bluuebunny/crossref_metadata_2025 huggingface dataset:
Source identity and kernel functions for Inozemtsev-type systems
Authors: Langmann Edwin , Takemura Kouichi
Published: August 2012

The Inozemtsev Hamiltonian is an elliptic generalization of the differential operator defining the BCN trigonometric quantum Calogero-Sutherland model, and its eigenvalue equation is a natural many-variable generalization of the Heun differential equation. We present kernel functions for Inozemtsev Hamiltonians and Chalykh-Feigin-Veselov-Sergeev-type deformations thereof. Our main result is a solution of a heat-type equation for a generalized Inozemtsev Hamiltonian which is the source of all these kernel functions. Applications are given, including a derivation of simple exact eigenfunctions and eigenvalues of the Inozemtsev Hamiltonian.
Flexoelectric effect in finite samples
Authors: Tagantsev Alexander K. , Yurkov Alexander S.
Published: August 2012

Static flexoelectric effect in a finite sample of a solid is addressed in terms of phenomenological theory for the case of a thin plate subjected to bending. It has been shown that despite an explicit asymmetry inherent to the bulk constitutive electromechanical equations which take into account the flexoelectric coupling, there exists a situation where electromechanical response for a finite sample is “symmetric.” “Symmetric” means that if a sensor and an actuator are made of a flexoelectric element, performance of such devices can be characterized by the same effective piezoelectric coefficient. This behavior is consistent with the thermodynamic arguments offered earlier, being in conflict with the current point of view on the matter in literature. This result was obtained using standard mechanical boundary conditions valid for the case where the polarization vanishes at the surface. It was shown that, for the case where the polarization at the surface is not zero, the aforementioned symmetry of electromechanical response may be violated if standard mechanical boundary conditions are used, leading to a conflict with the thermodynamic arguments. It is suggested that this conflict may be resolved when using modified mechanical boundary conditions. It is also shown that the contribution of surface piezoelectricity to the flexoelectric response of a finite sample is expected to be comparable to that of the static bulk contribution (including materials with high values of the dielectric constant) and to scale as the bulk value of the dielectric constant (similar to the bulk contribution). This finding implies that if the experimentally measured flexoelectric coefficient scales as the dielectric constant of the material, this does not imply that the measured flexoelectric response is controlled by the static bulk contribution to the flexoelectric effect.
Variational approach for nonpolar solvation analysis
Authors: Chen Zhan , Zhao Shan , Chun Jaehun , Thomas Dennis G. , Baker Nathan A. , Bates Peter W. , Wei G. W.
Published: August 2012

Solvation analysis is one of the most important tasks in chemical and biological modeling. Implicit solvent models are some of the most popular approaches. However, commonly used implicit solvent models rely on unphysical definitions of solvent-solute boundaries. Based on differential geometry, the present work defines the solvent-solute boundary via the variation of the nonpolar solvation free energy. The solvation free energy functional of the system is constructed based on a continuum description of the solvent and the discrete description of the solute, which are dynamically coupled by the solvent-solute boundaries via van der Waals interactions. The first variation of the energy functional gives rise to the governing Laplace-Beltrami equation. The present model predictions of the nonpolar solvation energies are in an excellent agreement with experimental data, which supports the validity of the proposed nonpolar solvation model.
Dynamics of thermoluminescence spectra of impurity–helium condensates containing stabilized nitrogen and oxygen atoms
Authors: Khmelenko V. V. , Lee D. M. , Krushinskaya I. N. , Boltnev R. E. , Bykhalo I. B. , Pelmenev A. A.
Published: August 2012

The results of investigations of thermoluminescence dynamics during destruction of neon–helium and krypton–helium condensates containing stabilized nitrogen and oxygen atoms are presented. Spectra of the thermoluminescence of a krypton–helium condensate contained bands of N and O atoms and NO molecules. The intensities of the bands in these spectra were found to increase simultaneously during destruction processes in the temperature range 1.5–15 K. The observation of NO molecules provides clear evidence for chemical reactions in the nanoclusters comprising the sample at low temperatures. Destruction of neon–helium samples occurred in two stages. During the first stage the α-group of N atoms surrounded by Ne and N2 molecules dominated the spectra. During the second stage, the spectra contained intense bands of N and O atoms stabilized in a molecular nitrogen matrix. The unusual characteristics of the thermoluminescence spectra were observed, and their changes were explained in terms of the shell structure of impurity nanoclusters, which comprised the impurity–helium condensates.
Low-temperature phosphorescence of dicyanoacetylene in rare gas solids
Authors: Turowski Michał , Crépin Claudine , Couturier-Tamburelli Isabelle , Piétri Nathalie , Kołos Robert
Published: August 2012

A strong visible ã3Σu+ – X̃1Σg+ luminescence was observed upon UV excitation of cryogenic rare gas (argon, krypton, and xenon) matrices doped with dicyanoacetylene (NC4N). Spectra and lifetimes of this phosphorescence have been measured. A detailed analysis of resolved vibronic bands is presented.
Component dynamics in polyvinylpyrrolidone concentrated aqueous solutions
Authors: Busselez Rémi , Arbe Arantxa , Cerveny Silvina , Capponi Sara , Colmenero Juan , Frick Bernhard
Published: August 2012

2H-nuclear magnetic resonance (NMR) and neutron scattering (NS) on isotopically labelled samples have been combined to investigate the structure and dynamics of polyvinylpyrrolidone (PVP) aqueous solutions (4 water molecules/monomeric unit). Neutron diffraction evidences the nanosegregation of polymer main-chains and water molecules leading to the presence of water clusters. NMR reveals the same characteristic times and spectral shape as those of the slower process observed by broadband dielectric spectroscopy in this system [S. Cerveny et al., J. Chem. Phys. 128, 044901 (2008)]10.1063/1.2822332. The temperature dependence of such relaxation time crosses over from a cooperative-like behavior at high temperatures to an Arrhenius behavior at lower temperatures. Below the crossover, NMR features the spectral shape as due to a symmetric distribution of relaxation times and the underlying motions as isotropic. NS results on the structural relaxation of both components–isolated via H/D labeling–show (i) anomalously stretched and non-Gaussian functional forms of the intermediate scattering functions and (ii) a strong dynamic asymmetry between the components that increases with decreasing temperature. Strong heterogeneities associated to the nanosegregated structure and the dynamic asymmetry are invoked to explain the observed anomalies. On the other hand, at short times the atomic displacements are strongly coupled for PVP and water, presumably due to H-bond formation and densification of the sample upon hydration.
Effects of strain, d-band filling, and oxidation state on the surface electronic structure and reactivity of 3d perovskite surfaces
Authors: Akhade Sneha A. , Kitchin John R.
Published: August 2012

Trends in the dissociative oxygen adsorption energy and oxygen vacancy formation energy on cubic LaBO3 and SrBO3 perovskite (001) surfaces (where B = Sc, Ti, V, Cr, Mn, Fe, Co, Ni, and Cu) and their dependence on strain, d-band filling, and oxidation state were examined using density functional theory in the generalized gradient approximation. The effects of strain were found to be small compared to the effects of d-band filling and oxidations state. Electronic structure descriptors such as the d-band center of the B-atom were identified for trends in the dissociative oxygen adsorption energy and for the oxygen vacancy formation energy. A chemical correlation between these two reaction energies was also identified showing the trends in these reaction energies are not independent of each other.
Magneto-optical system for high speed real time imaging
Authors: Baziljevich M. , Barness D. , Sinvani M. , Perel E. , Shaulov A. , Yeshurun Y.
Published: August 2012

A new magneto-optical system has been developed to expand the range of high speed real time magneto-optical imaging. A special source for the external magnetic field has also been designed, using a pump solenoid to rapidly excite the field coil. Together with careful modifications of the cryostat, to reduce eddy currents, ramping rates reaching 3000 T/s have been achieved. Using a powerful laser as the light source, a custom designed optical assembly, and a high speed digital camera, real time imaging rates up to 30 000 frames per seconds have been demonstrated.
Effects of streamwise rotation on the dynamics of a droplet
Authors: Poon Eric K. W. , Lou Jing , Quan Shaoping , Ooi Andrew S. H.
Published: August 2012

An initially streamwise rotating droplet released into a uniform cross flow is studied numerically. The computations are performed using a finite volume Navier–Stokes solver which employs a moving mesh interface tracking scheme to locate the interface. With a large initial Weber number (Wei = 40) the streamwise rotating droplet flattens along the free stream direction more quickly as rotation rate (\documentclass[12pt]{minimal}\begin{document}$\varOmega ^*$\end{document}Ω*) increases, and leads to a dramatic increase in the dynamic drag coefficient (CD/A*, where A* is the dimensionless frontal area). On the other hand, for Wei = 4 and 0.4 at \documentclass[12pt]{minimal}\begin{document}$\varOmega ^* \ge 0.6$\end{document}Ω*≥0.6, the flattening of the droplet is less pronounced and the droplet even restores to spherical shape, hence, CD/A* decreases sharply. The dynamic drag coefficient even becomes negative for Wei = 4 and 0.4 at \documentclass[12pt]{minimal}\begin{document}$\varOmega ^* = 1$\end{document}Ω*=1. At the largest deformation, the droplet can be classified into three major shapes: biconvex, convex-concave, and biconcave. One dominant feature of the wake downstream of the droplet is the formation and convection of vortex rings. The shape and deformation of the droplet is dependent not only on the size of the vortex ring, but also upon the free stream dynamic pressure and droplet pressure. The detachment of vortex ring in the wake leads to a substantial drag reduction, and this detachment occurs at Re ≈ 28.
Systematic coarse-graining of potential energy landscapes and dynamics in liquids
Authors: Shell M. Scott
Published: August 2012

Recent efforts have shown that the dynamic properties of a wide class of liquids can be mapped onto semi-universal scaling laws and constitutive relations that are motivated by thermodynamic analyses of much simpler models. In particular, it has been found that many systems exhibit dynamics whose behavior in state space closely follows that of soft-sphere particles interacting through an inverse power repulsion. In the present work, we show that a recently developed coarse-graining theory provides a natural way to understand how arbitrary liquids can be mapped onto effective soft-sphere models and hence how one might potentially be able to extract underlying dynamical scaling laws. The theory is based on the relative entropy, an information metric that quantifies how well a soft-sphere approximation to a liquid's multidimensional potential energy landscape performs. We show that optimization of the relative entropy not only enables one to extract effective soft-sphere potentials that suggest an inherent scaling of thermodynamic and dynamic properties in temperature-density space, but that also has rather interesting connections to excess entropy based theories of liquid dynamics. We apply the approach to a binary mixture of Lennard-Jones particles, and show that it gives effective soft-sphere scaling laws that well-describe the behavior of the diffusion constants. Our results suggest that the relative entropy formalism may be useful for “perturbative” type theories of dynamics, offering a general strategy for systematically connecting complex energy landscapes to simpler reference ones with better understood dynamic behavior.
Exact dynamic properties of molecular motors
Authors: Boon N. J. , Hoyle R. B.
Published: August 2012

Molecular motors play important roles within a biological cell, performing functions such as intracellular transport and gene transcription. Recent experimental work suggests that there are many plausible biochemical mechanisms that molecules such as myosin-V could use to achieve motion. To account for the abundance of possible discrete-stochastic frameworks that can arise when modeling molecular motor walks, a generalized and straightforward graphical method for calculating their dynamic properties is presented. It allows the calculation of the velocity, dispersion, and randomness ratio for any proposed system through analysis of its structure. This article extends work of King and Altman [“A schematic method of deriving the rate laws of enzyme-catalyzed reactions,” J. Phys. Chem. 60, 1375–1378 (1956)]10.1021/j150544a010 on networks of enzymatic reactions by calculating additional dynamic properties for spatially hopping systems. Results for n-state systems are presented: single chain, parallel pathway, divided pathway, and divided pathway with a chain. A novel technique for combining multiple system architectures coupled at a reference state is also demonstrated. Four-state examples illustrate the effectiveness and simplicity of these methods.
Density maximum and polarizable models of water
Authors: Kiss Péter T. , Baranyai András
Published: August 2012

To estimate accurately the density of water over a wide range of temperatures with a density maximum at 4 °C is one of the most stringent tests of molecular models. The shape of the curve influences the ability to describe critical properties and to predict the freezing temperature. While it was demonstrated that with a proper parameter fit nonpolarizable models can approximate this behavior accurately, it is much more difficult to do this for polarizable models. We provide a short overview of ρ–T diagrams for existing models, then we give an explanation of this difficulty. We present a version of the BK model [A. Baranyai and P. T. Kiss, J. Chem. Phys. 133, 144109 (2010)10.1063/1.3490660; A. Baranyai and P. T. Kiss, J. Chem. Phys. 135, 234110 (2011)]10.1063/1.3670962 which is capable to predict the density of water over a wide range of temperature. The BK model uses the charge-on-spring method with three Gaussian charges. Since the experimental dipole moment and the geometry is fixed, and the quadrupole moment is approximated by a least mean square procedure, parameters of the repulsion and dispersive attraction forces remained as free tools to match experimental properties. Relying on a simplified but plausible justification, the new version of the model uses repulsion and attraction as functions of the induced dipole moment of the molecule. The repulsive force increases, while the attractive force decreases with the size of the molecular dipole moment. At the same time dipole moment dependent dispersion forces are taking part in the polarization of the molecule. This scheme iterates well and, in addition to a reasonable density-temperature function, creates dipole distributions with accurate estimation of the dielectric constant of the liquid.
Towards a minimal stochastic model for a large class of diffusion-reactions on biological membranes
Authors: Chevalier Michael W. , El-Samad Hana
Published: August 2012

Diffusion of biological molecules on 2D biological membranes can play an important role in the behavior of stochastic biochemical reaction systems. Yet, we still lack a fundamental understanding of circumstances where explicit accounting of the diffusion and spatial coordinates of molecules is necessary. In this work, we illustrate how time-dependent, non-exponential reaction probabilities naturally arise when explicitly accounting for the diffusion of molecules. We use the analytical expression of these probabilities to derive a novel algorithm which, while ignoring the exact position of the molecules, can still accurately capture diffusion effects. We investigate the regions of validity of the algorithm and show that for most parameter regimes, it constitutes an accurate framework for studying these systems. We also document scenarios where large spatial fluctuation effects mandate explicit consideration of all the molecules and their positions. Taken together, our results derive a fundamental understanding of the role of diffusion and spatial fluctuations in these systems. Simultaneously, they provide a general computational methodology for analyzing a broad class of biological networks whose behavior is influenced by diffusion on membranes.
Photoinduced electron transfer processes in dye-semiconductor systems with different spacer groups
Authors: Li Jingrui , Wang Haobin , Persson Petter , Thoss Michael
Published: August 2012

Photoinduced electron transfer processes in perylene-titanium dioxide dye-semiconductor systems are studied. In particular, the influence of saturated and unsaturated aliphatic spacer groups inserted between the chromophore and the semiconductor substrate is investigated. The study is based on a recently developed method that combines first-principles electronic structure calculations to characterize the dye-semiconductor systems and accurate multilayer multiconfiguration time-dependent Hartree simulations to reveal the underlying nonadiabatic dynamics. The results show that, in agreement with previous experimental studies, the spacer groups may affect the electron transfer dynamics significantly. Furthermore, the influence of electronic-vibrational coupling on the electron transfer dynamics and absorption spectra is discussed.
Bubble pinch-off and scaling during liquid drop impact on liquid pool
Authors: Ray Bahni , Biswas Gautam , Sharma Ashutosh
Published: August 2012

Simulations are performed to show entrapment of air bubble accompanied by high speed upward and downward water jets when a water drop impacts a pool of water surface. A new bubble entrapment zone characterised by small bubble pinch-off and long thick jet is found. Depending on the bubble and jet behaviour, the bubble entrapment zone is subdivided into three sub-regimes. The entrapped bubble size and jet height depends on the crater shape and its maximum depth. During the bubble formation, bubble neck develops an almost singular shape as it pinches off. The final pinch-off shape and the power law governing the pinching, rneck ∝ A(t0 − t)αvaries with the Weber number. Weber dependence of the function describing the radius of the bubble during the pinch-off only affects the coefficient A and not the power exponent α.
Oscillatory regularity of charge carrier traps energy spectra in silicon organic polymer poly(di-n-hexylsilane)
Authors: Gumenjuk A. , Ostapenko N. , Ostapenko Yu. , Kerita O. , Suto S. , Watanabe A.
Published: August 2012

Charge carrier traps energy spectra have been investigated in silicon organic polymer poly(di-n-hexylsilane) by fractional thermally stimulated luminescence in the temperature range from 5 to 200 K. The energy spectrum of traps has been found to be discrete in nature—not quasi-continuous, as was regarded earlier. It has been established that trap energies form two characteristic series result from the vibrational quanta at 373 and 259 cm–1, respectively. It is important that these vibrational quanta coincide with the frequencies of the totally symmetric vibrational modes of silicon chain, which are active in Raman spectrum. The regularities mentioned are analyzed using the oscillatory traps model as the basis.
Spectral emission measurements of lithium on the lithium tokamak experiment
Authors: Gray T. K. , Biewer T. M. , Boyle D. P. , Granstedt E. M. , Kaita R. , Maingi R. , Majeski R. P.
Published: August 2012

There has been a long-standing collaboration between ORNL and PPPL on edge and boundary layer physics. As part of this collaboration, ORNL has a large role in the instrumentation and interpretation of edge physics in the lithium tokamak experiment (LTX). In particular, a charge exchange recombination spectroscopy (CHERS) diagnostic is being designed and undergoing staged testing on LTX. Here we present results of passively measured lithium emission at 5166.89 Å in LTX in anticipation of active spectroscopy measurements, which will be enabled by the installation of a neutral beam in 2013. Preliminary measurements are made in transient LTX plasmas with plasma current, Ip < 70 kA, ohmic heating power, Poh ∼ 0.3 MW and discharge lifetimes of 10–15 ms. Measurements are made with a short focal length spectrometer and optics similar to the CHERS diagnostics on NSTX [R. E. Bell, Rev. Sci. Instrum. 68(2), 1273–1280 (1997)10.1063/1.1147885]. These preliminary measurements suggest that even without the neutral beam for active spectroscopy, there is sufficient passive lithium emission to allow for line-of-sight profile measurements of ion temperature, Ti; toroidal velocity and vt. Results show peak Ti = 70 eV and peak vt = 45 km/s were reached 10 ms into the discharge.
Nuclear magnetic resonance apparatus for pulsed high magnetic fields
Authors: Meier Benno , Kohlrautz Jonas , Haase Jürgen , Braun Marco , Wolff-Fabris Frederik , Kampert Erik , Herrmannsdörfer Thomas , Wosnitza Joachim
Published: August 2012

A nuclear magnetic resonance apparatus for experiments in pulsed high magnetic fields is described. The magnetic field pulses created together with various magnet coils determine the requirements such an apparatus has to fulfill to be operated successfully in pulsed fields. Independent of the chosen coil it is desirable to operate the entire experiment at the highest possible bandwidth such that a correspondingly large temporal fraction of the magnetic field pulse can be used to probe a given sample. Our apparatus offers a bandwidth of up to 20 MHz and has been tested successfully at the Hochfeld-Magnetlabor Dresden, even in a very fast dual coil magnet that has produced a peak field of 94.2 T. Using a medium-sized single coil with a significantly slower dependence, it is possible to perform advanced multi-pulse nuclear magnetic resonance experiments. As an example we discuss a Carr-Purcell spin echo sequence at a field of 62 T.
Effect of soot microstructure on its ozonization reactivity
Authors: Han Chong , Liu Yongchun , Ma Jinzhu , He Hong
Published: August 2012

Large uncertainty among the measured uptake coefficients of O3 on soot highlights the importance of the sources and chemical structures of soot samples in this reaction. Soot samples with different microstructures were prepared by combusting n-hexane under controlled conditions. Their reactivities to O3 were further investigated using in situ Raman spectroscopy. The fuel/oxygen ratio in the combustion experiments not only affected the diameter of the primary particles, but also influenced the micro-chemical structure of soot. Average diameters of soot particles decreased with the decreasing fuel/oxygen ratio. Compared to the “fuel-rich” flame soot, the “fuel-lean” flame soot showed lower structural uniformity with higher disordered carbon content at the graphene layer edges (D1 band) and the surface graphene layers (D2 band) and the amorphous carbon content (D3 band). This disordered carbon was identified as the reactive component for the ozonization of both the “fuel-rich” and “fuel-lean” flame soot samples. The kinetics study demonstrated that the disordered carbon at the surface graphene layers was more active than that at the graphene layer edges in one sample, and the reactivity of these two microstructures types to O3 in the “fuel-rich” flame soot was higher than that in the “fuel-lean” flame soot.
A new concept in regulation of dc sources in cascaded multi-level inverters to improve output voltage total harmonic distortion
Authors: Hosseini Aghdam M. G.
Published: August 2012

In cascaded multi-level inverters, it is usually assumed that the dc sources have the same constant voltage and output harmonics minimization is accomplished by applying proper switching angles. Employing different dc voltages with proper ratios can result in further reduction of the harmonics. This paper introduces a new concept in selecting the values of the input dc source voltages in cascaded multi-level inverters in order to improve the output voltage total harmonic distortion (THD). After formulation of the system, i.e., describing the inverter’s output voltage components in terms of the switching angles and unequal dc source voltages, a rule is applied to obtain the step heights of the staircase output waveform (dc source voltages), so that the output waveform becomes as close to the required fundamental sine wave as possible. Substituting the obtained dc source voltages into the harmonics elimination equations results in a set of equations, which are functions of switching angles only. Solving these equations leads to proper switching angles, which, regardless of the fundamental component’s value, provide the specified harmonic conditions. The output voltage is then controlled by dc sources voltage regulation. Simulation results show that employing the proposed concept results in substantial improvement in the harmonic minimization, as well as, extending the operating range of the inverter, compared to the conventional methods with equal dc source voltage multi-level inverters.
Role of phonon dispersion in studying phonon mean free paths in skutterudites
Authors: Zebarjadi Mona , Yang Jian , Lukas Kevin , Kozinsky Boris , Yu Bo , Dresselhaus Mildred S. , Opeil Cyril , Ren Zhifeng , Chen Gang
Published: August 2012

Experimental thermal conductivity of bulk materials are often modeled using Debye approximation together with functional forms of relaxation time with fitting parameters. While such models can fit the temperature dependence of thermal conductivity of bulk materials, the Debye approximation leads to large error in the actual phonon mean free path, and consequently, the predictions of the thermal conductivity of the nanostructured materials using the same relaxation time are not correct even after considering additional size effect on the mean free path. We investigate phonon mean free path distribution inside fully unfilled (Co4Sb12) and fully filled (LaFe4Sb12) bulk skutterudites by fitting their thermal conductivity to analytical models which employ different phonon dispersions. We show that theoretical thermal conductivity predictions of the nanostructured samples are in agreement with the experimental data obtained for samples of different grain sizes only when the full phonon dispersion is considered.
Exchange bias training effect under different energy dissipation pattern
Authors: Su Yuanchang , Hu Jingguo
Published: August 2012

The phenomenon of exchange bias training effect is successfully obtained by introducing an out-of-step of energy dissipation of ferromagnet and antiferromagnet. The numerical results suggest that the energy dissipation pattern of the antiferromagnet plays a crucial role for the understanding of the exchange bias training effects, e.g., when the energy dissipation pattern of the antiferromagnet follows power-law function, the best fit function for the dependence of exchange bias on the cycle number is power-law. The physical mechanism that the amount of the coercive field shift in the descent branch is larger than that of ascent branch for the hysteresis loop measurement and the coercivity of ferromagnet/antiferromagnet bilayers is always larger than that of the corresponding ferromagnet layer has been illuminated, respectively. Moreover, under the different values of damping parameter, the anomalous training effect observed by recent experiment [Z. Shi et al., Appl. Phys. Lett. 93, 222504 (2008)] and the conventional training effect can also be elucidated, respectively.
Effects of surface micromesas on reverse leakage current in InGaN/GaN Schottky barriers
Authors: Lu Wei , Nishimura Tomoaki , (Dennis) Wang Lingquan , Nakamura Tohru , Yu Paul K. L. , Asbeck Peter M.
Published: August 2012

This work shows the correlation between excess reverse leakage currents in InGaN/GaN Schottky barrier diodes and the presence of surface micromesas on these structures. Surface micromesas with diameters of 1–2 μm and density in the range of 105 cm−2 were observed in metal-organic-chemical-vapor-deposition-grown InGaN (∼10 nm)/GaN epi-layers on c-sapphire substrates. Nomarski optical microscopy, scanning electron microscopy, and atomic force microscopy were used to investigate characteristics of the surface micromesas. We found that most of the surface micromesas originated from nanopipes in GaN as they intersected the InGaN/GaN epi-layer surface. Extensive current-voltage and Rutherford backscattering spectrometry measurements on the corresponding Ni-InGaN/GaN Schottky barriers revealed that these surface micromesas with nanopipes at their center were likely the main source of reverse leakage current. They also provide an easy metal diffusion path when devices undergo thermal annealing, even at relatively low temperatures. High-pressure (near atmospheric pressure) buffer layer growth can be used to minimize the surface micromesas and the leakage currents.
Control strategies of doubly fed induction generator-based wind turbine system with new rotor current protection topology
Authors: John Justo Jackson , Ro Kyoung-Soo
Published: August 2012

A protection scheme of a doubly fed induction generator (DFIG) based wind turbine system during faults is crowbar activation. With this protection, the rotor side converter (RSC) is temporarily disconnected, and its vector control over the stator active and reactive power is lost, leading to poor power quality at the point of common coupling (PCC). This paper presents a new protection scheme for transient rotor current to improve the performance of DFIG during grid disturbance. The new scheme, consisting of a crowbar and series circuit, is connected between the rotor windings and RSC to enhance the low voltage ride-through capability of DFIG. The proposed scheme successfully limits the transient rotor current and dc-link voltage, and a disconnection of RSC from the rotor windings is avoided during fault. Additionally, RSC and grid-side converter controllers are modified to improve the voltage at PCC. Simulations on matlab/Simulink verify the effectiveness of the proposed scheme.
Photoactivation of neurons by laser-generated local heating
Authors: Migliori Benjamin , Di Ventra Massimiliano , Kristan William
Published: August 2012

We present a method for achieving temporally and spatially precise photoactivation of neurons without the need for genetic expression of photosensitive proteins. Our method depends upon conduction of thermal energy via absorption by chemically inert carbon particles and does not require the presence of voltage-gated channels to create transmembrane currents. We demonstrate photothermal initiation of action potentials in Hirudo verbana neurons within an intact ganglion and of transmembrane currents in Xenopus oocytes. Thermal energy is delivered by focused 50 ms, 650 nm laser pulses with total pulse energies between 250 and 3500 μJ. We document an optical delivery system for targeting specific neurons that can be expanded for multiple target sites. Our method achieves photoactivation reliably (70 - 90% of attempts) and can issue multiple pulses (6-9) with minimal changes to cellular properties as measured by intracellular recording. Direct photoactivation presents a significant step towards all-optical analysis of neural circuits in animals such as Hirudo verbana where genetic expression of photosensitive compounds is not feasible.
Effecting change using careplans: experience from two fractured neck of femur pathways
Authors: Baker Kylie , Brierley Stephen , Mitchell Geoffrey , Roe John
Published: August 2012

Objective. To use a qualitative track of the effects of two fractured neck of femur careplans (1 & 2) implemented at the Ipswich Emergency Department in 2002 and 2003 in order to comment on the reasons for comparative successes and failures as instruments for change in clinical practice. Careplan 1 was initiated by local clinicians in 2002, rescinded in 2003 to make way for the system wide careplan 2, then informally restituted in 2004 after careplan 2 was withdrawn. Careplan 2 did not articulate specific ED management plans. Method. Biennial retrospective chart audits of two newly introduced evidence-based clinical practices over time was used to track changes from careplan 1. These were the use of regional anaesthesia by medical staff, and the compliance with indwelling urinary catheter insertion by nursing staff. Results. Elements of careplan 1 continued despite lack of promotion. There has been significant increase in nerve block (2.8% to 27%) and indwelling catheter insertion (26% to 75%) from 2000 to 2009. Formal use of careplan 1 has declined to 13–20% in 2009. Careplan 2 was withdrawn for review in 2004. Conclusions. Careplans are one way to effect lasting changes in clinical behaviours which may persist beyond their implementation and promotion phases. For acceptance, corporate plans should incorporate local practices. For longevity, local plans should comply with the corporate vision of continuity of care, but local investment in the plan will facilitate uptake.
A framework to improve evidence-informed decision-making in health service management
Authors: Liang Zhanming , Howard Peter F. , Leggat Sandra G. , Murphy Gregory
Published: August 2012

Objective. The objective of this paper is to present and provide justification for a framework to improve evidence-informed management decision-making among health service managers. Three research questions informed the study: How have different perspectives influenced how evidence has been defined? What are the barriers to the practice of evidence-informed decision-making (EIDM)? What are the factors that may encourage the application of evidence to guide management decision-making processes? Methods. A literature review was conducted to identify studies that examined the practice of EIDM among health service managers. Information relevant to the three research questions was collectively analysed, compared and contrasted based on their relevance to the EIDM process. Conclusion. Several factors have played different but significant roles in affecting the practice of EIDM among health service managers. Although interaction between these factors is complex, the framework developed in this paper may guide the development of strategies to encourage and improve the utilisation of evidence in management decision-making process. What is known about the topic? EIDM has been promoted as a mechanism for improving the quality of management decisions, and hence better service delivery, effectiveness and efficiency. Previous studies have explored and discussed various factors that may affect the practice of EIDM amongst health service managers. However, a greater understanding of how these factors interact is required so that relevant strategies to promote the increased use of EIDM can be developed. What does this paper add? The paper clarifies ‘evidence’ from the view of both managers and members of the research community. It discusses factors that may affect the practice of EIDM among health service managers and develops a framework to for better understanding of how these factors interact and affect practice at various levels. The framework will guide the development of strategies to encourage the utilisation of evidence among health service managers. What are the implications for practitioners? To encourage the practice of evidence-informed decision-making amongst health service managers, multi-level changes in the system, organisation and individual levels are required. To maximise the benefit and relevance of research evidence, managers should be actively involved in setting research agendas and guiding the appropriate presentation of research findings to meet the needs of potential readers.
Achieving waiting list reform: a pilot program integrating waiting time, category and patient factors
Authors: Siddins Mark T. , Boland John , Mathews Brian , Swanborough Perry
Published: August 2012

Equity in resource allocation is central to the tenet of social justice in health care. The management of surgical waiting lists is of critical importance to clinicians, patients and regulators. In most hospital environments, the basic process has remained unchanged for decades. Patients are assigned to one of three urgency-related categories. Clinicians consequently administer three competing patient pools. The basis by which patients are selected for treatment may be difficult to define. The specific clinical circumstances of each patient are often unreported and may be unknown to those administering the list. Waiting list bias is also recognised. This may reflect clinician advocacy, pressure to meet category timeframe restrictions or perceived training requirements. In this environment, it is difficult to demonstrate propriety in care. We report the implementation of a pilot program to redesign waiting list management within a South Australian public hospital unit. This allows assemblage of patients into a single list. Overall priority is determined by balancing clinical acuity and waiting time. The determination of acuity takes into account both the primary category and the specific characteristics of each patient that are relevant to their intended procedure. Uniquely, the process is applicable to lists containing patients with dissimilar conditions. This paper reviews the limitations of current approaches in meeting reasonable community expectations. The principles and social justification underpinning this reform are introduced. Finally, the benefits offered by the program are discussed and interim results are reported. What is known about this topic? Current models for the management of hospital waiting lists have remained largely unchanged for several decades. Typically patients are allocated to urgent, semi-urgent and non-urgent categories of care. No methodology exists to systematically integrate these groups, or to account for specific patient factors. In this void, propriety in management is difficult to establish or defend. What does this paper add? A program is reported that unifies all categories of patients into a single prioritised waiting list. The order of patients is dynamic, and transparently reflects waiting time, category assignment and relevant individual patient factors. Uniquely, the program is applicable to lists containing patients with diverse clinical conditions. What are the implications for clinicians? Adoption of new technology is essential if reasonable community expectations in waiting list management are to be met. The current program provides unambiguous, defensible prioritisation of all patients awaiting care. The present reliance on individual managers is reduced, and the unique circumstances of each patient are recognised. We believe this approach affords significant benefit to patients, practitioners and regulators.
Aluminium Nanowire Electrodes for Lithium-Ion Batteries
Authors: El Abedin Sherif Zein , Garsuch Arnd , Endres Frank
Published: August 2012

In this paper, we report on the fabrication of mechanically stable aluminium nanowire electrodes for application in lithium-ion batteries. The electrochemical synthesis of the nanowire electrodes was performed in the chloroaluminate ionic liquid 1-ethyl-3-methylimidazolium chloride [EMIm]Cl/AlCl3 (40:60 mol %) using polycarbonate templates. The fabricated nanowire electrodes exhibit high mechanical stability after 50 cycles of lithium deposition/stripping without significant disintegration of the nanowire structure. The mechanical stability and strong adhesion of the Al-nanowires with the electrodeposited Al-electrode can lead to long cycling life. The fabricated Al-nanowire electrodes deliver a capacity of 790 mAh g–1 at 1C-rate.
Human food preferences and cultural identity: The case of Aragón (Spain)
Authors: Cantarero Luis , Espeitx Elena , Gil Lacruz Marta , Martín Pilar
Published: August 2012

This research aims to analyze the relationship between sociocultural values and human food preferences. The latter, as shown in this paper, are greatly influenced by cultural identity. This work stems from a theoretical context that originated in Europe and the United States towards the mid‐twentieth century, within the field of the anthropology of food. A qualitative and quantitative analysis has been performed in the Comunidad Autónoma de Aragón (Spain). Research methods include focus groups, in‐depth interviews, participant observation, and a questionnaire that was handed out to a representative sample of the Aragonese population (816 people over 21 years of age; confidence level of 95.5% and error margin of ±3.5). Regarding the research outcome, a highly significant qualitative and quantitative connection has been found between food selection and cultural identity. In other words, people prefer to consume foods that are symbolically associated with their own culture, in order to reinforce their sense of belonging. Although this study has been carried out in Aragón, it is our belief that the results can be generalized to other areas. The originality and interest of our findings are notable considering that, to date, few works have analyzed the sociocultural factors motivating food behavior. Moreover, these results could be used by public and private organizations to meet objectives such as health promotion and product marketing.
Independence or interdependence
Authors: Luetzelberger Therese
Published: August 2012

This article contributes to understanding the relatively early residential independence of young Northern Europeans, by comparison to their Southern European peers. It explores the norms and underlying meanings that influence the departure from the parental home and the feelings attached to it. Analysing qualitative, biographically oriented interviews with Italian and German university students and their parents (43 participants), two patterns are identified. The first is an ‘independence’ pattern, which prioritizes the importance of leaving home in order to grow up. The second is an ‘interdependence’ pattern which supports the togetherness of the family and sees the family home as the best environment for young adults –i.e., they leave home only for ‘inevitable’ reasons related to work, education, or family formation. Both patterns are handed down over generations and are transmitted in the socialization process.
A mild generalization of Eisenstein’s criterion
Authors: Weintraub Steven
Published: August 2012

We state and prove a mild generalization of Eisenstein’s Criterion for a polynomial to be irreducible, correcting an error that Eisenstein made himself.
On the preperiodic points of an endomorphism of ℙ¹×ℙ¹ which lie on a curve
Authors: Mimar Arman
Published: August 2012

Let

X
X

be a projective curve in

P

1

×

P

1

\mathbb {P}^{1} \times \mathbb {P}^{1}

and

φ
\varphi

be an endomorphism of degree

≥
2

\geq 2

of

P

1

×

P

1

\mathbb {P}^{1} \times \mathbb {P}^{1}

, given by two rational functions by

φ
(
z
,
w
)
=
(
f
(
z
)
,
g
(
w
)
)

\varphi (z,w)=(f(z),g(w))

(i.e.,

φ
=
f
×
g

\varphi =f \times g

), where all are defined over

Q

¯

\overline {\mathbb {Q}}

. In this paper, we prove a characterization of the existence of an infinite intersection of

X
(

Q

¯

)

X(\overline {\mathbb {Q}})

with the set of

φ
\varphi

-preperiodic points in

P

1

×

P

1

\mathbb {P}^{1} \times \mathbb {P}^{1}

, by means of a binding relationship between the two sets of preperiodic points of the two rational functions

f
f

and

g
g

, in their respective

P

1

\mathbb {P}^{1}

-components. In turn, taking limits under the characterization of the Julia set of a rational function as the derived set of its preperiodic points, we obtain the same relationship between the respective Julia sets

J

(
f
)

\mathcal {J}(f)

and

J

(
g
)

\mathcal {J}(g)

as well. We then find various sufficient conditions on the pair

(
X
,
φ
)

(X,\varphi )

and often on

φ
\varphi

alone, for the finiteness of the set of

φ
\varphi

-preperiodic points of

X
(

Q

¯

)

X(\overline {\mathbb {Q}})

. The finiteness criteria depend on the rational functions

f
f

and

g
g

, and often but not always, on the curve. We consider in turn various properties of the Julia sets of

f
f

and

g
g

, as well as their interactions, in order to develop such criteria. They include: topological properties, symmetry groups as well as potential theoretic properties of Julia sets.
Sum formulas for local Gromov-Witten invariants of spin curves
Authors: Lee Junho
Published: August 2012

Holomorphic 2-forms on Kähler surfaces lead to “local Gromov-Witten invariants” of spin curves. This paper shows how to derive sum formulas for such local GW invariants from the sum formula for GW invariants of certain ruled surfaces. These sum formulas also verify the Maulik-Pandharipande formulas that were recently proved by Kiem and Li.
Multilevel regulation of HIF-1 signaling by TTP
Authors: Fähling Michael , Persson Anja Bondke , Klinger Bertram , Benko Edgar , Steege Andreas , Kasim Mumtaz , Patzak Andreas , Persson Pontus B. , Wolf Gunter , Blüthgen Nils , Mrowka Ralf
Published: August 2012

Hypoxia-inducible factor-1 (HIF-1) is a well-studied transcription factor mediating cellular adaptation to hypoxia. It also plays a crucial role under normoxic conditions, such as in inflammation, where its regulation is less well understood. The 3′-untranslated region (UTR) of HIF-1α mRNA is among the most conserved UTRs in the genome, hinting toward posttranscriptional regulation. To identify potential trans factors, we analyzed a large compilation of expression data. In contrast to its known function of being a negative regulator, we found that tristetraprolin (TTP) positively correlates with HIF-1 target genes. Mathematical modeling predicts that an additional level of posttranslational regulation of TTP can explain the observed positive correlation between TTP and HIF-1 signaling. Mechanistic studies revealed that TTP indeed changes its mode of regulation from destabilizing to stabilizing HIF-1α mRNA upon phosphorylation by p38 mitogen-activated protein kinase (MAPK)/MAPK-activated protein kinase 2. Using a model of monocyte-to-macrophage differentiation, we show that TTP-driven HIF-1α mRNA stabilization is crucial for cell migration. This demonstrates the physiological importance of a hitherto-unknown mechanism for multilevel regulation of HIF-1α in normoxia.
Matrix compliance regulates Rac1b localization, NADPH oxidase assembly, and epithelial–mesenchymal transition
Authors: Lee KangAe , Chen Qike K. , Lui Cecillia , Cichon Magdalena A. , Radisky Derek C. , Nelson Celeste M.
Published: August 2012

Epithelial–mesenchymal transition (EMT) is a form of epithelial plasticity implicated in fibrosis and tumor metastasis. Here we show that the mechanical rigidity of the microenvironment plays a pivotal role in the promotion of EMT by controlling the subcellular localization and downstream signaling of Rac GTPases. Soft substrata, with compliances comparable to that of normal mammary tissue, are protective against EMT, whereas stiffer substrata, with compliances characteristic of breast tumors, promote EMT. Rac1b, a highly activated splice variant of Rac1 found in tumors, localizes to the plasma membrane in cells cultured on stiff substrata or in collagen-rich regions of human breast tumors. At the membrane, Rac1b forms a complex with NADPH oxidase and promotes the production of reactive oxygen species, expression of Snail, and activation of the EMT program. In contrast, soft microenvironments inhibit the membrane localization of Rac1b and subsequent redox changes. These results reveal a novel mechanotransduction pathway in the regulation of epithelial plasticity via EMT.