bluuebunny/crossref_metadata_2025 huggingface dataset:
Vortex motion in magnetic disks with different geometric asymmetry
Authors: Wu Kuo-Ming , Wang Jia-Feng , Wu Yin-Hao , Lee Ching-Ming , Wu Jong-Ching , Horng Lance
Published: February 2008

An asymmetric disk achieves control over the clockwise and counterclockwise vortex states in a magnetic disk with an in-plane magnetic field. In this study, the influence of different geometric asymmetry on the vortex motion in 800nm disks has been studied. The excised angle, defined as half of the center angle corresponding to the excised arc, is flatted varying from 15° to 90°. For each asymmetric degree disk, the vortex motion is investigated through anisotropic magnetoresistance measurement and hysteresis loops recorded by focused magneto-optic Kerr effect magnetometry. The vortex nucleation and annihilation fields show strong dependence and different sensitivity on the asymmetry of disk. An interestingly evident switching mode change is also observed at particular excised angle. Numerical simulations, corresponding to realistically identical system, are calculated and agree well with the experimental results.
Limits of validity of photon-in-cell simulation techniques
Authors: Reitsma A. J. W. , Jaroszynski D. A.
Published: February 2008

A comparison is made between two reduced models for studying laser propagation in underdense plasma; namely, photon kinetic theory and the slowly varying envelope approximation. Photon kinetic theory is a wave-kinetic description of the electromagnetic field where the motion of quasiparticles in photon coordinate-wave number phase space is described by the ray-tracing equations. Numerically, the photon kinetic theory is implemented with standard particle-in-cell techniques, which results in a so-called photon-in-cell code. For all the examples presented in this paper, the slowly varying envelope approximation is accurate and therefore discrepancies indicate the failure of photon kinetic approximation for these cases. Possible remedies for this failure are discussed at the end of the paper.
Evidences of alkali-induced softening of the oxygen-substrate bond
Authors: Politano A. , Formoso V. , Agostino R. G. , Colavita E. , Chiarello G.
Published: February 2008

The interaction of oxygen with alkalis (Na, K) on Ni(111) was studied by high-resolution electron energy loss spectroscopy. Loss measurements revealed for the first time a softening of the O–Ni bond and, simultaneously, a strengthening of the alkali-Ni bond in the alkali+O coadsorbed phase, in perfect agreement with recent theoretical calculations. The weakening of the O–Ni bond was ascribed to the alkali-induced filling of the O 2pz antibonding orbitals. Different physical mechanisms were discussed for explaining the strengthening of the alkali-substrate bond whenever alkalis are coadsorbed with O adatoms.
Development of transferable interaction potentials for water. V. Extension of the flexible, polarizable, Thole-type model potential (TTM3-F, v. 3.0) to describe the vibrational spectra of water clusters and liquid water
Authors: Fanourgakis George S. , Xantheas Sotiris S.
Published: February 2008

We present a new parametrization of the flexible, polarizable Thole-type model for water [J. Chem. Phys. 116, 5115 (2002); J. Phys. Chem. A 110, 4100 (2006)], with emphasis in describing the vibrational spectra of both water clusters and liquid water. The new model is able to produce results of similar quality with the previous versions for the structures and energetics of water clusters as well as structural and thermodynamic properties of liquid water evaluated with classical and converged quantum statistical mechanical atomistic simulations. At the same time it yields accurate redshifts for the OH vibrational stretches of both water clusters and liquid water.
Growth, magnetotransport, and magnetic properties of ferromagnetic (In,Mn)Sb crystals
Authors: Ganesan K. , Bhat H. L.
Published: February 2008

In 1 − x Mn x Sb crystals are grown with different Mn doping concentrations (x=0.006, 0.01, 0.02, and 0.04) beyond the equilibrium solubility limit by the horizontal Bridgman technique. Structural, magnetic, and magnetotransport properties of the grown crystals are studied in the temperature range 1.4–300 K. Negative magnetoresistance and anomalous Hall effect are observed below 10 K. The anomalous Hall coefficient is found to be negative. The temperature dependence of the magnetization measurement shows a magnetic ordering below 10 K, which could arise from InMnSb alloy formation. Also, the saturation in magnetization observed even at room temperature suggests the existence of ferromagnetic MnSb clusters in the crystals, which has been verified by scanning electron microscopy studies. The carrier concentration increases with Mn doping, and this results in a decrease of resistivity. The carrier concentration and mobility at room temperature for the doped crystals are ∼2×1019 cm−3 and ∼200 cm2/V s, respectively. The observed anomalous Hall effect suggests the carrier mediated ferromagnetism below 10 K in In1−xMnxSb crystals.
Spin transfer switching of closely arranged multiple pillars with current-perpendicular-to-plane spin valves
Authors: Machida Kenji , Funabashi Nobuhiko , Aoshima Ken-ichi , Miyamoto Yasuyoshi , Kawamura Norikazu , Kuga Kiyoshi , Shimidzu Naoki
Published: February 2008

Spin transfer switching (STS) characteristics of two closely arranged spin valve (SV) pillars sharing a pair of top and bottom electrodes were investigated. Each pillar had a 300×100nm2 rectangular shape, which was fabricated by electron beam lithography. The separation between the pillars was 300nm or 1μm. The STS curves clearly show the two-step switching of the free layer for the device with a separation of 300nm. The first switching occurred at a switching current density of a single SV pillar or below. The second switching occurred at a switching current density approximately 1.2 times the first one. Furthermore, the STS characteristics of the paired free layers were estimated by a micromagnetic simulation using the Landau–Lifshitz–Gilbert–Slonczewski equation, which showed similar switching behavior to the experimental result of the free layers switched first.
Large anomalous Hall resistance of pair δ-doped GaAs structures grown by molecular-beam epitaxy
Authors: Jung D. W. , Noh J. P. , Touhidul Islam A. Z. M. , Otsuka N.
Published: February 2008

Beryllium/silicon pair δ-doped GaAs structures grown by molecular-beam epitaxy exhibit a Hall resistance which has a nonlinear dependence on the applied magnetic field and which is strongly correlated to the negative magnetoresistance observed under the applied magnetic field parallel to the δ-doped layers. Dependence of the occurrence of the nonlinear Hall resistance on the growth condition is investigated. A significantly large increase in both the magnitude and the nonlinearity of the Hall resistance is observed from samples whose GaAs buffer layers are grown under the condition of a low As∕Ga flux ratio. Reflection high energy electron diffraction and electron microscope observations show that a faceted surface develops with the growth and postgrowth annealing of a GaAs buffer layer under the condition of a low As flux. From samples which have only Si δ-doped layers and exhibit the n-type conduction, such nonlinear Hall resistance is not observed. The nonlinearity of the Hall resistance of Be∕Si pair δ-doped structures depends on the single parameter B∕T, where B and T are the applied magnetic field and the temperature, respectively. Based on these results, it is suggested that the nonlinear Hall resistance of Be∕Si pair δ-doped structures is the anomalous Hall effect caused by localized spins in δ-doped layers.
RheoDSC: A hyphenated technique for the simultaneous measurement of calorimetric and rheological evolutions
Authors: Kiewiet S. , Janssens V. , Miltner H. E. , Van Assche G. , Van Puyvelde P. , Van Mele B.
Published: February 2008

A newly developed hyphenated technique is presented combining an existing rheometer and differential scanning calorimeter into a single experimental setup. Through the development of a fixation accessory for differential scanning calorimeter (DSC) crucibles and a novel rotor, the simultaneous measurement is performed inside the well-controlled thermal environment of a Tzero™ DSC cell. Hence, the evolution of thermal and flow properties of a material can be simultaneously measured using steady or oscillatory shear measurements and regular or modulated temperature DSC measurements. Along with the construction of a prototype, a validation of the design was performed. The technique offers interesting opportunities for the investigation of flow-induced transitions, for instance, crystallization or phase separation, and provides an asset for high-throughput screening of materials. The potential of the novel technique is demonstrated by two case studies: the chemorheology during the cure of a thermosetting epoxy-amine system and the flow-induced crystallization of syndiotactic polypropylene.
Fe–(Au,Cu)–B two-phase magnetic microwires with exchange coupled nanosized grains
Authors: Lupu N. , Óvári T. A. , Corodeanu S. , Chiriac H.
Published: February 2008

Results on the magnetic behavior of glass-coated magnetic microwires prepared from the Fe87Au2−xCuxB11 alloy system are reported for the first time. The changes induced in their axial magnetization process by the substitution of Au with Cu have been studied. Hysteresis loops with typical shapes for soft magnetic materials have been observed in all cases except for x=1.5at.% of Cu. Fe87Au0.5Cu1.5B11 microwires display a two-step hysteresis loop with a plateau at zero magnetization. The observed change in the axial magnetization process of Fe–(Au,Cu)–B microwires with Cu content has been explained considering the average distance among adjacent α-(Fe,Cu) nanosized grains to be smaller than the exchange length. In this way, the ensemble of grains is collectively magnetized and it behaves as a single material from the magnetic point of view. The remainder amorphous matrix is also collectively magnetized, and the resulting stepped loop is the result of the magnetostatic coupling between these two systems: the grain ensemble and the amorphous matrix. The results demonstrate the effectiveness of composition control on the magnetic properties of Fe–(Au,Cu)–B microwires and open up new application opportunities for glass-coated microwires.
Ab initio calculation on ferromagnetic reduced anatase TiO2−δ
Authors: Zuo Xu , Yoon Soack-Dae , Yang Aria , Vittoria Carmine , Harris Vincent G.
Published: February 2008

The room-temperature ferromagnetism of reduced anatase (TiO2−δ) is studied using density functional calculation. Two kinds of point defects, titanium interstitial and oxygen vacancy (Ov), have been studied. The calculated magnetization shows that Ov is the point defect substantially related to the observed ferromagnetism. A model of the ferromagnetism is given based on the spin-polarized Ti3F+ cluster and the double exchange between the clusters. The calculated density of states supports the model and is in agreement with the donor impurity band exchange model.
Low loss porous terahertz fibers containing multiple subwavelength holes
Authors: Hassani Alireza , Dupuis Alexandre , Skorobogatiy Maksim
Published: February 2008

We propose a porous polymer terahertz fiber with a core composed of a hexagonal array of subwavelength air holes. Numerical simulations show that the larger part of guided power propagates inside the air holes within the fiber core, resulting in suppression of the bulk absorption losses of the core material by a factor of ∼10–20. Confinement of terahertz power in the subwavelength holes greatly reduces effective refractive index of the guided mode but not as much as to considerably increase modal radiation losses due to bending. As a result, tight bends of several centimeter bending radii can be tolerated.
Au(Si)-filled β-Ga2O3 nanotubes as wide range high temperature nanothermometers
Authors: Gong N. W. , Lu M. Y. , Wang C. Y. , Chen Y. , Chen L. J.
Published: February 2008

Au(Si)-filled β-Ga2O3 nanotubes were fabricated by an effective one-step chemical vapor deposition method. The Au(Si) interior was introduced by capillarity. Linear thermal expansion of Au(Si) with a coefficient of thermal expansion (CTE) as high as 1.5×10−4(1∕K) within single crystal Ga2O3 shell up to 800°C was observed by in situ transmission electron microscopy. The high CTE is correlated to partial melting of Au(Si). As Ga2O3 possesses excellent thermal and chemical stability, the structure can be used as a wide range high-temperature nanothermometer within localized regions of nanosystems.
Self-ordered InGaAs quantum dots grown at low growth rates
Authors: Huang Chun-Yuan , Wu Meng-Chyi , Shen Jeng-Jung , Lin Shih-Yen
Published: February 2008

This study explores the effects of the growth rate on InGaAs∕GaAs quantum dots (QDs) in producing ordered QD arrays. Surface morphological observations reveal that the dot density decreases as the growth rate increases and the QDs can be gradually self-ordered in the [11¯0] direction. The threshold growth rate for one-dimensional self-ordered QD arrays is 0.054μm∕h. This phenomenon is attributed to the preferential QD nucleation at the local strain maximum which is at the edge of the elongated step bunch. After the step bunches that elongated along [11¯0] become the main feature on the wetting layer surface, the accumulated strain field on both step edges favors the nucleation of QDs. However, the concurrent decrease in QD size and the thinning of the wetting layer may be associated with the desorption of In and Ga adatoms and the lateral mass transport, respectively.
ZnO epitaxy on (111) Si using epitaxial Lu2O3 buffer layers
Authors: Guo W. , Allenic A. , Chen Y. B. , Pan X. Q. , Tian W. , Adamo C. , Schlom D. G.
Published: February 2008

We report the growth and characterization of single-crystalline, crack-free, epitaxial (0001) ZnO films on (111) Si substrates using intervening epitaxial Lu2O3 buffer layers. The epitaxial orientation relationships are (0001)ZnO∥(111)Lu2O3∥(111)Si and [12¯10]ZnO∥[1¯10]Lu2O3∥[11¯0]Si. X-ray diffraction and transmission electron microscopy reveal that the ZnO films have high structural quality and an atomically sharp ZnO∕Lu2O3 interface. Temperature-dependent photoluminescence measurements show optical properties comparable to ZnO single crystals. The films have a resistivity of 0.31Ωcm, an electron concentration of 2.5×1017cm−3, and a mobility of 80cm2∕V⋅s at room temperature. The epitaxial growth of ZnO on Si represents a significant step toward the integration of ZnO-based multifunctional devices with Si electronics.
Bayesian and maximum entropy methods for fusion diagnostic measurements with compact neutron spectrometers
Authors: Reginatto Marcel , Zimbal Andreas
Published: February 2008

In applications of neutron spectrometry to fusion diagnostics, it is advantageous to use methods of data analysis which can extract information from the spectrum that is directly related to the parameters of interest that describe the plasma. We present here methods of data analysis which were developed with this goal in mind, and which were applied to spectrometric measurements made with an organic liquid scintillation detector (type NE213). In our approach, we combine Bayesian parameter estimation methods and unfolding methods based on the maximum entropy principle. This two-step method allows us to optimize the analysis of the data depending on the type of information that we want to extract from the measurements. To illustrate these methods, we analyze neutron measurements made at the PTB accelerator under controlled conditions, using accelerator-produced neutron beams. Although the methods have been chosen with a specific application in mind, they are general enough to be useful for many other types of measurements.
Pseudocrystallization of SiO2 and superhardness effects of AlN∕SiO2 nanomultilayers
Authors: Zhao Wenji , Kong Ming , Wu Ying , Li Geyang
Published: February 2008

Al N ∕ Si O 2 nanomultilayers with different SiO2 thicknesses were synthesized by reactive magnetron sputtering. X-ray diffraction and high-resolution transmission electron microscopy were used to characterize the microstructure, and nanoindentation technology was used to measure the mechanical properties of the multilayers. The crystallization of SiO2 as well as its influences on the growth and mechanical properties of the multilayers was studied. Results showed that due to the template effects of hcp AlN, amorphous SiO2 was forced to crystallize to a hcp pseudocrystal structure when its thickness was below 0.6nm. The SiO2 epitaxially grew with AlN in the multilayer with coherent interfaces. At this time, a tensile and compressive alternate stress field was developed corresponding to the modulation structure. The hardness of the multilayers was enhanced as a result. Calculation revealed that alternate stress field played an important role in multilayers’ reinforcement. As thickness increases, SiO2 grew into amorphous again, resulting in the blockade of epitaxial growth in the multilayers and disappearing of the hardness enhancement.
Electronic structures of Nb–W bulk and surface from first principles calculation
Authors: Gong H. R. , Nishi Yoshio , Cho Kyeongjae
Published: February 2008

First principles calculation shows that the Nb and W atoms have a tendency to mix instead of phase separate in the Nb–W bulk within the entire composition range, and the interaction between Nb and W atoms has a nonlinear effect on the density of states of the Nb–W bulk at the Fermi level. Calculation also reveals that the surface segregation of Nb atoms is energetically favorable with an energy decrease of 0.4–0.55eV/atom, and the segregation has important effects on the electronic structures of Nb–W surfaces. Interestingly, the work function of Nb–W phases is insensitive to the composition as well as the Nb surface segregation when W is in the range of 0–60at.%, and over this composition range, the work function remains relatively stable.
Influence of the Ge concentration in the virtual substrate on the low frequency noise in strained-Si surface n-channel metal-oxide-semiconductor field-effect transistors
Authors: Fobelets Kristel , Rumyantsev Sergey L. , Shur Michael S. , Olsen Sarah H.
Published: February 2008

We report on low frequency noise and field-effect mobility in strained-Si surface n-channel metal-oxide-semiconductor field-effect transistors (MOSFETs) grown on relaxed virtual substrates with a Ge concentration varying between 0% and 30%. An increased Ge concentration results in higher intrinsic field-effect mobility, increasing from 380cm2V−1s−1 for the unstrained channel to 865cm2V−1s−1 for the strained-Si MOSFET on 30% relaxed SiGe virtual substrate. However, the higher mobility is traded off for increased substrate leakage currents and increased 1∕f (flicker) noise. It is suggested that flicker noise is due to traps in the oxide layer. The density of traps increases from 2×1017eV−1cm−3 for 0% Ge to 2.3×1018eV−1cm−3 for the 30% Ge virtual substrate.
Miniature electrostatic electron energy analyzers and S-shaped deflector
Authors: Williams J. F. , Chen X. , Wilkie P.
Published: February 2008

An instrument has been developed to avoid the rotation of large electron sources and detectors in quantum single particle scattering experiments. The rotation of an electron beam has been achieved by combining three small cylindrical electrostatic electron energy analyzers in series such that the first analyzer is fixed and the other two rotate together around the exit axis of the first; it is a development from an S-shaped deflector used by Hegemann et al. [J. Phys. B 26, 4607 (1993)]. Novel design and construction, using copper, aluminum, and stainless steel parts mounted on polyvinyl printed circuit board, enabled an efficient, small-sized high vacuum compatible instrument. The characteristics and versatility of the instrument have been shown by measurements of angular and spin asymmetries of electron scattering phenomena.
Ferroelectric 90° domain structure in a thin film of BaTiO3 fine ceramics observed by 300kV electron holography
Authors: Matsumoto Takao , Koguchi Masanari , Suzuki Keigo , Nishimura Hitoshi , Motoyoshi Yasuhiro , Wada Nobuyuki
Published: February 2008

We observed 90° ferroelectric domain structure in a thin film of BaTiO3 by 300kV electron holography, especially paying attention to beam-induced influence on the polarization and diffraction effect. The beam-induced influence was minimized by recording holograms on high-resolution films at low electron-optical magnification. As for the diffraction effect, we chose such an orientation of the specimen as to minimize the corresponding amplitude contrast. Furthermore, to minimize any phase shifts that are not intrinsic to ferroelectricity, such as the mean-inner potential of the material or the electron-beam-induced charging under the illumination condition, we calculated the difference between phase images taken below and above the Curie temperature of the material to obtain a consistent value for the spontaneous polarization.
Extremely high flexibilities of Coulomb blockade and negative differential conductance oscillations in room-temperature-operating silicon single hole transistor
Authors: Lee Sejoon , Miyaji Kousuke , Kobayashi Masaharu , Hiramoto Toshiro
Published: February 2008

A unique feature of the extremely long-range-extended blockade regime with its shape of a long stick, where the Coulomb blockade oscillation and negative differential conductance peak-positions can be systematically and precisely modulated for both extremely-wide VG and VD ranges, was clearly observed in a room-temperature-operating silicon single hole transistor. These results originate from the large quantum level spacing, large tunnel-barrier height, small tunnel-barrier curvature, small bias-induced barrier modulation, and large voltage gain, attributing to the formation of an ultrasmall dot in the gently sloped tunnel barriers along the [100] Si nanowire channel having the large subband modulation.
Passivated p-type silicon: Hole injection tunable anode material for organic light emission
Authors: Zhao W. Q. , Ran G. Z. , Xu W. J. , Qin G. G.
Published: February 2008

We find that hole injection can be enhanced simply by selecting a lower-resistivity p-Si anode to match an electron injection enhancement for organic light emitting diodes with ultrathin-SiO2-layer-passivated p-Si anode (Si-OLED). For a Si-OLED with ordinary AlQ electron transport layer, the optimized resistivity of the p-Si anode is 40Ωcm; for that with n-doped Bphen electron transport layer, it decreases to 5Ωcm. Correspondingly, the maximum power efficiency increases from 0.3to1.9lm∕W, even higher than that of an indium tin oxide control device (1.4lm∕W). This passivated p-type silicon is a hole injection tunable anode material for OLED.
Evidence of hot electron-induced chemical degradation in electroluminescence spectra of polyethylene
Authors: Teyssedre Gilbert , Laurent Christian
Published: February 2008

Unlike semiconducting organics, insulating polymers exhibit electroluminescence features that cannot be interpreted on the basis of the photophysical properties of the material. In particular, it is shown for the first time that the spectral components observed in electroluminescence of polyethylene can only be reproduced when the material is irradiated by an electron beam. This shows that hot electron impact is a driving process in electroluminescence and that the excited states decay route goes along the chemical pathway ending with molecular fragmentation. From these results, electroluminescence and electrical degradation can be associated in an implicit scheme, opening the way for defining safety limits in terms of electric stresses applied to a material for a given application.
Microscopic calculation and measurement of the laser gain in a (GaIn)Sb quantum well structure
Authors: Bückers C. , Thränhardt A. , Koch S. W. , Rattunde M. , Schulz N. , Wagner J. , Hader J. , Moloney J. V.
Published: February 2008

A detailed microscopic calculation and experimental measurements of the optical gain from a (GaIn)Sb structure are presented. For a given excitation density, the gain in the (GaIn)Sb material system considerably exceeds that of a comparable equivalent (GaIn)As∕GaAs structure. The physical reasons for this high gain are analyzed and attributed mostly to band structure effects.
A low-loss, robust setup for double optical gating of high harmonic generation
Authors: Gilbertson Steve , Mashiko Hiroki , Li Chengquan , Khan Sabih D. , Shakya Mahendra M. , Moon Eric , Chang Zenghu
Published: February 2008

Previously, a second harmonic field was added to a polarization gating field by a Mach–Zehnder interferometer to gate the high harmonic generation process in argon gas. To reduce the losses of the interferometer, we developed a collinear setup consisting of only two quartz plates and a barium borate crystal. The high intensity at the focus allowed the double optical gating to be performed on neon gas. As a result, a supercontinuous spectrum was produced capable of supporting 130as. There is no delay jitter between the second harmonic field and the polarization gating field associated in this setup, which is necessary for generating stable single isolated attosecond pulses.
Study of residual background carriers in midinfrared InAs∕GaSb superlattices for uncooled detector operation
Authors: Haugan H. J. , Elhamri S. , Szmulowicz F. , Ullrich B. , Brown G. J. , Mitchel W. C.
Published: February 2008

The midinfrared 7 ML InAs/8 ML GaSb superlattices (SLs) were grown by molecular beam epitaxy at growth temperatures between 370 and 430°C in order to study the intrinsic characteristic of background carriers. Grown SLs were all residual p type with carrier densities in the low 1011cm−2, and a minimum density of 1.8×1011cm−2 was obtained from the SL grown at 400°C. With increasing growth temperature, the in-plane carrier mobility decreased from 8740to1400cm2∕Vs due to increased interfacial roughness, while the photoluminescence intensity increased sixfold due to a decrease in the nonradiative defect densities.
Magnetotransport, noise, and x-ray magnetic circular dichroism studies of pulsed laser deposited Fe3O4 film on Si substrates
Authors: Choudhary R. J. , Tiwari Shailja , Phase D. M. , Kumar Ravi , Thakur P. , Chae K. H. , Choi W. K.
Published: February 2008

Electrical fluctuation, magnetic, and magneto-transport properties of the (111) oriented Fe3O4 thin film deposited by pulsed laser deposition on technologically important silicon substrate have been studied. Low frequency conduction noise follows the trend of resistivity behavior with respect to temperature and the normalized value of noise drops by two orders of magnitude below the Verwey transition. At room temperature, magnetoresistance of the film is 5% at 8T. X-ray magnetic circular dichroism measurements performed on 10nm thick film of Fe3O4 indicate a single crystal-like uniform distribution of Fe ions in its crystal or magnetic structure.
Distinct band gaps and isotropy combined in icosahedral band gap materials
Authors: Sutter-Widmer D. , Neves P. , Itten P. , Sainidou R. , Steurer W.
Published: February 2008

Icosahedral band gap materials (BGMs) optimally combine the distinct band gaps of periodic BGMs with the high rotational symmetry of quasiperiodic structures. This is shown experimentally for longitudinal and transverse polarized elastic waves in a phononic crystal based on the three-dimensional Penrose tiling (3D-PT) and applies equally to photonic crystals. The ability of icosahedral BGMs to form Bragg-type band gaps follows from the similarity between the 3D-PT and the face-centered cubic structure (its periodic average structure). The 3D quasiperiodic BGM lacks bands of strong transmission like random or disordered BGMs but shows clear band gaps like periodic BGMs do.
Intense-laser generated relativistic electron transport in coaxial two-layer targets
Authors: Zhou C. T. , He X. T. , Yu M. Y.
Published: February 2008

The transport and heating of laser produced relativistic electron beam propagating through coaxial two-layer solid-density plasma are studied using two-dimensional hybrid fluid-particle-in-cell simulation. When the energetic electrons enter the plastic and copper target, stronger heating is observed in the plastic plasma. The heating of the plasma electrons and the formation of tens of million Gauss interface magnetic fields results from a large difference of the velocities of the returning electrons at the two sides of the interface. Moreover, the electron beam can have a completely different emittance behavior when the target consists of different-material layers.
Giant room-temperature magnetocaloric effect in Mn1−xCrxAs
Authors: Sun N. K. , Cui W. B. , Li D. , Geng D. Y. , Yang F. , Zhang Z. D.
Published: February 2008

A giant magnetocaloric effect was observed at room temperature in Mn1−xCrxAs compounds with x=0.006 and 0.01. The Cr dopant reduces (or even eliminates) the large thermal hysteresis of MnAs, while it lowers the first-order transition temperature from 313K for MnAs to 265K for Mn0.99Cr0.01As. Near the Curie temperature, a magnetic field induces a first-order phase transition from a ferromagnetic hexagonal phase to a paramagnetic orthorhombic phase, leading to a maximum value of ΔSM of 20.2J∕kgK at 267K for a 5T field change for Mn0.99Cr0.01As. The study on the Mn1−xCrxAs system may open an important field in searching proper materials for room-temperature magnetic refrigeration.
Quality and potential utility of ENSO-based forecasts of spring rainfall and wheat yield in south-eastern Australia
Authors: Anwar M. R. , Rodriguez D. , Liu D. L. , Power S. , O'Leary G. J.
Published: February 2008

Reliable seasonal climate forecasts are needed to aid tactical crop management decisions in south-eastern Australia (SEA). In this study we assessed the quality of two existing forecasting systems, i.e. the five phases of the Southern Oscillation Index (SOI) and a three phase Pacific Ocean sea-surface temperatures (SSTs), to predict spring rainfall (i.e. rainfall from 1 September to 31 November), and simulated wheat yield. The quality of the forecasts was evaluated by analysing four attributes of their performance: their reliability, the relative degree of shift and dispersion of the distributions, and measure of forecast consistency or skill. Available data included 117 years of spring rainfall and 104 years of grain yield simulated using the Agricultural Production Systems Simulator (APSIM) model, from four locations in SEA. Average values of spring rainfall were 102–174 mm with a coefficient of variation (CV) of 47%. Average simulated wheat yields were highest (5609 kg/ha) in Albury (New South Wales) and lowest (1668 kg/ha) in Birchip (Victoria). The average CV for simulated grain yields was 36%. Griffith (NSW) had the highest yield variability (CV = 50%). Some of this year-to-year variation was related to the El Niño Southern Oscillation (ENSO). Spring rainfall and simulated wheat yields showed a clear association with the SOI and SST phases at the end of July. Important variations in shift and dispersion in spring rainfall and simulated wheat yields were observed across the studied locations. The forecasts showed good reliability, indicating that both forecasting systems could be used with confidence to forecast spring rainfall or wheat yield as early as the end of July. The consistency of the forecast of spring rainfall and simulated wheat yield was 60–83%. We concluded that adequate forecasts of spring rainfall and grain yield could be produced at the end of July, using both the SOI and SST phase systems. These results are discussed in relation to the potential benefit of making tactical top-dress applications of nitrogen fertilisers during early August.
Effect of culture medium, genotype, and year of cross on embryo development and recovery from in vitro cultured ovules in breeding stenospermocarpic seedless grape varieties
Authors: Liu S. M. , Sykes S. R. , Clingeleffer P. R.
Published: February 2008

A highly efficient embryo rescue technique using in ovulo culture is critical for maximising success when using stenospermocarpic female parents to breed new seedless grape varieties. The effects of medium composition, pollen parent, and year of cross on embryo development and recovery in cultured ovules were investigated to improve in ovulo embryo rescue from stenospermocarpic parents commonly used in breeding seedless grapes for the Australian table and dried grape industries. Increasing CaCl2 concentrations in the culture medium improved embryo recovery, but embryo emergence from ovules and germination rates were unaffected by varying FeEDTA concentrations. A casein hydrolysate supplement in the culture medium improved embryo recovery, emergence, and germination. Embryo recovery varied with parental genotype and ranged from 5% to 14% in 4 self-pollinated genotypes. Mean embryo recoveries from ovules cultured 50 days after controlled cross-pollination from berries of the pollen-sterile, stenospermocarpic variety ‘Carina’ were 36% and 26% where the pollen parents were seeded (11 crosses) and seedless (6 crosses), respectively. Embryo recovery and germination were affected by the year in which a cross was made and there was a significant cross × year interaction. The results indicated that in ovulo embryo rescue can be improved by increasing CaCl2 concentrations and incorporating a casein hydrolysate supplement in the basal medium, by exploiting genotypic differences through the use of seedless parents that yield greater proportions of rescued hybrids, and possibly by understanding environmental effects on female parents to maximise the numbers of hybrids produced.
The influences of genotype, environment, and genotype×environment interaction on wheat quality
Authors: Williams R. M. , O'Brien L. , Eagles H. A. , Solah V. A. , Jayasena V.
Published: February 2008

Knowledge of the relative contributions of genotype (G), environment (E), and genotype and environment interaction (G × E) effects on wheat (Triticum aestivum L.) quality leads to more effective selection in breeding programs and segregation of more uniform parcels of grain better suited to the needs of customers. Their effects on wheat quality were reviewed using papers obtained from 4 major international databases. The literature is dominated by research from North America, with lesser contributions from Europe, Australia, and the rest of the world. Use of analysis of variance to partition sources of variation due to G, E, and G × E was the most common approach but, more recently, residual maximum likelihood methods that can accommodate large, but unbalanced, datasets have been used. In North America and Europe, the relative contributions of G, E, and G × E varied across studies, but traits associated with protein content were more influenced by E and G × E than those associated with protein quality, dough rheology and starch characteristics, where G effects were more important. Variation in the relative contributions of G, E, and G × E was highly dependent on the G and E sampled. The Australian studies were characterised by a relative lack of G × E, with G and E rankings being similar across the country for the protein quality, dough rheology, and starch quality traits examined in detail. This suggests that, in Australia, more efficient testing of potential cultivars will be possible for these traits, especially when the underlying variation at the gene level is known, and that efficiencies in the design and conduct of trial systems and quality evaluations could be achieved by testing samples from targetted environments without affecting genetic gain and overall crop quality.
Reanalyses of Gulf of Mexico fisheries data: Landings can be misleading in assessments of fisheries and fisheries ecosystems
Authors: de Mutsert Kim , Cowan James H. , Essington Timothy E. , Hilborn Ray
Published: February 2008

We used two high profile articles as cases to demonstrate that use of fishery landings data can lead to faulty interpretations about the condition of fishery ecosystems. One case uses the mean trophic level index and its changes, and the other uses estimates of fishery collapses. In earlier analyses by other authors, marine ecosystems in the Gulf of Mexico (GOM) and U.S. Atlantic Ocean south of Chesapeake Bay were deemed to be severely overfished and the food webs badly deteriorated using these criteria. In our reanalyses, the low mean trophic level index for the GOM actually resulted from large catches of two groups of low trophic level species, menhaden and shrimp, and the mean trophic level was slowly increasing rather than decreasing. Commercial targeting and high landings of shrimps and menhaden, especially in the GOM, drove the index as previously calculated. Reanalyses of fishery collapses incorporating criteria that included targeting, variability in fishing effort, and market forces discovered many false cases of collapse based simply upon a decline of catches to 10% of previous maximum levels. Consequently, we suggest that the low mean trophic level index calculated in the earlier article for the GOM did not reflect the overall condition of the fishery ecosystem, and that the 10% rule for collapse should not be interpreted out of context in the GOM or elsewhere. In both cases, problems lay in the assumption that commercial landings data alone adequately reflect the fish populations and communities.
Gating at the selectivity filter in cyclic nucleotide-gated channels
Authors: Contreras Jorge E. , Srikumar Deepa , Holmgren Miguel
Published: February 2008

By opening and closing the permeation pathway (gating) in response to cGMP binding, cyclic nucleotide-gated (CNG) channels serve key roles in the transduction of visual and olfactory signals. Compiling evidence suggests that the activation gate in CNG channels is not located at the intracellular end of pore, as it has been established for voltage-activated potassium (K
V
) channels. Here, we show that ion permeation in CNG channels is tightly regulated at the selectivity filter. By scanning the entire selectivity filter using small cysteine reagents, like cadmium and silver, we observed a state-dependent accessibility pattern consistent with gated access at the middle of the selectivity filter, likely at the corresponding position known to regulate structural changes in KcsA channels in response to low concentrations of permeant ions.
Arterial calcifications and increased expression of vitamin D receptor targets in mice lacking TIF1α
Authors: Ignat Mihaela , Teletin Marius , Tisserand Johan , Khetchoumian Konstantin , Dennefeld Christine , Chambon Pierre , Losson Régine , Mark Manuel
Published: February 2008

Calcification of arteries is a major risk factor for cardiovascular mortality in humans. Using genetic approaches, we demonstrate here that the transcriptional intermediary factor 1α (TIF1α), recently shown to function as a tumor suppressor in murine hepatocytes, also participates in a molecular cascade that prevents calcifications in arterioles and medium-sized arteries. We further provide genetic evidence that this function of TIF1α is not exerted in hepatocytes. The sites of ectopic calcifications in mutant mice lacking TIF1α resemble those seen in mice carrying an activating mutation of the calcium sensor receptor (
Casr
) gene and, in
TIF1
α-deficient kidneys,
Casr
expression is increased together with that of many other vitamin D receptor (VDR) direct target genes, namely
Car2
,
Cyp24a1
,
Trpv5
,
Trpv6
,
Calb1
,
S100g
,
Pthlh
, and
Spp1
. Thus, our data indicate that TIF1α represses the VDR pathway in kidney and suggest that an up-regulation of
Casr
expression in this organ could account for ectopic calcifications generated upon
TIF1
α deficiency. Interestingly, the calcifying arteriopathy of
TIF1
α-null mutant mice shares features with the human age-related Mönckeberg's disease and, overall, the
TIF1
α-null mutant pathological phenotype supports the hypothesis that aging is promoted by increased activity of the vitamin D signaling pathway.
A biodegradable and biocompatible gecko-inspired tissue adhesive
Authors: Mahdavi Alborz , Ferreira Lino , Sundback Cathryn , Nichol Jason W. , Chan Edwin P. , Carter David J. D. , Bettinger Chris J. , Patanavanich Siamrut , Chignozha Loice , Ben-Joseph Eli , Galakatos Alex , Pryor Howard , Pomerantseva Irina , Masiakos Peter T. , Faquin William , Zumbuehl Andreas , Hong Seungpyo , Borenstein Jeffrey , Vacanti Joseph , Langer Robert , Karp Jeffrey M.
Published: February 2008

There is a significant medical need for tough biodegradable polymer adhesives that can adapt to or recover from various mechanical deformations while remaining strongly attached to the underlying tissue. We approached this problem by using a polymer poly(glycerol-co-sebacate acrylate) and modifying the surface to mimic the nanotopography of gecko feet, which allows attachment to vertical surfaces. Translation of existing gecko-inspired adhesives for medical applications is complex, as multiple parameters must be optimized, including: biocompatibility, biodegradation, strong adhesive tissue bonding, as well as compliance and conformability to tissue surfaces. Ideally these adhesives would also have the ability to deliver drugs or growth factors to promote healing. As a first demonstration, we have created a gecko-inspired tissue adhesive from a biocompatible and biodegradable elastomer combined with a thin tissue-reactive biocompatible surface coating. Tissue adhesion was optimized by varying dimensions of the nanoscale pillars, including the ratio of tip diameter to pitch and the ratio of tip diameter to base diameter. Coating these nanomolded pillars of biodegradable elastomers with a thin layer of oxidized dextran significantly increased the interfacial adhesion strength on porcine intestine tissue
in vitro
and in the rat abdominal subfascial
in vivo
environment. This gecko-inspired medical adhesive may have potential applications for sealing wounds and for replacement or augmentation of sutures or staples.
Splicing promotes rapid and efficient mRNA export in mammalian cells
Authors: Valencia Patricia , Dias Anusha P. , Reed Robin
Published: February 2008

The numerous steps in protein gene expression are extensively coupled to one another through complex networks of physical and functional interactions. Indeed, >25 coupled reactions, often reciprocal, have been documented among such steps as transcription, capping, splicing, and polyadenylation. Coupling is usually not essential for gene expression, but instead enhances the rate and/or efficiency of reactions and, physiologically, may serve to increase the fidelity of gene expression. Despite numerous examples of coupling in gene expression, whether splicing enhances mRNA export still remains controversial. Although splicing was originally reported to promote export in both mammalian cells and
Xenopus
oocytes, it was subsequently concluded that this was not the case. These newer conclusions were surprising in light of the observations that the mRNA export machinery colocalizes with splicing factors in the nucleus and that splicing promotes recruitment of the export machinery to mRNA. We therefore reexamined the relationship between splicing and mRNA export in mammalian cells by using FISH, in combination with either transfection or nuclear microinjection of plasmid DNA. Together, these analyses indicate that both the kinetics and efficiency of mRNA export are enhanced 6- to 10-fold (depending on the construct) for spliced mRNAs relative to their cDNA counterparts. We conclude that splicing promotes mRNA export in mammalian cells and that the functional coupling between splicing and mRNA export is a conserved and general feature of gene expression in higher eukaryotes.
The Big Squeeze
Authors: Lucas Edward
Published: February 2008

During Putin’s presidency, media freedom has moved from the imperfect to the moribund, writes Edward Lucas. The message is clear: keep quiet
Phoenix Rising
Authors: Maryniak Irena
Published: February 2008

In a face-off with the West, Russia is rebranding its image – spinning the present as the latest chapter in a triumphant, grand narrative, reports Irena Maryniak
Development and preliminary validation of a measure for assessing staff perspectives on the quality of clinical group supervision
Authors: Horton Simon , de Lourdes Drachler Maria , Fuller Alison , de Carvalho Leite Jose Carlos
Published: February 2008

Background: In the UK clinical supervision is regarded as an essential process supporting quality improvement within the clinical governance framework, and the Royal College of Speech and Language Therapists regards it as a tool for promoting critical reflective practice. There is limited evidence of the impact on practice or improvements in healthcare quality, and the need for an evaluation instrument specifically tailored to group supervision.

Aims: To develop a measure for assessing staff perspectives on the quality of clinical group supervision and its impact on the quality of care.

Methods & Procedures: A self‐completion questionnaire was devised to measure staff perceptions of purpose, process and impact of clinical group supervision. Items were developed through an inductive process of consultation, peer and literature review. The questionnaire's content validity was assessed. The questionnaire was then administered to 57 subjects who had received approximately 1 year of clinical supervision to evaluate acceptability, factor structure and convergent validity.

Outcomes & Results: Response rates were 91% (52/57). Principal component factor analysis suggested a three‐factor structure, the first three factors accounting for 72.4% of the total variance. Items loaded appropriately onto purpose, process and impact. These three dimensions were positively and moderately correlated. Internal consistency reliability (Cronbach's alpha = 0.86) indicated that the 14 items could be regarded as a scale. The overall CSEQ score was positively correlated with a single question assessing ‘general opinion’ about the CS program (Spearman's rho = 0.79, p<0.001) giving evidence for convergent validity.

Conclusions: The questionnaire is concise, easy to complete and simple to analyse, and appears to be a reliable and valid measure of staff perceptions of quality of clinical group supervision. Further studies with larger sample sizes and including other groups of health professionals are needed to confirm the validity and reliability of the CSEQ.
Comparing language profiles: children with specific language impairment and developmental coordination disorder
Authors: Archibald Lisa M. D. , Alloway Tracy Packiam
Published: February 2008

Background: Although it is widely recognized that substantial heterogeneity exists in the cognitive profiles of children with Developmental Coordination Disorder (DCD), very little is known about the language skills of this group.

Aims: To compare the language abilities of children with DCD with a group whose language impairment has been well described: children with Specific Language Impairment (SLI).

Methods & Procedures: Eleven children with DCD and 11 with SLI completed standardized and non‐standardized assessments of vocabulary, grammatical skill, non‐word repetition, sentence recall, story retelling, and articulation rate. Performance on the non‐standardized measures was compared with a group of typically developing children of the same age.

Outcomes & Results: Children with DCD were impaired on tasks involving verbal recall and story retelling. Almost half of those in the DCD group performed similarly to the children with SLI over several expressive language measures, while 18% had deficits in non‐word repetition and story retelling only. Poor non‐word repetition was observed for both the DCD and the SLI groups. The articulation rate of the children with SLI was slower than that of the DCD group, which was slower than that of typically developing children.

Conclusions: Language impairment is a common co‐occurring condition in DCD. The language profile of children with either DCD or SLI was similar in the majority of, but not all, cases.