bluuebunny/crossref_metadata_2025 huggingface dataset:
Loss of AMP-activated protein kinase α2 subunit in mouse β-cells impairs glucose-stimulated insulin secretion and inhibits their sensitivity to hypoglycaemia
Authors: Beall Craig , Piipari Kaisa , Al-Qassab Hind , Smith Mark A. , Parker Nadeene , Carling David , Viollet Benoit , Withers Dominic J. , Ashford Michael L. J.
Published: May 2010

AMPK (AMP-activated protein kinase) signalling plays a key role in whole-body energy homoeostasis, although its precise role in pancreatic β-cell function remains unclear. In the present stusy, we therefore investigated whether AMPK plays a critical function in β-cell glucose sensing and is required for the maintenance of normal glucose homoeostasis. Mice lacking AMPKα2 in β-cells and a population of hypothalamic neurons (RIPCreα2KO mice) and RIPCreα2KO mice lacking AMPKα1 (α1KORIPCreα2KO) globally were assessed for whole-body glucose homoeostasis and insulin secretion. Isolated pancreatic islets from these mice were assessed for glucose-stimulated insulin secretion and gene expression changes. Cultured β-cells were examined electrophysiologically for their electrical responsiveness to hypoglycaemia. RIPCreα2KO mice exhibited glucose intolerance and impaired GSIS (glucose-stimulated insulin secretion) and this was exacerbated in α1KORIPCreα2KO mice. Reduced glucose concentrations failed to completely suppress insulin secretion in islets from RIPCreα2KO and α1KORIPCreα2KO mice, and conversely GSIS was impaired. β-Cells lacking AMPKα2 or expressing a kinase-dead AMPKα2 failed to hyperpolarize in response to low glucose, although KATP (ATP-sensitive potassium) channel function was intact. We could detect no alteration of GLUT2 (glucose transporter 2), glucose uptake or glucokinase that could explain this glucose insensitivity. UCP2 (uncoupling protein 2) expression was reduced in RIPCreα2KO islets and the UCP2 inhibitor genipin suppressed low-glucose-mediated wild-type mouse β-cell hyperpolarization, mimicking the effect of AMPKα2 loss. These results show that AMPKα2 activity is necessary to maintain normal pancreatic β-cell glucose sensing, possibly by maintaining high β-cell levels of UCP2.
Spectral functions for the Schrödinger operator on R+ with a singular potential
Authors: Kirsten Klaus , Loya Paul
Published: May 2010

In this article we analyze the spectral zeta function, the heat kernel, and the resolvent of the operator −d2/dr2+κ/r2+r2 over the interval (0,∞) for κ≥−1/4. Depending on the self-adjoint extension chosen, nonstandard properties of the zeta function and of asymptotic properties of the heat kernel and resolvent are observed. In particular, for the zeta function nonstandard locations of poles as well as logarithmic branch cuts at s=−k, k∊N0, do occur. This implies that the small-t asymptotic expansion of the heat kernel can have nonstandard powers as well as terms such as tk/(ln t)ℓ+1 for k,ℓ∊N0. The corresponding statements for the resolvent are also shown. Furthermore, we evaluate the zeta determinant of the operator for all values of κ and any self-adjoint extension.
New reductions of integrable matrix partial differential equations: Sp(m)-invariant systems
Authors: Tsuchida Takayuki
Published: May 2010

We propose a new type of reduction for integrable systems of coupled matrix partial differential equations; this reduction equates one matrix variable with the transposition of another multiplied by an antisymmetric constant matrix. Via this reduction, we obtain a new integrable system of coupled derivative modified KdV equations and a new integrable variant of the massive Thirring model, in addition to the already known systems. We also discuss integrable semidiscretizations of the obtained systems and present new soliton solutions to both continuous and semidiscrete systems. As a by-product, a new integrable semidiscretization of the Manakov model (self-focusing vector nonlinear Schrödinger equation) is obtained.
Gradings on the real forms of the Albert algebra, of g2, and of f4
Authors: Calderón Martín A. J. , Draper C. , Martín González C.
Published: May 2010

We find all the fine group gradings on the real forms of the Albert algebra and of the exceptional Lie algebras g2 and f4.
Temperature dependent valence states and magnetic properties of lithium delithiated Li0.59FePO4
Authors: Lee In Kyu , Shim In-Bo , Kim Chul Sung
Published: May 2010

Polycrystalline samples of Li0.59FePO4 were prepared by oxidation reaction of pure LiFePO4, and temperature dependent valence states and magnetic properties were studied. X-ray diffraction patterns showed a biphasic olivine-type orthorhombic structure (space group: Pnma) where triphylite (LiFePO4) and heterosite (FePO4) coexisted. Also, we have observed the biphasic antiferromagnetic ordering of triphylite and heterosite with different antiferromagnetic to paramagnetic ordering transition temperatures. Mössbauer spectra of Li0.59FePO4 showed a two-phase asymmetrical eight line pattern due to the different electric quadrupole interactions in triphylite and heterosite. The iron ions of triphylite and heterosite are at Fe2+ (3d6) and the Fe3+ (3d5) valence state. Also the large value of ΔEQ for the triphylite phase was originated from the asymmetric charge distribution of FeO6. These results indicate that the charge distributions around the Fe nucleus in the triphylite are more asymmetric because of the contribution from the crystal field and the ion valence state.
Grain boundary structure and chemistry of Dy-diffusion processed Nd–Fe–B sintered magnets
Authors: Sepehri-Amin H. , Ohkubo T. , Hono K.
Published: May 2010

We have investigated the microstructure of grain boundary diffusion processed Nd–Fe–B sintered magnets by high resolution scanning electron microscopy, high resolution transmission electron microscopy, and laser assisted atom probe to understand the mechanism of coercivity enhancement. After the vapor coating of Dy to the sintered magnets, the sample were annealed to let it diffuse in the sample through the grain boundary diffusion. The composition of the outer region of the Nd2Fe14B grains changed to (Nd,Dy)2Fe14B due to the substitution of Dy for Nd. Excess Nd ejected from the Nd2Fe14B grains led to the formation of continuous Nd-rich grain boundaries.
Reduction of artifact of metallic implant in magnetic resonance imaging by combining paramagnetic and diamagnetic materials
Authors: Gao Yanhui , Muramatsu Kazuhiro , Kushibe Atsumichi , Yamazaki Keita , Chiba Akihiko , Yamamoto Toru
Published: May 2010

The method of coating the metallic implant made of paramagnetic materials with diamagnetic materials has been proposed to reduce the magnetic disturbance of metallic implants which causes artifact in magnetic resonance imaging. The optimal thicknesses of the diamagnetic coatings have been obtained for a straight cylindrical hip joint and an aneurysm clip by using the magnetic field analysis of the finite element method (FEM). Whereas in the manufacturing, with respect to the mechanical force of the diamagnetic material, etc., the new structure of dual-material model with diamagnetic material inside and paramagnetic material outside is considered better. In this paper, first the effectiveness of the structure of the dual-material model with actual diamagnetic material inside and paramagnetic material outside is investigated by using the FEM. Then optimal thicknesses of paramagnetic coating of two models are obtained. Finally the effectiveness of the dual-material model is verified by the experiment.
Silane-based functionalization of synthetic antiferromagnetic nanoparticles for biomedical applications
Authors: Zhang Mingliang , Hu Wei , Earhart Christopher M. , Tang Mary , Wilson Robert J. , Wang Shan X.
Published: May 2010

Synthetic antiferromagnetic nanoparticles (SAFNPs) have been successfully coated with two different kinds of silanes, 3-aminopropyltrimethoxysilane and 2-[methoxy(polyethyleneoxy)propyl]trimethoxysilane. The morphology of SAF particles is characterized by scanning electron microscopy and magnetic properties by alternating gradient magnetometry. The attachment of silane molecules is verified by Fourier-transform infrared spectroscopy and colloidal stability is studied using dynamic light scattering. These two silanes change the surface chemical properties of SAFNPs dramatically in different ways, which in turn affects the stability of these particles.
Subvoxel limits of magnetic resonance angiography: One-dimensional case
Authors: Takeuchi Michihiro , Kim Dongmin , Sekino Masaki , Ueno Shoogo , Ohsaki Hiroyuki , Iriguchi Norio
Published: May 2010

Although the pixel size of magnetic resonance angiography (MRA) defines the spatial resolution of measured images, MRA visualizes blood vessels whose diameters are comparable to or smaller than the pixel size. In the present study, we carried out simplified one-dimensional numerical simulations and two-dimensional imaging experiments to show that discretization errors significantly appear in the measurement of very thin samples, or samples having subpixel structures. Magnetic resonance signals were calculated for a numerical model of blood vessel. The signal intensity was significantly affected by the small displacements. The experimentally obtained signal intensities agreed well with numerical simulations. The signals were summed within a region-of-interest (ROI) covering several pixels. A decrease in the number of pixels included in the ROI led to a decrease in the fluctuation of signal intensity.
Kinetic arrest of direct and reverse martensitic transformation and exchange bias effect in Mn49.5Ni40.4In10.1 melt spun ribbons
Authors: Llamazares J. L. Sánchez , Hernando B. , Suñol J. J. , García C. , Ross C. A.
Published: May 2010

Phase coexistence phenomena related to direct and reverse martensitic transformation have been studied in melt spun ribbons of the magnetic shape memory alloy Mn49.5Ni40.4In10.1. For magnetic fields above 10 kOe martensitic transformation undergoes a progressive kinetic arrest. The metastable character of the field-cooled frozen fraction of austenite into martensite was verified. An atypical incomplete reverse martensitic transformation of thermal origin was also observed. The zero-field cooled thermomagnetization curve measured at 50 kOe shows a decrease below 30 K that was accompanied by the occurrence of exchange bias effect suggesting the strengthening of antiferromagnetic interactions in martensite in such temperature range.
The effect of oxygen doping on the magnetism of Tb and Pr clusters
Authors: van Dijk C. N. , Rasing Th. , Kirilyuk A. , Bowlan J. , Liang A. , de Heer W. A.
Published: May 2010

The magnetic moments and electric dipoles of Tb and Pr clusters are investigated using the Stern–Gerlach deflection technique. The addition of a single oxygen atom induces an increase in the electric dipole of TbN clusters, however the magnetic moment is largely not affected. In Pr neither the magnetic moment nor the electric dipole is affected. This raises questions as to the role of conduction electrons in the exchange interaction of rare earth clusters, and puts into doubt the validity of the Ruderman-Kittel-Kasuya-Yosida (RKKY) exchange mechanism in small systems.
Origin of magnetostriction in Fe–Ga
Authors: Mudivarthi Chaitanya , Laver Mark , Cullen James , Flatau Alison B. , Wuttig Manfred
Published: May 2010

This paper investigates the origin of large magnetostriction in Fe–Ga alloys using small-angle neutron scattering (SANS) and Kerr microscopy. The SANS data for a single-crystal, electron irradiated, and quenched Fe81Ga19 sample under externally applied magnetic and elastic fields revealed the existence of magnetostrictive nanoclusters spaced at ∼15 nm apart that have a different magnetization than the A2 matrix. Combining the SANS results and the magnetization orientation obtained from the magnetic domain images using a Kerr microscope, it appears that the nanoclusters contribute significantly to the macroscopic magnetostriction.
Dielectric, magnetic and magnetoelectric properties of multiferroic BiFe0.5Cr0.5O3–NiFe2O4 composites
Authors: Babu S. Narendra , Hsu Jen-Hwa , Chen Y. S. , Lin J. G.
Published: May 2010

Multiferroic composites of NiFe2O4 (NFO) and BiFe0.5Cr0.5O3 (BFCO) are synthesized and their dielectric, magnetic, and magnetoelectric (ME) properties are measured at room temperature. NFO-BFCO forms a two-phase composite. The composite has a larger magnetization and dielectric constant than those of both parent compounds, due to the effects of interfacial strain on BFCO. Furthermore, the ME response in NFO-BFCO is about one time larger than that of BFCO, revealing the success of magnetic control of the dielectric response via the mechanical coupling, which can be exploited in the future applications of multiferroic composites.
Induction magnetometer using a high-Tc superconductor coil
Authors: Sasada Ichiro
Published: May 2010

An induction magnetometer consisting of a search coil and an inverting operational amplifier is simple in structure and in signal transferring mechanism from the magnetic field input to the voltage output. Because this magnetometer is based on Faraday’s law of induction, it has a lower cutoff frequency r/(2πL), where r is the resistance of the coil and L is its inductance. An attempt has been made to lower the cutoff frequency of the induction magnetometer by using a high-Tc superconductor coil. With a pancake coil (inner diameter ≈18 cm and outer diameter ≈23 cm, 92 turns, 3.23 mH) made of a Bismuth strontium calcium copper oxide (BSCCO) superconductor tape of 5 mm in width and 0.23 mm in thickness, the cutoff frequency achieved was 1.7 Hz which is much lower than that obtained with a bulky copper search coil which is typically in the range of 10–20 Hz. In the experiment, an inverting amplifier was made with a complementary metal-oxide semiconductor operational amplifier and was immersed in liquid nitrogen together with a BSCCO high-Tc superconducting coil. Discussion is made on the resolution of the induction magnetometer using a high-Tc superconductor search coil.
Electronic structure, crystallographic, magnetic, and transport characterization of EuMn2 films
Authors: Balin K. , Szade J. , Hutchison A. J. , Nowak A. , Gibaud A. , Celinski Z.
Published: May 2010

We report the formation of EuMn2, in the form of a thin film, grown by the reaction of Eu/Mn multilayers in the solid state phase at 480 K. X-ray diffraction (XRD) studies revealed that the EuMn2 crystallizes in a hexagonal structure, with the P6/mmc space group, and lattice parameters a=0.72 nm and c=1.07 nm. X-ray photoelectron spectroscopy measurements showed divalent europium forming the compound. Transition to a magnetically ordered phase was observed at 15 K. The value of 4πMs was estimated to be 1.5 kG at 2 K. An unusual behavior of the temperature dependence of resistivity was observed in the film, suggesting the presence of valence fluctuation systems.
Magneto-optical visualization of vortices penetration into Ba(Fe1.8Co0.2)As2
Authors: Lin Zhi Wei , Zhu Jianguo , Guo Youguang , Li Yongjian , Wang Shuhong , Zhang Yi Bing , Xu Ke Xi , Cai Chuan Bing
Published: May 2010

Vortices penetration into oxygen-free superconducting compounds FeAs-122 system is of interest in understanding superconductivity. This work studies the vortices motion in Ba(Fe1.8Co0.2)As2 single crystal by means of magneto-optical imaging technique in zero field cooled and field cooled conditions. The captured magneto-optical images and corresponding flux profiles show that, at zero field cooled condition, vortices penetrate into the crystal from the edges as external magnetic field increases. A vortices-free region is observed at the center of sample as applied field is less than full penetration field. In field cooled condition, the introduced vortices leave the sample at the edges as field decreases and polarization of the vortices at the edges are opposite as decreasing field approaches to zero. The pinning strength decreases with increasing temperature. The observed vortex behavior is very similar to that in high Tc superconducting materials with strong pinning strength.
Excited metastables electronic spin states in spin crossover compounds studies by atom-phonon coupling model: Gradual and two-step transition cases
Authors: Gindulescu A. , Rotaru A. , Linares J. , Dimian M. , Nasser J.
Published: May 2010

This contribution reports the study of metastable spin states in spin-crossover materials in the framework of the atom-phonon coupling model. Using this model for a linear chain we show theoretically for the first time that, even if the cooperativity is not strong enough to obtain hysteresis at high temperatures, metastable states exist at low temperatures for a high spin (HS) fraction of nHS=1. This gradual thermal transition featuring metastable states at low temperature has been observed experimentally by [Létard et al., J. Phys.: Conf. Ser. 21, 23 (2005)]. Moreover, for compounds showing a two-step thermal transition, we show that metastable states, corresponding to a HS fraction nHS=0.5, are present. This metastable states appear up to 50 K, fact that was observed by [Moussa et al., Phys. Rev. Lett. 94, 107205 (2005)] and [Matsumoto et al., J. Phys.: Conf. Ser. 148, 012029 (2009)].
A lower bound on the ground state energy of dilute Bose gas
Authors: Lee Ji Oon , Yin Jun
Published: May 2010

Consider an N-boson system interacting via a two-body repulsive short-range potential V in a three dimensional box Λ of side length L. We take the limit N,L→∞ while keeping the density ρ=N/L3 fixed and small. We prove a new lower bound for its ground state energy per particle, E(N,Λ)/N≥4πaρ[1−O(ρ1/3|log ρ|3)], as ρ→0, where a is the scattering length of V.
Symmetries and integrability of a fourth-order Euler–Bernoulli beam equation
Authors: Bokhari Ashfaque H. , Mahomed F. M. , Zaman F. D.
Published: May 2010

The complete symmetry group classification of the fourth-order Euler–Bernoulli ordinary differential equation, where the elastic modulus and the area moment of inertia are constants and the applied load is a function of the normal displacement, is obtained. We perform the Lie and Noether symmetry analysis of this problem. In the Lie analysis, the principal Lie algebra which is one dimensional extends in four cases, viz. the linear, exponential, general power law, and a negative fractional power law. It is further shown that two cases arise in the Noether classification with respect to the standard Lagrangian. That is, the linear case for which the Noether algebra dimension is one less than the Lie algebra dimension as well as the negative fractional power law. In the latter case the Noether algebra is three dimensional and is isomorphic to the Lie algebra which is sl(2,R). This exceptional case, although admitting the nonsolvable algebra sl(2,R), remarkably allows for a two-parameter family of exact solutions via the Noether integrals. The Lie reduction gives a second-order ordinary differential equation which has nonlocal symmetry.
Simple modeling of self-oscillations in nanoelectromechanical systems
Authors: Lazarus A. , Barois T. , Perisanu S. , Poncharal P. , Manneville P. , de Langre E. , Purcell S. T. , Vincent P. , Ayari A.
Published: May 2010

We present here a simple analytical model for self-oscillations in nanoelectromechanical systems. We show that a field emission self-oscillator can be described by a lumped electrical circuit and that this approach is generalizable to other electromechanical oscillator devices. The analytical model is supported by dynamical simulations where the electrostatic parameters are obtained by finite element computations.
The “ghost” symmetry of the BKP hierarchy
Authors: Cheng Jipeng , He Jingsong , Hu Sen
Published: May 2010

In this paper, we systematically develop the “ghost” symmetry of the Kadomtsev-Petviashvili sub-hierarchy of B type (BKP) through its actions on the Lax operator L, the eigenfunctions, and the τ function. In this process, the spectral representation of the eigenfunctions and a new potential are introduced by using squared eigenfunction potential of the BKP hierarchy. Moreover, the bilinear identity of the constrained BKP hierarchy and Adler–Shiota–van Moerbeke formula of the BKP hierarchy are rederived compactly by means of the spectral representation and “ghost” symmetry.
Stability of negative solitary waves for an integrable modified Camassa–Holm equation
Authors: Yin Jiuli , Tian Lixin , Fan Xinghua
Published: May 2010

In this paper, we prove that the modified Camassa–Holm equation is Painlevé integrable. We also study the orbital stability problem of negative solitary waves for this integrable equation. It is shown that the negative solitary waves are stable for arbitrary wave speed of propagation.
Analysis of the configurational temperature of polymeric liquids under shear and elongational flows using nonequilibrium molecular dynamics and Monte Carlo simulations
Authors: Baig Chunggi , Edwards Brian J.
Published: May 2010

We present a detailed analysis of the configurational temperature (Tconf) for its application to polymeric materials using nonequilibrium molecular dynamics (NEMD) and nonequilibrium Monte Carlo (NEMC) methods. Simulations were performed of linear polyethylene liquid C78H158 undergoing shear and elongational flows. At equilibrium, Tconf is equal to the set point temperature of the simulation. An aphysically large decrease in Tconf is observed in the NEMD simulations for both flows, especially at strong flow fields. By analyzing separately the individual contributions of the different potential interaction modes to the configurational temperature, it is found that the bonded modes (which constitutes almost 99.5% of the total) dominate the total Tconf over the nonbonded ones; i.e., bond-stretching (≈86.5%), bond-bending (≈11.8%), bond-torsional (≈1.2%), nonbonded intermolecular (≈0.4%), and intramolecular (≈0.1%) Lennard-Jones. The configurational temperature of the individual modes generally exhibits a nonmonotonic behavior with the flow strength and a dramatic change beyond a critical value of flow strength; this is mainly attributed to the dynamical effect of strong molecular collisions occurring at strong flow fields. In contrast, no such behavior is observed in the NEMC simulations where such dynamical effects are absent. Based on the principal physical concept of the configurational temperature, which represents the large-scale structural characteristics of the system, we propose to exclude the dynamical effects exhibited by the individual interaction modes, in obtaining a physically meaningful Tconf as the configurational entropy of the system should not be affected by such factors. Since (a) the main difference between equilibrium and nonequilibrium states lies in the change in the overall (global) structure (represented by the bond torsional and nonbonded modes), and (b) the local, very short structure (represented by the bond-stretching and bond-bending modes) is barely changing between equilibrium and nonequilibrium states and its contribution to the total system configurational entropy is negligible compared to the large-scale structural changes, in order to accurately describe the structural changes occurring at nonequilibrium states by use of the configurational temperature, we further propose that only the contributions from the bond-torsional and nonbonded modes to ΔTconf between equilibrium and nonequilibrium states should be taken into account to generate a physically meaningful ΔTconf. Applying the above hypothesis to the analysis of the simulation data, good agreement between the NEMD and NEMC simulations (and between NEMD simulations for different flows) is observed. Furthermore, the configurational temperature obtained in such way is found to match remarkably well with the heat capacity of amorphous polyethylene liquids and the flow-enhanced melting-point elevation reported in experiment.
Study of the change of electron temperature inside magnetic island caused by localized radio frequency heating
Authors: Yang J. , Zhu S. , Yu Q. , Zhuang G.
Published: May 2010

The change in the electron temperature inside magnetic island caused by localized radio frequency (rf) heating is studied numerically by solving the two-dimensional energy transport equation, to investigate the dependence of the temperature change on the location and width of the rf power deposition along the minor radius and the helical angle, the island width, and the ratio between the parallel and the perpendicular heat conductivity. Based on obtained numerical results, suggestions for optimizing the island stabilization by localized rf heating are made.
Modified screening potential in a high density inhomogeneous quantum dusty magnetoplasma
Authors: Hussain A. , Zeba I. , Salimullah M. , Murtaza G. , Jamil M.
Published: May 2010

The effect of strong ambient static magnetic field on Shukla–Nambu–Salimullah (SNS) potential in a dusty quantum magnetoplasma has been investigated using quantum hydrodynamic model. The potential is significantly modified by quantum statistical effects, density inhomogeneity, and dust polarization drift effect. The effective length of the modified SNS potential is found to be a sensitive function of external static magnetic field, E×B0 drift, and the scale length of inhomogeneity. Here E is the electric polarization vector produced via density inhomogeneity, and B0 is the ambient static magnetic field. It is found that dust polarization drift effect predominates the ion polarization drift effect in high magnetic field environments. It attracts our attention to the careful study of the underlying physics of dusty plasma environment of neutron stars and magnetars.
Numerical study of ion-cyclotron resonant interaction via hybrid-Vlasov simulations
Authors: Valentini Francesco , Iazzolino Antonio , Veltri Pierluigi
Published: May 2010

Hybrid Vlasov–Maxwell numerical simulations are used to investigate the collisionless resonant interaction of ions with ion-cyclotron waves in parallel propagation with respect to a background magnetic field. In linear regime, analytical results on wave damping, obtained by integrating the linearized Vlasov equation through the well-known characteristics method, are compared with the numerical results. Then, the ion heating process and the consequent generation of temperature anisotropy in the direction perpendicular to the background magnetic field are investigated numerically in detail. In nonlinear regime, the numerical results show that the distribution of particle velocities is strongly distorted due to the resonant ion-cyclotron interaction with the formation of diffusive plateaus in the longitudinal direction (with respect to the ambient field) and significantly departs from the Maxwellian equilibrium. These results are relevant in many plasma physics environments, such as the solar wind, where the process of ion-cyclotron heating and the generation of temperature anisotropy and non-Maxwellian velocity distributions are routinely recovered in many in situ measurements, or the laboratory plasmas, where the resonant interaction of ions with ion-cyclotron waves is the primary source of auxiliary heating in the confining apparatus.
S
33
nuclear magnetic resonance spectroscopy of biological samples obtained with a laboratory model S33 cryogenic probe
Authors: Hobo Fumio , Takahashi Masato , Saito Yuta , Sato Naoki , Takao Tomoaki , Koshiba Seizo , Maeda Hideaki
Published: May 2010

S 33 nuclear magnetic resonance (NMR) spectroscopy is limited by inherently low NMR sensitivity because of the quadrupolar moment and low gyromagnetic ratio of the S33 nucleus. We have developed a 10 mm S33 cryogenic NMR probe, which is operated at 9–26 K with a cold preamplifier and a cold rf switch operated at 60 K. The S33 NMR sensitivity of the cryogenic probe is as large as 9.8 times that of a conventional 5 mm broadband NMR probe. The S33 cryogenic probe was applied to biological samples such as human urine, bile, chondroitin sulfate, and scallop tissue. We demonstrated that the system can detect and determine sulfur compounds having SO42− anions and –SO3− groups using the S33 cryogenic probe, as the S33 nuclei in these groups are in highly symmetric environments. The NMR signals for other common sulfur compounds such as cysteine are still undetectable by the S33 cryogenic probe, as the S33 nuclei in these compounds are in asymmetric environments. If we shorten the rf pulse width or decrease the rf coil diameter, we should be able to detect the NMR signals for these compounds.
Terahertz emission from metal-organic chemical vapor deposition grown Fe:InGaAs using 830 nm to 1.55 μm excitation
Authors: Wood C. D. , Hatem O. , Cunningham J. E. , Linfield E. H. , Davies A. G. , Cannard P. J. , Robertson M. J. , Moodie D. G.
Published: May 2010

We demonstrate the generation of broadband terahertz (THz) frequency radiation from photoconductive emitters formed from Fe-doped InGaAs (Fe:InGaAs), grown by metal-organic chemical vapor deposition, following pulsed (femtosecond) laser excitation at wavelengths ranging from 830 nm to 1.55 μm. The Fe is incorporated epitaxially during growth, giving precise control over the doping level. Using both single-crystal ZnTe and GaP electro-optic detectors over the same wavelength range, the emission spectra from several Fe:InGaAs wafers with different Fe content were measured, with THz emission from all wafers showing bandwidths in excess of 2.0 THz. The THz output power was found to be strongly dependant on the Fe content, the thickness of the Fe:InGaAs layer, and the excitation wavelength.
Epitaxial graphene on cubic SiC(111)/Si(111) substrate
Authors: Ouerghi A. , Kahouli A. , Lucot D. , Portail M. , Travers L. , Gierak J. , Penuelas J. , Jegou P. , Shukla A. , Chassagne T. , Zielinski M.
Published: May 2010

Epitaxial graphene films grown on silicon carbide (SiC) substrate by solid state graphitization is of great interest for electronic and optoelectronic applications. In this paper, we explore the properties of epitaxial graphene films on 3C-SiC(111)/Si(111) substrate. X-ray photoelectron spectroscopy and scanning tunneling microscopy were extensively used to characterize the quality of the few-layer graphene (FLG) surface. The Raman spectroscopy studies were useful in confirming the graphitic composition and measuring the thickness of the FLG samples.
Using graded barriers to control the optical properties of ZnO/Zn0.7Mg0.3O quantum wells with an intrinsic internal electric field
Authors: Hall C. R. , Dao L. V. , Koike K. , Sasa S. , Tan H. H. , Inoue M. , Yano M. , Jagadish C. , Davis J. A.
Published: May 2010

Quantum wells with graded barriers are demonstrated as a means to control both the transition energy and electron-hole wave function overlap for quantum wells with an intrinsic internal electric field. In the case of c-axis grown ZnO/ZnMgO quantum wells, the graded barriers are produced by stepping the magnesium composition during the growth process. Four quantum wells with different structures are examined, where each well has similar transition energy, yet a wide range of wave function overlaps are observed. Photoluminescence and time resolved photoluminescence show good agreement with calculations.
The impact of SiNx gate insulators on amorphous indium-gallium-zinc oxide thin film transistors under bias-temperature-illumination stress
Authors: Jung Ji Sim , Son Kyoung Seok , Lee Kwang-Hee , Park Joon Seok , Kim Tae Sang , Kwon Jang-Yeon , Chung Kwun-Bum , Park Jin-Seong , Koo Bonwon , Lee Sangyun
Published: May 2010

The threshold voltage instability (Vth) in indium-gallium-zinc oxide thin film transistor was investigated with disparate SiNx gate insulators under bias-temperature-illumination stress. As SiNx film stress became more tensile, the negative shift in Vth decreased significantly from −14.34 to −6.37 V. The compressive films exhibit a nitrogen-rich phase, higher hydrogen contents, and higher N–H bonds than tensile films. This suggests that the higher N–H related traps may play a dominant role in the degradation of the devices, which may provide and/or generate charge trapping sites in interfaces and/or SiNx insulators. It is anticipated that the appropriate optimization of gate insulator properties will help to improve device reliability.
Characterization and mechanism studies of dielectric barrier discharges generated at atmospheric pressure
Authors: Tang Jie , Duan Yixiang , Zhao Wei
Published: May 2010

A dielectric barrier discharge (DBD) device operated at ambient air with an ac power supply was designed and examined. The discharge power and active current of DBD were characterized. Experimental results show that the discharge power does not proportionally increase all along with voltage. Through in-depth analysis of typical waveforms of instantaneous applied voltage and discharge current, and images of microdischarges in the gas gap, it is inferred that considerable reduction in charges transferred through discharge channels is most likely due to recombination and attachment to electronegative molecules, nonuniform highly distorted electric fields, and repulse of more homogeneous electric charges.
Spatial redistribution of the optical field intensity in inverted polymer solar cells
Authors: Chen Fang-Chung , Wu Jyh-Lih , Hung Yi
Published: May 2010

We have used indium tin oxide (ITO), a transparent conducting oxide, as an optical spacer to improve the performance of inverted polymer solar cells. The optical interference effect resulted in spatial redistribution of the optical field in the devices. Although the degree of light absorption in inverted cells was not increased, the resulting favorable distribution of photogenerated excitons probably decreased the level of exciton quenching near the electrodes. As a result, the introduction of the ITO optical spacer at an appropriate thickness increased the short-circuit current density and the overall power conversion efficiency.
High-power surface emission from terahertz distributed feedback lasers with a dual-slit unit cell
Authors: Mahler Lukas , Tredicucci Alessandro , Beltram Fabio , Walther Christoph , Faist Jérôme , Beere Harvey E. , Ritchie David A.
Published: May 2010

We present a surface emitting distributed feedback terahertz laser resonator based on a dual-slit configuration. With the spacing of the slits as a parameter, the surface losses of the lasers can be chosen over a large range, while keeping slits narrow for optimum current injection. Quantum cascade devices based on a double metal waveguide showed slope efficiencies up to 40 mW/A and peak powers of more than 20 mW. The efficient radiation out-coupling does not depend on boundary conditions, and therefore would allow the application to large-area devices, making this an ideal resonator for high-power surface emission.
ZnO–ZnTe nanocone heterojunctions
Authors: Lee Sang Hyun , Zhang X.-G. , Smith Barton , Seo Sung Seok A. , Bell Zane W. , Xu Jun
Published: May 2010

We report heterojunctions made of vertically aligned ZnO–ZnTe nanocones synthesized using a combination of thermal vapor deposition and pulsed-laser deposition. ZnO nanocones and nanorods were controlled by utilizing the growth rate difference between central and boundary sites of precursor domains. The p–n heterojunctions were subsequently formed by growing ZnTe as shells on the nanocone surface. Structural and electric characteristics indicate that nanocones are more feasible than nanorods for forming heterojunction. Furthermore, theoretical modeling demonstrates that the nanocone-based junction exhibits an electrostatic potential profile that is much more effective for carrier transport than the electrostatic potential for the nanorod-based junction.
Hybrid interfaces of biological molecules and metals: The prototypical case of adenine on Cu(110)
Authors: Bussolotti F. , Friedlein R.
Published: May 2010

Electronic and structural properties of thin, chemisorbed adenine films on Cu(110) have been investigated by ultraviolet photoelectron spectroscopy and reflection high-energy electron diffraction. Molecular reorientation at the particular coverage of about 0.3 ML from a disordered flat-lying to a long-range ordered standing-up phase is accompanied by pronounced changes of the interfacial dipole provided by the alignment of the intrinsic dipole moment of the polar molecule. Similar hybrid interfacial states are observed for ordered flat-lying and standing-up layers, suggesting comparable atomic site-specific N–Cu interactions.
Gay men's sex venues, the men who use them, and gay community perceptions: insights from a convenience sample of gay men attending a community festival in Melbourne
Authors: Smith Anthony M. A. , Grierson Jeffrey W. , von Doussa Henry
Published: May 2010

Background: Despite being understood as sites for the potential spread of sexually transmissible infections, we know remarkably little about gay men’s sex venues and how they are perceived in the gay community. The present paper aims to describe community attitudes to sex venues and towards the gay men who use them. Methods: Self-administered questionnaire at a gay community social event. Results: Men who use gay men’s sex venues differ from non-users in relation to their age, the number of casual sexual partners they have, their openness about their sexuality and their comfort with sexualised spaces. Also, not all venues are equal and appear to attract diverse clienteles with particular characteristics. Conclusion: Differentiation among gay men’s sex venues and the men who use them may offer opportunities for targeting interventions for sexual health promotion.
Trends in the location of the HIV-positive population in Australia: Implications for access to healthcare services and delivery
Authors: Carman Marina , Grierson Jeffrey , Pitts Marian , Hurley Michael , Power Jennifer
Published: May 2010

Background: Examining existing and potential trends in the HIV-positive population in Australia is important for current and future healthcare service development and delivery. Methods: A new analysis of existing data on this population from the HIV Futures 5 survey was based on linking a geographic breakdown of respondents based on ‘area type’ – capital city or inner suburban, outer suburban, regional centre and rural – with patterns of healthcare service access. In addition, the distance between the postcode of the respondent’s residence and the postcode of the doctor seen for HIV-related treatment was calculated. An analysis of ‘area type’ by income and age was also conducted. Results: The ‘area type’ analysis showed important differences in patterns of access to antiretroviral prescriptions and choice of provider for HIV-related and general healthcare. The median distance travelled to see a doctor for HIV-related treatment was higher for those living in outer suburbs than those living in regional centres. Discussion: Differences in service use appear to be related to geographic accessibility of different service types. However, there may be other important social, economic and cultural factors involved. Ageing and socio-economic pressures may be influencing a move away from inner suburban areas where most HIV-specific care is located. This new analysis assists in finding the right balance between increasing the accessibility of HIV-specific services and ‘mainstreaming’. Longitudinal data collection would further assist in tracking trends in geographic location, and how often and at what intervals people living with HIV utilise healthcare services.
'There is no love here anyway.' Sexuality, identity and HIV prevention in an African sub-culture in Amsterdam, The Netherlands
Authors: Heus Lineke
Published: May 2010

Background: Undocumented African immigrants in The Netherlands are persons perceived to be at high-risk for HIV infection and yet are also a group that health care providers find difficult to access. The present study explores the experiences of a sample of undocumented African immigrants living in Amsterdam and offers recommendations aimed at providing more effective prevention interventions. Methods: Data collection occurred through interviews and focus groups with men and women aged 20–35 of both African and Dutch descent, using their interactions to explore possible communication challenges. Field notes of interviews were transcribed and analysed to identify emergent themes and patterns. A conceptual framework related to power and identity construction was adopted. Results: The findings of the present study show how identity is shaped and constrained by discourses around sexuality and health, as well as what participants perceived to be conflicting belief systems, as well as the Dutch socioeconomic context. The data were divided into two broad categories: challenges around Dutch prevention interventions and challenges around peer-support. Each category is structured around sub-themes, such as ‘concepts used in prevention messages’, ‘inter-cultural tension’, ‘identification with the educator’ and ‘stigma: roots and implications’. Conclusions: These findings indicate that issues of power and identity construction have great implications for the uptake of HIV prevention strategies by African immigrant groups and reveal important opportunities on which to focus prevention efforts.
Interventions for young people in Australia to reduce HIV and sexually transmissible infections: a systematic review
Authors: Kang Melissa , Skinner Rachel , Usherwood Tim
Published: May 2010

Background: Like young people in other developed countries, sexually active young Australians can have an increased risk of acquiring sexually transmissible infections (STIs). This paper reviews intervention programs that aim to reduce the incidence and transmission of HIV and STIs among young people in Australia. Methods: Articles were identified from seven databases. Intervention studies conducted in Australia that included young people aged 12–25 years were reviewed. A two-dimensional matrix consisting of ‘setting’ and ‘intervention type’ was developed to categorise each study. Results: Forty-two studies met the inclusion criteria, and the majority were uncontrolled intervention studies. Of these, 23/42 studies measured participation in chlamydia ± other STI testing and found that the highest participation rates took place in non-clinical and non-general practice health care settings. Four studies facilitated access to testing indirectly, through the internet or other media. Ten studies involved the provision of education and measured its impact on factors such as knowledge, attitudes and/or behaviour. Three studies involved novel immunisation strategies for either hepatitis B or human papillomavirus vaccines. Two studies evaluated the impact of enhanced STI surveillance programs on prevalence rates. Conclusions: Proactive STI testing in non-clinical and some health settings appears feasible and achieves higher testing rates than in general practice; however, more evaluation of testing strategies in general practice settings is required. New technologies such as the internet and SMS are useful adjuncts for influencing behaviours such as condom use and STI testing. Media campaigns that promote STI testing can have a positive impact on testing rates.
Safer sexual behaviours after 1 year of antiretroviral treatment in KwaZulu-Natal, South Africa: a prospective cohort study
Authors: Peltzer Karl , Ramlagan Shandir
Published: May 2010

Background: As antiretroviral treatment (ART) becomes more widely available in low and middle income countries, the relationship between treatment and sexual risk behaviour in these countries has also become more important. Methods: This is a prospective study of all treatment-naϊve patients (n = 735) recruited from all three public hospitals in Uthukela health district in KwaZulu-Natal and followed up at 6 and 12 months of being on ART. Results: No evidence of increased risky sexual behaviours over time was found, from before commencing on ART, to 6 and 12 months on ART. Specifically, a significant reduction in risk taking was reported regarding sex without a condom in the past 3 months (P = 0.001) and unprotected sex with HIV-negative or unknown HIV status persons (P = 0.003). The number of sexual partners did, however, not significantly reduce over time. Some socio-demographic factors were associated with unprotected sex (being a man: odds ratio 1.7 (1.1–2.7), lower education: 0.4 (0.2–0.8)), one health factor (higher CD4 cell counts: 2.6 (1.1–6.1)) and social-behavioural factors (higher stigma: 1.2 (1.1–1.3), alcohol use at last sex: 6.9 (1.8–26.1)) and lower ART adherence: 0.5 (0.2–0.08)), while HIV knowledge (ART optimism, duration since known HIV-positive, HIV disease and treatment related knowledge), HIV symptoms and depression were not associated with unprotected sex. Conclusions: This prospective study with a large sample of persons on ART showed evidence of inhibition of risky sexual behaviours over time. Although unsafe sexual behaviours had decreased, some proportion did not practice safe sex.
SH2 domain containing leukocyte phosphoprotein of 76-kDa (SLP-76) feedback regulation of ZAP-70 microclustering
Authors: Liu Hebin , Purbhoo Marco A. , Davis Daniel M. , Rudd Christopher E.
Published: May 2010

T cell receptor (TCR) signaling involves CD4/CD8-p56lck recruitment of ZAP-70 to the TCR receptor, ZAP-70 phosphorylation of LAT that is followed by LAT recruitment of the GADS-SLP-76 complex. Back regulation of ZAP-70 by SLP-76 has not been documented. In this paper, we show that anti-CD3 induced ZAP-70 cluster formation is significantly reduced in the absence of SLP-76 (i.e., J14 cells) and in the presence of a mutant of SLP-76 (4KE) in Jurkat and primary T cells. Both the number of cells with clusters and the number of clusters per cell were reduced. This effect was not mediated by SLP-76 SH2 domain binding to ZAP-70 because SLP-76 failed to precipitate ZAP-70 and an inactivating SH2 domain mutation (i.e., R448L) on SLP-76 4KE did not reverse the inhibition of ZAP-70 clustering. Mutation of R448 on WT SLP-76 still supported ZAP-70 clustering. Intriguingly, by contrast, LAT clustering occurred normally in the absence of SLP-76, or the presence of 4KE SLP-76 indicating that this transmembrane adaptor can operate independently of ZAP-70-GADS-SLP-76. Our findings reconfigure the TCR signaling pathway by showing SLP-76 back-regulation of ZAP-70, an event that could ensure that signaling components are in balance for optimal T cell activation.
Single cell trapping and DNA damage analysis using microwell arrays
Authors: Wood David K. , Weingeist David M. , Bhatia Sangeeta N. , Engelward Bevin P.
Published: May 2010

With a direct link to cancer, aging, and heritable diseases as well as a critical role in cancer treatment, the importance of DNA damage is well-established. The intense interest in DNA damage in applications ranging from epidemiology to drug development drives an urgent need for robust, high throughput, and inexpensive tools for objective, quantitative DNA damage analysis. We have developed a simple method for high throughput DNA damage measurements that provides information on multiple lesions and pathways. Our method utilizes single cells captured by gravity into a microwell array with DNA damage revealed morphologically by gel electrophoresis. Spatial encoding enables simultaneous assays of multiple experimental conditions performed in parallel with fully automated analysis. This method also enables novel functionalities, including multiplexed labeling for parallel single cell assays, as well as DNA damage measurement in cell aggregates. We have also developed 24- and 96-well versions, which are applicable to high throughput screening. Using this platform, we have quantified DNA repair capacities of individuals with different genetic backgrounds, and compared the efficacy of potential cancer chemotherapeutics as inhibitors of a critical DNA repair enzyme, human AP endonuclease. This platform enables high throughput assessment of multiple DNA repair pathways and subpathways in parallel, thus enabling new strategies for drug discovery, genotoxicity testing, and environmental health.