bluuebunny/crossref_metadata_2025 huggingface dataset:
Interlayer thickness dependence of 90° exchange coupling in Co2MnAl/Cr/Co2MnAl epitaxial trilayer structures
Authors: Bosu S. , Sakuraba Y. , Saito K. , Wang H. , Mitani S. , Takanashi K. , You C. Y. , Hono K.
Published: March 2009

The spacer layer thickness dependence of interlayer exchange coupling has been investigated in the fully epitaxial trilayers of the Co2MnAl (CMA)/Cr/CMA structure. A series of high-quality samples of CMA (20 nm)/Cr (tCr=0.3–8.1 nm)/CMA (10 nm) trilayers was prepared on a MgO substrate by ultrahigh vacuum compatible dc sputtering. Comparison of the results of the experiments and the simulations of magnetization curves revealed novel behavior, dominating the 90° coupling and the absence of 180° coupling. No clear oscillation, only a peak of the 90° coupling strength (J2∼−0.68 erg/cm2), was observed at tCr=1.2 nm.
Crystallographic orientation and the magnetocaloric effect in MnP
Authors: Booth R. A. , Majetich S. A.
Published: March 2009

Here we present results for single crystals of manganese phosphide (MnP), a material exhibiting a first-order ferromagnetic to paramagnetic transition at a Curie temperature of 290 K. MnP has a saturation field of about 7.5 kOe along the c-axis. Along this easy magnetic axis, ΔS was measured to be 2.2, 3.3, and 6.0 J/kg K in applied fields of 10, 20, and 50 kOe, respectively. The density of MnP is 5.49 g/cm3. No hysteresis or irreversibility was measured over a range of temperatures from 10 to 300 K.
Perpendicular applied magnetic field dependence of Josephson current and measurement of trapped magnetic flux in Nb superconducting thin film by vibrating sample magnetometer
Authors: Watanabe Norimichi , Nakayama Akiyoshi , Abe Susumu , Suda Mitsunori , Nishi Yohei , Masuda Koji , Sugaya Chisato
Published: March 2009

We found hysteresis in Josephson current when sufficiently strong magnetic field Hz is applied in the direction perpendicular to the junction plane. This is because the magnetic flux is trapped in a superconducting thin film. So, we fabricated the simplified vibrating sample magnetometer, and we have measured the trapped magnetic flux in Nb superconducting thin film by vibrating the sample near the search coil. When a perpendicular magnetic field Hz was applied to the sample, many vortices were trapped in the perimeter of the sample. However, when a perpendicular applied magnetic field Hz was removed, many vortices were trapped in the central part of the sample. Furthermore, we confirmed that Josephson current was modulated by the parallel magnetic field generated by the vortices.
Structure and charge ordering behavior of the colossal magnetoresistive manganite Nd0.5Sr0.5MnO3
Authors: Luo Z. P. , Miller D. J. , Mitchell J. F.
Published: March 2009

The structure and charge ordering (CO) behavior of the three-dimensional colossal magnetoresistive manganite Nd0.5Sr0.5MnO3 have been studied by transmission electron microscopy. The electron diffraction analysis suggested its room temperature structure as orthorhombic, with a Pnma space group. By controlling the experimental temperature setting either above or below the CO transition temperature, it was observed that the CO grew through the propagation of the CO front. The twin boundaries were the barriers of the CO front movement. In heavily ion irradiated samples, it was observed that the CO front was pinned by the intracrystalline defects, forming a zigzag shape interface. Moreover, the electron beam was observed to influence the CO.
Torque in permanent magnet couplings: Comparison of uniform and radial magnetization
Authors: Ravaud R. , Lemarquand G. , Lemarquand V. , Depollier C.
Published: March 2009

We present a three-dimensional study of the torque transmitted between tile permanent magnets uniformly magnetized. All this study is based on the Coulombian model. The torque is calculated semianalytically by considering all the surface densities that appear on the tiles. In addition, no simplifying assumptions are done in the expressions given in this paper. Consequently, the evaluation of the torque is very accurate and allows us to show the drawbacks of using tile permanent magnets uniformly magnetized instead of using tile permanent magnets radially magnetized. Such an approach is useful because it allows us to realize easily parametric studies.
The interface state assisted charge transport at the MoO3/metal interface
Authors: Yi Yeonjin , Jeon Pyung Eun , Lee Hyunbok , Han Kyul , Kim Hyun Sung , Jeong Kwangho , Cho Sang Wan
Published: March 2009

The interface formation between a metal and MoO3 was examined. We carried out in situ ultraviolet and x-ray photoemission spectroscopy with step-by-step deposition of MoO3 on clean Au and Al substrates. The MoO3 induces huge interface dipoles, which significantly increase the work functions of Au and Al surfaces. This is the main origin of the carrier injection improvement in organic devices. In addition, interface states are observed at the initial stages of MoO3 deposition on both Au and Al. The interface states are very close to the Fermi level, assisting the charge transport from the metal electrode. This explains that thick MoO3 layers provide good charge transport when adopted in organic devices.
Tensor cross sections and the collisional evolution of state multipoles: OH(XΠ2)–Ar
Authors: Dagdigian Paul J. , Alexander Millard H.
Published: March 2009

By means of a kinetic analysis, we show that the overall rate constant for the collisional loss of orientation or alignment of a rotational level is the sum of the rate constant for elastic depolarization and the sum of the rate constants for all rotationally inelastic transitions out of the level under consideration. An expression for the depolarization cross section is derived in terms of tensor cross sections, and the relationship of depolarization to m-resolved transitions is discussed. We use this formalism in simulations, based on high-quality ab initio potential energy surfaces, of the depolarization of the open-shell molecule OH(XΠ2) through collisions with Ar. Good agreement is seen with the results of the two-color polarization spectroscopy experiments of Paterson et al. [J. Chem. Phys. 129, 074304 (2008)]. In addition, we show that the major contribution to elastic collisional depolarization occurs not from weak, glancing collisions but from encounters which probe the inner wall of the potential energy surface.
One-dimensional counterion gas between charged surfaces: Exact results compared with weak- and strong-coupling analyses
Authors: Dean David S. , Horgan Ron R. , Naji Ali , Podgornik Rudolf
Published: March 2009

We evaluate exactly the statistical integral for an inhomogeneous one-dimensional (1D) counterion-only Coulomb gas between two charged boundaries and from this compute the effective interaction, or disjoining pressure, between the bounding surfaces. Our exact results are compared to the limiting cases of weak and strong couplings which are the same for 1D and three-dimensional (3D) systems. For systems with a large number of counterions it is found that the weak-coupling (mean-field) approximation for the disjoining pressure works perfectly and that fluctuations around the mean-field in 1D are much smaller than in 3D. In the case of few counterions it works less well and strong-coupling approximation performs much better as it takes into account properly the discreteness of the counterion charges.
Dynamics of vesicle formation from lipid droplets: Mechanism and controllability
Authors: Wang Zilu , He Xuehao
Published: March 2009

A coarse-grained model developed by Marrink et al. [J. Phys. Chem. B 111, 7812 (2007)] is applied to investigate vesiculation of lipid [dipalmitoylphosphatidylcholine (DPPC)] droplets in water. Three kinds of morphologies of micelles are found with increasing lipid droplet size. When the initial lipid droplet is smaller, the equilibrium structure of the droplet is a spherical micelle. When the initial lipid droplet is larger, the lipid ball starts to transform into a disk micelle or vesicle. The mechanism of vesicle formation from a lipid ball is analyzed from the self-assembly of DPPC on the molecular level, and the morphological transition from disk to vesicle with increasing droplet size is demonstrated. Importantly, we discover that the transition point is not very sharp, and for a fixed-size lipid ball, the disk and vesicle appear with certain probabilities. The splitting phenomenon, i.e., the formation of a disk/vesicle structure from a lipid droplet, is explained by applying a hybrid model of the Helfrich membrane theory. The elastic module of the DPPC bilayer and the smallest size of a lipid droplet for certain formation of a vesicle are successfully predicted.
Vibrational solvatochromism and electrochromism: Coarse-grained models and their relationships
Authors: Cho Minhaeng
Published: March 2009

A theoretical description of vibrational solvatochromism and electrochromism is presented by using a coarse-grained model based on a distributed charge and multipole interaction theory. Solvatochromic frequency shift has been described by considering the interaction between distributed charges of a solute and electrostatic potential due to distributed charges of solvent molecules. Another approach was based on the expansion of the solvatochromic frequency shift in terms of solvent electric field and its gradient at distributed sites on solute. The relationship between these two approaches is elucidated and their validities are discussed. It is also shown that the distributed charge and multipole model for solvatochromism developed here can be used to describe vibrational Stark effects on frequency and transition dipole moment. The relationship between the vibrational Stark tuning rate and the parameters obtained from recent vibrational solvatochromism studies is clarified and used to determine the vibrational Stark tuning rates of a few stretching modes, which are then directly compared with experimentally measured values. We anticipate that the present theoretical model can be used to study a variety of vibrational solvatochromic and electrochromic phenomena and to extract critical information on local electrostatic environment around a small IR probe in solution or protein from linear and nonlinear IR spectroscopic studies.
Two-photon resonant second harmonic generation in atomic xeon
Authors: Shi Y. J. , Al-Basheer W. , Thompson R. I.
Published: March 2009

Vacuum ultraviolet (VUV) radiation at 124.8 nm (9.93 eV) was produced from two-photon resonant second harmonic generation (SHG) in a xeon gaseous medium and used to probe molecular samples of acetone, furan, thiophene, ammonia, and methane. The mass spectra recorded from the species with ionization energies below 9.93 eV were dominated by the parent ions. The parent ions were only observed when the incident UV radiation was tuned to resonate with the two-photon transition 5p5(P23/20)6p[1/2]0←5p6 S10 of Xe at 80 119.474 cm−1. The pressure dependence and the resonant nature of the parent ions observed support the mechanism for SHG as the ionization-initiated electric field induced SHG via the third-order nonlinear susceptibility χ(3), which is enhanced by the coupling between the 5p5(P23/20)6p[1/2]0 and the nearby 5p5(P23/20)5d[1/2]1 states of Xe atoms.
First principles study of magnetism in divalent Eu perovskites
Authors: Ranjan Rajeev , Nabi Hasan Sadat , Pentcheva Rossitza
Published: March 2009

A comparative first principles study has been carried out for EuLiH3 (ELH) and EuTiO3 (ETO) using the generalized gradient approximation +U approach. While ELH exhibits ferromagnetic ground state for all volumes, the magnetic ground state of ETO has the tendency to switch from G-type antiferromagnetic to a ferromagnetic state with change in volume. The marked difference in magnetic behavior and magnitude of the nearest neighbors exchange interaction of both the compounds are shown to be related to the difference in their respective electronic structure near the Fermi level. The Ti 3d states are shown to play predominant role in weakening the strength of the exchange interaction in ETO.
Re-entrant spiral magnetic order and ferroelectricity in Mn1−xFexWO4 (x=0.035)
Authors: Chaudhury R. P. , Lorenz B. , Wang Y. Q. , Sun Y. Y. , Chu C. W. , Ye F. , Fernandez-Baca J. , Mook H. , Lynn J.
Published: March 2009

We report the observation of a re-entrant spiral (noncollinear) magnetic order and ferroelectricity below 6 K in Mn0.965Fe0.035WO4 under applied magnetic fields above 3.6 T. At zero field, this compound shows a transition into the spiral magnetic and ferroelectric phase at 12 K, and it becomes paraelectric at 10.5 K with the entrance into the commensurate magnetic phase, which is the ground state at H=0. Under magnetic field above 3.6 T, however, the spiral magnetic phases with a larger FE polarization reappears below 6 K. The re-entrant magnetic/ferroelectric phase behavior is further studied by single crystal neutron scattering and the H-T phase diagram is completely resolved from neutron, dielectric constant, polarization, and magnetic measurements.
Diffusion-controlled and diffusionless crystal growth in liquid o-terphenyl near its glass transition temperature
Authors: Xi Hanmi , Sun Ye , Yu Lian
Published: March 2009

o -terphenyl is one of the organic liquids in which a fast mode of crystal growth is activated near the glass transition temperature Tg and continues deep in the glassy state. This growth mode, termed glass-crystal (GC), is not limited by molecular diffusion in the bulk liquid, in contrast to the diffusion-controlled growth at higher temperatures. The GC mode has been previously described as abruptly emerging near Tg and having a constant growth rate at a fixed temperature, two features important for testing its various explanations. We report here that the GC mode already exists in the equilibrium liquid of o-terphenyl up to 1.15Tg (Tg=246 K) in the form of loose, fast-growing fibers and that its growth rate is constant at Tg+2 K, but decreases by 30% in 10 h at Tg−13 K, during which time the glass’ fictive temperature decreases by 6 K. The slow down of GC growth becomes less noticeable over time so that fast growth is still observable after long annealing. The fiber growth, similar to the fully activated GC growth that yields compact spherulites, is also not limited by bulk diffusion. Crystal growth in the GC mode has a comparable activation energy as liquid desorption but a much faster rate, properties in common with polymorphic conversions. The time dependence of GC growth is not readily explained by the effect of physical aging on the thermodynamic driving force of crystallization, the liquid desorption, the primary structural relaxation, or a secondary relaxation. The secondary dielectric relaxation observed by dielectric spectroscopy in glassy o-terphenyl disappears too quickly for its molecular motions to be responsible for GC growth.
Nanoparticle networks as chemoselective sensing devices
Authors: Zimbovskaya Natalya A. , Pederson Mark R. , Blum Amy S. , Ratna Banahalli R. , Allen Reeshemah
Published: March 2009

We theoretically analyzed transport properties of a molecular network constructed of gold nanoparticles linked with oligophenylenevinulene (OPV) molecules. We showed that the conductance of such system was strongly reduced when trinitrotoluene (TNT) became attached to the OPV linkers in the network. The reported results are based on the ab initio electronic structure calculations. These results corroborate and elucidate experiments which revealed significant drops in the conductance the network while the latter was exposed to TNT vapors. The results suggest that the detected sensitivity of transport characteristics of the considered nanoparticle network to TNT may be used to design a sensing nanodevice.
Narrow escape time to a structured target located on the boundary of a microdomain
Authors: Reingruber Jürgen , Abad Enrique , Holcman David
Published: March 2009

The forward binding rate of chemical reactions is the reciprocal of the mean time for a Brownian molecule to hit its molecular target. When the target is embedded in the surface of a microdomain, this time is known as the narrow escape time, and it has been computed for various geometries. However, for large targets that extend from the surface far into the cytosol the classical computations do not apply and new ones are needed. In this work we generalize the narrow escape time formula to a three-dimensional spine attached to the boundary. We treat in detail the case of an ellipsoidal spine and validate our analysis by Brownian simulations. Finally, we compute the narrow escape time when the spine is uniformly covered by small partially absorbing disks and estimate the homogenized trapping rate of such a patchy surface.
Liquid-vapor equilibrium isotopic fractionation of water: How well can classical water models predict it?
Authors: Chialvo Ariel A. , Horita Juske
Published: March 2009

The liquid-vapor equilibrium isotopic fractionation of water is determined by molecular-based simulation, via Gibbs ensemble Monte Carlo and isothermal-isochoric molecular dynamics involving two radically different but realistic models, the extended simple point charge, and the Gaussian charge polarizable models. The predicted temperature dependence of the liquid-vapor equilibrium isotopic fractionation factors for H2O18∕H2O16, H2O17∕H2O16, and H2H1O16∕H21O16 are compared against the most accurate experimental datasets to assess the ability of these intermolecular potential models to describe quantum effects according to the Kirkwood–Wigner free energy perturbation ℏ2-expansion. Predictions of the vapor pressure isotopic effect for the H2O18∕H2O16 and H2O17∕H2O16 pairs are also presented in comparison with experimental data and two recently proposed thermodynamic modeling approaches. Finally, the simulation results are used to discuss some approximations behind the microscopic interpretation of isotopic fractionation based on the underlying rototranslational coupling.
Element-specific study of the temperature dependent magnetization of Co–Mn–Sb thin films
Authors: Schmalhorst J. , Ebke D. , Meinert M. , Thomas A. , Reiss G. , Arenholz E.
Published: March 2009

Magnetron sputtered thin Co–Mn–Sb films were investigated with respect to their element-specific magnetic properties. Stochiometric Co1Mn1Sb1 crystallized in the C1b structure has been predicted to be half-metallic and is therefore of interest for spintronic applications. It should show a characteristic antiferromagnetic coupling of the Mn and Co magnetic moments and a transition temperature TC of about 480 K. Although the observed transition temperature of our 20 nm thick Co32.4Mn33.7Sb33.8, Co37.7Mn34.1Sb28.2, and Co43.2Mn32.6Sb24.2 films is in quite good agreement with the expected value, we found a ferromagnetic coupling of the Mn and Co magnetic moments which indicates that the films do not crystallize in the C1b structure and are probably not fully spin polarized. The ratio of the Co and Mn moments does not change up to the transition temperature and the temperature dependence of the magnetic moments can be well described by the mean-field theory.
Surface optical phonon and A1(LO) in ZnO submicron crystals probed by Raman scattering: Effects of morphology and dielectric coating
Authors: Liu H. F. , Tripathy S. , Hu G. X. , Gong H.
Published: March 2009

The authors studied the surface optical phonon and A1(LO) in ZnO submicron crystals as well as ZnO single crystals with submicron surface structures by employing ultraviolet Raman scattering. The small variation in Raman frequency of A1(LO), when the growth condition is changed, is mainly caused by the crystal imperfection via two mechanisms: one is the frequency lowering by native defects and the other is the frequency increasing due to the tilt of c-axis of ZnO crystals away from the surface normal direction that leads to the mixing of A1(LO) and E1(LO). The evolution of Raman features, before and after dielectric coatings, in conjunction with the photoluminescence, provides clear-cut evidence for the observation of a surface optical phonon. The frequency of the observed surface mode is lowered by the existence of surface states, and the surface states can be effectively reduced by the dielectric coatings.
Excitation of low-n toroidicity induced Alfvén eigenmodes by energetic particles in global gyrokinetic tokamak plasmas
Authors: Nishimura Y.
Published: March 2009

The first linear global electromagnetic gyrokinetic particle simulation on the excitation of toroidicity induced Alfvén eigenmode (TAE) by energetic particles is reported. It is shown that the long wavelength magnetohydrodynamic instabilities can be studied by the gyrokinetic particle simulation. With an increase in the energetic particle pressure, the TAE frequency moves down into the lower continuum together with an increase in the linear growth rate.
Dependence of resistance drift on the amorphous cap size in phase change memory arrays
Authors: Braga Stefania , Cabrini Alessandro , Torelli Guido
Published: March 2009

Multilevel programming in phase change memories (PCMs) requires understanding of the phenomena which affect the stability of the programmed resistance levels. Although the Ge2Sb2Te5 (GST alloy) crystallization process has been extensively studied, further analysis is needed to characterize the drift of low-field amorphous-GST resistance. In this paper, we carry out a statistical analysis on an array of PCM cells so as to investigate the drift dynamics of intermediate GST resistance states. Our experimental results reveal the dependence of the drift dynamics exponent on the thickness of the amorphous cap inside the GST layer, which is ascribed to the different stresses.
Improved double planar probe data analysis technique
Authors: Ghim(Kim) Young-chul , Hershkowitz Noah
Published: March 2009

Plasma electron number density and ion number density in a dc multidipole weakly collisional Ar plasma are measured with a single planar Langmuir probe and a double planar probe, respectively. A factor of two discrepancy between the two density measurements is resolved by applying Sheridan’s empirical formula [T. E. Sheridan, Phys. Plasmas 7, 3084 (2000)] for sheath expansion to the double probe data.
Mechanism of exciton dephasing in a single carbon nanotube studied by photoluminescence spectroscopy
Authors: Yoshikawa Kohei , Matsunaga Ryusuke , Matsuda Kazunari , Kanemitsu Yoshihiko
Published: March 2009

We studied the temperature and chirality dependence of the photoluminescence (PL) linewidth of single carbon nanotubes to clarify the mechanism of exciton dephasing. The PL linewidth of a single carbon nanotube broadened linearly with increasing temperature, indicating that the linewidth and exciton dephasing are determined through exciton-phonon interactions. From the chirality dependence of the PL linewidth, we concluded that exciton dephasing is caused by both the longitudinal acoustic and twisting phonon modes.
Measurements on quantum capacitance of individual single walled carbon nanotubes
Authors: Dai Junfeng , Li Jun , Zeng Hualing , Cui Xiaodong
Published: March 2009

We report measurements of the quantum capacitance of individual semiconducting and small band gap single walled carbon nanotubes (SWNTs). The observed quantum capacitance, 82 aF/μm for a semiconducting SWNT with chiral index (16,8) and 10.3 aF/μm for a small band gap SWNT upon Fermi level lying at the first subband are remarkably smaller than those originating from the density of states. We attribute the discrepancy to a strong electron correlation in SWNTs and derive the Luttinger parameter g of 0.25–0.3 for the (16,8) SWNT and of 0.32 for a small band gap SWNT.
Broadside excitation of surface plasmon waveguides on Cytop
Authors: Daviau Richard , Lisicka-Skrzek Ewa , Tait R. Niall , Berini Pierre
Published: March 2009

Long-range surface plasmon waveguides consisting of a Au stripe on Cytop, covered with an index-matched aqueous solution, are described and characterized. The waveguides are tested using a broadside coupling technique, whereby tapered single-mode fibers are positioned in direct contact with the stripe such that the slow mode of the fiber couples through partial modal overlap to the long-range surface plasmon. Attenuation measurements obtained at λ0=1310 nm agree well with theory, thus validating the waveguide fabrication and experimental techniques. The waveguides are useful for (bio)chemical sensing and the broadside coupling technique is useful for on-wafer optical probing.
Electronic coupling of colloidal CdSe nanocrystals monitored by thin-film positron-electron momentum density methods
Authors: Eijt S. W. H. , Mijnarends P. E. , van Schaarenburg L. C. , Houtepen A. J. , Vanmaekelbergh D. , Barbiellini B. , Bansil A.
Published: March 2009

The effect of temperature controlled annealing on the confined valence electron states in CdSe nanocrystal arrays, deposited as thin films, was studied using two-dimensional angular correlation of annihilation radiation. A reduction in the intensity by ∼35% was observed in a feature of the positron annihilation spectrum upon removal of the pyridine capping molecules above 200 °C in a vacuum. This reduction is explained by an increased electronic interaction of the valence orbitals of neighboring nanocrystals, induced by the formation of inorganic interfaces. Partial evaporation of the nanoporous CdSe layer and additional sintering into a polycrystalline thin film were observed at a relatively low temperature of ∼486 °C.
Ultrawideband microwave noise filter: Hybrid antiferromagnet/ferromagnet exchange-coupled multilayers
Authors: Phuoc Nguyen N. , Xu Feng , Ong C. K.
Published: March 2009

Hybrid multilayers of [FeNi–FeMn]N/[MnIr–FeCo]N deposited onto flexible substrates oriented for wideband noise filters were fabricated using rf sputtering deposition. By combining the two types of multilayers with various thicknesses, where FeNi–FeMn is designed for the low frequency range and MnIr–FeCo for the high frequency range, one can realize a hybrid thin film for wideband noise filters. Its broad range from 1.5 to 7 GHz (the absorption width where the reflection loss is less than −10 dB) makes this hybrid thin film promising for future applications.
Tailoring the electronic properties of GaxIn1−xP beyond simply varying alloy composition
Authors: Zhang Yong , Jiang C.-S. , Friedman D. J. , Geisz J. F. , Mascarenhas A.
Published: March 2009

Spontaneous ordering in GaxIn1−xP provides the possibility of tuning electronic structure and improving transport properties. A quasiperiodic twinning structure of two ordered variants offers additional flexibilities in designing the material properties. The superstructure is shown to have distinctively different electronic and electrical properties from the single-variant ordered structure, as revealed in polarized elecroreflectance and cross-sectional scanning Kelvin probe force microscopy measurements. The entire potentially accessible range of the “direct” bandgap is defined for this alloy system, and thus the optimal bandgap for any intended application can be achieved through the interplay of the effects of alloying, ordering, and domain structure engineering.
Static and optical field enhancement in metallic nanotips studied by two-photon photoemission microscopy and spectroscopy excited by picosecond laser pulses
Authors: Tsujino S. , le Pimpec F. , Raabe J. , Buess M. , Dehler M. , Kirk E. , Gobrecht J. , Wrulich A.
Published: March 2009

The authors studied the photoemission from molybdenum nanotip arrays with controlled apex curvatures by photoelectron microscopy and spectroscopy excited by 10 ps visible laser pulses under dc electric field. While two-photon photoemission microscopy demonstrates the enhancement of photoabsorption at the sharp tip apex, spatially resolved analysis of the photoelectron energy revealed anomalous energy distribution that is ascribed to the dc field enhancement and resultant barrier reduction at the tip apex. The results show the applicability of photoelectron microscopy and spectroscopy to study the distribution of dc and optical electric field enhancement in field-emitter arrays.
Effect of oxygen content and superconductivity on the nonvolatile resistive switching in YBa2Cu3O6+x/Nb-doped SrTiO3 heterojunctions
Authors: Zhang H. J. , Zhang X. P. , Shi J. P. , Tian H. F. , Zhao Y. G.
Published: March 2009

The authors report on the resistive switching effect in YBa2Cu3O6+x/Nb-doped SrTiO3 heterojunctions. The current-voltage curves of these heterojunctions show hysteresis, which increases with decreasing temperature and oxygen content. Multiresistance states are realized by voltage pulses with different amplitudes. The relaxation of the junction current after switching follows the Curie–Von Schweidler law. More interestingly, the resistance of the low resistance state for the heterojunction shows a metallic behavior with a remarkable drop at Tc. The results were discussed in terms of the trapping-detrapping process via oxygen vacancies near the interface of the heterojunction and the conducting filaments through the junction barrier.
Physical properties of amorphous InGaZnO4 films doped with Mn
Authors: Liu Shiu-Jen , Fang Hau-Wei , Su Shih-Hao , Li Chia-Hung , Cherng Jyh-Shiarn , Hsieh Jang-Hsing , Juang Jenh-Yih
Published: March 2009

Amorphous InGaZnO4 (a-IGZO) films doped with various concentrations of Mn have been fabricated by using pulsed-laser deposition technique. Optical, electrical, and magnetic properties of the prepared Mn-doped a-IGZO films were investigated. The resistivity, carrier concentration, and carrier mobility of the a-IGZO films were found to be, respectively, increased, decreased, and enhanced by Mn doping. Moreover, the optical transmission is slightly increased in the visible range and the optical band gaps are not affected in the Mn-doped films. Room-temperature ferromagnetism has been observed in the field-dependent magnetization measurements.
Triple Shockley type stacking faults in 4H-SiC epilayers
Authors: Feng Gan , Suda Jun , Kimoto Tsunenobu
Published: March 2009

4 H -SiC epilayers have been characterized by microphotoluminescence (micro-PL) spectroscopy and micro-PL intensity mapping at room temperature. A type of stacking fault (SF) with a peak emission wavelength at 480 nm (2.58 eV) has been identified. The shape of this SF is triangular revealed by the micro-PL intensity mapping. Conventional and high-resolution transmission electron microscopies have been carried out to investigate the structure of this SF. Its stacking sequence is determined as (3,5) in Zhdanov’s notation, which is consistent with that of the triple Shockley SF. The formation mechanism of this SF is also discussed.
Multifunctionality attributed to the self-doping in polycrystalline La0.9MnO3: Coexistence of large magnetoresistance and magnetocaloric effect
Authors: Patra M. , De K. , Majumdar S. , Giri S.
Published: March 2009

We report the multifunctionality near room temperature attributed to the self-doping in polycrystalline La0.9MnO3. The peak in the temperature dependence of magnetoresistance (MR) and change of magnetic entropy (ΔSM) are observed at 254 K with −MR=55% at 50 kOe and −SM=4.9 J/kg K at 20 kOe where the Curie temperature and metal-insulator transition coexist at 254 K associated with a first order transition. The correlation between resistivity and ΔSM is observed in a limited region around TC. Here ΔSM is close to the largest reported values in manganites, suggesting that the material is interesting for multiple applications.
Colossal electroresistance and colossal magnetoresistive step in paramagnetic insulating phase of single crystalline bilayered manganite (La0.4Pr0.6)1.2Sr1.8Mn2O7
Authors: Yamato Y. , Matsukawa M. , Murano Y. , Suryanarayanan R. , Nimori S. , Apostu M. , Revcolevschi A. , Koyama K. , Kobayashi N.
Published: March 2009

We report a significant decrease in the low-temperature resistance induced by the application of an electric current on the ab-plane in the paramagnetic insulating (PMI) state of (La0.4Pr0.6)1.2Sr1.8Mn2O7. A colossal electroresistance effect attaining −95% is observed at lower temperatures. A colossal magnetoresistive step appears near 5 T at low temperatures below 10 K, accompanied by an ultrasharp width of the insulator-metal transition. Injection of higher currents to the crystal and magnetic field cooling process cause a disappearance of the steplike transition. These findings have a close relationship with the presence of the short-range charge-ordered clusters pinned within the PMI matrix of the crystal studied.
Surface selective deposition of molecular semiconductors for solution-based integration of organic field-effect transistors
Authors: Minari Takeo , Kano Masataka , Miyadera Tetsuhiko , Wang Sui-Dong , Aoyagi Yoshinobu , Tsukagoshi Kazuhito
Published: March 2009

A bottom-up fabrication technique for the preparation of self-organized organic field-effect transistors (OFETs) on flexible plastic substrates is presented. Solution-based self-organization of OFETs is achieved by patterning the insulator surface with solution-wettable and unwettable regions. The proposed method satisfies several important requirements of printable electronics, including reduction in energy consumption, minimization of facilities, and the on-demand use of molecular materials. Self-organized OFETs display an average mobility of 0.53 cm2/(V s), on/off ratio of 109, and subthreshold slope of 0.18 V/dec, with near-zero and narrowly distributed threshold voltage. An inverter circuit prepared using these devices is demonstrated with high signal gain.
Field effect enhanced quantum dot resonant tunneling diode for high dynamic range light detection
Authors: Wang W. P. , Hou Y. , Li N. , Li Z. F. , Chen X. S. , Lu W. , Wang W. X. , Chen H. , Zhou J. M. , Wu E. , Zeng H. P.
Published: March 2009

A field effect enhanced quantum dot resonant tunneling diode is proposed and demonstrated to improve the detection dynamic range for low light imaging application. Using the cross-wire device geometry, a lateral two dimensional electron gas (2DEG) current is formed in the quantum well channel together with the normal resonant tunneling current for quantum dot modulation. A peak photoresponsivity of the order of 1010 A/W and a light detection saturation level up to 105 photons per second at 77 K are achieved when the 2DEG current makes the main photocurrent contribution.
Dislocation density evolution during high pressure torsion of a nanocrystalline Ni–Fe alloy
Authors: Wang Y. B. , Ho J. C. , Cao Y. , Liao X. Z. , Li H. Q. , Zhao Y. H. , Lavernia E. J. , Ringer S. P. , Zhu Y. T.
Published: March 2009

High-pressure torsion (HPT) induced dislocation density evolution in a nanocrystalline Ni-20 wt %Fe alloy was investigated using x-ray diffraction and transmission electron microscopy. Results suggest that the dislocation density evolution is fundamentally different from that in coarse-grained materials. The HPT process initially reduces the dislocation density within nanocrystalline grains and produces a large number of dislocations located at small-angle subgrain boundaries that are formed via grain rotation and coalescence. Continuing the deformation process eliminates the subgrain boundaries but significantly increases the dislocation density in grains. This phenomenon provides an explanation of the mechanical behavior of some nanostructured materials.
Transverse surface waves in a 6 mm piezoelectric material carrying a prestressed metal layer of finite thickness
Authors: Qian Zheng-Hua , Jin Feng , Lu Tian-Jian , Kishimoto Kikuo
Published: March 2009

The propagation of transverse surface waves in a piezoelectric material carrying a prestressed metal layer of finite thickness is investigated analytically. The dispersion equation is solved in closed form for class 6 mm piezoelectric materials and the conditions for the existence of various wave modes are obtained. Numerical examples are presented for an aluminum, gold, or zinc layer on a PZT-4 ceramic substrate. The presence of initial stress can extend or shorten the range of phase velocity within which a nonleaky but dispersive mode exists. The dependence of phase velocity on initial stress opens a new window for designing acoustic wave devices.
Adverse metabolic and cardiovascular consequences of circadian misalignment
Authors: Scheer Frank A. J. L. , Hilton Michael F. , Mantzoros Christos S. , Shea Steven A.
Published: March 2009

There is considerable epidemiological evidence that shift work is associated with increased risk for obesity, diabetes, and cardiovascular disease, perhaps the result of physiologic maladaptation to chronically sleeping and eating at abnormal circadian times. To begin to understand underlying mechanisms, we determined the effects of such misalignment between behavioral cycles (fasting/feeding and sleep/wake cycles) and endogenous circadian cycles on metabolic, autonomic, and endocrine predictors of obesity, diabetes, and cardiovascular risk. Ten adults (5 female) underwent a 10-day laboratory protocol, wherein subjects ate and slept at all phases of the circadian cycle—achieved by scheduling a recurring 28-h “day.” Subjects ate 4 isocaloric meals each 28-h “day.” For 8 days, plasma leptin, insulin, glucose, and cortisol were measured hourly, urinary catecholamines 2 hourly (totaling ≈1,000 assays/subject), and blood pressure, heart rate, cardiac vagal modulation, oxygen consumption, respiratory exchange ratio, and polysomnographic sleep daily. Core body temperature was recorded continuously for 10 days to assess circadian phase. Circadian misalignment, when subjects ate and slept ≈12 h out of phase from their habitual times, systematically decreased leptin (−17%,
P
< 0.001), increased glucose (+6%,
P
< 0.001) despite increased insulin (+22%,
P
= 0.006), completely reversed the daily cortisol rhythm (
P
< 0.001), increased mean arterial pressure (+3%,
P
= 0.001), and reduced sleep efficiency (−20%,
P
< 0.002). Notably, circadian misalignment caused 3 of 8 subjects (with sufficient available data) to exhibit postprandial glucose responses in the range typical of a prediabetic state. These findings demonstrate the adverse cardiometabolic implications of circadian misalignment, as occurs acutely with jet lag and chronically with shift work.
Glatiramer acetate increases IL-1 receptor antagonist but decreases T cell-induced IL-1β in human monocytes and multiple sclerosis
Authors: Burger Danielle , Molnarfi Nicolas , Weber Martin S. , Brandt Karim J. , Benkhoucha Mahdia , Gruaz Lyssia , Chofflon Michel , Zamvil Scott S. , Lalive Patrice H.
Published: March 2009

Mechanisms of action as well as cellular targets of glatiramer acetate (GA) in multiple sclerosis (MS) are still not entirely understood. IL-1β is present in CNS-infiltrating macrophages and microglial cells and is an important mediator of inflammation in experimental autoimmune encephalitis (EAE), the MS animal model. A natural inhibitor of IL-1β, the secreted form of IL-1 receptor antagonist (sIL-1Ra) improves EAE disease course. In this study we examined the effects of GA on the IL-1 system. In vivo, GA treatment enhanced sIL-1Ra blood levels in both EAE mice and patients with MS, whereas IL-1β levels remained undetectable. In vitro, GA per se induced the transcription and production of sIL-1Ra in isolated human monocytes. Furthermore, in T cell contact-activated monocytes, a mechanism relevant to chronic inflammation, GA strongly diminished the expression of IL-1β and enhanced that of sIL-1Ra. This contrasts with the effect of GA in monocytes activated upon acute inflammatory conditions. Indeed, in LPS-activated monocytes, IL-1β and sIL-1Ra production were increased in the presence of GA. These results demonstrate that, in chronic inflammatory conditions, GA enhances circulating sIL-1Ra levels and directly affects monocytes by triggering a bias toward a less inflammatory profile, increasing sIL-1Ra while diminishing IL-1β production. This study sheds light on a mechanism that is likely to participate in the therapeutic effects of GA in MS.
Requirements for NuMA in maintenance and establishment of mammalian spindle poles
Authors: Silk Alain D. , Holland Andrew J. , Cleveland Don W.
Published: March 2009

Microtubules of the mitotic spindle in mammalian somatic cells are focused at spindle poles, a process thought to include direct capture by astral microtubules of kinetochores and/or noncentrosomally nucleated microtubule bundles. By construction and analysis of a conditional loss of mitotic function allele of the nuclear mitotic apparatus (NuMA) protein in mice and cultured primary cells, we demonstrate that NuMA is an essential mitotic component with distinct contributions to the establishment and maintenance of focused spindle poles. When mitotic NuMA function is disrupted, centrosomes provide initial focusing activity, but continued centrosome attachment to spindle fibers under tension is defective, and the maintenance of focused kinetochore fibers at spindle poles throughout mitosis is prevented. Without centrosomes and NuMA, initial establishment of spindle microtubule focusing completely fails. Thus, NuMA is a defining feature of the mammalian spindle pole and functions as an essential tether linking bulk microtubules of the spindle to centrosomes.
Syndecan-1 regulates αvβ3 and αvβ5 integrin activation during angiogenesis and is blocked by synstatin, a novel peptide inhibitor
Authors: Beauvais DeannaLee M. , Ell Brian J. , McWhorter Andrea R. , Rapraeger Alan C.
Published: March 2009

Syndecan-1 (Sdc1) is a matrix receptor shown to associate via its extracellular domain with the αvβ3 and αvβ5 integrins, potentially regulating cell adhesion, spreading, and invasion of cells expressing these integrins. Using Sdc1 deletion mutants expressed in human mammary carcinoma cells, we identified the active site within the Sdc1 core protein and derived a peptide inhibitor called synstatin (SSTN) that disrupts Sdc1's interaction with these integrins. Because the αvβ3 and αvβ5 integrins are critical in angiogenesis, a process in which a role for Sdc1 has been uncertain, we used human vascular endothelial cells in vitro to show that the Sdc1 regulatory mechanism is also required for integrin activation on these cells. We found Sdc1 expressed in the vascular endothelium during microvessel outgrowth from aortic explants in vitro and in mouse mammary tumors in vivo. Moreover, we show that SSTN blocks angiogenesis in vitro or when delivered systemically in a mouse model of angiogenesis in vivo, and impairs mammary tumor growth in an orthotopic mouse tumor model. Thus, Sdc1 is a critical regulator of these two important integrins during angiogenesis and tumorigenesis, and is inhibited by the novel SSTN peptide.
Sport and arrhythmias: summary of an international symposium
Authors: Giada Franco , Barold Serge S. , Biffi Alessandro , Piccoli Bruno De , Delise Pietro , El-Sherif Nabil , Gold Michael R. , Gorenek Bulent , Grubb Blair , Inama Giuseppe , Kautzner Josef , Molina Luis , Olshansky Brian , Pelliccia Antonio , Thiene Gaetano , Wellens Hein , Wolpert Christian , Zeppilli Paolo , Raviele Antonio , Heidbuchel Hein
Published: March 2009

This article is the report of an International Symposium endorsed by the European Society of Cardiology, held within the Venice Arrhythmias 2007: 10th International Workshop on Cardiac Arrhythmias (Venice, October 2007). The topics of the Symposium are the following: how to stratify the risk of sudden death in the athletes; the role of different diagnostic examinations in the risk stratification of sudden death in the athletes; controversies on arrhythmias and sport; and exercise prescription in patients with arrhythmias. Eur J Cardiovasc Prev Rehabil14:707-714 © 2007 The European Society of Cardiology
Safety and Symptom Improvement With Esomeprazole in Adolescents With Gastroesophageal Reflux Disease
Authors: Gold Benjamin D , Gunasekaran Thirumazhisai , Tolia Vasundhara , Wetzler Graciela , Conter Howard , Traxler Barry , Illueca Marta
Published: March 2009

Objectives:

The primary objective was to assess the safety of esomeprazole 20 or 40 mg once daily in adolescents with clinically diagnosed gastroesophageal reflux disease (GERD). A secondary aim was to assess changes in GERD symptoms after esomeprazole therapy.

Patients and Methods:

In this multicenter, randomized, double‐blind study, adolescents ages 12 to 17 years inclusive received esomeprazole 20 or 40 mg once daily for 8 weeks. Adverse events and changes in clinical parameters (eg, physical examination, laboratory measurements) were evaluated to assess safety. Patients or their parents or guardians scored symptom severity daily, and investigators scored overall GERD symptom severity every 2 weeks using a 4‐point scale.

Results:

In the 148 adolescents with safety data, treatment‐related and non–treatment‐related adverse events were reported by 75% and 78% of patients in the esomeprazole 20‐ and 40‐mg groups, respectively. Twenty‐two patients (14.9%) experienced adverse events that were considered related to treatment; the most common were headache (8%, 12/148), abdominal pain (3%, 4/148), nausea (2%, 3/148), and diarrhea (2%, 3/148). No serious adverse events or clinically important findings in other safety assessments were observed. At baseline, 68% (100/147) had heartburn, 63% (93/147) had epigastric pain, 57% (84/147) had acid regurgitation, and 15% (22/147) had vomiting symptoms. Symptom scores decreased significantly in both the esomeprazole 20‐mg and 40‐mg groups by the final study week (P < 0.0001). Investigators rated 63.1% (94/149) of the patients as having moderate or severe symptoms at baseline; at the final visit, this percentage decreased significantly to 9.3% (13/140; P < .0001).

Conclusions:

In adolescent patients with GERD, esomeprazole 20 or 40 mg daily for 8 weeks was well tolerated, and GERD‐related symptoms were significantly reduced from baseline values in both groups.
Incorporation into the prereplicative complex activates the Mcm2–7 helicase for Cdc7–Dbf4 phosphorylation
Authors: Francis Laura I. , Randell John C.W. , Takara Thomas J. , Uchima Lilen , Bell Stephen P.
Published: March 2009

The essential S-phase kinase Cdc7–Dbf4 acts at eukaryotic origins of replication to trigger a cascade of protein associations that activate the Mcm2–7 replicative helicase. Also known as Dbf4-dependent kinase (DDK), this kinase preferentially targets chromatin-associated Mcm2–7 complexes that are assembled on the DNA during prereplicative complex (pre-RC) formation. Here we address the mechanisms that control the specificity of DDK action. We show that incorporation of Mcm2–7 into the pre-RC increased the level and changes the specificity of DDK phosphorylation of this complex. In the context of the pre-RC, DDK preferentially targets a conformationally distinct subpopulation of Mcm2–7 complexes that is tightly linked to the origin DNA. This targeting requires DDK to tightly associate with Mcm2–7 complexes in a Dbf4-dependent manner. Importantly, we find that DDK association with and phosphorylation of origin-linked Mcm2–7 complexes require prior phosphorylation of the pre-RC. Our findings provide insights into the mechanisms that ensure that DDK action is spatially and temporally restricted to the origin-bound Mcm2–7 complexes that will drive replication fork movement during S phase and suggest new mechanisms to regulate origin activity.