bluuebunny/crossref_metadata_2025 huggingface dataset:
The structural properties of magainin in water, TFE/water, and aqueous urea solutions: Molecular dynamics simulations
Authors: Mehrnejad Faramarz , Naderi‐Manesh Hossein , Ranjbar Bijan
Published: March 2007

Here, the MD simulations and comparative structural analysis of Magainin in water, TFE/water, and 2M, 4M, and BM urea solutions is reported. For MAG‐TFE/water and MAG‐2M urea the largely alpha helical conformation of the peptide is maintained throughout the 9‐ns simulation. While in water, 4M urea, and 8M urea, the helix length decreases and at the same time helix radius increases. This suggests a more destabilized magainin secondary structure. Our simulation data reveals that the stabilizing effect of TFE is induced by preferential accumulation of TFE molecules around the alpha helical peptide. These results indicate that an aqueous urea solution solvates the sutface of polypeptide chain more favorably than pure water. Urea molecules interact more favorably with nonpolar groups of the peptide in comparison with water, and the presence of urea improves the interactions of water molecules with the hydrophilic groups of the peptide. At 8M urea, there are more direct interactions between the urea and solute, and the helix is destabilized. At 2M urea, the interaction of urea molecules and nonpolar residues are weak, therefore, the presence of urea molecules decreases the interactions of water molecules with hydrophilic groups. Urea could not deteriorate the peptide secondary structure with time from an initial helix structure. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Proteochemometric modeling reveals the interaction site for Trp9 modified α‐MSH peptides in melanocortin receptors
Authors: Lapinsh Maris , Prusis Peteris , Petrovska Ramona , Uhlén Staffan , Mutule Ilze , Veiksina Santa , Wikberg Jarl E. S.
Published: March 2007

The interactions of α‐MSH peptides with melanocortin receptors (MCRs) were located by proteochemometric modeling. Nine α‐MSH peptide analogues were constructed by exchanging the Trp9 residue in the α‐MSH core with the natural or artificial amino acids Arg, Asp, Cys, Gly, Leu, Nal, d‐Nal, Pro, or d‐Trp. The nine peptides created, and α‐MSH itself, were evaluated for their interactions with the 4 wild‐type MC1,3–5Rs and 15 multichimeric MCRs, each of the latter being constructed from three sequence segments, each taken from a different wild‐type MC1,3–5R. The segments of the chimeric MCRs were selected according to the principles of statistical molecular design and were arranged so as to divide the receptors into five parts. By this approach, a set of 19 maximally diverse MC receptor proteins was obtained for which the interaction activity with the 10 peptides were measured by radioligand binding thus creating data for 190 ligand–protein pairs, which were subsequently analyzed by use of proteochemometric modeling. In proteochemometrics, the structural or physicochemical properties of both interaction partners, which represent the complementarity of the interacting entities, are used to create multivariate mathematical descriptions. (Here, physicochemical property descriptors of the receptors' and peptides' amino acids were used). A valid, highly predictive (Q2 = 0.74) and easily interpretable model was then obtained. The model was further validated by its ability to correctly predicting the affinity of α‐MSH for new point and cassette‐mutated MC4/MC1Rs, and it was then used to identify the receptor residues that are important for affording the high affinity and selectivity of α‐MSH for the MC1R. It was revealed that these residues are located in several quite distant parts of the receptors' transmembrane cavity and must therefore cause their influence at various stages of the dynamic ligand‐binding process, such as by affecting the conformation of the ligand at the vicinity of the receptor and taking part in the path of the ligand's entry into its binding pocket. Our study can be used as a template how to create high resolution proteochemometric models when there are a limited number of natural proteins and ligands available. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Non‐invasive predictors of survival in cardiac amyloidosis
Authors: Kristen Arnt V. , Perz Jolanta B. , Schonland Stefan O. , Hegenbart Ute , Schnabel Philipp A. , Kristen Joern H. , Goldschmidt Hartmut , Katus Hugo A. , Dengler Thomas J.
Published: March 2007

Background:

Patients with cardiac amyloidosis (CA) have increased mortality.

Aims:

Clinical, electrocardiographic, and echocardiographic parameters were assessed for risk‐stratification of CA.

Methods and results:

CA was confirmed by endomyocardial biopsy in 59 patients (54.8±1.2 years) with light‐chain (n = 43) or transthyretin amyloidosis (n = 16). Six patients without CA served as controls (NCA). Clinical symptoms, electrocardiographic, and echocardiographic parameters were analyzed for prognostic significance. Of the patients with light‐chain amyloidosis, 14 died and 2 underwent heart transplantation. 1‐/3‐year survival was 68%/63%. Survival depended on left ventricular function (LV‐EF), LV mass, radius/wall thickness, septum thickness, low voltage pattern (LVP), conduction delay, NYHA class, and stem cell transplantation. A multivariate model only contained LV‐EF and LVP; the beneficial effect of stem cell transplantation was cancelled out as this treatment was withheld in patients with highest cardiac risk. Survival was most limited if both risk factors occurred. Cardiac involvement in transthyretin amyloidosis showed better survival (2 deaths, 1‐/3‐year survival 91%/83%). Analysis of prognostic risk factor utility in all amyloid patients (light‐chain and transthyretin) again revealed LVP and LV‐EF, and aetiology of amyloidosis as independent survival parameters.

Conclusion:

Prognosis of CA is poor, but aetiology of amyloid, LVP, and LV‐EF allows identification of patients at highest risk of death, who may require individual treatment approaches (heart transplantation prior to causative therapy).
Otitis media with effusion: what parents want to know
Authors: Vlastos I M , Hajiioannou J , Houlakis M
Published: March 2007

Introduction:

Otitis media with effusion is a common condition of childhood. The development of an information leaflet for parents of children with the condition, and its impact on clinical management, have not previously been examined.

Patients and methods:

Eighteen doctors and 38 parents assessed the content of an information leaflet on otitis media with effusion, by applying two rounds of the modified Delphi technique. A qualitative assessment of content items was also performed.

Results:

From the 23-item list used in the first assessment round, four items had a low doctor–parent agreement and seven were excluded. Differences were also noticed in comments on the value of such leaflets, with parents being more positive about the value of leaflet distribution.

Conclusion:

During the consultation, doctors may not tell parents what they want to know, especially regarding daily care of their child. An information leaflet, developed using the Delphi technique, can help reduce this discrepancy and increase parents' satisfaction.
Aboriginal rights to cultural property in Canada
Authors: Bell CE , Paterson RK
Published: March 2007

This article explores the rights of Aboriginal peoples in Canada concerning movable Aboriginal cultural property. Although the Canadian constitution protects Aboriginal rights, the content of this protection has only recently begun to be explored by the Supreme Court of Canada in a series of important cases. This article sets out the existing Aboriginal rights regime in Canada and assesses its likely application to claims for the return of Aboriginal cultural property. Canadian governments have shown little interest in attempting to resolve questions concerning ownership and possession of Aboriginal cultural property, and there have been few instances of litigation. Over the last decade a number of Canadian museums have entered into voluntary agreements to return cultural objects to Aboriginal peoples' representatives. Those agreements have often involved ongoing partnerships between Aboriginal peoples and museums concerning such matters as museum management and exhibition curatorship. A recent development has been the resolution of specific repatriation requests as part of modern land claims agreements. The compromise represented by these negotiated solutions also characterizes the legal standards being developed to reconcile existing Aboriginal rights and the legitimate policy concerns of the wider Canadian society.
Population size and habitat associations of the Long-tailed Ground-roller Uratelornis chimaera
Authors: SEDDON NATHALIE , TOBIAS JOSEPH A.
Published: March 2007

The Long-tailed Ground-roller (Uratelornis chimaera) is a globally Vulnerable, restricted-range species of dry forests in south-west Madagascar. We studied a population in 1997–2000, finding that nest-building was relatively synchronous and that pairs preferentially nested next to open areas, such as driveable tracks. By searching for trackside nests and for footprints, we conducted surveys throughout the known range of the species. Total transect coverage was 153 km, along which we encountered a minimum of 28 breeding pairs. By dividing the transects into 41 randomly distributed survey strips, each 1.2 km in length and 200 m broad, we intensively sampled an area of 9.84 km2. Using transect data, we made a tentative estimate of 5.7 mature adults km−2, from which we estimated a global population of 21,092 individuals, based on our calculation from satellite imagery that 3,706 km2 of suitable habitat remained. By comparing habitat data at points with and without ground-rollers we found that, contrary to previous statements, they prefer lower stature or degraded habitats, and have no direct association with the endemic cactus-like tree Didierea madagascariensis. We used a novel census technique to provide the first quantitative data on population size, population density, breeding behaviour and ecology in the Long-tailed Ground-roller, or any member of the family Brachypteraciidae, information that is crucial to the design of effective conservation programmes.
Chromium Yeast Supplementation Improves Fasting Plasma Glucose and LDL-Cholesterol in Streptozotocin-Induced Diabetic Rats
Authors: Lai  , Chen  , Cheng
Published: March 2007

Chromium yeast supplementation has been studied for its ability to improve carbohydrate and lipid abnormalities. There have been some earlier literature-reported studies involving chromium supplementation amongst patients suffering diabetes, but the results would appear to be somewhat varied. Forty male Wistar rats (ten weeks old, 300 g in average body mass) were divided into one of four groups, namely (i) controls; (ii) controls treated with chromium yeast; (iii) diabetic controls; and (iv) diabetic rats treated with chromium yeast. In the present investigation, the effect of a four-week oral administration of chromium yeast (600 μg of Cr/kg body mass/day, by gavage) upon the glucose and lipid metabolism in streptozotocin (STZ)-induced diabetic rats was assessed. Supplemental Cr yeast decreased the fasting blood glucose amongst the STZ-diabetic rats. No significant difference was observed in plasma fructosamine levels of rats treated with chromium yeast compared to control rats. Supplemental Cr yeast did decrease the plasma low-density lipoprotein (LDL)-cholesterol level for the STZ-diabetic rats as compared to controls. We noted no significant effect of chromium supplementation upon plasma high-density lipoprotein (HDL)-cholesterol or triglycerides compared to controls. Treatment with chromium yeast significantly increased the blood and urine chromium levels for both the diabetic and normal rats compared to respective control groups. The results of these studies suggest that Cr yeast decreased the fasting blood glucose and LDL-cholesterol levels in STZ-induced diabetic rats. This raises the possibility that Cr yeast supplementation can be considered to improve carbohydrate and lipid metabolism amongst human patients featuring type 2 diabetes mellitus.
The 1979–2005 Greenland ice sheet melt extent from passive microwave data using an improved version of the melt retrieval XPGR algorithm
Authors: Fettweis X. , van Ypersele J.‐P. , Gallée H. , Lefebre F. , Lefebvre W.
Published: March 2007

Analysis of passive microwave satellite observations over the Greenland ice sheet reveals a significant increase in surface melt over the period 1979–2005. Since 1979, the total melt area was found to have increased by +1.22 × 107 km2. An improved version of the cross‐polarized gradient ratio (XPGR) technique is used to identify the melt from the brightness temperatures. The improvements in the melt retrieval XPGR algorithm as well as the surface melt acceleration are discussed with results from a coupled atmosphere‐snow regional climate model. From 1979 to 2005, the ablation period has been increasing everywhere over the melt zone except in the regions where the model simulates an increased summer snowfall. Indeed, more snowfall in summer decreases the liquid water content of the snowpack, raises the albedo and therefore reduces the melt. Finally, the observed melt acceleration over the Greenland ice sheet is highly correlated with both Greenland and global warming suggesting a continuing surface melt increase in the future.
Tree Internal Signalling and Defence Reactions under Ozone Exposure in Sun and Shade Leaves of European Beech (Fagus sylvatica L.) Trees
Authors: Jehnes S. , Betz G. , Bahnweg G. , Haberer K. , Sandermann H. , Rennenberg H.
Published: March 2007

Abstract: The influence of free‐air ozone (O3) fumigation on the levels of gene transcripts and compounds of defence and signalling were analysed in leaves of adult beech trees from the “Kranzberg Forest” research site in 2003 and 2004. This includes the precursor of the stress hormone ethylene, ACC (1‐aminocyclopropane‐1‐carboxylic acid), conjugated salicylic acid, lignin content as well as of the expression level of genes connected with oxidative stress and stress signalling. At this site mature beech trees were exposed to an enhanced O3 regime by a free‐air O3 canopy exposure system. Levels of conjugated ACC and conjugated salicylic acid in leaves were increased under O3 fumigation whereas lignin content was only slightly enhanced. Quantitative real‐time RT‐PCR (qRT‐PCR) was performed on transcripts of genes connected with lignin, salicylic acid, and ethylene formation, the shikimate pathway, abscisic acid biosynthesis as well as with the antioxidative system. Genes which showed O3‐dependent increases included FsCOMT (caffeic‐acid O‐methyltransferase) connected with lignin formation, the stress response genes FsACS2 (ACC synthase) and FsPR1 (PR10 ‐ pathogenesis‐related protein), as well as FsNCED1 (9‐cis‐epoxicarotenoid dioxygenase), the rate‐limiting enzyme of the ABA synthesis. For FsNCED1 expression level, a significant O3 effect was found with an 8‐fold (sun) and 7‐fold (shade) induction in July 2003 and a 3‐fold and 2.5‐fold induction in July 2004. While the observed effects were not continuous, elevated O3 is concluded to have the potential to disrupt the defence and signalling system.
Effects of Elevated Atmospheric CO2 and/or O3 on Intra‐ and Interspecific Competitive Ability of Aspen
Authors: Kubiske M. E. , Quinn V. S. , Marquardt P. E. , Karnosky D. F.
Published: March 2007

Abstract: Three model communities of trembling aspen (monoculture, and mixed with either paper birch or sugar maple) were grown for seven years in elevated atmospheric CO2 and O3 using Free Air CO2 Enrichment (FACE) technology. We utilized trends in species' importance, calculated as an index of volume growth and survival, as indications of shifting community composition. For the pure aspen communities, different clones emerged as having the highest change in relative importance values depending on the pollutant exposure. In the control and elevated CO2 treatments, clone 42E was rapidly becoming the most successful clone while under elevated O3, clone 8 L emerged as the dominant clone. In fact, growth of clone 8 L was greater in the elevated O3 treatment compared to controls. For the mixed aspen‐birch community, importance of aspen and birch changed by ‐ 16 % and + 62 %, respectively, in the controls. In the treatments, however, importance of aspen and birch changed by ‐ 27 % and + 87 %, respectively, in elevated O3, and by ‐ 10 % and + 45 %, respectively, in elevated CO2. Thus, the presence of elevated O3 hastened conversion of stands to paper birch, whereas the presence of elevated CO2 delayed it. Relative importance of aspen and maple changed by ‐ 2 % and + 3 %, respectively, after seven years in the control treatments. But in elevated O3, relative importance of aspen and maple changed by ‐ 2 % and + 5 %, respectively, and in elevated CO2 by + 9 and ‐ 20 %, respectively. Thus, elevated O3 slightly increases the rate of conversion of aspen stands to sugar maple, but maple is placed at a competitive disadvantage to aspen under elevated CO2.
Grain Boundary Doping May Improve High-Temperature Superconducting Wire
Authors: Fitzgerald Richard
Published: March 2007

Superconducting wire is a central part of many of the applications devised for high-temperature superconductors in the 15 years following their discovery. With transition temperatures Tc above the boiling temperature of liquid nitrogen (77 K), these superconductors have the potential to provide cheap, low-loss wires capable of carrying large currents. The technological realization of this potential has been difficult, however, due in part to the anisotropic character of the ceramic high-Tc materials. Although single crystals of high-Tc superconductors have high critical current densities—the figure of merit in wire applications—polycrystalline wires suffer from significantly reduced current-carrying ability.
DNA-Inspired Electrostatics
Authors: Gelbart William M. , Bruinsma Robijn F. , Pincus Philip A. , Parsegian V. Adrian
Published: March 2007

Under “physiological” conditions (a 0.1 molar solution of NaCl), a DNA molecule takes on the form of a disordered coil with a radius of gyration of several micrometers; if any lengths of the molecule come within 1 nm of one other, they strongly repel. But under different conditions—in a highly dilute aqueous solution that also contains a small concentration of polyvalent cations—the same DNA molecule condenses into a tightly packed, circumferentially wound torus. Figure 1a shows just such a DNA torus. Its average radius is about 50 nm, and the distance between the axes of neighboring, parallel portions of the molecule is only slightly larger than its diameter.
New Measurements of Hydroxyl in the Middle Atmosphere Confound Chemical Models
Authors: Day Charles
Published: March 2007

The drive to measure, understand, and prevent ozone depletion over Antarctica has been so intense and attention-grabbing that the words “ozone” and “hole” now seem mated for life. But the ozone layer, which is densest at altitudes of 15–20 km, envelops the entire planet and extends into the mesosphere, where it plays a key role in the atmosphere's physics and chemistry. Ozone molecules, heated by their absorption of ultraviolet photons from the Sun, provide most of the energy that drives circulation in the upper stratosphere and mesosphere. (Figure 1 depicts the vertical structure of the atmosphere.)
Binary Quasicrystals Discovered That Are Stable and Icosahedral
Authors: Day Charles
Published: March 2007

You don’t need three chemical elements to make thermodynamically stable quasicrystals. Two will do.
So You Want to Be a Professor!
Authors: Anderson Matt
Published: March 2007

You’ve finished your PhD. You’re almost done with your postdoc. Now what? If you aim to stay in academia, read on.
Europe Moves toward Coherent Higher Education, Competes for Students
Authors: Feder Toni
Published: March 2007

In the debates on how to reform Europe’s higher education systems, the aims are faster, internationally recognized degrees that will be accepted by employers, increased flexibility of study programs, and global competitiveness.
Nations Tackle Nuclear Terrorist Threat
Authors: Guinnessy Paul
Published: March 2007

Lax controls on nuclear materials and a thriving black market are alarming officials.
Time-Resolved Macromolecular Crystallography
Authors: Galburt Eric A. , Stoddard Barry L.
Published: March 2007

Rapid x-ray characterization of structure and innovative ways of initiating and controlling reactions are shedding new light on protein function by enabling the visualization of macromolecules in action.
The Nobel Laureate Versus the Graduate Student
Authors: McDonald Donald G.
Published: March 2007

John Bardeen, the leading condensed matter theorist of his day, was quite wrong when he dismissed a startling prediction by the unknown Brian Josephson.
X-Ray Observations of Young Stars Address a Puzzle of the Solar System’s Origin
Authors: Schwarzschild Bertram
Published: March 2007

Must we really invoke a supernova midwife to explain why the newborn Solar System harbored so much short-lived radioactivity? Maybe not.
Isotopic Analysis of Pristine Microshells Resolves a Troubling Paradox of Paleoclimatology
Authors: Schwarzschild Bertram
Published: March 2007

If fossil isotopic data tell us that the tropical ocean was much cooler 50 million years ago than it is now, then either the data are flawed or we understand very little about global warming.
A Personal Reflection on University Research Funding
Authors: Birnbaum Howard K.
Published: March 2007

A veteran researcher in materials science and engineering argues that research funding needs reform at both the university and funding-agency levels.
Bonanza for Selected Science in Ireland
Authors: Feder Toni
Published: March 2007

Ireland’s new NSF-inspired funding agency has more money than scientists had dared hope for.
Nuclear Magnetic Resonance Spotlights Atomic Actors in Enzyme Dynamics
Authors: Day Charles
Published: March 2007

For years, biologists have used NMR to determine molecular structures. Now they’re using it to see how those structures change shape.
Advanced Physics in the High Schools
Authors: Gollub Jerry P. , Spital Robin
Published: March 2007

A study by the National Research Council makes several recommendations for improving the Advanced Placement program in the US.
Enrico Fermi and Quantum Electrodynamics, 1929–32
Authors: Schweber Silvan S.
Published: March 2007

A review article that Fermi wrote in 1932 taught an entire generation of physicists how to think about quantum electrodynamic effects in atomic phenomena.
An Excursion with Enrico Fermi, 14 July 1954
Authors: Glauber Roy
Published: March 2007

Rising above it all in the French Alps, four colleagues had an adventurous afternoon.
Researchers Combine Carbon Nanotubes with MEMS Technology to Make a Tiny Triode
Authors: Day Charles
Published: March 2007

Miniature on-chip vacuum tubes could power efficient wireless communication devices.
New Criteria for Determining Interagency R&D Budgets
Authors: Dawson Jim
Published: March 2007

Since the early days of the Bush administration, OMB officials have warned that tighter rules for funding interagency R&D programs were on the way. The rules have arrived, and they cover applied and basic research.
Probing the Nanomechanics of Cartilage with Atomic Force Microscopy
Authors: Day Charles
Published: March 2007

Researchers have measured the intermolecular forces that help cushion our joints.
European Commission Prods EU to Unify Research Base
Authors: Feder Toni
Published: March 2007

Europe’s physicists wait with a mix of optimism and skepticism to see how FP6 will affect their science.
CERN Group Detects More than 100 Antihydrogens
Authors: Levi Barbara Goss
Published: March 2007

The mating of a positron to an antiproton is a significant milestone along an arduous path toward a comparison of matter with antimatter.
Fusion Energy Panel Urges US to Rejoin ITER
Authors: Dawson Jim
Published: March 2007

A burning plasma is within reach and fusion could start providing electricity in as little as 35 years, according to several fusion researchers.
Chemistry Nobel Laureates Helped Develop Tools to Study Large Biological Molecules
Authors: Levi Barbar Goss
Published: March 2007

This year’s recipients helped adapt mass spectroscopy and nuclear magnetic resonance to the study of proteins.
Intergalactic Magnetic Fields
Authors: Kronberg Philipp P.
Published: March 2007

Magnetic fields that spread far beyond the galaxies that created them represent a significant, and only recently revealed, component of the cosmic energy budget.
Planetary Astronomers Worry About Future Funding
Authors: Feder Toni
Published: March 2007

Will plugging for the Large Synoptic Survey Telescope end up hurting support for ground-based planetary astronomy?
Infrared Adaptive Optics Reveals Stars Orbiting Within Light-Hours of the Milky Way’s Center
Authors: Schwarzschild Bertram
Published: March 2007

Orbital periods as short as 15 years clinch the case for a supermassive black hole at the Galaxy’s heart.
Kick-Starting Developing Economies With Relevant Technologies
Authors: Feder Toni
Published: March 2007

Martin Fisher puts his mind to using technology to facilitate microentre-preneurs in East Africa.
NSF Nears Decision on Underground Lab Site
Authors: Dawson Jim
Published: March 2007

As a Canadian mining company appears determined to shut off the pumps that keep South Dakota’s Homestake mine from flooding, the threat of high water is pressuring NSF to choose among three possible underground labs.
Watching a Molecule Break Up Reveals How Quickly It Changes Shape
Authors: Day Charles
Published: March 2007

It takes less than 60 femtoseconds for a doubly charged acetylene ion to change into its structural isomer vinylidene.
Astronomy Foes Join Forces to Build Giant Telescope
Authors: Feder Toni
Published: March 2007

A new public–private partnership faces hurdles but promises to make the US a formidable international competitor in ground-based astronomy.
Quantum Physics Under Control
Authors: Walmsley Ian , Rabitz Herschel
Published: March 2007

Thanks to the increasing ability to coherently control quantum systems, designer Hamiltonians can be created to explore new physics and to yield a better understanding of complex phenomena.
Submillimeter Measurements Strengthen the Case for Supernovae as Sources of Ancient Cosmic Dust
Authors: Blau Steven K.
Published: March 2007

Observations of high-redshift galaxies offered a surprise six years ago and presented a riddle that may have been solved only this past summer.
What Have We Learned From the Relativistic Heavy Ion Collider?
Authors: Ludlam Thomas , McLerran Larry
Published: March 2007

Collisions between high-energy beams of gold nuclei are providing glimpses of hot, dense states of matter reminiscent of the Big Bang.
Mercury Telescope Spins Up
Authors: Feder Toni
Published: March 2007

Pending solid science from the new Large Zenith Telescope, a group of scientists hopes to build an extremely large—and extremely cheap—array of liquid mercury telescopes.
Baja Site Vies to Host Telescopes
Authors: Feder Toni
Published: March 2007

The jury is still out on San Pedro Mártir’s becoming a major ground-based astronomy site, but it’s in the running thanks to its clear skies, proximity to the US, and other scientific and political virtues.
Ferroelectrets: Soft Electroactive Foams for Transducers
Authors: Bauer Siegfried , Gerhard-Multhaupt Reimund , Sessler Gerhard M.
Published: March 2007

After certain cellular polymers are internally charged, they behave like soft and sensitive piezoelectrics that can be used to interconvert acoustical or mechanical signals and electrical signals.
Hubble Sacrificed in Wake of President Bush’s New Space Vision
Authors: Guinnessy Paul
Published: March 2007

The Hubble Space Telescope has been sentenced to a slow death as NASA worries about minimizing risks to astronauts, completing the space station, and sending people to Mars. Astronomers are fighting a last-ditch campaign to reverse NASA’s HST decision.
Evidence Reported for a ‘Supersolid’ Phase of Helium-4
Authors: Levi Barbara Goss
Published: March 2007

The most likely explanation for a sharp drop in rotational inertia in crystalline 4He is the onset of superfluid behavior.
Dubna–Livermore Collaboration Forms Two New Superheavy Elements
Authors: Day Charles
Published: March 2007

The latest additions to the periodic table are element 115 and its daughter, element 113.
US Government Backs Off From Imposing Restrictions on Publishers
Authors: Feder Toni
Published: March 2007

In permitting one scholarly publisher’s activities, the Treasury Department seems to have muddied the dispute over freedom of the press and, in addition, has warned against collaborations between US scientists and their colleagues in sanctioned countries
Cryogenics on a Chip
Authors: Pekola Jukka , Schoelkopf Robert , Ullom Joel
Published: March 2007

Low-temperature techniques often bring to mind cryogenic liquids, gas compressors, and massive installations. But researchers are now building refrigerators and sensors that work by controlling electrons on a silicon chip
Edward Teller in the Public Arena
Authors: Brown Harold , May Michael
Published: March 2007

Having lived through upheavals in Hungary and Germany between the wars, Teller understood that political and military catastrophes are entirely possible. He was, perhaps, less aware that catastrophe can result from excess as well as inaction.
Court Rules Against 10 000-Year Radiation Safety Standard at Yucca Mountain
Authors: Dawson Jim
Published: March 2007

Saying the Environmental Protection Agency “unabashedly” ignored a National Academy of Sciences report on future radiation levels at the facility, a US appeals court sends the radioactive waste problem back to Congress.
I. I. Rabi and the Birth of CERN
Authors: Krige John
Published: March 2007

CERN was created in part to help restore a great European scientific tradition. But the establishment of a European laboratory also advanced US scientific and foreign policy aims.
Attosecond Bursts Trace the Electric Field of Optical Laser Pulses
Authors: Day Charles
Published: March 2007

The familiar textbook sketch of light’s oscillating electric field can now be drawn directly from measurements.
R-Process Nucleosynthesis in Supernovae
Authors: Cowan John J. , Thielemann Friedrich-Karl
Published: March 2007

The heaviest elements are made only in cataclysmic events. Finding out whether supernovae are cataclysmic enough requires extensive astronomical observation and sophisticated computer modeling.
Building a Cyclotron on a Shoestring
Authors: Feder Toni
Published: March 2007

Starting when he was an undergrad, Tim Koeth built a 12-inch cyclotron. Now he is in grad school and his creation is used in a senior-level lab class.
Trust and the Future of Research
Authors: Whitbeck Caroline
Published: March 2007

For many years, physicists were in denial that unethical conduct was a problem in their profession. But an erosion or neglect of trust and professional responsibility can threaten the research enterprise, often in subtle ways.
How to Popularize Physics
Authors: Simmons Elizabeth H.
Published: March 2007

An outreach effort can combine an eager audience, a favorite topic, and a preferred medium of expression to achieve a wonderful teaching experience.
Quantum Error Correction Demonstrated with Trapped Ions
Authors: Fitzgerald Richard
Published: March 2007

For the first time, this necessary part of a quantum computation scheme is implemented in a system that can be scaled up.
National Academies Committee Sets Steps for Bringing Best Science Advice to Washington
Authors: Dawson Jim
Published: March 2007

The president’s science adviser needs higher status, and candidates for science advisory boards should not be asked their political party or who they voted for, the National Academy of Sciences says in a new report.
Undergraduates Assemble Neutron Detector
Authors: Feder Toni
Published: March 2007

Spreading the construction of a detector across several institutions brings project visibility to participants.
Crushing a Solution of Left-Handed and Right-Handed Crystals Breaks Its Chiral Symmetry
Authors: Day Charles
Published: March 2007

A simple tabletop experiment could have profound implications for the origin of life.
The Accelerating Expansion of the Universe
Authors: Updike John
Published: March 2007

It is not true that developments in physics go ignored by professional humanists or by the common man. The basic facts get to us all and frame the way we think and even, in this instance of the fictional Martin Fairweather, feel. The picture physics paints of the material universe is arresting enough to make the newspapers but far from flattering to our individual identities. Astronomy is what we have now instead of theology. The terrors are less, but the comforts are nil. John Updike
Record Gamma-Ray Flare Is Attributed to a Hypermagnetized Neutron Star in Our Galaxy
Authors: Schwarzschild Bertram
Published: March 2007

Magnetars are neutron stars with the strongest magnetic fields known in nature or the laboratory. A problematic subclass of gamma-ray bursters may turn out to be extragalactic magnetars in disguise.
The Second Law of Thermodynamics
Authors: Lightman Alan
Published: March 2007

An original short story for Physics today
Creationist Wave Hits Volcanoes of the Deep Sea
Authors: Dawson Jim
Published: March 2007

With science museums finding an increasingly important source of revenue in their IMAX theaters, some museums are yielding to anti-evolution sentiment and not showing controversial films.
Ups and Downs of Nuclear Isomers
Authors: Walker Philip M. , Carroll James J.
Published: March 2007

Isomers are set apart from other nuclear excitations by their long half-lives. That longevity facilitates the study of nuclear structure and astrophysics, and it suggests a variety of practical applications.
Two-Dimensional Optical Spectroscopy Identifies Crucial Intermolecular Couplings in Photosynthesis
Authors: Day Charles
Published: March 2007

Protein-bound chlorophyll molecules transmit electronic excitation energy with almost no loss. A new optical technique shows how they do it.
Single, Physics-Based Model Accounts for the Mechanical Properties of Diverse Diopolymer Gels
Authors: Day Charles
Published: March 2007

Despite their variety of composition, stiffness, and strength, the protein-based filaments that support and connect cells behave in the same, predictable way when strained.
Is Economics the Next Physical Science?
Authors: Farmer J. Doyne , Shubik Martin , Smith Eric
Published: March 2007

An emerging body of work by physicists addressing questions of economic organization and function suggests new approaches to economics and a broadening of the scope of physics.
Targeted Ultrasound Mediates the Delivery of Therapeutic Genes to Heart Muscle
Authors: Day Charles
Published: March 2007

Rats exposed to ultrasound and injected with tiny DNA-coated bubbles grow new blood vessels.
Physicists Seek to Aid Developing Countries
Authors: Feder Toni
Published: March 2007

Conference delegates shaped ideas for how physics can contribute to sustainable development in the areas of education, economic development, energy and environment, and health.
Optical trap resolves the stepwise transfer of genetic information from DNA to RNA
Authors: Day Charles
Published: March 2007

The assembly of RNA can now be tracked with a precision finer than the distance between its bases.
Basic science funding flat, as war, deficit, and hurricane recovery squeeze federal budget
Authors: Dawson Jim
Published: March 2007

Most R&D agencies barely held their own in yet another year of modest science funding. A proposed across-the-board 2% cut could push many science programs into the red.
Physics for all? A million and counting!
Authors: Hehn Jack , Neuschatz Michael
Published: March 2007

Fully one-third of recent high-school graduates have taken physics. Much of the increase comes from nontraditional courses geared toward students not headed for careers in science or technology.
Semiconductor quantum dots take first steps toward spin-based quantum computation
Authors: Day Charles
Published: March 2007

Using nanosecond voltage pulses, researchers can entangle and rotate spin qubits in a double quantum dot—on demand.
Fifty years of seeing atoms
Authors: Tsong Tien T.
Published: March 2007

Beyond imaging atoms, clusters, and defects on a surface, today’s microscopes can distinguish elements, monitor their diffusion and redistribution near the surface, and even create designer nanostructures and reactions.
Gravitational microlensing reveals the lightest exoplanet yet found
Authors: Schwarzschild Bertram
Published: March 2007

Earth-like planets halfway across the galaxy can disclose themselves by bending light from background stars.
Pulsed Neutron Scattering for the 21st Century
Authors: Mason Thomas E.
Published: March 2007

The large neutron fluxes produced in next-generation spallation facilities are likely to soon find expanded application in fields as diverse as biology, polymers, complex fluids, and geophysics.
Trend-spotting: Physics in 1931 and today
Authors: Weart Spencer
Published: March 2007

A lot has changed in the past 75 years. Can those changes help us guess where physics will be 75 years from now?
Science and government
Authors: Marburger John H.
Published: March 2007

Science policy depends on the state of science itself, which evolves in response to new instrumentation, theoretical methods, and analytical tools. The growth of science and the course of science policy are undeniably progressive.
Proposed export restrictions withdrawn
Authors: Dawson Jim
Published: March 2007

Hundreds of letters of protest from scientific, academic, and industrial organizations convinced Department of Commerce officials to reconsider a tightening of the deemed export policy.
Tiny oscillating circuit exhibits new quantization of electrical conductance
Authors: Day Charles
Published: March 2007

Remarkably, the conductance of a coherent RC circuit keeps the same quantized value even when the resistor is widened to let through more electrons.
Nuclear spin polarization induced solely by a rotating magnetic field
Authors: Goss Levi Barbara
Published: March 2007

The effect is so small that its experimental measurement had to await today’s sensitive detectors.
White dwarf is caught hurling its outer layers at its red giant companion
Authors: Day Charles
Published: March 2007

Observations of the 12 February outburst and its aftermath are helping astronomers understand novae and supernovae.
Inductive magnetization of low-temperature ordered L10-FePt with CoAg underlayer
Authors: Lai Yu-Cheng , Chang Yen-Hwei , Chen Yen-Chia , Liang Chih-hao , Chang Wen-Cheng , Chiou Chun-Mao , Chen Guo-Ju
Published: March 2007

The feasibility of controlling film microstructure and nanocomposition of FePt film with various compositions of the CoAg underlayer by ion beam sputtering accompanied by an external magnetic field was performed. The characteristic of phase separation of the CoAg underlayer was employed to induce an inductive magnetism region which reduced the annealing temperature acquired for L10-FePt. The segregation of Co atoms could influence the corresponding magnetic properties of FePt. After annealing at 400°C, the FePt∕CoAg films deposited under the magnetic field showed a larger coercivity (Hc=5kOe) than that of the film deposited without a magnetic field (Hc=0.4kOe).
Collision between galaxy clusters unveils striking evidence of dark matter
Authors: Schwarzschild Bertram
Published: March 2007

The nonbaryonic matter generally assumed to dominate large aggregates of stars and gas almost always shares a common center of mass with the ordinary matter we can see. But a titanic collision can force them apart.
Reactor experiments seek missing neutrino mixing angle
Authors: Feder Toni
Published: March 2007

Exposing the details of how electron neutrinos change flavor could be a step toward determining the neutrino mass hierarchy and explaining the imbalance of matter and antimatter in the universe.
Properties of nanostructured Ge produced by laser-induced air breakdown processing
Authors: Kabashin A. V. , Magny F. , Meunier M.
Published: March 2007

Germanium wafers have been modified by a technique of laser-induced air breakdown processing. It has been found that the treatment leads to the formation of porous layers, containing nanoscale holes, and consists of Ge nanocrystals embedded into GeO2 matrices. They exhibit strong and stable photoluminescence in the green and UV ranges (2.2 and 2.9eV), whose appearance could be explained by defects in the GeO2 matrix or quantum confinement effects. The locally patterned layers are of importance for optoelectronics and biosensing applications.
Spatially resolved modeling of the combined effect of dislocations and grain boundaries on minority carrier lifetime in multicrystalline silicon
Authors: Stokkan G. , Riepe S. , Lohne O. , Warta W.
Published: March 2007

A model for the combined effect of dislocations and grain boundaries on minority carrier lifetime has been developed. Lifetime varies with dislocation density, grain boundary misorientation, and the coincidence site lattice (CSL) nature of the boundaries. Minority carrier lifetime was measured with high spatial resolution (50 μm) using the carrier density imaging (CDI) technique on a silicon nitride passivated multicrystalline sample. Dislocation density was measured on the same sample by image recognition of optical microscope pictures of a Secco etched surface. Grain boundaries were then mapped and characterized by electron backscatter diffraction (EBSD). Lifetime was simulated based on the dislocation and grain boundary measurements. Parameters were chosen to match closely the simulated and measured maps. Very good two-dimensional (2D) correlation was obtained by assigning roughly equal importance to recombination at dislocations and grain boundaries. The value for the capture cross section, which gives the best correlation, is 4×10−14 cm−3. This is in the range of values reported for interstitial transition metals like, for instance, iron. It appears necessary to include also the effect of grain boundaries to explain recombination in low lifetime areas. Sub grain boundaries were particularly recombination active and are dominating the number of active grain boundaries.
Dissociation of Si+ ion implanted and as-grown thin SiO2 layers during annealing in ultra-pure neutral ambient by emanation of SiO
Authors: Beyer V. , von Borany J. , Heinig K.-H.
Published: March 2007

We have observed a very inhomogeneous dissociation of stoichiometric and non-stoichiometric thin SiO2 layers (thermally grown on Si substrates) during high temperature annealing at a low partial pressure of oxygen. During this process some silicon of the (100)Si substrate and, in case of Si ion implantation, and additionally, excess Si is consumed. The SiO2 dissociation has been studied by electron microscopy and Rutherford backscattering spectrometry. Large holes (>1 μm) in non-implanted oxide layers have been observed which evolve probably from defects located at the Si∕SiO2 interface. For Si implanted SiO2 additionally the formation of voids within the oxide during annealing has been observed preferably at the position of the implanted Si excess. Oxygen vacancies are possibly emitted from Si∕SiO2 interfaces into the oxide and migrate through SiO2 with long-range distortions of the oxide network. In that way the hole and void formation in the oxide can be explained by oxygen-vacancy formation, migration and silicon-monoxide (SiO) emanation. As a driving force for growth of the large holes we identified oxygen diffusion from the Si∕SiO2 interface to the bare Si surface. This surface is a sink of oxygen diffusion due to the emanation of volatile SiO, whereas the Si∕SiO2 interface serves as an oxygen source. The predicted mechanism is consistent with the geometry of the holes in the SiO2 layer.
Electrical analysis of positive corona discharge in air and N2, O2, and CO2 mixtures
Authors: Dubois D. , Merbahi N. , Eichwald O. , Yousfi M. , Benhenni M.
Published: March 2007

This paper presents an experimental analysis of the electrical behavior of positive point-plane corona discharges. The corona current, streamer velocity, mean discharge frequency, and current-voltage characteristic are studied, firstly in synthetic air as a function of experimental parameters such as gap distance and tip radius. Different electrical diagnostics are used in order to better understand the streamer development as well as the dependence of its characteristics on the previous listed parameters. Then the influence of gas mixture (several proportions of N2 and O2 with or without CO2) is analyzed. When the gas concentration is varied the shape and amplitude of the corona current are significantly affected due to the variation of the gas electronegativity following its composition and concentration. The ionization and attachment coefficients are calculated from the electron energy distribution function in the case of these different gas mixtures in order to quantify the critical electric field value enabling the streamer development for a given gas mixture.
Optical spectra and spin Hamiltonian parameters for rhombic Zr3+ in Y3Al5O12
Authors: Zheng Wen-Chen , Fang Wang , Mei Yang
Published: March 2007

The four optical spectrum bands (or d-d transitions) and six spin Hamiltonian parameters (g factors gx, gy, gz and hyperfine structure constants Ax, Ay, Az) of the rhombic Zr3+ (4d1) center in Y3Al5O12 crystal are calculated from the complete diagonalization (of energy matrix) method and the perturbation theory method. The calculated results from both methods are not only close to each other but also in good agreement with the experimental values. It appears that the two microscopic theory methods (which are very close to those used in a 3d1 system) are effective in the explanations of the optical and electron paramagnetic resonance spectra for a 4d1 system. From the calculations, the optical spectrum bands are reassigned and the defect structure of the rhombic Zr3+ center in Y3Al5O12 crystal is estimated.
High-temperature perovskite relaxor ferroelectrics: A comparative study
Authors: Stringer C. J. , Shrout T. R. , Randall C. A.
Published: March 2007

The recent discovery of high-temperature piezoelectric ceramics based on Bi(Me′Me″)O3-PbTiO3 solutions have also permitted the development of high-temperature relaxor ferroelectrics with ternary solid solutions. One of the high-temperature compositions based on the xBiScO3-yPb(Mg1∕3Nb2∕3)O3-zPbTiO3 (xBS-yPMT-zPT) ternary system exhibited a high permittivity maxima of ∼17 000 and a Tmax of 500–550 K. These materials are compared to complex lead perovskite relaxor ferroelectrics by determination of the activation energy, EA, and freezing temperature, Tf, from the Vögel-Fulcher relationship and also a high-temperature deviation temperature, TD, from the Curie-Weiss behavior. It was found that these parameters scale within the perovskite relaxor systems and from the self-consistent trends of these defining parameters. It is suggested that a general comparison for relaxor ferroelectrics may exist. The highest EA, Tf, and TD values all exist within the xBS-yPMT-zPT ternary system within the relaxor ferroelectric systems compared in this study. Furthermore, given the compositional trends within these comparisons, insights into the nature of the dynamic polarization behavior in the perovskite relaxor ferroelectrics may be gained.