bluuebunny/crossref_metadata_2025 huggingface dataset:
Numerical simulations of grass fires using a coupled atmosphere‐fire model: Dynamics of fire spread
Authors: Cunningham Philip , Linn Rodman R.
Published: March 2007

Numerical simulations using a coupled atmosphere‐fire model (called HIGRAD/FIRETEC) are examined to investigate the dynamics of fire behavior in grasslands, focusing specifically on the relative roles and contributions of radiative and convective heat transfer and the relationships of these processes to the evolution of the solid fuel temperature; the three‐dimensional velocity fields in the vicinity of the fire; and the depletion of fuel, fuel moisture, and oxygen. The progression of the fire past a given point in these simulations is divided into a preheating period and an active burning period. The preheating period is characterized by a slowly increasing radiative heating of the fuel that evaporates fuel moisture and raises the temperature of the fuel slightly and by weak convective cooling because the gases flowing over the heated solid fuel are still cooler than the fuel itself. The active burning period is characterized by the presence of a strong pulse of convective heating and continued radiative heating, accompanied by the development of large vertical velocities and a rapid increase in fuel temperature that causes the reaction rates to increase and the fuel to begin to burn, producing heat and increasing the rates of depletion of fuel and oxygen. In all simulations, the magnitude of the convective heat transfer is greater than that of the radiative heat transfer; however, these processes and their relationships to the three‐dimensional structure and evolution of the fire are shown to depend both on the ambient wind speed and on the specific location along the fire front (e.g., at the head of the fire where the fire is spreading in the direction of the ambient wind, or on the flank of the fire where the fire is spreading in the direction almost perpendicular to the ambient wind).
Spatial‐scale partitioning of in situ turbulent flow data over a pebble cluster in a gravel‐bed river
Authors: Lacey R. W. Jay , Legendre Pierre , Roy André G.
Published: March 2007

Spatial structures within turbulent flow data were investigated through the use of a new multivariate variation partitioning analysis technique involving principal coordinates of neighbor matrices (PCNM), which is a form of distance‐based eigenvector maps (DBEM). The analysis revealed a significant (α = 0.01) spatial dependence, 58%, for the mean and turbulent flow variables. The flow variables were obtained from instantaneous two‐dimensional velocities collected in situ along a streamwise section that crosses over a pebble cluster in a gravel‐bed river. Using the orthogonal property of the PCNM variables, the explained variation was partitioned over four significant (α = 0.01) spatial scales: very large (VL, 17%), large (L, 24%), medium (M, 6%) and fine (F, 2%). Nearly 75% of the variance of the main turbulent flow indicators, such as the root‐mean‐square of the streamwise and vertical velocity components and the mean uv component Reynolds shear stress, was explained by the VL‐ and L‐scale PCNM submodels, which have streamwise and vertical length scales of the order of Δx = 5.3H − 2.6H and Δy = 1.0H − 0.5H (where H is the flow depth), respectively. Through a multivariate mapping procedure, clear spatial patterns within the explained flow variables emerge around the cluster, where the flow separation zone seems to play a significant role at a range of scales. As well, intervariable correlations at each spatial scale, obtained through eigenvector scatterplots, show intricate relationships between the flow variables. The interdependence of the Reynolds shear stress and the u component turbulent energy is much stronger at the VL scale than at the L and M scales. The application of PCNM analysis on the turbulent flow field shows the power of the technique to resolve the relevant spatial scales and patterns, and demonstrates its potential use in a variety of water resources studies.
Environmental Radiochemical Analysis II
Authors: Ware Anthony
Published: March 2007

Environmental Radiochemical Analysis II brings together comprehensive, up-to-date information from international experts in the field. Coverage includes information on new methods of radionuclide analyses, developments and improvements in existing methods, method comparisons, gamma detector performance and new software products, method uncertainty, underground laboratory facilities, method QA and QC, field studies covering colloid work, in-situ injection into rock strata and sampling of reduced waters for actinide assay. This stimulating, authoritative text makes essential reading for practising radioanalysts and provides valuable information for researchers and professionals in academia and industry.
Magnetic Resonance in Food Science
Authors: Amin Maryam Haifeng Gao , Berg Frans van den , Bonny Jean-Marie , Bro Rasmus , Capozzi Francesco , Duus Jens , Falch Eva , Ferreira Antonio Gilberto , Gostan Thierry , Hills Brian , Howell Nazlin , Hubbard Penny , Jaroszewski Jerzy , Kenne Lennart , Lee Cherl-Ho , Martin Gerard , Mohoric Ales , Nestle Nikolaus , Pusiol Daniel , Rezzi Serge , Rolls Edmund T , Shaarani Sharifudin M D , Sorland Geir Humborstad , Trezza Elena , Veliyulin E Emil , Wind Robert A , Spraul Manfred
Published: March 2007

The scope of applications of magnetic resonance to food science continues to expand. Recently, the focus has turned to the way in which the interpretation and quantification of magnetic resonance data of complex food systems increasingly requires the application of multivariate data analytical protocols. This book provides an up-to-date, global perspective of the latest developments in the field, including methods of studying metabolic processes both in vivo and in vitro, functional MRI and the sensory perception of food. Content is divided into five sections: sensory science; aroma and flavour; authenticity and quantification of food; functionality, structure and ingredients; applications of solid-state methods; and new NMR methods and instrumentation. Magnetic Resonance in Food Science: The Multivariate Challenge is ideal for graduates and researchers as well as for academics and professionals in the field.
Food Colloids
Authors: Foegeding Allen E , Dalgleish D G , Lakemond C M M , Pouzot Matthieu , Donato L , De Kruif C G , Ettelaie Rammile , Gunning Patrick , Cohen Stuart Martien A , Miller Reinhard , Wilde Peter J , Pezennec Stephane , Rodriguez Patino Juan M , Singh Harjinder , Panouille M , Semenova Maria G , Helstad Kristina M , Corredig Milena , Arnaudov Luben N , Linden Erik , Murray Brent S , Saint-Jalmes A , Schmitt Christophe , Pilosof Ana M R , Van Vliet Ton , McClements Julian D , Booth David A , Van Aken George A , Tornberg Eva , Luyten Hannemieke , Grati Nissim , Watson Andrew D , Horne David S , Laneuville Sandra I , Pacek A W
Published: March 2007

Food Colloids: Interactions, Microstructure and Processing describes the principles and practice underlying the formulation of food emulsions, dispersions, gels, and foams. Emphasis is on understanding how the functional properties of biopolymers and surfactants determine the texture and shelf-life of multiphase food materials. This book provides essential new findings by experts in the field on specific topics including: the interfacial rheological properties of proteins; the use of microscopy and image analysis to probe structure and phase transitions; the control of colloidal stability during thermal and mechanical processing; the interactions of proteins with polysaccharides and emulsifiers; the incorporation of neutraceuticals into food colloids; and the consumer perception of taste and texture. Food Colloids: Interactions, Microstructure and Processing provides a link between current research on the fundamental physical chemistry of colloidal systems and the requirements of the food technologist to use modern colloid science in new product formulation. It is suitable for postgraduates and researchers, both in industry and academia.
Suitability of a Combined Stomatal Conductance and Photosynthesis Model for Calculation of Leaf‐Level Ozone Fluxes
Authors: de Beeck M. Op , Löw M. , Verbeeck H. , Deckmyn G.
Published: March 2007

Abstract: Currently, the most important source of uncertainty in stomatal ozone flux (FO3) modelling is the stomatal conductance (gst) factor. Hence FO3 model accuracy will strongly depend on the gst model being implemented. In this study the recently developed semi‐empirical gst model of Dewar was coupled to the widely known biochemical photosynthesis (An) model of Farquhar. The gst performance of this model combination was evaluated with a 4‐month time series of beech (Fagus sylvatica L.) measurements. The gst model was hereto optimized in two steps to a 4‐day and a 8‐day period. A comparison between the modelled and measured gst to O3 (gstO3) revealed a rather good overall performance (R2= 0.77). Errors between the model combination and the measurements are thought to be largely caused by a moderate performance of the An model, due to poor parameterization. Two 2‐day periods with distinctly differing soil and meteorological conditions were chosen to give a picture of the daily gst performance. Although instant relative differences between modelled and measured gstO3 are sometimes high, the model combination is able to simulate the rough daily courses of gstO3 and hence FO3 reasonably well. Further improvement on full parameterization of the gst model and a well‐parameterized An model to be linked to are needed to draw founded conclusions about its performance. Future efforts hereto are certainly justified since the model's mechanistic nature makes it a tool able to model gst variation in space and time, O3 effects on gst, and effective FO3.
Significance of Ozone Exposure for Inter‐Annual Differences in Primary Metabolites of Old‐Growth Beech (Fagus sylvatica L.) and Norway Spruce (Picea abies L.) Trees in a Mixed Forest Stand
Authors: Alexou M. , Hofer N. , Liu X. , Rennenberg H. , Haberer K.
Published: March 2007

Abstract: The influence of long‐term free‐air ozone fumigation and canopy position on leaf contents of total glutathione, its redox state, non‐structural proteins (NSP), soluble amino compounds, and total soluble sugars in old‐growth beech (Fagus sylvatica) and spruce (Picea abies) trees were determined over a period of five years. Ozone fumigation had weak effects on the analysed metabolites of both tree species and significant changes in the contents of total glutathione, NSP, and soluble sugars were observed only selectively. Beech leaves were affected by crown position to a higher extent than spruce needles and exhibited lower contents of total glutathione and NSP and total soluble sugars, but enhanced contents of oxidised glutathione and amino compounds in the shade compared to the sun crown. Contents of total soluble sugars generally were decreased in shade compared to sun needles of spruce trees. Interspecific differences between beech and spruce were more distinct in the sun compared to the shade crown. Contents of total glutathione were increased whilst contents of amino compounds and total soluble sugars were lower in spruce needles compared to beech leaves. The metabolites determined showed individual patterns in the course of the five measurement years. Contents of total glutathione and its redox state correlated with air temperature and global radiation, indicating an important role for the antioxidant at low temperatures. Correlations of glutathione with instantaneous ozone concentrations seem to be a secondary effect. Differences in proteins and/or amino compounds in the inter‐annual course are assumed to be a consequence of alterations in specific N uptake rates.
CASIROZ: Root Parameters and Types of Ectomycorrhiza of Young Beech Plants Exposed to Different Ozone and Light Regimes
Authors: Železnik P. , Hrenko M. , Then C. , Koch N. , Grebenc T. , Levanič T. , Kraigher H.
Published: March 2007

Abstract:Tropospheric ozone (O3) triggers physiological changes in leaves that affect carbon source strength leading to decreased carbon allocation below‐ground, thus affecting roots and root symbionts. The effects of O3depend on the maturity‐related physiological state of the plant, therefore adult and young forest trees might react differently. To test the applicability of young beech plants for studying the effects of O3on forest trees and forest stands, beech seedlings were planted in containers and exposed for two years in the Kranzberg forest FACOS experiment (Free‐Air Canopy O3Exposure System,http:www.casiroz.de) to enhanced ozone concentration regime (ambient [control] and double ambient concentration, not exceeding 150 ppb) under different light conditions (sun and shade). After two growing seasons the biomass of the above‐ and below‐ground parts, beech roots (using WinRhizo programme), anatomical and molecular (ITS‐RFLP and sequencing) identification of ectomycorrhizal types and nutrient concentrations were assessed. The mycorrhization of beech seedlings was very low (ca.5 % in shade, 10 % in sun‐grown plants), no trends were observed in mycorrhization (%) due to ozone treatment. The number ofCenococcum geophilumtype of ectomycorrhiza, as an indicator of stress in the forest stands, was not significantly different under different ozone treatments. It was predominantly occurring in sun‐exposed plants, while its majority share was replaced byGenea hispidulain shade‐grown plants. Different light regimes significantly influenced all parameters except shoot/root ratio and number of ectomycorrhizal types. In the ozone fumigated plants the number of types, number of root tips per length of 1 to 2 mm root diameter, root length density per volume of soil and concentration of Mg were significantly lower than in control plants. Trends to a decrease were found in root, shoot, leaf, and total dry weights, total number of root tips, number of vital mycorrhizal root tips, fine root (mass) density, root tip density per surface, root area index, concentration of Zn, and Ca/Al ratio. Due to the general reduction in root growth indices and nutrient cycling in ozone‐fumigated plants, alterations in soil carbon pools could be predicted.
Antioxidative Defence of Old Growth Beech (Fagus sylvatica) under Double Ambient O3 Concentrations in a Free‐Air Exposure System
Authors: Haberer K. , Herbinger K. , Alexou M. , Tausz M. , Rennenberg H.
Published: March 2007

Abstract: In this study the influence of chronic free‐air ozone exposure and of different meteorological conditions in the very dry year 2003 and the more humid year 2004 on the antioxidative system in sun and shade leaves of adult Fagus sylvatica trees were investigated. Contents of ascorbate, glutathione, and α‐tocopherol, as well as chloroplast pigments were determined under ambient (1 × O3) and double ambient (2 × O3) ozone concentrations. Ozone affected the antioxidative system in June and July, causing lower ascorbate contents in the apoplastic space, a more oxidized redox state of ascorbate and glutathione and an increase in pigment contents predominantly in the shade crown. For all measured parameters significant differences between the years were observed. In 2004 the redox state of ascorbate and glutathione was in a more reduced state and leaf contents of α‐tocopherol, pigments of the xanthophyll cycle, β‐carotene, lutein, neoxanthin, and α‐carotene were lower compared to 2003. Contents of total glutathione and chlorophyll a + b were increased in the second year. These results indicate a strong influence of the drought conditions in 2003 on the antioxidative system of beech overruling the ozone effects. Shade leaves showed lower contents of ascorbate in both years and the redox states of ascorbate and glutathione were more oxidized compared to sun leaves. Contents of photoprotective and accessory pigments generally were enhanced and the de‐epoxidation state of the xanthophyll cycle was lower in the shade compared to the sun crown. Exhibiting less antioxidants shade leaves seem to be more sensitive against ozone than sun leaves.
Evidence that Branch Cuvettes are Reasonable Surrogates for Estimating O3Effects in Entire Tree Crowns
Authors: Then& C. , Herbinger K. , Blumenröther M. , Haberer K. , Heerdt C. , Oβwald W. , Rennenberg H. , Grill D. , Tausz M. , Wieser G.
Published: March 2007

Abstract:Within the scope of quantifying ozone (O3) effects on forest tree crowns it is still an open question whether cuvette branches of adult trees are reasonable surrogates for O3responses of entire tree crowns and whether twigs exhibit autonomy in defense metabolism in addition to carbon autonomy. Therefore, cuvette‐enclosed branches of mature beech(Fagus sylvatica)trees were compared with branches exposed to the same and different ozone regimes by a free‐air fumigation system under natural stand conditions by means of avice versaexperiment. For this purpose, cuvettes receiving 1 × O3air were mounted in trees exposed to 2 × O3and cuvettes receiving 2 × O3air were mounted in trees exposed to 1 × O3in the upper sun crown. At the end of the fumigation period in September 2004, leaves were examined for differences in gas exchange parameters, pigments, antioxidants, carbohydrates, and stable isotope ratios. No significant differences in foliar gas exchange, total carbohydrates, stable isotope ratios, pigment, and antioxidant contents were found as a consequence of cuvette enclosure (cuvette versus free‐air branches) of the same O3concentrations besides increase of glucose inside the cuvettes and reduction of the de‐epoxidation state of the xanthophyll cycle pigments. No significant ozone effect was found for the investigated gas exchange and most biochemical parameters. The total and oxidized glutathione level of the leaves was increased by the 2 × O3treatment in the cuvette and the free‐air branches, but this effect was significant only for the free‐air branches. From these results we conclude that cuvette branches are useful surrogates for examining the response of entire tree crowns to elevated O3and that the defence metabolism of twigs seems to be at least partially autonomous.
Balloon Measurements of the Cosmic Microwave Background Strongly Favor a Flat Cosmos
Authors: Schwarzschild Bertram
Published: March 2007

In 1998 two related but independent groups sent balloon-borne microwave telescopes aloft to study fluctuations in the cosmic microwave background (CMB) at fine angular resolution. In August of that year, the Maxima telescope spent one night at 40 km above Texas. And at the end of the year, its “sister” telescope, called Boomerang, took advantage of the steady circumpolar winds of the austral summer to complete a 10-day stratospheric circumnavigation of Antarctica.
A Historical Perspective on Copenhagen
Authors: Cassidy David C.
Published: March 2007

Copenhagen, a thought-provoking drama by Michael Frayn that has played to sold-out audiences in London, has now opened in New York with much well-deserved attention. Despite the sparse set, the three-person cast, and the technical nature of the subject matter, this play appears to speak on some level to almost everyone. (See PHYSICS TODAY, May, page 51.)
The German Uranium Project
Authors: Bethe Hans A.
Published: March 2007

During World War II, the German atomic scientists were trying to produce electric power by creating a chain reaction in uranium. Werner Heisenberg hoped that this achievement would impress the allies if the war was lost.
Femtosecond Comb Technique Vastly Simplifies Optical Frequency Measurements
Authors: Lubkin Gloria B.
Published: March 2007

A recent measurement of the transition frequency between the 1S and 2S states of hydrogen has now reached a precision of 1.8 parts in 1014. As the precision of optical spectroscopy has developed, further improvements appear to be getting easier instead of harder. So says Theodor Hänsch, of the Max Planck Institute of Quantum Optics in Garching, Germany (near Munich), who has been a leader in the field since the 1970s. At that time, hydrogen spectroscopy could be done at the level of 1 part in 107 or 108. But Hänsch dreamt that eventually one would be able to reach a level of 1 part in 1018 by splitting the natural linewidth for the 1S-2S resonance (which is 5 parts in 1016) to about 1%. Now he's within four orders of magnitude of his dream. The new hydrogen measurement was done jointly by Hänsch and his collaborators in Munich, and by Christoph Salomon and his collaborators at the Paris Observatory.
Spin and Isospin: Exotic Order in Quantum Hall Ferromagnets
Authors: Girvin Steven M.
Published: March 2007

Quantum mechanics is a strange business, and the quantum physics of strongly correlated many-electron systems can be stranger still. Good examples are the various quantum Hall effects. They are among the most remarkable many-body quantum phenomena discovered in the second half of the 20th century, comparable in intellectual import to superconductivity and superfluidity. The quantum Hall effects are an extremely rich set of phenomena with deep and truly fundamental theoretical implications.
QCD Made Simple
Authors: Wilczek Frank
Published: March 2007

Quantum chromodynamics, familiarly called QCD, is the modern theory of the strong interaction. Historically its roots are in nuclear physics and the description of ordinary matter—understanding what protons and neutrons are and how they interact. Nowadays QCD is used to describe most of what goes on at high-energy accelerators.
Diffusion Waves and their Uses
Authors: Mandelis Andreas
Published: March 2007

The concept of waves is an integral part of our scientific culture and has nourished physicists, pure and applied alike, for centuries. Many important discoveries in physics, including quantum mechanics, have involved wave phenomena. The wave concept owes some of its scientific success to its mathematical tractability. Linear wave equations—the sort that describe the transmission of sound and radio waves through air—contain a nonzero second-order time derivative, which gives rise mathematically to the rich and familiar array of properties we associate with waves, such as wavefront propagation, reflection, and refraction.
Szilard as Inventor: Accelerators and More
Authors: Telegdi Valentine L.
Published: March 2007

It is little appreciated, even in William Lanouette's excellent biography, that Leo Szilard worked as a professional inventor during most of his scientific career, constantly filing patent applications that covered an astonishingly large range of novel ideas.
Blue Diode Lasers
Authors: Johnson Noble M. , Nurmikko Arto V. , DenBaars Steven P.
Published: March 2007

The recent achievement of compact blue-emitting gallium nitride semiconductor lasers is likely to have far-reaching technological and commercial effects. The lasers' short wavelengths—around 400 nm, half that of gallium arsenide-based lasers—permit higher spatial resolution in applications such as optical storage and printing. And the high photon energy will open up new applications for these inexpensive, compact light sources. An aesthetic satisfaction with these devices stems from finally extending the existing and mature semiconductor laser technology for the near-infrared and red to encompass the “new frontier” blue and near-ultraviolet regions, thereby bridging the entire visible spectrum. At the same time, there are significant research opportunities arising from a plethora of poorly understood microscopic issues in the underlying material system, which include such fundamental properties as charge control, transport, and formation of optical gain for stimulated emission.
Organic Material Debuts as Both an Injection Laser and a Superconductor
Authors: Levi Barbara Goss
Published: March 2007

It's rare that a conference talk will sweep an audience off its feet, but those who heard Bertram Batlogg of Bell Labs address the International Conference on Synthetic Metals (ICSM) in Bad Gastein, Austria, this past July were reportedly blown away by what he had to say. Batlogg's group had achieved the long-sought goal of making an electrically pumped injection laser from an organic material, specifically tetracene. Furthermore, the team had also shown that the same tetracene crystals could be made to superconduct, with a critical temperature of a few degrees kelvin. But perhaps the most intriguing aspect of both demonstrations was the elegant and novel technique that the Bell Labs team had devised for adding charge: Rather than chemically doping their crystal, the experimenters injected charge through a field-effect-transistor arrangement, adding enough charge to convert the normally insulating tetracene crystal into a metal and even a superconductor. The control exerted by these experimenters over the current density allows them to study different regimes of behavior, as they did recently in exploring the fractional quantum Hall effect in tetracene and pentacene.

The following news story reports on work that has since been discredited. An independent committee commissioned by Bell Laboratories, Lucent Technologies, found evidence of scientific misconduct in the papers on which it was based (see Physics Today, November 2002, page 15 http://dx.doi.org/10.1063/1.1534995). The authors have withdrawn the papers in questions.
Pulse Shaping Improves Efficiency of Soft X-Ray Harmonic Generation
Authors: Fitzgerald Richard
Published: March 2007

As physicists seek to probe and control phenomena on increasingly smaller length scales, coherent sources of radiation in the extreme ultraviolet (EUV or XUV, 10–100 nm) and soft x-ray (1-30 nm) regions of the spectrum are increasingly in demand. The semiconductor industry, for example, is eagerly pursuing EUV sources that can generate smaller linewidths beyond the limits of optical lithography. And femtosecond chemistry could benefit from light sources capable of producing very short pulses at small wavelengths.
Technologies to Reduce Carbon Dioxide Emissions in the Next Decade
Authors: Rosenfeld Arthur H. , Kaarsberg Tina M. , Romm Joseph
Published: March 2007

The rise in the average global temperatures over the past few decades has raised concerns that the warming stems in part from anthropogenic emissions of so-called greenhouse gases, that is, those gases that trap heat near Earth's surface. Dominant among the greenhouse gases caused by human activity is carbon dioxide, even when the gases are compared in terms of their perturbation to the atmosphere, as in figure 1. CO2 is a natural component of the atmosphere, but its concentration has increased by one-third since the start of the industrial era and continues to rise at about 0.4% per year.
Nobel Prize in Chemistry Salutes the Discovery of Conducting Polymers
Authors: Levi Barbara Goss
Published: March 2007

In 1976, a serendipitous chain of events brought together three individuals from different academic and geographical cultures to study a curious polymer: polyacetylene. The trio soon discovered that doping this polymer can change its behavior from insulating to metallic. For that work, the three—Alan Heeger, a physicist now at the University of California, Santa Barbara; Alan MacDiarmid, a chemist from the University of Pennsylvania then specializing in inorganic chemistry; and Hideki Shirakawa, a polymer chemist who has recently retired from Japan's Tsukuba University—have now earned the 2000 Nobel Prize in Chemistry “for the discovery and development of conductive polymers.”
The Scientific Community and Intelligence Collection
Authors: Moynihan Mark F.
Published: March 2007

Jim Woolsey's statement before the US Senate presaged a dramatic shift in the way the US intelligence community collects intelligence. Before the end of the cold war, intelligence personnel almost exclusively focused on only one target: the Soviet Union. Now, however, they must pursue that bewildering variety of poisonous snakes. And quite a challenge it is. From understanding the intentions of foreign leaders, such as Saddam Hussein, to detecting modern threats, such as those posed by bacteriological and chemical warfare, the challenges faced by the intelligence community push it to the very limits of its capabilities and expertise.
Enthusiasm Deepens for US Underground Physics Lab
Authors: Feder Toni
Published: March 2007

A cross section of physicists has revived efforts to build a Gran Sassostyle underground facility in the US.
Science with Soft X Rays
Authors: Smith Neville
Published: March 2007

Synchrotron radiation with photon energies at or below 1 keV is giving new insights into such areas as wet cell biology, condensed matter physics and extreme ultraviolet optics technology.
The Intriguing Superconductivity of Strontium Ruthenate
Authors: Maeno Yoshiteru , Rice T. Maurice , Sigrist Manfred
Published: March 2007

Structurally, this metal oxide resembles the high-Tc cuprates, but its superconductivity is more like the superfluidity of helium-3.
Ultrafast X-ray Diffraction Tracks Molecular Shape-Shifting
Authors: Day Charles
Published: March 2007

The molecular workings of photosynthesis, vision, and other light-driven processes can now be studied on the time scales on which they occur.
Electron Holography Lab Pushes Resolution Limit
Authors: Feder Toni
Published: March 2007

By minimizing electromagnetic, mechanical, and other disturbances, physicists in Dresden, Germany, aim to perfect electron holography and popularize its use in semiconductor, superconductor, and other materials studies.
Adjusting the Values of the Fundamental Constants
Authors: Mohr Peter J. , Taylor Barry N.
Published: March 2007

The best values of the fundamental constants can rarely be determined by a direct measurement. Instead, they are usually found at the end of a chain of experimental observations and theoretical relationships.
Time Measurement at the Millennium
Authors: Bergquist James C. , Jefferts Steven R. , Wineland David J.
Published: March 2007

The latest clocks use a single ion to measure time with an anticipated precision of one part in 1018.
New Conventional Superconductor Found with a Surprisingly High Tc
Authors: Day Charles
Published: March 2007

Magnesium diboride, a black powdery material you can buy off the shelf for less than $2 a gram, turns out to be a superconductor.
X-ray and γ-ray Holography Improve Views of Atoms in Solids
Authors: Fitzgerald Richard
Published: March 2007

New developments make possible the imaging of light atoms and the removal of image distortions.
Position Paper Ponders Planning for US High-Energy Physics
Authors: Schwarzschild Bertram
Published: March 2007

A new HEPAP White Paper urges adequate utilization of existing facilities and timely planning for new ones.
Preparing Physicists for Life’s Work
Authors: Ripin Barrett
Published: March 2007

Physics departments are exploring ways to turn out students well matched to today’s—and tomorrow’s—job opportunities.
Helium joins family of gaseous bose-einstein condensates
Authors: Fitzgerald Richard
Published: March 2007

Now that researchers have observed the condensation of a gas of helium in its metastable state, helium is the first atom to form a Bose condensate in two phases.
Dramatic Evidence Seen for Collective Behavior among Electrons in Closely Separated Layers
Authors: Levi Barbara Goss
Published: March 2007

Theorists describe the two-layer system as a Josephson junction, an exciton condensate, or a ferromagnet.
Dropout Rate among Chinese Physics PhD Students Seems High; Community Considers Why
Authors: Hargreaves Lynley
Published: March 2007

US physics departments are starting to take measures to select students who are more dedicated to staying in physics.
Layered Magnetic Structures: History, Highlights, Applications
Authors: Grünberg Peter
Published: March 2007

Once studied primarily for their effects on light, thin magnetic films are today being layered to make complex structures with unique magnetic properties. Devices based on these structures are revolutionizing electronic data storage.
Epitaxially Self-Assembled Quantum Dots
Authors: Petroff Pierre M. , Lorke Axel , Imamoglu Atac
Published: March 2007

Nanometer-scale islands that form spontaneously on a semiconductor substrate have atomlike properties and potential applications in optical and optoelectronic devices, quantum computing, and information storage.
Farthest Supernova Strengthens Case for Accelerating Cosmic Expansion
Authors: Schwarzschild Bertram
Published: March 2007

A 10-billion-year-old stellar explosion, serendipitously recorded by the Hubble Space Telescope’s infrared camera, seems to show the cosmic expansion slowing down before it eventually sped up.
The Physics of Earthquakes
Authors: Kanamori Hiroo , Brodsky Emily E.
Published: March 2007

Seismologists have never directly observed rupture in Earth’s interior. Instead, they glean information from seismic waves, geodetic measurements, and numerical experiments.
Flexible Methods for Microfluidics
Authors: Whitesides George M. , Stroock Abraham D.
Published: March 2007

Devices for handling nanoliter quantities of fluids are creating new fabrication challenges and finding new applications in biology, chemistry, and materials science.
Feedback Tames Chaotic Surface Chemistry
Authors: Day Charles
Published: March 2007

With a single parameter as a tiller, surface scientists can steer a model catalyst away from chaos toward regimes of regular, repeating behavior.
Solid Acids Show Potential for Fuel Cell Electrolytes
Authors: Fitzgerald Richard
Published: March 2007

Solid acids can have high proton conductivities. Recent experiments demonstrate that they may be sufficiently stable to form the core of new, higher efficiency fuel cells.
Scrounging Old Equipment for New Experiments
Authors: Feder Toni
Published: March 2007

Word of mouth is the best bet for scrounging scientific equipment.
Atoms Hop between Islands of Regular Motion in a Sea of Chaos
Authors: Levi Barbara Goss
Published: March 2007

Collections of ultracold atoms a recontinuing to prove their worth as systems for studying the interface between quantum behavior and nonlinear dynamics.
Experiments Detail How Powerful Ultrashort Laser Pulses Propagate through Air
Authors: Day Charles
Published: March 2007

Thanks to self-focusing, laser pulses can be launched upward into clouds where they can be used to measure pollutants.
Spanish Physicists Hungry for Fresh Infusion of Jobs, Money
Authors: Feder Toni
Published: March 2007

Tighter ties between research and industry, money for basic science, and jobs, jobs, and more jobs are needed to continue strengthening physics in Spain.
A Phase Odyssey
Authors: Nugent Keith A. , Paganin David , Gureyev Tim E.
Published: March 2007

Phase measurement permeates modern science. New propagation-based alternatives to interferometry are providing increased opportunities for phase measurements using x rays, electrons, neutrons, and other waves.
Turbulent Heat Flow: Structures and Scaling
Authors: Kadanoff Leo P.
Published: March 2007

Geometrical structures and scaling behavior provide insights into the nature of convective turbulence and some risky generalizations about “complex systems.”
A Physicist with the Air Force in World War II
Authors: Green Alex E. S.
Published: March 2007

Plucked out of graduate school after Pearl Harbor, a young physicist designed specialized slide rules for military aircraft. Trying them out aboard B-29s in the war against Japan, he had some hair-raising adventures.
Second Material Found that Superconducts in a Ferromagnetic State
Authors: Day Charles
Published: March 2007

At first glance, ferromagnetism and superconductivity look incompatible, but that hasn’t turned out to be the case.
Russia Banks on Importing Nuclear Waste
Authors: Guinnessy Paul
Published: March 2007

Domestic and international opposition may scuttle the survival strategy of Russia’s nuclear industry.
New NIH Institute Seeks to Serve Physicists and Engineers in Medicine
Authors: Feder Toni
Published: March 2007

Now that medical imagers and bioengineers have succeeded in getting their own NIH institute, they have to fill its coffers and define its role both at NIH and in the wider scientific community.
Communication in a Disordered World
Authors: Simon Steven H. , Moustakas Aris L. , Stoytchev Marin , Safar Hugo
Published: March 2007

Rather than decreasing efficiency, scattering can actually increase the information transfer rate for cell phones and other wireless microwave communication devices. Mesoscopic physics helps explain how.
Two Revolutions in K-8 Science Education
Authors: Lopez Ramon E. , Schultz Ted
Published: March 2007

Today’s science education, which teaches all students to do science and think like scientists, has depended on the involvement of scientists and their societies. It must continue to do so.
Spectra of the Most Distant Quasars Elucidate the Reionization of the Cosmos
Authors: Schwarzschild Bertram
Published: March 2007

Half a million years after the Big Bang, almost all the hydrogen in the cosmos was neutral. When and how did it all get reionized?
Legislation to Revive OTA Focuses on Science Advice to Congress
Authors: Dawson Jim
Published: March 2007

In an era of tight budgets and shrinking programs, it will be difficult to reestablish the Office of Technology Assessment, once a small, highly regarded office that provided science advice to Congress.
Physics and Archaeology
Authors: Garrison Ervan G.
Published: March 2007

Physics-based techniques are yielding more accurate dates for our prehistoric ancestors, profoundly affecting our understanding of the past.
The Little Machines That are Making it Big
Authors: Bishop David , Gammel Peter , Giles C. Randy
Published: March 2007

Microelectromechanical systems are currently used in a variety of applications, including triggering airbags and measuring the Casimir force. In the future, they may revolutionize the way we think about machines.
Understanding Why Sound Waves Travel Faster along Earth’s Axis in the Inner Core
Authors: Levi Barbara Goss
Published: March 2007

New calculations of iron’s elasticity at the temperatures and pressures of Earth’s inner core show that the directional dependence of sound waves in the crystals is larger than expected.
Sprites, Elves, and Glow Discharge Tubes
Authors: Williams Earle R.
Published: March 2007

The venerable field of gaseous electronics underlies the understanding of a lightning-like phenomenon of spectacular extent, shape, and color.
Can Polymeric Carbon-60 Be Magnetic?
Authors: Levi Barbara Goss
Published: March 2007

If a recent experiment is confirmed, theorists will be challenged to explain the evidence for weak ferromagnetism in a compound made solely of carbon.
Edward Condon and the Cold War Politics of Loyalty
Authors: Wang Jessica
Published: March 2007

Early in the cold war, a noted scientist was relentlessly hounded by red-baiting congressmen. The lessons of the case remain no less relevant today.
The Promise and Challenge of Solid-State Lighting
Authors: Bergh Arpad , Craford George , Duggal Anil , Haitz Roland
Published: March 2007

In time, solid-state devices should provide inexpensive, environmentally friendly illumination that changes the way we think about using artificial light.
National Labs Focus on Tools against Terrorism in Wake of Airliner and Anthrax Attacks
Authors: Dawson Jim
Published: March 2007

A sophisticated array of devices to detect the potential weapons of terrorism—chemical and biological agents, radioactive material, and explosives—are being developed by scientists working long hours to try to prevent future attacks.
Ultrashort Laser Pulses Can Control X-Ray Switch
Authors: Fitzgerald Richard
Published: March 2007

The ability to direct pulses of x-ray synchrotron radiation using femtosecond lasers may open a new avenue for time-resolved x-ray studies.
Federal R&D Tops $103 Billion, but Physics Stays Flat
Authors: Dawson Jim
Published: March 2007

Four years of federal budget surpluses are giving way to deficit spending, thanks in large part to terrorists, war, and recession. As the unanticipated spending began late in the budget process, overall science appropriations increased significantly.
Annular Modes and Climate Prediction
Authors: Wallace John M. , Thompson David W. J.
Published: March 2007

Links between stratospheric wind patterns and ground-based climate offer hope of improved long-range weather forecasting and provide a possible explanation for some conspicuous climate trends of the past few decades.
Surface Acoustic Waves in Materials Science
Authors: Hess Peter
Published: March 2007

Laser-generated surface waves provide new tools for studying material properties, from linear elastic behavior to fracture.
Physics in Oil Exploration
Authors: Clark Brian , Kleinberg Robert
Published: March 2007

Petroleum engineers use a variety of physical techniques to find and exploit petroleum reservoirs in increasingly remote and complicated geological environments.
New Designs for the Nuclear Renaissance
Authors: Marcus Gail H. , Levin Alan E.
Published: March 2007

The next generation of nuclear power plants could help satisfy the world’s energy needs and support a hydrogen-based economy.
Hydrogen: The Fuel of the Future?
Authors: Ogden Joan M.
Published: March 2007

Available hydrogen technologies can dramatically reduce pollution and greenhouse gas emissions. But the switch to hydrogen fuel will require strong political will.
Slowly but Steadily, Fermilab Pushes the Upgraded Tevatron toward Its Design Goals
Authors: Levi Barbara Goss
Published: March 2007

The lab is confident that its revamped accelerator, although currently behind schedule, will produce proton–antiproton collisions at the promised rate.
Stellarator Fusion Gets a New Look
Authors: Feder Toni
Published: March 2007

Symmetry has rekindled interest in stellarators as a possible path to fusion energy.
Direct Measurement of the Sun’s Total Neutrino Output Confirms Flavor Metamorphosis
Authors: Schwarzschild Bertram
Published: March 2007

A kiloton of ultrapure heavy water lets a detector deep inside a Canadian mine record high-energy neutrinos from the Sun, regardless of flavor changes en route.
New Physics in Fusion Plasma Confinement
Authors: Hazeltine Richard D. , Prager Stewart C.
Published: March 2007

In the past two decades, the picture of fusion plasmas has changed. Once analogous to an obscure work of abstract art, it is now more like a landscape full of comprehensible features.
On the Road Again: Metal Foams Find Favor
Authors: Banhart John , Weaire Denis
Published: March 2007

Lightweight yet stiff, metal foams are experiencing a resurgence of interest for applications ranging from automobiles to dental implants.
European Space Science Stretches Lean Budget
Authors: Feder Toni
Published: March 2007

To save its science missions, ESA will follow a more rigid schedule and forge closer cooperation with national space agencies.
Sinks for Anthropogenic Carbon
Authors: Sarmiento Jorge L. , Gruber Nicolas
Published: March 2007

We have learned much about the workings of natural sinks like the oceans and terrestrial plants, but are just beginning to understand how their behavior might change as atmospheric CO2 concentrations rise.
Superconducting Magnets Above 20 Tesla
Authors: Van Sciver Steven W. , Marken Kenneth R.
Published: March 2007

Superconductors are key components of magnets that generate homogeneous, low-noise, and extremely stable high fields. Further increasing the strength of these fields will require meeting a number of technological challenges.
PCAST Advises Bush to Boost S&T Role in New Homeland Security Department
Authors: Dawson Jim
Published: March 2007

According to the President’s Council of Advisors on Science and Technology, sophisticated technology will be an important tool in preventing and responding to terrorist attacks, and the new homeland security department must have a strong, centralized science and technology office to meet the challenge.
Optical Studies of Single Quantum Dots
Authors: Gammon Daniel , Steel Duncan G.
Published: March 2007

Like atoms, quantum dots can be probed and manipulated with light. Unlike atoms, they can be customized.
The Unusual Thermodynamics of Microscopic Systems
Authors: Blau Steven K.
Published: March 2007

Theoretical distributions of work delivered to small objects have some surprising properties recently confirmed by experiment.
Radiation in the Treatment of Cancer
Authors: Boyer Arthur L. , Goitein Michael , Lomax Antony J. , Pedroni Eros S.
Published: March 2007

The art of cancer treatment is finding the right balance between tumor control and injury to normal tissues.
Physics in Crisis
Authors: Nagel Sidney
Published: March 2007

This opinion is appearing simultaneously in FermiNews and Physics Today.
Brownian Motors
Authors: Astumian R. Dean , Hänggi Peter
Published: March 2007

Thermal motion combined with input energy gives rise to a channeling of chance that can be used to exercise control over microscopic systems.
Time-Reversed Ultrasound Beats the Diffraction Limit
Authors: Day Charles
Published: March 2007

A new technique focuses time-reversed sound onto a spot more than an order of magnitude smaller than the sound’s wavelength.
Second CERN Group Produces Cold Atoms of Antihydrogen
Authors: Levi Barbara Goss
Published: March 2007

A new experiment, by CERN’s ATRAP collaboration, introduces a technique for determining the quantum state in which antihydrogen atoms are formed.
Mesoscopic Texture in Manganites
Authors: Mathur Neil , Littlewood Peter
Published: March 2007

From atom-scale stripes to micron-scale patches, manganites exhibit a wealth of fascinating phase-separated behavior.
Bubble Puzzles
Authors: Lohse Detlef
Published: March 2007

Bubbles are familiar from daily life and occupy an important role in physics, chemistry, medicine, and technology. Nevertheless, their behavior is often surprising and unexpected—and, in many cases, still not understood.
Magnesium Diboride: Better Late than Never
Authors: Canfield Paul C. , Crabtree George W.
Published: March 2007

With a superconducting transition temperature of 40 K and two superconducting gaps, MgB2 is full of surprises for both experimentalists and theorists.
Rosalind Franklin and the Double Helix
Authors: Elkin Lynne Osman
Published: March 2007

Although she made essential contributions toward elucidating the structure of DNA, Rosalind Franklin is known to many only as seen through the distorting lens of James Watson’s book, The Double Helix.
Low-Energy Electron Microscopy: Imaging Surface Dynamics
Authors: Phaneuf Raymond J. , Schmid Andreas K.
Published: March 2007

Flexibility and time resolution make LEEM a powerful tool for studying mesoscale phenomena—from surface diffusion to magnetization.
WMAP Spacecraft Maps the Entire Cosmic Microwave Sky With Unprecedented Precision
Authors: Schwarzschild Bertram
Published: March 2007

A year of full-sky observation by the newly rechristened Wilkinson Microwave Anisotropy Probe greatly strengthens the case for inflationary Big Bang cosmology.
Ultrashort Laser Pulses Beget Even Shorter Bursts in the Extreme Ultraviolet
Authors: Day Charles
Published: March 2007

The attophysics frontier is about to expand, thanks to the newly won ability to control the phase of amplified laser pulses.
Technical and Policy Issues of Counterterrorism—A Primer for Physicists
Authors: Davis Jay , Prosnitz Don
Published: March 2007

No longer threatened by a rival superpower, the US now faces the growing danger of clandestine terrorist groups. Effectively countering terrorists requires that physicists actively contribute to the nation’s defense.
Supernovae, Dark Energy, and the Accelerating Universe
Authors: Perlmutter Saul
Published: March 2007

Using very distant supernovae as standard candles, one can trace the history of cosmic expansion and try to find out what’s currently speeding it up.
Two-ion logic gates open the way to further advances in quantum computing
Authors: Levi Barbara Goss
Published: March 2007

Precisely controlled logic gates are key ingredients in quantum computers, which can easily outperform classical computers for some problems.
Experiments Investigate the Behavior of Pores in Artificial Vesicles
Authors: Day Charles
Published: March 2007

Twenty-first century experimental techniques combine with 19th century theory to explore how cell membranes behave when breached.