trilobite olenoides erratus. source : mark a. wilson a fossil is the preserved remain of a lifeform that lived in prehistoric times. most commonly fossils are mineralized parts or a whole organism which is no longer alive. in other cases the fossil may contain actual remains of the dead organism ; in particular, dna may be preserved over long periods of time under the right conditions, since dna is fundamentally an inanimate molecule. while the most familiar fossils are those derived from animals and plants including such exotic species as dinosaurs and woolly mammoths, there are also fossils from ancient bacteria. there are several methods of fossil formation including re - crystallization, permineralization, compression, molding and entombment. examination of fossils was the earliest technique of palaeoentology, the study of ancient lifeforms, and it continues as the companion of molecular biology, to be key in the elucidation of phylogenies ( ancestral relationships of species ). the earliest animal fossils date from the cambrian period, approximately 540 million years before present, although some bacterial fossils exist from at least two billion years before present. process of formation most fossils are the result of sedimentary rock formation where coverage of the original organism occurred quickly ; preservation and mineralization is encouraged by anoxic ( oxygen deprived ) conditions, where decompostion was not able to occur rapidly upon death of the subject. body parts most readily preserved are teeth and bony animal parts and the chitonous elements of plants, which elements are most resistive to decay, and thus have more time to enter their preserved state. recrystallized scleractinian fossil coral. source : mark a. wilson one of the simplest processes for fossil formation is the phenomenon of re - crystalization. this is an easily understood process, whereby substances such as teeth and bone, which begin with a high mineral content, have their chemicals replaced by a new crystalline lattice. in a number of instances, mineral replacement of the original body part transpires so gradually that microstructural features are conserved even though a complete transformation of the original organism ' s material occurs. a shell is termed recrystallized when the original skeletal compounds are still present but in a different crystal form, as in a transition form aragonite to calcite. the process of re - crystallization is often termed replacement. living organisms ordinarily contain large amounts of volume that is filled with water or gases. when an organism is covered with sediment, those aqueous


metaphysics - the study of the true nature of reality. metaphysics has evolved over the centuries as human consciousness has developed to include science and spiritual awareness as tools to explore and observe the true nature of reality. reality, or physical reality, includes everything we experience. thoughts, ideas, emotions, perceptions, even what we call dreams and hallucinations, life and death ; all are included in this experience that we call " reality ". science attempts to separate, categorize, quantify, and objectify physical experience, labeling certain aspects as " real " and others as " not real ". metaphysics includes science, and goes beyond it to encompass all aspects and dimensions of life experience as " real ". religion attempts to separate the physical from the non - physical, or spiritual, aspects of life experience, rejecting the physical and calling it " bad " or " evil " while embracing the spiritual and calling that " good " or even " god ". metaphysics goes beyond religions, recognizing that the physical and non - physical are one and not separate, neither good nor bad, and that everything is in fact what we might call " god ". at this point in our conscious evolution, metaphysics has taken its place as the most comprehensive and most effective means of gaining knowledge and understanding or who we really are, why we are here, and the true nature of the physical universe that we can perceive from our present point of view. while science helps us perceive and understand the qualities of various aspects of physical existence, and religion and spirituality can help us integrate what we call non - physical experience into our lives, it is only through metaphysical studies that the " big picture " can be seen and applied. the impact of gaining knowledge of the big picture and learning how to manipulate and affect our world at that level will lead to unimaginable developments in our technologies, social systems, health and well being, and our relationships to our planet and the universe. to ignore metaphysics is to ignore the potential of our future ; to embrace it is to embrace everything that life has to offer. so how can you study metaphysics? i have found the only reliable method is to access truth from the heart. by the heart i mean that zero point in the heart that connects us to source, all that is, god, or whatever you want to call it. once you access this point, you will find your level of awareness expands in a way that permits your conscious mind to perceive physical reality more accurately and effectively. you will then find that the words you


, god, or whatever you want to call it. once you access this point, you will find your level of awareness expands in a way that permits your conscious mind to perceive physical reality more accurately and effectively. you will then find that the words you read, hear and experience coming from " others " are in fact mirrors reflecting back to you the truth you perceived from the heart. this is true knowledge and it will replace belief as your main mode of conscious functioning. learn how to access the heart and continue your studies by exploring the links below. ~ ~ spirituality : how everything is connected. many aspects of the physical world were once beyond the range of human perception. spirituality is the exploration of those aspects of human experience that are still considered " non - physical " only because our technology cannot as yet measure or detect them. ultimately, as science continues to explore spirituality, it discovers that everything is in fact connected. ~ ~ famous scientists and philosophers. these famous scientists and thinkers have devoted a great deal of their lives and energy to the advancement of metaphysical knowledge and ideas. most have made valuable contributions and advancements in areas that contribute directly to the quality of everyday human life. ~ ~ cosmology and the mayan calendar - 2012. today, scientists know that there are powerful electromagnetic fields emanating from the earth, the sun, the center of the galaxy, and even our own hearts. these electromagnetic fields affect and interact with each other. but what is most relevant to the mayan calendar and 2012 is the impact that these cycles, both large and small, have upon life on earth. featured video : metaphysics for life lesson 102 - how it really works.


joined : 16 mar 2004 | posted : thu aug 06, 2009 11 : 24 am post subject : nanotubes could aid understanding of retrovirus transmission | recent findings by medical researchers indicate that naturally occurring nanotubes may serve as tunnels that protect retroviruses and bacteria in transit from diseased to healthy cells — a fact that may explain why vaccines fare poorly against some invaders. to better study the missions of these intercellular nanotubes, scientists have sought the means to form them quickly and easily in test tubes. sandia national laboratories researchers have now learned serendipitously to form nanotubes with surprising ease. “ our work is the first to show that the formation of nanotubes is not complicated, but can be a general effect of protein - membrane interactions alone, ” says darryl sasaki of sandia ' s bioscience and energy center. the tunnel - like structures have been recognized only recently as tiny but important bodily channels for the good, the bad, and the informational. in addition to providing protected transport to certain diseases, the nanotubes also seem to help trundle bacteria to their doom in the tentacles of microphages. lastly, the nanotubes may provide avenues to send and receive information ( in the form of chemical molecules ) from cell to cell far faster than their random dispersal into the bloodstream would permit. given the discovery of this radically different transportation system operating within human tissues, it was natural for researchers to attempt to duplicate the formation of the nanotubes. in their labs, they experimented with giant lipid vesicles that appeared to mimic key aspects of the cellular membrane. giant lipid vesicles resemble micron - sized spherical soap bubbles that exist in water. they are composed of a lipid bilayer membrane only five nanometers thick. the object for experimenters was to create conditions in which the spheres would morph into cylinders of nanometer radii. but researchers had difficulties, says sasaki, perhaps because they used a composite lipid called egg pc that requires unnecessarily high energies to bend into a tubular shape. egg pc is inexpensive, readily available, and offers good, stable membrane properties. it is the usual lipid of choice in forming nanocylinders via mechanical stretching techniques. but sandia postdoctoral researcher haiqing lui instead used popc — a single pure lipid requiring half the bending energy of egg pc. she was trying to generate nanotubes by a completely different approach that involved the use of motor proteins to


antimatter came about as a solution to the fact that the equation describing a free particle in motion ( the relativistic relation between energy, momentum and mass ) has not only positive energy solutions, but negative ones as well! if this were true, nothing would stop a particle from falling down to infinite negative energy states, emitting an infinite amount of energy in the process - - something which does not happen. in 1928, paul dirac postulated the existence of positively charged electrons. the result was an equation describing both matter and antimatter in terms of quantum fields. this work was a truly historic triumph, because it was experimentally confirmed and it inaugurated a new way of thinking about particles and fields. in 1932, carl anderson discovered the positron while measuring cosmic rays in a wilson chamber experiment. in 1955 at the berkeley bevatron, emilio segre, owen chamberlain, clyde wiegand and thomas ypsilantis discovered the antiproton. and in 1995 at cern, scientists synthesized anti - hydrogen atoms for the first time. when a particle and its anti - particle collide, they annihilate into energy, which is carried by " force messenger " particles that can subsequently decay into other particles. for example, when a proton and anti - proton annihilate at high energies, a top - anti - top quark pair can be created! an intriguing puzzle arises when we consider that the laws of physics treat matter and antimatter almost symmetrically. why then don ' t we have encounters with anti - people made of anti - atoms? why is it that the stars, dust and everything else we observe is made of matter? if the cosmos began with equal amounts of matter and antimatter, where is the antimatter? experimentally, the absence of annihilation radiation from the virgo cluster shows that little antimatter can be found within ~ 20 megaparsecs ( mpc ), the typical size of galactic clusters. even so, a rich program of searches for antimatter in cosmic radiation exists. among others, results form the high - energy antimatter telescope, a balloon cosmic ray experiment, as well as those from 100 hours worth of data from the alpha magnetic spectrometer aboard nasa ' s space shuttle, support the matter dominance in our universe. results from nasa ' s orbiting compton gamma ray observatory, however, are uncovering what might be clouds and fountains of antimatter in the galactic center. we stated that there is an approximate symmetry


learning causality in a complex world : understandings of consequence source : rowman & littlefield education, lanham, maryland ( 2012 ) call number : cubb bd591. g765 2012 contents : introduction - - simple linear causality : one thing makes another happen - - the cognitive science of simple causality : why do we get stuck? - - domino causality : effects that become causes - - cyclic causality : loops and feedback - - spiraling causality : escalation and de - escalation - - mutual causality : symbiosis and bi - directionality - - relational causality : balances and differentials - - across time and distance : detecting delayed and distant effects - - " what happened? " vs. " what ' s going on? " : thinking about steady states - - what you can ' t see does matter : attending to obvious and non - obvious causes - - it ' s not always a case of who did it : minding passive and unintentional causality - - step by step, or not : the mind - bending concept of simultaneous causality - - figuring out what to count on : dealing with stochastic causality - - isn ' t anybody in charge around here? : attending to distributed causality and emergence - - summing up : the implications for helping a new generation understand causal complexity - - putting it all together : teaching for causal complexity.


press release : the 2003 nobel prize in physics 7 october 2003 the royal swedish academy of sciences has decided to award the nobel prize in physics for 2003 " for pioneering contributions to the theory of superconductors and superfluids " alexei a. abrikosov argonne national laboratory, argonne, illinois, usa, vitaly l. ginzburg p. n. lebedev physical institute, moscow, russia, and anthony j. leggett university of illinois, urbana, illinois, usa flow without resistance this year ' s nobel prize in physics is awarded to three physicists who have made decisive contributions concerning two phenomena in quantum physics : superconductivity and superfluidity. superconducting material is used, for example, in magnetic resonance imaging for medical examinations and particle accelerators in physics. knowledge about superfluid liquids can give us deeper insight into the ways in which matter behaves in its lowest and most ordered state. at low temperatures ( a few degrees above absolute zero ) certain metals allow an electric current to pass without resistance. such superconducting materials also have the property of being able to displace magnetic flows completely or partly. those that displace magnetic flows completely are called type - i superconductors and a theory explaining them was awarded the nobel prize in physics in 1972. this theory, which is based on the fact that pairs of electrons are formed proved, however, to be inadequate for explaining superconductivity in the technically most important materials. these type - ii superconductors allow superconductivity and magnetism to exist at the same time and remain superconductive in high magnetic alexei abrikosov succeeded in explaining this phenomenon theoretically. his starting point was a theory that had been formulated for type - i superconductors by vitaly ginzburg and others, but which proved to be so comprehensive that it was also valid for the new type. although these theories were formulated in the 1950s, they have gained renewed importance in the rapid development of materials with completely new properties. materials can now be made superconductive at increasingly high temperatures and strong magnetic fields. liquid helium can become superfluid, that is, its viscosity vanishes at low temperatures. atoms of the rare isotope 3he have to form pairs analogous with pairs of electrons in metallic superconductors. the decisive theory explaining how the atoms interact and are ordered in the superfluid state was formulated in the 1970s by anthony leggett. recent


the rare isotope 3he have to form pairs analogous with pairs of electrons in metallic superconductors. the decisive theory explaining how the atoms interact and are ordered in the superfluid state was formulated in the 1970s by anthony leggett. recent studies show how this order passes into chaos or turbulence, which is one of the unsolved problems of classical physics. alexei a. abrikosov, born 1928 ( 75 years ) in moscow, the former soviet union, american ( and russian ) citizen. doctor ' s degree in physics in 1951 at the institute for physical problems, moscow. distinguished argonne scientist, argonne national laboratory, argonne, illinois, usa. vitaly l. ginzburg, born 1916 ( 87 years ) in moscow, russia ( russian citizen ). doctor ' s degree in physics at the university of moscow. former head of the theory group at the p. n. lebedev physical institute, moscow, russia. anthony j. leggett, born 1938 ( 65 years ) in london, england ( british and american citizen ). doctor ' s degree in physics in 1964 at the university of oxford. macarthur professor at the university of illinois at urbana - champaign, prize amount : sek 10 million, will be shared equally among the laureates. science editor, phone + 46 8 673 95 44, + 46 703 27 72 00, email @ example. com and eva krutmeijer, head of information, phone + 46 8 673 95 95, + 46 709 84 66 38, firstname. lastname @ example. org


of energy from one physical system to another expressed as the product of a force and the distance through which it moves a body in the direction of that force ; " work equals force times distance " hypernym ( s ) : energy, free _ energy 10. work - noun · a place where work is done ; " he arrived at work early today " hypernym ( s ) : geographic _ point, geographical _ point 11. work - noun · the total output of a writer or artist ( or a substantial part of it ) ; " he studied the entire wagnerian oeuvre " ; " picasso ' s work can be divided into periods " synonym ( s ) : oeuvre, body _ of _ work hypernym ( s ) : end _ product, output 12. work - verb · exert oneself by doing mental or physical work for a purpose or out of necessity ; " i will work hard to improve my grades " ; " she worked hard for better living conditions for the poor " 13. work - verb · be employed ; " is your husband working again? " ; " my wife never worked " ; " do you want to work after the age of 60? " ; " she never did any work because she inherited a lot of money " ; " she works as a waitress to put herself through college " 14. work - verb · have an effect or outcome ; often the one desired or expected ; " the voting process doesn ' t work as well as people thought " ; " how does your idea work in practice? " ; " this method doesn ' t work " ; " the breaks of my new car act quickly " ; " the medicine works only if you take it with a lot of water " hypernym ( s ) : succeed, win, come _ through, bring _ home _ the _ bacon, deliver _ the _ goods 15. work - verb · perform as expected when applied ; " the washing machine won ' t go unless it ' s plugged in " ; " does this old car still run well? " ; " this old radio doesn ' t work anymore " synonym ( s ) : function, operate, go, run 16. work - verb · shape, form, or improve a material ; " work stone into tools " ; " process iron " ; " work the metal " synonym ( s ) : work _ on, process hypernym ( s ) : transform, transmute, transubstantiate 17. work - verb · give a workout to ; " some parents


elemental analysis is a process where a sample of some material ( e. g., soil, waste or drinking water, bodily fluids, minerals, chemical compounds ) is analyzed for its elemental and sometimes isotopic composition. elemental analysis can be qualitative ( determining what elements are present ), and it can be quantitative ( determining how much of each are present ). elemental analysis falls within the ambit of analytical chemistry, the set of instruments involved in decyphering the chemical nature of our world. for synthetic chemists, elemental analysis or " ea " almost always refers to chnx analysis — the determination of the percentage weights of carbon, hydrogen, nitrogen, and heteroatoms ( x ) ( halogens, sulfur ) of a sample. this information is important to help determine the structure of an unknown compound, as well as to help prove the structure and purity of a synthesized compound. the most common form of elemental analysis, chn analysis, is accomplished by combustion analysis. in this technique, a sample is burned in an excess of oxygen, and various traps collect the combustion products — carbon dioxide, water, and nitric oxide. the weights of these combustion products can be used to calculate the composition of the unknown sample. other quantitative methods include : - gravimetry, where the sample is dissolved and then the element of interest is precipitated and its mass measured or the element of interest is volatilized and the mass loss is measured. - optical atomic spectroscopy, such as flame atomic absorption, graphite furnace atomic absorption, and inductively coupled plasma atomic emission, which probe the outer electronic structure of atoms. to qualitatively determine which elements exist in a sample, methods include : - mass spectrometric atomic spectroscopy, such as inductively coupled mass spectrometry, which probes the mass of atoms. - other spectroscopy which probes the inner electronic structure of atoms such as x - ray fluorescence, particle induced x - ray emission, x - ray photoelectron spectroscopy, and auger electron spectroscopy. - electrochemical methods there is no pharmaceutical or device industry support for this site and we need your viewer supported donations | editorial board | governance | licensing | disclaimers | avoid plagiarism | policies


, you can use entropy to modify the state as well, to make sure things don ’ t get too predictable. most operating systems have special ways of getting “ secure ” random numbers that handle this for you. another example of entropy : if you play the game dragon warrior for the nintendo, but use an emulator instead of a real nintendo, then you can save a snapshot of your game before you fight a monster, memorize what the monsters are going to do, and figure out exactly the right way to respond. when you load the game from the snapshot and try again, as long as you do the same things, the monster will respond in exactly the same way! that ’ s because the snapshot saves the state of the random number generator, so when you go back and load from the snapshot, the computer picks the same random numbers. so if a fight against a monster is going well but you make a disastrous move at the end, you can load your snapshot and repeat the exact same fight up to that point. the same trick doesn ’ t work in dragon warrior 2 ( or later ones ), though! why not? because the company that makes the game started using entropy in their sequel. so now little things like exactly how long you wait between pressing buttons will change the game. since you can ’ t possibly time everything exactly the same down to hundredths or thousandths of a second, the task is hopeless, and you have to just take your chances and trust to luck. so as you can see, random numbers can become a very tricky topic. but ultimately it ’ s all just a complicated formula, a seed, and a state.


| name, symbol, number | | krypton, kr, 36 | chemical series | | noble gases | | group, period, block | | 18, 4, p | | appearance | | colorless | | atomic mass | | 83. 798 ( 2 ) g / mol | | electron configuration | | [ ar ] 3d10 4s2 4p6 | | electrons per shell | | 2, 8, 18, 8 | | density | | ( 0 °c, 101. 325 kpa ) | | melting point | | 115. 79 k | ( - 157. 36 °c, - 251. 25 °f ) | boiling point | | 119. 93 k | ( - 153. 22 °c, - 243. 8 °f ) | critical point | | 209. 41 k, 5. 50 mpa | | heat of fusion | | 1. 64 kj · mol−1 | | heat of vaporization | | 9. 08 kj · mol−1 | | heat capacity | | ( 25 °c ) 20. 786 j · mol−1 · k−1 | | crystal structure | | cubic face centered | | electronegativity | | 3. 00 ( pauling scale ) | | ionization energies | | 1st : 1350. 8 kj · mol−1 | | 2nd : 2350. 4 kj · mol−1 | | 3rd : 3565 kj · mol−1 | | atomic radius ( calc. ) | | 88 pm | | covalent radius | | 110 pm | | van der waals radius | | 202 pm | | thermal conductivity | | ( 300 k ) 9. 43 mw · m−1 · k−1 | | speed of sound | | ( gas, 23 °c ) 220 m / s | | speed of sound | | ( liquid ) 1120 m / s | | cas registry number | | 7439 - 90 - 9 | krypton ( ipa : / ˈkrɪptən / or / ˈkrɪptan / ) is a chemical element with the symbol kr and atomic number 36. a colorless, odorless, tasteless noble gas, krypton occurs in trace amounts in the atmosphere, is isolated by fractionating liquefied air, and is often used with other rare gases in fluorescent lamps. krypton is inert for most practical purposes but it is known to form compounds with fluorine. krypton can also form clathrates with water when atoms of


air, and is often used with other rare gases in fluorescent lamps. krypton is inert for most practical purposes but it is known to form compounds with fluorine. krypton can also form clathrates with water when atoms of it are trapped in a lattice of the water molecules. notable characteristics edit krypton, a noble gas due to its very low chemical reactivity, is characterized by a brilliant green and orange spectral signature. it is one of the products of uranium fission. solidified krypton is white and crystalline with a face - centered cubic crystal structure which is a common property of all " rare gases ". in 1960 an international agreement defined the metre in terms of light emitted from a krypton isotope. this agreement replaced the longstanding standard metre located in paris which was a metal bar made of a platinum - iridium alloy ( the bar was originally estimated to be one ten millionth of a quadrant of the earth ' s polar circumference ). but only 23 years later, the krypton - based standard was replaced itself by the speed of light — the most reliable constant in the universe. in october 1983 the bureau international des poids et mesures ( international bureau of weights and measures ) defined the metre as the distance that light travels in a vacuum during 1 / 299, 792, 458 s. like the other noble gases, krypton is widely considered to be chemically inert. following the first successful synthesis of xenon compounds in 1962, synthesis of krypton difluoride was reported in 1963. other fluorides and a salt of a krypton oxoacid have also been found. arkr + and krh + molecule - ions have been investigated and there is evidence for krxe or krxe +. there are 32 known isotopes of krypton. naturally occurring krypton is made of five stable and one slightly radioactive isotope. krypton ' s spectral signature is easily produced with some very sharp lines. 81kr is the product of atmospheric reactions with the other naturally occurring isotopes of krypton. it is radioactive with a half - life of 250, 000 years. like xenon, krypton is highly volatile when it is near surface waters and 81kr has therefore been used for dating old ( 50, 000 - 800, 000 year ) groundwater. 85kr is an inert radioactive noble gas with a half - life of 10. 76 years, that is produced by


williams, h. paul ( 2009 ) logic and integer programming. international series in operations research & management science. springer, london, uk. isbn 9780387922799 integer programming ( discrete optimization ) is best used for solving problems involving discrete, whole elements. using integer variables, one can model logical requirements, fixed costs, sequencing and scheduling requirements, and many other problem aspects. whether it ’ s taught in or graduate programs or in math or computer science programs ; in courses called " integer programming, " " combinatorial optimization, " " combinatorial optimization and integer programming " or simply " advanced operations management, " it ’ s a part of every or curriculum, and one of its greatest teachers has developed a text that shows how to use logic in integer programming to develop models with much greater precision. paul williams, a leading authority on modeling in integer programming, has written a concise, readable introduction to the science and art of using modeling in logic for integer programming. written for graduate and postgraduate students, as well as academics and practitioners, the book is divided into four chapters that all avoid the typical format of definitions, theorems and proofs and instead introduce concepts and results within the text through examples. references are given at the end of each chapter to the more mathematical papers and texts on the subject, and exercises are included to reinforce and expand on the material in the chapter. chapter 1 gives a basic introduction to logic and its aims, and goes on to explain the propositional and predicate calculus. chapter 2 explains linear programming ( lp ) and integer programming ( ip ) using the machinery of logic ; explains the fundamental structural and mathematical properties of these types of models, along with the main methods of solving ip models ; covers main areas of practical application ; and attempts to distinguish between computationally ‘ difficult ’ and ‘ easy ’ classes of problem. chapter 3 applies logic to the formulation of ip models using the methods explained in chapter 1 and looks at the deeper mathematical concepts involved. chapter 4 then covers the fundamental problem of computational logic : the satisfiability problem, which lies at the heart of the entire book. methods of solving with both logic and ip are given and their connections are described. applications in diverse fields are discussed, and williams shows how ip models can be expressed as satisfiability problems and solved as such. | additional information : | | © 2009 h. paul williams | | library of congress subject classification : | | z bibliography. library science. information resources > za information resources > za4050 electronic


concept. the basic idea is that the human mind can keep track of about seven at once, or can differentiate between seven or so different ( but similar ) things. the phrase comes from the title of a 1956 paper by harvard professor george a. miller titled, the magical number seven, plus or minus two : some limits on our capacity for processing information, which begins : my problem is that i have been persecuted by an integer. for seven years this number has followed me around, has intruded in my most private data, and has assaulted me from the pages of our most public journals. this number assumes a variety of disguises, being sometimes a little larger and sometimes a little smaller than usual, but never changing so much as to be unrecognizable. the persistence with which this number plagues me is far more than a random accident. there is, to quote a famous senator, a design behind it, some pattern governing its appearances. either there really is something unusual about the number or else i am suffering from delusions of persecution. miller goes on to present data from a number of experiments which support the idea ( by arriving at the number seven ). topics of the experiments he reviewed included, " span of immediate memory ", " capacity for absolute judgements of the position of a dot on a square ", and ( my favorite ) " capacity for absolute judgements of saltiness


search loci : convergence : the reader may here observe the force of numbers, which can be successfully applied, even to those things, which one would imagine are subject to no rules. there are very few things which we know, which are not capable of being reduc ' d to a mathematical reasoning ; and when they cannot it ' s a sign our knowledge of them is very small and confus ' d ; and when a mathematical reasoning can be had it ' s as great a folly to make use of any other, as to grope for a thing in the dark, when you have a candle standing by you. of the laws of chance ( 1692 ) georg cantor at the dawn of point - set topology a first course in point - set topology can be challenging for the student because of the abstract level of the material. in an attempt to mitigate this problem, we use the history of point - set topology to obtain natural motivation for the study of some key concepts. in this article, we study an 1872 paper by georg cantor. we will look at the problem cantor was attempting to solve and see how the now familiar concepts of a point - set and derived set are natural answers to his question. we emphasize ways to utilize cantor ' s methods in order to introduce point - set topology to students. in his introduction to his book introduction to phenomenology, msgr. robert sokolowski writes as a philosopher, msgr. sokolowski is accustomed to the traditional methods of teaching philosophy to undergraduates – start with plato, aristotle and the other ancients, continue with developments through the scholastic and enlightenment eras, and then show how modern philosophy builds upon all that has gone before. he must be puzzled, then, by the lack of attention to the historical development of ideas that generally attends to the teaching of mathematics. he perceives that something important is missing, and he is correct. in recent years, interest has grown considerably in developing an historical approach to the teaching of mathematics. victor katz has edited an anthology of articles giving different perspectives on the development of mathematics in general from an historical point of view. some authors, such as klyve, stemkoski, and tou, focus on one particular historical figure – in their case, euler – important to the development of mathematics. there is also interest in the historical development of certain areas of mathematics commonly included in the undergraduate curriculum. brian hopkins has written a textbook introducing discrete mathematics from an historical point of view ; david bressoud has written two textbooks that present


need the other part, too. among these 27 / 196 of the families, 13 / 196 of all families have two boys, by pure counting, so the result is p = 13 / 27as the fraction of the families that satisfied the condition. note that it is just slightly less than 1 / 2 = 13. 5 / 27 i. e. much more than 1 / 3. i had to highlight the result because almost no one reads the full article and almost no one notices that the right results is neither 1 / 3 nor 1 / 2. indeed, the large difference of the right result from 1 / 3 appears because one de facto identifies one of the sons by mentioning that it is the kid from tuesday. if you assumed there were infinitely many days in a week and you would take any family with at least one tuesday kid, the " tuesday " information would identify this kid completely ( two tuesday kids would be infinitesimally unlikely ), and the question what is the probability of 2 sons would be reduced to the question what is the probability that the other, equally specific kid - the non - tuesday kid - is male - which is of course 1 / 2. i will discuss this " identification " and reasons why the result is close to 1 / 2 at the very end. indistinguishable kids ' bound states with kids that would satisfy the bose or fermi statistics, the counting would be different but equally straightforward. instead of 14 x 14 = 196 possibilities, one has 14 x 15 / 2 = 105 for bosons ( the symmetric triangle ) and 14 x 13 / 2 = 91 ( the antisymmetric triangle ) for fermions. among the 105 or 91 options, how many of them contain at least one tuesday son? well, in these two cases, we can ' t say which of them is older and younger : they ' re identical. so if there is at least 1 tuesday son, the number of states with at least 1 tuesday son is 14 for the bosons - we can just create the other particle into the 1 - particle state - or 13 for the fermions - we can also add the second creation operator, but with another tuesday son, the state will vanish because of pauli ' s exclusion principle. among these 14 or 13 states respectively, for bosons and fermions, 7 or 6 are two - son states, respectively. so the odds are 7 / 14 = 1 / 2 for the bosons and 6 / 13 for the fermions. note that the


states respectively, for bosons and fermions, 7 or 6 are two - son states, respectively. so the odds are 7 / 14 = 1 / 2 for the bosons and 6 / 13 for the fermions. note that the bosons literally saturate the 1 / 2 bound while the fermions are just slightly below it. why not one third? finally, i want to comment on " why the information about tuesday matters ". if we sum up the probabilities for the problems where the son is born on sunday, monday... and up to saturday, shouldn ' t we get the same result? and by symmetry, the result must be equal for all 7 days, so doesn ' t each term have to be 1 / 3? the answer is that we can ' t add the probabilities in this way because the " at least one monday son " etc. are assumptions, not propositions conditioned by these assumptions, and they ' re not disjoint. at any rate, the calculation is nonlinear because the conditional probabilities have the probability of the assumption in the denominator rather than the numerator, so you can ' t simply add the possibilities in any way. the word term in the previous paragraph is therefore incorrect. how and why 1 / 3 gets enhanced to nearly 1 / 2 if you were only told that " one of the kids is a boy ", the mixed families would be overrepresented over the two - boy families by the 2 - to - 1 ratio because boy - girl and girl - boy families are as likely as boy - boy families ; again, the kids notation is younger - older. however, if you ' re told that " one of the kids is a tuesday boy ", this overrepresentation almost disappears. why? because 1 / 7 of the boy - girl and girl - boy families have a tuesday boy. but ( approximately ) 2 / 7 of the boy - boy families have at least one tuesday boy because each of these two boys has a chance to be born on tuesday. in this way, the boy - boy families ( nearly ) compensate the factor of two by which they were underrepresented relatively to the mixed families. bonus : this puzzle and crackpot sean carroll ' s misunderstanding of logic this logical puzzle is actually a very precise pedagogical example showing what ' s wrong with the thinking of various people about the arrow of time. some people - those who say that the information about tuesday doesn ' t


to experimental data of the proton transfer in this polypeptide showed the possibilities of the simulation of the lrpt by the sdmc algorithm. the promising results encouraged us to investigate the mechanism of the lrpt, especially, if the reorientation of the hbn or the electrostatic energy barrier of the charge transfer is rate limiting for the lrpt. the results indicate, that both effects influence the lrpt and none of them is exclusively responsible for the lrpt rate. further analysis of the hydrogen bond network topology showed that graph algorithms can be used to analyze these networks. hydrogen bond networks can be clustered into regions which are close connected to each other. on the other hand, residues connecting two or more of these densely connected regions might play an important role for proton transfer pathways since a loss of such residues cuts a proton transfer pathway. a comparison of an analysis of the hbn topology of the photosynthetic reaction center with mutation studies of the same system showed, that residues identified as important for proton transfer by the mutation studies are identified as connection points between clusters by the network analysis. the developed algorithms together with the introduction of a new method for the simulation of the lrpt process ( sdmc ) improved the picture of the proton transfer processes in proteins. starting from the protein structure, the developed algorithms cover all steps from the detection of protein cavities, the placement of water molecules in these cavities, the calculation and analysis of the hydrogen bond network, the simulation of the lrpt and the investigation of the reaction kinetics. the analysis of the hbn by graph theoretical methods gives further insight into the hbn topology and identifies residues important for proton transfer pathways and therefore important for the protein activity.


closing in on the planck constant sep 25, 1998 physicists in the us have made the most accurate measurements ever of the planck constant, h. edwin williams and colleagues at the national institute of standards and technology in gaithersburg, maryland, measured h by comparing the voltage needed to control the velocity of a coil moving vertically in an magnetic field, with the current that has to be passed through the coil to balance gravity in the same magnetic field. the measurement could lead to a new reference stand for the kilogram ( phys. rev. lett. 81 2404 ). the kilogram is currently defined by a platinum - iridium alloy maintained at the bureau international des poids et mesures ( bipm ) in paris and six official copies. however, the official mass of the standard kilogram has been known to vary with time, hence the interest in defining the kilogram is terms of fundamental constants like h. the highly stable magnetic field needed for the experiment is generated by a superconducting magnet that has been cooled to 4 kelvin. the experiment also uses two induction coils : the lower coil is fixed to the support structure of the experiment, while the upper coil can move. this upper coil is also attached to a wheel balance above the experiment. in the first stage of the measurement, the mass balance is empty and a small force is applied to the upper coil, forcing it to move at 2mm / s. the researchers found that this generated a voltage of 1. 018 ± 0. 001 v across the moving coil. in the second stage of the experiment, a 500 g countermass is balanced by a - 10. 18 ma current in the induction coil. both stages were repeated over many months to obtain a value of 6. 62606891 ( 58 ) x 10 - 34 joule seconds for the planck constant. this result - which corresponds to an accuracy of 9 parts in 108 - is a factor of 15 better than previous measurements. the team hope to improve on this result by another factor of 10 by modifying their experiment.


ultrafast electron microscope makes movies dec 8, 2006 physicists have created a new form of electron microscopy that can make " movies " of atoms as they undergo ultra - rapid chemical or structural transitions. ahmed zewail and colleagues at the california institute of technology in the us have used coincident electron and laser pulses to follow vanadium and oxygen atoms as they rearranged themselves on a vanadium oxide surface over the course of several picoseconds. the researchers say that the technique could also be used to study a wide range of ultrafast biological and physical phenomena. ( proc. natl. acad. sci. 103 18427 ) ). electron microscopes have better resolution than optical microscopes because high - energy electrons have a much shorter wavelength than light. the resolution can be further improved by using coherent electron wavepackets, which can contain as few as one electron. the wavelengths of these packets are much smaller than the space between individual atoms and can be brought to a very sharp focus, allowing objects to be imaged with atomic - scale resolution. the packets are of extremely short duration and this can be exploited to take “ snapshots ” of atoms as they undergo structural or chemical transitions. in 2005, zewail and colleagues used coherent electron packets to take single snapshots of a number of materials and biological samples. now the researchers have further refined their technique to take a time sequence of images that allowed them to watch vanadium and oxygen atoms rearrange themselves in a process that can take as little as 100 femtoseconds ( 10 - 13 seconds ). the timing sequence is generated by femtosecond laser pulses as illustrated in the figure " ultrafast microscope ". each pulse is split into two pulses – one is used by the microscope to create the electron pulse and the other is used to heat the sample. according to zewail, the crucial and most difficult part of the technique is coordinating the arrivals of the laser and electron pulses at the sample with an accuracy of just a few femtoseconds. this is particularly difficult because the laser pulse travels at the speed of light, while the electron pulse lags behind at about two thirds the speed of light. the coincident laser pulse is used to heat the sample and drive a transition from a low - temperature crystal structure to a high - temperature structure. by changing the delay between the laser and electron pulses in regular time steps, the researchers were able to take snapshots of the atoms at different sample temperatures. zewai


an intermediate phenotype, or codominance by expressing both alleles at once. when a pair of organisms reproduce sexually, their offspring randomly inherit one of the two alleles from each parent. these observations of discrete inheritance and the segregation of alleles are collectively known as mendel ' s first law or the law of segregation. notation and diagramsedit geneticists use diagrams and symbols to describe inheritance. a gene is represented by a letter ( or letters ) — the capitalized letter represents the dominant allele and the recessive is represented by lowercase. often a " + " symbol is used to mark the usual, non - mutant allele for a gene. in fertilization and breeding experiments ( and especially when discussing mendel ' s laws ) the parents are referred to as the " p " generation and the offspring as the " f1 " ( first filial ) generation. when the f1 offspring mate with each other, the offspring are called the " f2 " ( second filial ) generation. one of the common diagrams used to predict the result of cross - breeding is the punnett square. interactions of multiple genesedit organisms have thousands of genes, and in sexually reproducing organisms assortment of these genes are generally independent of each other. this means that the inheritance of an allele for yellow or green pea color is unrelated to the inheritance of alleles for white or purple flowers. this phenomenon, known as " mendel ' s second law " or the " law of independent assortment ", means that the alleles of different genes get shuffled between parents to form offspring with many different combinations. ( some genes do not assort independently, demonstrating genetic linkage, a topic discussed later in this article. ) often different genes can interact in a way that influences the same trait. in the blue - eyed mary ( omphalodes verna ), for example, there exists a gene with alleles that determine the color of flowers : blue or magenta. another gene, however, controls whether the flowers have color at all : color or white. when a plant has two copies of this white allele, its flowers are white - regardless of whether the first gene has blue or magenta alleles. this interaction between genes is called epistasis, with the second gene epistatic to the first. many traits are not discrete features ( eg. purple or white flowers ) but are instead continuous features ( eg. human height and skin color ). these complex traits are the product of many


key : " s : " = show synset ( semantic ) relations, " w : " = show word ( lexical ) relations display options for sense : ( gloss ) " an example sentence " - s : ( n ) bear ( massive plantigrade carnivorous or omnivorous mammals with long shaggy coats and strong claws ) - s : ( n ) bear ( an investor with a pessimistic market outlook ; an investor who expects prices to fall and so sells now in order to buy later at a lower price ) - s : ( v ) bear ( have ) " bear a resemblance " ; " bear a signature " - s : ( v ) give birth, deliver, bear, birth, have ( cause to be born ) " my wife had twins yesterday! " - s : ( v ) digest, endure, stick out, stomach, bear, stand, tolerate, support, brook, abide, suffer, put up ( put up with something or somebody unpleasant ) " i cannot bear his constant criticism " ; " the new secretary had to endure a lot of unprofessional remarks " ; " he learned to tolerate the heat " ; " she stuck out two years in a miserable marriage " - s : ( v ) bear ( move while holding up or supporting ) " bear gifts " ; " bear a heavy load " ; " bear news " ; " bearing orders " - s : ( v ) bear, turn out ( bring forth ) " the apple tree bore delicious apples this year " ; " the unidentified plant bore gorgeous flowers " - s : ( v ) bear, take over, accept, assume ( take on as one ' s own the expenses or debts of another person ) " i ' ll accept the charges " ; " she agreed to bear the responsibility " - s : ( v ) hold, bear, carry, contain ( contain or hold ; have within ) " the jar carries wine " ; " the canteen holds fresh water " ; " this can contains water " - s : ( v ) yield, pay, bear ( bring in ) " interest - bearing accounts " ; " how much does this savings certificate pay annually? " - s : ( v ) wear, bear ( have on one ' s person ) " he wore a red ribbon " ; " bear a scar " - s : ( v ) behave, acquit, bear, deport, conduct, comport, carry ( behave in a certain manner ) " she carried herself well " ; " he bore himself with dignity " ; "


key : " s : " = show synset ( semantic ) relations, " w : " = show word ( lexical ) relations display options for sense : ( gloss ) " an example sentence " - s : ( n ) skim ( a thin layer covering the surface of a liquid ) " there was a thin skim of oil on the water " - s : ( n ) skim, skimming ( reading or glancing through quickly ) - s : ( v ) plane, skim ( travel on the surface of water ) - s : ( v ) skim over, skim ( move or pass swiftly and lightly over the surface of ) - s : ( v ) scan, skim, rake, glance over, run down ( examine hastily ) " she scanned the newspaper headlines while waiting for the taxi " - s : ( v ) skim, skip, skitter ( cause to skip over a surface ) " skip a stone across the pond " - s : ( v ) skim ( coat ( a liquid ) with a layer ) - s : ( v ) skim, skim off, cream off, cream ( remove from the surface ) " skim cream from the surface of milk " - s : ( v ) skim, skim over ( read superficially ) - s : ( adj ) skim, skimmed ( used of milk and milk products from which the cream has been removed ) " yogurt made with skim milk " ; " she can drink skimmed milk but should avoid butter "


biodegradable transistors - - made from us wednesday, march 7, 2012 award - winning tau research uses self - assembling blood, milk, and mucus proteins to build next generation technology silicon, a semi - conducting element, is the basis of most modern technology, including cellular phones and computers. but according to tel aviv university researchers, this material is quickly becoming outdated in an industry producing ever - smaller products that are less harmful to the environment. now, a team including ph. d. students elad mentovich and netta hendler of tau ' s department of chemistry and the center for nanoscience and nanotechnology, with supervisor dr. shachar richter and in collaboration with prof. michael gozin and his ph. d. student bogdan belgorodsky, has brought together cutting - edge techniques from multiple fields of science to create protein - based transistors — semi - conductors used to power electronic devices — from organic materials found in the human body. they could become the basis of a new generation of nano - sized technologies that are both flexible and biodegradable. working with blood, milk, and mucus proteins which have the ability to self - assemble into a semi - conducting film, the researchers have already succeeded in taking the first step towards biodegradable display screens, and they aim to use this method to develop entire electronic devices. their research, which has appeared in the journals nano letters and advanced materials, recently received a silver award at the materials research society graduate student awards in boston, ma. building the best transistor from the bottom up netta hendler, elad mentovich, and bogdan belgorodsky one of the challenges of using silicon as a semi - conductor is that a transistor must be created with a " top down " approach. manufacturers start with a sheet of silicon and carve it into the shape that is needed, like carving a sculpture out of a rock. this method limits the capabilities of transistors when it comes to factors such as size and flexibility. the tau researchers turned to biology and chemistry for a different approach to building the ideal transistor. when they appled various combinations of blood, milk, and mucus proteins to any base material, the molecules self - assembled to create a semi - conducting film on a nano - scale. in the case of blood protein, for example, the film is approximately four nanometers high. the current technology in use now is 18 nanometers, says men


self - assembled to create a semi - conducting film on a nano - scale. in the case of blood protein, for example, the film is approximately four nanometers high. the current technology in use now is 18 nanometers, says mentovich. together, the three different kinds of proteins create a complete circuit with electronic and optical capabilities, each bringing something unique to the table. blood protein has the ability to absorb oxygen, mentovich says, which permits the " doping " of semi - conductors with specific chemicals in order to create specific technological properties. milk proteins, known for their strength in difficult environments, form the fibers which are the building blocks of the transistors, while the mucosal proteins have the ability to keep red, green and, blue fluorescent dyes separate, together creating the white light emission that is necessary for advanced optics. overall, the natural abilities of each protein give the researchers " unique control " over the resulting organic transistor, allowing adjustments for conductivity, memory storage, and fluorescence among other characteristics. a new era of technology technology is now shifting from a silicon era to a carbon era, notes mentovich, and this new type of transistor could play a big role. transistors built from these proteins will be ideal for smaller, flexible devices that are made out of plastic rather than silicon, which exists in wafer form that would shatter like glass if bent. the breakthrough could lead to a new range of flexible technologies, such as screens, cell phones and tablets, biosensors, and microprocessor chips. just as significant, because the researchers are using natural proteins to build their transistor, the products they create will be biodegradable. it ' s a far more environmentally friendly technology that addresses the growing problem of electronic waste, which is overflowing landfills worldwide. for more technology news from tel aviv university, click here.


development of reliable closed - cycle life - support systems for multi - year missions. these missions also require new technologies such as aerobraking ( to help conserve propellants by utilizing the atmospheres of mars and earth for flight maneuvers ), storage and handling of cryogenics, ( i. e., gases supercooled to liquid form ), new spacesuits with greater flexibility and higher comfort for strenuous activity on the mars surface, solar and nuclear power systems, and local - resources utilization for producing propellants and other substances necessary for life. to shorten flight time and thus reduce the en - route exposure to microgravity and space radiation, human mars missions will also favor nuclear propulsion systems. nasa is studying advanced nuclear propulsion concepts, and our russian iss partner roskosmos is well advanced in the development of nuclear - electric propulsion. our exploration of the red planet is aimed not just at the search for life or later settlement by people but also at nearer - term objectives of quite concrete relevance for the present, motivated by fundamental questions such as why our sun has planets in the first place, how is it possible that earth and with it we humans exist, and is earth ' s and our existence an extraordinary or normal occurrence in the cosmos? why are we in this world, how did it come about, could it also have happened differently, and what will become of us? even more importantly, we are also exploring mars in order to better understand our terrestrial environment, to improve our ability to more accurately determine what we are changing on earth by our activities - on its surface and its atmosphere. mars is particularly well suited for such comparative planetology. the exploration of its topography, geology, geography, atmosphere, weather and climate conditions, developmental phases, indeed the entirety of its physical and chemical characteristics will add fundamentally to our knowledge and understanding of our own environment, thus serving considerably more than just the pure satisfaction of abstract human curiosity. mars ' formation and development still pose great riddles for science : it is the only other planet beside earth with a surface clearly marked by complex geological processes caused by ice ages, glaciers, and flowing water in niagara quantities. and that in a world which is so bone - dry today that all water in its presently considerably thinned - down carbon dioxide atmosphere would form a layer only two to five hundredths millimeter thick if it rained down to the ground all at once. mars has ice fields, mysterious dark zones, bright " deserts ", and various types of cloud formations which are subject to continual


this multimedia lesson for grades 7 - 10 explores the physical forces that act in concert to create snowflakes. students build an apparatus that creates conditions similar to a winter cloud and produce their own snow crystals indoors. by watching the snow crystals grow, they learn about how snowflake size and shape is determined by the forces that act on water molecules at the atomic and molecular levels. digital models and snowflake photo galleries bring together a cohesive package to help kids visualize what ' s happening at the molecular scale. editor ' s note : this lab activity calls for dry ice. see related materials for a link to the noaa ' s " dry ice safety " guidelines, and for a link to snow crystal images produced by an electron microscope. lewis structures, vsepr, condensation, covalent bond, crystals, electron sharing, ice, physics of snowflakes, snow formation, valence electrons, valence shell metadata instance created january 2, 2013 by caroline hall january 2, 2013 by caroline hall aaas benchmark alignments ( 2008 version ) 4. the physical setting 4b. the earth 6 - 8 : 4b / m15. the atmosphere is a mixture of nitrogen, oxygen, and trace amounts of water vapor, carbon dioxide, and other gases. 4d. the structure of matter 6 - 8 : 4d / m1a. all matter is made up of atoms, which are far too small to see directly through a microscope. 6 - 8 : 4d / m1cd. atoms may link together in well - defined molecules, or may be packed together in crystal patterns. different arrangements of atoms into groups compose all substances and determine the characteristic properties of substances. 6 - 8 : 4d / m3cd. in solids, the atoms or molecules are closely locked in position and can only vibrate. in liquids, they have higher energy, are more loosely connected, and can slide past one another ; some molecules may get enough energy to escape into a gas. in gases, the atoms or molecules have still more energy and are free of one another except during occasional collisions. 9 - 12 : 4d / h2. the number of protons in the nucleus determines what an atom ' s electron configuration can be and so defines the element. an atom ' s electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. atoms form bonds to other atoms by transferring or sharing electrons. 9 - 12 : 4d / h7a. atoms often join with one another in various


electron configuration, particularly the outermost electrons, determines how the atom can interact with other atoms. atoms form bonds to other atoms by transferring or sharing electrons. 9 - 12 : 4d / h7a. atoms often join with one another in various combinations in distinct molecules or in repeating three - dimensional crystal patterns. 12. habits of mind 12c. manipulation and observation 6 - 8 : 12c / m3. make accurate measurements of length, volume, weight, elapsed time, rates, and temperature by using appropriate devices. < a href = " http : / / www. compadre. org / precollege / items / detail. cfm? id = 12568 " > wgbh educational foundation. teachers ' domain : why do snowflakes come in so many shapes and sizes?. boston : wgbh educational foundation, 2010. < / a > teachers ' domain : why do snowflakes come in so many shapes and sizes? ( wgbh educational foundation, boston, 2010 ), www document, ( http : / / www. teachersdomain. org / resource / lsps07. sci. phys. matter. lpsnowflakes / ). teachers ' domain : why do snowflakes come in so many shapes and sizes?. ( 2010 ). retrieved may 21, 2013, from wgbh educational foundation : http : / / www. teachersdomain. org / resource / lsps07. sci. phys. matter. lpsnowflakes / wgbh educational foundation. teachers ' domain : why do snowflakes come in so many shapes and sizes?. boston : wgbh educational foundation, 2010. http : / / www. teachersdomain. org / resource / lsps07. sci. phys. matter. lpsnowflakes / ( accessed 21 may 2013 ). teachers ' domain : why do snowflakes come in so many shapes and sizes?. boston : wgbh educational foundation, 2010. 21 may 2013 < http : / / www. teachersdomain. org / resource / lsps07. sci. phys. matter. lpsnowflakes / >. % t teachers ' domain : why do snowflakes come in so many shapes and sizes? % d 2010 % i wgbh educational foundation % c boston % u http : / / www. teachersdomain. org / resource / lsps07.


modern programming languages have little support for writing secure software, making it all too easy to write programs with exploitable vulnerabilities. in these lectures, we explore a general technique based on type qualifiers that allows programmers to write down, in their souce code, their intentions with respect to security. we will describe how to mechanically verify that annotated code adheres to the policy. we will discuss the theoretical foundations and practical implementation issues. as a particular example, we show how to use type qualifiers to find format - string vulnerabilities in widely - deployed c programs and to find other security vulnerabilites in the linux kernel. we will also look at alias analysis, another important program analysis problem, and show how a must - alias analysis system corresponds to a system for statically checking access control. this series of lectures will discuss the requirements, protocols, and components of network security software on the internet. topics will include secure tunnels, security for web services, privacy constraints, design features that create or address dos threats, and the use of programmable security tokens in network protocols. the primary emphasis will be the relationship between models and design, including topics like the quantification of dos threats, models for code security in programmable tokens, strategies for composition and interoperation, and practical strategies for formal analysis of network protocol designs and software. in these lectures, we will analyze the security infrastructure in current, main - stream programming systems and platforms such as the java virtual machine and common language runtime. we will explain how byte code verification collaborates with the class loader and security manager to provide a secure run - time environment. we will also use theoretical tools to determine what properties current security systems based on stack inspection have and provide concrete proposals for improving the infrastructure for next - generation programming languages and systems.


we consider a simple pure substance under hydrostatic conditions described by the following fundamental equation : where the extensive variables u, v and n are the internal energy, the volume, and the number of particles respectively, and the intensive variables t, p and are the temperature, the pressure and the chemical potential respectively. equation ( ) corresponds to the choice of the variables u, v and n as independent variables of the entropy s ( u, v, n ). these variables are precisely those which are fixed and determine the macrostate of the members of the microcanonical ensemble and consequently s is the relevant potential in this statistical ensemble. it is useful to define the following quantities :, and so that eq. ( ) can then be written in the dimensionless form : in general, for other thermodynamic systems with degrees of freedom, one will have : where are extensive variables, and the corresponding entropic conjugate variables. massieu - planck functions are entropic thermodynamic potentials defined as legendre transformations of the entropy. in the case of a pure substance, the following ( dimensionless ) potentials can be formally defined : the function was first introduced by massieu, and it is called massieu ' s potential. the function was introduced by planck and is called planck ' s. potential. given the extensivity of, and using euler ' s theorem for homogeneous functions, it is easy to see that. therefore the legendre transformation of all variables redefines the entropy, substituting eq. ( ) into the differentials of the potentials defined above one gets : from eq. ( ) one obtains : the above equations allow a re - derivation of all the standard thermodynamic equations in terms of, and. for instance, maxwell relations can be deduced, by imposing that the equations ( ) - ( ) are exact differentials ( equality of crossed derivatives ). moreover, eq. ( ) is the gibbs - duhem equation which states that the complete set of intensive variables of the system are not all independent. on the other hand, the extremal condition of leads us to deduce that, and are homogeneous at equilibrium.


at various points along the path toward productive nanosystems for molecular manufacturing it would be useful to be able to calculate the properties and reactions of assemblies of atoms of various sizes. within the domain of non - relativistic quantum mechanics, such information is supplied by the schrodinger equation, but this can only be solved analytically for the hydrogen atom and ions with only one electron. for larger atoms and molecules, numerical solutions require compromises between computational feasibility and accuracy. recent work from researchers at argonne national laboratory suggests that machine learning can be an efficient alternative to numerical computations. a hat tip to kurzweilai. net for pointing to this new scientist article by lisa grossman “ molecules from scratch without the fiendish physics “ : a suite of artificial intelligence algorithms may become the ultimate chemistry set. software can now quickly predict a property of molecules from their theoretical structure. similar advances should allow chemists to design new molecules on computers instead of by lengthy trial - and - error. our physical understanding of the macroscopic world is so good that everything from bridges to aircraft can be designed and tested on a computer. there ’ s no need to make every possible design to figure out which ones work. microscopic molecules are a different story. “ basically, we are still doing chemistry like thomas edison, ” says anatole von lilienfeld of argonne national laboratory in lemont, illinois. the chief enemy of computer - aided chemical design is the schrodinger equation. in theory, this mathematical beast can be solved to give the probability that electrons in an atom or molecule will be in certain positions, giving rise to chemical and physical properties. but because the equation increases in complexity as more electrons and protons are introduced, exact solutions only exist for the simplest systems : the hydrogen atom, composed of one electron and one proton, and the hydrogen molecule, which has two electrons and two protons. … the researchers developed a machine learning model to calculate the atomisation energy — the energy of all the bonds holding a molecule together and applied it to a database of 7165 small organic molecules of known structure and atomization energy and containing up to seven atoms of carbon, nitrogen, oxygen, or sulfur, plus the number of hydrogen atoms necessary to saturate the bonds. these molecules had atomization energies ranging from 800 to 2000 kcal / mol. the model was trained on a subset of 1000 compounds and then used to calculate the energies of the remaining molecules in the database. the results showed a mean error of only 9.


deoxidation is the removal of excess oxygen from molten metal. the procedure involves adding materials with a high affinity for oxygen, the oxides of which are either gaseous or readily form slags. the deoxidation of steel is usually performed by adding mn, si and al, or rarely by adding cr, v, ti, zr and b. the deoxidation of molten steel shows a paradox. by increasing the concentration of deoxidizer in the melt over some critical value reoxidation of steel takes place. a few examples of the reoxidation of steel by adding the usual deoxidizers ( si and al ) are examined in this article. deoxidation is the last stage in steelmaking. in the basic oxygen furnace ( bof ) and other similar steelmaking practices the steel bath as the time of tapping contains 400 to 800 ppm activity of oxygen. deoxidation is carried out during tapping by adding into the tap - ladle appropriate amounts of ferromanganese, ferrosilicon and / or aluminum or other special deoxidizers. if at the end of the blow the carbon content of the steel is below specifications, the metal is also recarburized in the ladle. however, large additions in the ladle are undesirable, because of the adverse effect on the temperature of the metal. eight typical conditions of commercial ingots, cast in identical bottle - top molds, in relation to the degree of suppression of gas evolution are shown schematically in figure 1. the dotted line indicates the height to which the steel originally was poured in each ingot mold. depending on the carbon content and particularly of the oxygen content, the ingot structures range from that of a fully killed or dead - killed ingot n°1 to that of a violently rimmed ingot n°8. included in the series are indicated in figure 1 i. e. killed steel n°1, semikilled steel n°2, capped steel n°5, and rimmed steel n°7. figure 1 : series of typical ingot structures rimmed steel usually is tapped without having made additions of deoxidizers to the steel in the furnace or only small additions to the molten steel in ladle, in order to have sufficient oxygen present to give the desired gas evolution by reacting in the mold with carbon. the exact procedures followed depend upon whether the steel has a carbon content in the higher ranges i. e. % c =


% ti | | 2. 8 x 10 - 6 | | > 5 % ti | | 1. 9 x 10 - 3 | | < 0. 10 v | | 8. 9 x 10 - 8 | | - 48060 / t + 18. 61 | | > 0. 3 % v | | 2. 9 x 10 - 6 | | - 43200 / t + 17. 52 in all cases, the oxygen and the alloying element in solution are in equilibrium with the appropriate gas, liquid or solid oxide phases at 1600°c, e. g. 1 atm co, pure b2o3, pure al2o3 etc. the curves for mn, si and c are from compiled data. the curves for cr, v, b, ti and al are based on the recent work done in this laboratory by fruehan using the oxygen galvanic cell previously described in measuring the equilibrium oxygen potentials. - activities are chosen such that amn ≡ % mn and ao ≡ % o when % m→o - square brackets [ ] denote component present in molten steel - temperature ( t ) is on the kelvin scale. deoxidation reactions can be described using the deoxidation equilibrium constant. the reaction when the alloying element ( m ) is added to the steel can be represented by : mxoy = xm + yo..... ( 1 ) the deoxidation constant assuming pure mxoy forms ( i. e. unit activity for mxoy ) is given by : k = ( hm ) x ( ho ) y..... ( 2 ) where hm and ho are the henrian activities defined such that activity of the components is equal to its weight percent at infinite dilution in iron. hi = fi ( wt. % i )..... ( 3 ) the activity coefficient fi can be corrected for alloying elements by use of the interaction parameter eji ( d log fi / d log wt % j ) = eji..... ( 4 ) table 2 shows the coefficients of interaction for the common elements of carbon and stainless steels at 1600°c. table 2 : the coefficients of interaction for the common elements of carbon and stainless steels at 1600°c | carbon steel 1600°c | stainless steel 1600°c for most low alloy steels encountered in ladle metallurgy the activity coefficient can be taken as unity and equation 2 reduces to : km = ( % m ) x ( % o ) y.


electricity and magnetism the dot product introduction to the vector dot product. the dot product use this menu to view and help create subtitles for this video in many different languages. you ' ll probably want to hide youtube ' s captions if using these subtitles. - let ' s learn a little bit about the dot product. - the dot product, frankly, out of the two ways of multiplying - vectors, i think is the easier one. - so what does the dot product do? - why don ' t i give you the definition, and then i ' ll give - you an intuition. - so if i have two vectors ; vector a dot vector b - - that ' s - how i draw my arrows. - i can draw my arrows like that. - that is equal to the magnitude of vector a times the - magnitude of vector b times cosine of the - angle between them. - now where does this come from? - this might seem a little arbitrary, but i think with a - visual explanation, it will make a little bit more sense. - so let me draw, arbitrarily, these two vectors. - so that is my vector a - - nice big and fat vector. - it ' s good for showing the point. - and let me draw vector b like that. - vector b. - and then let me draw the cosine, or let me, at least, - draw the angle between them. - this is theta. - so there ' s two ways of view this. - let me label them. - this is vector a. - i ' m trying to be color consistent. - this is vector b. - so there ' s two ways of viewing this product. - you could view it as vector a - - because multiplication is - associative, you could switch the order. - so this could also be written as, the magnitude of vector a - times cosine of theta, times - - and i ' ll do it in color - appropriate - - vector b. - and this times, this is the dot product. - i almost don ' t have to write it. - this is just regular multiplication, because these - are all scalar quantities. - when you see the dot between vectors, you ' re talking about - the vector dot product. - so if we were to just rearrange this expression this - way, what does it mean? - what is a cosine of theta? - let me


vector a. - it ' s just our basic calculus. - or another way you could view it, just multiply both sides - by the magnitude of vector a. - you get the projection of a onto b, which is just a fancy - way of saying, this side ; the part of a that goes in the - same direction as b - - is another way to say it - - is - equal to just multiplying both sides times the magnitude of a - is equal to the magnitude of a, cosine of theta. - which is exactly what we have up here. - and the definition of the dot product. - so another way of visualizing the dot product is, you could - replace this term with the magnitude of the projection of - a onto b - - which is just this - - times the - magnitude of b. - that ' s interesting. - all the dot product of two vectors is - - let ' s just take - one vector. - let ' s figure out how much of that vector - - what component - of it ' s magnitude - - goes in the same direction as the - other vector, and let ' s just multiply them. - and where is that useful? - well, think about it. - what about work? - when we learned work in physics? - work is force times distance. - but it ' s not just the total force - times the total distance. - it ' s the force going in the same - direction as the distance. - you should review the physics playlist if you ' re watching - this within the calculus playlist. let ' s say i have a - 10 newton object. - it ' s sitting on ice, so there ' s no friction. - we don ' t want to worry about fiction right now. - and let ' s say i pull on it. - let ' s say my force vector - - this is my force vector. - let ' s say my force vector is 100 newtons. - i ' m making the numbers up. - 100 newtons. - and let ' s say i slide it to the right, so my distance - vector is 10 meters parallel to the ground. - and the angle between them is equal to 60 degrees, which is - the same thing is pi over 3. - we ' ll stick to degrees. - it ' s a little bit more intuitive. - it ' s 60 degrees. - this distance right here is 10 meters. - so my question is,


hacking quantum cryptography just got harder with quantum encryption, in which a message gets encoded in bits represented by particles in different states, a secret message can remain secure even if the system is compromised by a malicious hacker. credit : margita | shutterstock vancouver, british columbia — no matter how complex they are, most secret codes turn out to be breakable. producing the ultimate secure code may require encoding a secret message inside the quantum relationship between atoms, scientists say. artur ekert, director of the center for quantum technologies at the national university of singapore, presented the new findings here at the annual meeting of the american association for the advancement of science. ekert, speaking saturday ( feb. 18 ), described how decoders can adjust for a compromised encryption device, as long as they know the degree of compromise. the subject of subatomic particles is a large step away from the use of papyrus, the ancient writing material employed in the first known cryptographic device. that device, called a scytale, was used in 400 b. c. by spartan military commanders to send coded messages to one another. the commanders would wrap strips of papyrus around a wooden baton and write the message across the strips so that it could be read only when the strips were wrapped around a baton of matching size. [ the coolest quantum particles explained ] later, the technique of substitution was developed, in which the entire alphabet would be shifted, say, three characters to the right, so than an " a " would be replaced by " d, " and " b " replaced by " e, " and so on. only someone who knew the substitution rule could read the message. julius caesar employed such a cipher scheme in the first century b. c. over time, ciphers became more and more complicated, so that they were harder and harder to crack. harder, but not impossible. " when you look at the history of cryptography, you come up with a system, and sooner or later someone else comes up with a way of breaking the system, " ekert said. " you may ask yourself : is it going to be like this forever? is there such a thing as the perfect cipher? " the perfect cipher the closest thing to a perfect cipher involves what ' s called a one - time pad. " you just write your message as a sequence of bits and you then add those bits to a key and obtain a cryptogram, " ekert said. " if you take the cryptogram and add it to the key, you


pad. " you just write your message as a sequence of bits and you then add those bits to a key and obtain a cryptogram, " ekert said. " if you take the cryptogram and add it to the key, you get plain text. in fact, one can prove that if the keys are random and as long as the messages, then the system offers perfect security. " in theory, it ' s a great solution, but in practice, it has been hard to achieve. [ 10 best encryption software products ] " if the keys are as long as the message, then you need a secure way to distribute the key, " ekert said. the nature of physics known as quantum mechanics seems to offer the best hope of knowing whether a key is secure. quantum mechanics says that certain properties of subatomic particles can ' t be measured without disturbing the particles and changing the outcome. in essence, a particle exists in a state of indecision until a measurement is made, forcing it to choose one state or another. thus, if someone made a measurement of the particle, it would irrevocably change the particle. if an encryption key were encoded in bits represented by particles in different states, it would be immediately obvious when a key was not secure because the measurement made to hack the key would have changed the key. this, of course, still depends on the ability of the two parties sending and receiving the message to be able to independently choose what to measure, using a truly random number generator — in other words, exercising free will — and using devices they trust. but what if a hacker were controlling one of the parties, or tampering with the encryption device? ekert and his colleagues showed that even in this case, if the messaging parties still have some free will, their code could remain secure as long as they know to what degree they are compromised. in other words, a random number generator that is not truly random can still be used to send an undecipherable secret message, as long as the sender knows how random it is and adjusts for that fact. " even if they are manipulated, as long as they are not stupid and have a little bit of free will, they can still do it, " ekert said. more from livescience. com


this mathematically oriented introduction to the theory of logic programming presents a systematic exposition of the resolution method for propositional, first - order, and horn - clause logics, together with an analysis of the semantic aspects of the method. it is through the inference rule of resolution that both proofs and computations can be manipulated on computers, and this book contains elegant versions and proofs of the fundamental theorems and lemmas in the proof theory of logic programming. advanced topics such as recursive complexity and negation as failure and its semantics are covered, and streamlined setups for sld - and sldnf - resolution are described. no other book treats this material in such detail and with such sophistication. doets provides a novel approach to resolution that is applied to the first - order case and the case of ( positive ) logic programs. in contrast to the usual approach, the concept of a resolvent is defined nonconstructively, without recourse to the concept of unification, allowing the soundness and completeness proofs to be carried out in a more economic way. other new material includes computability results dealing with analytical hierarchy, results on infinite derivations and an exposition on general logic programs using 3 - valued logic.


keynote address : research agenda and policy perspectives on agriculture for development the keynote address of the conference, by justin lin, the chief economist at the world bank, focuses on future research priorities and the process of implementing the policy objectives of the 2008 world development report, " agriculture for development. " justin lin is the chief economist of the world bank. this lesson plan should be used for grades 5 - 7 to help practice, learn, and implement the scientific method, using a self - directed study. try dutch! : dutch language taster interested in dutch? curious how dutch sounds? wondering how difficult or easy it is? perhaps you are thinking of studying dutch? then here is your opportunity to have a go at the language yourself and experience what it is like to learn dutch from scratch. you can work through the pack all by yourself. no knowledge of dutch is required. ucl grant museum of zoology eutherians image collection this is a set of images taken from a teaching resource created at university college london, in collaboration with their museum of zoology. they are primarily along the themes of phylogeny ( evolutionary history ) and functional anatomy. the images are hosted in the uk centre for bioscience ' s imagebank. from ideas to intellectual property ( materials ) this zipped file contains all of the materials that made up the " how to extract value from intellectual property pt 1 ". inside the file is a narrative, the full powerpoint slide and cc licence information for all the clip art and materials that have been used. there are audio files that also can be used under the creative commons. the relevant attribution and sources for the materials can be found in the. ppt of the lecture. nuclear and particle physics a third year course in nuclear and particle physics. could do with a few lhc updates. contains lecture notes, examples,... as well as the files used to create these resources. also has some movies of nuclear collective motion. discusses : 1 introduction 2 a history of particle physics 3 experimental tools 4 nuclear masses 5 nuclear models 6 some basic concepts of theoretical particle physics 7 the fundamental forces 8 symmetries and particle physics 9 symmetries of the theory of strong humbox : keywords / tags matches " oerprs " humbox : keywords / tags matches " oerprs " feed 1 introduction to microeconomics this is a module framework. it can be viewed online or downloaded as a zip file. as taught semester 1 2009 / 2010. there are no pre - requisites to taking


sep. 13, 2012 it ' s not a magic trick and it ' s not sleight of hand - - scientists really are using levitation to improve the drug development process, eventually yielding more effective pharmaceuticals with fewer side effects. scientists at the u. s. department of energy ' s ( doe ) argonne national laboratory have discovered a way to use sound waves to levitate individual droplets of solutions containing different pharmaceuticals. while the connection between levitation and drug development may not be immediately apparent, a special relationship emerges at the molecular level. at the molecular level, pharmaceutical structures fall into one of two categories : amorphous or crystalline. amorphous drugs typically are more efficiently taken up by the body than their crystalline cousins ; this is because amorphous drugs are both more highly soluble and have a higher bioavailability, suggesting that a lower dose can produce the desired effect. " one of the biggest challenges when it comes to drug development is in reducing the amount of the drug needed to attain the therapeutic benefit, whatever it is, " said argonne x - ray physicist chris benmore, who led the study. " most drugs on the market are crystalline - - they don ' t get fully absorbed by the body and thus we aren ' t getting the most efficient use out of them, " added yash vaishnav, argonne senior manager for intellectual property development and commercialization. getting pharmaceuticals from solution into an amorphous state, however, is no easy task. if the solution evaporates while it is in contact with part of a vessel, it is far more likely to solidify in its crystalline form. " it ' s almost as if these substances want to find a way to become crystalline, " benmore said. in order to avoid this problem, benmore needed to find a way to evaporate a solution without it touching anything. because liquids conform to the shape of their containers, this was a nearly impossible requirement - - so difficult, in fact, that benmore had to turn to an acoustic levitator, a piece of equipment originally developed for nasa to simulate microgravity conditions. levitation or " containerless processing " can form pristine samples that can be probed in situ with the high - energy x - ray beam at argonne ' s advanced photon source. " this allows amorphization of the drug to be studied while it is being processed, " said rick weber, who works on the project team at the synchrotron. the acoustic levitat


at argonne ' s advanced photon source. " this allows amorphization of the drug to be studied while it is being processed, " said rick weber, who works on the project team at the synchrotron. the acoustic levitator uses two small speakers to generate sound waves at frequencies slightly above the audible range - - roughly 22 kilohertz. when the top and bottom speakers are precisely aligned, they create two sets of sound waves that perfectly interfere with each other, setting up a phenomenon known as a standing wave. at certain points along a standing wave, known as nodes, there is no net transfer of energy at all. because the acoustic pressure from the sound waves is sufficient to cancel the effect of gravity, light objects are able to levitate when placed at the nodes. although only small quantities of a drug can currently be " amorphized " using this technique, it remains a powerful analytical tool for understanding the conditions that make for the best amorphous preparation, vaishnav explained. argonne researchers have already investigated more than a dozen different pharmaceuticals, and the laboratory ' s technology development & commercialization division is currently pursuing a patent for the method. technology development & commercialization is also interested in partnering with the pharmaceutical industry to develop the technology further as well as to license it for commercial development. after adapting the technology for drug research, the argonne scientists teamed up with professors stephen byrn and lynne taylor at the department of industrial and physical pharmacy at purdue university and jeffery yarger of the department of chemistry and biochemistry at arizona state university. the group is now working on identifying which drugs the levitation instrumentation will impact most strongly. other social bookmarking and sharing tools : 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.


american heritage® dictionary of the english language, fourth edition - n. a form or part that is folded or coiled. - n. one of the convex folds of the surface of the brain. century dictionary and cyclopedia - n. the act of rolling. or winding together, or of winding one part or thing on another ; the motion or process of winding in and out. - n. the state of being rolled upon itself, or rolled or wound together. - n. a turn or winding ; a fold ; a gyration ; an anfractuosity ; a whorl : as, the convolutions of a vine ; the convolutions of the intestines. - n. in anatomy, specifically, one of the gyri, gyres, or anfractuosities of the brain, especially of the cerebrum. see cuts under brain and corpus. - n. in mathematics, such a connection between the relations of any asyzygetic system that each is applied alternately in the aggregate of the remaining relations. - n. something that is folded or twisted. - n. any of the folds on the surface of the brain. - n. the shape of something rotating ; a vortex. - n. mathematics a form of moving average. - n. computing a function which maps a tuple of sequences into a sequence of tuples. gnu webster ' s 1913 - n. the act of rolling anything upon itself, or one thing upon another ; a winding motion. - n. the state of being rolled upon itself, or rolled or doubled together ; a tortuous or sinuous winding or fold, as of something rolled or folded upon itself. - n. ( anat. ) an irregular, tortuous folding of an organ or part. - n. a convex fold or elevation in the surface of the brain - n. the action of coiling or twisting or winding together - n. the shape of something rotating rapidly - from latin convolutus ( " to roll together " ), past participle of convolvere, from con - + volvere ( " to roll " ). ( wiktionary ) “ it was in 1861 that he announced his discovery of the seat of articulate speech in the left side of the frontal region of the brain, since known as the convolution of broca. ” “ it is of small size, and consists of a square - shaped convolution,


this winter i ’ m taking a course on urban education. our first topic : segregation and desegregation in schools. firstly, what do we mean by segregation? as a working definition, i ’ ll offer that segregation is the spatial pattern of people across some attribute. so we could talk about segregation by race, by income, or by favorite ice cream flavor. once we pick something to measure against, we find that every city is segregated according to this definition. what matters is in what way the segregation manifests and the consequences on the populace the pattern has. segregation patterns can be uniform, with all groups distributed more or less evenly within a region, or clustered. likewise, we could also calculate the extent to which subpopulations are isolated from each other — which also gives a rough estimation of how often members of one group is likely to run into someone outside of their group. i think when we talk about ‘ segregated ’ groups, we typically mean highly clustered populations that are isolated from the other groups in the city. i don ’ t think that clustered, isolated groups are necessarily bad on their own. i love visiting the north end and chinatown. because they ’ re both t - accessible, it ’ s easy for me to get there. ( though, both neighborhoods have had rough pasts. ) and harvard square is the nicest place i ’ ve ever lived. score one for segregation! moral judgments aside, self - selection can have a big influence on patterns of segregation, at least it can in models. the positive feedback loops reinforce small, individual choice to generate large - scale patterning. schelling ’ s model of segregation is a classic, good first example of what i mean. in this model individuals exhibit only a slight preference to have neighbors that are similar to them. the individuals in this model are not racist. ( or maybe they are. i don ’ t have a good functional definition of racism yet. ) when individuals find themselves in a neighborhood that is too unlike themselves, they move somewhere else at random, possibly to a neighborhood more dissimilar from themselves than the last. even with this mild, partially blind behavior, a totally segregated structure emerges. in more relaxed models that completely ignore race, even more realistic patterns of segregation form. in this class of model, individuals simply choose to live in the nicest area they can afford. as if by magic, isolated poor and rich neighborhoods form. depending on the details of the model, wealthy suburbs appear spontaneously. if we use socioeconomic status as a proxy