bluuebunny/crossref_metadata_2025 huggingface dataset:
ECPR Fourth Biennial General Conference, September 6–8,
2007, University of Pisa, Italy
Authors: Bardi Luciano , Bull Martin , Dekker Clare , Hawkridge Louise
Published: January 2008

The Pisa conference was also the occasion for presenting three of the
ECPR's prizes. The first was the ECPR's Lifetime Achievement Award
for an outstanding contribution to European political science, which
went to an American: Philippe Schmitter (European University,
Florence, and formerly Stanford University). Second, the annual Jean
Blondel Ph.D. Prize was awarded to Tanja Aalberts (Leiden
University) for her dissertation on the politics of sovereignty.
Finally, the Mattei Dogan Foundation Prize in European Political
Sociology went to Giovanni Sartori (professor emeritus, University
of Florence and Columbia University).
Congressional Fellowship: A Voyage through Politics and
Policies in the United States
Authors: Kunduri Prasad V.
Published: January 2008

Fall of 2007 will remain etched in the memory of all my colleagues as
a period when each one of us, individually and collectively, turned
a new leaf in our lives. Over the past two weeks, the six of us
international fellows arrived separately in Washington, D.C., to
take part in the U.S. Congressional Fellowship program of the
American Political Science Association (APSA).
Allocating the Credit in Collaborative
Research
Authors: Biggs Jeffrey
Published: January 2008

For years journal articles from the natural sciences have been
characterized by multiple authors, reflecting the collaborative
nature of the research. The articles have also conformed to a
professional norm in giving credit to the authors and, at least
implicitly, indicating their relative contributions. Although such
collaborative research has grown significantly in political science,
the discipline is still wrestling with any standard to indicate who
gets credit and the nature of multiple authors' relative
contributions. This is an issue with which political scientists from
the most junior to the most senior continue to deal.
CARM1 promotes adipocyte differentiation by coactivating PPARγ
Authors: Yadav Neelu , Cheng Donghang , Richard Stephane , Morel Melanie , Iyer Vishwanath R , Aldaz C Marcelo , Bedford Mark T
Published: January 2008

The coactivator‐associated arginine methyltransferase 1 (CARM1) is recruited to gene promoters by many transcription factors. To identify new pathways that use CARM1, we carried out a comprehensive transcriptome analysis of CARM1‐knockout embryos. By using complementary DNA microarrays and serial analysis of gene expression, we identified various genes involved in lipid metabolism that were underrepresented in CARM1‐knockout embryos, indicating an important role for this coactivator in adipose tissue biology. We also observed that the amount of brown fat in CARM1‐knockout embryos is reduced. Furthermore, cells lacking CARM1 have a severely curtailed potential to differentiate into mature adipocytes. Reporter experiments and chromatin immunoprecipitation analysis show that CARM1 regulates these processes by acting as a coactivator for peroxisome proliferator‐activated receptor gamma (PPARγ). Together, these results show that CARM1 promotes adipocyte differentiation by coactivating PPARγ‐mediated transcription and thus might be important in energy balance.
Cell‐cycle‐dependent binding kinetics for the early endosomal tethering factor EEA1
Authors: Bergeland Trygve , Haugen Linda , Landsverk Ole J B , Stenmark Harald , Bakke Oddmund
Published: January 2008

Early endosomal antigen 1 (EEA1) is a cytosolic protein that specifically binds to early endosomal membranes where it has a crucial role in the tethering process leading to homotypic endosome fusion. Green fluorescent protein‐tagged EEA1 (EEA1‐GFP) was bound to the endosomal membrane throughout the cell cycle, and measurements using fluorescent recovery after photobleaching showed two fractions: one rapidly exchanging with the cytosolic pool, and the other with a long half‐life. The exchange consists of a release and binding process, and we have separated these two by using GFP and photoactivable GFP. The release rate was identical to the exchange rate, showing that the dissociation characteristics determine the cycling of this molecule. During mitosis, we found that the dissociation rate was markedly accelerated and, in addition, the long‐lived fraction was markedly reduced. This indicates that a fusion arrest in mitosis is not the result of EEA1 not binding to early endosomes, but rather due to the marked shift in membrane‐binding characteristics. This might be a general mechanism to fine‐tune and control tethering and fusion of early endosomes.
A selective PIKfyve inhibitor blocks PtdIns(3,5)P2 production and disrupts endomembrane transport and retroviral budding
Authors: Jefferies Harold B J , Cooke Frank T , Jat Parmjit , Boucheron Christine , Koizumi Tomonobu , Hayakawa Masahiko , Kaizawa Hiroyuki , Ohishi Takahide , Workman Paul , Waterfield Michael D , Parker Peter J
Published: January 2008

Phosphoinositides have crucial roles in cellular controls, many of which have been established through the use of small‐molecule inhibitors. Here, we describe YM201636, a potent inhibitor of the mammalian class III phosphatidylinositol phosphate kinase PIKfyve, which synthesizes phosphatidylinositol 3,5‐bisphosphate. Acute treatment of cells with YM201636 shows that the PIKfyve pathway is involved in the sorting of endosomal transport, with inhibition leading to the accumulation of a late endosomal compartment and blockade of retroviral exit. Inhibitor specificity is shown by the use of short interfering RNA against the target, as well as by rescue with the drug‐resistant yeast orthologue Fab1. We concluded that the phosphatidylinositol 3,5‐bisphosphate pathway is integral to endosome formation, determining morphology and cargo flux.
The Hunt for Anyons in Oxide Superconductors is Inconclusive
Authors: Levi Barbara Goss
Published: January 2008

As the date of the APS March meeting draws near, the conflicting results of two key experiments first aired by condensed matter physicists at last year's gathering are no closer to being resolved. Indeed a third experiment, reported this fall, has further clouded the picture. The conflicting evidence concerns whether or not high-temperature superconductors alter either the direction or ellipticity of polarized light passing through them. Such behavior might signal the breaking of time-reversal invariance in these new oxide materials—precisely the effect predicted by proponents of theories that invoke anyons, or exotic objects obeying fractional statistics, to explain the superconductivity.
Gamma Telescope Finds ‘Great Annihilator’ Near Galactic Center
Authors: Schwarzschild Bertram
Published: January 2008

For 20 years gamma-ray astronomers have been reporting intermittent evidence of positron-annihilation gammas coming from the vicinity of the center of our Galaxy. Much speculation about what's going on in the hidden heart of the Milky Way has been fueled by these sporadic sightings of 511-keV gammas. (When an electron–positron pair at rest annihilates into two photons, the result is a pair of back-to-back 511-keV gammas.) The most spectacular notion attributed the positrons to the workings of a monstrous black hole of some 106 solar masses, residing at the dynamical center of the Galaxy.
Four of Five New Experiments Claim Evidence For 17-keV Neutrinos
Authors: Schwarzschild Bertram
Published: January 2008

Six years ago, John Simpson at the University of Guelph in Ontario reported a rather disquieting discovery. In the beta decay of tritium, he asserted, a small fraction of decay events appear to produce a neutrino weighing 17 keV. That's 130, the mass of the electron—very much larger than anyone was looking for in the many attempts to find evidence for a nonvanishing neutrino mass in the end point of the electron energy spectrum from tritium decay.
Industry Gambles on Electron Synchrotrons for X-Ray Lithography
Authors: Levi Barbara Goss
Published: January 2008

Ultralarge-scale integrated circuits are patterned by optical lithography, which can now imprint linewidths narrower than 0.8 micron in commercial production. With some promising innovations, optical lithography may be able to push its limiting linewidths below 0.25 microns, narrow enough to produce the next two generations of circuits—16-Mbit and 64-Mbit dynamic random-access memory chips. To cram still more electronic features onto a given area, as is envisioned for the manufacture of chips with 256 Mbits or more, will probably require wavelengths typical of soft x rays rather than visible or ultraviolet light. Thus for nearly 20 years researchers have been developing the sources, masks, aligners, resists and other components of x-ray lithographic systems.
Light Comes from Ultrasonic Cavitation in Picosecond Pulses
Authors: Levi Barbara Goss
Published: January 2008

Many applications of ultrasound, such as welding plastics or sterilization of medical equipment, exploit cavitation, the rapid expansion and collapse of bubbles as sound waves pulse through a liquid. This phenomenon that has proved to be so utilitarian is also the source of great fascination and mystery: During cavitation the collapsing bubbles develop extremely high temperatures and pressures and emit visible radiation. Recent experiments have elucidated just how extreme the properties of cavitation bubbles are and have also suggested what potential new applications the bubbles might have. In one paper, Bradley Barber and Seth Putterman of the University of California at Los Angeles report that the light emitted during cavitation—known as sonoluminescence—emerges in flashes that are less than 50 picoseconds long, far shorter than anyone had expected, and that the pulses repeat with clocklike precision. In other work, Edward Flint and Kenneth Suslick of the University of Illinois at Urbana-Champaign have confirmed, by the most direct measurements to date, the long-standing expectation that the temperature during cavitation soars above 5000 K. A number of researchers have been exploiting these high temperatures for several years by using acoustic waves to accelerate various chemical reactions. Suslick and his colleagues recently reported a new application along these lines—the formation of amorphous iron.
Washington Ins & Outs: Musical Chairs at OSTP, DOE and Pentagon Leave Technology Policy a Trivial Pursuit
Authors: Goodwin Irwin
Published: January 2008

Some call it musical chairs. To the more cynical it's something like the Mad Tea Party in Alice in Wonderland, at which the participants changed seats at the direction of the Hatter. In Alice, the shuffling of seats had little effect on the individuals or on events. By contrast, the moves in Washington over the past few months are intended to make a difference at the White House Office of Science and Technology Policy and the Departments of Energy and Defense.
Modeling diffusive dynamics in adaptive resolution simulation of liquid water
Authors: Matysiak Silvina , Clementi Cecilia , Praprotnik Matej , Kremer Kurt , Delle Site Luigi
Published: January 2008

We present a dual-resolution molecular dynamics (MD) simulation of liquid water employing a recently introduced Adaptive Resolution Scheme (AdResS). The spatially adaptive molecular resolution procedure allows for changing from a coarse-grained to an all-atom representation and vice versa on-the-fly. In order to find the most appropriate coarse-grained water model to be employed with AdResS, we first study the accuracy of different coarse-grained water models in reproducing the structural properties of the all-atom system. Typically, coarse-grained molecular models have a higher diffusion constant than the corresponding all-atom models due to the reduction in degrees of freedom (DOFs) upon coarse-graining that eliminates the fluctuating forces associated with those integrated-out molecular DOFs. Here, we introduce the methodology to obtain the same diffusional dynamics across different resolutions. We show that this approach leads to the correct description of the here relevant structural, thermodynamical, and dynamical properties, i.e., radial distribution functions, pressure, temperature, and diffusion, of liquid water at ambient conditions.
Acousto-optical multiple interference devices
Authors: Beck M. , de Lima M. M. , Santos P. V.
Published: January 2008

We present a new concept for waveguide acousto-optical devices based on coupled Mach–Zehnder interferometers driven by acoustic waves. These acousto-optical multiple interference devices use the periodic refractive index modulation induced by the acoustic wave to realize functionalities such as ON/OFF switching for an arbitrary time interval, as well as for efficient light modulation at high harmonics of the acoustic frequency and pulse shaping for, e.g., integrated Q-switches. We also discuss application of the concepts to light modulation by very high acoustic frequencies, where the acoustic wavelengths become much shorter than the optical ones.
Theoretical characterization of temperature and density dependence of liquid water electronic excitation energy: Comparison with recent experimental data
Authors: D’Abramo Marco , Di Nola Alfredo , Aschi Massimiliano , Amadei Andrea
Published: January 2008

In a recent paper [Aschi et al., ChemPhysChem 6, 53 (2005)], we characterized, by means of theoretical-computational procedures, the electronic excitation of water along the typical liquid state isochore (55.32mol∕l) for a large range of temperature. In that paper we were able to accurately reproduce the experimental absorption maximum at room temperature and to provide a detailed description of the temperature dependence of the excitation spectrum along the isochore. In a recent experimental work by Marin et al. [J. Chem. Phys. 125, 104314 (2006)], water electronic excitation energy was carefully analyzed in a broad range of density and temperature, finding a remarkable agreement of the temperature behavior of the experimental data with our theoretical results. Here, by means of the same theoretical-computational procedures (molecular dynamics simulations and the perturbed matrix method), we investigate water electronic absorption exactly in the same density-temperature range used in the experimental work, hence, now considering also the absorption density dependence. Our results point out that, (1) for all the densities and temperatures investigated, our calculated absorption spectra are in very good agreement with the experimental ones and (2) the gradual maxima redshift observed increasing the temperature or decreasing the density has to be ascribed to a real shift of the lowest X̃→A electronic transition, supporting the conclusions of Marin et al.
Crystal structure of parallel-stacked peryleneimides and their application to organic field-effect transistor devices
Authors: Sato Kazuyuki , Mizuguchi Jin , Sakai Yoshimasa , Aramaki Shinji
Published: January 2008

Organic field-effect transistors (FETs) have recently attracted attention mainly because of the low fabrication cost. Parallel-stacked structure is considered favorable for realizing a high mobility along the stacked direction in organic FETs. Among our dipyridyl-peryleneimides synthesized previously for H2 sensors (OPP, MPP, and PPP for o-, m-, and p-position of the N atom in the pyridyl ring, respectively), OPP and PPP are found to crystallize in this structure and are expected to show better FET characteristics than MPP. Therefore, the FET characteristics have been studied in the present investigation from the standpoint of the crystal structure. The FET devices based on OPP and PPP exhibit n-type characteristics, showing a mobility of about 10−5cm2∕(Vs) and “on/off” ratios of about 102, whereas only poor performance was observed for the MPP-based FET.
Structural, magnetic, and transport properties of the electron-doped perovskites cobalt oxides La1−xTexCoO3 (⩽x⩽0.25)
Authors: Zheng G. H. , Zhu X. B. , Song W. H. , Sun Y. P.
Published: January 2008

The structural, magnetic, and transport properties of the electron-doped perovskites cobalt oxides La1−xTexCoO3 (0⩽x⩽0.25) have been investigated. For the structural properties, the room temperature structural transition from rhombohedra (R3¯C) to orthorhombic (Pbnm) symmetry is found in these samples with x⩾0.10 by the Rietveld refinement of x-ray powder diffraction patterns, which is ascribed to the smaller ionic radius of Te. As for the magnetic properties, firstly the spin state transition of Co3+ ions is observed in all samples, and the transition temperature shifts up to higher temperature with Te doping, which is ascribed to the smaller ionic radius and the strong acidity of Te. Secondly, it is interesting that there exists paramagnetic to ferromagnetic phase transition in the Te-doped samples. It is suggested that such a phase transition results from the introduction of Co2+ ions and the appearance of double exchange interaction between Co2+ and Co3+ due to Te doping. Moreover, Curie temperature TC increases with the increase of the Te doping level x (for x⩽0.10), and then decreases with the further increase of x. About the transport properties, the temperature dependence of the resistivity ρ shows that all samples display semiconducting behavior in the whole measured temperature region. And it can be seen that the resistivity first decreases with increasing Te doping level from x=0 to 0.10, then increases as x⩾0.15. Such variations of TC and ρ with x are suggested to be related to the structure transition.
Electrical properties of La2O3 and HfO2∕La2O3 gate dielectrics for germanium metal-oxide-semiconductor devices
Authors: Mavrou G. , Galata S. , Tsipas P. , Sotiropoulos A. , Panayiotatos Y. , Dimoulas A. , Evangelou E. K. , Seo J. W. , Dieker Ch.
Published: January 2008

Germanium metal-insulator-semiconductor capacitors with La2O3 dielectrics deposited at high temperature or subjected to post deposition annealing show good electrical characteristics, especially low density of interface states Dit in the 1011eV−1cm−2 range, which is an indication of good passivating properties. However, the κ value is estimated to be only about 9, while there is no evidence for an interfacial layer. This is explained in terms of a spontaneous and strong reaction between La2O3 and Ge substrate to form a low κ and leaky La–Ge–O germanate over the entire film thickness, which, however, raises concerns about gate scalability. Combining a thin (∼1nm) La2O3 layer with thicker HfO2 degrades the electrical characteristics, including Dit, but improves gate leakage and equivalent oxide thickness, indicating a better potential for scaling. Identifying suitable gate dielectric stack which combines good passivating/interfacial properties with good scalability remains a challenge.
Viscous flow model of creep in enamel
Authors: Schneider G. A. , He Li Hong , Swain M. V.
Published: January 2008

Recent observations have shown that enamel exhibits creep behavior during indentation. In this paper, we develop a viscous creep model for enamel that considers the basic shape of the apatite crystallites and treats the thin protein layer between the crystallites as a viscous fluid. The approach enables identification of the main flow planes in the anisotropic enamel structure and the influence of the volume fraction of the apatite crystals. Nanoindentation data showing creep are interpreted consistently and viscosities attributed to the protein layer are evaluated.
Rotational angular momentum polarization: The influence of stray magnetic fields
Authors: Marinakis Sarantos , Paterson Grant , Richmond Graham , Rockingham Michael , Costen Matthew L. , McKendrick Kenneth G.
Published: January 2008

We show that weak residual magnetic fields can significantly affect the preparation and measurement of molecular rotational angular momentum alignment in a typical gas-phase stereodynamics apparatus. Specifically, polarization spectroscopy, a third-order nonlinear spectroscopic technique, is used to prepare and probe the collisional and noncollisional losses of rotational angular momentum alignment of OH XΠ2. Residual magnetic fields of the order of the geomagnetic field are shown to have a significant effect on the prepared polarization on a submicrosecond timescale. This can be expected to be a significant effect for many gas-phase free radicals, such as those of interest in combustion, atmospheric chemistry, and the burgeoning field of cold molecules. We demonstrate a simple experimental remedy for this problem.
Transport energy in organic semiconductors with partially filled localized states
Authors: Li Ling , Meller Gregor , Kosina Hans
Published: January 2008

The charge transport in organic semiconductors has been investigated theoretically. An analytical model describing the effect of partially filled localized states on the concept of transport energy is presented, based on variable range hopping theory. The results illustrate that at low enough temperature the partially filled localized states in organic semiconductor systems play an important role on the transport energy. Moreover, the charge concentration will change the transport energy dramatically at higher carrier concentration. The paper also discusses the carrier-concentration-dependent mobility in organic semiconductors.
Calibration of an imaging crystal spectrometer for low x-ray energies
Authors: Lee S. G. , Bak J. G. , Bitter M.
Published: January 2008

An x-ray imaging crystal spectrometer was designed for the Hanbit magnetic mirror device to observe spectra of heliumlike neon at 13.4474Å. The spectrometer consists of a spherically bent mica crystal and an x-ray sensitive vacuum charge coupled device camera. This spectrometer can provide spatially resolved spectra, making it possible to obtain profiles of the ion charge state distribution from line ratios and profiles of the plasma rotation velocity from Doppler shift measurements. The paper describes measurements of spectral resolution of this instrument for low x-ray energies.
Order of magnitude enhancement in x-ray yield at low pressure deuterium-krypton admixture operation in miniature plasma focus device
Authors: Verma Rishi , Lee P. , Springham S. V. , Tan T. L. , Rawat R. S. , Krishnan M.
Published: January 2008

In a 200J fast miniature plasma focus device about 17- and 10-fold increase in x-ray yield in spectral ranges of 0.9–1.6keV and 3.2–7.7keV, respectively, have been obtained with deuterium-krypton (D2–Kr) admixture at operating pressures of ⩽0.4mbar. In the pressure range of >0.4–1.4mbar, about twofold magnification in average x-ray yield along with broadening of optimum pressure range in both spectral ranges were obtained for D2–Kr admixtures. An order of magnitude enhancement in x-ray yields at low pressures for admixture operation will help in achieving high performance device efficiency for lithography and micromachining applications.
Cavity polaritons in ZnO-based hybrid microcavities
Authors: Shimada R. , Xie J. , Avrutin V. , Özgür Ü. , Morkoč H.
Published: January 2008

Among wide-bandgap semiconductors, ZnO is a very attractive candidate for blue-ultraviolet lasers operating at room temperature owing to its large exciton binding energy and oscillator strength. Especially, ZnO-based microcavity structures are most conducive for polariton lasing at room temperature. We report the observation of cavity polaritons in bulk ZnO-based hybrid microcavities at room temperature. The bulk ZnO-based hybrid microcavities are composed of 29 pairs of Al0.5Ga0.5N∕GaN distributed Bragg reflector (DBR) at the bottom of the λ-thick cavity layer and eight pairs of SiO2∕Si3N4 DBR as the top mirror, which provided cavity Q values of ∼100. Anticrossing behavior between the lower and upper polariton branches was observed at room temperature. From the polariton dispersion curve, the vacuum Rabi splitting was estimated to be ∼50meV. These results are promising toward the realization of ZnO-based microcavity polariton devices.
Revision of “Cumulative effect of the filamentation and Weibel instabilities in counterstreaming thermal plasmas” [Phys. Plasmas 13, 102107 (2006)]
Authors: Stockem A. , Lazar M.
Published: January 2008

Dispersion formalism reported in Lazar et al. [Phys. Plasmas 13, 102107 (2006)] is affected by errors due to the misfitting of the distribution function (1) used to interpret the counterstreaming plasmas, with the general dispersion relations (4) and (5), where distribution function (1) has been inserted to find the unstable solutions. The analytical approach is reviewed here, providing a correct analytical and numerical description for the cumulative effect of filamentation and Weibel instabilities arising in initially counterstreaming plasmas with temperature anisotropies. The growth rates are plotted again, and for the cumulative mode, they are orders of magnitude larger than those obtained in Lazar et al. [Phys. Plasmas 13, 102107 (2006)]. Physically, this can be understood as an increasing of the efficiency of magnetic field generation, and rather enhances the potential role of magnetic instabilities for the fast magnetization scenario in astrophysical applications.
Vortex detection by electrical transport measurements on a single lead nanowire under axial magnetic field
Authors: Adam S. , de Menten de Horne F. , Piraux L. , Michotte S.
Published: January 2008

Electrical transport measurements were performed on single electrodeposited superconducting lead nanowires (330nm diameter) by applying a magnetic field parallel to the wire axis. We observe a vortex penetration while the nanowire is in the dissipative state generated by a phase-slip center. This results in a hysteresis in the resistance-current curves. A drop of the forward critical current leads to the disappearance of this hysteresis when the magnetic field is strong enough to stabilize the vortex at zero current. While the temperature is increased, lower magnetic fields are required to stabilize this vortex.
Behavior of stress induced leakage current in thin HfOxNy films
Authors: Jiang Ran , Li Zifeng
Published: January 2008

The behavior of stress induced leakage current (SILC) in thin HfOxNy films is investigated. Except for the H dispersive transport process, the electron trapping process is responsible for the SILC generation in HfOxNy dielectric. This trapping process is severely modulated by temperature, thickness, and stress polarity. The recovery of SILC also proves the influence of trapping process to SILC.
Negative thermal expansion in Ge-free antiperovskite manganese nitrides: Tin-doping effect
Authors: Takenaka K. , Asano K. , Misawa M. , Takagi H.
Published: January 2008

Giant negative thermal expansion (NTE) recently discovered in antiperovskite manganese nitrides Mn3AN (A=Zn,Ga, etc.) is achieved by doping Ge on A as “relaxant” of the sharp volume change at the magnetic transition. To promote wider applications, we synthesized NTE antiperovskites without expensive Ge. We discovered that Sn broadens the volume change, though less effective than Ge. Simultaneous substitution of Sn for A and C for N expands the operation-temperature window of NTE almost as broad as that of the Ge-doped counterpart. We discuss relation between the broadening and the phase instability caused by Ge or Sn.
Ultrafine-grained titanium of high interstitial contents with a good combination of strength and ductility
Authors: Xu W. , Wu X. , Sadedin D. , Wellwood G. , Xia K.
Published: January 2008

A dehydrided Ti powder of very high oxygen content was successfully consolidated using back pressure equal channel angular processing into a fully dense bulk ultrafine-grained Ti showing apparent compressive ductility as well as high true yield and ultimate strengths of 1350 and 1780MPa, respectively. Interstitial solid solution strengthening contributed to the majority of the increase in strength with additional contribution from ultrafine grains. Significantly, the material also exhibited much improved ductility for such a high interstitial content, thanks probably to the nonequilibrium grain boundaries and bimodal grain structure introduced during severe plastic deformation.
Resistive switching memory effect of ZrO2 films with Zr+ implanted
Authors: Liu Qi , Guan Weihua , Long Shibing , Jia Rui , Liu Ming , Chen Junning
Published: January 2008

The Au∕Cr∕Zr+-implanted-ZrO2∕n+-Si sandwiched structure exhibits reversible bipolar resistive switching behavior under dc sweeping voltage. The resistance ratio (Rratio) of high resistive state and low resistive state is as large as five orders of magnitude with 0.5V readout bias. Zr+-implanted-ZrO2 films exhibit good retention characteristics and high device yield. The impact of implanted Zr+ ions on resistive switching performances is investigated. Resistive switching of the fabricated structures is explained by trap-controlled space charge limited current conduction.
Defect modes merging in one-dimensional photonic crystals with multiple single-negative material defects
Authors: Chen Yihang
Published: January 2008

Twin defect modes are found to merge into each other in one-dimensional photonic crystals consisting of periodic layers of single-negative (permittivity- or permeability-negative) materials and multiple single-negative defect layers. By increasing the size or the number of the defects, the two defect modes both approach to the middle of the forbidden band gap, then merge when the photonic structure becomes nihility. In addition, the electric fields at the central frequency of the band gap could be designed to be strongly localized at just one interface between the defect layers and the periodic layers of the photonic crystal with low transmission.
Pre-College Physics Education Programs from the Research Community
Authors: Schwartz Brian B. , Wynne James J.
Published: January 2008

With the 1980s came the recognition that a crisis is developing in American education and in science and mathematics education in particular. Thus one goal coming out of President Bush's 1989 Education Summit is that “US students will be first in the world in science and mathematics” by the year 2000. Here we consider the response of three sectors of the physics research community—the professional scientific societies, the national laboratories (see figure 1) and industry—and survey the programs they offer for pre-college students and teachers. There are too many such programs for our treatment to be comprehensive and so we have chosen a representative selection. These same organizations also have many projects that deal with curriculum reform and teaching materials, as Gerhard Salinger discusses in his article on page 39. The box on page 50 summarizes the activities open to the individual researcher.
Polar Stratospheric Clouds and the Ozone Hole
Authors: Hamill Patrick , Toon Owen Brian
Published: January 2008

During the winter clouds appear in the Arctic and the Antarctic stratospheres. These clouds have been observed for over a century, and during most of that time they were considered an interesting and beautiful but relatively unimportant phenomenon. Recently, however, atmospheric scientists have found a critical relationship between the massive springtime ozone depletion over Antarctica and the formation of polar stratospheric clouds. (See figure 1.) In this article we outline the general properties of the three main types of stratospheric aerosols, and we show how changes in the levels of stratospheric nitrogen and chlorine species required for ozone depletion are dependent upon the formation of polar stratospheric clouds.
Solid C60
Authors: Huffman Donald R.
Published: January 2008

On 18 May 1990 my longtime friend and colleague Wolfgang Krätschmer called from the Max Planck Institute for Nuclear Physics in Heidelberg with a startling suggestion. The elusive molecule C60, which we had slowly come to realize was abundantly present in the carbonaceous smoke we had been making since 1983, was readily soluble in benzene, he told me. This would provide a simple technique for separating the molecule from the ordinary graphite that made up over 90% of the soot we had been producing.
Interference and Radioastronomy
Authors: Richard Thompson A. , Gergely Tomas E. , Vanden Bout Paul A.
Published: January 2008

Radioastronomy began in 1933 with Karl Jansky's accidental discovery of radio emission from the center of the Galaxy as he was studying the effect of thunderstorms on transatlantic telecommunications. Six decades later, telecommunications and other radio services are threatening the future of radioastronomy. Whether searching for the signature of a protogalaxy, studying the maseremission signposts of star formation or pursuing answers to any of the myriad questions of modern astrophysics, today's radioastronomer is often frustrated by man-made radio interference. From satellites, radar, radio and television transmitters, and wireless personal communication systems of all sorts to microwave ovens, computers and even garage door openers, the same technology that lets us study the universe at radio wavelengths is producing a flood of man-made signals. Figure 1 illustrates how noisy the radio spectrum has become at wavelengths around 1 meter. (The remedy offered in the figure is, alas, just an astronomer's fantasy.)
Theoretical Astrophysics
Authors: McKee Christopher F. , Press William H.
Published: January 2008

Astronomy is an observational science, not an experimental one. As a result, theory plays a particularly important role in the field. It provides the basic paradigms within which observations are framed and without which they degenerate into catalogs of uninterpreted data. At its most satisfying, theory makes predictions that are later verified by observation. But theory can also have a dramatic “postdictive” impact by explaining previously observed phenomena. It can catalyze specific new observations, which in turn stimulate models. Finally, theory provides much of the conceptual stimulation that invests astronomy with excitement.
Information is Physical
Authors: Landauer Rolf
Published: January 2008

Thermodynamics arose in the 19th century out of the attempt to understand the performance limits of steam engines in a way that would anticipate all further inventions. Claude Shannon, after World War II, analyzed the limits of the communications channel. It is no surprise, then, that shortly after the emergence of modern digital computing, similar questions appeared in that field. It was not hard to associate a logic gate with a degree of freedom, then to associate kT with that, and presume that this energy has to be dissipated at every step. Similarly, it seemed obvious to many that the uncertainty principle, ΔEΔt∼ℏ, could be used to calculate a required minimal energy involvement, and therefore energy loss, for very short Δt.
Localization of Light
Authors: John Sajeev
Published: January 2008

Since the beginning of scientific inquiry the nature of light has played a vital role in our understanding of the physical world. Physicists have marveled at the dual nature of light as both corpuscle and wave; we have harnessed the remarkable coherent properties of light through the use of lasers; and the quantum mechanics of the interaction of photons with matter continue to provide fascinating avenues of basic research. In essence, any alteration of electromagnetism, the fundamental interaction overning atomic, molecular and condensed matter physics, will lead to fundamentally new phenomena in all these areas.
Functional evolution of the p53 regulatory network through its target response elements
Authors: Jegga Anil G. , Inga Alberto , Menendez Daniel , Aronow Bruce J. , Resnick Michael A.
Published: January 2008

Transcriptional network evolution is central to the development of complex biological systems. Networks can evolve through variation of master regulators and/or by changes in regulation of genes within networks. To gain insight into meaningful evolutionary differences in large networks, it is essential to address the functional consequences of sequence differences in response elements (REs) targeted by transcription factors. Using a combination of custom bioinformatics and multispecies alignment of promoter regions, we investigated the functional evolution of REs in terms of responsiveness to the sequence-specific transcription factor p53, a tumor suppressor and master regulator of stress responses. We identified REs orthologous to known p53 targets in human and rodent cells or alternatively REs related to the established p53 consensus. The orthologous REs were assigned p53 transactivation capabilities based on rules determined from model systems, and a functional heat map was developed to visually summarize conservation of sequence and relative level of responsiveness to p53 for 47 REs in 14 species. Individual REs exhibited marked differences in transactivation potentials and widespread evolutionary turnover. Functional differences were often not predicted from consensus sequence evaluations. Of the established human p53 REs analyzed, 91% had sequence conservation in at least one nonprimate species compared with 67.5% for functional conservation. Surprisingly, there was almost no conservation of functional REs for genes involved in DNA metabolism or repair between humans and rodents, suggesting important differences in p53 stress responses and cancer development.
Isotopic evidence for omnivory among European cave bears: Late Pleistocene
Ursus spelaeus
from the Peştera cu Oase, Romania
Authors: Richards Michael P. , Pacher Martina , Stiller Mathias , Quilès Jérôme , Hofreiter Michael , Constantin Silviu , Zilhão João , Trinkaus Erik
Published: January 2008

Previous bone collagen carbon and nitrogen isotopic studies of Late Pleistocene European cave bears (
Ursus spelaeus
) have shown that these bears frequently had low nitrogen isotope values, similar to those of herbivores and indicating either unusual physiology related to hibernation or a herbivorous diet. Isotopic analysis of animal bone from the Peştera cu Oase (Cave with Bones), Romania, shows that most of its cave bears had higher nitrogen isotope values than the associated herbivores and were, therefore, omnivorous. The Oase bears are securely identified as cave bears by both their morphology and DNA sequences. Although many cave bear populations may have behaved like herbivores, the Oase isotopic data demonstrate that cave bears were capable of altering their diets to become omnivores or even carnivores. These data therefore broaden the dietary profile of
U. spelaeus
and raise questions about the nature of the carnivore guild in Pleistocene Europe.
Acute Leakage Patterns of Fluorescent Plasma Flow Markers after Transient Focal Cerebral Ischemia Suggest Large Openings in Blood‐Brain Barrier
Authors: Nagaraja Tavarekere N. , Keenan Kelly A. , Fenstermacher Joseph D. , Knight Robert A.
Published: January 2008

Objective: This study tested the hypothesis that blood‐brain barrier (BBB) opening during acute reperfusion permits the passage of smaller macromolecules but not larger ones and that this molecular size restriction disappears over time.

Methods: Following 3 hours (h) of unilateral middle cerebral artery occlusion and either 3 or 21 h of reperfusion, Wistar rats (n = 42) were injected with Evans blue (EB, a fluorescent dye that binds instantly to plasma albumin yielding EB‐tagged albumin, EB‐Alb) and with one of three fluorescent dextrans ranging in size from 77‐ to 2000‐kDa. During occlusion and reperfusion, ischemic status of the affected tissue was confirmed by magnetic resonance imaging (MRI). Blood‐to‐brain transfer of the dextrans relative to that of EB‐Alb was examined by fluorescence microscopy within three regions with ischemic damage.

Results: Increase in EB‐Alb leakage from 3 to 21 h of reperfusion was significant (from 40–60% to 80–90% of fields examined; p < 0.05). Co‐leakage of the largest dextran used 2000‐kDa, with EB‐Alb was observed in only 40% of the fields at 3+3 h, but nearly in all at 3 + 21 h (p < 0.01). Parenchymal distribution of the tracers differed among the fields and included considerable cellular uptake of EB‐Alb and some of dextrans.

Conclusions: Supporting the hypothesis, opening of the BBB was insufficient to allow passage of the largest dextran at 3 + 3 h in about 40% of the microvascular networks viewed. The number of total leaky microvascular beds increased by nearly 50% between 3 + 3 h and 3 + 21 h.
Static Magnetic Fields Affect Capillary Flow of Red Blood Cells in Striated Skin Muscle
Authors: Brix Gunnar , Strieth Sebastian , Strelczyk Donata , Dellian Marc , Griebel JüRgen , Eichhorn Martin E. , Andrā Wilfried , Bellemann Matthias E.
Published: January 2008

Blood flowing in microvessels is one possible site of action of static magnetic fields (SMFs). We evaluated SMF effects on capillary flow of red blood cells (RBCs) in unanesthetized hamsters, using a skinfold chamber technique for intravital fluorescence microscopy. By this approach, capillary RBC velocities (vRBC), capillary diameters (D), arteriolar diameters (Dart), and functional vessel densities (FVD) were measured in striated skin muscle at different magnetic flux densities. Exposure above a threshold level of about 500 mT resulted in a significant (P < 0.001) reduction of vRBC in capillaries as compared to the baseline value. At the maximum field strength of 587 mT, vRBC was reduced by more than 40%. Flow reduction was reversible when the field strength was decreased below the threshold level. In contrast, mean values determined at different exposure levels for the parameters D, Dart, and FVD did not vary by more than 5%.

Blood flow through capillary networks is affected by strong SMFs directed perpendicular to the vessels. Since the influence of SMFs on blood flow in microvessels directed parallel to the field as well as on collateral blood supply could not be studied, our findings should be carefully interpreted with respect to the setting of safety guidelines.
Frequency of Fish Consumption, Retinal Microvascular Signs and Vascular Mortality
Authors: Kaushik Shweta , Wang Jie Jin , Flood Victoria , Liew Gerald , Smith Wayne , Mitchell Paul
Published: January 2008

Objective: Fish consumption has established cardiovascular and cerebrovascular benefits, but its effects on microvascular structure have not been examined in population‐based studies. We investigated this association, in relation to vascular mortality in an Australian cohort (1992–2004).

Methods: Of 3654 participants aged 49+ years, 2683 (73%) with available data were included. Retinal arteriolar and venular diameters were measured, and signs of arterio‐venous nicking and retinopathy were assessed from digital retinal images. Fish consumption was evaluated using a food frequency questionnaire.

Results: Both wider mean arteriolar diameter (p = 0.002) and narrower venular diameter (p = 0.02) were associated with increasing frequency of consuming any or oily fish, after adjusting for cardiovascular risk factors, diet, inflammatory factors and socioeconomic status. This association was mainly present in persons with hypertension. Greater frequency of fish consumption was associated with a reduced prevalence of arterio‐venous nicking and a borderline significant trend for reduced retinopathy prevalence. Ten year stroke‐related mortality was significantly lower in persons consuming fish at least once per week compared to less frequent consumption (hazard ratio 0.57, 95% CI: 0.35 to 0.93).

Conclusions: Recent evidence shows that narrower arterioles and wider venules may predict vascular events. Our new findings suggest that the vascular protective effects of consuming fish could act, in part, by preventing pathological microvasculature change.
Kupffer Cells Are Mandatory for Adequate Liver Regeneration by Mediating Hyperperfusion via Modulation of Vasoactive Proteins
Authors: Abshagen Kerstin , Eipel Christian , Kalff Jörg C. , Menger Michael D. , Vollmar Brigitte
Published: January 2008

Objective:Physiological liver regeneration requires adequate microvascular perfusion after partial hepatectomy. Although Kupffer cells (KCs) are known to play a key role in modulating hepatocyte proliferation, their impact on regulating hepatic microcirculation during liver regeneration has so far been disregarded. With respect to their expression and modulation of vasoactive mediators, KCs may provide important signals that regulate hepatic perfusion during liver regeneration.

Methods:Intravital fluorescence microscopy, immunohistochemistry, Western blot analysis, and RT‐PCR were used to analyze livers of KC‐depleted mice (liposome‐encapsulated clodronate application) and KC‐competent mice at days 3, 5, and 8 after 68% hepatectomy.

Results:Selective and long‐lasting KC elimination limited the resection‐associated hyperperfusion, as evidenced by an only 1.7‐ to 2‐fold increase of sinusoidal volumetric blood flow and shear stress in contrast to a 3.5‐ to 5‐fold increase in KC‐competent mice. In accordance to that livers of KC‐depleted mice showed an altered pattern of vasoregulatory gene expression. KC‐depleted mice failed to show resection‐induced increase of HO‐1 and eNOS protein expression, but revealed a reduction of hepatic eNOS and HO‐1 protein levels to 22 and 12% of the corresponding values in KC‐competent mice. In addition, the eNOS inhibitory protein caveolin‐1 was increased in KC‐depleted animals prior to as well as after resection. Furthermore, resection‐associated accumulation of ET‐1 mRNA was absent in KC‐depleted livers. Finally, liver mass restoration was impaired, with a regain of only 79% weight within 8 days after resection in KC‐depleted mice.

Conclusion:The present study documents a remarkable change of the vasoactive mediator profile upon KC‐depletion and liver resection, limiting intrahepatic hyperperfusion. Therefore, KC‐dependent molecular mechanisms seem to be mandatory in regulating vasotonus during the process of liver regeneration and therewith maintaining intrahepatic shear stress as a trigger of hepatic proliferation.
Effects of twin pregnancy and periconceptional undernutrition on maternal metabolism, fetal growth and glucose–insulin axis function in ovine pregnancy
Authors: Rumball C. W. H. , Harding J. E. , Oliver M. H. , Bloomfield F. H.
Published: January 2008

Although twins have lower birthweights than singletons, they may not experience the increased disease risk in adulthood reportedly associated with low birthweight. In contrast, another periconceptional event, maternal undernutrition, does not reduce birthweight but does affect fetal and postnatal physiology in sheep. We therefore studied maternal and fetal metabolism, growth and glucose–insulin axis function in late gestation in twin and singleton sheep pregnancies, either undernourished from 60 days before until 30 days after conception or fed ad libitum. We found that twin‐bearing ewes had decreased maternal food intake in late gestation and lower maternal and fetal plasma glucose and insulin levels. Twin fetuses had fewer everted placentomes, grew slower in late gestation, and had a greater insulin response to a glucose challenge, but lesser response to arginine. In contrast, periconceptional undernutrition led to increased maternal food intake and a more rapid fall in maternal glucose levels in response to fasting. Periconceptional undernutrition increased the number of everted placentomes, and abolished the difference in insulin responses to glucose between twins and singletons. Thus, the physiology of twin pregnancy is quite different from that of singleton pregnancy, and is probably determined by a combination of factors acting in both early and late gestation. The inconsistency of the relationships between low birthweight and postnatal disease risk of twins may lie in their very different fetal development. These data suggest that twin pregnancy may be another paradigm of developmental programming, and indicate that twins and singletons must be examined separately in any study of fetal or postnatal physiology.