one or more kilograms of plutonium, excluding that contained in sealed sources and welded or otherwise sealed unirradiated or irradiated fuel rods, at the plant, including any of the following processes : ( i ) preparation of fuel material ; ( ii ) formation of fuel material into desired shapes ; ( iii ) application of protective cladding ; ( iv ) recovery of scrap material ; and ( v ) storage associated with such operations ; or ( 2 ) research and development activities involving any of the operations described in paragraph ( h ) ( 1 ) of this section, except for research and development activities where the operator is licensed to possess or use plutonium in amounts less than those specified in paragraph ( h ) ( 1 ). ( i ) source material means source material as defined in the regulations contained in part 40 of this chapter. ( j ) special nuclear material means : ( 1 ) plutonium, uranium 233, uranium enriched in the isotope 233 or in the isotope 235, and any other material which the commission, pursuant to the provisions of section 51 of the act, determines to be special nuclear material, but does not include source material ; or ( 2 ) any material artifically enriched by any of the foregoing, but does not include source material. ( k ) testing reactor means a nuclear reactor which is of a type described in § 50. 21 ( c ) of this chapter and for which an application has been filed for a license authorizing operation at : ( 1 ) a thermal power level in excess of 10 megawatts ; or ( 2 ) a thermal power level in excess of 1 megawatt, if the reactor is to contain : ( i ) a circulating loop through the core in which the applicant proposes to conduct fuel experiments ; or ( ii ) a liquid fuel loading ; or ( iii ) an experimental facility in the core in excess of 16 square inches in cross - section. ( l ) department means the department of energy established by the department of energy organization act ( pub. l. 95 - 91, 91 stat. 565, 42 u. s. c. 7101 et seq. ), to the extent that the department, or its duly authorized representatives, exercises functions formerly vested in the u. s. atomic energy commission, its chairman, members, officers and components and transferred to the u. s. energy research and development administration and to the administrator thereof pursuant to sections 104 ( b ), ( c ) and ( d ) of the energy reorganization act of 1974 ( pub. l. 93 - 438


environment ) in different ways : 1 ) thermally, when a warmer object is in contact with a cooler one ; 2 ) mechanically, when two objects push or pull on each other over a distance ; 3 ) electrically, when an electrical source such as a battery or generator is connected in a complete circuit to an electrical device ; or 4 ) by electromagnetic waves. 9 - 12 : 4f / h1. the change in motion ( direction or speed ) of an object is proportional to the applied force and inversely proportional to the mass. 8. the designed world 8b. materials and manufacturing 6 - 8 : 8b / m2. manufacturing usually involves a series of steps, such as designing a product, obtaining and preparing raw materials, processing the materials mechanically or chemically, and assembling the product. all steps may occur at a single location or may occur at different locations. 11. common themes 6 - 8 : 11a / m2. thinking about things as systems means looking for how every part relates to others. the output from one part of a system ( which can include material, energy, or information ) can become the input to other parts. such feedback can serve to control what goes on in the system as a whole. 6 - 8 : 11a / m3. any system is usually connected to other systems, both internally and externally. thus a system may be thought of as containing subsystems and as being a sub - system of a larger system. 9 - 12 : 11a / h2. understanding how things work and designing solutions to problems of almost any kind can be facilitated by systems analysis. in defining a system, it is important to specify its boundaries and subsystems, indicate its relation to other systems, and identify what its input and output are expected to be. < a href = " http : / / www. thephysicsfront. org / items / detail. cfm? id = 11753 " > institute of electrical and electronics engineers. dean kamen ' s artificial arm. institute of electrical and electronics engineers, june 30, 2011. < / a > dean kamen ' s artificial arm. ( 2011, june 30 ). retrieved june 19, 2013, from institute of electrical and electronics engineers : http : / / spectrum. ieee. org / video / biomedical / bionics / dean - kamens - artificial - arm institute of electrical and electronics engineers. dean kamen ' s artificial arm. institute of electrical and electronics engineers, june 30, 2011. http : / / spectrum. ieee. org / video


website detail page published by the annenberg channel these eight free professional development workshops for k - 8 teachers present science concepts on the nature of light and its behavior. each workshop is structured around a one - hour video that features footage of a complete science lesson by a master teacher. as each lesson unfolds, science and education experts provide commentary to expand on key points. graphics, animations, and video demonstrations provide background information on reflection, refraction, color, human vision, light energy, and more. the workshops are designed so that teachers come away with an understanding that will help them engage students in their own explorations. this resource also includes a series of self - tests to gauge understanding. the workshop videos may be viewed at no cost online. registered users may also participate in forums and teacher talk email lists. dvd ' s are available on the website at an additional cost. teachers who participate in the entire workshop series are eligible for two graduate credits from colorado state university ( tuition applies ). see related materials for a link to course enrollment information. please note that this resource requires flash. compadre is beta testing citation styles! disclaimer : compadre offers citation styles as a guide only. we cannot offer interpretations about citations as this is an automated procedure. please refer to the style manuals in the citation source information area for clarifications. citation source information the apa style presented is based on information from apa style. org : electronic references. the chicago style presented is based on information from examples of chicago - style documentation. the mla style presented is based on information from the mla faq. science in focus : shedding light on science : is associated with shedding light workshops : graduate credit this link takes you to the course enrollment page to pursue graduate credit for the annenberg media series " science in focus : shedding light on science ". ( 2 credit hours offered by colorado state university. ) relation by caroline hall accompanies science in focus : force and motion workshops a set of eight video - based workshops by the same publisher on the topic of force & motion. relation by caroline hall accompanies science in focus : energy a set of eight video - based workshops by the same publisher on the topic of energy and how to teach it in grades k - 8. relation by caroline hall know of another related resource? login to relate this resource to it. is associated with


hydrogen fuel cells are an appealing source of clean energy because they have the potential to power anything that uses electricity — from computers and cell phones to cars and ships — without toxic emissions. thayumanavan, who is an authority on charge transport and molecular design, was recently chosen as the campus ’ s first spotlight scholar in recognition of his research and innovation in clean energy science. thayumanavan co - directs the massachusetts center for renewable energy science and technology ( masscrest ). with colleagues ryan hayward, polymer science, and mark tuominen, physics, he discovered a new material that improves charge transport — a key energy - generating process for efficient and affordable hydrogen fuel cell design. using a polymer nanostructure that provides an excellent conduit for transporting protons from one side of a fuel cell membrane to another, they demonstrated how to improve proton conductivity under very low humidity conditions, where fuel cells prefer to operate but where few materials perform well. hydrogen fuel cells are an appealing source of clean energy because they have the potential to power anything that uses electricity — from computers and cell phones to cars and ships — without toxic emissions. the discovery could lead to commercial development of fuel cell membranes that stay chemically and mechanically stable much longer than current materials allow. the results are so promising that thayumanavan received $ 40, 000 from the massachusetts clean energy center to help demonstrate the technology ’ s viability. “ our work should lead to a lighter, more efficient and sustainable source of clean power, ” says thayumanavan. thayumanavan, who came to umass amherst in 2003, earned high praise from spotlight scholar nominators for his multi - faceted work, noting that his research in molecular design is also relevant to the life sciences. he ’ s created a nanoscopic gel that can effectively encapsulate and then release drug molecules inside cells. such a feature is useful in selectively delivering chemotherapeutic drug molecules to cancer cells. the campus ’ s technology transfer office and thayumanavan are pursuing commercial venture opportunities for bringing this technology to clinical trial.


the layout of nuclear facilities in iran nuclear iran : a glossary of terms april 2013 update international diplomacy concerning iranis nuclear program continues to center on the countryis compliance with agreements designed to ensure that peaceful nuclear work is not used as a cover for the develop = ment of nuclear weapons. the challenge of discovering what may be going on in iran is difficult not only because of tehranis obstructionism, but also because the same technologies, particularly uranium enrichment and spent fuel reprocessing, can be used for both civilian and military purposes. this policy focus is intended to improve comprehension of the main issues and important technical details surrounding the program. the core of the document explains the terms used by the international atomic energy agency ( iaea ), the worldis watchdog in ensuring that nuclear science and technology are used for peaceful purposes only. separate sections offer explanations of basic nuclear terms and the use of centrifuges for uranium enrichment. in addition, because some of iranis technology came from nuclear - armed pakistan, another section is devoted to explaining the main portions of islamabadis program. and since media coverage often compares sus = pected iranian nuclear work to initial u. s. development of atomic weapons in the mid - 1940s, the basic terms often used in describing this history are defined separately. in addition, this online report includes an interactive index that provides quick, hyperlinked access to all of the terms discussed in the various glossaries. by clicking on a term in this index, users can instantly jump to the page on which it appears, then click another link to return to the index. simon henderson is the baker fellow and director of the gulf and energy policy program at the washington institute. he has lived in both pakistan and iran and has written extensively on nuclear proliferation. olli heinonen, a senior fellow at harvard kennedy school ' s belfer center for science and international affairs, previously served as deputy director - general and head of the department of safeguards at the international atomic energy agency in vienna, inspecting facilities in iran and other countries. watch online as institute proliferation expert simon henderson and former iaea deputy director - general olli heinonen share a new study on the iranian nuclear program and international responses and discuss the latest developments ahead of a key iaea report on tehran ' s atomic activities. - nuclear iran glossary. pdf ( 3. 3 mb pdf ) for more information about this publication please contact the belfer center communications office at 617 - 495 - 9858. full text of this publication is available at : for


being a functionalist, and carefully distinguished his concept of function from that of malinowski, who openly advocated functionalism. while malinowski ' s functionalism claimed that social practices could be directly explained by their ability to satisfy basic biological needs, radcliffe - brown rejected this as baseless. instead, influenced by the process philosophy of alfred north whitehead, he claimed that the fundamental units of anthropology were processes of human life and interaction. because these are by definition characterised by constant flux, what calls for explanation is the occurrence of stability. why, radcliffe - brown asked, would some patterns of social practices repeat themselves and even seem to become fixed? he reasoned that this would at least require that other practices must not conflict with them too much ; and that in some cases, it may be that practices grow to support each other, a notion he called ' coadaptation ', deriving from the biological term. functional analysis, then, was just the attempt to explain stability by discovering how practices fit together to sustain that stability ; the ' function ' of a practice was just its role in sustaining the overall social structure, insofar as there was a stable social structure ( radcliffe - brown 1957 ). this is far from the ' functional explanation ' later impugned by carl hempel and others. it is also clearly distinct from malinowski ' s notion of function, a point which is often ignored by radcliffe - brown ' s detractors. while levi - strauss ( 1958 ) claimed that social structure and the social relations that are its constituents are theoretical constructions used to model social life, radcliffe - brown only half - agreed. he argued ( 1957 ) that social relations are real, and even directly observable ; but that social structure is a theoretical construction posited by the scientist on the basis of his or her observation of social relations. he shared with levi - strauss the notion that a major goal of social anthropology was to identify social structures and formal relationships between them, and that qualitative or discrete mathematics would be a necessary tool to do this. in that sense radcliffe - brown may be considered one of the fathers of social network analysis. in addition to identifying abstract relationships between social structures, radcliffe - brown argued for the importance of the notion of a ' total social structure ', which is the sum total of social relations in a given social unit of analysis during a given period. the identification of ' functions ' of social practices was supposed to be relative to this total social structure. levi - strauss saw social structure as a model. a


the universe together ; until we actually detect cold dark matter particles, it will be difficult to argue that cosmology is solved. experiments designed to detect the dark matter that holds are own galaxy together are now operating with sufficient sensitivity to detect both neutralinos and axions. in addition, experiments at particle accelerators ( fermilab and cern ) will be hunting for the neutralino and its other - nature of the dark energy. if the universe is indeed accelerating, then most of the critical density exists in the form of dark energy. this component is poorly understood. vacuum energy is only the simplest possibly for the smooth dark component ; there are other possibilities : frustrated topological defects or an evolving scalar field ( see e. g., caldwell et al, 1998 ; turner & white, 1997 ). independent evidence for the existence of this dark energy, e. g., by cmb anisotropy, the sdss and 2df surveys, or gravitational lensing, is crucial for verifying the accounting of matter and energy in the universe i have advocated. additional measurements of sne1a could help shed light on the precise nature of the dark energy. the dark energy problem is not only of great importance for cosmology, but for fundamental physics as well. whether it is vacuum energy or quintessence, it is a puzzle for fundamental physics and possibly a clue about the unification of the forces and particles.


january 17, 2006 homework syllabus for all sect consider the following algorithm for getting a drink of water in an apartment in which n roomates share n cups. procedure get - drink ( dirty : int, clean : int, n : int ) if ( clean = 0 ) then for ( j = 1 to n ) do wash - cup ( j ) ; dirty = 0 ; clean = n ; return ( dirty + 1, clean - 1, n ) question 1 use the accounting trick method to show that this algorithm runs in amortized constant time ( meaning that it is o ( 1 ) when using amortized anlaysis ). how many " tokens " will you deposit with each procedure call? which instruction will you pick as the barometer instruction to measure withdrawals on each function call? can you prove that the account will never go negative? question 2 suppose that rather than using the get - drink algorithm above, the roomates decided to implement a " you use it, then you wash it " policy instead. under policy, one would get a drink of water then immediately wash the cup so that all cups were clean at all times. compare and contrast the amount of time required to get a drink of water under both policies. how does this related to the design of algorithms and data structures? question 3 problem 4. 19 page 142 question 4 problem 6. 1 page 214 note : problem 6. 2 and the question about nephite coinage were moved to homework # 4 for jan. 23 ( so if you started them already, you are still ahead on your homework ). posted by jones at january 17, 2006 12 : 03 pm post a comment thanks for signing in,. now you can comment. ( sign out ) ( if you haven ' t left a comment here before, you may need to be approved by the site owner before your comment will appear. until then, it won ' t appear on the entry. thanks for waiting. )


will be waiting for you at the entrance. upon arrival, you walk up to him and say “ hello ”. he looks at you with puzzled eyes. you realize that your boss has not told you what language he speaks. you say “ guten tag ”. no reponse. you say “ bonjour ” no response. you finally say “ buenos dias ”. his eyes light up and he says “ ah, buenos dias, como esta usted? ” you shake hands. you show each other your id badges and start talking. in social situations, we don ’ t usually just walk up to someone and start talking. we usually say hello and shake hands. sometimes we need to establish a common language. so it is with ssl. instead of just starting to communicate, hellos need to be said and handshakes need to take place. there are four main phases to ssl : 3. key exchange 4. ongoing communications let ’ s look at each phase now. during the negotiation phase, the client and server introduce each other, and decide which encryption, authentication and compression protocols will be used. it should be noted that even though the capability for compression exists in the ssl specification, it is rarely, if ever used. in the authentication phase, the server proves itself to the client via a digital certificate. the server may also ask the client to prove itself via a digital certificate. it should be noted that in the case of internet shopping, this is rarely, if ever done. in the key exchange phase, a key is exchanged which will be used in creating a master key for encrypted communications. there are several methods by which this can be done, including the diffie - hellman method, which i shall discuss in a future audiocast. for now, we shall only discuss what is called the rsa method. firstly, the client randomly generates a key called the pre - master secret key [ or pmsk ] by means of a method that will be covered when we discuss ssl in detail a little later on. firstly, the client encrypts the pmsk with it ’ s own private key. this allows the server [ who has a copy of the client ’ s public key ] to authenticate that the pmsk did indeed come from the client. the whole assembly [ that is the pmsk encrypted with the client ’ s private key ] is now encrypted with the server ’ s public key [ which came via the server ’ s certificate


did indeed come from the client. the whole assembly [ that is the pmsk encrypted with the client ’ s private key ] is now encrypted with the server ’ s public key [ which came via the server ’ s certificate ] and sent to the server. the server decrypts the package with it ’ s own private key. this now leaves the original pmsk which has been encrypted with the client ’ s private key. the server decrypts this package with the client ’ s public key and hence authenticates the original pmsk. this original key is not the final key in the process, but is used along with some other items to create the final symmetric key, also known as the master key. from the master key, session keys can be derived. now that both sides have the symmetric or master key, they can exchange messages in an encrypted manner. digital signatures can also be provided to help ensure authentication and message integrity. now we are now ready to discuss the detailed step by step operation of the ssl handshake protocol. step 1. client hello this message begins the entire process. the client _ hello message is sent from the client to the server. there are four main things that are included in the message : 1. a random number called clienthello. random. this random number will be used to create a key later on in the process. the random number consists of a 32 bit timestamp along with 28 bytes created by a random number generator. 2. a list of cyphersuites and compression methods that the client supports. 3. the highest version of ssl that the client supports 4. a session identifier that indicates whether the client wishes to establish a new connection on the current session or establish a new connection on a new session the session identifier is useful for “ going back ” to previous webpages for example. so what is a cyphersuite? a cyphersuite consists of a listing of encryption methods, certificates and integrity checking methods. the client cannot just simply say “ i am going to use this value of encryption, this certificate and this integrity checking method ”. it has to check with the server to see if the server is actually capable of using any of the methods. step 2. server hello the server hello message is sent from the server to the client. there are four main things that the message contains : 1. a random number called serverhello. random. this number will also be used to


client and for mac operations performed by the client. initialization vector values are produced for the situation in which block ciphers in cbc mode are used. step 9 client certificate verification a certificate _ verify message is sent if the client previously provided a certificate to the server. this message is only used with certificates that have signing capabilities. step 10 change cipher spec it should be noted that the change cipher spec protocol is a separate protocol from the handshake protocol. it has been included here due to it ’ s critical function within the handshake protocol itself. ssl keeps a record of two states called the current state and the pending state. we can think of these two states as “ conditions that are happening now ” and “ conditions that will happen later ”. when ssl is first initialized, both states are zero. once the master key is established, that key is used for a pending state. both sides end up with a pending encryption process waiting in the wings so to speak. the pending cipherspec is copied into the current cipherspec. we just need some form of agreement between both ends as to when to begin implementing the encryption. this occurs in the next step. step 11 finished the finished message is used to tell the other end that the key exchange and authentication procedures were successful. this message is encrypted with one of the newly produced keys, and authenticated as well. once the server receives the encrypted finished message from the client, it is able to send it ’ s own change _ cipher _ spec and finished messages in steps 12 and 13 of the process. finally we are able to encrypt any data that needs to be sent from either party. that was quite a lot of material, but the core of the whole process [ as for many other security protocols ] consists of : negotiation, authentication, key exchange and ongoing communications in the show notes section, i have included an interesting trace of a client to server communication process i hope that this audiocast was useful, and thank you for listening. we ’ d love to have you subscribe to our rss feed – just click the button in the upper right corner of the web page. until next week, thanks for listening! if you have any feedback on the show – please drop an e - mail to feedback @ wirelesslanprofessionals. com.


definitions for ultra - gaseous matter the standard electrical dictionary gas so rarefied that its molecules do not collide or very rarely do so. experiments of very striking nature have been devised by crookes and others to illustrate the peculiar phenomena that this matter presents. the general lines of this work are similar to the methods used in geissler tube experiments, except that the vacua used are very much higher. when the vacuum is increased so that but one - millionth of the original gas is left the radiant state is reached. the molecules in their kinetic movements beat back and forth in straight lines without colliding, or with very rare collisions. their motions can be guided and rendered visible by electrification. a tube or small glass bulb with platinum electrodes sealed in it, is exhausted to the requisite degree and is hermetically sealed by melting the glass. the electrodes are connected to the terminals of an induction coil or other source of high tension electrification. the molecules which come in contact with a negatively electrified pole are repelled from it in directions normal to its surface. they produce different phosphorescent or luminous effects in their mutual collisions. thus if they are made to impinge upon glass, diamond or ruby, intense phosphorescence is produced. a piece of platinum subjected to molecular bombardment is brought to white heat. a movable body can be made to move under their effects. two streams proceeding from one negative pole repel each other. the stream of molecules can be drawn out of their course by a magnet. the experiments are all done on a small scale in tubes and bulbs, resembling to a certain extent geissler tubes. [ transcriber ' s note : these effects are caused by plasma - - ionized gas and electrons. ] use the citation below to add this definition to your bibliography : " ultra - gaseous matter. " definitions. net. stands4 llc, 2013. web. 19 may 2013. < http : / / www. definitions. net / definition / ultra - gaseous matter >.


a better plastic researchers at the university of leeds and durham university have solved a long - standing problem that could revolutionize the way new plastics are developed. the breakthrough will allow experts to create the perfect plastic with specific uses and properties by using a high - tech ' recipe book '. it will also increase our ability to recycle plastics. the research is published in the journal science. a plastic material is any of a wide range of synthetic or semi - synthetic organic solids used in the manufacture of industrial products. plastics are typically polymers of high molecular mass, and may contain other substances to improve performance and / or reduce production costs. monomers of plastic are either natural or synthetic organic compounds. the paper ' s authors form part of the microscale polymer processing project, a collaboration between academics and industry experts which has spent 10 years exploring how to better build giant macromolecules. these long tangled molecules are the basic components of plastics and dictate their properties during the melting, flowing and forming processes in plastics production. low - density polyethylenes ( ldpes ) are used in trays and containers, lightweight car parts, recyclable packaging and electrical goods. up until now, industry developed a plastic then found a use for it, or tried hundreds of different recipes to see which worked. this method could save the manufacturing industry time, energy and money. the mathematical models used put together two pieces of computer code. the first predicts how polymers will flow based on the connections between the string - like molecules they are made from. a second piece of code predicts the shapes that these molecules will take when they are created at a chemical level. these models were enhanced by experiments on carefully synthesized perfect polymers created in labs of the microscale polymer processing project. dr daniel read, from the school of mathematics, university of leeds, who led the research, said : " plastics are used by everybody, every day, but until now their production has been effectively guesswork. this breakthrough means that new plastics can be created more efficiently and with a specific use in mind, with benefits to industry and the environment. " professor mcleish added that as plastics production moves from oil - based materials to sustainable and renewable materials, the trial and error phase in developing new plastics could now be by - passed. he said : " by changing two or three numbers in the computer code, we can adapt all the predictions for new bio - polymer sources. " dr. ian robinson of lucite international, one of the industrial participants in the wider project


a notch or groove cut into a piece of material to allow two sections to be combined with a flush joint. a woodcutting tool used to cut an l - shaped groove into a piece of material. see also rabbet a strong current in a stream or river. 1. an enclosed metal channel, usually fire - resistant, installed in a building to hold electrical wiring. 2. a chute that directs the flow of a material to a specific location in a device. a channel holding electrical wiring that is designed to look like a piece of decorative trim or molding. a channel holding electrical wiring designed to be installed on a floor. the unit has a low profile and sloping edges to facilitate walking over it. the illegal practice of directing certain races away from some neighborhoods and into others. 1. a storage unit designed to hold various objects. 2. to cause a structure to shift so that it is out of plumb. 1. a force that causes a structure to shift so that it is out of plumb. 2. installation of bricks or other masonry units so that each course is stepped back from the previous one. straight - line outward movement from a circle ' s center. a power saw with a circular blade that is mounted on a moveable arm. the arm is lowered or raised to move the cutting blade to or away from the material to be cut. a drill press with a moveable arm that can be swung to various positions on the work table. an hvac system with ductwork running outward from a central heating and / or cooling unit. the surface of a log cut down the center. heating system where electrical or hot - water heating elements are installed in a concrete slab floor. see radiant heating use of radiation to generate heat such as with baseboard heating where the circulating hot water is radiated through conduction by thin metal fins at the bottom of the wall. the room is warmed by air circulating around the heating unit using convention. heating unit that is exposed and which transfers heat generated by hot eater or steam through conduction. when the air circulates around the radiator using convention, the room is heated. the distance from the center of a circle to the circumference. one - half of the diameter of a circle. a tool used for checking the radii of convex and concave surfaces. radioactive gas that seeps into some homes, from the ground, through sump pumps, cracks in the foundation, etc., it is considered a health hazard. any of the beams that slope from


or volume of living matter in a given area or volume. carbon cycle - the term used to describe the exchange of carbon ( in various forms, e. g., as carbon dioxide ) between the atmosphere, ocean, terrestrial biosphere, and geological deposits. catchments - assemblages used to capture and retain rainwater and runoff ; an important water management technique in areas with limited freshwater resources, such as gibraltar. ddt ( dichloro - diphenyl - trichloro - ethane ) - a colorless, odorless insecticide that has toxic effects on most animals ; the use of ddt was banned in the us in 1972. defoliants - chemicals which cause plants to lose their leaves artificially ; often used in agricultural practices for weed control, and may have detrimental impacts on human and ecosystem health. deforestation - the destruction of vast areas of forest ( e. g., unsustainable forestry practices, agricultural and range land clearing, and the over exploitation of wood products for use as fuel ) without planting new growth. desertification - the spread of desert - like conditions in arid or semi - arid areas, due to overgrazing, loss of agriculturally productive soils, or climate change. dredging - the practice of deepening an existing waterway ; also, a technique used for collecting bottom - dwelling marine organisms ( e. g., shellfish ) or harvesting coral, often causing significant destruction of reef and ocean - floor ecosystems. drift - net fishing - done with a net, miles in extent, that is generally anchored to a boat and left to float with the tide ; often results in an over harvesting and waste of large populations of non - commercial marine species ( by - catch ) by its effect of " sweeping the ocean clean. " ecosystems - ecological units comprised of complex communities of organisms and their specific environments. effluents - waste materials, such as smoke, sewage, or industrial waste which are released into the environment, subsequently polluting it. endangered species - a species that is threatened with extinction either by direct hunting or habitat destruction. freshwater - water with very low soluble mineral content ; sources include lakes, streams, rivers, glaciers, and underground aquifers. greenhouse gas - a gas that " traps " infrared radiation in the lower atmosphere causing surface warming ; water vapor, carbon dioxide, nitrous oxide, methane, hydrofluorocarbons, and ozone are the primary greenhouse gases in the earth ' s atmosphere. groundwater - water sources found below the surface of


pewter, any of a number of ductile, silver - white alloys consisting principally of tin. the properties vary with the percentage of tin and the nature of the added materials. lead, when added, imparts a bluish tinge and increased malleability and tends to escape from the alloy in poisonous quantities if the percentage used is too large ; antimony adds whiteness and hardness. other metals including copper, bismuth, and zinc can also be added. pewter is shaped by casting, hammering, or lathe spinning on a mold and is usually simply ornamented with rims, moldings, or engraving, although some continental display ware, especially of the renaissance period in france and germany, shows intricate ornamentation. pewter was early used in east asia, and roman pieces are extant. england was a pewter center from the middle ages ; pewter was the chief tableware until it was superseded by china. america imported much english pewter in colonial times and from c. 1700 made large quantities. the craft had virtually disappeared by 1850 but was revived in the 20th cent. in reproductions and in pieces of modern design. the collection and study of pewter are increasingly popular, although relatively little old pewter has been preserved because of its small intrinsic value and of the ease with which it may be melted and reused. pieces made of britannia metal are similar in appearance to pewter ware. see l. l. laughlin, pewter in america ( 1969 ) ; and h. j. kauffman, the american pewterer ( 1970 ) ; c. f. montgomery, a history of american pewter ( 1973 ). more on pewter from infoplease : see more encyclopedia articles on : arts and crafts


refraction at a boundary need to see it? view the broken pencil animation from the multimedia physics studios. flickr physics visit the physics classroom ' s flickr galleries and enjoy a photo overview of the topic of refraction and lenses. flickr physics visit the physics classroom ' s flickr galleries and enjoy the terrific display of photos showing the refraction of light by dew drops. flickr physics view a collection of incredible photos of reflection and refraction phenomena from tpc ' s flickr pool. looking for a lab that coordinates with this page? try the refraction action lab from the laboratory. flickr physics view a collection of incredible photos of reflection and refraction phenomena from tpc ' s flickr pool. curriculum corner learning requires action. give your students this sense - making activity from the curriculum corner. treasures from tpf need ideas? need help? explore the physics front ' s treasure box of catalogued resources on ray optics, including the topic of refraction. refraction and sight in unit 13 of the physics classroom tutorial, it was emphasized that we are able to see because light from an object can travel to our eyes. every object that can be seen is seen only because light from that object travels to our eyes. as you look at mary in class, you are able to see mary because she is illuminated with light and that light reflects off of her and travels to your eye. in the process of viewing mary, you are directing your sight along a line in the direction of mary. if you wish to view the top of mary ' s head, then you direct your sight along a line towards the top of her head. if you wish to view mary ' s feet, then you direct your sight along a line towards mary ' s feet. and if you wish to view the image of mary in a mirror, then you must direct your sight along a line towards the location of mary ' s image. this directing of our sight in a specific direction is sometimes referred to as the line of sight. as light travels through a given medium, it travels in a straight line. however, when light passes from one medium into a second medium, the light path bends. refraction takes place. the refraction occurs only at the boundary. once the light has crossed the boundary between the two media, it continues to travel in a straight line. only now, the direction of that line is different than it was in the former medium. if when sighting at an object, light from that object changes media on the way to your eye,


two media, it continues to travel in a straight line. only now, the direction of that line is different than it was in the former medium. if when sighting at an object, light from that object changes media on the way to your eye, a visual distortion is likely to occur. this visual distortion is witnessed if you look at a pencil submerged in a glass half - filled with water. as you sight through the side of the glass at the portion of the pencil located above the water ' s surface, light travels directly from the pencil to your eye. since this light does not change medium, it will not refract. ( actually, there is a change of medium from air to glass and back into air. because the glass is so thin and because the light starts and finished in air, the refraction into and out of the glass causes little deviation in the light ' s original direction. ) as you sight at the portion of the pencil that was submerged in the water, light travels from water to air ( or from water to glass to air ). this light ray changes medium and subsequently undergoes refraction. as a result, the image of the pencil appears to be broken. furthermore, the portion of the pencil that is submerged in water appears to be wider than the portion of the pencil that is not submerged. these visual distortions are explained by the refraction of light. in this case, the light rays that undergo a deviation from their original path are those that travel from the submerged portion of the pencil, through the water, across the boundary, into the air, and ultimately to the eye. at the boundary, this ray refracts. the eye - brain interaction cannot account for the refraction of light. as was emphasized in unit 13, the brain judges the image location to be the location where light rays appear to originate from. this image location is the location where either reflected or refracted rays intersect. the eye and brain assume that light travels in a straight line and then extends all incoming rays of light backwards until they intersect. light rays from the submerged portion of the pencil will intersect in a different location than light rays from the portion of the pencil that extends above the surface of the water. for this reason, the submerged portion of the pencil appears to be in a different location than the portion of the pencil that extends above the water. the diagram at the right shows a god ' s - eye view of the light path from the submerged portion of the pencil to each of your two eyes. only the left and right


different location than the portion of the pencil that extends above the water. the diagram at the right shows a god ' s - eye view of the light path from the submerged portion of the pencil to each of your two eyes. only the left and right extremities ( edges ) of the pencil are considered. the blue lines depict the path of light to your right eye and the red lines depict the path of light to your left eye. observe that the light path has bent at the boundary. dashed lines represent the extensions of the lines of sight backwards into the water. observe that these extension lines intersect at a given point ; the point represents the image of the left and the right edge of the pencil. finally, observe that the image of the pencil is wider than the actual pencil. a ray model of light that considers the refraction of light at boundaries adequately explains the broken pencil observations. flickr physics photo the broken pencil phenomenon occurs during your everyday spearfishing outing. fortunately for the fish, light refracts as it travels from the fish in the water to the eyes of the hunter. the refraction occurs at the water - air boundary. due to this bending of the path of light, a fish appears to be at a location where it isn ' t. a visual distortion occurs. subsequently, the hunter launches the spear at the location where the fish is thought to be and misses the fish. of course, the fish are never concerned about such hunters ; they know that light refracts at the boundary and that the location where the hunter is sighting is not the same location as the actual fish. how did the fish get so smart and learn all this? they live in schools. now any fish that has done his / her physics homework knows that the amount of refraction that occurs is dependent upon the angle at which the light approaches the boundary. we will investigate this aspect of refraction in great detail in lesson 2. for now, it is sufficient to say that as the hunter with the spear sights more perpendicular to the water, the amount of refraction decreases. the most successful hunters are those who sight perpendicular to the water. and the smartest fish are those who head for the deep when they spot hunters who sight in this direction. since refraction of light occurs when it crosses the boundary, visual distortions often occur. these distortions occur when light changes medium as it travels from the object to our eyes.


making graphene nanoribbons : the process for tailoring of the silicon carbide crystal for selective graphene growth and device fabrication is illustrated, starting with the top left figure. ( a ) a nanometer - scale step is etched into the silicon carbide crystal by a fluorine - based reactive ion etch ( rie ). ( b ) the crystal is heated to about 1200 - 1300 degrees celsius ( at low vacuum ), inducing step flow and relaxation to the etching. ( c ) when the crystal is further heated to about 1450 degrees celsius, a graphene nanoribbon forms. ( d ) from there the source and drain contacts, graphene nanoribbon channel, aluminum oxide gate dielectric and metal top gate are added. image : courtesy of walter de heer for years researchers have held out hope that graphene would be the material to pick up the mantle in the electronics industry when silicon hits its limits as the material of choice for making devices smaller, faster and cheaper. yet, turning graphene ' s promise into a reality has been difficult to say the least, in part because of the inherent difficulty of working with a substance one atom thick. methods of cutting graphene into useable pieces tend to leave frayed edges that mitigate the material ' s effectiveness as a conductor. now, a team of researchers at georgia institute of technology led by walter de heer claims to have made a significant advance in that area by developing a technique for creating nanometer - scale graphene ribbons without rough edges. ( a nanometer is one billionth of a meter. ) graphene has, of course, made headlines throughout the scientific world this week, thanks to the awarding of the nobel prize in physics to two researchers at the university of manchester in england who in 2004 pioneered a way of isolating graphene by repeatedly cleaving graphite with adhesive tape. the nobel prize committee recognized andre geim and konstantin novoselov " for groundbreaking experiments regarding the two - dimensional material graphene. " unlike the approach taken by geim and novoselov, de heer and his team in the past have created graphene sheets by heating a silicon carbide surface to 1, 500 degrees celsius until a layer of graphene formed. the graphene was then cut to a particular size and shape using an electron beam. " this was a serious problem because cutting graphene leaves rough edges that destroy a lot of graphene ' s good properties, making it less conduct


graphene formed. the graphene was then cut to a particular size and shape using an electron beam. " this was a serious problem because cutting graphene leaves rough edges that destroy a lot of graphene ' s good properties, making it less conductive, " says de heer, regents ' professor in georgia tech ' s school of physics. de heer ' s new approach, described october 3 in nature nanotechnology, is to etch patterns into the silicon carbide and then heat that surface until graphene forms within the etched patterns. ( scientific american is part of nature publishing group. ) in this way graphene forms in specific shapes and sizes without the need for cutting. " the whole philosophy has changed, " he says. " we ' re not starting with an infinite sheet of graphene ; we ' re growing it where we want to grow it. " the researchers claim to have used the technique to fabricate a densely packed array of 10, 000 top - gated graphene transistors on a 0. 24 - square - centimeter chip, a step toward their ultimate goal of creating graphene components that can be integrated with silicon for new generations of electronics. such a consolidation would be a key milestone towards making microprocessors able to operate at terahertz speeds, 1, 000 times faster than today ' s chips ( whose speeds are clocked at billions of hertz ). another goal is to reduce heat generation as an increasing number of transistors are packed onto each chip. such advances would continue to validate moore ' s law even as silicon circuits reach their miniaturization limit. " in principle, graphene can overcome silicon ' s limitation, " de heer says. " if we completely succeed [ only ] time will tell. " graphene and silicon will be able to coexist much the same way that airplanes and freight ships are used for transporting cargo. " they move at different speeds, but both are important because they have different costs, " de heer says. " i think a similar thing will happen in electronics. " de heer is also quick to acknowledge that, although the study of graphene dates back to the 1970s, the field still has a long way to go. he and his team are now investigating how the ribbons they created will perform over time and to what degree their new approach improves on cutting pieces of graphene out of larger sheets. with so many open questions about graphene ' s viability, de heer says he was


light, a sensitivity speck on the surface of the crystal is turned into a small speck of metallic silver ( these comprise the invisible or latent image ). if the speck of silver contains approximately four or more atoms, it is rendered developable - meaning that it can undergo development which turns the entire crystal into metallic silver. areas of the emulsion receiving larger amounts of light ( reflected from a subject being photographed, for example ) undergo the greatest development and therefore results in the highest optical density. silver halides, except for silver fluoride, are extremely insoluble in water. silver nitrate can be used to precipitate halides ; this application is useful in quantitative analysis of halides. the precipitation of silver halides via silver nitrate is also useful for abstracting halide leaving groups. however, close attention is necessary for other compounds in the test solution. some compounds can considerably increase or decrease the solubility of agx. examples of compounds that increase the solubility include : cyanide, thiocyanate, thiosulfate, thiourea, amines, ammonia, sulfite, thioether, crown ether. examples of compounds that reduces the solubility include many organic thiols and nitrogen compounds that do not possess solubilizing group other than mercapto group or the nitrogen site, such as mercaptooxazoles, mercaptotetrazoles, especially 1 - phenyl - 5 - mercaptotetrazole, benzimidazoles, especially 2 - mercaptobenzimidazole, benzotriazole, and these compounds further substituted by hydrophobic groups. compounds such as thiocyanate and thiosulfate enhance solubility when they are present in a sufficiently large quantity, due to formation of highly soluble complex ions, but they also significantly depress solubility when present in a very small quantity, due to formation of sparingly soluble complex ions. see also : argentometry. scientists from tel aviv university are experimenting with silver halide optical fibers for transmitting mid - infrared light from carbon dioxide lasers. the fibers allow laser welding of human tissue, as an alternative to traditional sutures.


skip to main content your organization might have access to this article on the publisher ' s site. to check, click on this link : http : / / dx. doi. org / + 10. 1063 / 1. 1148044 a highly sensitive gas sensor for detection and analytical identification of hazardous gases was developed, by depositing partially crystalline powder from an aqueous suspension of cds powder on an alumina substrate. when the deposited layers were promoted with catalysts from pt - group metals, they exhibited high sensitivity to different gas molecules upon modulation with light of certain frequency, depending on catalyst and impurity concentration. dark resistance and photosensitivity of the sensors were monitored against gas concentration, sensor temperature, and frequency of the modulating light. depending on the gas and its concentration, a change of up to 100 % in sensor response was observed. variation of photosensitivity with dark resistance showed different slopes for different molecules. variation of the low frequency phase angle with photosensitivity at different concentrations also produced different slopes, depending on the type of molecule. this differentiation likely comes about by different interactions of gas molecules with surface recombination centers, depending on the nature of physisorption and / or chemisorption on the surface. thus, in addition to detecting the gas, it can be identified from their slopes of variation with light frequency, and the sensor can be used as an analytical tool. © 1997 american institute of physics.


wed february 22, 2012 is einstein right? error could account for faster - than - light neutrinos originally published on wed february 22, 2012 4 : 25 pm remember last year, when we reported that italian scientists claimed to have broken the speed of light? remember the mystical implications of that? the possibility that einstein was wrong? that our very basic idea of physics was challenged? the idea that you could be shot before a bullet left a gun? then you also remember that our friend and astrophysicist adam frank warned that these results should be looked at with great suspicion. it turns out the results from the experiment called opera ( oscillation project with emulsion - tracking apparatus ) could have been affected by a problem with the gps system used to time the neutrinos. a spokesman for the european organization for nuclear research confirmed the error to the associated press today. the ap reports that james gillies says only other experiments planned for later this year will confirm whether the problem affected the results. science magazine reported the issue earlier today. the reported : " according to sources familiar with the experiment, the 60 nanoseconds discrepancy appears to come from a bad connection between a fiber optic cable that connects to the gps receiver used to correct the timing of the neutrinos ' flight and an electronic card in a computer. after tightening the connection and then measuring the time it takes data to travel the length of the fiber, researchers found that the data arrive 60 nanoseconds earlier than assumed. since this time is subtracted from the overall time of flight, it appears to explain the early arrival of the neutrinos. new data, however, will be needed to confirm this hypothesis. " so the bottom line is more experiments are needed to discard the findings for sure.


in my earlier post on the meaning of understanding, i describe understanding of mathematics as making connections : to understand is to make connections. these connections are not done in random. concepts are linked with other concepts in order to create a richer image for the new concept that is being learned. to understand therefore is to form concept image. and a concept image is not formed by defining the concept. the definition of a concept is different from the concept image. let me share with you a an excerpt from my paper which discusses this idea. you can view the references here. understanding the definition does not imply understanding the concept. in order to understand a concept one must have a concept image for it. one ’ s concept image includes all the non - verbal entities, visual representations, impressions and experiences that are created in our mind by a mention of a concept name ( vinner, 1992 ). vinner stressed that the concept definition is not the first thing that is learned in understanding a concept but the experiences associated with it, which becomes part of one ’ s concept image. vinner believes that in carrying out cognitive tasks, the mind consults the concept image rather than the concept definition. vergnaud ( 1997 ) also noted, “ it is misleading, even in mathematics [ despite its precision in defining ], to consider that the properties of a concept are self - contained in its definition ” ( p. 5 ). to study and understand how mathematical concepts are develop in students ’ minds through their experience both in and outside school, vergnaud proposed that one needs to consider a concept c as a three - uple of three sets : c = ( s, i, r ) s : the set of situations that make the concept useful and meaningful. i : the set of operational invariants that can be used by individuals to deal with these situations. r : the set of symbolic representations, linguistic, graphic or gestural that can be used to represent invariants, situations and procedures ( p. 6 ) what are these telling us mathematics teachers? well, firstly, that it is not a good practice to start with concept definitions and secondly that it is important to design learning experiences that will create and enrich the concept image because it is then and only then when students can relate to the definition. definitions are already an abstraction of the concept. for example, if you give the child the definition of a dog, do you think he ’ d recognize one if he sees one? kidding. in order to be suitable to learners, a definition must consist of concepts known


aero thermal & mechanical systems niskayuna, ny usa more than 50 years ago, richard feynman urged the pursuit of micro and nano scale devices. this pursuit has brought significant advances in micro and nano electronics made possible by the transistor. more recently, mems devices, built from similar materials and leveraging the same tools set at silicon based electronics, have made their way into existence. there is even an industry group dedicated to advancing mems. just a few weeks back, the managing director of the mems industry group stopped by our research center to learn more about our ongoing research. about 15 years ago, the new york times published an article about the future of an exciting technology called mems. we are living the realization of mems technology and today, ge is on the verge of enabling a whole new revolution in mems applications. but i digress. first of all, you are probably wondering what mems devices are. mems stands for micro electromechanical systems and are tiny ( smaller than the width of your hair ) microscopic sensors and actuators that most of us use every day without ever realizing it. if you are reading this blog post from a smart phone, you are using mems inertial sensing devices right now to control your screen orientation. if you drove a car to work today, a mems accelerometer was protecting you in your car ’ s airbag sensor. some of the very first mems devices were ink - jet print heads and pressure sensors. later today when you de - stress from a long work day playing your favorite wii game, you will encounter mems again. the mems accelerometers and gyroscopes in the game controller are what senses your motion and is what makes these games possible. yes, mems devices are all around us! be sure to check out the short clip below where i explain how mems devices are used in different parts of a car including the engine, tires and the airbags. our mems team is developing an entirely new class of devices that will span across numerous applications from consumer to commercial and industrial products. this device platform is enabled by novel materials that deliver orders of magnitude improvement to device performance. we ’ re excited to soon share with all of you what ge researchers are doing with mems technology. next week, we will take you inside our cleanroom where much of our mems work is done. and two weeks from now, we will reveal some of revolutionary applications we are working to enable.


layered magnetic structures : evidence for antiferromagnetic coupling of fe layers across cr interlayers grunberg, p., schreiber, r., pang, y., brodsky, m. b., & sowers, h. ( 1986 ) layered magnetic structures : evidence for antiferromagnetic coupling of fe layers across cr interlayers. phys. rev. lett. 57, 2442. essay about this article in albert fert ’ s thinking that lead to a realization of gmr, it was necessary to have an antiferromagnetic coupling between layers so that an external magnetic field could switch them to parallel alignment. it took another 20 years to achieve antiferromagnetically aligned magnetic layers sandwiched between non - magnetic metallic spacers. this achievement was due largely to a parallel development in multilayers that used semiconducting elements, in this case heterostructures. semiconducting elements have a lower affinity to interdiffuse at the interfaces between layers than do metallic elements ; therefore one was able to grow heterostructures by 1980. by following the recipe used for semiconductors several groups were able to achieve a controlled growth for metallic multilayers that demonstrated antiferromagnetic coupling between magnetic layers. notably peter grunberg grew fe / cr and fe / au double layers consisting of two fe layers separated by a thin spacer layer of cr or au, and demonstrated that the alignment between the fe layers was antiparallel before applying an external magnetic field. to determine the alignment and evaluate the interlayer coupling between the iron layers grunberg used the brillouin light scattering technique, in which light either excites or absorbs spin wave modes [ small deviations of the magnetization of the iron layers from their equilibrium positions ], and thereby either lowers or raises the frequency of the light. to ascertain the alignment of the iron layers grunberg noted whether an applied field shifted the light ’ s frequency. no shift indicated the magnetizations of the iron layers were parallel because either there is no coupling or a ferromagnetic coupling between layers. by varying the thickness of the spacer layer between a few and 20 a he identified the thicknesses where the alignments were antiparallel in zero field ; in particular he found that the coupling was definitively antiferromagnetic for 8 a of chromium. with this feat peter grunberg provided the material, a fe / cr


the alignments were antiparallel in zero field ; in particular he found that the coupling was definitively antiferromagnetic for 8 a of chromium. with this feat peter grunberg provided the material, a fe / cr multilayer, to test the idea of albert fert on gmr. parenthetically, the origin of the exchange coupling between magnetic layers across a nonmagnetic metallic spacer layer is similar to the ruderman - kittel - kasuya - yosida [ rkky ] interaction. that is, a magnetic moment immersed in a fermi sea of electrons creates a local polarization in the gas ; as only the electrons at the fermi level can produce the polarization, due to the availability of empty electron states to rearrange the electron distribution in the vicinity of the local moment, the induced magnetic polarization oscillates between being parallel and opposite to the local magnetic moment. this is reminiscent of the charge oscillations induced in a fermi sea of electrons by an added charge, which is known as friedel oscillations. when a second magnetic moment is in the proximity of the first it feels the magnetic polarization induced by it, i. e., it senses a local magnetic field, and aligns itself in its direction ; hence one establishes an indirect exchange interaction between the two moments through the metal ’ s electron gas. when a magnetic layer [ iron ] is in contact with a nonmagnetic metallic spacer it polarizes the electron gas in the spacer and provides the exchange field to couple to the magnetization of the magnetic layer at the opposite end of the spacer. this interlayer exchange coupling between magnetic layers is sizeable only for thin spacers of the order of a few nanometers, and oscillates between ferromagnetic and antiferromagnetic coupling due to the rkky or “ friedel ” oscillations. it should be mentioned that an interlayer exchange coupling was found about the same time as grunberg ’ s demonstration on fe / cr. groups at bell labs and at the university of illinois found an oscillatory coupling in multilayers containing rare - earth metals, e. g., dysprosium - yttrium [ dy - y ], where dy is magnetic and y nonmagnetic. after the discovery of gmr in magnetic multilayers there was tremendous interest in interlayer exchange coupling. stuart park


, published, or sold in whole or part, without prior written permission from the american physical society. select articles citing this paper himpsel, f. j., j. e. ortega, et al. ( 1998 ). " magnetic nanostructures. " advances in physics 47 ( 4 ) : 511 - 597. bruno, p. ( 1995 ). " theory of interlayer magnetic coupling. " physical review b 52 ( 1 ) : 411 - 439. unguris, j., r. j. celotta, et al. ( 1991 ). " observation of 2 different oscillation periods in the exchange coupling of fe / cr / fe ( 100 ). " physical review letters 67 ( 1 ) : 140 - 143. parkin, s. s. p., z. g. li, et al. ( 1991 ). " giant magnetoresistance in antiferromagnetic co / cu multilayers. " applied physics letters 58 ( 23 ) : 2710 - 2712. parkin, s. s. p., n. more, et al. ( 1990 ). " oscillations in exchange coupling and magnetoresistance in metallic superlattice structures - co / ru, co / cr, and fe / cr. " physical review letters 64 ( 19 ) : 2304 - 2307. binasch, g., p. grunberg, et al. ( 1989 ). " enhanced magnetoresistance in layered magnetic - structures with antiferromagnetic interlayer exchange. " physical review b 39 ( 7 ) : 4828 - 4830. baibich, m. n., j. m. broto, et al. ( 1988 ). " giant magnetoresistance of ( 001 ) fe / ( 001 ) cr magnetic superlattices. " physical review letters 61 ( 21 ) : 2472 - 2475.


researchers at rensselaer polytechnic institute have created a razor - like material that is truly on the “ cutting edge ” of nanotechnology. called nanoblades, these first - of - their - kind magnesium nanomaterials challenge conventional wisdom about nanostructure growth, and could have applications in energy storage and fuel cell technology. the discovery is detailed in the september 2007 issue of the journal of nanoscience and nanotechnology. the sharp nanometer - scale surface is vastly different from any other nanomaterial that has been created before using oblique angle deposition, according to lead researcher gwo - ching wang, professor and head of physics, applied physics, and astronomy at rensselaer. the team ’ s nearly two - dimensional structure changes the traditional understanding of oblique angle deposition, which was previously thought to always create cylindrical structures like nanorods or nanosprings. unlike three - dimensional springs and rods, nanoblades are extremely thin, with very large surface areas. they also are surprisingly spread out for a uniform nanomaterial, with one to two micron meters in between each blade, according to wang. the materials could be extremely useful for energy storage, particularly hydrogen storage, wang said. in order to store hydrogen, a large surface area is needed to provide room for the material to expand as more hydrogen atoms are stored. the vast surface area of each nanoblade, coupled with the large spaces between each blade, could make them ideal for this application. to create the nanoblades, the researchers used oblique angle vapor deposition. this widely used fabrication technique builds nanostructures by vaporizing a material — magnesium in this case — and allowing the vaporized atoms to deposit on a surface at an angle. as the deposition angle changes, the structure of the material deposited on the surface also changes. when the researchers deposited the magnesium straight onto a surface at zero degrees, the blades resembled a handful of cornflakes — flat, flakey structures overlapping one another. it wasn ’ t until the deposition angle was increased that the blade - like nature of these new nanomaterials became apparent. as the magnesium deposition angle was increased, the researchers were surprised that the structures first tilted away from the magnesium vapor source instead of the expected inclination toward the source. the blades then quickly curved upward to form nearly vertical structures resembling nano - scale razorblades. the blades also become ultra thin. from the side, the nanoblades resemble an overgrown lawn with thin, blade - like spires. at a 75 degree


blades then quickly curved upward to form nearly vertical structures resembling nano - scale razorblades. the blades also become ultra thin. from the side, the nanoblades resemble an overgrown lawn with thin, blade - like spires. at a 75 degree angle, the nanoblades had a thickness of as little as 15 nanometers and a width of a few hundred nanometers. researchers at rensselaer are now looking at ways to coat the magnesium nanoblades with metallic catalysts to trap and store hydrogen. the researchers monitored the blades as they were growing using a reflection high - energy electron diffraction ( rheed ) technique to create a surface pole figure or image. the new technique, created at rensselaer, is different from other diffraction techniques such as x - rays because it monitors the surface structure of the material as it grows. x - rays and other technologies measure the entire material, from the tip of the new growth straight through the substrate that the material is growing on. tracking the surface evolution of the material provides insight into how the structure evolves over time and helps scientists understand the mechanism of nanostructure formation, allowing engineers to later recreate ideal nanomaterials in the future. the creation of surface pole figures was particularly important in understanding the growth of nanoblades, as the surface morphology changed vastly over time. the surface pole figure technique was first outline by fu tang, a postdoctoral research associate in wang ’ s group, in a 2006 issue of applied physics letters. in that paper, surface pole figures were created for nanorod growth. the researchers are now working to analyze nanoblade growth to provide additional insight into the growth patterns of these new nanomaterials. other rensselaer researchers involved with the project are toh - ming lu, the r. p. baker distinguished professor of physics ; gaann fellow tom parker ; and postdoctoral research associate huafang li. source : rensselaer polytechnic institute explore further : researchers develop method to inkjet print highly conductive, bendable layers of graphene