bluuebunny/crossref_metadata_2025 huggingface dataset:
Additional testing needed to confirm warming of water off New Jersey Shore
Authors: Drinkwater K. F.
Published: October 2006

The article by Fisher et al. presents intriguing results. Their analysis of thermal data from boreholes in the sediment suggests large temperature variability (of order 6–10°C) primarily over the last 60 years with maximum temperatures approximately 20 years ago at a site (#903) on the continental slope off the southern Middle Atlantic Bight in approximately 450 m depth. Similar techniques suggest no such temperature change at a site (#902) 4.4 km away in 802 m of water.

The waters normally lying along the continental slope of the Middle Atlantic Bight and regions to the north are known as slope waters. These waters extend seaward to the northern edge of the Gulf Stream. Temperatures are typically 6–7°C at depths of 450 m or so, increasing almost linearly towards 10–15°C in shallower waters of 200 m [Stommel, 1965]. Below 700 m, temperatures are in the 4–5°C range. Similar temperatures were shown by Sverdrup et al. [1942] at a station along the slope off Chesapeake Bay in 1932. These same authors note the large variability in temperatures at around 400 m and attribute it to slope‐type waters being interspersed with short periods of North Atlantic central (Gulf Stream) waters produced by the presence of eddies or shelfward displacements in the stream itself.
Chinese‐American headway on some environmental issues
Authors: Showstack Randy
Published: October 2006

Although Chinese Premier Zhu Rongji may have failed to gain entrance for his country into the World Trade Organization during his April visit to the United States, the two countries concluded a series of agreements as part of the Second Session of the 2‐year‐old U.S.‐China Policy Forum on Environment and Development.

A memorandum of understanding on a $100 million clean energy program accelerates the export of clean U.S. environmental technologies in the area of energy efficiency renewable energy, and pollution reduction. A statement of intent on the development of a Sulfur Dioxide (SO2) Emissions Trading Feasibility Study calls for China to develop a study to test the effectiveness of emissions trading in China as a market‐based approach to reducing greenhouse gas emissions. And a Memorandum of Understanding on a natural gas pipeline project, signed by the Enron Corporation and the China National Petroleum Corporation, opens the way to jointly developing a natural gas pipeline to help offer an alternative to fossil fuels.
Rock conference looks at pore pressure, scale effects, and deformation
Authors: Bouteca Maurice , Guéguen Yves
Published: October 2006

The mechanical behavior and physical properties of commonly anisotropic, cracked, and porous rocks are of importance in the oil industry contaminant transport, and seismic hazard evaluations. About 70 researchers gathered last fall to discuss recent advances as well as shortcomings in our understanding of rock physics and rock mechanics, with scientists from both communities sharing their knowledge to explain geological observations.

Field and laboratory data were juxtaposed with models to highlight the nature of pore pressure regimes and their influence on the deformation of rocks. The range of scales that exist in geology, from plate tectonics to fault breccias, demands that macroscopic geomechanical concepts and laws are related to microscopic processes. Much of the meeting was dedicated to that large topic: bringing macroscopic observations to an understanding of the microscopic process.
Scientists discover solar system 44 light years from Earth
Authors: Showstack Randy
Published: October 2006

Worlds away from the Earth, 44 light years away in the Andromeda constellation, three Jupiter‐sized planets are orbiting Upsilon Andromedae,a bright star 1.2 times the mass of our Sun and two‐thirds of its 4.5 billion year age. This dramatic discovery, jointly announced by scientists from four research institutions on April 15, is the first planetary system ever found around a normal star, aside from our Solar System.

The finding suggests that planetary systems may be abundant in the Milky Way galaxy, and may indicate a new era of extrasolar planetary exploration and study, according to some scientists involved in the discovery.
SciLINKS hooks up science textbooks to the Internet
Authors: Showstack Randy
Published: October 2006

Holt, Rinehart and Winston, a textbook arm of Harcourt Brace Company, is publishing two new science textbooks that include something unusual in their margins. The books have icons and codes that refer students, teachers, and even parents to a hand‐picked and regularly updated selection of relevant Internet sites.

Other publishing houses soon may follow suit.
Reply: New results justify open discussion of alternative models
Authors: Newman Andrew , Stein Seth , Weber John , Engeln Joseph , Mao Aitlin , Dixon Timothy
Published: October 2006

A millennium ago, Jewish sages wrote that “the rivalry of scholars increases wisdom.” In contrast, Schweig et al. (Eos, this issue) demand that “great caution” be exercised in discussing alternatives to their model of high seismic hazard in the New Madrid seismic zone (NMSZ). We find this view surprising; we have no objection to their and their coworkers' extensive efforts promoting their model in a wide variety of public media, but see no reason not to explore a lower‐hazard alternative based on both new data and reanalysis of data previously used to justify their model. In our view, the very purpose of collecting new data and reassessing existing data is to promote spirited testing and improvement of existing hypotheses. For New Madrid, such open reexamination seems scientifically appropriate, given the challenge of understanding intraplate earthquakes, and socially desirable because of the public policy implications.
Water vapor pressure should be addressed in Potomac study
Authors: Egan Walter G.
Published: October 2006

In Bruce Doe's article, “A Potomac Perspective on the Growing Global Greenhouse” (Eos, January 5,1999), a statement is made in the next to last paragraph that “other climatic parameters such as precipitation can correlate better than temperature among the five sites.” It would be expected that precipitation, and in particular the partial pressure of water vapor, should correlate with the carbon dioxide greenhouse effect.

It was pointed out by W. G. Egan and coworkers in 1991 that there is an inverse relationship between carbon dioxide and water vapor partial pressure, seen both in laboratory experiments and at all worldwide Global Monitoring for Climate Change monitoring stations. Specific examples were presented for Cold Bay, Alaska and Palmer Station, Antarctica monthly and annually
Proposed project would give unprecedented look under North America
Authors: Levander Alan , Humphreys Eugene D. , Ekstrom Goran , Meltzer Anne S. , Shearer Peter M.
Published: October 2006

An unprecedented examination of the Earth's deep interior and investigation across a broad range of scales of the structure of the North American continent and the processes that formed it would be among the undertakings of a proposed 10‐year Earth Science project called USArray. Now in the planning and development stage, the project would permit a three‐dimensional (3‐D) systematic investigation of North America, improving the resolution of lithospheric images by an order of magnitude.

For the Earth sciences, the project would be the seismological equivalent of the Hubble space telescope. A number of factors suggest that North America is particularly suited for this project, including the states of current knowledge and technology, the availability of a sophisticated infrastructure, organization in the seismological community scientific economy, and widespread scientific interest.
U.S. council calls for sustained ocean observing system
Authors: Showstack Randy
Published: October 2006

A council that includes the heads of 12 United States federal agencies involved in funding ocean research or developing ocean research policy has called for the establishment of a national integrated and sustained ocean observing system.

Officials said the system should integrate new tools to monitor changes in the oceans' physical, biological, and chemical systems with the many already‐existing satellite and in situ observing elements. The system, they said, could improve long‐term climate forecasts, increase understanding of long and short‐term ocean phenomena, and help to answer some key questions concerning global warming.
The Deep Hot Biosphere
Authors: Craig Harmon
Published: October 2006

The first inhabitants of planet Earth were single‐celled microorganisms and they are still with us today. Their name is truly legion, for they live everywhere, from boiling hot springs at the Earth's surface and on the seafloor to the coldest waters of the oceans and the Antarctic lakes. They are the masters of evolutionary adaptation, who have colonized the entire range of conditions under which water can exist as a liquid. At some ancient mythic time billions of years ago in a witches' brew of precursory molecules, somewhere, somehow, on a sunny Precambrian day bright with promise some of these molecules came together in the first coupling, learned to replicate, create enzymes, metabolize, and seal themselves into protective membranes inside of which they began the process of living. How they did this is our greatest mystery, for they are our primordial ancestors and we do not understand ourselves until we understand them.
Study proposes wholesale change in thinking about natural hazards mitigation
Authors: Showstack Randy
Published: October 2006

The “lollapaloozas,” the major natural catastrophes, are getting bigger and bigger, and it is time to confront this growing problem by dramatically changing the way that society approaches natural hazard mitigation, conducts itself in relation to the natural environment, and accepts responsibility for activities that could lead to or increase disasters, according to Dennis Mileti, principal investigator of a new study on natural hazards, and director of the Natural Hazards Research and Applications Information Center at the University of Colorado at Boulder.

Since 1989, the United States has been struck by seven of the nation's 10 most costly natural disasters, including the 1994 Northridge earthquake in California that caused $25 billion in damages. Also since 1989, the financial cost of natural hazards in the United States—which includes floods, earthquakes, hurricanes, and wildfires, as well as landslides, heat, and fog—has frequently averaged $1 billion per week, a price that some experts say will continue rising. Internationally, the Kobe, Japan, earthquake cost more than $100 billion and is the most financially costly disaster in world history None of these figures include indirect losses related to natural disasters, such as lost economic productivity
Isotope Tracers in Catchment Hydrology
Authors: Hornberger George M.
Published: October 2006

The drainage basin has been a fundamental unit of study in hydrology and geomorphology throughout the modern era of these Earth sciences. The basin, or catchment, is a convenient unit because it typically is well defined topographically, can be studied as a series of nested units of increasing size, and is an open system for which inputs and outputs of mass and energy can be defined and measured. Small catchments have been the “outdoor laboratories” for hydrologists interested in rainfall‐runoff relationships, for geochemists interested in the export of weathering products from the landscape, and for ecosystem ecologists interested in biogeochemical cycling.

Research studies on small catchments have evolved from a strong focus on strictly input‐output relationships (a “black‐box” approach) to a focus on understanding flow paths, residence times, and biological and chemical reactions within the catchment. Tracers are essential tools for such work. In catchment studies, tracers that move with the water but do not interact with biota, soils, and rocks are sought so that water itself can be followed. Other tracers are used to follow selected biogeochemical reactions. A multitude of stable and radioactive isotopes has been used as tracers in catchment studies.
Global Climate Project shows early promise
Authors: Trenberth Kevin E.
Published: October 2006

The implementation of a global climate project and its early results are being hailed as exciting leaps forward in climate research that have enormous potential for improving predictions of interannual variations, as well as improving the understanding and modeling, and possibly developing predictive capabilities, of decadal and longer variability and climate change. Known as the Climate Variability and Predictability (CLIVAR) project of the World Climate Research Programme (WCRP),its most recent achievements have included observations, predictions, and documentation of the evolution of the 1997–1998 El Niño and that event's progression into the 1998 La Niña. In place to accomplish this was CLIVAR's full tropical Pacific observing system and new coupled atmosphere‐upper ocean models.

Even more exciting was that prediction models were able to capture aspects of the differences in teleconnection patterns between this El Niño and previous events, pointing to the importance of sea surface temperature patterns globally Exciting new possibilities also have emerged through profiling floats deployed at various depths that come to the surface every week or two to give ocean soundings of temperature and salinity, while their displacements provide estimates of ocean currents at depth.
Report suggests some public attitudes about geophysical and environmental issues
Authors: Showstack Randy
Published: October 2006

“Global warming, greenhouse. It is pretty much written that everything is going to come to an end,” said one man during a focus group held in Des Moines, Iowa. “No one wants to pull back what they have. Humans are greedy and they want what they want. We will be like the dinosaurs when the meteorite hits the Earth.”

“Global warming. It has a lot to do with the ozone layer, and with all of the ice melting and stuff like that.The warming comes because of the icecaps melting,” said a man involved with a focus group in Los Angeles, California.
Preparing for the Atlantic hurricane season
Authors: Showstack Randy
Published: October 2006

In response to forecasts that the 1999 Atlantic hurricane season could be highly active, the American Red Cross is recommending that people in hurricane impact zones take measures to prepare for and mitigate against potentially devastating storms.

“Given the huge toll last year's hurricane season took on the United States, the Caribbean, and Central America, we should take all necessary precautions as the 1999 hurricane season gets underway” said Steve Bullock, acting president of the American Red Cross.
Two Resources for Planetary Scientists
Authors: Bell Jim
Published: October 2006

I still carry with me perhaps the most useful trinket I've ever received at a professional conference. Some years ago, the conveners of the annual American Astronomical Society's Division for Planetary Sciences meeting handed out with the registration materials a business‐ card‐sized “cheat sheet” chock full of handy facts and figures on the physical and orbital properties of the Sun and planets, including a useful list of physical constants and simple formulae for solar system astronomy Along with (I confess) my similarly sized versions of the periodic table and geologic timescale that I have tucked away in my wallet, these form some of my most useful and handy sources of reference information for quick answers to typical questions that arise in planetary science.

Two new books have recently been written that serve similar purposes, though each at a different and higher level, for students and others interested in planetary science. The first is the incredibly comprehensive and well‐organized The Planetary Scientist's Companion by Katharina Lodders and Bruce Fegley Jr. The authors, active and well‐respected planetary scientists themselves, have responded well to the need within the community for a single compendium of current and useful data, formulae, and pithy synopses of information on the geology, geochemistry, interiors, and (where appropriate) atmospheric compositions of the objects in our solar system.
Bill would expand ocean exploration
Authors: Showstack Randy
Published: October 2006

Legislation introduced by U.S. Congressman James Greenwood (R‐Penn.) on June 9 could lead to increased study and exploration of the world's oceans.

“The Exploration of the Seas Act” (House Resolution 2090) would direct the Secretary of Commerce to contract with the National Academy of Sciences to establish a Coordinated Oceanographic Program Advisory Panel to report to Congress on the adoption and establishment of an international effort to explore the potential of the oceans.
SOS over the Southeast
Authors: Showstack Randy
Published: October 2006

Scientists from U.S. government agencies and academia who are involved with the Southern Oxidants Study (SOS) are collecting air samples from mid‐June to mid‐July to assess the physical and chemical characteristics of fine particulate matter and ozone in parts of the southeastern United States.

They hope the study will provide a better understanding of some of the basic chemical, meteorological, and transport processes that cause air pollution—especially in areas that are hot and humid, with stagnant air and natural emissions of hydrocarbons from rural and urban forests. Scientists say that air pollution in these areas can damage crops and forests and affect human health and scenic visibility.
Wallace receives 1999 Roger Revelle medal
Authors: Lau Ngar‐Cheung , Wallace John Michael
Published: October 2006

John Michael Wallace was awarded the 1999 Roger Revelle Medal at the AGU Spring Meeting Honors Ceremony, which was held on June 2,1999, in Boston, Massachusetts. The medal recognizes outstanding accomplishments or contributions toward an understanding of the Earth's atmospheric processes, including its dynamics, chemistry, and radiation, or the role of atmosphere, atmosphere‐ocean coupling, or atmosphere‐land coupling in determining the climate, biogeochemical cycles, or other key elements of the integrated climate system.
Weighing a dam's economic and environmental impact
Authors: Showstack Randy
Published: October 2006

While some people claim that it was a publicity stunt or criticize it as an economic loss and a move in the wrong direction, the breaching of the low‐slung Edwards Dam on July 1 has changed the landscape of the Kennebec River flowing through Augusta, Maine, and may also change the landscape for some other dammed rivers nationwide.

The breaching marks the first time that the Federal Energy Regulatory Commission (FERC), which licenses nonfederal hydroelectric projects, has ruled that a dam should be removed because the environmental damage that it causes outweighs its economic benefits.
Hot air and Congress
Authors: Balco Greg
Published: October 2006

Bruce Doe's article, “A Potomac Perspective on the Growing Global Greenhouse” (Eos, January 5, 1999), contained the provocative suggestion that temperature in the Washington, D.C., region might be causally linked to congressional attention to the topics of greenhouse warming and global climate change, as well as federal funding for research into these topics. This assertion is particularly interesting in light of recent archaeological and paleoclimatic studies that suggest a link between large‐scale regional climate change and major events in ancient civilizations. For example, the collapses of the Akkadian Empire, the Minoan civilization in Crete, the Old Kingdom of Egypt, and the Mayan civilization in Mexico appear to coincide with major regional climate changes, suggesting that climatic factors might be more important than previously proposed sociopolitical ones in explaining the history of these cultures (see, for example, K. Wright's article, “Empires in the Dust,” in Discover, March 1998).

If a connection between climate and politics could be demonstrated in our own society, it might shed light on these past events. However, Doe did not further explore this possibility, presumably because of the lack of an appropriate quantitative measurement of legislative activity that could be compared to the temperature record.
Gulf of Mexico report card
Authors: Showstack Randy
Published: October 2006

The Gulf of Mexico's 4 million km2 drainage area in the United States pours an average of 27,473 cubic meters per second of freshwater into the gulf. Mixed in with that water flow are nutrients and sediment contaminants that affect the health of the gulf.

A November 23 report on the ecological condition of U.S. estuaries that drain into the gulf finds that eutrophication is one of the most critical problems facing gulf coastal ecosystems, with many gulf estuaries—particularly those in Louisiana and Texas—showing evidence of pre‐eutrophic or eutrophic conditions.
The Chi‐Chi, Taiwan earthquake: Large surface displacements on an inland thrust fault
Authors: Ma Kuo‐Fong , Lee Chyi‐Tyi , Tsai Yi‐Ben , Shin Tzay‐Chyn , Mori Jim
Published: October 2006

In the early morning (01:47 local time) of September 21, 1999, the largest earthquake of the century in Taiwan (Mw=7.6, ML=7.3) struck the central island near the small town of Chi‐Chi. The hypocenter was located by the Central Weather Bureau Seismological Center at 23.87°N, 120.75°E, with a depth of about 7 km.

There were extensive surface ruptures for about 85 km along the Chelungpu fault with vertical thrust and left lateral strike‐slip offsets. The maximum displacement of about 9.8 meters is among the largest fault movements ever measured for modern earthquakes. There was severe destruction in the towns of Chungliao, Nantou,Taichung, FengYuan, and Tungshi, with over 2300 fatalities and 8700 injuries.
When to celebrate the end of the century
Authors: Warren Bruce A.
Published: October 2006

I was saddened to read an ad for AGU's Fall Meeting that described it as “the last geophysical meeting to be held in this century” It is not. “This” century (the twentieth) ends on December 31, 2000. If scientists aren't sure what the word “century” means or have difficulty counting off intervals of one hundred, starting at one, how can we ever expect the news media and general public to get things right?

Some say this is just a matter of semantics or religious significance. Not so: it is about consistent definitions and counting—something scientists are supposed to care about and attend to.
Three‐dimensional radiative transfer makes its mark
Authors: Davis Anthony B. , Marshak Alexander , Kassianov Evgueni , Stokes Gerald M.
Published: October 2006

Clearly atmospheric three‐dimensional (3‐D) radiative transfer has crossed the invisible but important threshold that makes it a subject of scientific interest in its own right, and this transition happened almost without anyone noticing. It took an AGU Spring Meeting special session this year on the topic to come to this realization. The outcome was a pleasant surprise for all involved.

Three‐dimensional radiative transfer is traditionally viewed as a rather specialized subtopic, generally subordinated to some well‐defined application. Consider, for instance, this question: “What is the effect of unresolved horizontal variability in cloud structure on energy budgets in general circulation models (GCMs); that is, on fluxes at the grid‐cell scale? “This is clearly an important issue and was addressed head‐on by Bob Cahalan and Graeme Stephens. The answer currently is anticipated in the form of a bias with respect to predictions based on the standard horizontally uniform cloud models implemented in the GCM parameterizations; this way, fluxes can be readily corrected for 3‐D effects.
Differential analysis of secondary metabolites by LC–MS following strain improvement of Streptomyces lydicus AS 4.2501
Authors: Li Xiao‐Bing , Qiao Bin , Yuan Ying‐Jin
Published: October 2006

Metabolite variations in a high‐yielding mutant and its parent strain were studied by comparative LC–MS analysis after strain improvement. Streptomyces lydicus AS 4.2501‐P28, a propionate‐resistant mutant isolated by the high‐frequency screening method using the principle of eliminating precursor inhibition effects, showed an increase of 267% in streptolydigin titre over the starting strain. Culture extracts of this mutant and its parent strain were analysed in parallel by an LC‐MS technique, including full scan and extracted‐ion scan, ESI‐MS (electrospray‐ionization MS) detection, DAD (diode‐array detection) and MS2 (tandem MS) measurement. The main metabolic variations were obviously found in intermediates, metabolites and biosynthetic pathways: two unknown metabolites with the molecular [M−H]− ions at m/z 423.3 and 687.2, corresponding to two branch pathways, were blocked in the mutant, and the accumulation of a significant intermediate at m/z 363.1 [M−H]− decreased dramatically in the mutant cultures, resulting in the overproduction of streptolydigin (an antibiotic that inhibits prokaryotic RNA polymerase) in the mutant. Ion fragmentations of the tandem‐MS spectra provided experimental evidence for the structural characterization of the three compounds obtained. In comparison with the traditional methods, comparative LC–MS analysis was rapid, sensitive and suitable for characterizing intermediates, metabolites and pathways for elucidation of the metabolic alterations after the isolation of improved strains.
Bacterial protein toxins and lipids: pore formation or toxin entry into cells
Authors: Geny Blandine , Popoff Michel R.
Published: October 2006

Lipids are hydrophobic molecules which play critical functions in cells, in particular, they are essential constituents of membranes, whereas bacterial toxins are mainly hydrophilic proteins. All bacterial toxins interact first with their target cells by recognizing a surface receptor, which is either a lipid or a lipid derivative, or another compound but in a lipid environment. Most bacterial toxins are PFTs (pore‐forming toxins) which oligomerize and insert into the lipid bilayer. A common mechanism of action involves the formation of a β‐barrel structure, resulting from the assembly of individual β‐hairpin(s) from individual monomers. An essential step for intracellular active toxins is to translocate their enzymatic part into the cytosol. Some toxins use a translocation mechanism based on pore formation similar to that of PFTs, others undergo a yet unclear ‘chaperone’ process.
Entangled trajectory dynamics in the Husimi representation
Authors: López Hender , Martens Craig C. , Donoso Arnaldo
Published: October 2006

We solve quantum dynamical equations of simple systems by propagating ensembles of interacting trajectories. A scheme is proposed which uses adaptive kernel density estimation for representing probability distribution functions and their derivatives. The formulation is carried on in the Husimi representation to ensure the positiveness of the distribution functions. By comparing to previous work, the effect of changing representations is studied as well as the advantage of using adaptive kernels for the estimation of probability distributions. We found significant improvement in the accuracy of the results.
Monoenergetic proton backlighter for measuring E and B fields and for radiographing implosions and high-energy density plasmas (invited)
Authors: Li C. K. , Séguin F. H. , Frenje J. A. , Rygg J. R. , Petrasso R. D. , Town R. P. J. , Amendt P. A. , Hatchett S. P. , Landen O. L. , Mackinnon A. J. , Patel P. K. , Smalyuk V. A. , Knauer J. P. , Sangster T. C. , Stoeckl C.
Published: October 2006

A novel monoenergetic proton backlighter source and matched imaging detector have been utilized on the OMEGA laser system to study electric (E) and magnetic (B) fields generated by laser-plasma interactions and will be utilized in the future to radiograph implosions and high-energy density (HED) plasmas. The backlighter consists of an imploding glass microballoon with DHe3 fuel, producing 14.7MeV DHe3 protons and 3MeV DD protons that are then passed through a mesh that divides the protons into beamlets. For quantitative study of E+B field structure, monoenergetic protons have several unique advantages compared to the broad energy spectrum used in previous experiments. Recent experiments have been performed with a single laser beam (intensity of ∼1014W∕cm2) interacting with a CH foil, and B fields of ∼0.5MG and E fields of ∼1.5×108V∕m have been measured using proton deflectometry. LASNEX simulations are being used to interpret these experiments. Additional information will also be presented on the application of this technique to measuring E and B fields associated with Hohlraums and directly driven implosions, to radiographically mapping the areal density (ρR) distribution in imploded capsules, and to radiographing HED plasmas.
Imaging of high-speed dust particle trajectories on NSTX
Authors: Roquemore A. L. , Davis W. , Kaita R. , Skinner C. H. , Maqueda R. , Nishino N.
Published: October 2006

Imaging of high-speed incandescent dust particle trajectories in a tokamak plasma has been accomplished on NSTX using up to three high-speed cameras each viewing the same plasma volume from different locations and operating at speeds up to 68000frames∕s with exposure times varying from 2to300μs. The dynamics of the dust trajectories can be quite complex exhibiting a large variation in both speed (10–200m∕s) and direction. Simulations of these trajectories will be utilized to ascertain the role dust may play in future machines such as ITER where significant dust production from wall erosion is expected. NSTX has numerous view ports including both tangential as well as radial views in both the midplane and lower divertors. Several vertical ports are also available so that a few specific regions in NSTX may be viewed simultaneously from several different camera positions. The cameras can be operated in the full visible spectrum but near-infrared filters can be utilized to enhance the observation of incandescent particles against a bright background. A description of the cameras and required optics is presented.
New diagnostic systems on HL-2A
Authors: Ding X. T. , Zhou Y. , Deng Z. C. , Xiao W. W. , Liu Z. T. , Shi Z. B. , Yan L. W. , Hong W. Y. , Yang Q. W.
Published: October 2006

Three new diagnostic systems have been presented in this article: (1) the pulse molecular beam injection as a modulated particle source and microwave reflectometry for investigation of the particle transport, (2) a new three-step electrostatic probe array for zonal flow studying, and (3) eight-channel laser interferometer with 6m HCN laser for electron density profile measurement with good spatial resolution. The main experimental results have also been shown briefly.
Dust particle dynamics in low-pressure plasma reactor
Authors: Davoudabadi M. , Mashayek F.
Published: October 2006

In this paper, the structure of a rf plasma glow discharge in a parallel-plate geometry is revisited through a numerical solution of the well-known local field approximation model equations. The dynamics of a dust particle injected into the plasma is elaborated in a Lagrangian framework by solving the particle equations for its motion and charge. Different ion drag expressions are considered. For particles of three different sizes, magnitudes of various forces such as gravity, electricity, and ion drag acting on a stationary particle are compared to each other. Particle potential energy, together with its possible wells, is demonstrated for each case. Taking into account the neutral drag force, damping oscillations and final locations of the particles, depending on their initial injection position (top or bottom), are captured. The transient characteristic of the charging process of smaller particles with respect to their motion time scale is discussed. The effect of inclusion of ion thermal energy in the calculation of drag force on the motion of the particle is illustrated.
High-order excitations in state-universal and state-specific multireference coupled cluster theories: Model systems
Authors: Evangelista Francesco A. , Allen Wesley D. , Schaefer Henry F.
Published: October 2006

For the first time high-order excitations (n>2) have been studied in three multireference couple cluster (MRCC) theories built on the wave operator formalism: (1) the state-universal (SU) method of Jeziorski and Monkhorst (JM) (2) the state-specific Brillouin-Wigner (BW) coupled cluster method, and (3) the state-specific MRCC approach of Mukherjee (Mk). For the H4, P4, BeH2, and H8 models, multireference coupled cluster wave functions, with complete excitations ranging from doubles to hextuples, have been computed with a new arbitrary-order string-based code. Comparison is then made to corresponding single-reference coupled cluster and full configuration interaction (FCI) results. For the ground states the BW and Mk methods are found, in general, to provide more accurate results than the SU approach at all levels of truncation of the cluster operator. The inclusion of connected triple excitations reduces the nonparallelism error in singles and doubles MRCC energies by a factor of 2–10. In the BeH2 and H8 models, the inclusion of all quadruple excitations yields absolute energies within 1kcalmol−1 of the FCI limit. While the MRCC methods are very effective in multireference regions of the potential energy surfaces, they are outperformed by single-reference CC when one electronic configuration dominates.
Hydrogen-bond dynamics and Fermi resonance in high-pressure methane filled ice
Authors: Klug D. D. , Tse J. S. , Liu Zhenxian , Hemley Russell J.
Published: October 2006

High-pressure, variable temperature infrared spectroscopy and first-principles calculations on the methane filled ice structure (MH-III) at high pressures are used to investigate the vibrational dynamics related to pressure induced modifications in hydrogen bonding. Infrared spectroscopy of isotopically dilute solutions of H2O in D2O is employed together with first-principles calculations to characterize proton dynamics with the pressure induced shortening of hydrogen bonds. A Fermi resonance is identified and shown to dominate the infrared spectrum in the pressure region between 10 and 30GPa. Significant differences in the effects of the Fermi resonance observed between 10 and 300K arise from the double-well potential energy surface of the hydrogen bond and quantum effects associated with the proton dynamics.
The interplay between discrete noise and nonlinear chemical kinetics in a signal amplification cascade
Authors: Lan Yueheng , Papoian Garegin A.
Published: October 2006

We used various analytical and numerical techniques to elucidate signal propagation in a small enzymatic cascade which is subjected to external and internal noises. The nonlinear character of catalytic reactions, which underlie protein signal transduction cascades, renders stochastic signaling dynamics in cytosol biochemical networks distinct from the usual description of stochastic dynamics in gene regulatory networks. For a simple two-step enzymatic cascade which underlies many important protein signaling pathways, we demonstrated that the commonly used techniques such as the linear noise approximation and the Langevin equation become inadequate when the number of proteins becomes too low. Consequently, we developed a new analytical approximation, based on mixing the generating function and distribution function approaches, to the solution of the master equation that describes nonlinear chemical signaling kinetics for this important class of biochemical reactions. Our techniques work in a much wider range of protein number fluctuations than the methods used previously. We found that under certain conditions the burst phase noise may be injected into the downstream signaling network dynamics, resulting possibly in unusually large macroscopic fluctuations. In addition to computing first and second moments, which is the goal of commonly used analytical techniques, our new approach provides the full time-dependent probability distributions of the colored non-Gaussian processes in a nonlinear signal transduction cascade.
Temperature dependence of the direct piezoelectric effect in relaxor-ferroelectric single crystals: Intrinsic and extrinsic contributions
Authors: Davis Matthew , Damjanovic Dragan , Setter Nava
Published: October 2006

The direct piezoelectric response d33 of [001]C-poled 0.955Pb(Zn1∕3Nb2∕3)O3–0.045PbTiO3 [PZN-4.5PT] and 0.98Pb(Zn1∕3Nb2∕3)O3–0.08PbTiO3 [PZN-8PT] has been investigated as a function of temperature upon heating above 40°C to the paraelectric phase. Using a Rayleigh-law based analysis, it is shown that both the reversible/intrinsic and irreversible (extrinsic) contributions to the response increase in both compositions as the phase transition to a tetragonal phase is approached. The latter is likely due to an increased domain wall mobility close to the first order transition temperature, which also gives rise to an increased frequency dispersion. Large reversible direct piezoelectric responses d33>1600pm∕V are observed for both compositions, which increase dramatically close to the transition temperature. Most importantly, the reversible contribution is always much larger than the irreversible part in the low temperature, domain-engineered phase, the latter accounting for around 20% of the response in PZN-8PT, at 40°C, and 5% in PZN-4.5PT. The importance of this result to the validity of the adaptive phase model is discussed.
Analytical expressions for the magnetization curves of a magnetic-tunnel-junction-like system
Authors: Layadi A.
Published: October 2006

Magnetization curves are predicted for a magnetic-tunnel-junction-like system in some special cases of interest: (i) weak interlayer magnetic coupling/high exchange anisotropy field HE and (ii) strong coupling/low HE. Analytical expressions for different switching fields are derived in these situations. These fields depend on the magnetizations (MA,MB) and thicknesses (tA,tB) of the two ferromagnetic layers, on the bilinear (J1) and biquadratic (J2) coupling parameters, and on the exchange (HE) and uniaxial (HA) anisotropy fields of the pinned layer. In the first case, the whole system is found to behave as two uncoupled layers with equivalent exchange and planar anisotropy fields. The effect of the biquadratic coupling J2 on the hysteresis curves is discussed for both ferromagnetic and antiferromagnetic coupling cases. In the second case, the system behaves as a single (ferromagnetic/antiferromagnetic) bilayer with effective exchange and magnetocrystalline anisotropy fields. These findings confirm some of the results inferred from a ferromagnetic resonance analysis and previously reported.
Validity/invalidity of Schottky-Mott rules for Schottky contacts to III-V nitride semiconductor heterostructures
Authors: Lu Changzhi , Mohammad S. Noor
Published: October 2006

Carrier transport through the metal/semiconductor and metal/semiconductor/semiconductor (M∕S∕S) Schottky contact interfaces has been studied. Metal/n-GaN, metal/n-AlxGa1−xN, and metal/n-AlxGa1−xN∕n-GaN diodes have been chosen for the study. It has been observed that, owing to the presence of the piezoelectric polarization field and a quantum well at the AlxGa1−xN∕GaN interface, the AlxGa1−xN∕GaN contacts exhibit properties distinctly different from those of the AlxGa1−xN contacts. The superiority of the AlxGa1−xN∕GaN contacts to that of the AlxGa1−xN contacts largely disappears at high temperatures. While the GaN and AlxGa1−xN contacts appear to obey the Schottky-Mott rule, the AlxGa1−xN∕GaN contacts tend to disobey it.
Fundamental limits of all nonlinear-optical phenomena that are representable by a second-order nonlinear susceptibility
Authors: Kuzyk Mark G.
Published: October 2006

Applying the three-level ansatz and the sum rules to the new dipole-free sum-over-states expression, we develop a rigorous method for calculating the fundamental limits of the dispersion of the real and imaginary parts of the second-order electronic nonlinear-optical susceptibilities. These results can be applied to all orders of nonlinearity, hence can be used to study any nonlinear-optical phenomena at any wavelength. The theory can be used to understand how strongly light interacts with matter and can be applied to optimizing a material’s properties for applications. In particular, we find that the resonant first hyperpolarizability peaks when the energy difference between excited states is small. In contrast, the maximal off-resonance hyperpolarizability requires the excited states to be well separated. Therefore, one molecular design strategy does not fit all applications.
Structural stability and elastic property of the L12 ordered Co3(Al,W) precipitate
Authors: Yao Q. , Xing H. , Sun J.
Published: October 2006

The method of augmented plane wave plus local orbitals within the generalized gradient approximation has been employed to investigate the structural stability and elastic properties of the ternary Co3(Al,W) precipitate. The results showed that the stable Co3(Al,W) compound has L12 ordered structure. The calculated results of elastic properties show that the L12 Co3(Al,W) precipitate has a strengthening effect in the disordered fcc cobalt matrix, owing to the larger modulus differences between Co3(Al,W) and cobalt matrix. The theoretical calculations also show that the Co3(Al,W) compound is brittle in nature.
Large magnetoresistance in single-crystalline Ni50Mn50−xInx alloys (x=14–16) upon martensitic transformation
Authors: Yu S. Y. , Liu Z. H. , Liu G. D. , Chen J. L. , Cao Z. X. , Wu G. H. , Zhang B. , Zhang X. X.
Published: October 2006

Variation of electrical resistance in single-crystalline Ni50Mn50−xInx alloys (x=14–16) upon martensitic transformation was investigated. In Ni50Mn35In15 with Tm∼295K, a negative magnetoresistance (MR) over 60% is attainable at moderate field strengths; in Ni50Mn34In16 with Tm∼190K, the MR can exceed 70% over a temperature of approximately 100K. The significant change in electric resistance upon martensitic transformation originates primarily from the altered electronic structure, while the large effect of a magnetic field follows its ability to manipulate the transformation in materials of low Tm and large ΔM∕ΔS. The extremely large MR promises more innovative applications for these important alloys.
Air-stable n-channel copper hexachlorophthalocyanine for field-effect transistors
Authors: Ling Mang-Mang , Bao Zhenan , Erk Peter
Published: October 2006

The authors report air-stable n-channel transistor performance of copper hexachlorophthalocyanine (Cl16CuPc) organic semiconductor. The charge carrier mobility is about 0.01cm2∕Vs for thin films deposited at an elevated substrate temperature. Effects of substrate temperature, substrate surface chemical treatment, thin film morphology, and crystallinity on device performance are investigated. No significant decrease in mobility and on/off ratio was observed for devices stored in ambient environment.
Origin of high oscillator strength in green-emitting InGaN∕GaN nanocolumns
Authors: Kawakami Y. , Suzuki S. , Kaneta A. , Funato M. , Kikuchi A. , Kishino K.
Published: October 2006

Optical characterization has been performed on an InGaN∕GaN nanocolumn structure grown by nitrogen plasma assisted molecular beam epitaxy not only in macroscopic configuration but also in a microscopic one that can be assessed to a single nanocolumn. The photoluminescence (PL) decay monitored at 500nm is fitted with a double exponential curve, which has lifetimes of 0.67 and 4.33ns at 13K. These values are two orders of magnitude smaller than those taken at the same wavelength in conventional InGaN∕GaN quantum wells (QWs) grown toward the C orientation. PL detection of each single nanocolumn was achieved using a mechanical lift-off technique. The results indicate that the very broad, macroscopically observed PL spectrum is due to the sum of the sharp PL spectrum from each nanocolumn, the peak energy of which fluctuates. Moreover, unlike conventional QWs, the blueshift of a single nanocolumn is negligibly small under higher photoexcitation. These findings suggest that carrier localization as well as the piezoelectric polarization field is suppressed in InGaN∕GaN nanocolumns.
Formation and characterization of silicon/carbon nanotube/silicon heterojunctions by local synthesis and assembly
Authors: Kawano Takeshi , Christensen Dane , Chen Supin , Cho Chung Yeung , Lin Liwei
Published: October 2006

This work investigates the formation of silicon/multiwalled carbon nanotube/silicon heterojunctions by in situ synthesizing carbon nanotubes between two heavily doped, suspended silicon microstructures that are separated 5–10μm apart using the techniques of localized heating and electric-field-assisted self-assembly. The local electric field has the strength of 0.2–1V∕μm. Tip- and root-grown carbon nanotubes are observed to form two different heterojunction morphologies at the tips as the former stop to grow and the latter continue to grow as the growth tips of carbon nanotubes reach the cold silicon. Experimental measurements of the silicon/carbon nanotube/silicon system show linear current-voltage characteristics indicating Ohmic contact behavior.
Luminescence properties of wurtzite AlN nanotips
Authors: Shi Shih-Chen , Chen Chia Fu , Chattopadhyay Surojit , Chen Kuei-Hsien , Ke Bo-Wen , Chen Li-Chyong , Trinkler Laima , Berzina Baiba
Published: October 2006

The optical properties of aluminum nitride nanotips (AlNNTs) synthesized via vapor transport and condensation process have been studied by cathodoluminescence, photoluminescence (PL), thermoluminescence (TL), and UV absorption measurements. Two defect related transitions around 2.1 and 3.4eV and an excitonic feature at 6.2eV were identified. Compared to the AlN macropowders, the AlNNTs showed a blueshift (+0.2eV) of the ∼3.2eV peak. Analysis of both PL and TL excitation measurements indicated the existence of subband gap multiple energy levels in AlNNTs. A significant TL intensity even at 145°C suggests possible ultraviolet detector and dosimetric applications of these AlNNTs.
‘When, Where, if, and but’: Qualifying GIS and the Effect of Streetlighting on Crime and Fear
Authors: Pain Rachel , MacFarlane Robert , Turner Keith , Gill Sally
Published: October 2006

Geographical information systems (GIS) are increasingly used in England and Wales as a tool to monitor crime and aid community-safety planning. This is despite the widely known limitations of police-recorded data on crime victimisation, and concerns about the quality and specificity of available data on fear of crime. Meanwhile, improving streetlighting is a popular strategy both for improving community safety and for reducing fear of crime. In this paper we report on research carried out in Northumberland, northeast England, which aimed to identify locations most in need of new streetlighting. First, GIS crime hotspot maps and lighting coverage maps were analysed to identify potential areas to target. Qualitative rapid appraisal techniques were then used in these areas to explore local residents' perceptions and understandings of the relationships between streetlighting, victimisation, and fear of crime. The qualitative data were used to interpret the hotspot maps further, and to inform the location and type of streetlighting interventions. The research demonstrates that people's experiences of crime and fear, and their understandings of the relationships these have to streetlighting, are complex and reflective. At most, streetlighting was held to have a marginal and even then contradictory influence on the problems of crime and fear that people face. The implications are considered. We conclude that qualifying the outputs of GIS mapping was essential in this case, and has wide potential in critical policy research to promote more inclusive knowledge and more effective decisionmaking.