are gamma rays? a gamma ray is a packet of electromagnetic energy - - a photon. gamma photons are the most energetic photons in the electromagnetic spectrum. gamma rays ( gamma photons ) are emitted from the nucleus of some unstable ( radioactive ) atoms. what are the properties of gamma radiation? gamma radiation is very radiation. gamma photons have about 10, 000 times as much energy as the photons in the visible range of the electromagnetic spectrum. gamma photons have no mass and no electrical charge - - they are pure because of their high energy, gamma photons travel at the speed of light and can cover hundreds to thousands of meters in air before spending their energy. they can pass through many kinds of materials, including human tissue. very dense materials, such as lead, are commonly used as shielding to slow or stop gamma photons. their wave lengths are so short that they must be measured in nanometers, billionths of a meter. they range from 3 / 100ths to 3 / 1, 000ths of a nanometer. what is the difference between gamma rays and x - rays? gamma rays and x - rays, like visible, infrared, and ultraviolet light, are part of the electromagnetic spectrum. while gamma rays and x - rays pose the same hazard, they differ in their origin. gamma rays originate in the nucleus. x - rays originate in the electron fields surrounding the what conditions lead to gamma ray emission? emission occurs when the nucleus of a radioactive atom has too much energy. it often follows the emission of what happens during gamma provides an example of radioactive decay by gamma radiation. scientists think that a neutron transforms to a proton and a beta particle. the additional proton changes the atom to barium - 137. the nucleus ejects the beta particle. however, the nucleus still has too much energy and ejects a gamma photon ( gamma radiation ) to become more stable. how does gamma radiation change in the environment? gamma rays exist only as long as they have energy. once their energy is spent, whether in air or in solid materials, they cease to exist. the same is true for x - rays. how are people exposed to most people ' s primary source of gamma exposure is naturally occurring radionuclides, particularly potassium - 40, which is found in soil and water, as well as meats and high - potassium foods such as bananas. radium is also a source of gamma exposure. however, the increasing use of nuclear medicine ( e. g., bone, thyroid, and lung scans )


" that ' s not what i meant " : human communication is fraught with misinterpretation. written out in longhand, words and letters can be misread. a telegraph clerk can mistake a dot for a dash. noise will always be with us, but at least a new jqi ( * ) device has established a new standard for reading quantum information with a minimum of uncertainty. success has come by viewing light pulses not with a single passive detector with but an adaptive network of detectors with feedback. the work on jqi ' s new, more assured photonic protocol was led by francisco becerra and carried out in alan migdall ' s jqi lab. they report their results in nature photonics ( * * ). here are some things you need to know to appreciate this development. how to modulate? digital data, in its simplest form, can be read with a process called on - off keying : a detector senses the intensity of incoming bursts of electrons in wires or photons through fibers and assigns a value of 0 or 1. a more sophisticated approach to modulating a signal ( not merely off / on ) is to encode data in the phase of the pulse. in " phase - shift keying, " information is encoded in the amount of phase shift imposed on a carrier wave ; the phase of the wave is how far along the wave cycle you happen to be ( say, at the top of a crest or the bottom of a trough in a sinusoidal, as in this figure ). what kind of alphabet? larger words can be assembled from a small suite of symbols. the roman alphabet has 26 letters, the greek only 24. binary logic, and most transistors, makes do with just a two - letter alphabet. everything is a 0 or a 1, and larger numbers and letters and words are assembled from as many binary bits as are necessary. but what if we enlarged the alphabet from two to four? in quaternary logic more data can be conveyed in a single pulse. the cost of this increase is having to write and read 4 states of modulation ( or 4 symbols ). even more efficient in terms of packing data, but correspondingly more difficult to implement, is logic based on 6 states, or 8, or any higher number. digital data at its most basic - - - at the level of transistor - - - remains in binary form, but for communicating this data, higher number alphabets can be used. in fact, high - definition television delivery


any higher number. digital data at its most basic - - - at the level of transistor - - - remains in binary form, but for communicating this data, higher number alphabets can be used. in fact, high - definition television delivery already involves high - level logic. no matter what kind of logic is used, errors creep in. a detector doesn ' t just unequivocally measure a 0 or a 1. the reading process is imperfect. and even worse, the state of the light pulse is inherently uncertain, and that is a real problem when the light pulses belong to a set of overlapping states. this is illustrated in the figure below for binary and quaternary phase states. on the left side of the figure, the measurement of the phase of a light pulse is depicted, where there are only two choices. is the pulse in the alpha state or the – alpha state? because the tails of one overlap the other there is a slight ambiguity that leads to uncertainty in which state a measurement indicates. on the right, four possible states are depicted on a complex - number graph ( with real ( re ) and imaginary ( im ) axes ). here the overlap of the states is more complicated, but results in similar ambiguities of the measured states, seen mostly near the borders ( decision threshold lines ) between the states. standard quantum limit decades ago communications theory established a minimal uncertainty for the accurate transmission and detection of information encoded in overlapping states. the hypothetical minimal detection error using conventional schemes is called the standard quantum limit and it depends on things like how many photons of light comprise the signal, how many levels ( binary, quaternary, etc. ) need to be read out, and which physical property of light is used to encode the information, such as the phase. but starting in the 1970s with physicist carl w. helstrom, some scientists have felt that the standard quantum limit could be circumvented. the jqi researchers do exactly this by using not a single passive photo - detector, but an active detection process involving a series of stages. at each stage, the current light signal strikes a partially - silvered mirror, which peels off a fraction of the pulse for analysis and the rest goes on to subsequent stages. at each stage the signal is combined with a separate reference oscillator wave used as a phase reference against which the signal phase is determined. this is done by shifting the reference wave by a known amount and letting it interfere with the signal wave at the beamspl


the signal is combined with a separate reference oscillator wave used as a phase reference against which the signal phase is determined. this is done by shifting the reference wave by a known amount and letting it interfere with the signal wave at the beamsplitter. by altering that known shift, the interference pattern can reveal something about the phase of the input pulse. by combining many such stages ( see the figure below ) and using information gained by previous stages to adjust the phase of the reference wave in successive stages, a better estimate of the signal phase can be obtained. detecting phase in this adaptive way, and implemented in a feedback manner, the jqi system is able to beat the standard quantum limit for a set of 4 states ( quaternary ) encoding information as a phase. these states are represented as fuzzy distributions arranged at different angles around a circle as seen in the figure above where the angles represent the phase of the light pulses. the jqi noise - reduction achievement is depicted in the graph below. the error rate is plotted as a function of the mean number of photons used to deliver the information. the standard quantum limit ( sql ) is the red line. the light gray line is the sql line if you take into account that individual photon detector stages used were ~ 72 % efficient rather than 100 % ( with the detector efficiencies being 84 %. in the business of detecting single photons, 84 % is top of the line. ) the error probabilities measured for the system ( black points with error bars ) fall well below the quantum limit, by about 6 decibels in the center of the curve. this is equivalent to saying that the jqi receiver is performing better than the sql by a factor of about 4 in determining the phase of an incoming signal. that is, the jqi receiver achieves an error probability that is 4 times lower than the so - called " standard quantum limit. " this graph shows results for a system that implements 10 adaptive measurements. the two other lines on the chart show what the expected uncertainty would be for a perfect system ( 100 % efficient detectors ) and without any of the imperfections that would be encountered in any realistic implementation, and a hypothetical ultimate - limit on uncertainty derived by helstrom. to conclude, the jqi photon receiver features an error rate four times lower than perfect conventional receivers, over a wide range of photon number, and with discrimination for four states. the only previous detection below the quantum limit was for a very narrow range of photons and with only a 2


receiver features an error rate four times lower than perfect conventional receivers, over a wide range of photon number, and with discrimination for four states. the only previous detection below the quantum limit was for a very narrow range of photons and with only a 2 - state protocol and only slightly below the sql. ( * ) the joint quantum institute ( jqi ) is operated jointly by the national institute of standards and technology in gaithersburg, md and the university of maryland in college park. ( * * ) " experimental demonstration of a receiver beating the standard quantum limit for multiple nonorthogonal state discrimination, " by f. e. becerra, j. fan, g. baumgartner, j. goldhar, j. t. kosloski, and a. migdall, nature photonics, published online 6 january 2013. alan migdall, firstname. lastname @ example. org, 301 - 975 - 2331 press contact at jqi : phillip f. schewe, email @ example. com, 301 - 405 - 0989. http : / / jqi. umd. edu / phillip f. schewe | source : eurekalert! further information : www. umd. edu more articles from physics and astronomy : “ out of this world ” space stethoscope valuable on earth, too 22. 05. 2013 | johns hopkins storms on uranus, neptune confined to upper atmosphere 21. 05. 2013 | university of arizona a fried breakfast food popular in spain provided the inspiration for the development of doughnut - shaped droplets that may provide scientists with a new approach for studying fundamental issues in physics, mathematics and materials. the doughnut - shaped droplets, a shape known as toroidal, are formed from two dissimilar liquids using a simple rotating stage and an injection needle. about a millimeter in overall size, the droplets are produced individually, their shapes maintained by a surrounding springy material made of polymers. droplets in this toroidal shape made... frauhofer fep will present a novel roll - to - roll manufacturing process for high - barriers and functional films for flexible displays at the sid displayweek 2013 in vancouver – the international showcase for the display industry. displays that are flexible and paper thin at the same time?! what might still seem like science fiction will be a major topic at the sid display week 2013 that currently takes place in vancouver in canada. high manufacturing cost and a short lifetime are still a major


that are flexible and paper thin at the same time?! what might still seem like science fiction will be a major topic at the sid display week 2013 that currently takes place in vancouver in canada. high manufacturing cost and a short lifetime are still a major obstacle on... university of wurzburg physicists have succeeded in creating a new type of laser. its operation principle is completely different from conventional devices, which opens up the possibility of a significantly reduced energy input requirement. the researchers report their work in the current issue of nature. it also emits light the waves of which are in phase with one another : the polariton laser, developed... innsbruck physicists led by rainer blatt and peter zoller experimentally gained a deep insight into the nature of quantum mechanical phase transitions. they are the first scientists that simulated the competition between two rival dynamical processes at a novel type of transition between two quantum mechanical orders. they have published the results of their work in the journal nature physics. “ when water boils, its molecules are released as vapor. we call this... researchers have shown that, by using global positioning systems ( gps ) to measure ground deformation caused by a large underwater earthquake, they can provide accurate warning of the resulting tsunami in just a few minutes after the earthquake onset. for the devastating japan 2011 event, the team reveals that the analysis of the gps data and issue of a detailed tsunami alert would have taken no more than three minutes. the results are published on 17 may in natural hazards and earth system sciences, an open access journal of... 22. 05. 2013 | life sciences 22. 05. 2013 | ecology, the environment and conservation 22. 05. 2013 | earth sciences 17. 05. 2013 | event news 15. 05. 2013 | event news 08. 05. 2013 | event news


string theorists had looked at the idea of confining all forces to a brane and having gravity leak, but they had not worked out the mechanism, says physicist joseph lykken of fermilab in batavia, ill. randall and sundrum, he remarks, " changed people ' s thinking about this stuff entirely. " as randall and sundrum refined their idea, they realized that if the extra dimension of spacetime were warped in anti - de sitter fashion, it could be infinitely large and what we observe about gravity could still be true. this model came to be known as rs - 2. " working that out was mind - blowing, " sundrum recalls. " we had reason to be dead scared. in each of these cases, there was a distinct fear of making complete fools of ourselves. " " it was counterintuitive, " notes theorist michael j. duff of imperial college london. " it came as a surprise even to those working in extra dimensions that even though the extra dimension is very large, we wouldn ' t be aware of it. newton ' s law would still be an inverse square law, not an inverse cube law, which is what you might naively expect. " it took a while for many physicists to realize what randall and sundrum were suggesting, but the time was right for such thinking. anti - de sitter space was popping up in some models, branes were thriving, and in 1998 nima arkani - hamed of harvard, georgi dvali of new york university and savas dimopoulos of stanford university ( or add, for short ) had postulated a three - brane within two large extra dimensions. randall and sundrum offered a new set of options of what went on in the early universe. some of the recent models, be they rs, elaborations of add or others, will be put to the test when the large hadron collider ( lhc ) at cern near geneva fires up in 2007. " if there is any solution to the hierarchy problem, it should be revealed at the energies the lhc will explore, " randall enthuses. evidence could include gravitons, supersymmetric partners or evanescent, tiny black holes. " even if we don ' t know the answer, it should tell us what the answer is, " she adds. in typical fashion, randall recently took on two things new to her. the first was writing a book about physics, released last month. the second


history plastic as invention is attributed to leo hendrik baekeland sold the first one called bakelite in 1909. throughout the twentieth century the use of plastic became extremely popular and came to replace other traditional materials in both the domestic, industrial and comercial. propiedades and features plastic bags coca - cola bottle plastic. plastics are composed of organic macromolecules substances called polymers. these polymers are large groups of monomers linked by a chemical process called polymerization. plastics provide the necessary balance of properties that can not be achieved with other materials such as : color, light weight, nice touch and resistance to environmental degradation and biologica. de fact, plastic refers to a condition of the material, but not material itself : synthetic polymers commonly called plastics are actually synthetic materials that can reach the plastic state, ie when the material is viscous or fluid, and has properties of resistance to mechanical stress. this state is reached when the material becomes solid plastic state usually by heating, and is ideal for different production processes and that this state is when the material can be handled in the forms that exist today. so the word plastic is a way to refer to synthetic materials capable of entering into a plastic state, but plastic is not necessarily the group of material that is routinely referred palabra. son characteristic properties of most plastics, but not always met in certain special plastic : they are cheap ( they have a low cost in the market ). densidad. existen they have low permeable and impermeable plastic material, dissemination of materials electricos. son termoplasticos. son insulating thermal insulation, but most do not elevadas. su resist burning temperatures contaminante. son is resistant to corrosion and be at the intemperie. resisten many factors are recycled quimicos. algunos better than others, they are not biodegradable or easy to trabajar. procesos easy reciclar. son development the first part of the production of plastics is the production of polymers in the chemical industry. today, the recovery of post - consumer plastic is also essential. part of the industry - finished plastic directly used as grain or resin. more often, they use various forms of molding ( injection, compression, rotation, inflation, etc.. ) or the extrusion of profiles or wires. part of the largest plastics processing machinery is made in a plastics horneadora. clasificacion you can qualify for the plastics into several categories : according to


free encyclopedia jump to : navigation, search the term plastic in its broader meaning applies to substances of different structures that lack a fixed point of boiling and held over a temperature range elasticity and flexibility properties that allow mold them and adapt to different forms and applications. however, in the narrow sense, is that denotes certain types of synthetic materials obtained by polymerization phenomena or artificial propagation of carbon atoms in the long molecular chains of organic compounds derived from petroleum and other natural substances. the word plastic was originally used as an adjective to denote a degree of mobility and easy to acquire some form, meaning that remains in the term plasticity. the invention of the first plastic arises as a result of a competition held in 1860, when the u. s. manufacturer of billiard balls and collard phelan offered a reward of $ 10, 000 who get a substitute for natural ivory, for the manufacture of billiard balls. one of the people who competed was the american inventor john wesley hyatt, who developed the film dissolving cellulose ( natural material ) in a solution of camphor and ethanol. while hyatt did not win the prize, got a very marketable product that would be vital for the further development of the film industry of late nineteenth - s. in 1909 american chemist leo hendrik baekeland belgian origin synthesized a polymer of high commercial interest, from molecules of phenol and formaldehyde. it gave the name of bakelite and was the first totally synthetic plastic ever, was the first of a series of synthetic resins, which revolutionized modern technology by starting the " plastic era. " throughout the twentieth century the use of plastic became extremely popular and came to replace other materials in both the domestic, industrial and commercial. in 1920 there was an event that would set the pace in the development of plastics. the german chemist hermann staudinger ventured that they were in fact composed of giant molecules or macromolecules. efforts to test these claims initiated many scientific research that produced enormous advances in this part of chemistry. properties and characteristics plastics are organic substances formed by macrocells called polymers. these polymers are large groups of monomers linked by a chemical process called polymerization. plastics provide the necessary balance of properties that can not be achieved with other materials such as : color, light weight, nice touch and resistance to environmental and biological degradation. in fact, plastic refers to a condition of the material, but not the material itself : the synthetic polymers commonly called plastics are actually synthetic materials that can reach the plastic state


: color, light weight, nice touch and resistance to environmental and biological degradation. in fact, plastic refers to a condition of the material, but not the material itself : the synthetic polymers commonly called plastics are actually synthetic materials that can reach the plastic state, ie when the material is viscous or fluid, and no resistance properties to mechanical stress. this state is reached when the material becomes solid plastic state usually by heating, ideal for different production processes and that this state is when the material can be handled in the forms that exist today. so the word plastic is a way to refer to synthetic materials capable of entering into a plastic state, but plastic is not necessarily the group of everyday materials to which this word refers. the properties and characteristics of most plastics ( though not always fulfilled in certain special plastics ) are these : * easy to work and shape, * have a low production cost, * have low density * tend to be waterproof, * good electrical insulators, * acceptable acoustic insulation, * good thermal, although most can not withstand very high temperatures * resistant to chemical corrosion and many factors ; * some are not biodegradable or easily recyclable, and if they are burned, are highly polluting. the first part of the production of plastics is the production of polymers in the chemical industry. today, the recovery of post - consumer plastic is also essential. part of the industry - finished plastic directly used as grain or resin. more often, they use various forms of molding ( injection, compression, rotation, inflation, etc.. ) or the extrusion of profiles or wires. part of the largest plastics processing is done on a machine horneadora. classification of plastics according to the base monomer this classification is considered the origin of the monomer from which part of the polymer production. * natural : these are polymers whose monomers are derived from natural products with certain characteristics, eg, cellulose, casein, and rubber. in two of these examples there are other plastic which is obtained from : or cellulose derivatives are : the celluloid, cellophane and cellon. o rubber products are the rubber and ebonite. * synthetic : those that have their origin in man - made products, mainly petroleum products such as polyethylene bags according to their behavior in heat a thermoplastic is a plastic that, at room temperature, is plastic or deformable, it becomes a liquid when heated and hardens into a glassy state when cooled sufficiently. most


##ethylene bags according to their behavior in heat a thermoplastic is a plastic that, at room temperature, is plastic or deformable, it becomes a liquid when heated and hardens into a glassy state when cooled sufficiently. most thermoplastics are high molecular weight polymers, those with associated chains via weak van der waals forces ( polyethylene ) ; strong dipole - dipole interactions and hydrogen bonding, or even stacked aromatic rings ( polystyrene ). thermoplastic polymers differ from thermosetting polymers that after being heated and molded to form they can overheat and other objects, as in the case of thermoset or thermoduric, its shape after cooling does not change and the preferred fire.. its physical properties change gradually if they melt and shape several times. the main ones are : * cellulosic resins : derived from cellulose, the material component of the woody part of plants. belongs to this group rayon. * polyethylenes and derivatives used as raw materials for ethylene obtained from oil cracking, discussed later, allows for different monomers such as vinyl acetate, vinyl alcohol, vinyl chloride, etc.. this part pvc, polystyrene, acrylic, etc.