bluuebunny/crossref_metadata_2025 huggingface dataset:
The human Suv3 helicase interacts with replication protein A and flap endonuclease 1 in the nucleus
Authors: Venø Susanne T. , Kulikowicz Tomasz , Pestana Cezar , Stepien Piotr P. , Stevnsner Tinna , Bohr Vilhelm A.
Published: August 2011

The hSuv3 (human Suv3) helicase has been shown to be a major player in mitochondrial RNA surveillance and decay, but its physiological role might go beyond this functional niche. hSuv3 has been found to interact with BLM (Bloom's syndrome protein) and WRN (Werner's syndrome protein), members of the RecQ helicase family involved in multiple DNA metabolic processes, and in protection and stabilization of the genome. In the present study, we have addressed the possible role of hSuv3 in genome maintenance by examining its potential association with key interaction partners of the RecQ helicases. By analysis of hSuv3 co-IP (co-immunoprecipitation) complexes, we identify two new interaction partners of hSuv3: the RPA (replication protein A) and FEN1 (flap endonuclease 1). Utilizing an in vitro biochemical assay we find that low amounts of RPA inhibit helicase activity of hSuv3 on a forked substrate. Another single-strand-binding protein, mtSSB (mitochondrial single-strand-binding protein), fails to affect hSuv3 activity, indicating that the functional interaction is specific for hSuv3 and RPA. Further in vitro studies demonstrate that the flap endonuclease activity of FEN1 is stimulated by hSuv3 independently of flap length. hSuv3 is generally thought to be a mitochondrial helicase, but the physical and functional interactions between hSuv3 and known RecQ helicase-associated proteins strengthen the hypothesis that hSuv3 may play a significant role in nuclear DNA metabolism as well.
Protein kinase D controls voluntary-running-induced skeletal muscle remodelling
Authors: Ellwanger Kornelia , Kienzle Christine , Lutz Sylke , Jin Zheng-Gen , Wiekowski Maria T. , Pfizenmaier Klaus , Hausser Angelika
Published: August 2011

Skeletal muscle responds to exercise by activation of signalling pathways that co-ordinate gene expression to sustain muscle performance. MEF2 (myocyte enhancer factor 2)-dependent transcriptional activation of MHC (myosin heavy chain) genes promotes the transformation from fast-twitch into slow-twitch fibres, with MEF2 activity being tightly regulated by interaction with class IIa HDACs (histone deacetylases). PKD (protein kinase D) is known to directly phosphorylate skeletal muscle class IIa HDACs, mediating their nuclear export and thus derepression of MEF2. In the present study, we report the generation of transgenic mice with inducible conditional expression of a dominant-negative PKD1kd (kinase-dead PKD1) protein in skeletal muscle to assess the role of PKD in muscle function. In control mice, long-term voluntary running experiments resulted in a switch from type IIb+IId/x to type IIa plantaris muscle fibres as measured by indirect immunofluorescence of MHCs isoforms. In mice expressing PKD1kd, this fibre type switch was significantly impaired. These mice exhibited altered muscle fibre composition and decreased running performance compared with control mice. Our findings thus indicate that PKD activity is essential for exercise-induced MEF2-dependent skeletal muscle remodelling in vivo.
Alternative pathways of dehydroascorbic acid degradation in vitro and in plant cell cultures: novel insights into vitamin C catabolism
Authors: Parsons Harriet T. , Yasmin Tayyaba , Fry Stephen C.
Published: August 2011

L-Ascorbate catabolism involves reversible oxidation to DHA (dehydroascorbic acid), then irreversible oxidation or hydrolysis. The precursor–product relationships and the identity of several major DHA breakdown products remained unclear. In the presence of added H2O2, DHA underwent little hydrolysis to DKG (2,3-dioxo-L-gulonate). Instead, it yielded OxT (oxalyl L-threonate), cOxT (cyclic oxalyl L-threonate) and free oxalate (~6:1:1), essentially simultaneously, suggesting that all three product classes independently arose from one reactive intermediate, proposed to be cyclic-2,3-O-oxalyl-L-threonolactone. Only with plant apoplastic esterases present were the esters significant precursors of free oxalate. Without added H2O2, DHA was slowly hydrolysed to DKG. Downstream of DKG was a singly ionized dicarboxy compound (suggested to be 2-carboxy-L-xylonolactone plus 2-carboxy-L-lyxonolactone), which reversibly de-lactonized to a dianionic carboxypentonate. Formation of these lactones and acid was minimized by the presence of residual unreacted ascorbate. In vivo, the putative 2-carboxy-L-pentonolactones were relatively stable. We propose that DHA is a branch-point in ascorbate catabolism, being either oxidized to oxalate and its esters or hydrolysed to DKG and downstream carboxypentonates. The oxidation/hydrolysis ratio is governed by reactive oxygen species status. In vivo, oxalyl esters are enzymatically hydrolysed, but the carboxypentonates are stable. The biological roles of these ascorbate metabolites invite future exploration.
Orbital Wall Reconstruction with Titanium Mesh: Retrospective Study of 24 Patients
Authors: Gabrielli Mario Francisco , Monnazzi Marcelo Silva , Passeri Luis Augusto , Carvalho Waldner Ricardo , Gabrielli Marisa , Hochuli-Vieira Eduardo
Published: August 2011

The aim of this study was to evaluate the efficacy and safety of traumatic orbital defect reconstruction with titanium mesh. A retrospective study was made. Evaluations were made after a minimum postoperative follow-up of 12 months, looking for the main complications. Twenty-four patients were included in this evaluation; 19 were male (79.1%) and 5 (20.8%) were female. The main injury etiology was vehicle accidents (50%) followed by other causes. Fourteen patients (58.3%) presented orbital floor fractures, and 10 had more than one wall fractured (41.6%). Permanent infraorbital nerve hypoesthesia was observed in two patients (8.3%), enophthalmos occurred in five patients (20.8%), and exophthalmos was found in two patients (8.3%). Four patients (16.6%) still presented evidence of residual prolapsed intraorbital content, and one of those needed further surgical correction; sinusitis occurred in one patient (4.1%). Titanium mesh is a reliable option for orbital reconstruction, despite some complications found in this sample.
Droplet collisions and interaction with the turbulent flow within a two-phase wind tunnel
Authors: Bordás Róbert , Hagemeier Thomas , Wunderlich Bernd , Thévenin Dominique
Published: August 2011

Experiments in wind tunnels concerning meteorological issues are not very frequent in the literature. However, such experiments might be essential, for instance for a careful investigation of droplet-droplet interactions in turbulent flows. This issue is crucial for many configurations, in particular to understand warm rain initiation. It is clearly impossible to completely reproduce cloud turbulence within a wind tunnel due to the enormous length scales involved. Nevertheless, it is not necessary to recover the whole spectrum in order to quantify droplet interactions. It is sufficient for this purpose to account correctly for the relevant properties only. In the present paper, these properties and a methodology for setting those in a two-phase wind tunnel are first described. In particular, droplet size and number density, velocities, turbulent kinetic energy, k, and its dissipation rate, ɛ, are suitably reproduced, as demonstrated by non-intrusive measurement techniques. A complete experimental characterization of the air and droplet properties is freely available in a database accessible at http://www.ovgu.de/isut/lss/metstroem. Finally, quantifications of droplet collision rates and comparisons with theoretical predictions are presented, showing that measured collision rates are higher, typically by a factor of 2 to 5. These results demonstrate that model modifications are needed to estimate correctly droplet collision probabilities in turbulent flows
Measurements of the phase transition and the average length of the density fluctuation under supercritical fluid using micromechanical resonators
Authors: Toda Masaya , Fujii Takashi , Yoshida Atsushi , Hashida Toshiyuki , Ono Takahito
Published: August 2011

This paper presents an original method to measure the phase transition and macroscopic density fluctuation of supercritical carbon dioxide using a resonant microcantilever beam. There is a significant reduction of the resonant frequency near the phase transition point where the density and viscosity of carbon dioxide exhibit large variations, while the vibration amplitude of the micromechanical resonator displayed a large shift up due to generation of microscopic density fluctuation. The average length of the density fluctuation of supercritical fluid could be calculated from this large shift of the vibration amplitude and the value is in the range of millimeter.
Numerical study of the effective magnetocrystalline anisotropy and magnetostriction in polycrystalline FeGa films
Authors: Dean Julian , Bryan M. T. , Morley N. A. , Hrkac G. , Javed A. , Gibbs M. R. J. , Allwood D. A.
Published: August 2011

The high interest in FeGa films is due to the high magnetostriction present in single crystal thin films. There is, however, significant reduction in the magnetostriction when grown using sputtering. The reduction is explained here using finite element analysis by considering the local magnetocrystalline and magnetoelastic behavior of the grains within the sample. It is shown that, if the saturation magnetostrictive constant for each grain in a polycrystalline structure is of the order of 400 ppm, this is reduced to less than 90 ppm when the crystallites are randomly orientated. Furthermore, the inherent stress due to the sample fabrication leads to an increase in the anisotropy field. This work suggests that, with low stress fabrication and aligning the in-plane orientation of the crystallites, the potential in unlocking FeGa as a thin film for sensory applications can be realised.
Experimental and modeling analysis of fast ionization wave discharge propagation in a rectangular geometry
Authors: Takashima Keisuke , Adamovich Igor V. , Xiong Zhongmin , Kushner Mark J. , Starikovskaia Svetlana , Czarnetzki Uwe , Luggenhölscher Dirk
Published: August 2011

Fast ionization wave (FIW), nanosecond pulse discharge propagation in nitrogen and helium in a rectangular geometry channel/waveguide is studied experimentally using calibrated capacitive probe measurements. The repetitive nanosecond pulse discharge in the channel was generated using a custom designed pulsed plasma generator (peak voltage 10–40 kV, pulse duration 30–100 ns, and voltage rise time ∼1 kV/ns), generating a sequence of alternating polarity high-voltage pulses at a pulse repetition rate of 20 Hz. Both negative polarity and positive polarity ionization waves have been studied. Ionization wave speed, as well as time-resolved potential distributions and axial electric field distributions in the propagating discharge are inferred from the capacitive probe data. ICCD images show that at the present conditions the FIW discharge in helium is diffuse and volume-filling, while in nitrogen the discharge propagates along the walls of the channel. FIW discharge propagation has been analyzed numerically using quasi-one-dimensional and two-dimensional kinetic models in a hydrodynamic (drift-diffusion), local ionization approximation. The wave speed and the electric field distribution in the wave front predicted by the model are in good agreement with the experimental results. A self-similar analytic solution of the fast ionization wave propagation equations has also been obtained. The analytic model of the FIW discharge predicts key ionization wave parameters, such as wave speed, peak electric field in the front, potential difference across the wave, and electron density as functions of the waveform on the high voltage electrode, in good agreement with the numerical calculations and the experimental results.
Label-free microfluidic characterization of temperature-dependent biomolecular interactions
Authors: Nguyen ThaiHuu , Pei Renjun , Landry Donald W. , Stojanovic Milan N. , Lin Qiao
Published: August 2011

We present a microfluidic approach to characterizing temperature-dependent biomolecular interactions. Solvated L-arginine vasopressin (AVP) and its immobilized RNA aptamer (spiegelmer) were allowed to achieve equilibrium binding in a microchip at a series of selected temperatures. Unbound AVP were collected and analyzed with matrix-assisted laser desorption/ionization mass spectrometry (MALDI-MS), yielding melting curves that reveal highly temperature-dependent zones in which affinity binding (36–45 °C) or dissociation (25–33 °C and 50–65 °C) occurs. Additionally, temperature-dependent binding isotherms were constructed; from these, thermodynamic quantities involved in binding were extracted. The results illustrated a strong change in heat capacity of interaction for this system, suggesting a considerable thermodynamic influence controlling vasopressin-spiegelmer interaction.
Simulation of fluid flow during protein crystal growth in magnetic fields
Authors: Okada H. , Hirota N. , Matsumoto S. , Wada H.
Published: August 2011

We are developing a superconducting magnet system to grow high-quality protein crystals. The gravity-controlled environment, based on magnetic forces, can suppress thermal convection and may give rise to a variety of additional effects on the protein crystal growth. To design suitable magnetic force conditions for protein crystal growth in protein solutions, we are studying a gravity-controlled environment by magnetic forces in the crystal growth process by computer simulations. In this study, we derived a modified Navier-Stokes equation with gravity and static magnetic force and numerically solved the equation. The obtained results show that the temperature dependence of the magnetization modifies the levitation condition and the magnetic force gives rise to an unexpected change of fluid motion.
Space-charge-limited currents and trap characterization in coaxial AlGaN/GaN nanowires
Authors: Simpkins B. S. , Mastro M. A. , Eddy C. R. , Hite J. K. , Pehrsson P. E.
Published: August 2011

This manuscript presents the first observation of the space-charge-limited current (SCLC) conduction mechanism in individual heterostructure nanowires (NWs). This effect is exploited to extract size-dependent carrier densities and to demonstrate surface-dominated behavior for these technologically relevant nanostructures. Mobile carrier densities were shown to increase from 2.5 × 1016 to 5.6 × 1017 cm−3, as NW width decreased from 200 to 50 nm. This size-dependent behavior is a consequence of the increasing influence of near-surface confined carriers as widths decrease. Traps impact the SCLC response and were characterized as an exponential band edge tail with an average characteristic energy of 75 meV. In addition to the specific materials properties extracted, these results further demonstrate the tendency for low-dimensional materials (1D NWs) to exhibit SCLC at much lower injection fluxes compared to their higher dimensional (2D heterostructure field-effect transistors) counterparts.
Transport scattering time and single-particle relaxation time in ZnO/MgZnO heterostructures: Many-body effects
Authors: Gold A.
Published: August 2011

Recent experimental results regarding the transport properties of ZnO/MgZnO heterostructures with very high mobility (μ≤1.8×105cm2/Vs) are analyzed. In the electron density range of the experiment, the two-dimensional electron gas in ZnO/MgZnO heterostructures is strongly correlated with a large Wigner-Seitz parameter 4 < rs < 12. We demonstrate that many-body effects (exchange and correlation), described by a local-field correction, are very large in this density range. They reduce the screening properties of the two-dimensional electron gas and strongly reduce the transport scattering time and the single-particle relaxation time at low electron densities. For such samples, we also discuss the peak mobility, the metal-insulator transition, and the magnetoresistance in a parallel magnetic field.
Charge dynamics in KH2PO4 systematically modified by proton irradiation
Authors: Jung Kweon Jin , Won Lee Kyu , Lee Kwang-Sei , Oh In-Hwan , Eui Lee Cheol
Published: August 2011

Our systematic study employing high-resolution nuclear magnetic resonance measurements shows that the hydrogen bonds and proton transport in the KH2PO4 (KDP) system may be tuned sensitively by proton irradiation. In particular, the hydrogen-bond length in KDP increased by a properly chosen dose of proton irradiation is shown to give rise to a minimum in the activation energy of proton hopping in the hydrogen-bond direction.
Quadratic magneto-optical Kerr effect in Co2MnSi
Authors: Wolf Georg , Hamrle Jaroslav , Trudel Simon , Kubota Takahide , Ando Yasuo , Hillebrands Burkard
Published: August 2011

Quadratic magneto-optical Kerr effects (QMOKE) are investigated in epitaxial Co2MnSi thin films as a function of the post-deposition annealing temperature. We determine the amplitude of the QMOKE signal for different annealing temperatures, which provide various degrees of L21 crystal ordering, as manifested by X-ray diffraction. We observe that QMOKE is significantly present only when the L21 ordering phase is also present, and that the QMOKE signal increases with the higher degree of L21 ordering. Additionally, we notice that the linear magneto-optical Kerr effect (LMOKE) decreases with higher annealing temperature. A comparison of the linear and quadratic MOKE contributions shows the amplitudes are of similar magnitude. From these results, we conclude that the presence of QMOKE is linked to the higher degree of L21 ordering in Co2MnSi.
Interpretation of trap-limited mobility in space-charge limited current in organic layers with exponential density of traps
Authors: Montero José M. , Bisquert Juan
Published: August 2011

Charge carrier transport in disordered organic semiconductors, performed in electronic devices such as optoelectronic and photovoltaic ones, is usually affected by an exponential distribution of localized states in the band-gap (traps) under space-charge limited current. In this paper, we provide a full analysis for the trap-controlled transport of the single-carrier device in the frequency domain. Trap-limited mobility is interpreted in terms of the classical multiple-trapping picture with one transport state and the trapping-detrapping dynamics of the exponential density of traps. This allows us to provide a suitable explanation of the usual experimental features of the mobility dependence on voltage as along with the capacitance spectra.
Vibration waveform effects on dynamic stabilization of ablative Rayleigh-Taylor instability
Authors: Piriz A. R. , Lucchio L. Di , Rodriguez Prieto G. , Tahir N. A.
Published: August 2011

An analysis of dynamic stabilization of Rayleigh-Taylor instability in an ablation front is performed by considering a general square wave for modulating the vertical acceleration of the front. Such a kind of modulation allows for clarifying the role of thermal conduction in the mechanism of dynamic stabilization. In addition, the study of the effect of different modulations by varying the duration and amplitude of the square wave in each half-period provides insight on the optimum performance of dynamic stabilization.
Quantum collapse in ground-state Fermi-Dirac-Landau plasmas
Authors: Akbari-Moghanjoughi M.
Published: August 2011

In this paper, it is revealed that in a relativistically degenerate dense highly magnetized electron-ion plasma, the effective quantum-potential due to the quantum-force acting on fermions may vanish causing a quantum transverse collapse in the ground-state Fermi-Dirac-Landau (GSFDL) plasma. The condition for the plasma transverse collapse is found to be restricted to the minimum relativistic degeneracy parameter and minimum impressed magnetic field strength values satisfied for some superdense astrophysical objects such as white dwarfs and neutron stars. In such objects, the magnetization pressure is shown to cancel the lateral electron degeneracy pressure counteracting the existing gravitational pressure. Furthermore, using the Sagdeev pseudopotential method in the framework of quantum magnetohydrodynamics model, including magnetization, it is confirmed that the quantum pressure due to spin-orbit polarization and the electron relativistic degeneracy has crucial effects on the existence criteria and the propagation of localized magnetosonic density excitations in GSFDL plasmas. Current findings can have important implications for the density excitation mechanism and hydrostatic stability of the highly magnetized astrophysical relativistically dense objects such as white-dwarfs, neutron stars, magnetars, and pulsars.
Carbon nanotube thin film transistors on flexible substrates
Authors: Chandra Bhupesh , Park Hongsik , Maarouf Ahmed , Martyna Glenn J. , Tulevski George S.
Published: August 2011

Carbon nanotube thin film transistors (CNT-TFTs) are fabricated on flexible substrates using purified, surfactant-based CNT suspensions, with >95% semiconducting CNT fraction. The TFTs are made up of local bottom-gated structures with aluminum oxide as the gate dielectric. The devices exhibit high ON current densities (0.1 μA/μm) and on-off ratios (∼105) with mobility values ranging from 10-35 cm2/Vs. A detailed numerical model is used to understand the TFT performance and its dependence on device parameters such as TFT channel length, CNT density, and purity.
Topics in cubic special geometry
Authors: Bellucci Stefano , Marrani Alessio , Roychowdhury Raju
Published: August 2011

We reconsider the sub-leading quantum perturbative corrections to \documentclass[12pt]{minimal}\begin{document}$\mathcal {N }=2$\end{document}N=2 cubic special Kähler geometries. Imposing the invariance under axion-shifts, all such corrections (but the imaginary constant one) can be introduced or removed through suitable, lower unitriangular symplectic transformations and dubbed Peccei-Quinn (PQ) transformations. Since PQ transformations do not belong to the d = 4 U-duality group G4, in symmetric cases they generally have a non-trivial action on the unique quartic invariant polynomial \documentclass[12pt]{minimal}\begin{document}$\mathcal {I}_{4}$\end{document}I4 of the charge representation \documentclass[12pt]{minimal}\begin{document}$\mathbf {R}$\end{document}R of G4. This leads to interesting phenomena in relation to theory of extremal black hole attractors; namely, the possibility to make transitions between different charge orbits of \documentclass[12pt]{minimal}\begin{document}$\mathbf {R}$\end{document}R, with corresponding change of the supersymmetry properties of the supported attractor solutions. Furthermore, a suitable action of PQ transformations can also set \documentclass[12pt]{minimal}\begin{document}$\mathcal {I}_{4}$\end{document}I4 to zero, or vice versa it can generate a non-vanishing \documentclass[12pt]{minimal}\begin{document}$\mathcal {I}_{4}$\end{document}I4: this corresponds to transitions between “large” and “small” charge orbits, which we classify in some detail within the “special coordinates” symplectic frame. Finally, after a brief account of the action of PQ transformations on the recently established correspondence between Cayley's hyperdeterminant and elliptic curves, we derive an equivalent, alternative expression of \documentclass[12pt]{minimal}\begin{document}$\mathcal {I}_{4}$\end{document}I4, with relevant application to black hole entropy.
A family of one-dimensional Vlasov-Maxwell equilibria for the force-free Harris sheet
Authors: Wilson F. , Neukirch T.
Published: August 2011

A family of self-consistent collisionless distribution functions for the force-free Harris sheet is presented. This family includes the distribution function recently found by Harrison and Neukirch [Phys. Rev. Lett. 102, 135003 (2009)] as well as distribution functions with a different dependence on the particle energy, but with the same dependence on the canonical momenta. It is shown generally that the other distribution functions in the family give rise to the same pressure function and, thus, to the same current density and magnetic field as the known distribution function, provided certain conditions on the parameters are satisfied. A number of examples of distribution functions from the new family are given, which illustrate the use of the general method.
Effects of rhenium alloying on adhesion of Mo/HfC and Mo/ZrC interfaces: A first-principles study
Authors: Si Abdelkader H. , Faraoun H. I. , Esling C.
Published: August 2011

Adhesion and electronic structure of Mo/HfC and Mo/ZrC interfaces with and without Re impurity are investigated using first-principles density functional calculations. For Re free interface, results show that Mo atoms bind preferentially on top of C atoms, forming covalent bonds. The presence of Re alloying at the interface improves the adhesion, but does not affect the nature of interfacial Mo-C bonds.
Investigation of the switching wave propagation in linear chains of magnetic elements
Authors: Kaganovskiy L. , Litvinov D. , Khizroev S. , Wilcox S.
Published: August 2011

A micromagnetic study employing OOMMF1 simulator of magnetic switching wave propagation along magnetic data channels is presented. The optimization of the wave propagation as a function of geometry and physical parameters is investigated, which resulted in an order of magnitude increase in the depth of magnetic signal propagation. Unlike unoptimized rapidly decaying waves, the resulting wave stays practically the same throughout the channel, improving wave detection characteristics. When the in-plan dimensions of the channel are scaled proportionally, the optimized propagation length remains relatively constant. This indicates a possibility of the scalability in the data channel, which has significant technological applications.
Angle dependence of the interaction distance in the shear force technique
Authors: Merlo J. M. , Aguilar J. F. , Martí-Panameño E. , Cortés R. , Coello V.
Published: August 2011

We study the interaction distance in the lateral force detection, using a standard quartz tuning fork as a force transducer. That is the distance at which the interaction sample-probe starts to be detected. We study in particular the dependence on the approaching angle. For angles smaller than 0.366 radians, we found an exponential behavior of the interaction distance as a function of the approaching angle. We show an equation that adjusts well with the experimental data, and discuss the possible phenomena.
Cranz-Schardin camera with a large working distance for the observation of small scale high-speed flows
Authors: Skupsch C. , Chaves H. , Brücker C.
Published: August 2011

The Cranz-Schardin camera utilizes a Q-switched Nd:YAG laser and four single CCD cameras. Light pulse energy in the range of 25 mJ and pulse duration of about 5 ns is provided by the laser. The laser light is converted to incoherent light by Rhodamine-B fluorescence dye in a cuvette. The laser beam coherence is intentionally broken in order to avoid speckle. Four light fibers collect the fluorescence light and are used for illumination. Different light fiber lengths enable a delay of illumination between consecutive images. The chosen interframe time is 25 ns, corresponding to 40 × 106 frames per second. Exemplarily, the camera is applied to observe the bow shock in front of a water jet, propagating in air at supersonic speed. The initial phase of the formation of a jet structure is recorded.
An O(N3) implementation of Hedin's GW approximation for molecules
Authors: Foerster D. , Koval P. , Sánchez-Portal D.
Published: August 2011

We describe an implementation of Hedin's GW approximation for molecules and clusters, the complexity of which scales as O(N3) with the number of atoms. Our method is guided by two strategies: (i) to respect the locality of the underlying electronic interactions and (ii) to avoid the singularities of Green's functions by manipulating, instead, their spectral functions using fast Fourier transform methods. To take into account the locality of the electronic interactions, we use a local basis of atomic orbitals and, also, a local basis in the space of their products. We further compress the screened Coulomb interaction into a space of lower dimensions for speed and to reduce memory requirements. The improved scaling of our method with respect to most of the published methodologies should facilitate GW calculations for large systems. Our implementation is intended as a step forward towards the goal of predicting, prior to their synthesis, the ionization energies and electron affinities of the large molecules that serve as constituents of organic semiconductors.
Exciton in an anisotropic parabolic quantum-well wire in the presence of a magnetic field
Authors: Zhai Li-Xue , Wang Yan , Liu Jian-Jun
Published: August 2011

The properties of an exciton in an anisotropic parabolic quantum-well wire in a magnetic field are investigated theoretically. It is found that a decrease in the confinement length increases the exciton binding energy and decreases the longitudinal extension of the exciton wave function. The results of the exciton diamagnetic shifts are in agreement with previously reported magneto-photoluminescence experimental data. Details of the effects of the magnetic field on the binding energy and the wave function of the exciton have been investigated. The conclusion is drawn that the magnetic field has a more pronounced effect in wider quantum-well wires.
Non-hard sphere thermodynamic perturbation theory
Authors: Zhou Shiqi
Published: August 2011

A non-hard sphere (HS) perturbation scheme, recently advanced by the present author, is elaborated for several technical matters, which are key mathematical details for implementation of the non-HS perturbation scheme in a coupling parameter expansion (CPE) thermodynamic perturbation framework. NVT-Monte Carlo simulation is carried out for a generalized Lennard-Jones (LJ) 2n-n potential to obtain routine thermodynamic quantities such as excess internal energy, pressure, excess chemical potential, excess Helmholtz free energy, and excess constant volume heat capacity. Then, these new simulation data, and available simulation data in literatures about a hard core attractive Yukawa fluid and a Sutherland fluid, are used to test the non-HS CPE 3rd-order thermodynamic perturbation theory (TPT) and give a comparison between the non-HS CPE 3rd-order TPT and other theoretical approaches. It is indicated that the non-HS CPE 3rd-order TPT is superior to other traditional TPT such as van der Waals/HS (vdW/HS), perturbation theory 2 (PT2)/HS, and vdW/Yukawa (vdW/Y) theory or analytical equation of state such as mean spherical approximation (MSA)-equation of state and is at least comparable to several currently the most accurate Ornstein-Zernike integral equation theories. It is discovered that three technical issues, i.e., opening up new bridge function approximation for the reference potential, choosing proper reference potential, and/or using proper thermodynamic route for calculation of fex − ref, chiefly decide the quality of the non-HS CPE TPT. Considering that the non-HS perturbation scheme applies for a wide variety of model fluids, and its implementation in the CPE thermodynamic perturbation framework is amenable to high-order truncation, the non-HS CPE 3rd-order or higher order TPT will be more promising once the above-mentioned three technological advances are established.
Multiferroic coupling in nanoscale BiFeO3
Authors: Goswami Sudipta , Bhattacharya Dipten , Choudhury P. , Ouladdiaf B. , Chatterji T.
Published: August 2011

Using the results of x-ray and neutron diffraction experiments, we show that the ferroelectric polarization, in ∼22 nm particles of BiFeO3, exhibits a jump by ∼30% around the magnetic transition point TN (∼635 K) and a suppression by ∼7% under 5T magnetic field at room temperature (≪TN). These results confirm the presence of strong multiferroic coupling even in nanoscale BiFeO3 and thus could prove to be quite useful for applications based on nanosized devices of BiFeO3.
Influence of de-tuning and non-radiative recombination on the temperature dependence of 1.3 μm GaAsSb/GaAs vertical cavity surface emitting lasers
Authors: Hild Konstanze , Marko Igor P. , Johnson S. R. , Yu S.-Q. , Zhang Y.-H. , Sweeney Stephen J.
Published: August 2011

In this letter, we measure the pure spontaneous emission and lasing emission from a working vertical cavity surface emitting laser (VCSEL) for a wide range of temperatures. From this spontaneous emission, we gain insight into the temperature dependence of the radiative component of the threshold current (and hence gain). Together with the temperature dependence of the threshold current, the cavity mode to gain peak alignment and the temperature dependence of an equivalent active region edge emitting laser, we show how non-radiative recombination coupled with gain-cavity de-tuning influences the thermal properties of these devices.
Experimental validation of the exponential localized states distribution in the variable range hopping mechanism in disordered silicon films
Authors: Pichon L. , Rogel R.
Published: August 2011

Carriers transport in low temperature (≤600 °C) polycrystalline silicon thin film transistor channel region is studied for devices biased from weak to strong inversion. Analysis is supported by the theory of the 3D variable range hopping model due to hopping between localized electronic states near the Fermi level. The corresponding density of states is determined following an exponential (tail states) distribution associated with the statistical shift of the Fermi level.
Nanoparticle single-electron transistor with metal-bridged top-gate and nanogap electrodes
Authors: Azuma Yasuo , Suzuki Seiichi , Maeda Kosuke , Okabayashi Norio , Tanaka Daisuke , Sakamoto Masanori , Teranishi Toshiharu , Buitelaar Mark R. , Smith Charles G. , Majima Yutaka
Published: August 2011

Au nanoparticle single-electron transistors with metal-bridged top-gates and nanogap electrodes were fabricated using two consecutive electron beam lithography and electroless Au plating steps. The metal-bridged top-gate electrodes were suspended above electroless Au plated nanogap electrodes. Au nanoparticles (5.2 nm in diameter) were chemisorbed between the nanogap electrodes after top-gate fabrication. Clear Coulomb diamonds were observed at 9 K. The gate capacitance Cg of the top-gate electrodes was 99 zF, which is 10 times larger than that of a similar device with only side-gate electrodes.
Field-effect mobility extraction in nanowire field-effect transistors by combination of transfer characteristics and random telegraph noise measurements
Authors: Nazarov A. N. , Ferain I. , Dehdashti Akhavan N. , Razavi P. , Yu R. , Colinge J. P.
Published: August 2011

A technique based on the combined measurements of random telegraph-signal noise amplitude and drain current vs. gate voltage characteristics is proposed to extract the channel mobility in inversion-mode and accumulation-mode nanowire transistors. This method does not require the preliminary knowledge of the gate oxide capacitance or that of the channel width. The method accounts for the presence of parasitic source and drain resistance effect. It has been used to extract the zero-field mobility and the field mobility reduction factor in inversion-mode and junctionless transistors operating in accumulation mode.
Kramers problem for nonequilibrium current-induced chemical reactions
Authors: Dzhioev Alan A. , Kosov D. S.
Published: August 2011

We discuss the use of tunneling electron current to control and catalyze chemical reactions. Assuming the separation of time scales for electronic and nuclear dynamics we employ Langevin equation for a reaction coordinate. The Langevin equation contains nonconservative current-induced forces and gives nonequilibrium, effective potential energy surface for current-carrying molecular systems. The current-induced forces are computed via Keldysh nonequilibrium Green's functions. Once a nonequilibrium, current-depended potential energy surface is defined, the chemical reaction is modeled as an escape of a Brownian particle from the potential well. We demonstrate that the barrier between the reactant and the product states can be controlled by the bias voltage. When the molecule is asymmetrically coupled to the electrodes, the reaction can be catalyzed or stopped depending on the polarity of the tunneling current.
Single-electron turnstile pumping with high frequencies
Authors: Lin Chuan-Yu , Zhang Wei-Min
Published: August 2011

In this letter, we present a theoretical analysis to single-electron pumping operation in a large range of driving frequencies through the time-dependent tunneling barriers controlled by external gate voltages. We show that the single-electron turnstile works at the frequency lower than the characteristic frequency which is determined by the mean average electron tunneling rate. When the driving frequency is greater than the characteristic frequency of electron tunnelings, fractional electron pumping occurs as an effect of quantum coherence tunneling.
Suppression of the spin pumping in Pd/Ni81Fe19 bilayers with nano-oxide layer
Authors: Kim Duck-Ho , Kim Hong-Hyoun , You Chun-Yeol
Published: August 2011

We demonstrate that the spin pumping effect can be effectively suppressed with a nano-oxide layer. Spin pumping effect manifests itself by an enhancement of the Gilbert damping parameter in normal metal/ferromagnetic hetero-structures, while many spintronics devices prefer smaller damping parameter. Since the spin pumping effect is directly related with the spin dependent interface conductance, we can modify the spin pumping by altering the interface conductance with the nano-oxide layer. We prepared series of Pd/Ni81Fe19 bilayers with different pausing time between Pd and Ni81Fe19 depositions in order to control the interface conductance. The Gilbert damping parameters are determined from the line-width measurements in the ferromagnetic resonance spectra for each pausing time sample. They are 0.0490, 0.0296, 0.0278, and 0.0251 for 0, 6, 30, and 60 s pausing time, respectively. We find that the damping parameter of Pd/Ni81Fe19 is almost recovered to one of the Cu/Ni81Fe19 bilayer with 60 s pausing time, while the static magnetic properties are not noticeably changed.
First principles study of the electric field effect on magnetization and magnetic anisotropy of FeCo/MgO(001) thin film
Authors: He K. H. , Chen J. S. , Feng Y. P.
Published: August 2011

The magnetization and magnetic anisotropy of FeCo/MgO(001) thin film under electric field were investigated by the first-principles calculations. Three different interface configurations were considered: Co/Fe/MgO, Fe/Co/MgO, and FeCo/FeCo/MgO. It was found that the perpendicular anisotropy was preferred for all the configurations and enhanced with increasing electric field, which was consistent with experimental results. Furthermore, our calculations indicated that the FeCo/FeCo/MgO was the most stable configuration and had the largest perpendicular magnetic anisotropy energy. The results also showed that the FeCo/FeCo/MgO and Fe/Co/MgO configurations had larger magnetoelectric coefficients than those of the Co/Fe/MgO configuration and previous report about the Fe/MgO interface.
Bipolar conductivity in amorphous HfO2
Authors: Islamov D. R. , Gritsenko V. A. , Cheng C. H. , Chin A.
Published: August 2011

This study calculates the contribution of electrons and holes to HfO2 conductivity in Si/HfO2/Ni structures using experiments on injection of minority carriers from n- and p-type silicon. Results show that electrons and holes contribute to the conductivity of HfO2, allowing HfO2 to exhibit two-band conductivity.
Mapping of conservative and dissipative interactions in bimodal atomic force microscopy using open-loop and phase-locked-loop control of the higher eigenmode
Authors: Chawla Gaurav , Solares Santiago D.
Published: August 2011

We compare the ability of higher cantilever eigenmodes to map conservative and dissipative tip-sample interactions in bimodal atomic force microscopy under three different control schemes, namely, open-loop (OL), constant-excitation phase-locked-loop (CE-PLL), and constant-amplitude phase-locked-loop (CA-PLL). We perform a direct comparison of these schemes by applying analytical expressions of the virial and dissipated power to imaging and spectroscopy experiments conducted on a two-component polymer sample in air. We find that OL and CE-PLL provide similar information, while CA-PLL explores a broader range of interactions, especially for softer samples, due to its constant sensitivity to tip-sample forces.
Communication: A new hybrid exchange correlation functional for band-gap calculations using a short-range Gaussian attenuation (Gaussian-Perdue–Burke–Ernzerhof)
Authors: Song Jong-Won , Yamashita Koichi , Hirao Kimihiko
Published: August 2011

We have developed a new hybrid functional [Gaussian-Perdue–Burke–Ernzerhof (Gau-PBE)] that is suitable for the calculation of solid state bandgaps using a periodic boundary condition. The characteristic of this functional is the use of a Gaussian attenuation scheme (Gau) to include a short-range Hartree–Fock (HF) exchange. This new functional can perform barrier height calculations with an accuracy comparable to the middle-range hybrid functional and bandgap calculations with an accuracy comparable to the Heyd–Scuseria–Ernzerhof (HSE) functional. However, the point is that the performance can be achieved using a Gaussian HF exchange, while the HISS functional calculates twice HF-exchange integrations using an error function to obtain both performances. In addition, Gau-PBE functional can decrease the time cost of bandgap calculations by an average of 40% compared to the HSE functional.
Reflection and Transmission of Acoustic Waves at Semiconductor - Liquid Interface
Authors: Sharma J. N. , Sharma A.
Published: August 2011

The study of reflection and transmission characteristics of acoustic waves at the interface of a semiconductor halfspace underlying an inviscid liquid has been carried out. The reflection and transmission coefficients of reflected and transmitted waves have been obtained for quasi-longitudinal (qP) wave incident at the interface from fluid to semiconductor. The numerical computations of reflection and transmission coefficients have been carried out with the help of Gauss elimination method by using MATLAB programming for silicon (Si), germanium (Ge) and silicon nitride (Si3N4) semiconductors. In order to interpret and compare, the computer simulated results are plotted graphically. The study may be useful in semiconductors, seismology and surface acoustic wave (SAW) devices in addition to engines of the space shuttles.
Effective masses and electronic structure of diamond including electron correlation effects in first principles calculations using the GW-approximation
Authors: Löfås Henrik , Grigoriev Anton , Isberg Jan , Ahuja Rajeev
Published: August 2011

We present calculated interband transitions and effective masses for diamond from first principles including electron correlation effects via the GW-approximation. Our findings are in agreement with experiments, already the first iteration of the GW-scheme gives a direct gap at the gamma-point of 7.38 eV and a indirect gap of 5.75 eV close to experimental values. For deeper bands a quasiparticle self-consistent method is necessary to accurately reproduce the valence band width to 23.1 eV. We also obtain effective hole masses along different symmetry axes and electron conduction masses, ml = 1.1m0 and mt = 0.22m0
The mitochondrial DNA haplotypes of snails of the estuarine hydrobiid genus Tatea cross species and biogeographic boundaries
Authors: Colgan D. J. , da Costa P.
Published: August 2011

Investigations of estuarine taxa can provide a perspective on phylogeography that complements studies of marine littoral organisms. For example, reductions in gene flow between populations and increased genetic structuring would be expected in estuarine species. The substantial amount of information about marine species and the habitat diversity along long latitudinal spans makes south-eastern Australia an excellent potential location for comparing marine and estuarine taxa. To investigate this potential, we studied the phylogeography of the two species in the estuarine gastropod genus Tatea. These have extensive and broadly overlapping distributions that encompass known marine phylogeographic boundaries. Against expectation, both Tatea species showed a remarkable lack of geographic and inter-specific variability in mitochondrial 12S rRNA (107 specimens) and cytochrome c oxidase subunit I (39) DNA sequences. No major phylogeographic discontinuities were revealed in either species and there was minimal haplotype divergence between them for either 12S rRNA or COI. The patterns of mitochondrial DNA variation discovered in Tatea may be due to a recent selective sweep or range expansion from a population in which there was little variability. Both possibilities are complicated by having to explain the similarity of the patterns in the two species.
Polygamy and low effective population size in a captive Murray cod (Maccullochella peelii peelii) population: genetic implications for wild restocking programs
Authors: Rourke Meaghan L. , McPartlan Helen C. , Ingram Brett A. , Taylor Andrea C.
Published: August 2011

Stocking of freshwater fish species with hatchery-bred fish is a common response to depleted wild stocks, but may have numerous genetic implications. Murray cod, Maccullochella peelii peelii (Mitchell), have been produced in captivity for wild stocking programs for more than 30 years. The potential genetic impacts of this stocking program on wild populations was investigated by using eight microsatellite markers to determine the parentage of 1380 offspring from 46 separate spawnings collected over three consecutive breeding seasons, and by estimating the effective population size of the broodfish generation through demographic and genetic methods. Results revealed unexpected incidences of polygamous spawnings (both polygyny and polyandry), multiple spawnings by both sexes within a season and repeated matings between pairs of fish across multiple seasons. Furthermore, approximately half of the broodfish failed to spawn at all over the 3-year study period. This likely contributed to the estimated effective population size of around half of the census size, moderate but significant reductions in allelic richness in all three cohorts investigated and a small but significant reduction in heterozygosity in two cohorts. These results allowed us to make recommendations regarding captive husbandry that will maximise genetic diversity of fish intended for stocking.