dyes and carbon tetrachloride. the majority of hazardous waste which the campus generates is characteristic hazardous waste. it is not included on any of the lists mentioned above but is considered hazardous because it exhibits one of the four characteristics mentioned below. empty containers ignitable - a liquid with a flash point less than 140 fahrenheit, an ignitable compressed gas or oxidizer, or other material that can cause fire through friction absorption of moisture or spontaneous chemical changes, common examples include used oil - based paint, used paint thinner, adhesives and mineral spirits. corrosive - a water containing liquid with a ph less than or equal to 2. 0 or greater than or equal to 12. 5, or a liquid that corrodes plain carbon steel at a rate greater than 6. 35 mm per year. examples include waste rust removers and waste battery acids. reactive - a waste that is normally unstable, readily undergoes violent changes without detonating, reacts violently with water, forms a potentially explosive mixture with water, or generates toxic gases or fumes when mixed with water or noncorrosive materials, is incapable of detonation or explosive reaction, or is a forbidden class a or class b explosive. toxic - a waste is tc hazardous if ( according to the toxicity characteristic leaching procedure ) it exceeds the regulatory levels for any of the eight metals, six pesticides or 25 organic chemicals listed in the appendix under toxic substances. this list includes metals like chromium, lead, mercury, silver and organic chemicals like benzene, chloroform, methyl ethyl ketone, and butadiene. if you have a waste which is listed in one of the tables or exhibits one of the characteristics mentioned above, do not place it in a dumpster for landfill. hazardous waste must be shipped with the campus hazardous waste shipment. contact the university safety manager, ext. 2273, for proper disposal. empty containers that formerly contained hazardous waste can be put in the dumpster for landfill. a container is empty if all waste has been removed by the methods commonly used to empty that type of container ( e. g. pouring or pumping ). in addition, the container must have less than one inch of waste remaining, or 3 % or less by weight of waste remaining if the container holds 110 gallons or less or. 3 % or less by weight or waste remaining if the container holds more than 110 gallons. containers that held acutely hazardous waste ( " p " wastes ) must be triple


american heritage® dictionary of the english language, fourth edition - v. to reduce the volume or compass of. - v. to make more concise ; abridge or shorten. - v. physics to cause ( a gas or vapor ) to change to a liquid. - v. physics to remove water from ( milk, for example ). - v. to become more compact. - v. to undergo condensation. century dictionary and cyclopedia - to make more dense or compact ; reduce the volume or compass of ; bring into closer union of parts ; consolidate ; compress : used both literally and figuratively. - in chem. and physical, to reduce to another and denser form, as a gas or vapor to the condition of a liquid or of a solid, as by pressure or abstraction of heat. - synonyms to concentrate, contract, crowd together, inspissate ; to abridge, shorten, reduce, epitomize, abbreviate ; to solidify. - to become denser or more compact, as the particles of a body ; become liquid or solid, as a gas or vapor. - close in texture or composition ; compact ; dense. - v. transitive to decrease size or volume by concentration toward the essence. - v. intransitive, chemistry to transform from a gaseous state into a liquid state via condensation. - adj. archaic condensed ; compact ; dense. gnu webster ' s 1913 - v. to make more close, compact, or dense ; to compress or concentrate into a smaller compass ; to consolidate ; to abridge ; to epitomize. - v. ( chem. & physics ) to reduce into another and denser form, as by cold or pressure. - v. to become more compact ; to be reduced into a denser form. - v. to combine or unite ( as two chemical substances ) with or without separation of some unimportant side products. - v. to undergo polymerization. - adj. rare condensed ; compact ; dense. - v. undergo condensation ; change from a gaseous to a liquid state and fall in drops - v. remove water from - v. cause a gas or vapor to change into a liquid - v. make more concise - v. become more compact or concentrated - v. develop due to condensation - v. compress or concentrate - from latin condensare. ( wiktionary ) - middle english


work is the transfer of energy. in physics we say that work is done on an object when you transfer energy to that object. for introductory thinking, this is the best definition of work. if you put energy into an object, then you do work on that object. if a first object is the agent that gives energy to a second object, then the first object does work on the second object. the energy goes from the first object into the second object. at first we will say that if an object is standing still, and you get it moving, then you have put energy into that object. for example, a golfer uses a club and gets a stationary golf ball moving when he or she hits the ball. the club does work on the golf ball as it strikes the ball. energy leaves the club and enters the ball. this is a transfer of energy. thus, we say that the club did work on the ball. and, before the ball was struck, the golfer did work on the club. the club was initially standing still, and the golfer got it moving when he or she swung the club. so, the golfer does work on the club, transferring energy into the club, making it move. the club does work on the ball, transferring energy into the ball, getting it moving. in almost all cases considered when studying mechanical forms of energy, when work is done on an object a force is applied to the object, and the object is displaced while this force is acting upon it. that is, the object moves as a result of a force being placed on it. in the previous golf example the club places a force on the ball, and this force acts on the ball over the short distance through which the club and the ball are in contact as the ball is being hit. energy is transferred as the force acts over this displacement. the amount of work is calculated by multiplying the force times the displacement. that formula looks like this : at first we will consider only forces that are aimed in the same direction as the displacement. for example, we will imagine an object being pushed horizontally to the right, and the object will be moving horizontally to the right as a result of this applied force. below is an animation that shows just that. the force vector is drawn in blue. it is pushing the object to the right. this force is applied over a displacement. the displacement vector is shown in red. the object starts out standing still. while the force is acting on the object the object picks up speed, that is, it accelerate


to study particle physics, you have a strong scientific and mathematical background. but you also need a good imagination, because you ’ ll be spending a lot of time studying things that you cannot see. and that ’ s okay with dr. derek harnett, a physicist who will be the second speaker in the 2011 / 12 university lecture series at ufv. harnett will speak on wed, nov 16, at 4 pm in room b121 on the abbotsford campus. harnett will speak about exotic bound states of the strong nuclear force. the strong nuclear force is one of the four basic forces in nature ( the others being gravity, the electromagnetic force, and the weak nuclear force ). it is what scientists believe causes quarks to stick together to make protons and neutrons. the science of physics includes a perpetual quest to further isolate the tiny subatomic building blocks of matter. objects are made of molecules, which are comprised of atoms. atoms can be broken down into protons, neutrons, and electrons. protons and neutrons are made of smaller ‘ bits ’ of matter called quarks. “ particle physics contends that there must be another force, stronger than the electric force, that provides a greater attraction than repulsion, ” harnett says. “ they ’ ve labeled it, rather unimaginatively, the strong nuclear force. “ we now know that forces are due to particle exchange. the particles interact by sending streams of mediating particles back and forth, exchanging energy. the bundles of energy that flow between quarks are called gluons. ” “ people are building machines now to try to see these particles, ” harnett notes. “ such exotic particles are predicted by theory but have yet to be conclusively identified in experiment. the big question is : do they exist and haven ’ t been found yet, or is the theory incomplete? my inclination is that the theory — formally called quantum chromodynamics — is fine. ” “ but when we ask why care about theoretical physics, we need to remember that before you can take a force and harness it for the purpose of engineering, you need a really deep understanding of it. electromagnetism was pure scientific theory to begin with. some guys just wanted to know why magnets stuck together. now we have it powering wireless devices all over the world. we probably won ’ t reap the benefits of nuclear physics research in the foreseeable future, but it is still worthwhile and fascinating


picking out the head of a screw at a distance of 300 km ( 190 mi ). notable 1990s results included the mark iii measuring diameters of 100 stars and many accurate stellar positions, coast and npoi producing many very high resolution images, and isi measuring stars in the mid - infrared for the first time. additional results include direct measurements of the sizes of and distances to cepheid variable stars, and young stellar objects. high on the chajnantor plateau in the chilean andes, the european southern observatory ( eso ), together with its international partners, is building alma, which will study light from some of the coldest objects in the universe. alma will be a single telescope of a new design, composed initially of 66 high - precision antennas and operating at wavelengths of 0. 3 to 9. 6 mm. its main 12 - metre array will have fifty antennas, 12 metres in diameter, acting together as a single telescope – an interferometer. an additional compact array of four 12 - metre and twelve 7 - metre antennas will complement this. the antennas can be spread across the desert plateau over distances from 150 metres to 16 kilometres, which will give alma a powerful variable " zoom ". it will be able to probe the universe at millimetre and submillimetre wavelengths with unprecedented sensitivity and resolution, with a vision up to ten times sharper than the hubble space telescope, and complementing images made with the vlt interferometer. optical interferometers are mostly seen by astronomers as very specialized instruments, capable of a very limited range of observations. it is often said that an interferometer achieves the effect of a telescope the size of the distance between the apertures ; this is only true in the limited sense of angular resolution. the amount of light gathered — and hence the dimmest object that can be seen — depends on the real aperture size, so an interferometer would offer little improvement ( the thinned - array curse ). the combined effects of limited aperture area and atmospheric turbulence generally limit interferometers to observations of comparatively bright stars and active galactic nuclei. however, they have proven useful for making very high precision measurements of simple stellar parameters such as size and position ( astrometry ), for imaging the nearest giant stars and probing the cores of nearby active galaxies. for details of individual instruments, see the list of astronomical interferometers at visible and infrared wavelengths. | a simple two - element optical interferometer. light from two small telescopes ( shown as lenses ) is


the cores of nearby active galaxies. for details of individual instruments, see the list of astronomical interferometers at visible and infrared wavelengths. | a simple two - element optical interferometer. light from two small telescopes ( shown as lenses ) is combined using beam splitters at detectors 1, 2, 3 and 4. the elements creating a 1 / 4 - wave delay in the light allow the phase and amplitude of the interference visibility to be measured, which give information about the shape of the light source. | | a single large telescope with an aperture mask over it ( labelled mask ), only allowing light through two small holes. the optical paths to detectors 1, 2, 3 and 4 are the same as in the left - hand figure, so this setup will give identical results. by moving the holes in the aperture mask and taking repeated measurements, images can be created using aperture synthesis which would have the same quality as would have been given by the right - hand telescope without the aperture mask. in an analogous way, the same image quality can be achieved by moving the small telescopes around in the left - hand figure — this is the basis of aperture synthesis, using widely separated small telescopes to simulate a giant telescope. | at radio wavelengths, interferometers such as the very large array and merlin have been in operation for many years. the distances between telescopes are typically 10 – 100 km ( 6. 2 – 62 mi ), although arrays with much longer baselines utilize the techniques of very long baseline interferometry. in the ( sub ) - millimetre, existing arrays include the submillimeter array and the iram plateau de bure facility. the atacama large millimeter array is under construction and expected to be finished by the end of 2012. max tegmark and matias zaldarriaga have proposed the fast fourier transform telescope which would rely on extensive computer power rather than standard lenses and mirrors. if moore ' s law continues, such designs may become practical and cheap in a few years. labeyrie ' s hypertelescope antoine labeyrie has proposed the idea of an astronomical interferometer where the individual telescopes seen as parts of a fractionated spacecraft or a satellite constellation are positioned in a spherical arrangement ( requiring the individual telescopes to be positioned to a fraction of a wavelength ). this geometry reduces the amount of pathlength compensation required in re - pointing the interferometer array ( in fact a mertz corrector can be used rather than delay lines ), but otherwise is little different


( help ) ; more than one of - " new hardware to take interferometry to the next level ". eso. retrieved 3 april 2013. - j. d. monnier, optical interferometry in astronomy, reports on progress in physics, 66, 789 - 857, 2003 iop. ( download pdf file ) - m. ryle & d. vonberg, 1946 solar radiation on 175mc / s, nature 158 pp 339 - govert schilling, new scientist, 23 february 2006 the hypertelescope : a zoom with a view - rouan d., pelat d. ( 2008 ). " the achromatic chessboard, a new concept of a phase shifter for nulling interferometry ". astronomy and astrophysics 484 ( 2 ) : 581 – 9. arxiv : 0802. 3334. bibcode : 2008a & a... 484.. 581r. doi : 10. 1051 / 0004 - 6361 : 20078712. - le coroller, h. ; dejonghe, j. ; arpesella, c. ; vernet, d. ; labeyrie, a. ( 2004 ). " tests with a carlina - type hypertelescope prototype ". astronomy and astrophysics 426 ( 2 ) : 721 – 728. bibcode : 2004a & a... 426.. 721l. doi : 10. 1051 / 0004 - 6361 : 20041088. retrieved 2009 - 05 - 23 - berger, j. p. ; haguenauer, p. ; kern, p. ; perraut, k. ; malbet, f. ; schanen, i. ; severi, m. ; millan,. et al. ( 2001 ). " integrated optics for astronomical interferometry " ( w ). astronomy and astrophysics 376 ( 03 ) : l31 – 34. bibcode : 2001a & a... 376l.. 31b. doi : 10. 1051 / 0004 - 6361 : 20011035. retrieved 2009 - 05 - 23 further reading - how to combine the light from multiple telescopes for astrometric measurements - at npoi... why an optical interferometer? - remote sensing the potential and limits of astronomical interferometry


using conceptmapper to trace the evolution of taxonomic perspectives nico franz, email @ example. com, xianhua liu, firstname. lastname @ example. org, robert peet, email @ example. com, and laura downey, firstname. lastname @ example. org. ( 1 ) university of puerto rico - mayaguez, department of biology, po box 9012, mayaguez, pr, ( 2 ) curriculum in ecology, university of north carolina, chapel hill, nc, ( 3 ) lter network office, university of new mexico, albuquerque, nm taxonomic perspectives evolve over time, as the definitions for taxonomic names become partially redefined in light of new observations and character interpretations. many taxonomic redefinitions require concomitant adjustments in naming, yet other changes in taxonomic perspective, such as the shifting of a non - type genus from one tribe to another, are not translated into nomenclatural changes. the need for finer semantic resolution arises in various situations, including the integration of data in large - scale, long - term biodiversity studies and the development and periodical updating of taxonomic databases. taxonomic concepts, i. e. the meanings of names as they are specified in a particular source ( example : diaprepes abbreviatus [ linnaeus 1758 ] sec. pierce 1916 ), offer such resolution by allowing experts to use a precise ontology - like vocabulary to describe differences in name definitions between different taxonomic treatments. this presentation introduces conceptmapper, a software tool that assists taxonomists in the process of importing, visualizing, and correlating the meanings of taxonomic names in two separate classifications. the tool is built upon an xml schema ( see http : / / tdwg. napier. ac. uk / ) that manages scientific names, concept references, character and specimen circumscriptions, hierarchical parent - child relationships within one classification, and concept relationship assertions among two classifications. several real - life examples will show that conceptmapper is valuable to anyone who intends to understand the evolution of taxonomic names and their meanings in a purely systematic or applied biological context. species 1 : coleoptera curculionidae diaprepesabbreviatus ( citrus root weevil )


occur within a given space. space can also be described for its circulatory function or its ability to direct or enhance movement from area to area. the function of space can also be symbolic or may be used to make a visible statement about its use. and finally, space can function psychologically to offer optimum satisfaction or to simply be pleasing. the organization of content within a multimedia product may be enhanced through an approach to the digital environment that actively anticipates the function of the space occupied by the structure. from this perspective, the multimedia designer must anticipate the purpose of the content and the level of interaction that is necessary. the circulatory function of multimedia includes the ease with which the user can move and the visual guideposts that clarify the access routes. psychologically, a well designed multimedia experience leaves the user anticipating a return trip. the design produced by the architect influences the user ' s movement through space on many levels. the architect manipulates physical space which is bounded by walls, floor, and ceiling ; perceptual space and the sense of scale, perspective and distance that is seen by the viewer ; conceptual space that is part of memory and includes the mental maps that we carry around in our heads ; and finally, behavioral space which includes the way we actually move through and use an environment. the experience of manipulating space to create an environment through which others move is a fundamental concern for the multimedia designer. the environment is constructed of bits of information and is thus binary rather than physical. nonetheless, multimedia is space that we enter. if it is space on the internet, it is open and vast. if it is space on a portable storage device such as a cd - rom it is limited in scale but may be open in structure. the structure of the space is perceptual as opposed to the bricks and mortar of a physical structure. and yet, the experience of moving through a constructed environment is similar. mitchell argues that the structure of space on the internet has many of the symbolic and social characteristics of physical space but that the restrictions of architectural form can be overcome. spatial cities, he says, condense human activity to promote interaction but there is also an element of control introduced as access is organized. districts and neighborhoods are created to define space. for the inhabitants, crossing a threshold and entering a defined place d as an owner, guest, visitor, tourist, trespasser, intruder, or invader d is a symbolically, socially, and legally freighted act. there is always a big


the inhabitants, crossing a threshold and entering a defined place d as an owner, guest, visitor, tourist, trespasser, intruder, or invader d is a symbolically, socially, and legally freighted act. there is always a big difference between being a local and being an alien, being on your own turf and being on somebody else ' s, enjoying your privacy and appearing in public, feeling at home and knowing that you are out of place. so it is on the net, as well, but the game gets some new rules ; structures of access and exclusion are reconstrued in entirely nonarchitectural terms ( if we continue to define architecture as materially constructed form ), and you enter and exit places not by physical travel, but by simply establishing and breaking logical links. the architecture of multimedia space is not simply materially constructed form, although there are comparisons that can be made. rather, multimedia space is formally organized by the designer to allow movement through and within and between sections. the structure is most effectively created as a format for guiding movement rather than a form for controlling movement. movement is no longer bounded by the structure, rather it is guided. the ability to link from one section to another or to simply enter or exit a structure at any point becomes equivalent to walking through walls for the user. the design of a building or structure relies on the thoughtful consideration of human behavior. ultimately, a building is constructed for human use and thus movement through it, around it, and within it is of primary importance. the architect can create an environment that employs space in a directional way. for example, a gothic cathedral in which the emphatic axis directs movement toward a single focus d the altar. the architect may also elect to create an environment of non - directional space in which there is no single or obvious path through a building. rather, there are a variety of paths to choose from, each offering a unique relationship to the space created. the designer of multimedia must be similarly concerned with the user ' s movement through the material. in a multimedia environment there are multiple windows, doors, and hallways through content. the designer ' s challenge is to use directional and non - directional space to create multiple paths through a coherent, navigable garden of content rather than a labyrinth of dark, empty passageways and blind alleys. physical space. the constraints of technology allow limited influences on the part of the designer over physical space, which might be conceived of as the cd, the user ' s computer, or the network


labyrinth of dark, empty passageways and blind alleys. physical space. the constraints of technology allow limited influences on the part of the designer over physical space, which might be conceived of as the cd, the user ' s computer, or the network. physical space may also include access speed, storage limitations and the size of the digital presentation. these technology limitations are generally unavoidable and require that the designer simply make intelligent decisions that don ' t impede user access. in fact, the multimedia designer has the greatest influence over the realms of perceptual, behavioral and conceptual space. perceptual space. in the design of multimedia, perceptual space includes the elements visible on the user ' s screen and the environment that is created through their arrangement. the choice and arrangement of visual elements such as type, color, pattern, and image as well as the designer ' s use of sound, movement and time are important elements in multimedia design. the designer has control over the assembly of these elements and is charged with creating a perceptual space that is articulate and that adds to the communication goals of the presentation. if there is a sense of depth or perspective visible or if the passage of time is evident in the presentation, it is perceptual space that has been influenced by the designer. three - dimensional space is described as being boundless or limitless in all directions. perception of three - dimensional space is influenced by our ability to perceive depth and volume. the physiological properties of binocular vision, seeing with two eyes, gives us an ability to discriminate between the relative depths or forms within a three - dimensional visual field. this allows us to imagine distance and to gauge scale, shape and size. our understanding of three - dimensional space is also psychological because perception is a function of our ability to comprehend and assimilate what we are seeing. h. l. f. helmoltz developed cue theory which suggests that before the mind can know and interpret sensory information, it must participate in sensory events that form the basis for interpretation. in other words, once spatial cues are learned through experience, our perception of space becomes relatively simple and our response to it is automatic. cumulative sensory experience builds a foundation from which we perceive. our perception of space in multimedia is both a physiological function of vision and a learned phenomenon that is all the more complex because the digital data that makes up the multimedia product has no real volume or scale. it is the orientation, organization and design of content that can be approached


coating. each composite has unique properties and characteristics that suit it to different applications. most materials presented have a minimum of stretch and shrinkage in a wide range of temperature and humidity conditions, and coatings prevent mildew, staining, and streaking. choice of a material calls for understanding of its light reflectivity and light transmission. reflectivity is the amount of light the surface of the material reflects. transmission is the amount of light that penetrates the material. most fabrics allow some amount of light transmission, but some materials come with a blackout scrim between layers and allow no light to penetrate, so light and heat from the sun can be controlled. all the materials come in some shade of white ; some are also available in a limited range of colors, depending on supply and demand. the proper selection of membrane material will be based on the proposed size, form, function, and desired longevity of the structure, and the economics of the project. membranes can be fabricated in a number of ways based on the material chosen and the orientation of the seams. all aspects of a fabric structure should be derived from the same computer model or full - scale mockup. computer - generated patterns are the most widely accepted template for fabrication. smaller structures, such as awnings, are patterned directly off a full - scale mockup. seams determine the appearance of joined panels. the seams can be sewn, glued, electronically welded, or heat - sealed. seam styles can be parallel or radial to a mast. butt seams are joints produced by placing two adjacent pieces directly beside one another and covering the joint with a strip of material. lap seams are joints made by overlapping the edges of the material. reinforcements — multiple layers of material applied to specific areas of a membrane to strengthen it where concentrated tension loads exist — are also a part of the fabrication process and differ from project to project. the book is available for purchase at amazon. com. editor ' s note : this is an excerpt from fabric architecture : creative resources for shade, signage, and shelter by samuel j. armijos. copyright 2008 by samuel j. armijos, with permission of the publisher, w. w. norton & company, inc.


find information on common issues. ask questions and find answers from other users. suggest a new site feature or improvement. check on status of your tickets. progress in technology has brought microelectronics to the nanoscale, but nanoelectronics is not yet a well - defined engineering discipline with a coherent, experimentally verified, theoretical framework. the ncn has a vision for a new, ' bottom - up ' approach to electronics, which involves : understanding electronic conduction at the atomistic level ; formulating new simulation techniques ; developing a new generation of software tools ; and bringing this new understanding and perspective into the classroom. we address problems in atomistic phenomena, quantum transport, percolative transport in inhomogeneous media, reliability, and the connection of nanoelectronics to new problems such as biology, medicine, and energy. we work closely with experimentalists to understand nanoscale phenomena and to explore new device concepts. in the course of this work, we produce open source software tools and educational resources that we share with the community through the nanohub. this page is a starting point for nanohub users interested in nanoelectronics. it lists key resources developed by the ncn nanoelectronics team. the nanohub contains many more resources for nanoelectronics, and they can be located with the nanohub search function. to find all nanoelectronics resources, search for ' nanoelectronics. ' to find those contributed by the ncn nanoelectronics team, search for ' ncnnanoelectronics. ' more information on nanoelectronics can be found here. ncn nanoelectronics : research seminars ranking is calculated from a formula comprised of user reviews and usage data. learn more › 28 nov 2007 | series many research seminars are available on the nanohub. listed below are a few that discuss new device possiblities. ncn nanoelectronics : courses ncn nanoelectronics : simulation tools for education many simulation tools are available on the nanohub. the tools have been well - tested and here include supporting materials so that they can be effectively used for education or intelligently used for … ncn nanoelectronics : simulation tools for research ece 495n teaching materials : homeworks and exams ( fall 2007 ) 29 oct 2007 | series | contributor ( s ) : supriyo datta, saptarshi das homework assignments and


. " the key idea here, " tao explains, " is to convert an optical signal into local electrochemical current. " this is accomplished thanks to a phenomenon known as surface plasmon resonance. in an electrode — a metal conductor through which electric current is passed — electrons move freely and oscillate in a wavelike fashion called a plasmon. shining light on the surface plasmon causes the electrons to absorb energy and enter an excited state. tao notes that the plasmon is exquisitely sensitive to any changes occurring near the electrode ' s surface. if, for example, an electrochemical reaction involving oxidation or reduction takes place ( where electrons are lost or gained, respectively ), the plasmon registers this change as a reflection of light ( electrochemical current can be inferred from the changes in optical signals detected ). the technique allows for the resolution of trace chemicals down to a small fraction of a micron in diameter. the tnt experiments were carried out by first depositing a fingerprint on the surface of an electrode. the raised ridges of the fingerprint formed a delicate layer of protein that blocked the flow of electrochemical current, whereas the grooves allowed current to flow, providing the contrast to reveal the fingerprint in vivid relief when an electrical potential was applied. next, the applied potential was lowered to correspond to the specific reduction potential of tnt, at which point spots of the explosive particles appeared, providing both visual and chemical confirmation. remarkably, the technique could successfully detect the grains of tnt, even if they were mixed with other species of particles, including traces of dust, airborn particulate matter or wax. provided by arizona state university " new imaging technology brings trace chemicals into focus ( w / video ). " march 11th, 2010. http : / / phys. org / news187537969. html


structure in locations where the paths diverge most. the cross - correlation method produces travel - time residuals, which correspond to isolated anomalous velocities. spectral division yields a differential attenuation ( or dampening ) measurement ( dt * ). d " attenuation : the lowermost mantle, called d ", is a region of extreme heterogeneity on lateral scales from 100s to 1000s of kilometers. the core - mantle boundary is a chemical, thermal, and dynamic boundary layer between the iron core and the silicate mantle. consequently, measureable anamalous structures occur. for example, beneath central america, i measured a ~ 250 km wide velocity and quality factor anomaly which may be characterized as thermal in nature [ fisher et al., 2003 ]. radial quality factor : ( qlm9 ) over 30, 000 differential scs - s attenuation measurements were used to calculate the first radial quality factor model with high sensitivity in the lower mantle. the structure is unique, and shows that the earth is more anelastic with greater radius. the model shows that attenuation is high just above the core - mantle - boundary, where high temperatures ( due to heating from the core ) likely increase the anelasticity. [ lawrence and wysession., 2005a ]. global quality factor : ( vqm3da ) using over 70, 000 differential measurements we invert for the 3d quality factor structure of the earth. by analyzing both velocity and quality factor on the same scale, we can more easily understand the source of the heterogeneity. quality factor is highly dependent upon temperature and water content, so observation of large anomalies indicates one or the other. depending on how, velocity changes, it is possible to infer which one [ lawrence and wysession., 2006b ]. transition zone topography : seismic interfaces at about 410 and 660 kilometers depth are known to have significant topography [ flanagan and shearer, 1998 ]. however, previous evidence lead scientists to believe that different measurement techniques ( sds underside reflections and pds - p - to - s converted waves ) resulted in different estimates of global topography. we demonstrated that the two techniques do actually yield the same average and laterally variations in transition zone thickness [ lawrence and shearer., 2005 ]. north american structure : seismic attenuation and travel times are useful in - situe measurements of the mantle. using them together we can delineate difference between thermal and water concentration anoma


where did this weird theory come from? the inspiration for this theory came from stephen hawking ' s work on black hole entropy. entropy is the energy in a system that is available to do work. according to the second law of thermodynamics, the entropy of any closed system always increases or stays the same, and in many ways entropy can be described as the state of disorder in a system. another law in physics states that all physical laws should work the same everywhere in the universe. black holes, like the one shown below, present a big problem because they decrease entropy, and thus violate the second law of thermodynamics. ( wikipedia copyright user : alain r ) they reduce the entropy of the universe because the information encoded in objects that are sucked in is irretrievably lost. what ' s just as strange about black hole entropy is the maximum possible entropy in any region of a black hole scales with its radius squared not cubed, as if a black hole were a flat two - dimensional object. this means that all the information about all the objects that have ever fallen into a black hole somehow seems to be confined to the spherical surface of the event horizon. the event horizon is like the outer shell of a black hole. it is the point of no return, where even light itself cannot escape, and no one knows what lies within this shell. current theory tells us that all the mass of the original collapsed star and all the objects that have been swallowed since are reduced to a radius of zero at a central point inside the horizon, called a singularity. the holographic principle solves two closely related important problems with black hole entropy. the first problem is that black holes decrease entropy, as described above. second, they violate the law of conservation of information. this law, a more specific interpretation of the second law of thermodynamics, is most often described in a quantum sense. when an atom, for example, falls into a black hole, all of its information is lost. for an atom, that means its wave function, according to quantum mechanics, is gone from the universe. this loss violates an important principle in science - that information is conserved in the quantum sense. hawking showed us that black holes slowly radiate their energy away, they slowly evaporate in other words. according to the no - hair theorem in physics, this too is a problem. hawking radiation should be completely independent of the material going into a black hole. it should be a mixed ( think


away, they slowly evaporate in other words. according to the no - hair theorem in physics, this too is a problem. hawking radiation should be completely independent of the material going into a black hole. it should be a mixed ( think of it as generic ) quantum state. any particular initial quantum state of the material going into a black hole is therefore lost, and according to the law of information conservation, it can ' t be. the problem of information loss can also be described by something called the entangled pure state situation. this is how it works : let ' s say a photon has just spontaneously annihilated in space ( they do this all time according to quantum theory ). when it does so, an electron and a positron are spontaneously created. these two particles should quickly annihilate each other and release a new photon. but what if one particle is sucked into a black hole while the other one escapes? half the information of the photon ( called a partial trace ) is lost from a closed physical system ( the universe ). this also violates the second law of thermodynamics on a quantum level. from black hole riddles to holograms the information problem led to a huge battle between physicists, with hawking and kip thorn on one side insisting that quantum information must be lost, and leonard susskind and gerard t ' hooft on the other side, insisting that that is impossible. eventually, t ' hooft proposed a holographic theory as a solution to the problem and susskind provided a string theory interpretation of that solution. hawking, recognizing the problem of information loss, suggested that quantum fluctuations on the event horizon could theoretically allow all information to escape from a black hole. as long as information comes back out, the information paradox is solved. from this solution they arrived at the idea of information being contained on the event horizon of a black hole, contained in a two - dimensional space in order words, and that is the kernel at the center of the holographic principle, introduced here in this 3 - minute video : ( from michael coulson on vimeo ) what is the holographic principle? a hologram is a three - dimensional image confined in two dimensions. below is a mouse hologram for example. two photos are taken from different views. what ' s really interesting about thinking of the universe as a holographic projection is that it offers a possible description of quantum gravity, something that physicists have been seeking for decades.


hologram for example. two photos are taken from different views. what ' s really interesting about thinking of the universe as a holographic projection is that it offers a possible description of quantum gravity, something that physicists have been seeking for decades. string theory allows us a lower dimensional description of the universe, in which gravity emerges from it in a holographic way. this could account for why physicists haven ' t been able to find a force - carrier particle for gravity. the other three fundamental forces each have a gauge boson, a virtual particle that mediates a fundamental force. it also offers an explanation for why gravitational force is so much weaker than the other three forces as well. it is so weak, in fact, that it can be completely omitted from quantum equations. quantum mechanics describes the tiny subatomic world very well, and relativity describes the behaviours of massive objects in the vastness of space. the holographic principle could be the bridge between quantum mechanics and relativity that physicists have been searching for in their quest to find a single unified theory that can describe both the very small and the very big. string theory attempts to describe gravity as an emergent property of tiny fundamental vibrating strings. it doesn ' t attempt to describe gravity in terms of a force - mediating particle. instead, gravity is an illusion. string ( or strings as there is a whole set of these theories right now ) theory is based on an elegant set of mathematical formulae but there are many physical phenomena it cannot describe and there is no way to test it, so far. gravity, as an emergent holographic illusion, could bridge two competing ( and as of now mutually exclusive ) theories of how the universe works : black holes present a riddle to physicists because they require both a relativistic and a quantum description in order to understand them, and the holographic principle offers a potential way to describe them in which both quantum mechanics and relativity can be satisfied. physicist juan maldacena came up with a mathematical description of spacetime, called anti de sitter space, which describes the holographic universe. to us, the universe seems infinite yet we can deduce that it has some kind of boundary that has been expanding ever since the big bang. his mathematical metric solves this apparent anomaly. he used a three - dimensional analogue of what is called the hyperbolic plane, the boundary or surface of our universe. this plane is two - dimensional but it is wildly twisted ( and impossible to visualize ).


metric solves this apparent anomaly. he used a three - dimensional analogue of what is called the hyperbolic plane, the boundary or surface of our universe. this plane is two - dimensional but it is wildly twisted ( and impossible to visualize ). we, living within this bounded surface, don ' t notice the twisting. it is sort of like the distortion you see when looking at a global map, a 2 - d representation of a 3 - d world. his 3 - d analogue of this plane coupled with a fourth dimension, time, gives us a model holographic universe. string theory, describing the interior of the universe, has a sort of 2 - d shadow on the inner boundary of it. every fundamental particle has a 2 - d counterpart on that boundary. using this theory, you can describe any object in a gravitational field, whether it ' s a subatomic particle or a massive neutron star. you could describe a black hole. try this 83 - minute video from the 2010 world science festival called " black holes and holographic worlds, " where the world ' s best physicists describe this topic for nonscientists : as you can see, it has been very tempting to expand the holographic idea to the universe as a whole. in this sense, the universe is a two - dimensional information structure " painted on " the cosmological horizon, the edge of space analogous to the event horizon of a black hole. it even provides a new conceptualization of entropy - as the surface of the universe expands, more information can be stored on its 2 - d surface and the entropy of the universe increases as a result. according to this theory, our familiar three dimensions of space only work at the macroscopic scale and at low energies. when we look at very high - energy events or at the subatomic scale, or both simultaneously in the case of black holes, the underlying reality of a 2 - dimensional space seems to become apparent. the event horizon of a black hole is, therefore, a peek at this inner reality of the universe. leonard susskind describes the holographic principle in his own words in this 13 - minute interview : in order for this theory to work, there must be a limit on information density. entropy can be described as degrees of freedom in a system of matter and / or energy. there is an upper limit to the density of information that can be packed into a given volume that can be translated to two spatial dimensions. as you subdivide matter into its atoms and


of freedom in a system of matter and / or energy. there is an upper limit to the density of information that can be packed into a given volume that can be translated to two spatial dimensions. as you subdivide matter into its atoms and then into its sub - particles and finally down into various fundamental particles, you increase the degrees of freedom. the holographic principle implies that at some point there is a limit to the subdivisions you can make, and at that point you reach some kind of fundamental particle containing a single bit of information ( like the zeros and 1 ' s of a computer ' s binary language - or like a 1 - dimensional string in string theory ). and here is where the universe, according to the holographic principle, should ultimately break down into fundamental pixels of reality, like the pixels in a photographic image, in this case grains of spacetime calculated to be planck length. searching for the universe ' s pixels first try : gravitational wave noise some scientists, such as craig hogan of fermilab, believe that this graininess, equivalent to quantum fuzziness, can be scaled up across the holographic universe and detected as very minute gravitational waves. the geo 600 in germany is the latest and most sensitive gravitational wave detector built. recall general relativity for a moment. gravity bends spacetime. as a result it can shorten distances. disturbances in spacetime caused by heavy - weight binary star systems made up of white dwarfs, neutron stars or black holes can ripple right across the universe as waves. the hulse - taylor binary, two neutron stars orbiting a common center of mass, has an orbital decay that is in exact agreement with the loss of energy through gravitational waves predicted by general relativity. these ripples, however, are expected to be very minute and none so far have been directly detected ( by any instrument ). the geo 600 can detect relative changes in distance on the scale of 10 - 21 m, that ' s about the size of a single atom compared to the distance between the sun and earth! along with detecting minute gravitational waves, noise in the geo 600 may be holographic noise. hogan ' s interpretation of the noise from geo 600 caused quite a stir in late 2010. he suggested that the noise is scaled up planck - length graininess, massively scaled up graininess. planck - length is on the scale of 10 - 35 m, a difference of 1014 between planck length and the detector ' s sensitivity! hogan claims that the noise should grow grainier across great distances, much


, massively scaled up graininess. planck - length is on the scale of 10 - 35 m, a difference of 1014 between planck length and the detector ' s sensitivity! hogan claims that the noise should grow grainier across great distances, much like a low - res movie played on a screen that is too big. so, larger scale ( 10 - 21 or more ) changes in distance could be traced back to planck - scale graininess at the edge of the universe, and it could be detected by the geo 600. unfortunately, it is very common for gravitational wave detectors to detect a noise background - they are extremely sensitive instruments. and physicists are still in the process of identifying and removing sources of noise. and, as mentioned, gravitational waves have yet to be directly detected. searching for the universe ' s pixels second try : gamma ray polarization some physicists calculate holographic noise, if it exists, to be on a much smaller scale than any current instrument can measure, much smaller than hogan ' s estimate. and so they have devised another ingenious way to look for evidence of holographic graininess in spacetime. the european space agency used its integral gamma - ray observatory in 2002 to look at gamma ray bursts. these are bursts of extremely high - energy gamma photons from supernovae. when the photons travel through spacetime, their polarization ( you can think of it as a twist ) is slightly affected. a polarized gamma ray preferentially scatters in a direction perpendicular to the direction of polarization. if spacetime is smooth, as einstein predicted, the polarization should remain random. that means there shouldn ' t be any difference between higher and lower energy photons no matter how far they travel. but if spacetime is grainy as the holographic principle predicts, the degree of polarization of the gamma rays should depend on distance and energy. the detector should detect random polarizations if einstein was right or it should detect a bias toward a particular polarization if the holographic theory is right. i ' m going to leave you in suspense for a moment about what they found, in order to introduce you to another very interesting problem that the holographic principle might solve, called locality. a fascinating new look at reality hogan ' s hypothesis violates a tenet of special relativity called locality. this means that an object is directly influenced only by its immediate surroundings. at first thought, this might seem to be a deathblow against the holographic principle.


reality hogan ' s hypothesis violates a tenet of special relativity called locality. this means that an object is directly influenced only by its immediate surroundings. at first thought, this might seem to be a deathblow against the holographic principle. but, locality is already violated by a widely accepted ( and experimentally verified ) phenomenon called quantum entanglement. let me give you an example to illustrate how this works : during nuclear decay processes, the events that take place must obey various conservation laws in physics. this means in the quantum world that various new particles that are generated as a particle decays must have specific quantum states. if a pair of particles is generated having a two - state spin, for example, one particle must be spin up and the other must be spin down. these particles are called an entangled pair. lets say they fly away in opposite directions. now here is the rub : when two objects ( they can be subatomic particles, molecules or even diamonds have been observed to obey this! ) interact physically and then become separated, each member of that pair is described as having the same quantum description. that means their state is indefinite until it is measured, according the the copenhagen interpretation of quantum mechanics. they are each in an equivalent state of quantum superposition. much later, when they are across the universe from each other, one person measures the spin of one of these particles. there is a 50 % chance it will be spin - up and 50 % chance it will be spin - down, depending on which one of the pair he measures. when one particle is measured, the quantum states of both particles collapses. if a second person then measures the second particle, its spin is 100 % predictable - it will be the opposite spin of the first one measured. let ' s say particle a collapsed into a spin up quantum state. how did particle b instantly get wind of that news from across the universe and collapse into a spin down state? nonlocality implies some kind of across - the - universe instantaneous communication between two particles. that ' s a violation of special relativity, which states that nothing, star ships, light or communication, can exceed light speed. experimental results have shown that effects due to entanglement travel at least thousands of times faster than the speed of light. what does this mean? it suggests that either nonlocality operates in quantum physics or there are hidden variables we don ' t know about yet. perhaps the measured spin of the particles is just one element of a larger yet unknown physical


of light. what does this mean? it suggests that either nonlocality operates in quantum physics or there are hidden variables we don ' t know about yet. perhaps the measured spin of the particles is just one element of a larger yet unknown physical reality or the assumption that we can measure a particle and collapse its spin into one definite state is not quite accurate. there is no transmission of information possible - no force transmission fast enough to account for projecting information across space between two separate physical systems. the fact that it happens is deeply unsettling. it is not easy to live in a classical world looking out into a quantum mechanical world, to use the words of physicist john stewart bell, who proposed the entanglement experiment described above and formulated bell ' s theorem based on it. these results led to the bohm interpretation of quantum mechanics. this interpretation gives non - locality a place in quantum mechanics, where all particles in the universe are able to instantaneously exchange information with all other particles. basil hiley, professor of physics, describes the challenge of thinking about particles and locality, and extends it to the conundrum of heisenberg ' s uncertainty principle, in this fascinating 10 - minute video : the bohm interpretation, as i understand it, does not provide us with an easy 1 - step answer to the problem of locality. instead, it asks us to rethink the problem of wave - particle duality and challenge our assumptions about particle reality. does the holographic principle provide a viable answer to the nonlocality problem? well, yes, in the sense that this principle implies a reality outside of spacetime, so that problems involving separation by space or time are transcended. nonlocality means that no particle in this universe is separate from any other particle. an electron in young ' s two - slit experiment, for example, seems to know beforehand where other electrons are going to be. according to this principle, we can view a particle such as an electron not as a material object moving through space but as something that unfolds out of a deeper level of reality that is outside of spacetime. in this reality, particles like electrons and photons can sniff out space before them. there is lots of evidence that they do just that. it ' s just that we can ' t observe their process because our perception of them is stuck in space and time. the holographic principle, therefore, seems to solve two very tricky problems in physics - black hole entropy and nonlocality. experimental


s just that we can ' t observe their process because our perception of them is stuck in space and time. the holographic principle, therefore, seems to solve two very tricky problems in physics - black hole entropy and nonlocality. experimental proof of the holographic theory? i left you in suspense over the gamma ray polarization experiment, so let ' s get back to it now. a gamma ray burst, such as the nasa artist ' s illustration below, is a random event and in order to detect and measure its photons, our detector ( and earth in general ) must be in line with one of its bipolar jets ( shown as yellow ). luckily, such a burst happened in 2004 ( well, for us anyway ), called grb 041219a. it was extremely bright and far away ( 300 million light years ), making its data a perfect candidate to test the holographic principle. no polarization difference was detected. the integral gamma - ray observatory detector is so precise it would be able to detect graininess down to a scale of 10 - 48 m, which is 1013 times smaller than planck length. some researchers, attempting to restore the holographic principle, have suggested that gamma rays perhaps don ' t behave as expected in this grainy universe. to conclude, no one has yet experimentally verified the holographic principle. so far, two experiments appear to refute its existence. specifically, they refute a measurable graininess or pixilation of spacetime. it might be possible that the assumption of underlying pixilation is itself incorrect but the idea of a three - dimensional projection of spacetime of a two - dimensional universe may still hold some validity. i suspect physicists right now are busy thinking of new ways to verify the principle. the next step : peering past a quantum - uncertain universe when the holographic principle was introduced in 2010, it captured the imagination of people worldwide. we can play with the bizarre possibility that we, and everything around us, are merely projections cast from some distant 2 - dimensional screen, that we are ignorant of our true flatness as we live out our lives inside an enormous sphere at least 13. 7 billions of light years across as projections from its inner surface. certainly this idea has huge philosophical implications. can you imagine god observing us as characters in a moving film projected over the surface of the universe? what does this mean for time? how about free will? this notion is at once absurd and alluring. this is why most physicist


mit physics news spotlight the bouncing gas clouds of gases that bounce off each other could help physicists model the behavior of high - temperature superconductors and other unusual materials. anne trafton, mit news office april 14, 2011 two gas clouds ( one red and one blue ), each a million times thinner than air, are seen to completely repel each other under the influence of strong, quantum - mechanical interactions. such gas clouds can model matter under extreme conditions, such as neutron stars or the quark - gluon plasma of the early universe. image : martin zwierlein when two clouds of gas meet, they normally pass right through each other. but now, mit physicists have created clouds of ultracold gases that bounce off each other like bowling balls, even though they are a million times thinner than air. this marks the first time that such impenetrable gases have been observed. while this experiment involved clouds of lithium atoms cooled to near absolute zero, the findings could also help explain the behavior of other strongly interacting systems such as neutron stars, high - temperature superconductors and quark - gluon plasma : the hot soup of elementary particles that formed immediately after the big bang. a paper describing the work appears in the april 14 issue of nature. the researchers, led by mit assistant professor of physics martin zwierlein, carried out their experiment with an isotope of lithium that belongs to a class of particles called fermions. all building blocks of matter — electrons, protons, neutrons and quarks — are fermions. different states of fermionic matter are distinguished by their mobility. for example, electrons can be mobile, as in a metal ; immobile, as in an insulator ; or flow without resistance, as in a superconductor. however, for many types of material, including high - temperature superconductors, it is not known what circumstances induce fermions to form a given state of matter. this is especially true of materials with strongly interacting fermions — that is, fermions that are more likely to collide with each other ( also called scattering ). in this study, the researchers set out to model strongly interacting systems, using lithium gas atoms to stand in for electrons. by tuning the lithium atoms ’ energy states with a magnetic field, they made the atoms interact with each other as strongly as the laws of nature allow : they scatter every time they encounter another atom. to eliminate any effects of temperature, the researchers


. by tuning the lithium atoms ’ energy states with a magnetic field, they made the atoms interact with each other as strongly as the laws of nature allow : they scatter every time they encounter another atom. to eliminate any effects of temperature, the researchers cooled the gas to about 100 billionths of one kelvin, close to absolute zero ( - 273 degrees celsius ). they used magnetic forces to separate the gas into two clouds, labeled “ spin up ” and “ spin down, ” then made the clouds collide in a trap formed by laser light. instead of passing through each other, as gases would normally do, the clouds repelled in dramatic fashion. “ when we saw that these ultra dilute puffs of gas bounce off each other, we were completely in awe, ” says graduate student ariel sommer, lead author of the naturepaper. the gas clouds did eventually diffuse into each other, but it took more than an entire second — an extremely long time for events occurring at microscopic scales. in fact, this diffusion was shown by the mit researchers to be the slowest allowed by quantum mechanics. john thomas, professor of physics at duke university, called the result “ amazing, ” given the fact that under normal circumstances, two clouds of gases composed of a mix of up and down spins diffuse into each other immediately. “ it ’ s quite remarkable that these gases would actually turn around and bounce, ” says thomas, who was not involved in this research. the research, conducted at the mit - harvard center for ultracold atoms, is part of a program aimed at using ultracold atoms as easily controllable model systems to study the properties of complex materials, such as high - temperature superconductors and novel magnetic materials that have applications in data storage and improving energy efficiency. in future work, the researchers plan to confine the lithium gases to two dimensions, which will allow them to simulate the mostly two - dimensional confinement of electrons in high - temperature superconductors. their work can also be used to model the behavior of other strongly interacting systems, such as high - density neutron stars, which are only about 10 kilometers in diameter but more massive than our sun. another substance that interacts as strongly as the atoms in the ultracold lithium gas clouds created at mit is the quark - gluon plasma that existed in the beginning of our universe and has been recreated in particle accelerators, such as the large hadron collider at cern, by colliding atomic nuclei at energies corresponding to a


seismology is the scientific study of earthquakes and the propagation of elastic waves through the earth or through other planet - like bodies. the field also includes studies of earthquake effects, such as tsunamis as well as diverse seismic sources such as volcanic, tectonic, oceanic,..., a microseism is defined as a faint earth tremor caused by natural phenomena. the term is most commonly used to refer to the dominant background seismic noise signal on earth, which are mostly composed of rayleigh waves and caused by water waves in the oceans and lakes. thus a microseism is a small and long - continuing oscillation oscillation is the repetitive variation, typically in time, of some measure about a central value or between two or more different states. familiar examples include a swinging pendulum and ac power. the term vibration is sometimes used more narrowly to mean a mechanical oscillation but sometimes... of the ground. detection and characteristics microseisms are very well detected and measured by means of a broad - band seismograph, and can be recorded anywhere on earth. dominant microseism signals from the oceans are linked to characteristic ocean swell periods, and thus occur between approximately 4 to 30 seconds. microseismic noise usually displays two predominant peaks. the weaker is for the larger periods, typically close to 16 s, and can be explained by the effect of surface gravity waves in shallow water. these microseisms have the same period as the water waves that generate them, and are usually called ' primary microseisms '. the stronger peak, for shorter periods, is also due to surface gravity waves in water, but arises from the interaction of waves with nearly equal frequencies but nearly opposite directions. these tremors have a period which is half of the water wave period and are usually called ' secondary microseisms '. a slight, but detectable, incessant excitation of the earth ' s free oscillations, or normal modes, with periods in the range 30 to 1000 s are also caused by water waves, and is often referred to as the " earth hum ". this hum is probably generated like the secondary microseisms but from the interaction of infragravity waves. as a result, from the short period ' secondary microseisms ' to the long period ' hum ', this seismic noise contains information on the sea state in oceanography, a sea state is the general condition of the free surface on a large body of water — with respect to wind waves and swell — at


very large small - world graphs, two simplified models serve as useful points of reference. the simplest of all graph models are lattices — highly regular graphs in which every vertex is joined to a few neighbors. the term lattice brings to mind a two - dimensional square grid, but a lattice can have other geometries. the minimal lattice is a one - dimensional structure, like a row of people holding hands. bending this linear lattice around and joining the two ends creates a ring lattice, or cycle. a nearest - neighbor ring lattice with n vertices has n edges, and every vertex has degree 2, meaning that two edges meet there. when edges extend both to nearest neighbors and to next - nearest neighbors, the ring has 2n edges and vertices of degree 4. how does the ring lattice perform as a model of small - world graphs? not terribly well. it is suitably sparse, with just n edges in the nearest - neighbor case, and there is a sense in which it is highly clustered, since all the edges are " local. " but the diameter is not small. the only way to travel in a ring is to go from neighbor to neighbor ; the lattice is like a railroad line without an express track. the diameter of the nearest - neighbor ring is n / 2, which is much larger than log n. whereas a lattice is a very orderly graph, the other benchmark model is maximally random. the graphs in this class were first studied around 1960 by the hungarian mathematicians paul erdos and alfred renyi. to build one of their graphs, you start with a collection of n vertices and no edges. then you make a sweep through the graph, considering every possible pairing of vertices, and in each case you either draw an edge with probability p or do nothing with probability 1 - p. the outcome of this process is easy to predict in the extreme cases : if p = 0, the graph remains edgeless, and if p = 1, the graph becomes a clique. between the extremes, you can expect the graph to have about pn2 / 2 edges, placed randomly and independently. erdos and renyi proved a number of interesting results about these graphs. most of the proofs are statements about " almost every " random graph ; this sounds like a strangely vague manner of speaking for mathematical discourse, but it has a precise meaning. saying that almost every random graph has some property q means that as the size of the graph n goes to infinity, the probability of q approaches 1. for example, erdos and ren


of speaking for mathematical discourse, but it has a precise meaning. saying that almost every random graph has some property q means that as the size of the graph n goes to infinity, the probability of q approaches 1. for example, erdos and renyi showed that if the edge probability p is greater than a certain threshold, then almost every random graph is connected. this doesn ' t mean you can ' t construct disconnected graphs if you set out to do so, but the random process has no chance of producing them when n approaches infinity. as a model of small - world networks, the erdos - renyi random graph has some strengths. it can be made as dense or as sparse as necessary just by adjusting the edge probability p. and the diameter tends to be small ( in some cases too small ). but erdos - renyi graphs show no tendency to form clusters. they cannot, since the edges are placed independently, and neighbors of neighbors are no more likely to be linked than any other randomly chosen vertices. rewiring the lattice it ' s not really surprising that the lattice model and the erdos - renyi model fail to reproduce some features of networks such as the human friendship graph or the world wide web. after all, these real - world networks are neither entirely regular nor entirely random. people generally know their neighbors, but their circle of acquaintances is not confined to those who live next door, as the lattice model would imply. conversely, links between pages on the web are not created at random, as the erdos - renyi process requires. watts and strogatz deal with these failures by a strategy that seems perfectly obvious once someone else has thought of it : they interpolate between the two models. they begin with a regular lattice, such as a ring, and then " rewire " some of the edges to introduce a measure of randomness. each edge in the original lattice is examined in turn, and is either left in place or else is redirected to another randomly chosen destination. the decision to rewire an edge is governed by a probability p, which can be adjusted over the range from 0 to 1. if p is equal to 0, then nothing happens ; the lattice is unchanged. if p is equal to 1, the lattice is transformed into a random graph much like a product of the erdos - renyi procedure. the interesting range lies between these extremes. in their analysis of the rewired graphs, watts and strogatz examined not the diameter — the shortest path between the


than 3. 4785, almost every graph has a giant component — a single large, connected piece that includes most of the vertices and edges in the graph. when β is less than 1, high - degree vertices are so abundant that almost every graph consists of one connected piece. aiello, chung and lu developed their model with a specific family of real - world graphs in mind, namely " call graphs " recording long - distance telephone traffic. as described in part i, a call graph has telephone numbers as its vertices, and an edge is drawn between two vertices whenever a call is placed between the corresponding numbers. analysis of an actual call graph shows that the degree sequence is not quite a perfect power law, and yet the model captures important features of the graph. the best approximation has parameter values of roughly α = 17 and β = 2. 1. since β lies between 1 and 3. 4785, the model predicts that the graph is not connected but does have a giant component. graph practice, in theory it may seem remarkable that the abstract and austere formalism of graph theory would prove useful in explaining such worldly phenomena as the architecture of the world wide web or the casting of hollywood films or patterns of telephone calls. but graph theory is a branch of mathematics that has never been afraid to get its hands dirty with applications. early on, it had close and fruitful encounters with organic chemistry and electrical engineering. in another sense, though, the sudden blooming of graphs — the tendency to see them everywhere we look — is indeed new and noteworthy. for a long time, science has preferred to see the world through a grid of cartesian coordinates, organizing everything around us according to row and column, rank and file, latitude and longitude. although there have always been exceptions to this rectilinear prejudice — notably the treelike structures of taxonomists and grammarians — the simplicity of lattices has been hard to resist. and both lattices and trees have a convenient property that physicists call locality. the only way to move through a lattice or a tree is to crawl from one node to the next. there is no action at a distance ; there are no secret wormholes connecting distant parts of the universe. graphs are a generalization of both lattices and trees. they admit more - flexible arrangements and less - regular connections in the way the world is put together. in graphs the principle of locality can be violated, as the shortcuts in the watts - strogatz model make explicit. such subterranean channels make


a new advance in x - ray imaging has revealed the dramatic three - dimensional shape of gold nanocrystals, and is likely to shine a light on the structure of other nano - scale materials. described today in nature communications, the new technique improves the quality of nanomaterial images, made using x - ray diffraction, by accurately correcting distortions in the x - ray light. dr jesse clark, lead author of the study from the london centre for nanotechnology said : " with nanomaterials playing an increasingly important role in many applications, there is a real need to be able to obtain very high quality three dimensional images of these samples. " up until now we have been limited by the quality of our x - rays. here we have demonstrated that with imperfect x - ray sources we can still obtain very high quality images of nanomaterials. " up until now, most nanomaterial imaging has been done using electron microscopy. x - ray imaging is an attractive alternative as x - rays penetrate further into the material than electrons and can be used in ambient or controlled environments. however, making lenses that focus x - rays is very difficult. as an alternative, scientists use the indirect method of coherent diffraction imaging ( cdi ), where the diffraction pattern of the sample is measured ( without lenses ) and inverted to an image by computer. nobel prize winner lawrence bragg suggested this method in 1939 but had no way to determine the missing phases of the diffraction, which are today provided by computer algorithms. cdi can be performed very well at the latest synchrotron x - ray sources such as the uk ' s diamond light source which have much higher coherent flux than earlier machines. cdi is gaining momentum in the study of nanomaterials, but, until now, has suffered from poor image quality, with broken or non - uniform density. this had been attributed to imperfect coherence of the x - ray light used. the dramatic three - dimensional images of gold nanocrystals presented in this study demonstrate that this distortion can be corrected by appropriate modelling of the coherence function. professor ian robinson, london centre for nanotechnology and author of the paper said : " the corrected images are far more interpretable that ever obtained previously and will likely lead to new understanding of structure of nanoscale materials. " the method should also work for free - electron - laser, electron - and atom - based diffractive imaging. notes for editors 1. for more information or to speak


- ( march - june 1888 ) ( a ) i observe with astonishment that science has today resigned itself to the apparent world ; a real world - - whatever it may be like - - we certainly have no organ for knowing it. at this point we may ask : by means of what organ of knowledge can we posit even this antithesis? - - that a world accessible to our organs is also understood to be dependent upon these organs, that we understand a world as being subjectively conditioned, is not to say that an objective world is at all possible. who compels us to think that subjectivity is real, essential? the " in - itself " is even an absurd conception ; a " constitutioning - itself " is nonsense ; we possess the concept " being, " " thing, " only as a relational concept - - the worst thing is that with the old antithesis " apparent " and " true " the correlative value judgment " lacking in value " and " absolutely valuable " has developed. the apparent world is not counted as a " valuable " world ; appearance is supposed to constitute an objection to supreme value. only a " true " world can be valuable in itself - - prejudice of prejudices! firstly, it would be possible that the true constitution of things was so hostile to the presuppositions of life, so opposed to them, that we needed appearance in order to be able to live - - after all, this is the case in so many situations ; e. g., in marriage. our empirical world would be determined by the instincts of self - preservation even as regards the limits of its knowledge : we would regard as true, good, valuable that which serves the preservation of the species - - a. we possess no categories by which we can distinguish a true from an apparent world. ( there might only be an apparent world, but not our apparent world. ) b. assuming the true world, it could still be a world less valuable for us ; precisely the quantum of illusion might be of a higher rank on account of its value for our preservation. ( unless appearance as such were grounds for condemnation? ) c. that a correlation exists between degrees of value and degrees of reality ( so that the supreme values also possess the supreme reality ) is a metaphysical postulate proceeding from the presupposition that we know the order of rank of values ; namely, that this order of rank is a moral order - - only with this presupposition is truth necessarily part of the definition of all the highest


cognitive science is a cross - disciplinary enterprise devoted to understanding the nature of the mind. in recent years, investigators in philosophy, psychology, the neurosciences, artificial intelligence, and a host of other disciplines have come to appreciate how much they can learn from one another about the various dimensions of cognition. the result has been the emergence of one of the most exciting and fruitful areas of inter - disciplinary research in the history of science. this volume of original essays surveys foundational, theoretical, and philosophical issues across the discipline, and introduces the foundations of cognitive science, the principal areas of research, and the major research programs. with a focus on broad philosophical themes rather than detailed technical issues, the volume will be valuable not only to cognitive scientists and philosophers of cognitive science, but also to those in other disciplines looking for an authoritative and up - to - date introduction to the field. if you use one of kobo ' s free reading apps you won ' t need to worry about download options most of the time. your kobo reading app can easily add kobo store books to your library for a seamless reading experience. download options matter when : you want to read your book on an ereader other than the kobo ereader ( see here for a list of supported ereaders ). the book you want is only available as an adobe drm pdf. in both of these cases you will need to : download a copy of your book to your computer. open the book using a free application called adobe digital editions. you can also use digital editions to transfer the book to your ereader. see here for more information on digital editions. you can read this item on your computer using our free kobo desktop application. this application lets you read, manage your library of ebooks, and even shop for new ones. check out our demo for more information!


neuroscientists create fiber - optic method of arresting epileptic seizuresmain category : epilepsy also included in : medical devices / diagnostics article date : 28 jan 2013 - 1 : 00 pst neuroscientists create fiber - optic method of arresting epileptic seizures | patient / public : | uc irvine neuroscientists have developed a way to stop epileptic seizures with fiber - optic light signals, heralding a novel opportunity to treat the most severe manifestations of the brain disorder. using a mouse model of temporal lobe epilepsy, ivan soltesz, chancellor ' s professor and chair of anatomy & neurobiology, and colleagues created an eeg - based computer system that activates hair - thin optical strands implanted in the brain when it detects a real - time seizure. these fibers subsequently " turn on " specially expressed, light - sensitive proteins called opsins, which can either stimulate or inhibit specific neurons in select brain regions during seizures, depending on the type of opsin. the researchers found that this process was able to arrest ongoing electrical seizure activity and reduce the incidence of severe " tonic - clonic " events. " this approach is useful for understanding how seizures occur and how they can be stopped experimentally, " soltesz said. " in addition, clinical efforts that affect a minimum number of cells and only at the time of a seizure may someday overcome many of the side effects and limitations of currently available treatment options. " study results appear online in nature communications. more than 3 million americans suffer from epilepsy, a condition of recurrent spontaneous seizures that occur unpredictably, often cause changes in consciousness, and can preclude normal activities such as driving and working. in at least 40 percent of patients, seizures cannot be controlled with existing drugs, and even in those whose seizures are well controlled, the treatments can have major cognitive side effects. although the study was carried out in mice, not humans, soltesz said the work could lead to a better alternative to the currently available electrical stimulation devices. visit our epilepsy section for the latest news on this subject. university of california - irvine 24 may. 2013. < http : / / www. medicalnewstoday. com / releases / 255430. php > please note : if no author information is provided, the source is cited instead. contact our news editors for any corrections of factual information, or to contact the editors please use our feedback form. please send any medical news or health news


zodiac inflatable boat? on top of an electrically powered chassis. being lightweight means it can go further on a single charge? they claim up to 2, 500 miles. xp even says it can be safely driven off a 25 foot cliff? apparently the air - filled shell will protect you like airbags did nasa ' s mars exploration rover. i ' m not totally convinced. after all, i don ' t think nasa ' s instruments were loosely packed so they could rattle around inside their casing, like humans in a car. and xp ' s website doesn ' t show much evidence of a product yet. although they are offering to bet $ 50, 000 that their claims are true. what do you think? as for the competition, the endurance races that will decide who wins in the " conventional " and " alternative " categories of the automotive x - prize are scheduled for 2009. but few teams have gone public about entries. the fact the rules have not been finalised may be one reason? i think a lot more teams will go public after they are. in it, tahan argues that the world needs a new " public - friendly ", " rational " and " sexy " name for stuff that uses of quantum phenomena that have no classical counterpart. or, to quote tahan ' s proposed definition directly : " spookytechnology " encompasses all functional devices, systems, and materials whose utility relies in whole or in part on higher order quantum properties of matter and energy that have no counterpart in the classical world. these purely quantum traits may include superposition, entanglement, decoherence ( along with the quantum aspects of measurement and error correction ) or new behavior that emerges in engineered quantum many - body systems. as you may have guessed, the term comes from einstein ' s famous description of quantum entanglement as " spooky action at a distance ". tahan believes using " spookytechnology " could both capture the public ' s imagination and avoid any confusion between future quantum devices and older ones. other terms, such as " quantum information technology ", " entanglement - based technology " and even " quantronics " just aren ' t catchy enough, he says. have a go for yourself - you can choose exactly which kind of people you want to target. if you ' re a facebook user, it even tells you how many people your ad will reach. starting with 6 + million when the form is blank for a uk user, you can whittle it down to numbers it says


their discovery. the diagram shows how the cobalt ions form flat layers? alternate rows have magnetic moments pointing in opposite directions. the grey tetrahedra are made from oxygen ions with lithium ions ( not shown ) sandwiched in between. new technologies too often begin in walled gardens? services are closed, accessible only to certain users. aol found the downside to this : as the web became more open and more popular, its users climbed the walls to escape aol ' s subscriber - only pages and join with everyone else. at the virtual worlds conference and expo, the two firms revealed a plan to allow avatars to travel from one virtual world, say second life, to another, for example activeworlds. they suggest developing a set of open standards that allow an avatar to move between worlds easily, keeping its appearance, name and any digital currency? a kind of virtual passport scheme. if the city of beijing were to take on the new standard, the avatars of the 10, 000 people it hopes will work in a virtual version of the city could simply stroll into second life or another virtual world to relax after work. but could the proposal has the potential to take virtual worlds to a different place altogether. the web has no way to accommodate people as individual, certified and identifiable ( if necessary ) users. some say this has hampered development of the web? and allowed some illegal practices to flourish. under the ibm / linden scheme, people could have a single verifiable identity across all virtual worlds. that would make them more like the real world? and a lot less like the web. computer scientists just can ' t leave our internet search engines alone. last week it was better image searching. now, jaime teevan at microsoft thinks she? s found a fix for a very annoying problem. we ' ve all been there. you find some useful search results, but some of those useful results mysteriously disappear when you repeat the search a few days later. it happens because the search engines are continuously updated. but, it? s not all the search engine? s fault. teevan asked a test group to conduct a web search of their choice, and then quizzed them on exactly what they searched for an hour later. in just 60 minutes most of them had forgotten exactly what they typed. word order, capitalisation and phrasing all changed. the solution? re : search? a new add - on to your search engine of choice. it keeps a record of past searches and remembers the results it thinks you found most


x - ray and energy - loss spectroscopy the signals used in energy dispersive x - ray spectroscopy ( eds ) and electron energy - loss spectroscopy ( eels ) are caused by inelastic scattering ( involves loss of energy ) of electrons as they pass through the sample. these techniques form the basis of analytical microscopy and enable qualitative and quantitative compositional analyses, elemental mapping, and electronic property analysis for a wide range of elements. the field emission gun of the f20 ut scanning transmission electron microscope allows these analyses to be performed on a nanometer, and, in some cases, on an atomic scale. the characteristic x - rays typically used in eds are created when high - energy electrons of the beam eject inner shell electrons from atoms in the sample, and the ionized atoms return to their lowest energy states by replacing the missing inner shell electrons by electrons from the outer shells. this process results in either the emission of an x - ray or an auger electron, whose energy of emission is characteristic of the difference in energy of the two electron shells involved, thereby providing a unique signature to identify the type of atoms present. in an eds spectrum, we see sharp peaks corresponding to the characteristic x - rays emitted by the atoms of the different elements present in the sample. eels looks at the energy distribution of the electrons that have been inelastically scattered while passing through the sample. low energy losses ( < 50 ev ) correspond typically to electrons that have interacted with the weakly bound outer - shell electrons of the atoms in the sample and provide information about the electronic properties of the material. high losses ( > 50 ev ) correspond to electrons that have been inelastically scattered by the inner electron shells and so contain information characteristic of the atoms in the sample. a typical eels spectrum contains both a series of peaks at low energies created by plasmon oscillations or other phenomena and a series of low intensity ionization edges at high - energy losses, whose onset position is characteristic of the different types of atoms in the sample. the fine structure of the ionization edges can provide information on chemical bonding and atomic configurations. examples of electron energy - loss spectroscopy capabilities examples of energy dispersive x - ray spectroscopy capabilities | high - resolution z - contrast image of a c - si / a - si interface from a high - efficiency si heterojunction solar cell. the image reveals an atomically abrupt and flat c - si / a - si interface ( see next ). | for additional information, contact mowafak al - ja


zinc oxide is a compound formed from a combination of one molecule of the mineral zinc and one molecule of oxygen. zinc is one of the most abundant elements on the earth and is a silver - colored metal with a medium luster. when the metal combines with oxygen, it forms a white powder that slightly resembles flour or baking soda. for use in skin care and cosmetics products, zinc oxide can be produced through several methods. one way, called the french or direct process, involves heating pure zinc metal at extremely high temperatures until it forms a vapor and mixes with the air. then, the air is cooled, and the zinc oxide is captured in a special bag. this produces a potent, high quality form of the ingredient. the same method can be used with zinc that has already combined with other elements. known as the indirect or american process, this technique results in a finished product that is of lower potency. in laboratory settings, zinc oxide can be produced by combining different chemicals with solutions that contain zinc. another way to synthesize the ingredient is to pass electricity through a zinc electrode that is submerged in a liquid that contains oxygen in its molecules. these methods are used to produce large batches of medium - quality zinc oxide. the use of zinc oxide in natural medicine dates back as far as 500 bc, when it was used as an ointment in ancient india. by 1025, european physicians, including the greek doctor dioscorides, were using zinc oxide to treat growths on the skin, such as cancerous lesions. as research continued, the uses of zinc oxide expanded, and in the 20th century, mass - produced skin care products that contain the ingredient first appeared on the market. during the 1970s, the u. s. food and drug administration began regulating the production of sunscreens, products that are used to protect the skin from ultraviolet rays. zinc oxide is one of 17 approved substances that can be used as a sun - protective ingredient in sunscreens. of these ingredients, zinc oxide is known to absorb the most ultraviolet energy and protects against both uva and uvb rays, the two forms of sun energy that are the most damaging for the skin. zinc oxide sunscreens help to prevent the redness and irritation known as sunburn that happens as a result of prolonged exposure to the sun. these sunscreens also help limit the amount of cellular damage that occurs when the skin is subjected to ultraviolet energy. by reducing the amount of damage, zinc oxide sunscreens help to prevent sun damage that can lead to


there is a famous experiment illustrating the consequences of the wave - description for the probability to find an electron at a given point in space. if an electron - source is placed in front of a metal - sheet with two narrow slits, a recording - device behind this screen would detect a distribution of incoming electrons that is identical to an interference - pattern of waves passing through the double slit ( as would be seen when shining coherent, monochromatic light ( a laser produces this kind of light ) on the two slits ). this interference - pattern shows up no matter how low the rate of electrons coming through. even if only one single electron per hour would pass through the slits, there would, finally, be a distribution of detected electrons given by the well - known interference - pattern. this experiment clearly demonstrates the wave - characteristics of the electron - or more precisely, it demonstrates that the probability to find an electron at a given point in space and time is given by a wave - function. it is this probability - distribution that passes the double - slit and, quite logically, results in an interference - pattern on the other side - giving the resulting probability - distribution for the position of an electron behind the double - slit. so the electron * is * no wave. it ' s position is given by probabilities * that are described * by a wave - function. compare it to casting a dice - twice : the probability for any number on the dice is equal. so if you plan a game ( an experiment ) where you win depending on a specific combination of the two outcomes, the probability of possible results will be a combination of all probabilities. if you had some kind of dice with a huge number of faces ( say : 1000 ) and the probabilities for these numbers to show up would be ' modulated ' by a sine - function ( a simple wave - like distribution ), then the combination of casting the dice twice would be the interference - pattern of the two wave - functions that describe the probabilities for the numbers showing up... so the probabilities of all events and the combination of these probabilities describe the possible outcomes of the game. the probabilities for all number - combinations in ( number - ) space are given by a wave - function. the same is true for the electrons in the two - slit experiment. the possible position of the electron after passing the screen with the two slits is given by the probability - distribution that results from the wave - like probability distribution of the electron passing through the


the same is true for the electrons in the two - slit experiment. the possible position of the electron after passing the screen with the two slits is given by the probability - distribution that results from the wave - like probability distribution of the electron passing through the double - slit screen - either the left slit, or the right slit. this does * not * mean ( as is so often implied ) that the electron is passing thtough both slits simultaneously. just as it does not mean that your dice show all numbers simultaneously. it does not mean either that the electron is at every point in space at the same time. as your winning numbers are not all numbers on the dice. no, the probability to find the electron at a given point in space and time is described by a wavefunction. the probability to have your winning pair of numbers showing up in the experiment with the dice is described by a probability - distribution, that we just constructed to be a wavefunction. if the path of the electron is determined before travelling through one of the slits then, of course, the probability - distribution for the position of the electron is completely different : the position of the electron is known ( within principal limits ), the probability to find the electron at a different point is zero. if you cast the dice and record the number, the result of this ' experiment ' is known, the probability to get another number is zero. if the electron continues it ' s trip through the double - slit experiment there will be no resulting interference - pattern behind the screen. this is not surprising at all, because the probability - distribution for finding an electron at a given point is no longer a monochromatic wave showing equal probabilities for either path through any of the slits. the wave - function is a strongly localized package. no surprise here : also the result of casting your dice twice will no longer be described by a combination of all probabilities of the first cast and the second - since the first outcome was ' measured ' and is therefore determined. nobody would dare to say the dice have wave and matter duality - the wave describes the probabilities for a given point in ( number - ) space. the same for electrons, photons, anyones... they dont have wave and matter duality. the probability - distribution is described by a wave - function. the electron in a box is not at every point at the same time - the probability for being at any point might be equal at any time. the probability for any number on a dice