data/train/batch_000021.jsonl

{"text": "click on the image to see an enhanced diagram. heat is energy in transit from warmer systems to colder systems. heat is associated with the internal potential and kinetic energy ( an apparently disorganized molecular motion ) of a system. if heat is a form of energy associated to the particles \u2019 rotational, translational and vibratory movements, how does the heat move through the space between the sun and the earth, which density is extremely low? the answer is : heat could be transferred from warmed systems by radiation. the thermal radiation is electromagnetic radiation that consists of particles and waves, i. e. photons and waves, the same as visible light. thus, the radiative heat transfer can take place through vacuum. the energy always moves from a warmer system to a colder system. the energy which is moving from one system to another is known as heat. the transfer or dispersion of heat can occur by means of three main mechanisms, conduction, convection and radiation : conduction : it is the flow of heat through solids and liquids by vibration and collision of molecules and free electrons. the molecules of a given point of a system which are at higher temperature vibrate faster than the molecules of other points of the same system - or of other systems - which are at lower temperature. the molecules with a higher movement collide with the less energized molecules and transfer part of their energy to the less energized molecules of the colder regions of the structure. for example, the heat transfer by conduction through the bodywork of a car. metals are the best thermal conductors ; while non - metals are poor thermal conductors. for comparison, the thermal conductivity ( k ) of the copper is 401 w / m * k, while the thermal conductivity ( k ) of the air is 0. 0263 w / m * k. the thermal conductivity of the carbon dioxide ( co2 ) is 0. 01672 w / m * k, almost the thermal conductivity of an isolator. formula to calculate the conductivity gradient for a given system : q = - ka ( \u03b4 t / \u03b4 n ) where \u03b4 t / \u03b4 n is the temperature gradient in the direction of area a, and k is the thermal conductivity constant obtained by experimentation in w / m. k. convection : flow of heat through currents within a fluid ( liquid or gas ). convection is the displacement of volumes of a substance in a liquid or gaseous phase. when a mass of a fluid is heated up, for", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6426837688924495, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:e75d3108-a88b-48fc-9d90-3b168a47faff>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:35.295438"}
{"text": "w / m. k. convection : flow of heat through currents within a fluid ( liquid or gas ). convection is the displacement of volumes of a substance in a liquid or gaseous phase. when a mass of a fluid is heated up, for example when it is in contact with a warmer surface, its molecules are carried away and scattered causing that the mass of that fluid becomes less dense. for this reason, the warmed mass will be displaced vertically and / or horizontally, while the colder and denser mass of fluid goes down ( the low - kinetic - energy molecules displace the molecules in high - kinetic - energy states ). through this process, the molecules of the hot fluid transfer heat continuously toward the volumes of the colder fluid. for example, when heating up water on a stove, the volume of water at the bottom of the pot will be warmed up by conduction from the metallic bottom of the pot and its density decreases. given that it gets lesser dense, it shifts upwards up to the surface of the volume of water and displaces the upper - colder and denser - mass of water downwards, to the bottom of the pot. formula of convection : q = ha ( ts - t \u221e ) where h is for convective heat transfer coefficient, a is the area implied in the heat transfer process, ts is for the temperature of the system and t \u221e is a reference temperature. radiation : it is heat transfer by electromagnetic waves or photons. it does not need a propagating medium. the energy transferred by radiation moves at the speed of light. the heat radiated by the sun can be exchanged between the solar surface and the earth ' s surface without heating the transitional space. for example, if i place an object ( such as a coin, a car, or myself ) under the direct sunbeams, i will note in a little while that the object will be heated. the exchange of heat between the sun and the object occurs by radiation. the formula to know the amount of heat transferred by radiation is : q = e \u03c3 a [ ( \u03b4t ) ^ 4 ] where q is the heat transferred by radiation, e is the emissivity of the system, \u03c3 is the constant of stephan - boltzmann ( 5. 6697 x 10 ^ - 8 w / m ^ 2. k ^ 4 ), a is the area involved in the heat transfer by radiation, and ( \u03b4t ) ^ 4 is the difference of temperature between two systems to the fourth or higher power. a heat", "subdomain_id": "subdomain_quantum_thermodynamics", "similarity_score": 0.6198428093939448, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:e75d3108-a88b-48fc-9d90-3b168a47faff>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:35.297411"}
{"text": "^ - 8 w / m ^ 2. k ^ 4 ), a is the area involved in the heat transfer by radiation, and ( \u03b4t ) ^ 4 is the difference of temperature between two systems to the fourth or higher power. a heat sink is a system capable of absorbing heat from an object with which it is in thermal contact without a phase change or a significant variation in temperature. at earth ' s location, the outer space, the gravity field ( guth. 1999. pp. 29 - 31 ) and the false void are heat sinks. water has a specific heat of 4. 190 kj / kg. k, while air has a specific heat of 1. 0057 kj / kg. k, and soil have a specific heat of 0. 725 kj / kg. k. water has a specific heat higher than soil and air ; then, the thermal capacity of water is higher than the thermal capacity of the air and the soil. to a greater thermal capacity, a slower rate of dissipation of heat. the atmosphere and the soil don ' t maintain a load of heat for longer periods than water because they have a specific heat capacity lower than water, so water absorbs more heat for inreasing its temperature for a determined interval. for equal volumes ( 1kg, for example ), water absorbs more heat than air or soil. the absorbed heat will be transformed into kinetic and potential energy. a body with a high energy density will lose its inner energy slower than a body with a lower energy density. for example, if you have ten dollars and your friend has five dollars, and each one is obliged to spend one dollar per day, you will delay ten days to spend your money, while your friend will delay only five days to consume his money. in general, the soil and the air have independently 1 / 4 of the specific heat of water. for example, the specific heat of carbon dioxide is 850 j / kg \u00b0c ; to be precise, 4. 92 times less than the specific heat of water ; then, its thermal capacity will be less than the thermal capacity of water. for equal masses of the evaluated substances, at controlled temperatures and pressure, the carbon dioxide will release its internal heat five times faster than the water. if one kilogram of water at 30 \u00b0c is cooled by 10 \u00b0c in 10 minutes, one kilogram of carbon dioxide at 30 \u00b0c would be cooled by 10 \u00b0c in two minutes. the rule is : if you get it fast, you will lose it fast", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6242980100060818, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:e75d3108-a88b-48fc-9d90-3b168a47faff>", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:35.300012"}
{"text": "functions like the crystals of a glasshouse. this is, the properties of absorption and conduction of glass are similar to those of the atmospheric greenhouse gases \u2026 \u201d ( wilson, jerry d. college physics - 2nd edition ; p. 382. prentice hall inc. 1994 ). there are other authors who discuss thermal events similarly as the writers i have quoted in the previous paragraph ; i have found the same mistakes written on reports from nasa, noa, epa, etc. those unintentional faults have been inflated by some pseudo - environmentalists and politicians that enforce the erroneous concept of \" greenhouse gases \", \u201c anthropogenic global warming \u201d and \u201c manmade climate change \u201d, closing their eyes to the laws of thermodynamics, heat transfer, thermal expansion, physics laws, etc. the atmosphere is not a \u201c glass \u201d, nor acts like a glass. it either is a blanket that \u201c reradiates \u201d heat to the surface, or that obstructs convection. far from impeding convective heat transfer, gases allow convection. co2 is able to absorb the energy emitted by the ground and the oceans and transforms it into kinetic and potential energy. by these transformations from one class of energy into another, the co2 emits radiant energy ( energy in transit or heat ), which is transferred by convection to the upper atmosphere layers. after it has been transferred to the upper layers of the atmosphere, the heat is released to the outer space ( heat sink ). however, we have understood that the current concentration of carbon dioxide cannot be a source of \u201c global warming \u201d. we would need about 560 ppmv for increasing the earth \u2019 s surface temperature up to 0. 7 \u00b0c. the terrestrial atmosphere is a stratum composed by a mixture of gases ( air ) that wraps the earth and is retained by earth \u2019 s gravity. the atmosphere stratifies according to differences of density and temperature. nitrogen and oxygen are the predominant constituents in all layers, but each layer is less dense than the previous layer, starting up from the troposphere which is the denser layer ( density = magnitude of mass per unit of volume ; for example, the density of liquid water is 1 kg per liter ). the quantity of mass of air per unit of volume decreases as height increases. at sea level and 288. 2 k ( 15. 2 \u00b0c or 59. 36 \u00b0f ), the density of air is 1. 225 kg / m + e3 and its thermal conductivity is 0.", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6093276780283432, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:e75d3108-a88b-48fc-9d90-3b168a47faff>", "chunk_index": 5, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:35.310878"}
{"text": "for all great discoveries chemists are indebted to the \u201c balance \u201d \u2014 that incomparable instrument which gives permanence to every observation, dispels all ambiguity, establishes truth, detects error, and guides us in the true path of inductive science. the balance, once adopted as a means of investigating nature, put an end to the school of aristotle in physics. the explanation of natural phenomena by mere fanciful speculations, gave place to a true natural philosophy. fire, air, earth, and water, could no longer be regarded as elements. three of them could henceforth be considered only as significative of the forms in which all matter exists. everything with which we are conversant upon the surface of the earth is solid, liquid, or aeriform ; but the notion of the elementary nature of air, earth, and water, so universally held, was now discovered to belong to the errors of the past. fire was found to be but the visible and otherwise perceptible indication of changes proceeding within the, so called, elements. lavoisier investigated the composition of the atmosphere and of water, and studied the many wonderful offices performed by an element common to both in the scheme of nature, namely, oxygen : and he discovered many of the properties of this elementary gas. after his time, the principal problem of chemical philosophers was to determine the composition of the solid matters composing the earth. to the eighteen metals previously known were soon added twenty - four discovered to be constituents of minerals. the great mass of the earth was shown to be composed of metals in combination with oxygen, to which they are united in one, two, or more definite and unalterable proportions, forming compounds which are termed metallic oxides, and these, again, combined with oxides of other bodies, essentially different to metals, namely, carbon and silicium. if to these we add certain compounds of sulphur with metals, in which the sulphur takes the place of oxygen, and forms sulphurets, and one other body, \u2014 common salt, \u2014 ( which is a compound of sodium and chlorine ), we have every substance which exists in a solid form upon our globe in any very considerable mass. other compounds, innumerably various, are found only in small scattered quantities. the chemist, however, did not remain satisfied with the separation of minerals into their component elements, i. e. their analysis ; but he sought by synthesis, i. e. by combining", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6220342624410864, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:6a414e97-50c7-4a62-876f-e742ec3a65c7>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:35.377243"}
{"text": "improving the performance of platinum electrocatalysts in fuel cells 12 january 2007 the journal science and its online companion science express this week provide two reports from different research teams on efforts to improve the stability and performance of platinum electrocatalysts in pem fuel cells. scientists at the us department of energy \u2019 s ( doe ) brookhaven national laboratory have discovered that the addition of gold clusters to platinum electrocatalysts stabilizes them for use in fuel cells. a pem fuel cell converts hydrogen and oxygen into water and, as part of the process, produces electricity. hydrogen is oxidized when electrons are released and hydrogen ions are formed ; the released electrons supply current for an electric motor. oxygen is reduced by gaining electrons, and in reaction with hydrogen ions, water, the only byproduct of a fuel cell reaction, is produced. platinum electrocatalysts speed up these oxidation and reduction reactions ( orr ). in reactions during the stop - and - go driving of an electric car, however, the platinum dissolves, which reduces its efficiency as a catalyst \u2014 a major impediment for vehicle - application of fuel cells. under lab conditions that imitate the environment of a fuel cell, the brookhaven researchers added gold clusters to the platinum electrocatalyst, which kept it intact during an accelerated stability test. this test is conducted under conditions similar to those encountered in stop - and - go driving in an electric car. the research is reported in the 12 january 2007 edition of the journal science. fuel cells are expected to become a major source of clean energy, with particularly important applications in transportation. despite many advances, however, existing fuel - cell technology still has drawbacks, including loss of platinum cathode electrocatalysts, which can be as much as 45 percent over five days, as shown in our accelerated stability test under potential cycling conditions. using a new technique that we developed to deposit gold atoms on platinum, our team was able to show promise in helping to resolve this problem. the next step is to duplicate results in real fuel cells. \u2014 radoslav adzic, co - author in the unique method developed at brookhaven, the researchers displaced a single layer of copper with gold on carbon - supported platinum nanoparticles. after being subjected to several sweeps of 1. 2 volts, the gold monolayer transformed into three - dimensional clusters. using x - rays as probes at brookhaven \u2019 s national synchrotron light source, a scanning transmission microscope at brookhaven \u2019 s center for functional", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6089477505829058, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:10eb12ab-073b-481f-a025-a15ecd75f5d4>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:36.388256"}
{"text": "of 1. 2 volts, the gold monolayer transformed into three - dimensional clusters. using x - rays as probes at brookhaven \u2019 s national synchrotron light source, a scanning transmission microscope at brookhaven \u2019 s center for functional nanomaterials, and electrochemical techniques in the laboratory, the scientists were able to verify the reduced oxidation of platinum and to determine the structure of the resulting platinum electrocatalyst with gold clusters, which helped them to gain an understanding of the effects of the gold clusters. in the brookhaven experiment, the platinum electrocatalyst remained stable with potential cycling between 0. 6 and 1. 1 volts in more than 30, 000 oxidation - reduction cycles, imitating the conditions of stop - and - go driving. the gold clusters protected the platinum from being oxidized. our team \u2019 s research raises promising possibilities for synthesizing improved platinum - based catalysts and for stabilizing platinum and platinum - group metals under cycling oxidation / reduction conditions. \u2014 radoslav adzic this research is funded through the us department of energy \u2019 s hydrogen program. in a separate study published online in science express, researchers enhanced the performance of platinum electrocatalysts in fuel cells. the slow rate of the oxygen reduction reaction ( orr ) in pem fuel cell is a major limiter for automotive applications. the team from argonne national laboratory, the university of liverpool, lawrence berkeley national laboratory and the university of south carolina developed a pt3ni ( 111 ) catalyst that is 10 - fold more active for the oxygen reduction reaction than the corresponding pt ( 111 ) surface, and 90 - fold more active than current state - of - the - art pt / c catalysts. the pt3ni ( 111 ) surface has an unusual electronic structure ( d - band center position ) and arrangement of surface atoms in the near - surface region. under operating conditions relevant to fuel cells, its near - surface layer exhibits a highly structured compositional oscillation in the outermost and third layers are pt rich and the second atomic layer is ni rich. the weak interaction between the pt surface atoms and non - reactive oxygenated species increases the number of active sites for o2 adsorption. \u201c stabilization of platinum oxygen - reduction electrocatalysts using gold clusters \u201d ; j. zhang, k. sasaki, e. sutter, r. r. adzic ; science 12 january 2007 : vol. 315. no. 5809, pp. 220 - 222 doi : 10. 1126", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6345602917659241, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:10eb12ab-073b-481f-a025-a15ecd75f5d4>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:36.389827"}
{"text": "are purely imaginary and do not correspond to any experience. a theory of money would still be meaningful even if throughout history there had never been any indirect exchange. that such a theory would have no practical importance in a world that did not use money would in no way detract from the truth of its statements. because we study science for the sake of real life? and, it should be remembered, the desire for pure knowledge for its own sake is also a part of life? and not as a form of mental gymnastics, we generally do not mind forgoing the gratification that could be offered by a perfect, comprehensive system of the axioms of human action, a system so universal that it would comprise all thinkable categories of the conditions of action. instead, we are satisfied with the less universal system that refers to the conditions given in the world of experience. nevertheless, this reference to experience in no way changes the aprioristic character of our knowledge. in this connection, experience is of absolutely no concern to our thinking. all that we owe to experience is the demarcation of those problems that we consider with interest from problems that we wish to leave aside because they are uninteresting from the point of view of our desire for knowledge. hence, experience by no means always refers to the existence or nonexistence of the conditions of action, but often only to the presence of an interest in the treatment of a problem. in experience there is no socialist community ; nevertheless, the investigation of the economy of such a community is a problem that in our age arouses the greatest of interest. a theory of action could conceivably be constructed on the assumption that men lacked the possibility of understanding one another by means of symbols, or on the assumption that men? immortal and eternally young? were indifferent in every respect to the passage of time and therefore did not consider it in their action. the axioms of the theory could conceivably be framed in such universal terms as to embrace these and all other possibilities ; and it would be conceivable to draw up a formal praxeological system patterned after the science of logic or the science built upon the axioms of, for example, hilbertian geometry. we forgo these possibilities because conditions that do not correspond to those we encounter in our action interest us only in so far as thinking through their implications in imaginary constructions enables us to further our knowledge of action under given conditions. the method actually employed by economists in the treatment of their problems can be seen with", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6098385130681067, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:05f91e7d-a1ea-4985-8bd2-bc3d5b0e8810>", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:37.308326"}
{"text": "and dust cloud that formed the planets. thus, the meteorite perhaps reflects an early stage of evolution of complex carbon compounds in space. the science paper notes that many of the organic compounds found in the tagish lake sample have also been found in other meteorites, but that the distribution of compounds is different, particularly for the amino acids and carboxylic acids. \" we found some compounds identical to some in murchison that show the same - interstellar connection - in their abundance of deuterium ( heavy hydrogen ), while some others differ from murchison in amounts and variety, \" says pizzarello, meaning that for some groups of organic molecules, only the simplest species were found in tagish lake, as opposed to a broader distribution of species found in murchison. \" overall, tagish lake represents a simpler, more unaltered stage than we have seen before. \" other members of the research team include yongsong huang from the department of geological sciences at brown university ; luann becker from the institute for crustal studies at the university of california santa barbara ; robert j. poreda from the department of earth and environmental sciences, university of rochester ; george cooper from the nasa ames research center ; and ronald a. nieman and michael williams, both also from asu. \" some people have been disappointed that we found virtually no amino acids, but scientifically this is very exciting, \" pizzarello said. \" this meteorite shows the complexity of the history of organic compounds in space - it seems to have had a distinct evolution. \" pizzarello notes that while the meteorites like tagish lake may lack amino acids, they still could have contributed the molecular precursors of biomolecules that are necessary for the origin of life. louis allamandola, astrochemist with the nasa ames research center and nai member, says the absence of amino acids and other simple organic molecules could mean the meteorite was exposed to high heat or energy levels during its travels through space. \" the main signature of the meteorite is that of sooty, cross polymerized aromatic material - - probably much like the black soot from a diesel engine or sooty candle flame, \" says allamandola. \" from an organic chemical point of view, this is the kind of material you get when you heat any organic material above about 400 degrees celsius ( 752 degrees fahrenheit ). so, all this means is that this particular rock had a different history from that of the", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6002155408891026, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:799b4de9-78b6-443d-93be-2921035b705e>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:37.392330"}
{"text": "? religion is a set of beliefs which allow us to understand and categorize our world and our place in it. a set of beliefs which define our culture, our expectations, our views of people and behaviors we expect. i have found several different... religion & philosophy > > religions function object functors in c and c is described in multiple online sources, as addition to our editors ' articles, see section below for printable documents, function object functors in c and c books and related discussion. suggested pdf resources - c + + stl function object functor program examples - such an object is called a function object, or functor. - sometimes you can. check the best selling c / c + + and stl books at amazon. - math 614 : lecture notes - let f, g : c \u2192 d be functors ( in this lecture, all functors are covariant. ). a natural functors. - adjoint functors in algebra, topology and mathematical logic - ic : c\u2192c which maps each object and morphism to itself.. are functors, while \u03c6 is a function which assigns to each pair of objects x \u2208 c,. - a framework for higher - order functions in c + + - abstract. c and c + + allow passing functions as arguments to in c + + by enclosing a function inside an object such that the jects \u201c functors \u201d, and further developed by kuhne. [ kuh95 ]... suggested web resources - function object - wikipedia, the free encyclopedia - a function object, also called a functor, functional, or functionoid, is a a callback in procedural languages, such as c, may be performed by using function pointers... - c + + functors - and their uses - stack overflow - a functor is a object which acts like a function. - the function pointer tutorials - functors - jan 6, 2005 4. functors to encapsulate c and c + + function pointers with a pointer to an object and a pointer to a member function in its constructor. - functors - function objects in c + + - functors : function objects in c + +. both c and c + + support function pointers, which provide a way to pass around instructions on how to perform an operation. - callbacks in c + + using template functors - the simplest callback mechanism is a pointer - to - function,", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6200863828781367, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:c12fa2ee-ff56-4d2b-a158-34e9aa6db225>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:37.768227"}
{"text": "accomplished in two different ways. the first is to use a numerical method, such as runge - kutta to approximate the solution. otherwise, we can linearize the system of equations and find the solutions around the critical points to find an approximate solution. one way to do this is by the nullcline approach. we set s \u2019 and i \u2019 to zero, and solve the resulting system, obtaining this is then the critical point where the equilibrium is defined. when shown in the si - plane, this point gives the solution to the linear portion of the system around which the nonlinear portion oscillates. since the system is stable, it should converge to this point as this value of s is also the threshold defined by the threshold theorem. in order for i to be positive ( nonzero ) at equilibrium, this value must be less than one. if i is not positive, then there are no infected people at equilibrium and there is no epidemic. then, for a small enough ratio of r to c, decreasing the contact rate can have a significant effect, and the severity of the epidemic can be reduced or even eliminated by the implementation of public health measures such as isolation of infectives or vaccination of susceptibles. this solution suggests that there should be recurring outbreaks of diminishing severity after the initial outbreak. this pattern is not quite what is observed, though. in fact, it is found that the severity of epidemics can depend on a number of other factors, including seasonal changes. the model can then be refined by making b a function of time rather than a constant, to portray a higher susceptibility during winter months than during the summer. by adding this seasonality function, apparently random fluctuations that look chaotic are observed. ( ref 2 ) the system, though perhaps aperiodic, is stable though, so not actually chaotic.", "subdomain_id": "subdomain_quantum_simulation", "similarity_score": 0.6033570040574094, "token_count": 377, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:a0115c48-444f-41d4-8d8f-de912de8b4a8>", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:37.840246"}
{"text": "dec. 8, 2009 nanoscale machines expected to have wide application in industry, energy, medicine and other fields may someday operate far more efficiently thanks to important theoretical discoveries concerning the manipulation of famous casimir forces that took place at the u. s. department of energy ' s ames laboratory. the groundbreaking research, conducted through mathematical simulations, revealed the possibility of a new class of materials able to exert a repulsive force when they are placed in extremely close proximity to each other. the repulsive force, which harnesses a quantum phenomenon known as the casimir effect, may someday allow nanoscale machines to overcome mechanical friction. though the frictional forces in nanoscale environments are small, they significantly inhibit the function of the tiny devices designed to operate in that realm, explained costas soukoulis, a senior physicist at the ames lab and distinguished professor of physics at iowa state university, who led the research effort. soukoulis and his teammates, including ames laboratory assistant scientist thomas koschny, were the first to study the use of exotic materials known as chiral metamaterials as a way to harness the casimir effect. their efforts have demonstrated that it is indeed possible to manipulate the casimir force. the findings were published in the sept. 4, 2009 issue of physical review letters. understanding the importance of their discovery requires a basic understanding of both the casimir effect and the unique nature of chiral metamaterials. the casimir effect was named after dutch physicist hendrik casimir, who postulated its existence in 1948. using quantum theory, casimir predicted that energy should exist even in a vacuum, which can give rise to forces acting on the bodies brought into close proximity of each other. for the simple case of two parallel plates, he postulated that the energy density inside the gap should decrease as the size of the gap decreases, also meaning work must be done to pull the plates apart. alternatively, an attractive force that pushes the plates closer together can be said to exist. casimir forces observed experimentally in nature have almost always been attractive and have rendered nanoscale and microscale machines inoperable by causing their moving parts to permanently stick together. this has been a long - standing problem that scientists working on such devices have struggled to overcome. remarkably, this new discovery demonstrates that a repulsive casimir effect is possible using chiral metamaterials. chiral materials share an interesting characteristic : their molecular structure prevents them from being superimposed over a reverse copy of themselves, in the same way a human hand cannot fit perfectly", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6670300465647394, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:8dd4d113-9bac-4b8e-bad4-be3b9931562e>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:37.853250"}
{"text": "a repulsive casimir effect is possible using chiral metamaterials. chiral materials share an interesting characteristic : their molecular structure prevents them from being superimposed over a reverse copy of themselves, in the same way a human hand cannot fit perfectly atop a reverse image of itself. chiral materials are fairly common in nature. the sugar molecule ( sucrose ) is one example. however, natural chiral materials are incapable of producing a repulsive casimir effect that is strong enough to be of practical use. for that reason, the group turned its attention to chiral metamaterials, so named because they do not exist in nature and must instead be made in the lab. the fact that they are artificial gives them a unique advantage, commented koschny. \" with natural materials you have to take what nature gives you ; with metamaterials, you can create a material to exactly meet your requirements, \" he said. the chiral metamaterials the researchers focused on have a unique geometric structure that enabled them to change the nature of energy waves, such as those located in the gap between the two closely positioned plates, causing those waves to exert a repulsive casimir force. the present study was carried out using mathematical simulations because of the difficulties involved in fabricating these materials with semiconductor lithographic techniques. while more work needs to be done to determine if chiral materials can induce a repulsive casimir force strong enough to overcome friction in nanoscale devices, practical applications of the casimir effect are already under close study at other doe facilities, including los alamos and sandia national laboratories. both have expressed considerable interest in using the chiral metamaterials designed at ames laboratory to fabricate new structures and reduce the attractive casimir force, and possibly to obtain a repulsive casimir force. funding for this research was provided by the doe office of science. other social bookmarking and sharing tools : note : materials may be edited for content and length. for further information, please contact the source cited above. - zhao et al. repulsive casimir force in chiral metamaterials. physical review letters, 2009 ; 103 ( 10 ) : 103602 doi : 10. 1103 / physrevlett. 103. 103602 note : if no author is given, the source is cited instead.", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6485317839660873, "token_count": 472, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:8dd4d113-9bac-4b8e-bad4-be3b9931562e>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:37.856237"}
{"text": "tat \u00b7 ing causing a loss of strength or energy. weakening, or reducing the strength of. mentioned in : stress reduction, and often its effects linger even after returning home. what can be done to enhance the military ' s capacities to operate in such complex environments while simultaneously protecting against the stressors inherent in them? this article proposes a new training program for both improving operational effectiveness and building resilience to the stressors of deployment : mindfulness - based mind fitness training ( mmft mmft monthly mecha fighting tournament mmft method of moments plus fourier transform, pronounced m - fit ). this program includes techniques and exercises that previous research in civilians has demonstrated to be effective at enhancing the capacities central to mind fitness, such as mental agility, emotion regulation, attention, and situational awareness. importantly, these exercises appear to achieve improvements in mind fitness by changing brain structure and function so that brain processes are more efficient. our pilot research, conducted in pre - deployment marine reservists, suggests that mmft is similarly successful at bolstering mind fitness and building resilience against stressors in a military cohort. drawing on the well - documented theory of neuroplasticity, which asserts that experience changes the brain, this article argues that mind fitness training could complement the military ' s existing stress inoculation inoculation, in medicine, introduction of a preparation into the tissues or fluids of the body for the purpose of preventing or curing certain diseases. the preparation is usually a weakened culture of the agent causing the disease, as in vaccination against training by developing skills to promote resilience against stress and trauma so that warriors can execute their missions more effectively. stress can degrade performance a variety of research indicates that harmful conditions such as chronic stress, neglect, and abuse can produce harmful changes in the brain. ( 3 ) stress is produced by real or imagined events that are perceived to threaten an individual ' s physical and mental well - being. today, stress is commonly understood to mean external events or circumstances, and as a result, we tend to think of stress as something external to us. however, stress is actually a perceived, internal response. the right amount of stress will allow a decisionmaker to function at peak performance. however, excessive stress has biological and psychological consequences that reduce the capacity to process new information and learn. stress may also bias decisionmaking more toward reactive, unconscious emotional choices. recent empirical research about decisionmaking in stressful military environments demonstrates that trauma and stress lead to deficits in cognitive functioning", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6073578802293494, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:46f3d515-bb26-4641-9bf2-a578f41b7bb4>", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:38.136736"}
{"text": "( adj. ) also spelled analogue, describes a device or system that represents changing values as continuously variable physical quantities. a typical analog device is a clock in which the hands move continuously around the face. such a clock is capable of indicating every possible time of day. in contrast, a digital clock is capable of representing only a finite number of times ( every tenth of a second, for example ). in general, humans experience the world analogically. vision, for example, is an analog experience because we perceive infinitely smooth gradations of shapes and colors. when used in reference to data storage and transmission, analog format is that in which information is transmitted by modulating a continuous transmission signal, such as amplifying a signal ' s strength or varying its frequency to add or take away data. for example, telephones take sound vibrations and turn them into electrical vibrations of the same shape before they are transmitted over traditional telephone lines. radio wave transmissions work in the same way. computers, which handle data in digital form, require modems to turn signals from digital to analog before transmitting those signals over communication lines such as telephone lines that carry only analog signals. the signals are turned back into digital form ( demodulated ) at the receiving end so that the computer can process the data in its digital format. contrast with digital.", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.640278783681143, "token_count": 267, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:d86e8bcb-d514-4c89-9392-237c0a5986d8>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:38.285104"}
{"text": "scientists have apparently broken the universe \u2019 s speed limit. for generations, physicists believed there is nothing faster than light moving through a vacuum \u2014 a speed of 186, 000 miles per second. but in an experiment in princeton, n. j., physicists sent a pulse of laser light through cesium vapor so quickly that it left the chamber before it had even finished entering. the pulse traveled 310 times the distance it would have covered if the chamber had contained a vacuum. researchers say it is the most convincing demonstration yet that the speed of light \u2014 supposedly an ironclad rule of nature \u2014 can be pushed beyond known boundaries, at least under certain laboratory circumstances. \u201c this effect cannot be used to send information back in time, \u201d said lijun wang, a researcher with the private nec institute. \u201c however, our experiment does show that the generally held misconception that \u2018 nothing can travel faster than the speed of light \u2019 is wrong. \u201d the results were published in thursday \u2019 s issue of the journal nature. the achievement has no practical application right now, but experiments like this have generated considerable excitement in the small international community of theoretical and optical physicists. previously thought impossible \u201c this is a breakthrough in the sense that people have thought that was impossible, \u201d said raymond chiao, a physicist at the university of california at berkeley who was not involved in the work. chiao has performed similar experiments using electric fields. in the latest experiment, researchers at nec developed a device that fired a laser pulse into a glass chamber filled with a vapor of cesium atoms. the researchers say the device is sort of a light amplifier that can push the pulse ahead. previously, experiments have been done in which light also appeared to achieve such so - called superluminal speeds, but the light was distorted, raising doubts as to whether scientists had really accomplished such a feat. the laser pulse in the nec experiment exits the chamber with almost exactly the same shape, but with less intensity, wang said. the pulse may look like a straight beam but actually behaves like waves of light particles. the light can leave the chamber before it has finished entering because the cesium atoms trade energy with the leading edge of the waves as they pass through. this produces an almost identical light pulse that exits the chamber and travels about 60 feet before the main part of the laser pulse finishes entering the chamber, wang said. wang said the effect is possible only because light has no mass ; the same thing cannot be done with physical objects. the princeton experiment and others like it test", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6216660230845026, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:407aeee2-2230-4a8f-8647-4aed4b649a2d>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:38.428389"}
{"text": "about 60 feet before the main part of the laser pulse finishes entering the chamber, wang said. wang said the effect is possible only because light has no mass ; the same thing cannot be done with physical objects. the princeton experiment and others like it test the limits of the theory of relativity that albert einstein developed nearly a century ago. according to the special theory of relativity, the speed of particles of light in a vacuum, such as outer space, is the only absolute measurement in the universe. the speed of everything else \u2014 rockets or inchworms \u2014 is relative to the observer, einstein and others explained. only in the lab in everyday circumstances, an object cannot travel faster than light. the princeton experiment and others change these circumstances by using devices such as the cesium chamber rather than a vacuum. ultimately, the work may contribute to the development of faster computers that carry information in light particles. not everyone is convinced the nec scientists did what they claim. aephraim steinberg, a physicist at the university of toronto, said the light particles coming out of the cesium chamber may not have been the same ones that entered, so he questions whether the speed of light was broken. still, the work is important, he said : \u201c the interesting thing is how did they manage to produce light that looks exactly like something that didn \u2019 t get there yet? \u201d", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6561037404034129, "token_count": 275, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:407aeee2-2230-4a8f-8647-4aed4b649a2d>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:38.429772"}
{"text": "when gordon moore made his observation in 1965 that the number of transistors integrated on a single silicon chip is doubling roughly every two years, the only logical end point for such a trend would be a transistor made from a single atom. this point has now been reached. writing in nature nanotechnology, michelle simmons from the university of new south wales in sydney and colleagues report a single - atom transistor, the world \u2019 s smallest, on a silicon chip. the transistor is based on current flowing through a single atom of phosphorus embedded in a silicon wafer. phosphorus is a natural choice for such a transistor, as it is relatively easy to integrate into silicon. there it acts as an electron donor because it has an additional electron compared to silicon. this additional charge can be used for conventional electronic devices such transistor, but also more complex schemes are possible. for example, the magnetic property of this single excess electron, its spin, can be used for new types of quantum computing. indeed, i have previously blogged about such efforts from another research group in sydney using multiple phosphorus atoms for silicon - based quantum computing. one of the key challenges in making a single - atom transistor is to place a single phosphorus atom into silicon in a controlled fashion. here, this is achieved by the careful placement of three phosphine ( ph3 ) molecules on the surface of silicon using a scanning tunneling microscsope. in a number of reaction steps these molecules dissociate and cause the ejection of a silicon atom from the surface and the incorporation of a single phosphorus atom in its place. once incorporated into silicon, the energy level of the phosphorus \u2019 outer electron states lies below that of the surrounding silicon. the precise match between silicon and phosphorus energy levels can be controlled by the electrical potential applied between two gate electrodes on either side ( see figure on the right ). this voltage controls the electric current between source and drain, and through the atom. if the energy levels of silicon and the phosphorus atom do match up, it is possible for electrons to pass through the phosphorous atom one by one. if the voltage between the two gates is set so that the silicon and phosphorus energy levels do not match up, there is no electric current. there are, however, a few drawbacks in the present approach. so far this transistor only works for really low temperatures, barely above absolute zero. and in the current implementation the contacting electrodes are still several tens of nanomet", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6029873969215619, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:fbc131ce-7b22-4c74-8836-c0c100759094>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:38.447763"}
{"text": ". there are, however, a few drawbacks in the present approach. so far this transistor only works for really low temperatures, barely above absolute zero. and in the current implementation the contacting electrodes are still several tens of nanometres apart \u2013 hardly on the single atom scale. also, the fabrication of the structure with a scanning tunnelling microscope doesn \u2019 t allow to make billions of them in the same efficient way as commercial computer chips are fabricated. still, such single atom transistors could already be of interest for the quantum computing schemes investigated for phosphorus atoms, where the low temperature is less of an issue. either way, considering that according to gordon moore \u2019 s law commercial silicon transistors are only expected to reach single atom scales beyond 2020, this study certainly is ahead of the curve. fuechsle, m., miwa, j., mahapatra, s., ryu, h., lee, s., warschkow, o., hollenberg, l., klimeck, g., & simmons, m. ( 2012 ). a single - atom transistor nature nanotechnology doi : 10. 1038 / nnano. 2012. 21 the university of new south wales has produced a youtube video explaining these findings.", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6323482730167191, "token_count": 264, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:fbc131ce-7b22-4c74-8836-c0c100759094>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:38.448512"}
{"text": "power, which they see as being essential for laying the foundations for a transitional withering of the state towards communism ( stateless society ). in this state, the vanguard party would act as a central nucleus in the organisation of socialist society, presiding over a single - party political system. leninism rejects political pluralism, seeing it as divisive and destructive. instead, leninism advocates the concept of democratic centralism as a process to ensure the voicing of concern and disagreement and to refine policy. generally, the purpose of democratic centralism is \" diversity in ideas, unity in action. \" leninist revolutionary theory alongside marxist economic theory forms the ideology of marxism - leninism. after lenin ' s death in 1924, leninism branched into multiple ( sometimes opposing ) interpretations, including trotskyism, stalinism, and maoism. \" socialist dreams turned into the socialist struggle of millions only when marx ' s scientific socialism had linked up the urge for change with the struggle of a definite class. outside the class struggle, socialism is either a hollow phrase or a naive dream. \" \u2014 vladimir lenin stalinism was the political system of the soviet union and the countries within the soviet sphere of influence during the leadership of joseph stalin. the term usually defines the style of a government rather than an ideology. the ideology was officially marxism - leninism theory, reflecting that stalin himself was not a theoretician, in contrast to marx and lenin, and prided himself on maintaining the legacy of lenin as a founding father for the soviet union and the future socialist world. stalinism is an interpretation of their ideas, and a certain political regime claiming to apply those ideas in ways fitting the changing needs of soviet society, as with the transition from \" socialism at a snail ' s pace \" in the mid - twenties to the rapid industrialization of the five - year plans. the main contributions of stalin to communist theory were : - the groundwork for the soviet policy concerning nationalities, laid in stalin ' s 1913 work marxism and the national question, praised by lenin. - socialism in one country, stating that communists should attain socialism in their own country as a prelude to internationalising. - the theory of aggravation of the class struggle along with the development of socialism, a theoretical base supporting the repression of political opponents as necessary. the legitimacy of stalin ' s claim to the role of leadership in the soviet union ( and thus the international communist movement as a whole ) is a matter of some debate. advocates of stalinism cite both lenin ' s praising of the", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6076960801557149, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:ce538435-7f6b-422f-a441-c99fc232150b>", "chunk_index": 13, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:39.650839"}
{"text": "introduction to linux a protocol is, simply put, a set of rules for communication. in order to get data over the network, for instance an e - mail from your computer to some computer at the other end of the world, lots of different hard - and software needs to work together. all these pieces of hardware and the different software programs speak different languages. imagine your e - mail program : it is able to talk to the computer operating system, through a specific protocol, but it is not able to talk to the computer hardware. we need a special program in the operating system that performs this function. in turn, the computer needs to be able to communicate with the telephone line or other internet hookup method. and behind the scenes, network connection hardware needs to be able to communicate in order to pass your e - mail from one appliance to the other, all the way to the destination computer. all these different types of communication protocols are classified in 7 layers, which are known as the open systems interconnection reference model, the osi model for short. for easy understanding, this model is reduced to a 4 - layer protocol description, as described in the table below : table 10 - 1. the simplified osi model | layer name | | layer protocols | | application layer | | http, dns, smtp, pop,... | | transport layer | | tcp, udp | | network layer | | ip, ipv6 | | network access layer | | ppp, pppoe, ethernet | each layer can only use the functionality of the layer below ; each layer can only export functionality to the layer above. in other words : layers communicate only with adjacent layers. let ' s take the example of your e - mail message again : you enter it through the application layer. in your computer, it travels down the transport and network layer. your computer puts it on the network through the network access layer. that is also the layer that will move the message around the world. at the destination, the receiving computer will accept the message through it ' s own network layer, and will display it to the recepient using the transport and application layer. | it ' s really much more complicated | the above and following sections are included because you will come across some networking terms sooner or later ; they will give you some starting points, should you want to find out about the details. linux supports many different networking protocols. we list only the most important : the transport control protocol and the internet protocol", "subdomain_id": "subdomain_quantum_cryptography", "similarity_score": 0.6043787773076847, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:fb92407e-57f6-4374-ae92-d9541042dd5e>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:40.113675"}
{"text": "search course communities : one - variable calculus resources particular resources may be found by either a keyword search or an advanced search. see these options up and to your left. or you may browse for resources under the following topics : - general tools : graphers and cas - general collections of applets : materials that cover a wide range of multivariable calculus topics. - background : resources to help students with things they should know - history of calculus : - continuity and limits : examples, limits of a function - theoretical issues : more on continuity, intermediate value theorem, maximum value theorem, mean value theorem, etc. - functions in general, graphers and definitions : - calculus functions : trigonometric, exponential, logarithms, hyperbolic, inverse functions - differentiation, calculation rules : - differentiation, definition and elementary application : - differentiation, general applications : concavity, related rates, optimization - differential equations : initial value problems, first - order odes, slope fields, euler ' s method, systems - antidifferentiation : rules - fundamental theorem : both parts - integration, motivation and definition : - integration, applications : - integration methods : - numerical integration : euler ' s method, trapezoidal rule, mid - point rule, simpson ' s rule, rk - methods - infinite limits, function values and integrals : - infinite limits, sequences and series : - function approximation : taylor polynomials discuss this course start a new discussion thread periodical articles for student readings it would be helpful to have a place where links to articles from math horizons, college mathematics journal and mathematics magazine could be collected according to subject. for example, having a list of articles suitable for students in multivariate calculus when talking about double integrals. the course community could have a forum to house member suggestions. perhaps journal editors could forward suggestions as part of the standard review process. add your reply", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6111598446979298, "token_count": 384, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:263ad2be-e2e5-41f9-821b-2004206ee8e5>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:40.185984"}
{"text": "filamentary structures in our milky way galaxy are apparent at large scales ( as shown in this planck image, on the right ) and small scales ( as seen in the herschel image on the left ). this planck image, covering a portion of the sky about 55 degrees in total extent, was obtained by the planck high frequency instrument at a frequency of 857 gigahertz ( corresponding to a wavelength of 350 micrometers ). the bright horizontal band corresponds to the plane of our spiral galaxy, which is seen in cross - section from our vantage point. the colors in the planck images represent the intensity of heat radiation by dust. this planck image was obtained during the first planck all - sky survey, which began in mid - august 2009. by mid - march 2010, more than 98 percent of the sky had been observed. the second sky scan is underway, but, because of the way planck surveys the sky, the first scan won ' t be 100 percent complete until late - may 2010. planck is a european space agency mission, with significant participation from nasa. nasa ' s planck project office is based at jpl. jpl contributed mission - enabling technology for both of planck ' s science instruments. european, canadian, u. s. and nasa planck scientists will work together to analyze the planck data. more information is online at http : / / www. nasa. gov / planck and http : / / www. esa. int / planck.", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.6061251014583, "token_count": 295, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:47a9584f-4f7d-48cd-99b0-46962a4c0f49>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:40.609638"}
{"text": "table - top test targets quantum foam nov 29, 2012 15 comments one of the biggest challenges in physics \u2013 finding evidence for quantum gravity \u2013 could be tackled using a simple table - top experiment, according to jacob bekenstein from the hebrew university of jerusalem. bekenstein, who is best known for studying the thermal properties of black holes, has come up with an interesting new proposal for using single photons to probe what is known as \" quantum foam \". the foam, which was introduced in 1955 by the us physicist john wheeler, is believed to exist on length scales so small that quantum fluctuations affect space \u2013 time. bekenstein ' s proposal is the latest effort in the quest to understand how quantum mechanics can be unified with einstein ' s general theory of relativity \u2013 a problem that has eluded physicists since they first began to understand the quantum and relativistic worlds in the early 20th century. one of the main reasons why physicists have struggled with developing a theory of quantum gravity is a complete lack of experimental evidence. the problem is that the effects of quantum gravity are only expected to be measurable over extremely small distances. some theories of quantum gravity suggest that experiments must probe distances smaller than the planck length, which is 1. 61 \u00d7 10 \u2013 35 m. probing this scale using an accelerator would involve colliding particles at enormous energies of more than 1016 tev. this would be well beyond the capabilities of the large hadron collider, which has a maximum collision energy of 14 tev, or indeed of any conceivable future collider. bekenstein ' s proposal, in contrast, is much more modest ; he says it could be done in a small physics lab mostly using existing equipment. photons at the ready the experiment would involve firing single photons at a piece of glass or crystal, suspended by a tiny thread. when the photon moves from the vacuum into the material, it loses speed because the material has a higher refractive index than that of the vacuum. the result is that a tiny amount of momentum is transferred to the material, causing it to move an extremely small distance. in the case of a blue photon with a wavelength of 445 nm, bekenstein says it would cause a 150 mg piece of high - lead glass to deflect by about 2 \u00d7 10 \u2013 35 m, which is on a par with the planck length. the bottom line is that if a photon is detected on the other side of the material, it means the mass was deflected by a distance", "subdomain_id": "subdomain_quantum_metrology", "similarity_score": 0.6656076324869358, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:c43d7f3a-b1d6-4607-8053-534f6b355ede>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:40.619719"}
{"text": "photons lost in a maze enhancing the interaction between light and matter is the essence of many research disciplines, including quantum information science, energy harvesting and optical biosensing. the traditional method has been to strongly confine light in, for example, a highly ordered nanocavity. surprisingly, an alternative approach to confinement of waves exists, originally proposed by philip anderson, and for which he was awarded the nobel prize in physics. using this approach, disordered materials are employed, giving rise to random and multiple scattering of the propagating light waves. for a certain amount of randomness of the structures, so - called anderson localized modes form spontaneously : light is trapped in a maze. a challenge in this research field has been to determine how well light can be confined based on random disorder. in a recent paper in new journal of physics researchers from the quantum photonics group at dtu fotonik have developed an efficient method for exciting anderson - localized modes by embedding nanoscopic light sources ( so - called quantum dots ) inside the disordered material. by analyzing the statistics of the emitted light, the quality and extent of light confinement can be extracted. surprisingly, the subtle interplay between the amount of disorder and the underlying periodic structure of the system studied can be exploited to confine light very efficiently, proving the potential of employing disorder for enchancement of light \u2013 matter interaction.", "subdomain_id": "subdomain_quantum_optics", "similarity_score": 0.7040222104494036, "token_count": 279, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:b3dc7260-f3ee-4673-852d-cdf094ddaa69>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:40.651904"}
{"text": "| diamondoid monolayers as monochromatic electron source | diamondoids are nanometer - sized molecules that feature diamond - crystal cage structures. adamantane, the smallest member in the family, consists of one cage structure, diamantane two, triamantane three, tetramantane four, and so on. on all of these, the dangling bonds on the outer surfaces are terminated by hydrogen atoms. because of their potential to possess novel properties of both diamond and nanomaterial, intensive efforts have been made to synthesize the larger diamondoid molecules, but to no avail. this situation was finally changed in 2003 when significant quantities of higher diamondoids were found in petroleum by researchers in moleculardiamond technologies. now, scientists from berkeley lab, stanford university, lawrence livermore national laboratory, and germany have used photoelectron spectroscopy at the als to reveal an intriguing feature : monochromatized electron emission from a self - assembled monolayer of diamondoids. this discovery has immediately attracted the attention of people who are searching for materials for next - generation electron emitters. materials for electron emitters have long been sought because electrons emitted into vacuum can be precisely controlled and easily integrated into elaborate devices. they lie at the heart of a number of modern technologies, such as field - emission flat - screen displays, electron microscopes, electron lithography, and next - generation free - electron lasers. for electron emitters, one of the biggest challenges is to develop large, uniform surfaces that emit electrons with a sharp energy distribution. in the late 1970s, scientists found that hydrogen - terminated diamond surfaces are characterized by negative electron affinity ( nea ), meaning for electrons, the energy level of the vacuum is lower than that of the diamond conduction bands. at surfaces with nea, electrons excited into the conduction band will spontaneously fall out into vacuum even at low temperature. thus, nea - based electron emitters have several advantages over conventional emitters. they exhibit electron emission at extremely low bias voltage ( zero in the ideal case ), and the energy distribution of the emitted electron is extremely narrow. however, two critical issues prevented nea semiconductors from being used in commercialized products. one is the nonuniform emission normally observed on diamond surfaces. the other is the difficulty of supplying electrons to the emission surface, because diamond and other nea semiconductors are wide - gap materials with low electron conductivity. diamondoids, being diamond - like nanoclusters, provide us with the opportunity to sustain the", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.652843132374576, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:93b4ecea-e98a-462c-a6b9-fe9279c80cd0>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:41.302826"}
{"text": "is the difficulty of supplying electrons to the emission surface, because diamond and other nea semiconductors are wide - gap materials with low electron conductivity. diamondoids, being diamond - like nanoclusters, provide us with the opportunity to sustain the nea feature of diamond while avoiding the conventional problems of bulk nea materials. toward this end, the collaborators replaced one of the hydrogen atoms on the surface of tetramantane ( four - cage diamondoids ) with a thiol group ( hydrogen + sulfur ). this substitution chemically \" functionalizes \" the tetramantane, i. e., it promotes bonding with other molecules, enabling it to form more complex structures, like nanosized tinker toys. the researchers found that these diamondoid \u2013 thiol complexes would then self - assemble into a uniform monolayer on metal surfaces such as silver or gold. photoelectron spectroscopy was then performed on the tetramantane \u2013 thiol monolayers at beamline 10. 0. 1, where a strong, sharp peak was detected. the outstanding peak observed in the spectra is a strong indication of nea. furthermore, up to 68 % of all the emitted electrons were within this single energy peak, with a width of less than 0. 5 ev. this is several times as strong as the same measurement for bulk diamond. technologically, this means most electrons are emitted from the diamondoid monolayer at the same energy, i. e., speed. the result directly shows that diamondoid monolayers can be superior to conventional materials as electron emitters. the molecules can be purified and functionalized under precise control. they can be inexpensively self - assembled into large - area, uniform monolayers. more importantly, they perform better than previous materials in terms of the energy distribution of the emitted electrons. further investigations are under way to fully understand this striking phenomenon, as well as to make real devices based on diamondoids. research conducted by w. l. yang, n. mannella, k. tanaka, and x. j. zhou ( stanford university and als ) ; j. d. fabbri, w. meevasana, m. a. kelly, n. a. melosh, and z. - x. shen ( stanford university ) ; t. m. willey, j. r. i. lee, and t. van buuren ( lawrence livermore national laboratory ) ; j. e. dahl and r. m. k. carlson", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6606172208262694, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:93b4ecea-e98a-462c-a6b9-fe9279c80cd0>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:41.306994"}
{"text": ". shen ( stanford university ) ; t. m. willey, j. r. i. lee, and t. van buuren ( lawrence livermore national laboratory ) ; j. e. dahl and r. m. k. carlson ( moleculardiamond technologies, chevron technology ventures ) ; p. r. schreiner, b. a. tkachenko, and n. a. fokina ( justus - liebig university, germany ) ; a. a. fokin ( justus - liebig university, germany, and kiev polytechnic institute, ukraine ) ; and z. hussain ( als ). research funding : u. s. department of energy, office of basic energy sciences ( bes ). operation of the als is supported by bes. publication about this research : w. l. yang, j. d. fabbri, t. m. willey, j. r. i. lee, j. e. dahl, r. m. k. carlson, p. r. schreiner, a. a. fokin, b. a. tkachenko, n. a. fokina, w. meevasana, n. mannella, k. tanaka, x. j. zhou, t. van buuren, m. a. kelly, z. hussain, n. a. melosh, and z. - x. shen, \" monochromatic electron photoemission from diamondoid monolayers, \" science 316, 1460 ( 2007 ).", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6722011188487698, "token_count": 322, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:93b4ecea-e98a-462c-a6b9-fe9279c80cd0>", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:41.308415"}
{"text": "posted : september 08, 2008 on wednesday, the world \u2019 s largest particle accelerator \u2013 the large hadron collider ( lhc ) \u2013 will be powered up to receive an injection of particle beams for the very first time as it begins the heroic quest to solve some of the biggest mysteries of our universe. astronomy now will be attending this momentous scientific milestone via a live link - up from westminster to the ceremony at cern ( the european organisation for nuclear research ) and we \u2019 ll have a full report later in the week. the lhc has a circumference of 27 kilometres, stretching from geneva airport in the lower left, to the open french countryside in the upper right. image : cern. buried one hundred metres below the french / swiss border and boasting a circumference of 27 kilometres, the lhc is the largest and most ambitious physics experiment in history. by accelerating particles to speeds of 99. 9999991 percent that of light, and watching what happens when they collide, it will probe questions surrounding the nature and existence of dark matter and antimatter, the weakness of gravity and even if extra dimensions exist. the dual beams of the lhc consist of bunches of particles a few tens of centimetres in length containing 100 billion protons. there will be 3000 going around the collider in each direction at any one time, with each beam containing the energy equivalent to the eurostar travelling at over 90 miles per hour. sub - atomic smash - ups will occur between the beams 600 million times a second, and detectors situated along the accelerator \u2019 s circumference will be on the look - out for the resulting debris of subatomic particles. on the lhc \u2019 s shopping list is the elusive higgs boson particle, which is widely believed to be the origin of the well - known property mass. the standard model of particle physics predicts two types of particles : mass - less particles like photons, and those with mass, like quarks ( protons and neutrons that make up atomic nuclei ) and electrons. the standard model also predicts the existence of the higgs boson and states that particles that possess mass do so because they interact with the resulting higgs field, as if they were travelling through treacle. this is important from a cosmological viewpoint, because the presence of dark matter can only be inferred from its gravitational effect, and this gravitational effect results from dark matter possessing mass. in essence, understanding the higgs boson", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6120729252543926, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:c17254c3-ce43-4dd0-9bb0-5a503afb60df>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:41.904321"}
{"text": "string theory is part of the equation. string theory states that all different particles are different vibrations in higher - dimensional string structures. one of the things that string theory predicts is the existence of micro black holes, something that could be identified in the lhc in terms of the particles that they decay into. such a result would provide the first real validation for string theory. but despite scare mongering by the popular media that the earth will ultimately be consumed in one of these \u2018 man - made \u2019 black holes, such an event is impossible since they would decay almost immediately, lacking the energy to grow, let alone be sustained. moreover, the sub - atomic collisions that the lhc will bare witness to are just a patch on what happens naturally in nature. in its 4. 6 billion year existence, the earth has been subject to a phenomenal number of cosmic ray collisions of far higher energies than could ever be achieved in the lhc, with no ill effects. the only real danger from the lhc is that the machine could damage itself should the magnets that keep the beams inside the collider fail. the result would be that the particle beams would destroy the magnets. to gradually test the full capabilities of the lhc, therefore, the beams won \u2019 t be switched on with full intensity at first, but will gradually be powered up over several months before getting down to serious business. astronomy now will be attending the lhc powering up ceremony via a live link - up to cern. we \u2019 ll have a full report later in the week. in the meantime, you can read more about the lhc in the july issue of astronomy now magazine. this special publication features the photography of british astro - imager nik szymanek and covers a range of photographic methods from basic to advanced. beautiful pictures of the night sky can be obtained with a simple camera and tripod before tackling more difficult projects, such as guided astrophotography through the telescope and ccd imaging. u. s. & worldwide store mars rover poster this new poster features some of the best pictures from nasa ' s amazing mars exploration rovers spirit and opportunity. u. s. & worldwide store home | news archive | magazine | solar system | sky chart | resources | stores | spaceflight now \u00a9 2010 pole star publications ltd.", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6365785271029545, "token_count": 468, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:c17254c3-ce43-4dd0-9bb0-5a503afb60df>", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:41.910570"}
{"text": "memristors were conceived by electrical engineer leon chua in his seminal 1971 paper \" memristor - - the missing circuit element \" ( ieee transactions on circuit theory ). his peer - reviewed claim startled electrical engineers by detailing how there was a \" missing link \" in circuit theory. by mathematical necessity, according to chua, a fourth passive electronics component - - after resistors, capacitors and inductors - - must exist. his argument was reminiscent of the inventor of the periodic table, russian chemist dmitri mendeleev, who claimed that by mathematical necessity there were missing elements in the periodic table that must exist. both were right. mendeleev ' s missing elements were eventually discovered, and in 2006 hewlett packard senior fellow stan williams likewise discovered chua ' s missing - memristor in a common semiconductor material. chua called his fourth passive circuit component a memristor, because it \" remembered \" the amount of current that had recently been flowing through it by changing its internal resistance - - making it a memory - resistor. hp ' s formulation was titanium - dioxide, but since them many other semiconductor manufacturers have come forward to disclose that they had also been working on memristive materials in their efforts to build a universal memory type - - called a resistive random access memory ( reram ). as a result, approximately 40 years after memristors were postulated by chua, these materials are finally achieving widespread commercialization as universal memory chips that are nonvolatile, denser than flash, and yet faster than dram. a remarkable spectrum of semiconductor houses are promising memristive microchips, some as early as 2013, including adesto technologies, elpida, fujitsu, global foundries, hewlett packard, hynix, ibm, macronix, nanya, nec, panasonic, rambus, sandisk, samsung, sharp, sony, st microelectronics, winbond, 4ds, and several research labs like imec collaborating with foundry partners like tsmc. what you may not be aware of, however, is that the next 40 years are likely to be even more significant for memristors, as the basis of a new era of cognitive computers based on the architecture of the human brain. spear - headed by the defense advanced research projects agency ( darpa ) program called systems of neuromorphic adaptive plastic scalable electronics ( synapse ) research labs are pioneering", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6251084255906258, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:27b3a6c7-d85e-4eba-80ed-312bc07a6877>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:42.648096"}
{"text": "by john mccaskill biomolecular computing, computations performed by biomolecules, is challenging traditional approaches to computation both theoretically and technologically. often placed within the wider context of natural or even unconventional computing, the study of natural and artificial molecular computations is adding to our understanding both of biology and computer science well beyond the framework of neuroscience. the papers in this special theme document only a part of an increasing involvement of europe in this far reaching undertaking. in this introduction, i wish to outline the current scope of the field and assemble some basic arguments that biomolecular computation is of central importance to both computer science and biology. readers will also find arguments for not dismissing dna computing as limited to exhaustive search and for a qualitatively distinctive advantage over all other types of computation including quantum computing. the idea that molecular systems can perform computations is not new and was indeed more natural in the pre - transistor age. most computer scientists know of von neumanns discussions of self - reproducing automata in the late 1940s, some of which were framed in molecular terms. here the basic issue was that of bootstrapping : can a machine construct a machine more complex than itself? important was the idea, appearing less natural in the current age of dichotomy between hardware and software, that the computations of a device can alter the device itself. this vision is natural at the scale of molecular reactions, although it may appear utopic to those running huge chip production facilities. alan turing also looked beyond purely symbolic processing to natural bootstrapping mechanisms in his work on self - structuring in molecular and biological systems. purely chemical computers have been proposed by ross and hjelmfelt extending this approach. in biology, the idea of molecular information processing took hold starting from the unraveling of the genetic code and translation machinery and extended to genetic regulation, cellular signaling, protein trafficking, morphogenesis and evolution - all of this independently of the development in the neurosciences. for example, because of the fundamental role of information processing in evolution, and the ability to address these issues on laboratory time scales at the molecular level, i founded the first multi - disciplinary department of molecular information processing in 1992. in 1994 came adlemans key experiment demonstrating that the tools of laboratory molecular biology could be used to program computations with dna in vitro. the huge information storage capacity of dna and the low energy dissipation of dna processing lead to an explosion of interest in massively parallel dna computing.", "subdomain_id": "subdomain_quantum_computing", "similarity_score": 0.6612396636052029, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:27e7ac4a-2f96-4c3d-9106-248acec66100>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:42.693821"}
{"text": "that the tools of laboratory molecular biology could be used to program computations with dna in vitro. the huge information storage capacity of dna and the low energy dissipation of dna processing lead to an explosion of interest in massively parallel dna computing. for serious proponents of the field however, there really never was a question of brute search with dna solving the problem of an exponential growth in the number of alternative solutions indefinitely. in a new field, one starts with the simplest algorithms and proceeds from there : as a number of contributions and patents have shown, dna computing is not limited to simple algorithms or even, as we argue here, to a fixed hardware configuration. after 1994, universal computation and complexity results for dna computing rapidly ensued ( recent examples of ongoing projects here are reported in this collection by rozenberg, and csuhaj - varju ). the laboratory procedures for manipulating populations of dna were formalized and new sets of primitive operations proposed : the connection with recombination and so called splicing systems was particularly interesting as it strengthened the view of evolution as a computational process. essentially, three classes of dna computing are now apparent : intramolecular, intermolecular and supramolecular. cutting across this classification, dna computing approaches can be distinguished as either homogeneous ( ie well stirred ) or spatially structured ( including multi - compartment or membrane systems, cellular dna computing and dataflow like architectures using microstructured flow systems ) and as either in vitro ( purely chemical ) or in vivo ( ie inside cellular life forms ). approaches differ in the level of programmability, automation, generality and parallelism ( eg simd vs mimd ) and whether the emphasis is on achieving new basic operations, new architectures, error tolerance, evolvability or scalability. the japanese project lead by hagiya focuses on intramolecular dna computing, constructing programmable state machines in single dna molecules which operate by means of intramolecular conformational transitions. intermolecular dna computing, of which adleman ' s experiment is an example, is still the dominant form, focusing on the hybridization between different dna molecules as a basic step of computations and this is common to the three projects reported here having an experimental component ( mccaskill, rozenberg and amos ). beyond europe, the group of wisconsin are prominent in exploiting a surface based approach to intermolecular dna computing using dna chips. finally, supramolecular dna computing, as pioneered", "subdomain_id": "subdomain_quantum_computing", "similarity_score": 0.6255880826097626, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:27e7ac4a-2f96-4c3d-9106-248acec66100>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:42.694763"}
{"text": "mccaskill, rozenberg and amos ). beyond europe, the group of wisconsin are prominent in exploiting a surface based approach to intermolecular dna computing using dna chips. finally, supramolecular dna computing, as pioneered by eric winfree, harnesses the process of self - assembly of rigid dna molecules with different sequences to perform computations. the connection with nanomachines and nanosystems is then clear and will become more pervasive in the near future. in my view, dna computation is exciting and should be more substantially funded in europe for the following reasons : the difference with quantum computing is dramatic. quantum computing involves high physical technology for the isolation of mixed quantum states necessary to implement ( if this is scalable ) efficient computations solving combinatorially complex problems such as factorization. dna computing operates in natural noisy environments, such as a glass of water. it involves an evolvable platform for computation in which the computer construction machinery itself is embedded. embedded computing is possible without electrical power in microscopic, error prone and real time environments, using mechanisms and technology compatible with our own make up. because dna computing is linked to molecular construction, the computations may eventually also be employed to build three dimensional self - organizing partially electronic or more remotely even quantum computers. moreover, dna computing opens computers to a wealth of applications in intelligent manufacturing systems, complex molecular diagnostics and molecular process control. the papers in this section primarily deal with biomolecular computing. the first contribution outlines the european initiative in coordinating molecular computing ( emcc ). three groups present their multidisciplinary projects involving joint theoretical and experimental work. two papers are devoted to extending the range of formal models of computation. the collection concludes with a small sampler from the more established approach to biologically inspired computation using neural network models. it is interesting that one of these contributions addresses the application of neural modelling to symbolic information processing. however, the extent to which informational biomolecules play a specific role in long term memory and the structuring of the brain, uniting neural and molecular computation, still awaits clarification. john mccaskill - gmd tel : + 49 2241 14 1526", "subdomain_id": "subdomain_quantum_computing", "similarity_score": 0.6853815450102819, "token_count": 449, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:27e7ac4a-2f96-4c3d-9106-248acec66100>", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:42.695634"}
{"text": "the sun is a natural nuclear fusion reactor, fusing hydrogen to helium. our current understanding of physics is quite clear about what happens, four hydrogen nuclei ( protons ), with and without the help of catalysts are transformed into helium, neutrinos and energy. the energy is released as gamma rays and as kinetic energy of the particles, including the neutrinos. neutrinos were originally theorized to make up the energy and angular momentum difference when a neutron decays into a proton and an electron. neutrinos were later demonstrated to exist, but accomplishing this was difficult because they have negligible mass, travel very close to the speed of light, and have no electric charge nor magnetic moment ( thus don ' t interact electromagnetically ). they also don ' t interact through the strong nuclear force. neutrinos do interact with other matter through the weak nuclear force ( that is how they are produced ). large heavy water ( water that has deuterium instead of hydrogen ) tanks with arrays of photocells are usually used to detect neutrinos. the detectors used to capture solar neutrinos are huge, usually deep underground to avoid noise from cosmic rays. as the technology progressed, and bigger detectors were built, it became clearer that we just weren ' t getting as many neutrinos from the sun as our models of solar combustion predicted. in various experiments, the number of detected neutrinos was between 1 / 3 and 1 / 2 of the predicted number. therefore either our models of the sun were wrong or our models of neutrino behavior were wrong. this is known as the solar neutrino problem. the solutions based on the models of the sun being wrong were based on the premise that the temperature and pressure in the interior of the sun was not what we thought it was. for example, since neutrinos measure the amount of current nuclear fusion, it was suggested that the nuclear processes in the core of the sun might have temporarily shut down, and since it takes thousands of years for heat energy to move from the core to the surface of the sun, this would not immediately be apparent. solutions based on incorrect understanding of solar physics were rendered untenable by helioseismology which observes how waves propagate through the sun. based on these observations it became possible to measure the interior temperatures of the sun and these agreed with the standard solar models. currently, the solar neutrino problem is believed to result from an inadequate understanding of the", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6150005136940749, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:d1f9168b-eab1-4e45-b2ab-fb002ef59652>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:42.730597"}
{"text": "silicon carbide, chemical compound, sic, that forms extremely hard, dark, iridescent crystals that are insoluble in water and other common solvents. widely used as an abrasive, it is marketed under such familiar trade names as carborundum and crystolon. it is heat resistant, decomposing when heated to about 2, 700\u00b0c ; it is used in refractory materials, e. g., rods, tubes, firebrick, and in special parts for nuclear reactors. very pure silicon carbide is white or colorless ; crystals of it are used in semiconductors for high - temperature applications. silicon carbide fibers, added as reinforcement to plastics or light metals, impart increased strength and stiffness. silicon carbide is prepared commercially by fusing sand and coke in an electric furnace at temperatures above 2, 200\u00b0c ; a flux, e. g., sodium chloride, may be added to eliminate impurities. silicon carbide was discovered ( 1891 ) by e. g. acheson ; early studies of it were made by henri moissan. the columbia electronic encyclopedia, 6th ed. copyright \u00a9 2012, columbia university press. all rights reserved. more on silicon carbide from infoplease : see more encyclopedia articles on : compounds and elements", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6653923915135997, "token_count": 271, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:81fb236c-32ae-4f71-9e06-73de5298b345>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:43.034246"}
{"text": "describing motion with words visit the physics classroom ' s flickr galleries and take a visual overview of 1d kinematics. distance and displacement distance and displacement are two quantities that may seem to mean the same thing yet have distinctly different definitions and meanings. - distance is a scalar quantity that refers to \" how much ground an object has covered \" during its motion. - displacement is a vector quantity that refers to \" how far out of place an object is \" ; it is the object ' s overall change in position. to test your understanding of this distinction, consider the motion depicted in the diagram below. a physics teacher walks 4 meters east, 2 meters south, 4 meters west, and finally 2 meters north. even though the physics teacher has walked a total distance of 12 meters, her displacement is 0 meters. during the course of her motion, she has \" covered 12 meters of ground \" ( distance = 12 m ). yet when she is finished walking, she is not \" out of place \" - i. e., there is no displacement for her motion ( displacement = 0 m ). displacement, being a vector quantity, must give attention to direction. the 4 meters east cancels the 4 meters west ; and the 2 meters south cancels the 2 meters north. vector quantities such as displacement are direction aware. scalar quantities such as distance are ignorant of direction. in determining the overall distance traveled by the physics teachers, the various directions of motion can be ignored. now consider another example. the diagram below shows the position of a cross - country skier at various times. at each of the indicated times, the skier turns around and reverses the direction of travel. in other words, the skier moves from a to b to c to d. use the diagram to determine the resulting displacement and the distance traveled by the skier during these three minutes. then click the button to see the answer. as a final example, consider a football coach pacing back and forth along the sidelines. the diagram below shows several of coach ' s positions at various times. at each marked position, the coach makes a \" u - turn \" and moves in the opposite direction. in other words, the coach moves from position a to b to c to d. what is the coach ' s resulting displacement and distance of travel? click the button to see the answer. to understand the distinction between distance and displacement, you must know the definitions. you must also know that a vector quantity such as displacement is direction - aware and a scalar quantity such as distance is", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6259956928092995, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:499e5940-0bb4-41c6-875d-f331ac36f52c>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:44.144004"}
{"text": "mar. 22, 2009 the territory where the higgs boson may be found continues to shrink. the latest analysis of data from the cdf and dzero collider experiments at the u. s. department of energy ' s fermilab now excludes a significant fraction of the allowed higgs mass range established by earlier measurements. those experiments predict that the higgs particle should have a mass between 114 and 185 gev / c2. now the cdf and dzero results carve out a section in the middle of this range and establish that it cannot have a mass in between 160 and 170 gev / c2. \u201c the outstanding performance of the tevatron and cdf and dzero together have produced this important result, \u201d said dennis kovar, associate director of the office of science for high energy physics at the u. s. department of energy. \u201c we ' re looking forward to further tevatron constraints on the higgs mass. \" the higgs particle is a keystone in the theoretical framework known as the standard model of particles and their interactions. according to the standard model, the higgs boson explains why some elementary particles have mass and others do not. so far, the higgs particle has eluded direct detection. searches at the large electron positron collider at the european laboratory cern established that the higgs boson must weigh more than 114 gev / c2. calculations of quantum effects involving the higgs boson require its mass to be less than 185 gev / c2. \" a cornerstone of nsf ' s support of particle physics is the search for the origin of mass, and this result takes us one step closer, \" said physics division director joe dehmer, of the national science foundation. the observation of the higgs particle is also one of the goals of the large hadron collider experiments at cern, which plans to record its first collision data before the end of this year. the success of probing the higgs territory at the tevatron has been possible thanks to the excellent performance of the accelerator and the continuing improvements that the experimenters incorporate into the analysis of the collider data. \u201c fermilab \u2019 s tevatron collider typically produces about ten million collisions per second, \u201d said dzero co - spokesperson darien wood, of northeastern university. \u201c the standard model predicts how many times a year we should expect to see the higgs boson in our detector, and how often we should see particle signals", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6169471859223794, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:bbdf5547-de56-4b9a-abca-f4b5f6a5e6e8>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:44.298989"}
{"text": "appear at first glance. background information : as in any scientific endeavor, the first step is to gather information about the subject. before each experiment, the students need to have information relevant to the lab topic. the pre lab discussion provides some background information. the teacher may wish to provide additional information or the students may look up additional relevant information. language skill building : clear precise communication is a key to good science. scientists must be able to communicate their findings in unambiguous language. this often means that the common words are defined as used in this report so that the reader knows exactly what the scientist means when he reads the term. the teacher may wish to discuss the term significant as it is found in many scientific studies. it is usually defined using a statistical test in a scientific study but it shows up in advertising without any definition. scientific writing is designed to have only one interpretation while poetry will invoke many different meanings, depending on the reader ' s personal experiences. students often tell the teacher that they \" know \" something but can ' t put it into words. developing language skills is a large part of science, and students must be taught how to better use their language to communicate their ideas. the first step is to have students clearly define the terms that they are using. in many experiments, the students need to develop operational definitions for terms that are needed to describe critical aspects of the experiment. scientific thinking : the students must develop confidence in their own thinking ability. great science does not depend on expensive complex equipment but on the clear thinking of the experimenter. the experiments in this manual serve only as entertainment if students do not do the follow - up thinking scientifically. teachers should insist that students think before they write and that they express their thoughts clearly. printing the labs : the labs are available both as web pages and as adobe portable document format ( pdf ) files, a more printer - friendly format. you must have adobe acrobat reader installed on your computer to use this feature. you can download the free adobe acrobat reader software here. 1. introduction to alchemy like the alchemists, our objective is to make gold from base metals ; we use drain cleaner, pennies and galvanized nails. 2. water, water everywhere different to determine the differences between samples of water obtained by the class. 3. a slippery slimy substance to make and study an unusual polymer, using borax, guar gum and food coloring. 4. what is the pop in popcorn? to determine what causes some corn kernel", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6211031093469961, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:64a9b784-81f4-44ac-9eda-9267e0cef2a1>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:44.341773"}
{"text": "of water obtained by the class. 3. a slippery slimy substance to make and study an unusual polymer, using borax, guar gum and food coloring. 4. what is the pop in popcorn? to determine what causes some corn kernels to pop when heated. 5. hard rock candy to study how crystals form while making sugar crystal rock candy. 6. heat - - hide & seek to learn the difference between heat and temperature, using moth crystals. 7. hot & cold reactions to explore the energy of chemical reactions, using baking soda, lye, vinegar, zinc, hcl. 8. are we saturated yet? to make and observe the properties of unsaturated, saturated, and supersaturated solutions, using photography fixer. 9. cleaning up your act to make a useable soap. 10. the solution to solubility is the solvent to determine the solubility of three general types of common solvents : water, alcohol and xylene. pdf lab for the solution to solubility is 11. out spot, darn spot to explore the science of laundry. this laboratory exercise is different from the others in that students will not be given a set procedure to follow to remove a spot. instead they will need to use the information provided to develop a procedure to remove a spot. 12. can the mettle of metal be improved? to determine the effects of annealing, quenching, and tempering on metals, using bobbi pins, hair clip, single strand steel wire. 13. creepy metals to determine the tensile strength and creep in three common metals. 14. blowing up balloons, chemically to determine what observable factors are changed in a chemical reaction and what factors remain constant. to determine the amount of acid neutralized by several brands of antacid tablet. 16. chemistry clicks your bic to experimentally determine the molecular mass of butane, using a lighter. 17. electric gel cell to make functional electrical cells and determine the relative strength of each type of cell, using jell - o. 18. viscosity is a virtue to compare the viscosity of motor oil at different temperatures ; compare the viscosities of several grades of motor oil ; and to compare the viscosity of new and used motor oil. \u00a9 1999 robert farber - all rights reserved. teachers are encouraged to copy and modify these labs for use in their teaching. please send any questions or comments to robert farber ( firstname. lastname @ example", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6062735172315054, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:64a9b784-81f4-44ac-9eda-9267e0cef2a1>", "chunk_index": 2, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:44.343712"}
{"text": "yenka science with electronics is a highly interactive virtual lab, which lets you model physics and chemistry experiments safely and easily. simulate experiments however you wish : design circuits and optical systems, model reactions using over 100 different chemicals, investigate wave propogation or accelerate masses. poweful graph tools let you follow your experiments ' progress. it can be used as a flexible demonstration tool - for example, on a whiteboard. alternatively, students can use yenka themselves, to investigate concepts in yenka ' s safe, accurate world. and teachers and students can all use the full version of yenka science at home, free of charge. yenka science with electronics covers these areas : - electronic design - design circuits using over 100 types of digital and analog component. - light and sound - experiment with sound, water and light waves, and ray diagrams. - force and motion - investigate projectiles, oscillations, gravity and motion. - electricity and magnetism - simulate power generation and transmission, and analogue electrical circuits. - inorganic and physical chemistry - model experiments using a wide range of chemicals, equipment and glassware, graphing data as your simulations run. - electrochemistry - investigate electrolysis, electroplating and cells, choosing from a range of metal or carbon electrodes, and 28 different electrolytes. if you don ' t teach electronics in your science lessons, you could save money by buying yenka science. and you can also buy yenka physics or yenka chemistry individually, which together make up yenka science.", "subdomain_id": "subdomain_quantum_materials", "similarity_score": 0.6078548688352832, "token_count": 310, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:b22b8443-72fd-4366-9740-252b65ec5c3c>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:44.908939"}
{"text": "an external force. kinetic energy : the energy of an object based on its movement. parabola : the natural path of an object in motion through the air. a parabola is completely symmetric about the axis. potential energy : the energy of an object based on its location. this is the stored energy. roller coaster : a gravity - based train where all of the movement is propelled by gravity. the only input energy is to reach the starting point. post - visit activities provide your students with an opportunity to review workshop - presented concepts and introduce related subjects. below you will find a classroom extension activity and a list of suggested resources for further exploration. we hope that you enjoyed our outreach hands - on workshop and we look forward to visiting your students again! hands - on activity : flying high - 2 golf balls - 2 tennis balls - 2 basketballs - outdoor space this is a great demonstration for illustrating the principle of conservation of momentum. take your class outside and ask if they know what momentum is. explain that momentum is equal to the mass times the velocity of an object. the law of conservation says that if two ( or more ) objects collide, the total momentum before the collision must be equal to the total momentum after, not taking into consideration principles like gravity and friction. for the demonstration, first stack the two basketballs on top of each other and drop them as one. observe what happens. now, hold the tennis ball on top of the basketball and repeat. be careful that nothing is in line with the tennis ball. here, you \u2019 ll notice that the tennis ball travels a good distance higher than the drop point. try different combinations to see if you can maximize the height. to understand what \u2019 s going on, explain that the total mass of your two objects can be thought of as one larger object falling at a specific velocity. when they hit the ground, the top one bounces off the bottom one. the small one soars because you \u2019 ve suddenly removed most of the mass. as a result, the velocity must increase in order to compensate. example : imagine you have a 10 pound ball and a 1 pound ball stacked and falling at 10 meters per second hit the ground. the 10 pound ball isn \u2019 t elastic enough to bounce at all. what velocity will the 1 pound ball now have? your total initial mass = 11 pounds. so, set up your equation like this : 11lb \u00d7 10m / s = 1lb \u00d7 vm / s ( where v = the unknown velocity ). if you solve for v, you", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.6664518571629143, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:ce52bfd6-e52a-4026-b891-65e7006eacb2>", "chunk_index": 1, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:44.986229"}
{"text": "classical general relativity in more than four spacetime dimensions has been the subject of increasing attention in recent years. among the reasons why it should be interesting to study this extension of einstein \u2019 s theory, and in particular its black hole solutions, we may mention that - string theory contains gravity and requires more than four dimensions. in fact, the first successful statistical counting of black hole entropy in string theory was performed for a fivedimensional black hole. this example provides the best laboratory for the microscopic string theory of black holes. - the ads / cft correspondence relates the properties of a d - dimensional black hole with those of a quantum field theory in d \u2212 1 dimensions. - the production of higher - dimensional black holes in future colliders becomes a conceivable possibility in scenarios involving large extra dimensions and tev - scale gravity. - as mathematical objects, black hole spacetimes are among the most important lorentzian ricci - flat manifolds in any dimension. and the translation : traditional general of relativity in more than four masses of that the time of the space was the subject of the increase attention these the slipped years. to the relations of transformation, so that he had that to being interesting, to this extension of the theory of einstein to study and in the detail of the relative solutions to perforate black color, that we can we mentioned this - the theory of the series of the characters will count the force of the gravity and it more has the necessity of the one of mass four. they executed the first guessed right statistical client of the entropy of the black color that really perforates in the theory of the series of the characters the end to perforate the black color of the fivedimensional. this better example releases the laboratory available for the microscopic theory of the series of the characters of the black color of the perforations. - the correspondence of ads / cft connects the characteristics of a d dimensional schwarzen that the sacadores with those with a theory of the zone of the section of the time in the d without mass 1. - the production of the perforations that the high - dimensional - black color in her the future transforms of colliders inside the great possibilities imaginable ones into the writing of the suggestion adds of the film and in the fairs of tev the force of the gravity. - as matemati of the messages those we belong spacetimes of the black color that the sacadores to the tubes the greatest piece of the important stocherkaehne i", "subdomain_id": "subdomain_quantum_field_theory", "similarity_score": 0.651574800098293, "token_count": 512, "source_dataset": "HuggingFaceFW/fineweb-edu", "source_id": "<urn:uuid:152ce7f1-8d02-4546-a969-0b59a15efdeb>", "chunk_index": 0, "filtering_threshold": 0.6, "created_at": "2025-12-23T01:51:45.095793"}