apr. 24, 1998 columbus, ohio - - researchers at ohio state university have developed a new model of atomic forces that may solve a long - standing problem in particle physics. the work may aid the understanding of the structure of protons and other particles that contain quarks because it begins to reconcile physicist richard feynman ’ s 1970s model of the proton with modern views of the quark structure of sub - atomic particles. “ we ’ re hoping our work will make it easier for people who work with the quark model to calculate a lot of experimental information, ” said kenneth wilson, professor of physics at ohio state and 1982 nobel laureate in physics. “ right now, the equations that describe proton structure are very complicated. ” wilson helps to lead the research group for this project, which includes robert perry, also professor of physics, and stan glazek, a frequent visitor to ohio state and associate professor of physics from warsaw university. the researchers discussed their model april 18 at the 1998 american physical society meeting in columbus. physicists have a hard time mathematically describing the structure of the proton, because the particle is supposed to be surrounded by a cloud of virtual particles that blink in and out of existence all the time, severely complicating the equations. in the early 1970s, feynman, a former physicist at caltech, devised a way for physicists to separate the proton ’ s constituents from these virtual particles - - mathematically, at least. he suggested that a proton moving at the speed of light could outrun the slower virtual particles so physicists could observe its constituents on their own. he envisaged the proton ’ s constituents as being just three fundamental particles called quarks. this greatly simplified the mathematics. physicists now hypothesize that protons are made up of quarks and other fundamental particles called gluons, and that the massless and neutrally charged gluons bind quarks together. the current theory is much more complicated than feynman ’ s : the connection between quarks and gluons is supposed to be so strong that smashing a proton in a particle accelerator would release not just three quarks as feynman predicted, but a shower of quarks, anti - quarks, and gluons. still, feynman ’ s ideas provided for simple equations that matched experimental results concerning the energy states of protons. “ the question was, once we had this very complex quark theory, why did feynman ’ s


gluons. still, feynman ’ s ideas provided for simple equations that matched experimental results concerning the energy states of protons. “ the question was, once we had this very complex quark theory, why did feynman ’ s simple model still work so well? no one has ever been able to figure out why. in fact, the problem became so difficult that people just gave up, ” said wilson. wilson and his colleagues have formulated a new picture of quark - gluon interaction. they think that gluons may bind strongly to each other but not so strongly to quarks. that would prevent quarks from escaping easily during experiments, but also allow for feynman ’ s simpler mathematical model. “ the coupling of gluons to each other is quite strong, and that coupling confines quarks inside the proton, ” explained wilson. with this theory, when the bonds between gluons are broken, the reaction emits mostly other gluons. extra particles such as anti - quarks and virtual particles don ’ t emerge because no strong bonds exist between quarks. even gluons should be rarely emitted because, in the new theory, they are expected to have high masses, making them hard to produce. this work, which was sponsored by a grant from the national science foundation, is in the preliminary stages, and the ohio state researchers will continue to develop it mathematically. but even before then, they hope other physicists will explore the new theory as well. other social bookmarking and sharing tools : the above story is reprinted from materials provided by ohio state university. note : materials may be edited for content and length. for further information, please contact the source cited above. note : if no author is given, the source is cited instead.


build a segment of the dna consisting of adenine, thymine, cytosine and guanine. color - coded pieces designate certain molecules making up the four nucleotides present in dna. kit includes : 12 packets of model parts, each with enough material to construct a segment of 6 - paired bases. instructions and reproducible student worksheets are also included. chromosomes are structures in the nucleus of a cell and are composed of long strands of deoxyribonucleic acid ( dna ). in 1953, two scientists, james d. watson and f. h. c. crick, proposed a model of the structure of the complex dna. they described the molecule as a double helix or spiral, composed of nucleotides. each nucleotide is composed of a phosphate unit joined to deoxyribose, a five - carbon sugar and a nitrogen - containing base. the dna molecule is a double strand of possibly thousands of nucleotides bonded by synthesis in a cell. 12 - 3 prong " deoxyrobose " centers ( black ) 12 - 2 prong " phosphate " centers ( red ) 3 - " adenine " straws ( red ) 3 - " guanine " straws ( gray ) 3 - " thymine " straws ( blue ) 1 - 4 prong center 3 - " cytosine " straws ( short green ) 6 - hydrogen bondcenters ( white ) 24 - connectors ( yellow ) 1 - long strand ( gray ) 3 long posts ( green ) 3 - " uracil " ( white ) manufacturer : american educational products american educational products are focused on the early childhood and physical education arena. teachers, parents and caregivers will find creatively designed products to stimulate children ' s motor skills, as well as their intellectual development. many of the products are appropriate for children with special needs / disabilities and ideal for school, home and daycare settings. sensoryedge offers free shipping to the lower 48 contiguous states in the usa. shipping times are listed on each item page. if you order multiple items, they may arrive separately. most products are shipped factory direct and thus might be coming from different locations. the majority of the products we sell are shipped either ups or fed ex ground depending on the vendors preferred delivery service. large orders and heavy items may be shipped by a 3rd party trucking service. items shipped via 3rd party trucking do not include lift - gate service or inside delivery. sensoryedge wants you to be satisfied


learn something new every day more info... by email thermoelasticity is the change in the size and shape of a solid object as the temperature of that object fluctuates. materials that are more elastic will expand and contract more than those materials that are more inelastic. scientists use their understanding of thermoelasticity to design materials and objects that can withstand fluctuations in temperature without breaking. scientists have understood the equations that describe thermoelasticity for over 100 years but have only recently begun stress testing materials in order to determine how thermoelastic they are. by subjecting materials to rising and falling temperatures, engineers are able to predict how much these materials will expand or contract at different temperatures. this knowledge is important when building machines or weight bearing structures with pieces that need to fit closely together. understanding the principles of thermoelasticity helps engineers design things that maintain their structural integrity for a range of temperatures. the principles of thermoelasticity have affected the way engineers design a number of different objects. knowing that concrete expands when it is heated, for instance, is the reason that sidewalks are designed with small spaces between the slabs. without these spaces, the concrete would have no room to expand, causing a great deal of stress on the material, and leading to cracks, breaks or holes. likewise, bridges are designed with expansion joints to allow for the components to expand as they are heated. all materials that are elastic expand when heated and contract when cooled. the expansion that is described by thermoelasticity formulas is caused by an increase in the movement of the atoms in the material. these atoms remain linked to each other as a solid heats but the molecular bonds grow in size, allowing the atoms to move away from each other and causing the material to grow. conversely, when a material is cooled, the atoms move less and the bonds pull them closer to each other. the principles of thermoelasticity dictate that the expansion caused by an increase in temperature will cause an object to expand in all directions. slabs of concrete expand out towards one another, up away from the ground, and down towards the ground when they are heated. cups or other vessels will expand in all directions as well in such a way that the total volume they can contain increases along with the size of the vessel. specific formulas are used in the study of thermoelasticity to describe how objects change in shape with changes in temperature.


archive for darpa you are browsing the archives of darpa. you are browsing the archives of darpa. there a lot of great stuff going on : on the absolute temperature scale that is used by physicists, the kelvin scale, one cannot go below zero — at least not in the sense of getting colder than zero kelvin. physicists of the ludwig - maximilians university munich and the max planck institute of quantum optics, garching, germany, have now created an atomic gas in the lab that has nonetheless negative kelvin values. these negative absolute temperatures lead to several striking consequences : although the atoms in the gas attract each other and give rise to a negative pressure, the gas does not collapse, a behavior that is also postulated for dark energy in cosmology. also supposedly impossible heat engines can be realized with the help of negative absolute temperatures, such as an engine with a thermodynamic efficiency above 100 percent. in order to bring water to the boil, energy needs to be added to the water. during heating up, the water molecules increase their kinetic energy over time and move faster on average. yet, the individual molecules possess different kinetic energies, from very slow to very fast. in thermal equilibrium, low - energy states are more likely than high - energy states, i. e., only a few particles move really fast. in physics, this distribution is called boltzmann distribution. physicists led by ulrich schneider and immanuel bloch have now created a gas in which this distribution is inverted : many particles possess large energies and only a few have small energies. this inversion of the energy distribution means that the particles have assumed a negative absolute temperature. “ the inverted boltzmann distribution is the hallmark of negative absolute temperature ; and this is what we have achieved, ” says schneider. “ yet the gas is not colder than zero kelvin, but hotter. it is even hotter than at any positive temperature. the temperature scale simply does not end at infinity, but jumps to negative values instead. ” ( gizmag ) a streetscape that includes natural landscaping, bicycle lanes, wind powered lighting, storm water diversion for irrigation, drought - resistant native plants and innovative concrete has earned cermak road in chicago the title of “ greenest street in america ” according to the chicago department of transport ( cdot ). the location runs through an industrial zone which links the state and us highways. the project will record quantifiable results through a set of equally aggressive sustainability goals charting eight performance areas such as storm


, are highly encouraged to submit proposals to the loco program. performance of materials, parts, and assemblies ( e. g., tribological, optical, electronic and / or thermal ) are dictated by interactions between surfaces and the environment, affecting the cost, capability and readiness of dod systems. a number of known thin - film materials exist that could mitigate these performance limitations when deposited as coatings on substrates of interest to dod ( e. g., crystalline diamond thin film ). however, the high bulk deposition temperatures used in state - of - the - art chemical vapor deposition processes to meet the energetic and chemical requirements for processes, such as reactant flux, surface mobility and reaction energy, are often higher than the maximum temperature that many dod - relevant substrates can withstand ( i. e., due to property changes such as melting, grain growth, etc. ). these synthetic constraints not only affect our ability to manipulate surfaces of existing dod systems, but also restrict development of new technologies on emerging substrates ( e. g., diamond on polymers for flexible electronics and on living cells for biotic / abiotic interfaces ). to this end, darpa is seeking innovative multidisciplinary research proposals that independently develop novel chemical and physical processes to meet the energetic / chemical requirements of thin film deposition without reliance on broadband temperature input used in state - of - the - art chemical vapor deposition. darpa anticipates early stage efforts that address one piece of the deposition puzzle ( i. e., process component ) such as reactant flux, surface mobility, reaction energy, nucleation, byproduct removal, etc., that will be integrated later in the program to create a full deposition process. the specific objective of the loco program is to develop a deposition process applicable to a large variety of thin - film materials. however, to guide proposal development for process components, initial areas of interest for loco thin films include synthesis of covalent thin films with long - range order that require high deposition temperatures ( > 700°c ) for insertion points in tribological, thermal management, optical and electronic applications ( e. g., crystalline diamond thin films ). the loco program is broken into two independent, but intellectually connected thrusts : thrust 1, the main effort of the loco program, is arranged in a progression of discrete tasks that rapidly move from fundamental research to deposition of a thin film on a dod part for testing and evaluation. performers will address one or more of the process components for thin film growth ( e.


” the darpa story says the next step for the program is to improve models for “ characterizing the thermal uncertainties and heat - stress allowances for the vehicle ’ s outer shell. ” however, accurately characterizing materials at high temperatures is not easy. last week we summarized a review article on methods for measuring thermophysical properties above 1, 500°c, a laboratory capability that is being driven largely by aerospace and nuclear applications. even the business of accurately measuring temperature for those tests is as much art as science. these materials are not easy to work with, either. the materials under investigation are refractory nonoxide composites, like c / sic, sometimes with refractory borides mixed in. the cover story of the january / february issue of the bulletin gives an overview of materials, processes and properties of uhtc composite materials under investigation for hypersonic vehicles in the uk. in the us, a multi - university and industry partnership is working on the problem under the umbrella organization, national hypersonic science center for materials and structures. a recent paper ( abstract only ) by a research team at the university of california, santa barbara — one of the partner universities — describes a method for measuring strain at high - temperatures. the authors, mark novak and frank zok, note that development of materials for extreme environments requires the ability to reproduce conditions in the laboratory, which is not trivial. in their paper, they use digital image correlation to measure displacement and strain. dic is an optical, non - contact method that can be used at high temperatures. displacements are measured by correlating speckle pattern images of specimen surfaces in the deformed state to the undeformed state. strains are determined by differentiating between displacement fields. the technique eliminates strain gauges, and they report, is accurate with excellent spatial resolution. it has the further advantage of being useful for specimens subject to thermal gradients or mechanical loads because it can recognize out - of - plane displacements. the trick is in the imaging, which requires an illumination source that can be distinguished from the glow of thermal radiation. also, heat haze is a problem when the measurements are made in ambient air. finally, the speckle pattern itself has to be thermally stable and have enough contrast in the test temperature interval. the paper describes a technique novak and zok devised using a co2 laser as the illumination source, which they demonstrated on a c / sic composite and a nickel base superalloy ( inconel 625 ). al


| the act or manner of managing ; handling, direction, or control | | a high point of land or rock projecting into the sea or other water beyond the line of coast ; a headland. | | — n, pl - ses | | 1. | | compare theory a suggested explanation for a group of facts or phenomena, either accepted as a basis for further verification ( working hypothesis ) or accepted as likely to be true | | 2. | | an assumption used in an argument without its being endorsed ; a supposition | | 3. | | an unproved theory ; a conjecture | | [ c16 : from greek, from hupotithenai to propose, suppose, literally : put under ; see | hypothesis hy · poth · e · sis ( hi - poth ' i - sis ) n. pl. hy · poth · e · ses ( - sez ' ) a tentative explanation that accounts for a set of facts and can be tested by further investigation. | hypothesis ( hi - poth ' i - sis ) pronunciation key plural hypotheses ( hi - poth ' i - sez ' ) a statement that explains or makes generalizations about a set of facts or principles, usually forming a basis for possible experiments to confirm its viability. our living language : the words hypothesis, law, and theory refer to different kinds of statements, or sets of statements, that scientists make about natural phenomena. a hypothesis is a proposition that attempts to explain a set of facts in a unified way. it generally forms the basis of experiments designed to establish its plausibility. simplicity, elegance, and consistency with previously established hypotheses or laws are also major factors in determining the acceptance of a hypothesis. though a hypothesis can never be proven true ( in fact, hypotheses generally leave some facts unexplained ), it can sometimes be verified beyond reasonable doubt in the context of a particular theoretical approach. a scientific law is a hypothesis that is assumed to be universally true. a law has good predictive power, allowing a scientist ( or engineer ) to model a physical system and predict what will happen under various conditions. new hypotheses inconsistent with well - established laws are generally rejected, barring major changes to the approach. an example is the law of conservation of energy, which was firmly established but had to be qualified with the revolutionary advent of quantum mechanics and the uncertainty principle. a theory is a set of statements, including laws and hyp


major changes to the approach. an example is the law of conservation of energy, which was firmly established but had to be qualified with the revolutionary advent of quantum mechanics and the uncertainty principle. a theory is a set of statements, including laws and hypotheses, that explains a group of observations or phenomena in terms of those laws and hypotheses. a theory thus accounts for a wider variety of events than a law does. broad acceptance of a theory comes when it has been tested repeatedly on new data and been used to make accurate predictions. although a theory generally contains hypotheses that are still open to revision, sometimes it is hard to know where the hypothesis ends and the law or theory begins. albert einstein ' s theory of relativity, for example, consists of statements that were originally considered to be hypotheses ( and daring at that ). but all the hypotheses of relativity have now achieved the authority of scientific laws, and einstein ' s theory has supplanted newton ' s laws of motion. in some cases, such as the germ theory of infectious disease, a theory becomes so completely accepted, it stops being referred to as a theory. plur. hypotheses ( heye - poth - uh - seez ) in science, a statement of a possible explanation for some natural phenomenon. a hypothesis is tested by drawing conclusions from it ; if observation and experimentation show a conclusion to be false, the hypothesis must be false. ( see scientific method and theory. )


the alchemy of paint looks at medieval artists ' materials and methods in a manner as close as possible to the way painters themselves saw them in the middle ages. to do that, it had to adopt the worldview of 13th or 14th century european artisans. it assumes that they were reasonably well - informed about science, philosophy and religion, but were not too worried about the finer details. as such, the book is a primer, introducing general principles that pervade the traditional worldview. i therefore hope it will prove useful to readers whose interests may be wider than just alchemy or paint. the book follows in the footsteps of c. s. lewis ' the discarded image. the book draws upon my experience as a scientist studying the material nature of works of art. my starting point was that great paintings are physical testament to medieval skills in chemistry, optics and perception, just as the great gothic cathedrals are physical testament to medieval engineering skills. approaching artworks as the tangible traces of embodied skills, artists ' processes and their products can help throw light on the material culture of a place and a time. the more i looked into the material nature of european works of art from the middle ages, the more i realised the truly international character of the period. traditional european works of art can only be understood if their connections with non - european cultures are acknowledged. some european ' art - forms ' may be specific to europe, but what ' in - formed ' them recognises no spatial boundaries. the word ' traditional ' ( as opposed to ' medieval ' ) further implies that their worldview was not time - limited - it may have faded in europe over the last 500 years, but pockets of it live on, as superstitions in the modern world and as coherent beliefs elsewhere. the book starts from the recognition that our current attitudes towards colour seriously devalue the sensation. it looks towards the middle ages as the nearest culture to our own that acknowledged the importance of colour. by examining the materials of colour ( pigments, dyes and metals ) the book explores a world in which colour is meaningful. the book starts with a survey of the international trade in colours and the way colours touched members of society - as things that paid taxes and provoked wars, to things that were taken as drugs and were the focus of meditation. it then investigates recipes that artists wrote describing how to purify natural colours like lapis lazuli, and synthesise artificial colours like vermilion. those recipes conjure - up a world of three continents, made


nuclear reaction defies expectations dec 10, 2010 11 comments a novel kind of fission reaction observed at the cern particle physics laboratory in geneva has exposed serious weaknesses in our current understanding of the nucleus. the fission of mercury - 180 was expected to be a " symmetric " reaction that would result in two equal fragments but instead produced two nuclei with quite different masses, an " asymmetric " reaction that poses a significant challenge to theorists. nuclear fission involves the splitting of a heavy nucleus into two lighter nuclei. according to the liquid - drop model, which describes the nucleus in terms of its macroscopic quantities of surface tension and electrostatic repulsion, fission should be symmetric. some fission reactions are, however, asymmetric, including many of those of uranium and its neighbouring actinide elements. these instead can be understood by also using the shell model, in which unequal fragments can be preferentially created if one or both of these fragments contains a " magic " number of protons and / or neutrons. for example, one of the fragments produced in many of the fission reactions involving actinides is tin - 132, which is a " doubly - magic " nucleus, containing 50 protons and 82 neutrons. the latest work, carried out by a collaboration of physicists using cern ' s isolde radioactive beam facility, investigated the interplay between the macroscopic and microscopic components of nuclear fission. it used what is known as beta - delayed fission, a two - step process in which a parent nucleus beta decays and then the daughter nucleus undergoes fission if it is created in a highly excited state. this kind of reaction allows scientists to study fission reactions in relatively exotic nuclei and was first studied at the flerov laboratory in dubna, russia, about 20 years ago, although the dubna measurements did not reveal the masses of the fragments produced. firing protons at uranium the experiment at isolde involved firing a proton beam at a uranium target and then using laser beams and a magnetic field to filter out ions of thallium - 180 from among the wide variety of nuclei produced in the proton collisions. these ions then became implanted in a carbon foil, where they underwent beta decay and some of the resulting atoms of mercury - 180 then fissioned. silicon detectors placed in front of and behind the foil allowed the energies of the fission products to be measured. the researchers were expecting the fission reaction to be symmetric, with the mercury - 180 splitting into two nuclei of zirconium - 90, a result thought to be particularly


of and behind the foil allowed the energies of the fission products to be measured. the researchers were expecting the fission reaction to be symmetric, with the mercury - 180 splitting into two nuclei of zirconium - 90, a result thought to be particularly favoured because these nuclei would contain a magic number of neutrons ( 50 ) and a " semi - magic " number of protons ( 40 ). what they found, however, was quite different. the energy of the fission products recorded in the silicon detectors did not peak at one particular value, which would be the case if only one kind of nuclei was being produced in the reactions, but instead showed two distinct peaks centred around the nuclei ruthenium - 100 and krypton - 80. collaboration spokesperson andrei andreyev of the university of leuven, belgium, ( and currently at the university of west of scotland ) says that this asymmetric fission was unexpected because the observed fragments do not contain any magic or semi - magic shells. his colleague, theorist peter moller of the los alamos national laboratory in the us had in fact devised a model of the nucleus that predicted that mercury - 180 would undergo asymmetric fission. but he wasn ' t able to explain why that is, having plotted a three - dimensional potential energy surface for the fission of mercury - 180 and then identified a minimum in that surface, but he couldn ' t identify which of the three variables were responsible for that minimum. ' beautiful experimental achievement ' phil walker of the university of surrey in the uk, who is not a member of the collaboration, describes the research as a " beautiful experimental achievement " that has " an impressive theoretical outcome ". he says that the result will be mainly of interest to academics but believes that it might just have practical implications. " much of our energy generation depends on nuclear fission, " he points out, " and if we want to make reactors safer and cheaper we need to be able to trust the basic theory of the fission process. i would say that the theory has been found to be sadly lacking, and it needs to be fixed. " andreyev agrees. " i hope that as a result of our paper theorists will start to think about this problem and tell us what is happening, " he says. " for the moment we don ' t know. " the research appears in physical review letters. about the author edwin cartlidge is a science writer based in rome