" the experiments showed that bismuth telluride could tolerate even higher temperatures than theorists had predicted. " this means that the material is closer to application than we thought, " chen said. this magic is possible thanks to surprisingly well - behaved electrons. the quantum spin of each electron is aligned with the electron ' s motion — a phenomenon called the quantum spin hall effect. this alignment is a key component in creating spintronics devices, new kinds of devices that go beyond standard electronics. " when you hit something, there ' s usually scattering, some possibility of bouncing back, " explained theorist xiaoliang qi. " but the quantum spin hall effect means that you can ' t reflect to exactly the reverse path. " as a dramatic consequence, electrons flow without resistance. put a voltage on a topological insulator, and this special spin current will flow without heating the material or dissipating. topological insulators aren ' t conventional superconductors nor fodder for super - efficient power lines, as they can only carry small currents, but they could pave the way for a paradigm shift in microchip development. " this could lead to new applications of spintronics, or using the electron spin to carry information, " qi said. " whether or not it can build better wires, i ' m optimistic it can lead to new devices, transistors, and spintronics devices. " fortunately for real - world applications, bismuth telluride is fairly simple to grow and work with. chen said, " it ' s a three - dimensional material, so it ' s easy to fabricate with the current mature semiconductor technology. it ' s also easy to dope — you can tune the properties relatively easily. " " this is already a very exciting thing, " he said, adding that the material " could let us make a device with new operating principles. " the high quality bismuth telluride samples were grown at simes by james analytis, ian fisher and colleagues. image : surface electron band structure of bismuth telluride. ( credit : image courtesy of yulin chen and z. x. shen ) simes, the stanford synchrotron radiation lightsource at slac, and the advanced light source at lawrence berkeley national laboratory are supported by the office of basic energy sciences within the doe office of science. slac national accelerator laboratory is a multi - program laboratory exploring frontier questions in photon science, astrophysics, particle physics and accelerator research. located in


definition of retina retina : the retina is the nerve layer that lines the back of the eye, senses light, and creates impulses that travel through the optic nerve to the brain. there is a small area, called the macula, in the retina that contains special light - sensitive cells. the macula allows us to see fine details clearly. the eye has a number of other components. these include the cornea, iris, pupil, lens, optic nerve and vitreous. the cornea is the clear front window of the eye that transmits and focuses light into the eye. the iris is the colored part of the eye that helps regulate the amount of light that enters the eye. the pupil is the dark aperture in the iris that determines how much light is let into the eye. the lens is the transparent structure inside the eye that focuses light rays onto the retina. the optic nerve is the nerve that connects the eye to the brain and carries the impulses formed by the retina to the visual cortex of the brain. the vitreous humor is a clear, jelly - like substance that fills the middle of the eye. source : medterms™ medical dictionary last editorial review : 4 / 27 / 2011 5 : 27 : 15 pm medical dictionary definitions a - z search medical dictionary emedicinehealth top news get breaking medical news. eye health resources health solutions from our sponsors most popular topics pill identifier on rxlist - quick, easy, find a local pharmacy - including 24 hour, pharmacies


is the type of power the hacker seeks. privilege escalation can best be described as the act of leveraging a bug or vulnerability in an application or operating system to gain access to resources that normally would have been protected from an average user. the end result of privilege escalation is that the application performs actions that are running within a higher security context than intended by the designer, and the hacker is granted full access and control. would you believe that hackers are paranoid people? well, many are, and they worry that their evil deeds might be uncovered. they are diligent at working on ways to maintain access to the systems they have attacked and compromised. they might attempt to pull down the etc / passwd file or steal other passwords so that they can access other useris accounts. rootkits are one option for hackers. a rootkit is a set of tools used to help the attacker maintain his access to the system and use it for malicious purposes. rootkits have the capability to mask the hacker, hide his presence, and keep his activity secret. they will be discussed in detail later on in the class. sometimes hackers might even fix the original problem that they used to gain access, where they can keep the system to themselves. after all, who wants other hackers around to spoil the fun? sniffers are yet another option for the hacker and can be used to monitor the activity of legitimate users. at this point, hackers are free to upload, download, or manipulate data as they see fit. nothing happens in a void, and that includes computer crime. hackers are much like other criminals in that they would like to be sure to remove all evidence of their activities. this might include using rootkits or other tools to cover their tracks. other hackers might hunt down log files and attempt to alter or erase them. hackers must also be worried about the files or programs they leave on the compromised system. file hiding techniques, such as hidden directories, hidden attributes, and alternate data streams ( ads ), can be used. as an ethical hacker, you will need to be aware of these tools and techniques to discover their activities and to deploy adequate countermeasures. backdoors are methods that the hacker can use to reenter the computer at will. the tools and techniques used to perform such activities are discussed later on in the class. at this point, what is important is to identify the steps. as an ethical hacker, you will follow a similar process to one that


( ansi ). from a security standpoint, the most critical process handled at this layer is encryption and decryption. if properly implemented, this can help security data in transit. session layer layer 5 is known as the session layer. its functionality is put to use when creating, controlling, or shutting down a tcp session. items such as the tcp connection establishment and tcp connection occur here. session - layer protocols include items such as remote procedure call and sqlnet from oracle. from a security standpoint, the session layer is vulnerable to attacks such as session hijacking. a session hijack can occur when a legitimate user has his session stolen by a hacker. this will be discussed in detail in lesson 7, " sniffers, session hijacking, and denial of service ". transport layer layer 4 is known as the transport layer. the transport layer ensures completeness by handling end - to - end error recovery and flow control. transport - layer protocols include tcp, a connection - oriented protocol. tcp provides reliable communication through the use of handshaking, acknowledgments, error detection, and session teardown, as well as user datagram protocol ( udp ), a connectionless protocol. udp offers speed and low overhead as its primary advantage. security concerns at the transport level include synchronize ( syn ) attacks, denial of service ( dos ), and buffer overflows. network layer layer 3 is known as the network layer. this layer is concerned with logical addressing and routing. the network layer is the home of the internet protocol ( ip ), which makes a best effort at delivery of datagrams from their source to their destination. security concerns at the network level include route poisoning, dos, spoofing, and fragmentation attacks. fragmentation attacks occur when hackers manipulate datagram fragments to overlap in such a way to crash the victimis computer. ipsec is a key security service that is available at this layer. data link layer layer 2 is known as the data link layer. the data link layer is responsible for formatting and organizing the data before sending it to the physical layer. the data link layer organizes the data into frames. a frameis a logical structure in which data can be placed ; itis a packet on the wire. when a frame reaches the target device, the data link layer is responsible for stripping off the data frame and passing the data packet up to the network layer. the data link layer is made up of two sub layers,


to predict the reduction in polymer chain orientation that occurs in nylon fibers drawn at high speeds. “ this is counterintuitive, ” he says. “ normally you would expect to see the increase in orientation with take - up speed to continue. ” this phenomenon had been observed by dupont researchers but never fully understood. “ the practical implication, ” says mchugh, “ is that we can now identify beforehand the upper limit in spin - speed for processing fibers with maximum orientational properties. ” some of the world ’ s leading synthetic fiber producers, including dow chemical, celanese acetate, dupont and exxonmobil, are now using mchugh ’ s models. in 2002, with the help of graduate student william kohler and postdoctoral associate prashant shrikhande, mchugh turned his attention to polylactic acid. “ one of the unusual features of pla, compared to most other polymers, is that the monomer, lactic acid, exists in two different forms : a d - and an l - form, ” he says. “ in molecular terms, the d - form is simply a mirror image of the l - form. ” anthony mchugh ’ s mathematical models account for physical changes that occur in a millisecond or less. polymerizing a mixture of the two forms produces a polymer with a relatively low melting point and mechanical properties poorly suited for fiber applications. using just one of these forms, say, the l - type, produces a highly crystalline polymer ( plla ) with superior mechanical properties and a melting temperature of 175 degrees c. combining equal amounts of both forms into a “ racemic ” mixture, however, results in the formation of a co - crystal phase that exhibits an even higher melting temperature and superior mechanical properties. the manufacture of pla fibers requires processing conditions greater than 190 degrees c. at these temperatures, reactions can cause a reduction in the polymer ’ s molecular weight and a degradation of its mechanical properties. “ clearly, this polymer has a very narrow processing window, ” says mchugh, “ which puts an even greater emphasis on the need to develop a reliable theoretical model. ” the first attempts to apply mchugh ’ s model did not meet expectations for plla. the chain - entangled nature of the polymer led to increased viscosity and greater spin speed. mchugh responded by using a newer constitutive equation that accounts for chain entanglements, the so - called “ extended pom - pom ” model. “ this modification


optical projection tomography ( opt ) optical projection tomography ( opt ) is an optical imaging tool that creates high resolution 3d images of samples that are over ten times larger than samples imaged with other optical microscopic techniques ( 1 ). opt images also have excellent contrast between a fluorescent region of interest and the rest of the specimen. in opt, a digital camera is used to capture an image of a transparent specimen. a specialized lens ensures that the image is formed only by the rays of light that are approximately parallel. this image is a projection through the specimen. a series of these projections obtained at various positions about the sample is used to create a 3 - dimensional image of the sample. opt is limited to transparent specimens as it is necessary to minimize light scattering through the sample. mouse embryos are ideal specimens for opt as they are naturally transparent. one of the great strengths of opt is the ability to acquire fluorescent images. this allows a researcher to tie fluorescent molecules to a particular type of molecule, such as a type of protein or gene. opt can be used to map the distribution of the fluorescent molecules, which is also a map of the distribution of molecule under study. at the mouse imaging centre, we have begun research into altering the data processing methods in order to obtain higher resolution images of larger specimens. this will allow researchers to use opt to study larger embryos and even complete organs. above left : three orthogonal planes out of an autofluorescence opt reconstruction of an e10. 5 wildtype mouse embryo. the resolution of this image is approximately 20 microns. above right : surface rendering of an e9. 5 wildtype mouse embryo. red : cardiac, white transparent : embryo. above : surface renderings of the cardiac region of e12. 5 wildtype ( left ) and e12. 5 baf60c knockdown ( right ) mouse embryos. the outflow tract of the wildtype heart undergoes constriction and septation, whereas the outflow tract of the mutant has no constriction and little septation. red : myocardium, yellow : interior vessels of great arteries. the myocardium is rendered transparently in the second set of images to easily see the interior of the great vessels. this work is described in " baf60c is essential for function of baf chromatin remodelling complexes in heart development " by h. lickert et. al., nature volume 432, nov 4 2004.


below are the first 10 and last 10 pages of uncorrected machine - read text ( when available ) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole. intended to provide our own search engines and external engines with highly rich, chapter - representative searchable text on the opening pages of each chapter. because it is uncorrected material, please consider the following text as a useful but insufficient proxy for the authoritative book pages. do not use for reproduction, copying, pasting, or reading ; exclusively for search engines. ocr for page 142 glossary of physical terms absolute zero. the temperature of - 273. 16°c, or - 459. 69°f, or zero kelvin ( o k ), thought to be the temperature at which molecular motion is at a minimum and a body has no heat energy. alpha particle. a positively charged particle consisting of two pro - tons and two neutrons, identical with the nucleus of the helium atom ; emitted by several radioactive substances. angstrom. a unit of length equal to one ten - billionth of a meter ( 10 - ' ° m ). anisotropy. the characteristic of a substance for which a physical property varies in value with the direction in or along which the measurement is made. antimatter. material consisting of atoms that are composed of positrons, antiprotons, and antineutrons. antineutron. the antiparticle to the neutron ; a strongly interacting baryon that has no charge, mass of 939. 6 mev, spin 1 / 2, and mean life of almost 103 seconds. antinucleon. an antineutron or antiproton, that is, a particle having the same mass as its nucleon counterpart but opposite charge or opposite magnetic moment. · ·. ~ ·......... antiparticle. a counterpart to a particle, having mass, lifetime, and spin identical to the particle but with charge and magnetic moment.. reverser in sign. antiproton. the antiparticle of the proton, a strongly interacting 142 ocr for page 143 glossar y of physical terms 143 baryon that is stable, carries unit negative charge, has the same mass as the proton ( 983. 3 mev ), and has spin 1 / 2. astrophysics. the study of such physical properties of celestial bodies as luminosity, size, mass, density, temperature


negative charge, has the same mass as the proton ( 983. 3 mev ), and has spin 1 / 2. astrophysics. the study of such physical properties of celestial bodies as luminosity, size, mass, density, temperature, and chemical composition ; the study of the origin and evolution of these bodies. asymptotic freedom. in some particle - physics theories, the binding force between two quarks decreases as their relative momentum increases ; equivalently, as two quarks approach, the force between them disappears. atom. the individual structure that constitutes the basic unit of any chemical element. atomic number. the number of protons in an atomic nucleus. atomic physics. the science concerned with the structure of the atom. the characteristics of the elementary particles of which the atom is composed and the processes involved in the interactions of radiant energy with matter. atomic spectrum. the spectrum of radiations due to transitions between energy levels in an atom, either absorption or emission. aurora. the most intense of the several lights emitted by the earth ' s upper atmosphere, seen most often along the outer realms of the arctic and antarctic, where it is called the aurora borealis and aurora australis, respectively ; excited by charged particles from space. baryon. a particle that can be transformed into a nucleon and some number of mesons and lighter particles ; any of a group of hadrons ( as nucleons ) that undergo strong interactions and are held to be a combination of three quarks. beta decay. radioactive transformation of a nuclide in which the atomic number increases or decreases by unity with no change in mass number ; the nucleus emits a beta particle. beta particle. an electron or positron emitted from a nucleus during beta decay. big bang. a theory in astronomy, according to which the universe originated billions of years ago from the explosion of a single mass of material, so that the pieces are still hying apart. biophysics. the hybrid science involving the application of physical principles and methods to study and explain the structures of living organisms and the mechanics of life processes. black hole. a star with radius just outside the schwarzschild radius ; it is invisible but can capture matter and light from the outside. boson. a particle ( as a photon, meson, or alpha particle ) whose spin is zero or an integral number. ocr for page 144 144 glossary of physical terms " breathing " mode. the vibrational state in which a nucleus under - goes spherically symmetric


as a photon, meson, or alpha particle ) whose spin is zero or an integral number. ocr for page 144 144 glossary of physical terms " breathing " mode. the vibrational state in which a nucleus under - goes spherically symmetric radial expansion and contraction. charged particle. a particle whose charge is not zero ; the charge of a particle is added to its designation as a superscript with particles of ~ 1 and - 1 ( in terms of the charge of the proton ) denoted by ~ arid -, respectively. coherent anti - stokes raman scattering. nonlinear spectroscopy where laser light scattered from a sample undergoes an increase in frequency ( anti - stokes behavior ), derived from vibrational states of the atoms or molecules in the sample. condensed matter ¢physics ). the physics of the solid and liquid states. cosmic rays. electrons, muons, the nuclei of atoms, and photons that impinge upon the earth from all directions of space with nearly the speed of light. cosmology. the study of the overall structure of the physical uni - verse. crystallography. the branch of science that deals with the geometric description of crystals and their internal arrangement. cyclotron. an accelerator in which charged particles are succes - sively accelerated by a constant - frequency alternating electric field that is synchronized with movement of the particles on spiral paths in a constant magnetic field normal to their path. deuteron. the nucleus of the deuterium atom consisting of one proton and one neutron. diabatic. a change in which the environment of a system alters too rapidly for the system to read just continuously. diamagnetic. having a magnetic permeability less than that of a vacuum ; slightly repelled by a magnet. dirac electron theory. theory that accounts for spin angular momen - tum of the electron and gives its magnetic moment and its behavior in an electromagnetic field. doppler elect. the change in the observed frequency of a wave due to relative motion of source and observer. electromagnetic theory. theory according to which light is an elec - tromagnetic wave whose electric and magnetic fields obey maxwell ' s equations. electromagnetism. magnetism produced by an electric current rather than by a permanent magnet. electron. an elementary particle consisting of a charge of negative electricity equal to about 1. 602 x 10 - ~ 9 coulomb and having a mass when at rest of about 9. 109534 x 10 - 28 gram ( or about 1 / 1836 that


elementary particle consisting of a charge of negative electricity equal to about 1. 602 x 10 - ~ 9 coulomb and having a mass when at rest of about 9. 109534 x 10 - 28 gram ( or about 1 / 1836 that of a proton ). ocr for page 145 glossary of physical terms 145 electron accelerator. energies. electron charge. the charge carried by an electron, equal to about - 1. 602 x 10 - ~ 9 coulomb, or - 4. 803 x 10 - ~ ° statcoulomb. elementary particle. a particle that, in the present state of knowl - edge, cannot be described as compound and is thus one of the fundamental constituents of all matter. entropy. the degradation of the matter and energy in the universe to an ultimate state of inert uniformity. epitaxy. growth of one crystal on the surface of another crystal, in which the growth of the deposited crystal is oriented by the lattice structure of the substrate. equivalence principle. in general relativity, the principle that the observable local effects of a gravitational field are indistinguishable from those arising from acceleration of the frame of reference. far - ultraviolet radiation. ultraviolet radiation in the wavelength of 200 to 300 nanometers ; germicidal effects are greatest in this range. femto -. prefix meaning one quadrillionth ( lo - ~ 5 ) part of. fermion. a particle ( as an electron, proton, or neutron ) whose spin quantum number is an odd multiple of l / 2. ferromagnet. a substance with an abnormally high magnetic perme - ability, a definite saturation point, and appreciable residual magne - tism and hysteresis. fission. the division of an atomic nucleus into parts of comparable mass ; usually restricted to heavier nuclei such as isotopes of uranium, plutonium, and thorium. fluorescence. emission of, or the property of emitting, electromag - netic radiation ( usually as visible light ) resulting from and occurring only during absorption of radiation from some other source. free - electron laser. a laser in which beams of unbound electrons interact with a strong magnetic field to produce tunable laser light. free radical. an atom or a diatomic or polyatomic molecule that possesses at least one unpaired electron. fusion. combination of two light nuclei to form a heavier nucleus ( and perhaps other reaction products ) with release of some binding a


free radical. an atom or a diatomic or polyatomic molecule that possesses at least one unpaired electron. fusion. combination of two light nuclei to form a heavier nucleus ( and perhaps other reaction products ) with release of some binding a device that accelerates electrons to high energy. galaxy. a large - scale aggregate of stars, gas, and dust. the aggregate is a separate system of stars covering a mass range from 107 to 10 ~ 2 solar masses and ranging in diameter from 1500 to 300, 000 light - years. gamma ray. a high - energy photon, especially as emitted by a nucleus in a transition between two energy levels. general relativity. the theory of einstein that generalizes special ocr for page 146 146 glossary of physical terms relativity to noninertial frames of reference and incorporates gravi - tation and in which events take place in a curved space. geophysics. the physics of the earth and its environment, i. e., earth, air, and ( by extension ) space. glass. a hard, amorphous, inorganic, usually transparent, brittle substance made by fusing silicates, sometimes berates and phos - phates, with certain basic oxides and then rapidly cooling to prevent crystallization ( nb : not the sense in which the term is used in the term spin glass ). gluon. a hypothetical, neutral, massless particle believed to bind together quarks to form hadrons. gluon string. a particle - physics theoretical model to account for the binding force between quarks that increases monotonically as they are separated. gravitation. the mutual attraction among all masses in the universe. gravitational force. the force on a particle due to its gravitational attraction to other particles. gravitational radiation. a propagating gravitational field predicted by general relativity, which is produced by some change in the distribution of matter ; it travels at the speed of light, exerting forces on masses in its path. gravitational redshift. a displacement of spectral lines toward the red when the gravitational potential at the observer of the light is greater than at its source. gyrotron. a device for producing microwave energy. also called an electron cyclotron maser. hadron. any of the particles that take part in the strong interaction. hall conductivity. the reciprocal of the electrical resistivity associ - ated with the hall current. hall current. when an electric current in a conductor is placed in a magnetic field that is


the particles that take part in the strong interaction. hall conductivity. the reciprocal of the electrical resistivity associ - ated with the hall current. hall current. when an electric current in a conductor is placed in a magnetic field that is perpendicular to the current a transverse electric field is created, which in turn can support a transverse current. heavy - ion linear accelerator. a linear accelerator that produces a beam of heavy particles of high intensity and sharp energy ; used to produce transuranic elements and short - lived isotopes and to study nuclear reactions, nuclear spectroscopy, and the absorption of heavy.. tons in matter. helicity. the component of the spin of a particle along its momen - tum. hydrogen maser. a maser in which hydrogen gas is the basis for providing an output signal with a high degree of stability and spectral purity. ocr for page 147 glossar y of physical terms 147 hypercharge. a quantum number conserved by strong interactions, equal to twice the average of the changes of the numbers of an isospin multiplet. hypernucleus. a nucleus containing one or more hyperons in addi - tion to the nucleons. hyperon. a hadron that has baryon number b = + 1, i. e., that can be transformed into a nucleon and some number of mesons or lighter particles and that has a nonzero strangeness number. ionicity. the state of being characterized by, relating to, or existing as ions. isospin multiplet. a collection of hadrons that have approximately the same mass and the same quantum numbers except for charge. isotropy. the quality of a property that does not depend on the direction along which it is measured or of a medium or entity whose properties do not depend on the direction along which they are measured. joule. unit of energy, work, or quantity of heat equal to one newton - meter. jo particle. an unstable, neutral meson that has a mass about 3 times the mass of the photon. k meson. see kaon. kaon. collective name for four pseudoscalar mesons having masses of about 495 mev and decaying via weak interactions ; an unstable meson produced in high - energy particle collisions with its electri - cally charged forms being 966. 3 times more massive than the electron ; also known as k meson. lamb shift. a small shift in the energy levels of a hydrogen atom, and of hydrogenlike


energy particle collisions with its electri - cally charged forms being 966. 3 times more massive than the electron ; also known as k meson. lamb shift. a small shift in the energy levels of a hydrogen atom, and of hydrogenlike ions, from those predicted by the dirac electron theory, in accord with principles of quantum electrodynamics. lambda hyperon ( a ). a quasi - stable baryon, forming an isotopic singlet, having zero charge and hypercharge, a spin of 1 / 2, positive parity, and mass of 1115. 5 mev. laser. a device that uses the maser principle of amplification of electromagnetic waves by stimulated emission of radiation and operates in the optical or infrared region. derived from light amplification by stimulated emission of radiation. laser interferometer. an interferometer that uses a laser as a light source ; because of the monochromaticity and high intrinsic brilliance of laser light, it can operate with path differences in the interfering beams of hundreds of meters, in contrast to a maximum of about 20 centimeters for classical interferometers. laser light. coherent, nearly single - frequency, highly directional ocr for page 148 148 glossar y of physical terms electromagnetic radiation emitted in the range from infrared to ultraviolet and x - ray wavelengths. laser optics. optical systems utilizing the properties of laser light. laser spectroscopy. a branch of spectroscopy in which a laser is used as an intense, monochromatic light source ; in particular, it includes saturation spectroscopy, as well as the application of laser sources to raman spectroscopy and other techniques. lepton. any of a family of particles ( as electrons, muons, and neutrinos ) that have spin quantum number 1 / 2 and that experience no strong interactions ; a fermion having a mass smaller than the proton mass. light. electromagnetic radiation with wavelengths capable of caus - ing the sensation of vision, ranging approximately from 4000 ( ex - treme violet ) to 7700 angstroms ( extreme red ) ; more generally, electromagnetic radiation of any wavelength. light - year. a unit of measurement of astronomical distance ; it is the distance light travels in one sidereal year and is equivalent to 9. 461 x 10 ~ 2 kilometers or 5. 879 x 10 ~ 2 miles. luminosity. in optics, a measure of the brightness of a light source ; in colliding - beam accelerators, a measure of the rate of collisions of the particles


~ 2 kilometers or 5. 879 x 10 ~ 2 miles. luminosity. in optics, a measure of the brightness of a light source ; in colliding - beam accelerators, a measure of the rate of collisions of the particles in the colliding beams. macromolecule. a large molecule in which there is a large number of - one or several relatively simple structural units, each consisting of several atoms bonded together. magnetic hysteresis. lagging of changes in the magnetization of a substance behind changes in the magnetic field as the magnetic field 1s varlec. magnetic moment. a vector associated with a magnet, current loop, particle, or such, whose cross product with the magnetic induction ( or alternatively, the magnetic - field strength ) of a magnetic field is equal to the torque exerted on the system by the field. magnetic monopole. a hypothetical particle carrying magnetic charge ; it would be a source for magnetic field in the same way that a charged particle is a source for electric held. magnetic permeability. a factor, characteristic of a material, that is proportional to the magnetic induction produced in a material divided by the magnetic - field strength ; it is a tensor when these qualities are not parallel. magnetic resonance. a phenomenon exhibited by the magnetic spin systems of certain atoms whereby the spin systems absorb energy at specific ( resonant ) frequencies when subjected to magnetic fields alternating at frequencies that are in synchronism with natural frequencies of the system. ocr for page 149 glossar y of physica ~ terms 149 maser. a device for coherent amplification or generation of electro - magnetic waves in which an ensemble of atoms or molecules, raised to an unstable energy state, is stimulated by an electromagnetic wave to radiate excess energy at the same frequency and phase as the stimulating wave. mass number. the sum of the numbers of protons and neutrons in the nucleus of an atom or nuclide. matter. the substance composing bodies perceptible to the senses ; includes any entity possessing mass when at rest. meson. any of a group of hadrons ( as the pion and loon ) that are strongly interacting and have zero or an integer number of quantum units of spin. metastability. the property of having only a slight margin of stabil - ity. metrology. the science of weights and measures or of measurement. mho. a unit of conductance, admittance, and susceptance equal to the conductance


the property of having only a slight margin of stabil - ity. metrology. the science of weights and measures or of measurement. mho. a unit of conductance, admittance, and susceptance equal to the conductance between two points of a conductor such that a potential difference of 1 volt between these points produces a current of 1 ampere ; the conductance of a conductor in mhos is the reciprocal of its resistance in ohms. microelectronics. the technology of constructing circuits and de - vices in extremely small packages by various techniques. microemulsion. a homogenous, single - phase, thermodynamically stable mixture of oil, water, and surfactant. million electron volts ( me vj. a unit of energy commonly used in nuclear and particle physics, equal to the energy acquired by an electron in falling through a potential of 106 volts. molecular biology. ~...... that nart of biology which attempts to interpret o ~ o ~ og ~ ca ~ events in terms of the physicochemical properties of molecules in a cell. molecular ion. a molecule possessing nonzero net electric charge. molecular physics. the study of the behavior and structure of molecules, including the quantum - mechanical explanation of several kinds of chemical binding between atoms in a molecule ; directed valence ; the polarizability of molecules ; the quantization of vibra - tional ' rotational, and electronic motions of molecules ; and the phenomena arising from intermolecular forces. molecule. a group of atoms held together by chemical forms ; a molecule is the smallest unit of matter that can exist by itself and retain all its chemical properties. monte carlo method. a technique that obtains a probabilistic ap - proximation to the solution of a problem by using statistical sampling techniques. ocr for page 150 150 glossar y of physical terms multiphoton spectroscopy. nonlinear spectroscopy usually involv - ing intense laser light enabling more than one photon to interact with an atom within a time frame shorter than the decay time of the atomic state. muon. collective name for two semistable elementary particles with positive and negative charge, which are leptons and have a spin of 1 / 2 and a mass of approximately 105. 7 mev. muonium. an atom consisting of an electron bound to a positively charged muon by their mutual coulomb attraction, just as an electron is bound to a proton in the hydrogen


/ 2 and a mass of approximately 105. 7 mev. muonium. an atom consisting of an electron bound to a positively charged muon by their mutual coulomb attraction, just as an electron is bound to a proton in the hydrogen atom. nano -. prefix meaning one billionth ( lo - 9 ) part of. neutrino. a neutral lepton having zero rest mass and spin 1 / 2. neutron. an uncharged hadron that has a mass nearly equal to that of the proton and is present in all known atomic nuclei except the hydrogen nucleus. newton. the unit of force equal to one kilogram - meter per second squared ( i kg m / s2 ~. nonlinear optics. the study of the interaction of radiation with matter in which certain variables describing the response of the matter ( such as electric polarization of power absorption ) are not proportional to variables describing the radiation ( such as electric - field strength or energy flux ). nonlinear spectroscopy. spectroscopy usually using laser light and the nonlinear optical behavior of certain properties of matter ; e. g., coherent anti - stokes raman scattering. nova. a star that suddenly becomes explosively bright ( the term is a misnomer because it does not denote a new star but the brightening of an existing faint star ). nuclear physics. the study of the characteristics, behavior, and internal structures of the atomic nucleus. nucleon. a collective name for a proton or a neutron ; these particles are the main constituents of atomic nuclei, have approximately the same mass, have a spin of l / 2, and can transform into each other through the process of beta decay. nucleosynthesis. the production of a chemical element from hydro - gen nuclei ( as in stellar evolution ). nucleus. the central, positively charged, dense portion of an atom. nuclide. a species of atom characterized by the number of protons, number of neutrons, and energy content in the nucleus ; to be regarded as a distinct nuclide, the atom must be capable of existing for a measurable lifetime, generally greater than 10 - ~ 2 second. parity. a physical property of a wave function that specifies its three behavior under an inversion, i. e., under simultaneous reflection of all ocr for page 151 glossar y of physical terms 151 three spatial coordinates through the origin ; if the wave function is unchanged by inversion, its parity is 1 ( or even ) ; if the function is changed only in sign, its parity is -


for page 151 glossar y of physical terms 151 three spatial coordinates through the origin ; if the wave function is unchanged by inversion, its parity is 1 ( or even ) ; if the function is changed only in sign, its parity is - 1 ( or odd ). particle physics. the branch of physics concerned with understand - ing the properties and behavior of elementary particles, especially through study of collisions or decays involving energies of hundreds of mev or more. pauli exclusion principle. the principle that no two fermions of the same kind may simultaneously occupy the same quantum state. phase. a portion of a physical system ( liquid, gas, solid ) that is homogeneous throughout, has definable boundaries, and can be separated physically from other phases ; the type of state of a system, such as solid, liquid, or gas. phase transition. a change of a substance from one phase ( e. g., solid, liquid, or gas ) to another. phonon. a quantum of an acoustic mode of thermal vibration in a crystal lattice. photoemission. the ejection of electrons from a solid ( or less com - monly, a liquid ) by incident electromagnetic radiation. photoionization. the removal of one or more electrons from an atom or molecule by absorption of a photon of visible or ultraviolet light. photon. a massless particle, the quantum of the electromagnetic field, carrying energy, momentum, and angular momentum. photovoltaic. of, relating to, or utilizing the generation of a voltage when radiant energy falls on the boundary between two dissimilar substances ( as two different semiconductors ). pion. a short - lived meson that is primarily responsible for the nuclear force and that exists as a positive or negative particle with mass 273. 2 times the electron mass or as a neutral particle with mass 264. 2 times the electron mass. planck ' s constant. a fundamental physical constant, the elementary quantum of action ; the ratio of the energy of a photon to its frequency, it is equal to 6. 62620 + 0. 00005 x 10 - 34 joule - second ; symbolized by h. plasma. a collection of charged particles ( as in the atmosphere of stars or in a metal ) containing about equal numbers of positive ions and electrons, exhibiting some properties of a gas but differing from a gas in being a good conductor of electricity and in being affected by a magnetic field. plasma physics. the study of highly ionized gases. plate tectonics


equal numbers of positive ions and electrons, exhibiting some properties of a gas but differing from a gas in being a good conductor of electricity and in being affected by a magnetic field. plasma physics. the study of highly ionized gases. plate tectonics. global tectonics based on a model of the earth characterized by a small number ( 10 - 25 ) of semirigid plates that float on some viscous underlayer in the mantle ; each plate moves more or ocr for page 152 152 glossary of physical terms less independently and grinds against the others, concentrating more deformation, volcanism, and seismic activity along the periphery. positive energy theorem. a recent theory that shows that in general relativity theory, any isolated system must have a positive value for its total energy. positron. an elementary particle having mass equal to that of the electron and having the same spin and statistics as the electron but a positive charge equal in magnitude to the electron ' s negative charge ; the antiparticle of the electron. positronium. the bound state of an electron and a positron. proton. a hadron that is the positively charged constituent of ordi - nary matter and, together with the neutron, is a building stone of all atomic nuclei ; its mass is approximately 938 mev. proton accelerator. a particle accelerator that accelerates protons to high energies, as opposed to one that accelerates heavier ions or electrons. pulsar. a celestial radio source, emitting intense short bursts of radio emission ; the periods of known pulsars range between 33 millisec - onds and 3. 75 seconds, and pulse durations range from 2 to about 150 milliseconds, with longer - period pulsars generally having a longer pulse duration. quantize. to restrict an observable quantity, such as energy or angular momentum, to a discrete set of values, to subdivide ( as energy ) into small but measureable increments. quantized hall effect. the appearance of quantum levels in the hall conductivity for a two - dimensional conductor in a magnetic field. quantum. for certain physical quantities, a unit such that the values of the quantity are restricted to integral multiples of this unit ( e. g., the quantum of angular momentum is planck ' s constant divided by 2 ~ ; an entity resulting from quantization of a field or wave, having particlelike properties such as energy ' mass, momentum, and angu - lar momentum (


., the quantum of angular momentum is planck ' s constant divided by 2 ~ ; an entity resulting from quantization of a field or wave, having particlelike properties such as energy ' mass, momentum, and angu - lar momentum ( e. ~., the photon is the quantum of an electromagnetic field, and the phonon is the quantum of a lattice vibration ). quantum chromodynamics. the quantum theory that describes the strong interactions that bind quarks together to form hadrons. quantum electrodynamics. the quantum theory of electromagnetic radiation, synthesizing the wave and corpuscular pictures, and of the interaction of radiation with electrically charged matter, in particular with atoms and their constituent electrons. quantum mechanics. the modern theory of matter, of electromag - netic radiation, and of the interaction between matter and radiation ; it differs from classical physics, which it generalizes and supersedes, mainly in the realm of atomic and subatomic phenomena. ocr for page 153 glossary of physical terms 153 quark. hypothetical elementary particles that have charges whose magnitudes are 1 / 3 or 2 / 3 of the electron charge ; quarks are thought to come in several types ( as up, down, strange, charmed, and bottom ) and are held to be a constituent of hadrons. quark - gluon model. the particle - physics model of the constituents of hadrons and the force that binds them ; see quantum chromodynam - ics. radiation pressure. the pressure exerted by electromagnetic radia - tion on objects on which it impinges. radio astronomy. the study of celestial objects by measurement and analysis of their emitted electromagnetic radiation in the wavelength range from roughly 1 millimeter to 30 meters. raman spectroscopy. nonlinear spectroscopy named for sir chandrasekhara venkata raman ( 1888 - 1970 ), indian physicist. relativistic magnetron. a device to produce microwaves that uses electrons moving at velocities near the speed of light in a magnetic field. renormalization group approach or theory. a mathematical tech - nique to avoid infinities that occur in certain classes of physical theories. resistivity. the electrical resistance offered by a material to the flow of current times the cross - sectional area of current flow and per unit length of current path ; the reciprocal of the conductivity. robotics. technology dealing with the design, construction, and operation of robots in automation. schwarzschild radius.


flow of current times the cross - sectional area of current flow and per unit length of current path ; the reciprocal of the conductivity. robotics. technology dealing with the design, construction, and operation of robots in automation. schwarzschild radius. for a given body of matter, a distance equal to the mass of the body times the gravitational constant divided by the square of the speed of light. second - order doppler elect. at velocities close to the speed of light, additional doppler effects may be detected even in cases where the source and observer are moving only transversely. semiconductor. a solid crystalline material whose electrical conduc - tivity is intermediate between that of a metal and an insulator, ranging from about 105 mhos to 10 - 7 mho per meter, and is usually strongly temperature dependent. semiconductor laser. a laser in which the wavelength of the coher - ent light beam is determined by a semiconductor compound. sidereal year. the time period relative to the stars of one revolution of the earth about the sun ; it is about 365. 2564 mean solar days. sigma - zero ( i ) particle. an unstable elementary particle of the baryon family, of neutral charge, with a mass about 1. 4 times the mass of the proton. ocr for page 154 154 glossary of physical terms soft x ray. an x ray having a comparatively long wavelength and poor penetrating power. solar mass. the mass of the sun, 2 x 103° kg. solar physics. the scientific study of all physical phenomena con - nected with the sun ; it overlaps with geophysics in the consideration of solar - terrestrial relationships such as the connection between solar activity and auroras. solid. a substance that has a definite volume and shape and resists forces that tend to alter its volume or shape ; a crystalline material, i. e., one in which the constituent atoms are arranged in a three - di - mensional lattice, periodic in three independent directions. solitonfsj. solitary waves ( as in a gaseous plasma ) that retain their phase and speed after colliding with each other. space charge. an electric charge distributed throughout a three - di -.. menslona ~. region. spectroscopy. the branch of physics concerned with the production, measurement, and interpretation of electromagnetic spectra arising from either emission or absorption of radiant energy by various substances. spin. the intrinsic angular momentum of a particle or nucleus, which exists even when the particle is at rest,


branch of physics concerned with the production, measurement, and interpretation of electromagnetic spectra arising from either emission or absorption of radiant energy by various substances. spin. the intrinsic angular momentum of a particle or nucleus, which exists even when the particle is at rest, as distinguished from orbital angular momentum. spin glass. a state of matter in which the magnetic spins of randomly located atoms freeze in direction at low temperature ; often general - ized to other systems. strong force. see strong interaction. strong interaction. one of the fundamental interactions of elemen - tary particles, primarily responsible for nuclear forces and other interactions among hadrons. substrate. the physical material on which a microcircuit is fabri - cated. superconducting magnet. an electromagnet whose coils are made of a superconductor with a high transition temperature and extremely high critical field ; it is capable of generating magnetic fields of 100, 000 oersteds and more with no steady power dissipation. superconductivity. a property of many metals, alloys, and chemical compounds at temperatures near absolute zero by virtue of which their electrical resistivity vanishes and they become strongly dia - magnetic. superdense. densities that are greater than that for an ordinary nucleus, such as may exist in the core of novae. ocr for page 155 glossar y of ph ysica ~ terms 1 5 5 supernova. a star that suddenly bursts into very great brilliance as a result of its blowing up ; it is orders of magnitude brighter than a nova. supersymmetry. a particle - physics theory that attempts to unite two particle classes of fermions and bosons into a unified theory. symmetry. the property of remaining invariant under certain changes ( as of orientation in space, of the sign of the electric charge, of parity, or of the direction of time flow ). synchrotron. a device for accelerating electrons or protons in closed orbits in which the frequency of the accelerating voltage is varied ( or held constant in the case of electrons ) and the strength of the magnetic field is varied so as to keep the orbit radius constant. tau particle lor tau lepton ( i. a short - lived elementary particle of the lep ton family that exists in positive and negative charge states and has a mass about 3500 times heavier than an electron. tectonics. a branch of geology concerned with structure, especially with folding and faulting. tera -. prefix meaning one trillion ( 10 ~


exists in positive and negative charge states and has a mass about 3500 times heavier than an electron. tectonics. a branch of geology concerned with structure, especially with folding and faulting. tera -. prefix meaning one trillion ( 10 ~ 21. tesla. unit of magnetic flux intensity equal to one weber per square meter ( 1 wb / m2 ), or one volt second per square meter ( 1 v s / m21. three - degree radiation. the remnant radiation, at microwave fre - quencies, of the big bang. tokamak. a device for confining plasma within a toroidal chamber, which produces plasma temperatures, densities, and confinement times greater than those produced by any other such device. tomography. a diagnostic technique using x - ray photographs in which the shadows of structures before and behind the section under scrutiny do not show. toroidal. of, relating to, or shaped like a torus ; doughnut - shaped. upsilon particle ( y ). any of a group of unstable electrically neutral mesons that have a mass about 10 times that of a proton. vacuum polarization. a process in which an electromagnetic field gives rise to virtual electron - positron pairs that effectively alter the distribution of charges and currents that generated the original electromagnetic field. valley of stability. the region on a chart of the nuclides where the majority of stable nuclides are found. w +. a positively charged boson with a mass about 87 times that of the proton that mediates the weak force. w -. the negatively charged counterpart to the w +. wave. a disturbance that propagates from one point in a medium to other points without giving the medium as a whole any permanent displacement. ocr for page 156 156 glossary of physical terms weak coupling. the coupling of four fermion fields in the weak interaction, having a strength many orders of magnitude weaker than that of the strong or electromagnetic interactions. weak force. see weak interaction. weak interaction. one of the fundamental interactions among ele - mentary particles responsible for beta decay of nuclei and for the decay of particles with lifetimes greater than about 10 - ~ ° second, such as muons, k mesons, and lambda hyperons ; it is several orders of magnitude weaker than the strong and electromagnetic interac - tions. x - ray astronomy. the study of x rays mainly from sources outside the solar system ; it includes the study of novae and supernovae in the milky way galaxy, together


over the past 38 years his holiness maharishi mahesh yogi has reformulated theancient vedic wisdom of life into a complete science of consciousness, his vedic scienceand technology. in doing so, maharishi has demonstrated that the literature of the vedictradition is not the work of different authors in various historical periods ; rather it is theprecise description of the unified source of nature ’ s orderliness, a self - interacting field of pure consciousness — pure wakefulness — that is the managing intelligence of the universe. maharishi describes this field as the most fundamental level of natural law, for all of thediverse laws of nature that give rise to and structure the vast material universe find their home within this unified field of intelligence. in addition, maharishi has brought to lightpractical procedures from the vedic tradition that enable anyone to directly experienceand unfold this most fundamental and powerful level of natural law in their own aware - ness. this he explains as the ultimate achievement, the blossoming of the total potentialof human life in higher states of consciousness. maharishi ’ s comments on the vedic literature, both in his writing as well as in manythousands of hours of lectures, have provided scholars and students with profound insightsinto the vedic literature as the theoretical and practical textbooks of consciousness. whilemaharishi has not commented upon every verse and in this vast body of literature, he nonetheless has provided sufficient understanding of its pervading themes. this paper will illustrate how maharishi ’ s comments on the vedic literature and his exposition of natural law can be used to show how the valm ¡ ki ramaya∆ unfolds one of its keythemes, the nature and practical application of is a concept of singular importance throughout the ramaya∆, for virtually allbehavior within the narrative is evaluated in terms of conformity or lack of conformity toit. modern scholars view as a collection of loosely codified behavioral codesdeeply rooted in the culture of ancient india and handed down from generation to gen - eration. however, maharishi provides a more profound understanding in his commentaryon another aspect of the vedic literature, the bhagavad - g ¡ ta. in maharishi ’ s commentary, on its most fundamental level is the total potential of natural law, the manag - ing intelligence of the entire universe ; on a more expressed level it represents the lawsof nature that uphold the evolution of all life throughout creation. when behavior is inaccord with


hydrogen : the essentials note that while hydrogen is normally shown at the top of the group 1 elements in the periodic table, the term " alkaline metal " refers to the group 1 elements from lithium downwards and not hydrogen. hydrogen is the lightest element. it is by far the most abundant element in the universe and makes up about about 90 % of the universe by weight. it is also the most abundant element in the earth ' s sun. hydrogen as water ( h2o ) is absolutely essential to life and it is present in all organic compounds. hydrogen is the lightest gas. hydrogen gas was used in lighter - than - air balloons for transport but is far too dangerous because of the fire risk ( hindenburg ). it burns in air to form only water as waste product and if hydrogen could be made on sufficient scale from other than fossil fuels then there might be a possibility of a hydrogen economy. hydrogen : historical information robert boyle ( 1627 - 1691 ; english chemist and physicist ) published a paper ( " new experiments touching the relation betwixt flame and air " ) in 1671 in which he described the reaction between iron filings and dilute acids which results in the evolution of gaseous hydrogen ( " inflammable solution of mars " [ iron ] ). however it was only much later that it was recognized as an element by henry cavendish ( 1731 - 1810 ; an english chemist and physicist who also independently discovered nitrogen ) in 1766 when he collected it over mercury and described it as " inflammable air from metals ". cavendish described accurately hydrogen ' s properties but thought erroneously that the gas originated from the metal rather than from the acid. hydrogen was named by lavoisier. deuterium gas ( 2h2, often written d2 ), made up from deuterium, a heavy isotope of hydrogen, was discovered in 1931 by harold urey, a professor of chemistry at chicago and california ( both usa ). sometime prior to the autumn of 1803, the englishman john dalton was able to explain the results of some of his studies by assuming that matter is composed of atoms and that all samples of any given compound consist of the same combination of these atoms. dalton also noted that in series of compounds, the ratios of the masses of the second element that combine with a given weight of the first element can be reduced to small whole numbers ( the law of multiple proportions ). this was further evidence for atoms. dalton ' s theory of atoms was published by thomas thomson in the 3rd edition of his


element that combine with a given weight of the first element can be reduced to small whole numbers ( the law of multiple proportions ). this was further evidence for atoms. dalton ' s theory of atoms was published by thomas thomson in the 3rd edition of his system of chemistry in 1807 and in a paper about strontium oxalates published in the philosophical transactions. dalton published these ideas himself in the following year in the new system of chemical philosophy. the symbol used by dalton for hydrogen is shown below. [ see history of chemistry, sir edward thorpe, volume 1, watts & co, london, 1914. ] in 1839 a british scientist sir william robert grove carried out experiments on electrolysis. he used electricity to split water into hydrogen and oxygen. he then argued one should be able to reverse the electrolysis and so generate electricity from the reaction of oxygen with hydrogen. he enclosed platinum strips in separate sealed bottles, one containing hydrogen and one oxygen. when the containers were immersed in dilute sulphuric acid a current indeed flowed between the two electrodes and water was formed in the gas bottles. he linked several of these devices in series to increase the voltage produced in a gas battery. later the term fuel cell was used by the chemists ludwig mond and charles langer. much later fuel cells were by nasa in the 1960s for the apollo space missions. fuel cells have been used for more than 100 missions in nasa spacecraft. fuel cells are also used in submarines. the lifting agent for the ill fated hindenberg ballooon was hydrogen rather than the safer helium. the image below is the scene probably in a way you have not seen it before. this is a " ray - traced " image reproduced with the permission of johannes ewers, the artist, who won first place with this image in the march / april 1999 internet raytracing competition. for details of ray - tracing you can ' t beat the pov - ray site. hydrogen : physical properties hydrogen : orbital properties isolation : in the laboratory, small amounts of hydrogen gas may be made by the reaction of calcium hydride with water. cah2 + 2h2o → ca ( oh ) 2 + 2h2 this is quite efficient in the sense that 50 % of the hydrogen produced comes from water. another very convenient laboratory scale experiment follows boyle ' s early synthesis, the reaction of iron filings with dilute sulphuric acid. fe + h2so4 → feso4 + h2 there are many industrial methods for the production of hydrogen and


exploring the multifunctional nature of activated carbon filtration granular activated carbon ( gac ) is commonly used for removing organic constituents and residual disinfectants in water supplies. this not only improves taste and minimizes health hazards, it protects other water treatment units such as reverse osmosis membranes and ion exchange resins from possible damage due to oxidation or organic fouling. activated carbon is a favored water treatment technique because of its multifunctional nature and the fact that it adds nothing detrimental to the treated water. most activated carbons are made from raw materials such as nut shells, wood, coal and petroleum. typical surface area for activated carbon is approximately 1, 000 square meters per gram ( m2 / gm ). however, different raw materials produce different types of activated carbon varying in hardness, density, pore and particle sizes, surface areas, extractables, ash and ph. these differences in properties make carbons often preferable over other methods in various applications. the two principal mechanisms by which activated carbon removes contaminants from water are adsorption and catalytic reduction. organics are removed by adsorption and residual disinfectants are removed by catalytic reduction. factors that affect the performance of activated carbon are organic material in public water supplies comes from decaying plant life, which becomes more soluble in water over time and exists as large, high - molecular weight organic acids ( non - polar weak acids ). eventually, smaller molecular weight acids of varying sizes form. typical organic acid molecules range in molecular weight from a few hundred to tens of thousands. the size, number and chemical structure of organic acid molecules depend on a large number of factors including water ph and temperature. accordingly, there exists an almost infinite number of organic acids. as a result, removing organics can be difficult and is always site - specific. activated carbon ' s adsorptive properties are used to remove organics. generally, adsorption takes place because all molecules exert forces to adhere to each other. activated carbon adsorbs organic material because the attractive forces between the carbon surface ( non - polar ) and the contaminant ( non - polar ) are stronger than the forces keeping the contaminant dissolved in water ( polar ). the adsorptive forces are weak and cannot occur unless the organic molecules are close to the carbon ' s surface. the large surface area of the activated carbon, due to its particle size and pore configuration, allows for the adsorption to take place. factors that decrease solub


conditions of use i chose oxygen because it ’ s what we breathe and i thought it was interesting. oxygen was discovered by joseph priestly in 1774. the atomic number : 8, the atomic mass : 15. 9994 amu. the melting point is : - 218. ( 54. 750008 k, - 361. 12 ) the boiling point is : - 183. 0 ( 90. 15 k, - 297. ) oxygen does not have a freezing point. joseph priestly was born : march 13, 1733 in a country near england. he died february 6, 1804. joseph was in the fields of science. i chose helium because its one of the dangerous elements. helium was discovered by sir william ramsay in 1895. the atomic number is 2, the atomic mass : 4. 002602 amu. the melting point is : - 272. 0 ( 1. 15 k, - 457. ). the boiling point is : - 268. 93. helium does not have a freezing point because it is a gas. helium was discovered by sir william ramsay. sir william ramsay was born october 2, 1852. he died july 23, 1916. he will be remembered forever i chose sodium because i thought it was interesting. sir humphrey davey discovered sodium. the atomic number of sodium is 11. the symbol of sodium is na. the melting point of sodium is 97. 81. the boiling point is 882.. sodium is used in glass. it is created in nature. article posted may 22, 2012 at 12 : 35 pm • comment • reads 205 see all articles