an event, represents the contract between the sender and receiver, and is made up of a name and an optional message body. user gestures. a specific action that a user takes in order to interact with an application. traditionally, gestures include mouse clicks and keys presses. however, many modern applications also employ interactions in which a user acts more directly on an application. for example, they may touch a screen to swipe, pinch, or pull content. viewbag. the name / value keyed collection that lets you store any loosely typed data. asp. net mvc 3 introduced the viewbag ( called viewdata in previous versions ) in
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2025-12-25T21:10:58.688170
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sparks - st. elmo ' s fire instructor / speaker : prof. walter lewin last time i mentioned to you that charge resides at the surface of solid conductors but that it ' s not uniformly distributed. perhaps you remember that, unless it happens to be a sphere. and i want to pursue that today. if i had a solid conductor which say had this shape and i ' m going to convince you today that right here, the surface charge density will be higher than there. because the curvature is stronger than it is here. and the way i want to approach that is as follows. suppose i have here a solid conductor a which has radius r of a and very very far away, maybe tens of meters away, i have a solid conductor b with radius r of b and they are connected through a conducting wire. if they are connected through a conducting wire, then it ' s equipotential. they all have the same potential. i ' m going to charge them up until i get a charge distribution qa here and i get qb there. the potential of a is about the same that it would be if b were not there. because b is so far away that if i come with some charge from infinity in my pocket that the work that i have to do to reach a per unit charge is independent of whether b is there or not, because b is far away, tens of meters, if you can make it a mile if you want to. and so the potential of a is then the charge on a divided by 4 pi epsilon 0 the radius of a. but since it is an equipotential because it ' s all conducting, this must be also the potential of the sphere b, and that is the charge on b divided by 4 pi epsilon 0 r of b. and so you see immediately that the q, the charge on b, divided by the radius of b, is the charge on a divided by the radius on a. and if the radius of b were for instance 5 times larger than the radius of a, there would be 5 times more charge on b than there would be on a. but if b has a 5 times larger radius, then its surface area is 25 times larger and since surface charge density, sigma, is the charge on a sphere divided by the surface area of the sphere, it is now clear that if the radius of b is 5 times larger than a, it ' s true that the charge on b is 5 times the charge on a, but the surface charge density on b is
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subdomain_quantum_materials
| 0.637277
| 512
|
HuggingFaceFW/fineweb-edu
|
<urn:uuid:0b039c0b-d2e7-44ec-92d2-bb2f379367ca>
| 0
| 0.6
|
2025-12-25T21:10:58.832855
|
inside is of course the surface charge density times the area a, divided by epsilon 0, this is gauss ' s law. and so you find immediately that the electric field is sigma divided by epsilon 0. so whenever you have a conductor if you know the local surface charge density you always know the local electric field. and since the surface charge density is going to be the highest here, even though the whole thing is an equipotential, the electric field will also be higher here than it will be there. i can demonstrate this to you in a very simple way. i have here a cooking pan and the cooking pan, i used to boil lobsters in there, it ' s a large pan. the cooking pan i ' m going to charge up and the cooking pan here has a radius, whatever it is, maybe 20 centimeters, but look here at the handle, how very small this radius is, so you could put charge on there and i ' m going to convince you that i can scoop off more charge here where the radius is small than i can scoop off here. i have here a small flat spoon and i ' m going to put the spoon here on the surface here and on the surface there and we ' re going to see from where we can scoop off the most charge. still charged from the previous lecture. so here, we see the electroscope that we have seen before. i ' m going to charge this cooking pan with my favorite technique which is the electrophorus. so we have the cat fur and we have the glass plate. i ' m going to rub this first with the cat fur, put it on, put my finger on, get a little shock, charge up the pan, put my finger on, get another shock, charge up the pan, and another one, charge up the pan, make sure that i get enough charge on there, rub the glass again, put it on top, put my finger on, charge, once more, and once more. let ' s assume we have enough charge on there now. here is my little spoon. i touch here the outside here of the can - - of the pan. and go to the electroscope and you see a little charge. it ' s very clear. what i want to show you now it ' s very qualitative is that when i touch here the handle, it ' s a very small radius, that i can take off more charge. there we go. that ' s all i wanted to show you. so you
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subdomain_quantum_materials
| 0.620485
| 512
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:0b039c0b-d2e7-44ec-92d2-bb2f379367ca>
| 2
| 0.6
|
2025-12-25T21:10:58.835359
|
those of us with even a passing interest in science are used to the idea that computers play a central role in understanding physics and chemistry, especially high - powered computation used in areas such as weather prediction and molecular visualization. however, over the past few years, a new target for that computation has emerged and begun to attract media attention. it ' s called computational biology ( or more catchy, bioinformatics ) and it refers to the digital storage, categorization, and analysis of biological data. if your most recent encounter with biology took place in high school, you may be surprised by any such crossover with computing. although i always found it fascinating, i remember biology never quite having the rigor of its counterparts in the science curriculum. some cells did this, other cells had that, and different organisms did all sorts of strange things, especially when dissected by over - enthusiastic schoolchildren. but there seemed to be few universal principles equivalent in scope to newton ' s equations or the periodic table of elements. digitizing life - - thanks to the wonders of molecular biology, many such fundamentals are now known to exist. an overview of some of the basics should give an impression of what is involved - bear in mind that we ' re dealing with the natural world in all its complexity, so everything that follows has been vastly simplified. life as we know it is encoded in a set of long molecules called dna, identical copies of which are found in every cell in a living organism such as a human being. everything that happens within an organism can be traced back to its dna - just like the hard disk in a computer. in humans, each cell contains 46 separate dna molecules called chromosomes, analogous perhaps to hard disk partitions. your chromosomes contain a mixture of information duplicated from those of your parents, which is one reason why you inherited so many of their characteristics. any one dna molecule consists of a series of connected nucleotides forming a chain that can run to lengths of many millions. there are only four possible nucleotides, so any dna molecule can be represented as a sequence using only four letters. this is where the digitization begins - the entire set of chromosomes for a human being can be stored in a few gigabytes of space ( even less after compression ) and you can even download a recent draft to your own computer. according to present - day understanding, only a fraction of your dna has a purpose - the other 98 percent or so is affectionately named " junk. " the meaningful bits, known as
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subdomain_quantum_computing
| 0.628588
| 512
|
HuggingFaceFW/fineweb-edu
|
<urn:uuid:15312acd-e457-48ad-8cf4-f817fd406dcf>
| 0
| 0.6
|
2025-12-25T21:10:59.115410
|
from physics research archive - page 4 the physics classroom : total internal reflection - sep 16, 2010 the optical fiber in the photo above doesn ' t just guide the beam - - the fiber produces the beam. instead of a tube of helium and neon gas, or a piece of ruby, the " active medium " of this laser is added to the glass in the fiber. since the mirrors are just the polished ends of the fiber, there is nothing to go out of alignment, and maintenance is easy. network theory : a key to unraveling how nature works - sep 1, 2010 you are looking at a network diagram that shows the interconnectedness of the world economy. to learn more about this network, visit mapping the world economy. making a supersonic jet in your kitchen - aug 16, 2010 what exactly happens when an object makes a splash in water? the disk shown above was pulled into water in a reproducible way to investigate the splash. the real sea monsters : on the hunt for rogue waves - aug 1, 2010 this " rogue wave " broke over the deck of an oil tanker, and was much taller than the other waves on the ocean at the time. see freak waves, rogue waves for graphs of rogue waves building up in the ocean, and for the measurement of one that struck an oil platform in the north sea. from soap bubbles to technology - jul 16, 2010 the soap film you see here, made in between two metal rings, is called a catenoid, and it uses the minimum area to enclose a given volume. click on the image to see another example of a " minimal surface " soap film. about dust - jul 1, 2010 this satellite image shows a recent dust storm in china that was so large it spread out to neighboring countries. for more on this storm, see this time magazine article and also about dust. shock diamonds and mach disks - jun 16, 2010 when the speed of the gases in a jet or rocket exhaust exceeds the speed of sound, a dazzling pattern results called " shock diamonds " or " mach disks, " as shown in this photo of the sr - 71 blackbird. the diamonds are created by crisscrossing shock waves in the exhaust. image credit : nasa, esa, h. bond ( stsci ), r. ciardullo ( penn state ), and the hubble heritage team ( aura / stsci ) ; image source ; larger image stellar evolution - jun 1, 2010 when the sun reaches the end of its life, its outer layers will
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subdomain_quantum_optics
| 0.649904
| 512
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:61a1c128-6043-43d5-acf4-3f35e7ec4ab0>
| 0
| 0.6
|
2025-12-25T21:10:59.834746
|
cells rely on tiny molecular motors to deliver cargo, such as mrna and organelles, within the cell. the critical nature of this transport system is evidenced by the fact that disruption of motors by genetic defects leads to fatal diseases in humans. although investigators have isolated these motor to study their function in a controlled environment outside the cell, it has been difficult for researchers to follow these fascinating molecular transporters in their natural environment, the living cell. now, two articles published by cell press in biophysical journal, make use of incredibly tiny, glowing " quantum dots " to track the miniscule motions of myosin v in living cells. interestingly, both research groups independently report that myosin v molecules carry their quantum dot cargo either in a straight line or in a manner akin to a drunken walk. myosin v is a motor molecule that " walks " in a fashion similar to humans by stepping along actin filament tracks that are assembled in a dense, criss - crossing network inside the cell. a critical feature of these motors is their ability to walk long distances without falling off their tracks. however, this has never been observed within cells. through the binding of quantum dots directly to a single myosin v molecule, both investigative teams used sophisticated microscopes and sensitive cameras to witness the 72 nanometer strides ( equivalent to 1 millionth of an inch ) taken by these motors for the first time in cells. in results published in the may 20th 2009 issue of biophysical journal, dr. giovanni cappello from the institut curie in paris, france tracked the movement of single myosin v molecules with inside living hela cells. dr. cappello and colleagues reported that the myosin v can transport cargo for long distances without falling off its track at velocities higher than would be expected based on earlier studies. " our approach goes beyond conventional experiments on organelles and opens interesting perspectives for studying intracellular transport pathways and how motors behave in complex filament networks, " says dr. cappello. dr. david warshaw and colleagues from the university of vermont college of medicine used quantum dots to follow the activity of myosin v in cos - 7 cells. their findings, published in the july 22nd 2009 issue of the journal, suggested that myosin v ' s apparent drunken walk is in fact the motor taking turns at almost every intersection it encounters along the dense and randomly oriented intracellular actin highway. " cargo delivery in cells can ' t totally be a random process, therefore,
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subdomain_quantum_materials
| 0.619607
| 512
|
HuggingFaceFW/fineweb-edu
|
<urn:uuid:5f725809-c65a-4ea3-9c56-3f7abc647b7e>
| 0
| 0.6
|
2025-12-25T21:10:59.992212
|
, or, not and near ( known as operators ) to limit, widen, or define your search. most internet search engines default to a boolean and search, but its handy for you to know how to do a basic boolean search. - boolean logic is just the term used to describe certain logical operations that are used to combine search terms in many search engine databases and directories on the net. basic boolean search operator - and using and narrows a search by combining terms ; it will retrieve documents that use both the search terms that you specify, as in this example : adelaide and south australia basic boolean search operator - or using or broadens a search to include results that contain either of the words you type in. or is a good tool to use when there are several common spellings or synonyms of a word, as in this example : computer or pc basic boolean search operator - not - using not will narrow a search by excluding certain search terms. not retrieves documents that contain one, but not the other, of the search terms you enter, as in this example : adelaide not travel. keep in mind that not all search engines and directories support boolean terms. however, most do, and you can easily find out if the one you want to use supports this technique by consulting the faq ' s ( frequently asked questions ) on a search engine or directory ' s home page. further search operators include : - near means you want all the words in that specific order or the actual phrase. - nand means a combination of not and and - nor means a combination of not and or conduct a search with domain names to refine the search : if you know the website you are looking for is specific type of website, for example a website for a government agency or a school can be identified by the last part of its web address. -. com = a commercial business -. edu = an educational institution -. gov = a governmental institution -. org = a non - profit organization -. biz = a business example : to search for a south australian government website you would type “ south australia site :. sa. gov. au ” into your search engine. you can also select to search for websites from a specific country. -. au = australia -. fr = france -. co. uk = england example : for holiday websites from australia you would type “ holidays site :. au ” into your search engine.
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subdomain_quantum_computing
| 0.603309
| 496
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:e53c7953-637b-4d2b-8fd5-221ab09b29cd>
| 2
| 0.6
|
2025-12-25T21:11:00.078400
|
hypnosis, hypnotherapy : hypnosis is a trance - like state in which a person becomes more aware and focused and is more open to suggestion. hypnotherapy has been used to treat health conditions or to change behaviors. early study suggests that hypnosis may have short and long - term effects for patients with mild high blood pressure. additional research is needed to confirm these findings. - use cautiously with mental illnesses ( e. g. psychosis, schizophrenia, manic depression, multiple personality disorder, or dissociative disorders ) or seizure disorders. iridology is the study of the iris ( colored part of the eye ) with the intention of gaining information about underlying diseases. iridologists believe that the degrees of light and darkness in the iris give clues to the body ' s general health. preliminary studies by a south korean team of researchers using a computerized approach suggest that iridology may assist in the identification of individual predispositions for vascular diseases such as hypertension. further research is needed to confirm the effectiveness of iridology as a diagnostic tool for hypertension, and further teams of researchers would need to conduct parallel work in order for these methods to become validated. - iridology should not be used alone to diagnose disease. studies of iridology have reported incorrect diagnoses, and thus, potentially severe medical problems may go undiagnosed. in addition, research suggests that iridology may lead to inappropriate treatment. iridology is therefore not recommended as a sole method of diagnosis or treatment for any condition. - lutein : lutein and zeaxanthin are found in high levels in foods, such as green vegetables, egg yolk, kiwi fruit, grapes, orange juice, zucchini, squash, and corn. preliminary evidence suggests that pre - eclampsia risk may decrease with increasing concentrations of lutein. additional human studies are needed before a firm recommendation can be made. - avoid if allergic or hypersensitive to lutein or zeaxanthin. use cautiously if at risk for cardiovascular disease or cancer. avoid if pregnant or breastfeeding. - lycopene : lycopene is a carotenoid, which is a naturally occurring class of fat - soluble pigments ( coloring ) found mainly in plants and algae. lycopene is present in human serum, liver, adrenal glands, lungs, prostate, colon, and skin at higher levels than other carote
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subdomain_quantum_optics
| 0.607461
| 512
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:7df2c02b-3013-4ab0-a13c-4c01a58c76f7>
| 23
| 0.6
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2025-12-25T21:11:00.510189
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called a biconditional. " iff " joins two sentences to form a new sentence. it should not be confused with logical equivalence which is a description of a relation between two sentences. the biconditional " a iff the sentences a, describing a relation between the states of affairs a describe. by contrast " a is logically equivalent to b " mentions both sentences : it describes a relation between those two sentences, and not between whatever matters they describe. the distinction is a very confusing one, and has led many a philosopher astray. certainly it is the case that when a is logically equivalent to b, " a iff b " is true. but the converse does not hold. reconsidering the sentence : - madison will eat pudding if and only if it is custard. there is clearly no logical equivalence between the two halves of this particular biconditional. for more on the distinction, see w. v. quine ' s mathematical logic, section 5. one way of looking at " a if and only if b " is that it means " a if b " ( b implies a ) and " a only when b " ( not b implies not a ). " not b implies not a " means a implies b, so then we get two way implication. in philosophy and logic, " iff " is used to indicate definitions, since definitions are supposed to be universally quantified biconditionals. in mathematics and elsewhere, however, the word " if " is normally used in definitions, rather than " iff ". this is due to the observation that " if " in the english language has a definitional meaning, separate from its meaning as a propositional conjunction. this separate meaning can be explained by noting that a definition ( for instance : a group is " abelian " if it satisfies the commutative law ; or : a grape is a " raisin " if it is well dried ) is not an equivalence to be proved, but a rule for interpreting the term defined. ( some authors, nevertheless, explicitly indicate that the " if " of a definition means " iff "! ) here are some examples of true statements that use " iff " - true biconditionals ( the first is an example of a definition, so it should normally have been written with " if " ) : - a person is a bachelor iff that person is a marriageable man who has never married. - " snow is white " ( in english ) is true if
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subdomain_quantum_field_theory
| 0.606138
| 512
|
HuggingFaceFW/fineweb-edu
|
<urn:uuid:df826300-5d59-43c7-85d1-1f788051ad03>
| 2
| 0.6
|
2025-12-25T21:32:37.131585
|
the basic forces in nature contemporary physics education project the interactions in the universe are governed by four forces ( strong, weak, electromagnetic and gravitational ). physicists are trying to find one theory that would describe all the forces in nature as a single law. so far they have succeeded in producing a single theory that describes the weak and electromagnetic forces ( called electroweak force ). the strong and gravitational forces are not yet described by this theory. table courtesy of university of guelph, guelph, ontario ( cananda ) shop windows to the universe science store! cool it! is the new card game from the union of concerned scientists that teaches kids about the choices we have when it comes to climate change — and how policy and technology decisions made today will matter. cool it! is available in our online store you might also be interested in : the neutrino is an extremely light particle. it has no electric charge. the neutrino interacts through the weak force. for this reason and because it is electrically neutral, neutrino interactions with... more some ideas are used throughout the sciences. they are " tools " that can help us solve puzzles in different fields of science. these " tools " include units of measurement, mathematical formulas, and graphs.... more mechanics is the term used to refer to one of the main branches of the science of physics. mechanics deals with the motion of and the forces that act upon physical objects. we need precise terminology... more the interactions in the universe are governed by four forces ( strong, weak, electromagnetic and gravitational ). physicists are trying to find one theory that would describe all the forces in nature as... more when the temperature in the core of a star reaches 100 million degrees kelvin fusion of helium into carbon occurs. oxygen is also formed from fusion of carbon and helium together when the temperature is... more a plot of the binding energy per nucleon vs. atomic mass shows a peak atomic number 56 ( iron ). elements with atomic mass less then 56 release energy if formed as a result of a fusion reaction. above this... more there are several experiments where nuclear fusion reactions have been achieved in a controlled manner ( that means no bombs are involved!! ). the two main approaches that are being explored are magnetic... more
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subdomain_quantum_field_theory
| 0.671339
| 472
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HuggingFaceFW/fineweb-edu
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<urn:uuid:f6b8e300-5420-4e46-9c29-9b2d695a94b5>
| 0
| 0.6
|
2025-12-25T21:32:37.561933
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', curved space. - flat space does not mean the metric tensor is diagonal with the entries ( - 1, 1, 1, 1 ), this is just the case in a very specific coordinate system. flat space means the curvature tensor identically vanishes ( which is independent of the coordinate system ). - of course one can describe accelerated observers in special relativity. that leads me now directly to the equivalence principle, the cornerstone of general relativity. googling ' equivalence principle ' it is somehow depressing. wikipedia isn ' t wrong, but too specific ( the equivalence principle doesn ' t have anything to do with standing on the surface of the earth ). the second hit is a nasa website which i find mostly confusing ( saying all objects react equally to gravity doesn ' t tell you anything about the relation of gravitational to inertial mass ). the third and fourth hits get it right, the fifth is wrong ( the locality is a crucial ingredient ). so here it is : - the equivalence principle : locally, the effects of gravitation ( motion in a curved space ) are the same as that of an accelerated observer in flat space. that is what einstein explains in his thought experiment with the elevator. if you are standing in the elevator ( that is just a local patch, theoretically infinitesimally small ) you can ' t tell whether you are pulled down because there is a planet underneath your feet, or because there is a flying pig pulling up the elevator. this website has two very nice mini - movies depicting the situation. if you could make your elevator larger you could however eventually distinguish between flat and curved space because you could measure geodesic deviation, i. e. the curvature. if you think of particles, the equivalence principle means that the inertial mass is equal to the gravitational mass, which has been measured with impressive precision. but the above formulation makes the mathematical consequences much clearer. to formulate your theory, you will have to introduce a tangential bundle on your curved manifold where you can deal with the ' local ' quantities, and you will have to figure out how the cuts in this bundle ( tensors ) will transform under change of coordinates. if you want your theory to be independent of that choice of coordinates it will have to be formulated in tensor equations. next thing to ask is then how to transport tensors from one point to the other, which leads you to a ' covariant ' derivative. the equivalence principle is thus a very central ingredient of general relativity and despite its simplicity the base of a
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subdomain_quantum_field_theory
| 0.624841
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:a3a65a4a-b5d3-41fd-bd68-47cb1070e5fa>
| 1
| 0.6
|
2025-12-25T21:32:37.764255
|
thing to ask is then how to transport tensors from one point to the other, which leads you to a ' covariant ' derivative. the equivalence principle is thus a very central ingredient of general relativity and despite its simplicity the base of a large mathematical apparatus, it ' s the kind of insight every theoretical physicist dreams of. it gives you a notion of a ' straightest line ' in curved space ( a geodesic ) on which a testparticle moves. this curve most notably is independent of the mass of that particle : heavy and light things fall alike even in general relativity ( well, we already knew this to be the case in the newtonian limit ). for a very nice demonstration see the video on the nasa website. please note that this holds for pointlike testparticles only, it is no loger true for extended or spinning objects, or for objects that significantly disturb the background. the equivalence principle however is not sufficient to give you einstein ' s field equations that describe how space is curved by its matter content. but that ' s a different story. it remains to be said all this is standard textbook knowledge and general relativity is today not usually considered a large mystery. there are definitely more than 3 people who understand it. we have moved on quite a bit since 1905. general relativity is sexy. though i doubt there ' s more than three people in the world who really understand potatoes. * in the more advanced stages of confusion they start referring to physical theories as women. josh, this one ' s for you.
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subdomain_quantum_field_theory
| 0.611866
| 313
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HuggingFaceFW/fineweb-edu
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<urn:uuid:a3a65a4a-b5d3-41fd-bd68-47cb1070e5fa>
| 2
| 0.6
|
2025-12-25T21:32:37.765034
|
| a fool or simpleton ; ninny. | | an extraordinary or unusual thing, person, or event ; an exceptional example or instance. | | — the chemical symbol for | the symbol for the element rubidium. the symbol for rubidium. | rubidium ( r - bid ' e - əm ) pronunciation key a soft, silvery - white metallic element of the alkali group. it ignites spontaneously in air and reacts violently with water. rubidium is used in photoelectric cells, in making vacuum tubes, and in radiometric dating. atomic number 37 ; atomic weight 85. 47 ; melting point 38. 89°c ; boiling point 688°c ; specific gravity ( solid ) 1. 532 ; valence 1, 2, 3, 4. see periodic table. rb / r - b - l / abbreviation : " realtime blackhole list ". a service that allows people to blacklist sites for emitting spam, and makes the blacklist available in real time to electronic - mail transport programs that know how to use rbl so they can filter out mail from those sites. drastic ( and controversial ) but effective. there is an rbl home page ( http : / / maps. vix. com / rbl / usage. html ). chemical element of group 1 ( also called group ia ) in the periodic table, the alkali metal group. rubidium is the second most reactive metal and is very soft, with a silvery - white lustre. a brief treatment of rubidium follows. for full treatment, see alkali metal. learn more about rb with a free trial on britannica. com.
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subdomain_quantum_materials
| 0.675667
| 338
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HuggingFaceFW/fineweb-edu
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<urn:uuid:12ccbc51-911a-4599-9c7d-d1b0b00a0f3b>
| 0
| 0.6
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2025-12-25T21:32:38.188824
|
recursion is a programming paradigm as well as a problem solving strategy thought to be very challenging to grasp for university students. this article outlines a pilot study, which expands the age range of students exposed to the concept of recursion in computer science through instruction in a series of interesting and engaging activities. in this study, a small number of students ( n = 9 ) aged 11 to 13 years, were presented with a new and unique recursion curriculum involving hands - on experiences over a seven - week period at the university of victoria, canada. the curriculum was comprised of a series of progressively challenging recursion activities — roughly based upon the ideas of ‘ computer science unplugged ’ ( bell, witten, & fellows, 2009 ) — and included programming applications with microworlds ex, a programming language based on logo. through this engagement, an increased number of students recognized and understood the concepts covered. we hypothesize that through experiences for youth with activities such as those outlined here, the number of students who understand fundamental computer science applications and who might potentially pursue computer science in post - secondary education will increase. we hypothesis further that through an earlier encounter of “ challenging ” concepts the learning and understanding of those will become easier at the university level. in this paper, the curriculum, classroom experiences, preliminary, largely descriptive and qualitative results and next steps in the research are discussed. gunion, katherine ; milford, todd ; and stege, ulrike " the paradigm recursion : is it more accessible when introduced in middle school?, " the journal of problem solving : 2, article 8.
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subdomain_quantum_simulation
| 0.643934
| 330
|
HuggingFaceFW/fineweb-edu
|
<urn:uuid:8551a3e6-e0bd-4088-a449-3a45fb20ac71>
| 0
| 0.6
|
2025-12-25T21:32:38.202407
|
1. 0 x 10 - 3 mole each of h2 and i2 had been used, together with 2. 0 x 10 - 3 mole of hi, would more hi have been produced spontaneously? | you can verify that the reaction quotient is q = 4. 0. because this is less than keq, the forward reaction is still spontaneous. | if the conditions of example 7 are changed so that the hi concentration is increased to 2. 0 x 10 - 2 mole liter - 1, what happens to the reaction? | the reaction quotient now is q = 400. this is greater than keq - there are now too many product molecules and too few reactant molecules for equilibrium to exist. thus the reverse reaction occurs more rapidly than the forward reaction. equilibrium is reached only by converting some of the hi to h2 and 12, so the reverse reaction is spontaneous. | if the conditions of example 7 are changed so that the hi concentration is 7. 1 x 10 - 3 mole liter - 1, in which direction is the reaction spontaneous? | under these conditions, since q equals keq within the limits of accuracy of the data, the system as described is at equilibrium, and neither the forward nor the backward reaction is spontaneous. ( both reactions are still taking place at the molecular level, of course, but they are balanced so their net effects cancel. ) the second use for equilibrium constants is to calculate the concentrations of reactants and products that will be present at equilibrium. | if a 1 - liter flask contains 1. 0 x 10 - 3 mole each of h2 and i2 at 448°c, what amount of hi is present when the gas mixture is at equilibrium? | the keq expression is treated as an ordinary algebraic equation, and solved for the hi concentration : you can verify that in example 7 the hi concentration was less than this equilibrium value ; in example 8 it was more ; and in example 9 it was just this value. | one - tenth of a mole, 0. 10 mole, of hydrogen iodide is placed in an otherwise empty 5. 0 liter flask at 448°c. when the contents have come to equilibrium, how much hydrogen and iodine will be in the flask? | from the stoichiometry of the reaction, the concentrations of h2 and i2 must be the same. for every mole of h2 and i2 formed, 2 moles of hi must decompose. let y equal the number of moles of
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subdomain_quantum_thermodynamics
| 0.608086
| 512
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HuggingFaceFW/fineweb-edu
|
<urn:uuid:0380ba0a-eb55-47d7-9ade-aefc9151e100>
| 8
| 0.6
|
2025-12-25T21:32:38.281058
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dissociation to hydrogen and iodine is favored much more. the hydrogen iodide - producing reaction is exothermic or heat emitting : ( if you check this figure against appendix 3, remember that this reaction involves gaseous iodine, not solid. ) if the external temperature of this reaction is lowered, the equilibrium is shifted in favor of the heat - emitting or forward reaction ; conversely, if the temperature is increased, the reverse reaction, producing h2 and i2 is favored. the equilibrium shifts so as to counteract to some extent the effect of adding heat externally ( raising the temperature ) or removing it ( lowering the temperature ). the temperature dependence of the equilibrium point is one example of a more general principle, known as le chatelier ' s principle : if an external stress is applied to a system at chemical equilibrium, then the equilibrium point will change in such a way as to counteract the effects of that stress. if the forward half of an equilibrium reaction is exothermic, then keq will decrease as the temperature increases ; if it is endothermic, keq will increase. only for a heat - absorbing reaction can the equilibrium yield of products be improved by increasing the temperature. a good way to remember this is to write the reaction explicitly with a heat term : then it is clear that adding heat, just like adding hi, shifts the reaction to the left. ( see figure 4 - 3. ) le chatelier ' s principle is true for other kinds of stress, such as pressure changes. the equilibrium constant, keq, is not altered by a pressure change at constant temperature. however, the relative amounts of reactants and products will change in a way that can be predicted from le chatelier ' s principle. the hydrogen - iodine reaction involves an equal number ( 2 ) of moles of reactants and product. therefore, if we double the pressure at constant temperature, the volume of the mixture of gases will be halved. all concentrations in moles liter - 1 will be doubled, but their ratio will be the same. in example 12, doubling the concentrations of the reactants and product does not change the equilibrium constant : - keq = - = 50. 51 thus the hydrogen - iodine equilibrium is not sensitive to pressure changes. notice that in this case keq does not have units, since the concentration units in the numerator and denominator cancel. in contrast, the dissociation of ammonia is affected by changes in pressure because the
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subdomain_quantum_thermodynamics
| 0.609172
| 512
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HuggingFaceFW/fineweb-edu
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<urn:uuid:0380ba0a-eb55-47d7-9ade-aefc9151e100>
| 16
| 0.6
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2025-12-25T21:32:38.292529
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motion machine that would deliver power without an energy source. from common sense and experience we know this to be impossible. this " common sense " is stated scientifically as the first law of thermodynamics, which will be discussed in chapter 15. a mathematician would call this a proof by contradiction : if we assume that a catalyst can alter keq, then we must assume the existence of a perpetual - motion machine. however, a perpetual - motion machine cannot exist ; therefore our initial assumption was wrong, and we must conclude that a catalyst cannot alter keq. in summary, keq is a function of temperature, but it is not a function of reactant or product concentrations, total pressure, or the presence or absence of catalysts. the relative amounts of substances at equilibrium can be changed by applying an external stress to the equilibrium mixture of reactants and products, and the change is one that will relieve this stress. this last statement, le chatelier ' s principle, enables us to predict what will happen to a reaction when external factors are changed, without having to make exact calculations. a spontaneous reaction is one that will take place, given enough time, without outside assistance. some spontaneous reactions are rapid, but time is not an element in the definition of spontaneity. a reaction can be almost infinitely slow and still be spontaneous. the net reaction that we observe is the result of competition between forward and reverse steps. if the forward process is faster, then products accumulate, and we say that the reaction is spontaneous in the forward direction. if the reverse process is faster, then reactants accumulate, and we say that the reverse reaction is the spontaneous one. if both forward and reverse processes take place at the same rate, then no net change is observed in any of the reaction components. this is the condition of chemical equilibrium. the ratio of products to reactants, each concentration term being raised to a power corresponding to the coefficient of that substance in the balanced chemical equation, is called the equilibrium constant, keq. ( see equation 4 - 8. ) it can be used to predict whether a given reaction under specified conditions will be spontaneous, and to calculate the concentrations of reactants and products at equilibrium. the reaction quotient, q, has a form that is identical with that of the equilibrium constant, keq, but q applies under nonequilibrium conditions as well. for a given set of conditions, if q is smaller than keq, the forward reaction is spontaneous ; if q is greater than keq,
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subdomain_quantum_thermodynamics
| 0.652963
| 512
|
HuggingFaceFW/fineweb-edu
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<urn:uuid:0380ba0a-eb55-47d7-9ade-aefc9151e100>
| 19
| 0.6
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2025-12-25T21:32:38.296415
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that of the equilibrium constant, keq, but q applies under nonequilibrium conditions as well. for a given set of conditions, if q is smaller than keq, the forward reaction is spontaneous ; if q is greater than keq, the reverse reaction is spontaneous ; and if q = keq, the system is at equilibrium. the equilibrium constant can be used with any convenient set of concentration units : moles liter - 1, pressure in atmospheres, or others. its numerical value will depend on the units of concentration, so one must be careful to match the proper values of keq and units when solving problems. if gas concentrations are expressed in moles liter - 1, the equilibrium constant is designated by kc ; if in atmospheres, by kp. just as partial pressure of the jth component of a gas mixture is related to moles per liter by pj = cjrt, so kp and kc are related by kp = kc ( rt ) δn, in which δn is the net change in number of moles of gas during the reaction. when some of the reactants or products are pure solids or liquids, they act as infinite reservoirs of material as long as some solid or liquid is left. their effect on equilibrium depends only on their presence, not on how much of the solid or liquid is present. their effective concentrations are constant, and can be incorporated into keq. in practice, this simply means omitting concentration terms for pure solids and liquids from the equilibrium - constant expression. evaporation of a liquid can be treated formally as a chemical reaction with the liquid as reactant and vapor as product. these conventions for writing concentration terms for a liquid permit us to write the equilibrium constant for evaporation as kp = pj where pj is the equilibrium vapor pressure of substance j. le chatelier ' s principle states that if stress is applied to a system at equilibrium the amounts of reactants and products will shift in such a manner as to minimize the stress. this means that for a heat - absorbing, or endothermic, reaction, keq increases as the temperature is increased, since carrying out more of the reaction is a way of absorbing some of the added heat. similarly, cooling increases keq for a heat - emitting or exothermic reaction. although the equilibrium constant keq is independent of pressure, and changing the total pressure on a reacting system does not alter keq directly, an increase in pressure does cause the reaction to shift in
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subdomain_quantum_thermodynamics
| 0.604573
| 512
|
HuggingFaceFW/fineweb-edu
|
<urn:uuid:0380ba0a-eb55-47d7-9ade-aefc9151e100>
| 20
| 0.6
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2025-12-25T21:32:38.297483
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