bluuebunny/crossref_metadata_2025 huggingface dataset:
Rheological study of polymer flow past rough surfaces with slip boundary conditions
Authors: Niavarani Anoosheh , Priezjev Nikolai V.
Published: October 2008

The slip phenomena in thin polymer films confined by either flat or periodically corrugated surfaces are investigated by molecular dynamics and continuum simulations. For atomically flat surfaces and weak wall-fluid interactions, the shear rate dependence of the slip length has a distinct local minimum which is followed by a rapid increase at higher shear rates. For corrugated surfaces with wavelength larger than the radius of gyration of polymer chains, the effective slip length decays monotonically with increasing corrugation amplitude. At small amplitudes, this decay is reproduced accurately by the numerical solution of the Stokes equation with constant and rate-dependent local slip length. When the corrugation wavelength is comparable to the radius of gyration, the continuum predictions overestimate the effective slip length obtained from molecular dynamics simulations. The analysis of the conformational properties indicates that polymer chains tend to stretch in the direction of shear flow above the crests of the wavy surface.
Unitary isomorphism of Fock spaces of bosons and fermions arising from a representation of the Cuntz algebra O2
Authors: Kawamura Katsunori
Published: October 2008

Bosons and fermions are described by using canonical generators of Cuntz algebras on any permutative representation. According to branching laws associated with these descriptions, a certain representation of the Cuntz algebra O2 induces Fock representations HB and HF of bosons and fermions simultaneously. From this, a unitary operator U from HB to HF is obtained. We show the explicit formula of the action of U on the standard basis of HB. It is shown that U preserves the particle number of HB and HF.
Magnetic detection of high-resolution electron spin resonance using a microcantilever in the millimeter-wave region up to 240 GHz
Authors: Ohmichi E. , Mizuno N. , Kimata M. , Ohta H.
Published: October 2008

Highly sensitive magnetic detection of electron spin resonance (ESR) using a microcantilever is presented. By combining a modulation technique with the use of a piezoresistive cantilever, we successfully observed ESR signals of a tiny single crystal (mass<1 μg) of Co Tutton salt, Co(NH4)2(SO4)2⋅6H2O, in the frequency region of 80–240 GHz. The achieved spin sensitivity was ∼109 spins/G at 4.5 K, providing promising applications to high-resolution and high-sensitivity terahertz ESR.
Vapor-liquid interfacial properties of fully flexible Lennard-Jones chains
Authors: Blas Felipe J. , MacDowell Luis G. , de Miguel Enrique , Jackson George
Published: October 2008

We consider the computation of the interfacial properties of molecular chains from direct simulation of the vapor-liquid interface. The molecules are modeled as fully flexible chains formed from tangentially bonded monomers with truncated Lennard-Jones interactions. Four different model systems comprising of 4, 8, 12, and 16 monomers per molecule are considered. The simulations are performed in the canonical ensemble, and the vapor-liquid interfacial tension is evaluated using the test area and the wandering interface methods. In addition to the surface tension, we also obtain density profiles, coexistence densities, critical temperature and density, and interfacial thickness as functions of temperature, paying particular attention to the effect of the chain length on these properties. According to our results, the main effect of increasing the chain length (at fixed temperature) is to sharpen the vapor-liquid interface and to increase the width of the biphasic coexistence region. As a result, the interfacial thickness decreases and the surface tension increases as the molecular chains get longer. The interfacial thickness and surface tension appear to exhibit an asymptotic limiting behavior for long chains. A similar behavior is also observed for the coexistence densities and critical properties. Our simulation results indicate that the asymptotic regime is reached for Lennard-Jones chains formed from eight monomer segments. We also include a preliminary study on the effect of the cutoff distance on the interfacial properties. Our results indicate that all of the properties exhibit a dependence with the distance at which the interactions are truncated, though the relative effect varies from one property to the other. The interfacial thickness and, more particularly, the interfacial tension are found to be strongly dependent on the particular choice of cutoff, whereas the density profiles and coexistence densities are, in general, less sensitive to the truncation.
Laser detection of spin-polarized hydrogen from HCl and HBr photodissociation: Comparison of H- and halogen-atom polarizations
Authors: Sofikitis Dimitris , Rubio-Lago Luis , Bougas Lykourgos , Alexander Andrew J. , Rakitzis T. Peter
Published: October 2008

Thermal HCl and HBr molecules were photodissociated using circularly polarized 193nm light, and the speed-dependent spin polarization of the H-atom photofragments was measured using polarized fluorescence at 121.6nm. Both polarization components, described by the a01(⊥) and Re[a11(∥,⊥)] parameters which arise from incoherent and coherent dissociation mechanisms, are measured. The values of the a01(⊥) parameter, for both HCl and HBr photodissociation, are within experimental error of the predictions of both ab initio calculations and of previous measurements of the polarization of the halide cofragments. The experimental and ab initio theoretical values of the Re[a11(∥,⊥)] parameter show some disagreement, suggesting that further theoretical investigations are required. Overall, good agreement occurs despite the fact that the current experiments photodissociate molecules at 295K, whereas previous measurements were conducted at rotational temperatures of about 15K.
Ion correlation forces between uncharged dielectric walls
Authors: Wernersson Erik , Kjellander Roland
Published: October 2008

The interaction pressure between two uncharged planar walls immersed in various electrolyte solutions containing mono- and/or divalent ions is investigated. The solution is treated as a primitive model electrolyte, and the wall surfaces constitute dielectric discontinuities. Ionic image charge and ion-wall dispersion interactions are included. The interaction parameters are appropriate for hydrocarbon (polystyrene)/water interfaces, and the electrolyte concentrations considered lie between 0.250M and 1.00M. The anisotropic hypernetted chain method is used to self-consistently calculate the ion density profiles and the ion-ion correlation functions in the inhomogeneous electrolyte. Thereby, the effects of image charge interactions and dispersion interactions on the pressure and the electrolyte structure are included in a fully consistent manner. The explicit consideration of correlations between the ions in the presence of image charges ensures that the screening of the zero-frequency van der Waals interaction is taken into account. Of special interest are the effects of asymmetries between anions and cations with respect to valency and/or dispersion interaction with the walls. Such asymmetries create an electric double layer in the electrolyte outside each electroneutral surface. This causes the wall-wall interaction for large surface separations to be similar to the interaction between charged surfaces. For intermediate separations, around 1–2 nm, a substantial repulsive peak appears in the ionic pressure. In some cases the repulsion is larger than the van der Waals attraction between the walls, which implies that there is a repulsive barrier in the total pressure despite that the surfaces are uncharged. The strongest repulsion is found for 2:1 electrolytes where the monovalent anions interact strongly with the walls via dispersion forces. In general, ion-wall dispersion forces acting on ions of lower valency have a much greater effect than equally strong dispersion forces acting on ions of higher valency. This is mainly due to the more strongly repulsive image charge forces on ions of higher valency that counteract the attractive dispersion forces. Effects of confinement on the ion-ion correlations also contribute to this difference. For all electrolytes the interaction pressure from the ions is attractive for small surface separations. The main cause is a depletion of ions between the walls from the self-image repulsion and confinement effects. For totally symmetric electrolytes the attractive pressure extends to large separations in most cases.
Nonlinear harmonic components in dielectric relaxation of polyelectrolytes
Authors: Déjardin Jean-Louis , Jadzyn Jan
Published: October 2008

The problem of the nonlinear ac dielectric response in polyelectrolytes is carried out by considering these electrically charged systems acted on by a strong dc bias electric field superimposed on a weak ac field. An infinite set of coupled (translation-rotation) kinetic equations is derived, and by using a perturbation procedure, we establish a new expression for the complex dielectric increment of an assembly of nonpolar rodlike macroions surrounded by small counterions. By considering the stationary regime, we show that the electric polarization of the nonpolar macroion is given by calculating the expectation value of P1(cos ϑ)H1(x), where P1 and H1 stand for the first Legendre and Hermite polynomials, respectively. The results so obtained provide new relaxation features, which are presented in the form of analytic expressions and illustrated by Cole-Cole-like diagrams and three-dimensional dispersion and absorption plots in order to show the influence of the coupling parameter a measuring the importance of the rotational motion over the translational one.
Density-gradient theory of tunneling: Physics and verification in one dimension
Authors: Ancona M. G. , Svizhenko A.
Published: October 2008

The application of an engineering-oriented continuum description of electron transport known as density-gradient theory to quantum mechanical tunneling is investigated, and its legitimacy, physical fidelity, and limitations are assessed using detailed comparisons with nonequilibrium Green’s function simulations in one dimension. These comparisons demonstrate that despite the apparent contradiction, quantum tunneling can often be well represented by the classical field theory with the electron inertia term of Newton’s second law playing a significant role. Moreover, the density-gradient approach is found to be quite accurate with the main source of error not being the description of the tunneling itself, but rather the representation of the carriers at high density inside the electrodes. A physical understanding of the ad hoc tunneling boundary conditions used in previous work is also provided.
Surface recombination in ZnO nanorods grown by chemical bath deposition
Authors: Zhao Q. X. , Yang L. L. , Willander M. , Sernelius B. E. , Holtz P. O.
Published: October 2008

Vertically well-aligned ZnO nanorods on Si substrates were prepared by a two-step chemical bath deposition (CBD) method. The optical properties of the grown ZnO nanorods were investigated by time resolved photoluminescence spectroscopy. It was found that the effective decay time of the near bandgap recombination in the CBD grown ZnO nanorods strongly depends on the diameter of the ZnO nanorods. Typically, the decay curves obtained from these ZnO nanorods show a combination of two exponential decays. The experimental results show that the fast exponential decay is related to the surface recombination and the slow decay is related to the “bulk” decay. The measured decay time of the effective surface recombination decreases with decreasing diameter, while the bulk decay time remains unchanged. The results also show that an annealing treatment around 500 °C significantly reduces the surface recombination rate. A simple carrier and exciton diffusion equation is also used to determine the surface recombination velocity, which results in a value between 1.5 and 4.5 nm/ps.
First-principles study of p-type transparent conductive oxides CuXO2 (X=Y, Sc, and Al)
Authors: Shi Li-Jie , Fang Zhi-Jie , Li Jingbo
Published: October 2008

Using first-principles methods we have calculated electronic structures, optical properties, and hole conductivities of CuXO2 (X=Y, Sc, and Al). We show that the direct optical band gaps of CuYO2 and CuScO2 are approximately equal to their fundamental band gaps and the conduction bands of them are localized. The direct optical band gaps of CuXO2 (X=Y, Sc, and Al) are 3.3, 3.6, and 3.2 eV, respectively, which are consistent with experimental values of 3.5, 3.7, and 3.5 eV. We find that the hole mobility along long lattice c is higher than that along other directions through calculating effective masses of the three oxides. By analyzing band offset we find that CuScO2 has the highest valence band maximum (VBM) among CuXO2 (X=Y, Sc, and Al). In addition, the approximate transitivity of band offset suggests that CuScO2 has a higher VBM than CuGaO2 and CuInO2 [Phys. Rev. Lett. 88, 066405 (2002)]. We conclude that CuScO2 has a higher p-type doping ability in terms of the doping limit rule.
A magnetometry study of Co oxidation in Co/MgO bilayers grown by sputtering
Authors: Lu Y. , Deranlot C. , Vaurès A. , Petroff F. , George J-M.
Published: October 2008

One of the critical challenges during fabrication of magnetic tunnel junctions is to avoid the magnetic bottom electrode oxidation, considered as a spin depolarization source that lowers the tunneling magnetoresistance effect. In this paper, we present a study of the magnetic properties of Co/MgO bilayers as a function of several sputtering growth parameters by using a superconducting quantum interference device magnetometer. We demonstrate the high sensitivity of the magnetic properties to the oxidation of the Co layer and identify the relevant parameters to optimize the MgO growth process.
Characterization of borate glasses by W-band pulse electron-nuclear double resonance spectroscopy
Authors: Kordas George , Goldfarb Daniella
Published: October 2008

( 100 − x ) mol %  B2O3 x mol % Me2O (Me=Li,Na,K) glasses, exposed to γ-Co60 irradiation to produce paramagnetic states, were characterized by W-band (95GHz) pulse electron-nuclear double resonance (ENDOR) spectroscopy in order to characterize local structures occurring in the range of compositions between x=16 and x=25 at which the “boron oxide” anomaly occurs. The high resolution of nuclear frequencies allowed resolving the Li7 and B11 ENDOR lines. In the samples with x=16 and x=20 glasses, B11 hyperfine couplings of 16, 24, and 36MHz were observed and attributed to the tetraborate, triborate, and boron oxygen hole center (BOHC) structures, respectively. The x=25 samples showed hyperfine couplings of 15MHz for the tetraborate and 36MHz for BOHC. Density functional theory (DFT) calculations predicted for these structures negative hyperfine couplings, which were confirmed by W-band ENDOR. This suggests that a spin polarization mechanism accounts for the negative hyperfine structure splitting.
Solution of the Percus–Yevick equation for hard hyperspheres in even dimensions
Authors: Adda-Bedia M. , Katzav E. , Vella D.
Published: October 2008

We solve the Percus–Yevick equation in even dimensions by reducing it to a set of simple integrodifferential equations. This work generalizes an approach we developed previously for hard disks. We numerically obtain both the pair correlation function and the virial coefficients for a fluid of hyperspheres in dimensions d=4, 6, and 8, and find good agreement with the available exact results and Monte Carlo simulations. This paper confirms the alternating character of the virial series for d≥6 and provides the first evidence for an alternating character for d=4. Moreover, we show that this sign alternation is due to the existence of a branch point on the negative real axis. It is this branch point that determines the radius of convergence of the virial series, whose value we determine explicitly for d=4, 6, 8. Our results complement, and are consistent with, a recent study in odd dimensions [R. D. Rohrmann et al., J. Chem. Phys. 129, 014510 (2008)].
A molecular dynamics study of the phase transition in bcc metal nanoparticles
Authors: Shibuta Yasushi , Suzuki Toshio
Published: October 2008

The phase transition between liquid and solid phases in body-centered cubic (bcc) metal nanoparticles of iron, chromium, molybdenum, and tungsten with size ranging from 2000 to 31250 atoms was investigated using a molecular dynamics simulation. The nucleation from an undercooled liquid droplet was observed during cooling in all nanoparticles considered. It was found that a nucleus was generated near one side of the particle and solidification spread toward the other side the during nucleation process. On the other hand, the surface melting and subsequent inward melting of the solid core of the nanoparticles were observed during heating. The depression of the melting point was proportional to the inverse of the particle radius due to the Gibbs–Thomson effect. On the other hand, the depression of the nucleation temperature during cooling was not monotonic with respect to the particle radius since the nucleation from an undercooled liquid depends on the event probability of an embryo or a nucleus.
Mode conversion of nonaxisymmetric modes in strongly nonuniform helicon-sustained plasma
Authors: Aliev Yu. M. , Krämer M.
Published: October 2008

The oblique wave propagation in helicon-sustained plasma accounting for the effect of the radial electron density gradient is investigated. It is shown that the conditions for the conversion of electrostatic and electromagnetic modes may change drastically in strongly nonuniform helicon plasma due to modification of the wave dispersion branches. Furthermore, the densities at which mode conversion occurs can be considerably lower if the density gradient is steep enough. This result contrasts with the common mode conversion theory neglecting density gradient effects and predicting mode conversion in the central plasma region at very high electron densities.
The scaling of forced collisionless reconnection
Authors: Sullivan Brian P. , Rogers Barrett N.
Published: October 2008

This paper presents two-fluid simulations of forced magnetic reconnection with finite electron inertia in a collisionless three-dimensional (3D) cube with periodic boundaries in all three directions. Comparisons are made to analogous two-dimensional (2D) simulations. Reconnection in this system is driven by a spatially localized forcing function that is added to the ion momentum equation inside the computational domain. Consistent with previous results in similar, but larger forced 2D simulations [B. Sullivan, B. N. Rogers, and M. A. Shay, Phys. Plasmas 12, 122312 (2005)], for sufficiently strong forcing the reconnection process is found to become Alfvénic in both 2D and 3D, i.e., the inflow velocity scales roughly like some fraction of the Alfvén speed based on the upstream reconnecting magnetic field, and the system takes on a stable configuration with a dissipation region aspect ratio on the order of 0.15.
Analytic integrability of a Chua system
Authors: Llibre Jaume , Valls Clàudia
Published: October 2008

We consider the system ẋ=a(z−a1x3−a2x2−bx), ẏ=−z, ż=−b1x+y+b2z, where a and b are parameters and b1=7/10, b2=6/25, a1=44/3, and a2=41/2. We analyze the existence of local and global analytic first integrals.
Full quantum vibrational simulation of the relaxation of the cyanide ion in water using the Ehrenfest method with quantum corrections
Authors: Bastida Adolfo , Zúñiga José , Requena Alberto , Miguel Beatriz
Published: October 2008

The Ehrenfest method with quantum corrections is used to describe the vibrational relaxation of the cyanide ion in liquid water. All the vibrational degrees of freedom of the system are described using quantum mechanics, including the normal modes of each individual solvent water molecule. The remaining translational and rotational degrees of freedom are described classically. Two different relaxation pathways are identified, one V-V and another V-TR. The V-V pathway involves the participation of the bending mode of the water molecules. This pathway is the fastest (T1(a)∼20 ps) and is also the most important, accounting for ∼82% of the relaxation process. The other V-TR relaxation pathway involves the direct transfer of the CN− vibrational quantum to the rotational and translational motions of the solvent and is significantly slower (T1(b)∼180 ps). The agreement with the experimental measurements is shown to be excellent.
On the UV responsivity of neutron irradiated 4H-SiC
Authors: Cavallini Anna , Castaldini Antonio , Nava Filippo
Published: October 2008

We report on UV responsivity of 4H-SiC photodiodes irradiated by 1 MeV neutrons. Current-voltage characteristics, photoresponse spectra, and responsivity were obtained with light wavelength from 200 to 450 nm. Photoresponse results slightly affected by irradiation up to the threshold fluence Φcritical=8×1014 cm−2. At fluences ≥Φcritical the rejection rate is in the order of 103 in the range of 200–320 nm while it is less than 102 at about 320 nm. The abrupt increase in midgap traps induced by irradiation at Φcritical, observed by photoinduced current transient spectroscopy, proves carrier generation/trapping to be the controlling mechanism for the responsivity.
Visible red random lasing in Y2O3:Eu3+/ZnO polycrystalline thin films by energy transfer from ZnO films to Eu3+
Authors: Chong M. K. , Abiyasa A. P. , Pita K. , Yu S. F.
Published: October 2008

Visible red random lasing centered at ∼611 nm has been observed in Y2O3:Eu3+/ZnO films at room temperature. Using a 355 nm laser source to excite the ZnO films, ultraviolet (UV) random lasing has been observed. The UV lasing spectrum can be tuned to overlap strongly with the F70-L56 excitation spectrum of Eu3+ ions centered at ∼394 nm by controlling the pump power, leading to very efficient radiative energy transfer from the ZnO films to Eu3+ ions. As a result, a red random lasing centered at ∼611 nm corresponding to the D50-F72 transition of Eu3+ ions was observed.
Dynamic switching behavior of bistable chiral-tilted homeotropic nematic liquid crystal displays
Authors: Liang Bau-Jy , Hsu Jy-Shan , Lin Che-Li , Hsu Wei-Chih
Published: October 2008

This investigation elucidates the transient behavior associated with switching between two stable states of a bistable chiral-tilted homeotropic nematic liquid crystal device. Experimental results reveal that the applied pulse voltages and durations not only determine the final states but are interestingly related to the relaxation time. When a suitable pulse voltage is applied, the minimum relaxation time can be obtained by adjusting the pulse duration. Analyzing the hydrodynamic behavior of the liquid crystal directors explicates the switching mechanism and relaxation processes. The principles that underlie the design of the waveforms to have the minimum relaxation time are obtained.
One- and biphotonic reorientational nonlinearities in dye-doped nematic and cholesteric liquid crystals
Authors: Yeh H.-C. , Lin H.-C. , Mo T.-S. , Fuh Andy Y.-G. , Huang S.-Y. , Lee C.-R.
Published: October 2008

This investigation elucidates one- and biphotonic reorientational nonlinearities in dye-doped nematic liquid crystals (DDNLCs) and dye-doped cholesteric liquid crystals (DDCLCs) using the Z-scan technique. Three cases—DDNLCs stimulated by one green beam polarized linearly parallel and perpendicular to the LC director and DDCLCs stimulated by one circularly polarized green beam—are considered without and with simultaneous stimulation by one linearly polarized red beam. Green-beam-induced dye reorientation through trans-cis isomerization and red-beam-induced suppression of dye reorientation by cis-trans back isomerization are responsible for the one- and biphotonic nonlinearities, respectively. The nonlinear refractive indices obtained herein are two orders of magnitude larger than those obtained elsewhere [Fuh et al., Opt. Exp. 13, 10634 (2005)]. The induced biphotonic nonlinearities can be modulated by controlling the intensity of the red beam in different ways due to the difference among the capabilities of the red beam to suppress the reorientation of the dyes and LCs in the three cases.
Investigation of correlation between the microstructure and electrical properties of sol-gel derived ZnO based thin films
Authors: Zhu M. W. , Gong J. , Sun C. , Xia J. H. , Jiang X.
Published: October 2008

Pure ZnO and aluminum doped ZnO films (ZAO) were prepared by sol-gel method and the effect of Al doping on the microstructure and electrical properties of the films was investigated. The results showed that the transformation from granular to columnar structure could be observed in pure ZnO films with the increase in heating time while in aluminum doped films little structural changes occurred even after a prolonged heating time. Additionally, measurements of electrical properties showed that both microstructural evolution and doping could significantly improve the conductivity of the films, which could be assigned to an increase both in Hall mobility and carrier concentration. The relationship between microstructure and the electrical properties of the films was discussed, and various scattering mechanisms were proposed for sol-gel derived ZnO and ZAO films as a function of the carrier concentration.
Excitation of the Alfvén eigenmodes by localized energetic ions in optimized stellarators
Authors: Marchenko V. S.
Published: October 2008

Growth rates of the core-localized toroidal Alfvén eigenmodes destabilized by the localized energetic ions in the quasi-omnigeneous stellarator are calculated. Estimates show that these growth rates are comparable with collisional damping rates on the localized electrons.
Quantum effects on the entanglement fidelity in elastic scatterings in strongly coupled semiclassical plasmas
Authors: Jung Young-Dae , Kato Daiji
Published: October 2008

The quantum effects on the entanglement fidelity in elastic electron-ion scatterings are investigated in strongly coupled semiclassical plasmas. The screened pseudopotential model and partial wave analysis are employed to obtain the entanglement fidelity in strongly coupled semiclassical plasmas as a function of the thermal de Broglie wavelength, Debye length, and projectile energy. It is shown that the quantum effect significantly enhances the entanglement fidelity in strongly coupled semiclassical plasmas. It is also found that the entanglement fidelity increases with increasing the projectile energy. In addition, it is shown that the plasma screening effect increases the entanglement fidelity slightly.
The reduced triplet-triplet annihilation of electrophosphorescent device doped by an iridium complex with active hydrogen
Authors: Han Liangliang , Yang Dongfang , Li Wenlian , Chu Bei , Chen Yiren , Su Zisheng , Zhang Dongyu , Yan Fei , Hu Zhizhi , Zhang Zhiqiang
Published: October 2008

We demonstrate high efficiency electrophosphorescent devices doped by bis(2-phenyl-benzoimidazole) iridium (III) acetylacetonate [Ir(ppi)2acac] with active hydrogen. At 100 mA/cm2 2 wt % Ir(ppi)2acac doped device offers an external quantum efficiency (ηext) of 5.1% and an efficiency roll-off of 28.2%, which decreases for 33.5% and 39.1% compared with that of 2 and 6 wt % fac-tris(2-phenylpyridine) iridium (III) [fac-Ir(ppy)3] doped reference devices, respectively. 7 wt % Ir(ppi)2acac doped device behaves a maximum ηext of 13.4% and a ηext of 8.0% at a luminance of 10 000 cd/m2. Both the ηext are higher than that of the reference device. The improvement in electroluminescent performance was assumed to be the very short triplet lifetime (3.74 ns) induced by the active hydrogen atom.
Effective polarization fatigue from repeated dielectric barrier discharges in cellular polypropylene ferroelectrets
Authors: Qiu Xunlin , Gerhard Reimund
Published: October 2008

Polarization fatigue is observed when cellular polypropylene (PP) ferroelectrets are subjected to high-voltage cycles. The fatigue rate strongly depends on the amplitude and the number of the applied voltage cycles, whereas the frequency and the waveform of the voltage do not have a strong influence. The much lower piezoelectric activity of significantly fatigued cellular PP ferroelectret films recovers in part after a storage period of typically several hours in ambient air. It is believed that the effective polarization fatigue is mainly caused by the plasma modification of the internal surfaces effected by the repeated dielectric barrier discharges inside the voids.
Thermal emittance changes at the charge ordering transition of (Sm0.35Ca0.65)MnO3
Authors: Laffez P. , Napierala C. , Zaghrioui M. , Ta Phuoc V. , Hassini A. , Ammar M. R.
Published: October 2008

The reversible charge ordering transition of (Sm1−x,Cax)MnO3 is associated with strong changes in electrical, magnetic, and infrared properties. In this work, normal spectral emissivity is calculated from infrared reflectance of bulk polished ceramics. Emissivity versus temperature shows a sharp variation at the charge ordering transition near room temperature. By comparing the apparent temperature of the sample with the absolute temperature, we show that Sm0.35Ca0.65MnO3 is a good candidate for infrared furtivity around room temperature.
Implementation scheme for quantum controlled phase-flip gate through quantum dot in slow-light photonic crystal waveguide
Authors: Gao Jie , Sun F. W. , Wong Chee Wei
Published: October 2008

We propose a scheme to realize controlled phase gate between two single photons through a single quantum dot in a slow-light photonic crystal waveguide. Enhanced Purcell factor and large β-factor lead to high gate fidelity over broadband frequencies compared to cavity-assisted system. The excellent physical integration of this photonic crystal waveguide system provides tremendous potential for large-scale quantum information processing.
High-throughput evaluation of domain switching in piezoelectric ceramics and application to PbZr0.6Ti0.4O3 doped with La and Fe
Authors: Jones Jacob L. , Pramanick Abhijit , Daniels John E.
Published: October 2008

A combinatorial material synthesis and characterization technique is introduced and demonstrated wherein the ferroelectric behavior of a compositionally graded bulk ceramic is investigated during electrical loading. Using combined high-energy x-ray microdiffraction and fluorescence spectroscopy, non-180° domain wall motion of different compositions is measured and quantified as a function of composition across the gradation. The greatest amount of non-180° domain wall motion is found in samples containing the highest measured fraction of La dopant (2mol%).
Propagation of exchange bias in CoFe∕FeMn∕CoFe trilayers
Authors: Nam D. N. H. , Chen W. , West K. G. , Kirkwood D. M. , Lu J. , Wolf S. A.
Published: October 2008

Co Fe ∕ Fe Mn , FeMn∕CoFe bilayers and CoFe∕FeMn∕CoFe trilayers were grown in magnetic field and at room temperature. The exchange bias field HEB depends strongly on the order of depositions and is much higher at CoFe∕FeMn than at FeMn∕CoFe interfaces. By combining the two bilayer structures into symmetric CoFe∕FeMn(tFeMn)∕CoFe trilayers, HEBt and HEBb of the top and bottom CoFe layers, respectively, are both enhanced. Reducing tFeMn of the trilayers also results in enhancements of both HEBb and HEBt. These results evidence the propagation of exchange bias between the two CoFe∕FeMn and FeMn∕CoFe interfaces mediated by the FeMn antiferromagnetic order.
Diagnosis of high-intensity pulsed heavy ion beam generated by a novel magnetically insulated diode with gas puff plasma gun
Authors: Ito H. , Miyake H. , Masugata K.
Published: October 2008

Intense pulsed heavy ion beam is expected to be applied to materials processing including surface modification and ion implantation. For those applications, it is very important to generate high-purity ion beams with various ion species. For this purpose, we have developed a new type of a magnetically insulated ion diode with an active ion source of a gas puff plasma gun. When the ion diode was operated at a diode voltage of about 190 kV, a diode current of about 15 kA, and a pulse duration of about 100 ns, the ion beam with an ion current density of 54 A/cm2 was obtained at 50 mm downstream from the anode. By evaluating the ion species and the energy spectrum of the ion beam via a Thomson parabola spectrometer, it was confirmed that the ion beam consists of nitrogen ions (N+ and N2+) of energy of 100–400 keV and the proton impurities of energy of 90–200 keV. The purity of the beam was evaluated to be 94%. The high-purity pulsed nitrogen ion beam was successfully obtained by the developed ion diode system.
On the embedding of space-time in five-dimensional Weyl spaces
Authors: Dahia F. , Gomez G. A. T. , Romero C.
Published: October 2008

We revisit Weyl geometry in the context of recent higher-dimensional theories of space-time. After introducing the Weyl theory in a modern geometrical language we present some results that represent extensions of Riemannian theorems. We consider the theory of local embeddings and submanifolds in the context of Weyl geometries and show how a Riemannian space-time may be locally and isometrically embedded in a Weyl bulk. We discuss the problem of classical confinement and the stability of motion of particles and photons in the neighborhood of branes for the case when the Weyl bulk has the geometry of a warped product space. We show how the confinement and stability properties of geodesics near the brane may be affected by the Weyl field. We construct a classical analog of quantum confinement inspired in theoretical-field models by considering a Weyl scalar field which depends only on the extra coordinate.
Strain induced changes in gate leakage current and dielectric constant of nitrided Hf-silicate metal oxide semiconductor capacitors
Authors: Son S. Y. , Choi Y. S. , Kumar P. , Park H. W. , Nishida T. , Singh R. K. , Thompson S. E.
Published: October 2008

Uniaxial-mechanical-stress altered gate leakage current and dielectric constant of silicon metal-oxide-semiconductor (MOS) devices with nitrided Hf-silicate (HfSiON) dielectric are measured as a function of uniaxial stress applied using four-point wafer bending along the [110] direction. The gate leakage current and dielectric constant are found to increase by ∼2% per 100MPa of tensile and compressive stresses. A decrease in hole trap activation energy in hafnium oxide-based dielectric is used to explain the mechanical stress altered gate leakage. It is proposed that the HfSiON dielectric constant increase results from band gap narrowing caused by strain induced N p band splitting.
Superconductivity at 27K in tetragonal FeSe under high pressure
Authors: Mizuguchi Yoshikazu , Tomioka Fumiaki , Tsuda Shunsuke , Yamaguchi Takahide , Takano Yoshihiko
Published: October 2008

A huge enhancement of the superconducting transition temperature Tc was observed in a tetragonal FeSe superconductor under high pressure. The onset temperature was as high as 27K at 1.48GPa and the pressure coefficient showed an extremely high value of 9.1K∕GPa. The upper critical field Hc2 was estimated to be ∼72T at 1.48GPa. Because of the high Hc2, the FeSe system can be applied to superconducting wire rods.
Characterization of Pt/multiferroic BiFeO3/(Ba,Sr)TiO3/Si stacks for nonvolatile memory applications
Authors: Yeh Chia-Shiu , Wu Jenn-Ming
Published: October 2008

The Pt/BiFeO3(BFO)/(Ba,Sr)TiO3(BST)/Si metal-ferroelectric-insulator/Si (MFIS) structures were fabricated by rf-magnetron sputtering. The electric properties of the BFO ferroelectric film with BST insulating buffer on Si substrates were investigated. BST demonstrates excellent insulating properties on Si substrates. The MFIS structure exhibits clockwise capacitance-voltage hysteresis loops due to the ferroelectric polarization of BFO. The maximum memory window of the MFIS is 3.86 V, which is a remarkable improvement in comparison with previously reported 0.8 V. Trapped charge and charge injection are found to initiate when the sweeping voltage is higher than 8 and 9 V, respectively.
Effects of hormonal growth promotants (HGP) on growth, carcass characteristics, the palatability of different muscles in the beef carcass and their interaction with aging
Authors: Thompson J. M. , McIntyre B. M. , Tudor G. D. , Pethick D. W. , Polkinghorne R. , Watson R.
Published: October 2008

Effects of hormonal growth promotant (HGP) implantation on liveweight, carcass and meat quality measurements were examined using 80 Angus yearling cattle. After entry to the feedlot, 40 steers and 40 heifers were implanted with Revalor-S (28 mg oestradiol and 140 mg trenbolone acetate) and Revalor-H (20 mg oestradiol, 200 mg trenbolone acetate), respectively. Cattle were slaughtered after 55 and 65 days on feed. Samples from the Mm. longissimus dorsi, biceps femoris (the cap and body portions), gluteus medius (the eye and D portions), infraspinatus and triceps brachii were prepared for sensory testing after aging for 5 and 21 days after slaughter. A total of 854 muscle samples were cooked by grill (601) or roast (253) methods and served to consumers using the Meat Standards Australia taste panel protocols.
When adjusted to the same initial liveweight, implantation with Revalor-H and Revalor-S resulted in a 4 and 7% increase in slaughter weight, respectively. Implantation resulted in an increased ossification score in steers (P < 0.05), but not in heifers. There was a significant interaction (P < 0.05) between HGP implantation and days aged for shear force. There was a small effect of HGP implants on compression (P < 0.05), but not on cook loss and intramuscular fat percentage. Muscles differed in their response to HGP implantation (P < 0.05) for tenderness, overall liking and palatability scores. Muscles also differed in their aging rates after slaughter (P < 0.05). The greatest response in sensory scores to HGP implantation was found in those muscles that had the highest aging rates. Possible mechanisms by which muscles differed in their response to HGP implantation are discussed.
Evolution of the Meat Standards Australia (MSA) beef grading system
Authors: Polkinghorne R. , Thompson J. M. , Watson R. , Gee A. , Porter M.
Published: October 2008

The Australian Beef Industry identified variable eating quality as a major contributor to declining beef consumption in the early 1990s and committed research funding to address the problem. The major issue was the ability to predict the eating quality of cooked beef before consumption. The Meat Standards Australia (MSA) program developed a consumer testing protocol, which led to MSA grading standards being defined by consumer score outcomes. Traditional carcass grading parameters proved to be of little value in predicting consumer outcomes. Instead a broader combination of factors forms the basis of an interactive prediction model that performs well.
The grading model has evolved from a fixed parameter ‘Pathway’ approach, to a computer model that predicts consumer scores for 135 ‘cut by cooking method’ combinations for each graded carcass. The body of research work conducted in evaluating critical control points and in developing the model predictions and interactions has involved several Australian research groups with strong support and involvement from the industry.
International perspective: characterisation of United States Department of Agriculture and Meat Standards Australia systems for assessing beef quality
Authors: Smith G. C. , Tatum J. D. , Belk K. E.
Published: October 2008

The intent, in this manuscript, is to characterise the United States Department of Agriculture (USDA) and Meat Standards Australia (MSA) systems for assessing beef quality and to describe the research evidence that supports the principles involved in grade application. USDA beef quality grading standards rely on carcass-trait-only assessments of approximate age of the animal at harvest and amount of intramuscular fat (as marbling) inside the muscles. USDA beef quality grading started 82 years ago. Then, as now, because no traceability system was in place, each animal’s history (exact age, feeding regimen, management practices, etc.) was incomplete; those who assigned quality grades used indicators of age (physiological maturity) and plane of nutrition (amount of marbling), and they do so still. Since 1926, research studies have identified a multitude of palatability-determining live-animal factors (e.g. genetics, use of hormonal growth promotants, high-energy diet finishing) and carcass-treatment factors (e.g. electrical stimulation, tenderstretch carcass suspension, postmortem aging) that cannot be incorporated into a carcass-trait-only quality assessment system. The USA beef industry has depended on development of more than 100 beef brands – some using palatability assurance critical control point plans, total quality management (TQM) philosophies, USDA certification and process verification programs, or combinations of live-animal factors, carcass-treatment factors and carcass-trait constraints – to further differentiate fresh beef products. The MSA grading system is a TQM grading approach that incorporates animal-specific traits (e.g. genetics, sex, age), control of certain pre-harvest and post-harvest processes in the beef chain, cut-specific quality differences and consumer preferences, into a beef pricing system. A unique aspect of the MSA grading system is that the grades are assigned to cuts or muscles, not carcasses; cuts or muscles from the same carcass are assigned individual (and in many cases, different) grades that reflect differences in expected eating quality performance among the various cuts of beef further adjusted to reflect the influence of cut or muscle aging and alternative cooking methods. The MSA grading system is still being modified and refined (using results of an extensive, ongoing consumer testing program), but it represents the best existing example of a TQM grading approach for improving beef quality and palatability. Research studies have shown that the accuracy of palatability-level prediction by use of the two systems – USDA quality grades for US customers and consumers and MSA grades for Australian customers and consumers – is sufficient to justify their continued use for beef quality assessment.
A PHD-Polycomb Repressive Complex 2 triggers the epigenetic silencing of
FLC
during vernalization
Authors: De Lucia Filomena , Crevillen Pedro , Jones Alexandra M. E. , Greb Thomas , Dean Caroline
Published: October 2008

Vernalization, the acceleration of flowering by winter, involves cold-induced epigenetic silencing of
Arabidopsis FLC
. This process has been shown to require conserved Polycomb Repressive Complex 2 (PRC2) components including the Su(z)12 homologue, VRN2, and two plant homeodomain (PHD) finger proteins, VRN5 and VIN3. However, the sequence of events leading to
FLC
repression was unclear. Here we show that, contrary to expectations, VRN2 associates throughout the
FLC
locus independently of cold. The vernalization-induced silencing is triggered by the cold-dependent association of the PHD finger protein VRN5 to a specific domain in
FLC
intron 1, and this association is dependent on the cold-induced PHD protein VIN3. In plants returned to warm conditions, VRN5 distribution changes, and it associates more broadly over
FLC
, coincident with significant increases in H3K27me3. Biochemical purification of a VRN5 complex showed that during prolonged cold a PHD-PRC2 complex forms composed of core PRC2 components (VRN2, SWINGER [an E(Z) HMTase homologue], FIE [an ESC homologue], MSI1 [p55 homologue]), and three related PHD finger proteins, VRN5, VIN3, and VEL1. The PHD-PRC2 activity increases H3K27me3 throughout the locus to levels sufficient for stable silencing.
Arabidopsis
PHD-PRC2 thus seems to act similarly to Pcl-PRC2 of
Drosophila
and PHF1-PRC2 of mammals. These data show
FLC
silencing involves changed composition and dynamic redistribution of Polycomb complexes at different stages of the vernalization process, a mechanism with greater parallels to Polycomb silencing of certain mammalian loci than the classic
Drosophila
Polycomb targets.
Molecular phylogeny of a newfound hantavirus in the Japanese shrew mole (
Urotrichus talpoides
)
Authors: Arai Satoru , Ohdachi Satoshi D. , Asakawa Mitsuhiko , Kang Hae Ji , Mocz Gabor , Arikawa Jiro , Okabe Nobuhiko , Yanagihara Richard
Published: October 2008

Recent molecular evidence of genetically distinct hantaviruses in shrews, captured in widely separated geographical regions, corroborates decades-old reports of hantavirus antigens in shrew tissues. Apart from challenging the conventional view that rodents are the principal reservoir hosts, the recently identified soricid-borne hantaviruses raise the possibility that other soricomorphs, notably talpids, similarly harbor hantaviruses. In analyzing RNA extracts from lung tissues of the Japanese shrew mole (
Urotrichus talpoides
), captured in Japan between February and April 2008, a hantavirus genome, designated Asama virus (ASAV), was detected by RT-PCR. Pairwise alignment and comparison of the S-, M-, and L-segment nucleotide and amino acid sequences indicated that ASAV was genetically more similar to hantaviruses harbored by shrews than by rodents. However, the predicted secondary structure of the ASAV nucleocapsid protein was similar to that of rodent- and shrew-borne hantaviruses, exhibiting the same coiled-coil helix at the amino terminus. Phylogenetic analyses, using the maximum-likelihood method and other algorithms, consistently placed ASAV with recently identified soricine shrew-borne hantaviruses, suggesting a possible host-switching event in the distant past. The discovery of a mole-borne hantavirus enlarges our concepts about the complex evolutionary history of hantaviruses.
The two Kabiye orthographies
Authors: Roberts David
Published: October 2008

Two orthographies have been developed for Kabiye, a Gur language spoken mainly in Togo. The first aim of this paper is to provide an accurate historical summary concerning their development, teasing out some of the sociolinguistic issues which led to their separate evolution. Following this, I present the results of a comparative analysis, based on a text sample. I demonstrate five major types of difference: level of representation (shallow or deep), degree of consistency, dialect choice, diacritical tone marking and word boundaries. For each of these I explain by what criteria each party arrived at its decisions.

Locally, I hope that this analysis will contribute to well-informed choices should the Kabiye orthography ever be rectified in the future. But beyond this, the Kabiye experience will be of interest to anyone developing orthographies in other languages. With access to a varied stock of case studies such as this one, we will be in a better position to refine the existing principles of orthography development which can then be applied cross-linguistically.
GSEA-SNP: applying gene set enrichment analysis to SNP data from genome-wide association studies
Authors: Holden Marit , Deng Shiwei , Wojnowski Leszek , Kulle Bettina
Published: October 2008

The power of genome-wide SNP association studies is limited, among others, by the large number of false positive test results. To provide a remedy, we combined SNP association analysis with the pathway-driven gene set enrichment analysis (GSEA), recently developed to facilitate handling of genome-wide gene expression data. The resulting GSEA-SNP method rests on the assumption that SNPs underlying a disease phenotype are enriched in genes constituting a signaling pathway or those with a common regulation. Besides improving power for association mapping, GSEA-SNP may facilitate the identification of disease-associated SNPs and pathways, as well as the understanding of the underlying biological mechanisms. GSEA-SNP may also help to identify markers with weak effects, undetectable in association studies without pathway consideration. The program is freely available and can be downloaded from our website.

Contact:  bkulle@medisin.uio.no

Supplementary information:  Supplementary data are available at Bioinformatics online.