bluuebunny/crossref_metadata_2025 huggingface dataset:
Atomic Resolution Phase Contrast Imaging and In-Line Holography Using Variable Voltage and Dose Rate
Authors: Barton Bastian , Jiang Bin , Song ChengYu , Specht Petra , Calderon Hector , Kisielowski Christian
Published: October 2012

The TEAM 0.5 electron microscope is employed to demonstrate atomic resolution phase contrast imaging and focal series reconstruction with acceleration voltages between 20 and 300 kV and a variable dose rate. A monochromator with an energy spread of ≤0.1 eV is used for dose variation by a factor of 1,000 and to provide a beam-limiting aperture. The sub-Ångstrøm performance of the instrument remains uncompromised. Using samples obtained from silicon wafers by chemical etching, the [200] atom dumbbell distance of 1.36 Å can be resolved in single images and reconstructed exit wave functions at 300, 80, and 50 kV. At 20 kV, atomic resolution <2 Å is readily available but limited by residual lens aberrations at large scattering angles. Exit wave functions reconstructed from images recorded under low dose rate conditions show sharper atom peaks as compared to high dose rate. The observed dose rate dependence of the signal is explained by a reduction of beam-induced atom displacements. If a combined sample and instrument instability is considered, the experimental image contrast can be matched quantitatively to simulations. The described development allows for atomic resolution transmission electron microscopy of interfaces between soft and hard materials over a wide range of voltages and electron doses.
The rapid recovery of 5-HT cell firing induced by the antidepressant vortioxetine involves 5-HT3 receptor antagonism
Authors: Bétry Cécile , Pehrson Alan L. , Etiévant Adeline , Ebert Bjarke , Sánchez Connie , Haddjeri Nasser
Published: October 2012

The therapeutic effect of current antidepressant drugs appears after several weeks of treatment and a significant number of patients do not respond to treatment. Here, we report the effects of the multi-modal antidepressant vortioxetine (Lu AA21004), a 5-HT3 and 5-HT7 receptor antagonist, 5-HT1B receptor partial agonist, 5-HT1A receptor agonist and 5-HT transporter (SERT) inhibitor, on rat 5-HT neurotransmission. Using in vivo electrophysiological recordings in the dorsal raphe nucleus of anaesthetized rats, we assessed the acute and subchronic effects of vortioxetine and/or the selective 5-HT3 receptor agonist, SR57227 or the selective 5-HT1A receptor agonist flesinoxan, on 5-HT neuronal firing activity. Using ex-vivo autoradiography, we correlated SERT occupancy and presumed 5-HT firing activity. The selective serotonin reuptake inhibitor, fluoxetine, was used as comparator. Importantly, the recovery of 5-HT neuronal firing was achieved after 1 d with vortioxetine and 14 d with fluoxetine. SR57227 delayed this recovery. In contrast, vortioxetine failed to alter the reducing action of 3 d treatment of flesinoxan. Acute dosing of vortioxetine inhibited neuronal firing activity more potently than fluoxetine. SR57227 prevented the suppressant effect of vortioxetine, but not of fluoxetine. In contrast, flesinoxan failed to modify the suppressant effect of vortioxetine acutely administered. Differently to fluoxetine, vortioxetine suppressed neuronal firing without saturating occupancy at the SERT. Vortioxetine produced a markedly faster recovery of 5-HT neuronal firing than fluoxetine. This is at least partly due to 5-HT3 receptor antagonism of vortioxetine in association with its reduced SERT occupancy.
Adsorption of nucleic acid bases on magnesium oxide (MgO)
Authors: Fornaro Teresa , Brucato John Robert , Branciamore Sergio , Pucci Amaranta
Published: October 2012

The adsorption of organic molecules on mineral matrices might have played a fundamental role in processes that led to the emergence of life. We investigated the adsorption properties of the nucleobases adenine, cytosine, uracil and hypoxanthine on magnesium oxide (MgO), determining the single solute batch equilibrium adsorption isotherms. Langmuir-type isotherms were fitted to data, assuming a rapid reversible equilibration of adsorption, demonstrated effectively through desorption experiments. The Langmuir equilibrium adsorption constantKand the amount of the solute per unit of adsorbent mass necessary to complete the monolayerbwere calculated. The results indicate that MgO is a good adsorbent for nucleobases (adenine > uracil > hypoxantine > cytosine), suggesting a role of metal oxides in concentrating biomolecules in prebiotic conditions that might have favoured the passage from geochemistry to biochemistry.
A high-speed buck converter for efficiency enhancement of W-CDMA power amplifiers
Authors: Haßler Falk , Ellinger Frank , Jörges Udo , Wolf Robert , Lindner Bastian
Published: October 2012

We present a design strategy for a buck converter, which fulfills the high dynamic requirements of efficient envelope amplifier needed by modern efficiency enhancement techniques for power amplifiers. The proposed DC–DC converter has an innovative control system, which makes it fast, robust, and resource saving. A mathematical model describes its dynamic behavior and is used to find a setup, which gives an optimal compromise between the dynamic performance and efficiency. The approach is applicable to various state-of-the-art communication standards. As an example, an envelope following (EF) power amplifier (PA) for the wideband code-division-multiple-access (W-CDMA) modulation scheme is treated. The corresponding buck converter is implemented in a monolithic chip (except the inductor and the capacitor of the output filter). The measurements with an industry standard W-CDMA PA (RMPA2265) match very well with the forecast of the model and confirm doubling of the average efficiency.
Emergency department staff views and experiences on diagnostic overshadowing related to people with mental illness
Authors: van Nieuwenhuizen A. , Henderson C. , Kassam A. , Graham T. , Murray J. , Howard L. M. , Thornicroft G.
Published: October 2012

Aims.

To investigate recognition of diagnostic overshadowing, i.e., misattribution of physical symptoms to mental illness, among emergency medicine professionals; further, to identify contributory and mitigating factors to diagnostic overshadowing.

Methods.

In-depth individual interviews of 25 emergency department clinicians and qualitative analysis using thematic analysis.

Results.

Diagnostic overshadowing was described as a significant issue. Contributing factors included: (1) problems of knowledge and information gathering; (2) clinicians' attitudes toward people with mental illness, substance misuse and frequent attenders; and (3) difficulties in working with mental health services in the context of a 4-h target for discharge from the emergency department. Avoidance of patients with a psychiatric diagnosis was also described, due to fear of violence.

Conclusion.

The physical health care of people with mental illness in emergency departments may be adversely affected by diagnostic overshadowing and avoidance by clinical staff, along with difficulties created by the illness, medication and the emergency department environment. Greater joint working between psychiatric and emergency department staff is suggested as one way to reduce diagnostic overshadowing.
Studierende schieben Pflichten auf, aber auch persönliche Projekte
Authors: Grund Axel , Schmid Sebastian , Klingsieck Katrin B. , Fries Stefan
Published: October 2012

Die Forschung zum Thema Prokrastination betrachtet fast ausschließlich das Aufschieben von Handlungen, die als fremdbestimmte Verpflichtungen und Leistungshandlungen wahrgenommen werden und die zugunsten von attraktiveren Handlungsalternativen zurückgestellt werden. Am Beispiel der Alltagshandlungen Studierender wurde untersucht, inwieweit dieses Begriffsverständnis bestimmte phänomenologische Facetten vernachlässigt. 398 Studierende beschrieben aufgeschobene und stattdessen ausgeführte Alltagshandlungen einer konkreten Aufschiebeepisode anhand von 35 Merkmalen. Anschließend wurde mit Analysen latenter Profile überprüft, inwieweit sich typische Handlungsprofile unterscheiden und interpretieren lassen. Es konnten je drei distinkte Typen aufgeschobener und ausgeführter Handlungen identifiziert werden. Erstere lassen sich anhand ihrer wahrgenommenen Merkmalsprofile als Pflichthandlungen, persönliche Projekte und Aktivhandlungen beschreiben; letztere als Entspannungshandlungen, Sozialhandlungen und wiederum Pflichthandlungen. Die Profile von persönlichen Projekten und Aktivhandlungen zeigen, dass das Spektrum von aufgeschobenen Handlungen breiter ist, als in der Forschung zumeist vorausgesetzt wird. Vor dem Hintergrund dieser Befunde wird dafür argumentiert, die Konzeption und Erfassung von Prokrastination auf selbstbestimmte Handlungen und Aktivhandlungen zu erweitern.
NSF advisory committee examines realignment plan
Authors: Showstack Randy
Published: October 2012

The U.S. National Science Foundation's (NSF) plan to move the Office of Polar Programs (OPP) back into the Directorate for Geosciences (GEO) was prompted by organizational efficiency, potential synergy between the two, timing, and other factors, NSF director Subra Suresh told members of the Advisory Committee for Geosciences during its 11–12 October meeting. The group, which is a federal advisory committee to NSF, also focused on the search for a permanent associate director for the geosciences directorate, the budget, and workload and infrastructure issues.
Coffee and copy, deadlines and cutlines: The lessons of a scientist turned reporter
Authors: Morrison Jessica M.
Published: October 2012

I'm a scientist, and I drink coffee. Now, I know what you're thinking, “So what? We're all scientists. We all drink coffee.”—but I didn't. Not until I left my laboratory bench at the University of Notre Dame, journeying deep into the foreign land of newspaper journalism, did I learn to appreciate a slow drip alongside the morning hustle.
Tracking the Antarctic water flows that feed the Benguela Current
Authors: Schultz Colin
Published: October 2012

As the initiator of the northbound branch of the Atlantic Meridional Overturning Circulation (AMOC), the Benguela Current is a key component in the large‐scale circulation system that transports energy, salt, and biogeochemical tracers around the Atlantic basin. Water flowing in the Benguela Current derives from several sources, but the bulk originates as Antarctic Intermediate Water (AAIW). The relatively fresh AAIW is formed when northbound water from the Antarctic Circumpolar Current sinks below warmer northern waters. AAIW's depth and salinity varies depending on where it is formed. AAIW from both the Atlantic and Indian oceans feeds the Benguela Current, so knowing its properties and pathways is important for understanding AMOC. After performing a particle‐tracking analysis in a high‐resolution regional ocean circulation model, Rimaud et al. calculated how AAIW of the Indian and Atlantic oceans evolve into the Benguela Current.
China's Changbaishan volcano showing signs of increased activity
Authors: Schultz Colin
Published: October 2012

Roughly 1100 years ago, the Changbaishan volcano that lies along the border between northeastern China and North Korea erupted, sending pyroclastic flows dozens of kilometers and blasting a 5‐kilometer‐wide chunk off of the tip of the stratovolcano. The eruption, known as the Millennium eruption because of its proximity to the turn of the first millennium, was one of the largest volcanic events in the Common Era. In the subsequent period, there have been three smaller eruptions, the most recent of which took place in 1903. Starting in 1999, spurred by signs of resumed activity, scientists established the Changbaishan Volcano Observatory, a network to track changing gas compositions, seismic activity, and ground deformation. Reporting on the data collected over the past 12 years, Xu et al. found that these volcanic indices each leapt during a period of heightened activity from 2002 to 2006.
Effect of an MLT dependent electron loss rate on the magnetosphere‐ionosphere coupling
Authors: Gkioulidou Matina , Wang Chih‐Ping , Wing Simon , Lyons Larry R. , Wolf Richard A. , Hsu Tung‐Shin
Published: October 2012

As plasma sheet electrons drift earthward, they get scattered into the loss cone due to wave‐particle interactions and the resulting precipitation produces auroral conductance. Realistic electron loss is thus important for modeling the magnetosphere ‐ ionosphere (M‐I) coupling and the degree of plasma sheet electron penetration into the inner magnetosphere. In order to evaluate the significance of electron loss, we used the Rice Convection Model (RCM) coupled with a force‐balanced magnetic field to simulate plasma sheet transport under different electron loss rates and under self‐consistent electric and magnetic field. We used different magnitudes of i) strong pitch angle diffusion everywhere electron loss rate (strong rate) and ii) a more realistic loss rate with its MLT dependence determined by wave activity (MLT rate). We found that electron pressure under the MLT rate is larger compared to the strong rate inside L ∼ 12 RE. The dawn‐dusk asymmetry in the precipitating electron energy flux under the MLT rate, with much higher energy flux at dawn than at dusk, agrees better with statistical DMSP observations. High‐energy electrons inside L ∼ 8 RE can remain there for many hours under the MLT rate, while those under the strong rate get lost within minutes. Under the MLT rate, the remaining electrons cause higher conductance at lower latitudes; thus after a convection enhancement, the shielding of the convection electric field is less efficient, and as a result, the ion plasma sheet penetrates further earthward into the inner magnetosphere than under the strong rate.
Numerical analysis of the effect of momentum ratio on the dynamics and sediment‐entrainment capacity of coherent flow structures at a stream confluence
Authors: Constantinescu George , Miyawaki Shinjiro , Rhoads Bruce , Sukhodolov Alexander
Published: October 2012

The flow and turbulence structure at stream confluences are characterized by the formation of a mixing interface (MI) and, in some cases, of streamwise‐oriented vortical (SOV) cells flanking the MI. Depending on the junction angle and planform symmetry, as well as the velocity ratio across the MI, the MI can be in the Kelvin‐Helmholtz (KH) mode or in the wake mode. In the former case, the MI contains predominantly co‐rotating large‐scale quasi two‐dimensional (2‐D) eddies whose growth is driven by the KH instability and vortex pairing. In the latter case, the MI is populated by quasi 2‐D eddies with opposing senses of rotation. This study uses eddy resolving simulations to predict details of flow structure for KH‐ and wake‐mode conditions at a confluence for which field measurements are available. Results indicate that SOV cells at this confluence, which occur in both modes, redistribute momentum and mass, enhancing the potential for entrainment of bed material beneath the cells and for extraction of fluid and suspended sediment from the MI. The simulations predict that the cores of some of the primary SOV cells are subject to large‐scale bimodal oscillations toward and away from the MI that contribute to amplification of the turbulence close to the MI and enhance the capacity of the SOV cells to entrain sediment. At this confluence, which has a concordant bed and a large angle between the incoming streams ‐ conditions that generate strong adverse lateral pressure gradients adjacent to the MI ‐ the oscillating SOV cells interact with MI eddies to generate large bed friction velocities in the zone of scour immediately downstream of the confluence.
Ring opening polymerization of mannosyl tricyclic orthoesters: rationalising the stereo and regioselectivity of glycosidic bond formation using quantum chemical calculations
Authors: Boonyarattanakalin Siwarutt , Ruchirawat Somsak , Gleeson M. Paul
Published: October 2012

Quantum chemical methods have been used to assess the physico-chemical origin of the stereo and regio-selectivity during glycosyl tricyclic orthoester polymerization. The subtle modulation of steric and electronic factors dramatically influences the reaction.
Structure–activity relationship studies using peptide arrays: the example of HIV-1 Rev–integrase interaction
Authors: Gabizon Ronen , Faust Ofrah , Benyamini Hadar , Nir Sivan , Loyter Abraham , Friedler Assaf
Published: October 2012

We used peptide arrays to perform structure–activity relationship studies on anti-HIV peptides derived from HIV-1 integrase.
Electrical hypothesis of toxicity of the Cry toxins for mosquito larvae
Authors: Lemeshko Victor V. , Orduz Sergio
Published: October 2012

Many electrical properties of insect larval guts have been studied, but their importance for toxicity of the Cry-type toxins has never been reported in the literature. In the present work, we observed potential-dependent permeabilization of plasma membrane by several polycationic peptides derived from the Cry11Bb protoxin. The peptide BTM-P1d, all D-type amino acid analogue of the earlier reported peptide BTM-P1, demonstrated high membrane-permeabilizing activity in experiments with isolated rat liver mitochondria, RBC (red blood cells) and mitochondria in homogenates of Aedes aegypti larval guts. Two larger peptides, BTM-P2 and BTM-P3, as well as the Cry11Bb protoxin treated with the protease extract of mosquito larval guts showed similar effects. Only protease-resistant BTM-P1d, in comparison with other peptides, displayed A. aegypti larval toxicity. Taking into account the potential-dependent mechanism of membrane permeabilization by studied fragments of the Cry11Bb protoxin and the literature data related to the distribution of membrane and transepithelial potentials in the A. aegypti larval midgut, we suggest an electrical hypothesis of toxicity of the Cry toxins for mosquito larvae. According to this hypothesis, the electrical field distribution is one of the factors determining the midgut region most susceptible for insertion of activated toxins into the plasma membrane to form pores. In addition, potential-dependent penetration of short active toxin fragments into the epithelial cells could induce permeabilization of mitochondria and subsequent apoptosis or necrosis.
Method for investigating threshold field of charge injection at electrode/dielectric interfaces by space charge observation
Authors: An Zhenlian , Cang Jun , Chen Xuan , Liu Yaqiang
Published: October 2012

We propose a dielectric sample model to investigate the threshold field for charge injection at electrode/dielectric interfaces by space charge observation. The model sample consists of a dielectric layer and two thin charge blocking layers, respectively, placed at the inside and one side of the dielectric layer. The method has been applied to investigate the threshold field for charge injection from Al, Au, or semiconductive electrode into polyethylene. Experimental results show that charge injection occurs so long as the interface electric field is nonzero, i.e., there is no indication of a threshold field for the charge injection.
The embedded many-body expansion for energetics of molecular crystals
Authors: Bygrave P. J. , Allan N. L. , Manby F. R.
Published: October 2012

Reliable prediction of molecular crystal energetics is a vital goal for computational chemistry. Here we show that accurate results can be obtained from a monomer-based many-body expansion truncated at the two-body level, with the monomer and dimer calculations suitably embedded in a model of the crystalline environment. By including the two dominant effects—electrostatics and exchange-repulsion—we are able to capture the important nonadditive terms in the energy, and approach very closely results from full periodic second-order Møller-Plesset calculations. The advantage of the current scheme is that extension to coupled-cluster and explicitly correlated F12 methods is completely straightforward. We demonstrate the approach through calculations on carbon dioxide, hydrogen fluoride, and ice XIh and XIc. In accord with previous studies, we find these two ice polymorphs to be very close in energy, with our periodic coupled-cluster single double triple-F12 calculation giving the hexagonal structure more stable by around 0.3 kJ mol−1.
Darboux transformations for (1+2)-dimensional Fokker-Planck equations with constant diffusion matrix
Authors: Schulze-Halberg Axel
Published: October 2012

We construct a Darboux transformation for (1+2)-dimensional Fokker-Planck equations with constant diffusion matrix. Our transformation is based on the two-dimensional supersymmetry formalism for the Schrödinger equation. The transformed Fokker-Planck equation and its solutions are obtained in explicit form.
Omnidirectional reflection from nanocolumnar TiO2 films
Authors: Leontyev Viktor , Hawkeye Matthew , Kovalenko Andriy , Brett Michael J.
Published: October 2012

Anisotropic properties of columnar nanoporous thin films were utilized to design and fabricate interference mirrors with lossless omnidirectional reflection in the visible spectral range. Index graded columnar films with distributed Bragg reflector (DBR), sinusoidal, and Gaussian refractive index profiles were studied using finite-difference frequency-domain and finite-difference time-domain methods, with an emphasis on maximizing the omnidirectional reflection bandwidth. Titanium dioxide columnar films with sixteen period sinusoidal refractive index profile were fabricated using the glancing angle deposition technique and characterized by angle resolved transmittance measurements. Simulations and experimental measurements have shown the presence of the omnidirectional reflection band up to 5% wide for a film with a maximum refractive index nmax=2.3 and refractive index contrast Δn=0.8. Simulations further showed that with the optimal choice of the refractive index variation range, the omnidirectional reflection band can reach 10.5% width in TiO2 films with a sinusoidal index profile, 14.5% with a DBR index profile, and 12% with a Gaussian profile. Due to the optical anisotropy of the columnar films, the reflection bandwidth exceeded the corresponding value, observed in isotropic analogs, by a factor of three to four depending on the choice of the refractive index profile.
Structure and mechanical properties of tantalum mononitride under high pressure: A first-principles study
Authors: Chang Jing , Zhao Guo-Ping , Zhou Xiao-Lin , Liu Ke , Lu Lai-Yu
Published: October 2012

The structure and mechanical properties of tantalum mononitride (TaN) are investigated at high pressure from first-principles using the plane wave pseudopotential method within the local density approximation. Three stable phases were considered, i.e., two hexagonal phases (ε and θ) and a cubic δ phase. The obtained equilibrium structure parameters and ground state mechanical properties are in excellent agreement with the experimental and other theoretical results. A full elastic tensor and crystal anisotropy of the ultra-incompressible TaN in three stable phases are determined in the wide pressure range. Results indicated that the elastic properties of TaN in three phases are strongly pressure dependent. And the hexagonal θ-TaN is the most ultraincompressible among the consider phases, which suggests that the θ phase of TaN is a potential candidate structure to be one of the ultraincompressible and hard materials. By the elastic stability criteria, it is predicted that θ-TaN is not stable above 53.9 GPa. In addition, the calculated B/G ratio indicated that the ε and δ phases possess brittle nature in the range of pressure from 0 to 100 GPa. While θ phase is brittleness at low pressure (below 8.2 GPa) and is strongly prone to ductility at high pressure (above 8.2 GPa). The calculated elastic anisotropic factors for three phases of TaN suggest that they are elastically highly anisotropic and strongly dependent on the propagation direction.
Thermoelectric properties of lattice matched InAlN on semi-insulating GaN templates
Authors: Sztein Alexander , Bowers John E. , DenBaars Steven P. , Nakamura Shuji
Published: October 2012

The thermoelectric properties of nearly lattice matched n-type InxAl1−xN (x ≈ 0.18) grown by metal organic chemical vapor deposition (MOCVD) are investigated with particular attention to the potentially conductive GaN template and InAlN/GaN interfacial polarization charges. The thermoelectric properties of InAlN are measured over a range of carrier densities and through temperatures as high as 815 K. The maximum room temperature ZT was found to be 0.007 at a carrier density of 6.4 × 1019 cm−3. The ZT of InAlN at this carrier density increases to 0.05 at 815 K. It is also shown that the interfacial charge in InAlN/GaN structures and the resulting two dimensional electron gas (2DEG) lead to greatly improved electron mobility and power factor when 2DEG conduction is dominant. Using this strategy, a 250% improvement in power factor is realized as the thickness of InAlN is decreased from 290 nm to 34 nm. Methods for extending these power factor enhancements to thicker materials are discussed.
Vascularization for cooling a plate heated by a randomly moving source
Authors: Cetkin E. , Lorente S. , Bejan A.
Published: October 2012

Here, we show that a plate heated by a moving beam can be cooled effectively by fluid that flows through a vasculature of channels embedded in the plate. The vascular designs studied are radial, grid and hybrid (radial + grid). The peak temperature of the plate changes with the path and direction of the moving beam. The strength, size and speed of the beam vary. The peak temperature increases as the beam strength and size increase and as the speed of the beam decreases. The grid and hybrid designs are robust because of loops present in the flow structure. The pressure difference that drives the fluid flow varied. The channel diameter ratios that provide greatest flow access are reported. The cooling performance of the multiscale grid structures is less sensitive to the changes in beam path than the cooling performance of the other structures studied. The effect of adding a vascular structure to the design is dramatic.
Glassy magnetic ground state in La4/3Sr5/3Mn2O7: Role of first order phase transition and short range antiferromagnetic correlations
Authors: Chattopadhyay S. , Giri S. , Majumdar S.
Published: October 2012

We report the observation of reentrant spin glass state in the bilayered manganite with nominal composition La4/3Sr5/3Mn2O7. The studied compound transforms from a high temperature paramagnetic phase with antiferromagnetic type short range magnetic correlation to a ferromagnetic phase upon cooling. On further cooling, the long range ferromagnetic phase is destroyed leading to glassy magnetic phase. Our ac susceptibility analysis indicates the possibility of the existence of frozen spin clusters below the spin glass transition temperature. The cooling rate and cooling field dependence of magnetization measurements reveal that the glassy phase is closely connected with the arrested kinetics of the first order phase transition leading to the existence of antiferromagnetic/paramagnetic clusters along with the ferromagnetic phase at low temperature.
Dynamical thermal conductivity of bulk semiconductor crystals
Authors: Ezzahri Younès , Joulain Karl
Published: October 2012

The paper discusses the behavior of the dynamical lattice thermal conductivity κ(Ω) of bulk semiconductor crystals. The calculation approach is based on solving Boltzmann-Peierls phonon transport equation in the frequency domain after excitation by a dynamical temperature gradient, within the framework of the single relaxation time approximation and using modified Debye-Callaway model. Our model allows us to obtain a compact expression for κ(Ω) that captures the leading behavior of the dynamical thermal conduction by phonons. This expression fulfils the causality requirement and leads to a convolution type relationship between the heat flux density current and the temperature gradient in the real space-time domain in agreement with Gurtin-Pipkin theory. The dynamical behavior of κ(Ω) is studied by changing temperature as well as different intrinsic and extrinsic parameters. Our calculations show the cut-off frequency of κ(Ω) to be sensitive to the changes of some of these parameters. The paper investigates also the applicability of Shastry's sum rule (SSR) in the frame work of Boltzmann theory. It is shown that within the frame work of Callaway approximated form of the collision operator and time independent Callaway parameter, the SSR breaks down and is only valid when resistive processes dominate normal processes, for which case, we derive an alternative expression to the classical limit of the expectation of the thermal operator introduced in Shastry's formalism.
Effect of length scale on mechanical properties of Al-Cu eutectic alloy
Authors: Tiwary C. S. , Roy Mahapatra D. , Chattopadhyay K.
Published: October 2012

This paper attempts a quantitative understanding of the effect of length scale on two phase eutectic structure. We first develop a model that considers both the elastic and plastic properties of the interface. Using Al-Al2Cu lamellar eutectic as model system, the parameters of the model were experimentally determined using indentation technique. The model is further validated using the results of bulk compression testing of the eutectics having different length scales.
Enhanced photocurrent and conversion efficiency in thin-film microcrystalline silicon solar cells using periodically textured back reflectors with hexagonal dimple arrays
Authors: Sai Hitoshi , Saito Kimihiko , Kondo Michio
Published: October 2012

Periodically textured back reflectors with hexagonal dimple arrays are applied to thin-film microcrystalline silicon (μc-Si:H) solar cells for enhancing their photon absorption and photovoltaic performance. In a systematic survey of 1 -μm-thick μc-Si:H cells, the best performance is obtained with a period of 1.5 μm and an aspect ratio of 0.20–0.25 with a high current density exceeding 26 mA/cm2 and a marked efficiency of 10.1%. These results demonstrate the high potential of periodic textures or surface gratings for improving the conversion efficiency of thin-film silicon solar cells.
Nanowire array photovoltaics: Radial disorder versus design for optimal efficiency
Authors: Sturmberg Björn C. P. , Dossou Kokou B. , Botten Lindsay C. , Asatryan Ara A. , Poulton Christopher G. , McPhedran Ross C. , Martijn de Sterke C.
Published: October 2012

Solar cell designs based on disordered nanostructures tend to have higher efficiencies than structures with uniform absorbers, though the reason is poorly understood. To resolve this, we use a semi-analytic approach to determine the physical mechanism leading to enhanced efficiency in arrays containing nanowires with a variety of radii. We use our findings to systematically design arrays that outperform randomly composed structures. An ultimate efficiency of 23.75% is achieved with an array containing 30% silicon, an increase of almost 10% over a homogeneous film of equal thickness.
Poole-Frenkel emission in epitaxial nickel oxide on AlGaN/GaN heterostructures
Authors: Fiorenza Patrick , Greco Giuseppe , Giannazzo Filippo , Lo Nigro Raffaella , Roccaforte Fabrizio
Published: October 2012

In this letter, the conduction mechanism through epitaxial nickel oxide (NiO) dielectric films grown by metal-organic chemical vapor deposition on AlGaN/GaN heterostructures was investigated. In particular, macroscopic current-voltage measurements carried out at different temperatures allowed to demonstrate that Poole-Frenkel (PF) mechanism rules the conduction through the dielectric layer, with an emission barrier of 0.2 eV. Conductive atomic force microscopic measurements were carried out to directly image the presence of preferential current spots on the NiO surface, which have been correlated to the defects responsible for the PF emission.
Effective magnetic anisotropy of annealed FePt nanoparticles
Authors: Usov N. A. , Barandiarán J. M.
Published: October 2012

The hysteresis loops of randomly oriented assembly of FePt nanoparticles are calculated numerically as a function of particle diameter for the range of the effective anisotropy constants, Kef = 1-5 × 107 erg/cm3, taking into account the effect of thermal fluctuations. Very sharp dependence of the assembly coercive force on the particle diameter is found for Kef  ≥ 3 × 107 erg/cm3. The effective anisotropy constant of annealed FePt nanoparticle is estimated assuming the existence of L10 inclusions distributed randomly in a magnetically soft surrounding matrix. The hysteresis loop evolution can be explained if the total volume of the L10 grains is supposed to increase during annealing.
Ordered graphene strips onto polymer backing prepared by laser scanning
Authors: Lyutakov O. , Huttel I. , Tuma J. , Kalbac M. , Janousek M. , Šimek P. , Svorcik V.
Published: October 2012

The preparation of ordered array of graphene strips with arc lateral shape on graphene layer is described. In the next step, porphyrine doped polymer film was deposited onto graphene and the substrate was dissolved and the graphene film was revealed. Polymer film was modified by scanning laser beam and simultaneous mechanical movement of the sample. The creation of graphene ordered strips relies on graphene cutting due to polymer substrate distortion. Creation of ordered graphene strips was proved by scanning tunneling microscopy measurement. The method makes possible the creation of micro- and nano-ordered graphene strips.
Synthesis and local electrical characterization of ZnO microwalls grown on cracked GaN/Si(111) by aqueous method
Authors: Yu Naisen , Wu Yunfeng , Du Lifang , Du Haiying , Mao Zhangwen , Hu Danyang , Wang Yong , Zhu Xueliang
Published: October 2012

ZnO microwalls have been grown on cracked GaN/Si(111) using aqueous method. The cracks of GaN direct ZnO grow and form two-dimensional microwall networks. Electrical characterization of individual upright standing ZnO microwall was performed by using conductive atomic force microscopy. Enhanced conductivity for the off-axis facet plane present on as-grown ZnO microwalls has been detected. Meanwhile, the local current-voltage characteristics shows that the sidewall has lower Schottky barrier height, it indicated that the off-axis sidewalls planes are more electrically active than c-plane ZnO. Furthermore, it will also provide a unique structure for surface-related applications, such as sensing, catalyzing, energy harvesting, etc.
Effective passivation of In0.2Ga0.8As by HfO2 surpassing Al2O3 via in-situ atomic layer deposition
Authors: Chang Y. H. , Lin C. A. , Liu Y. T. , Chiang T. H. , Lin H. Y. , Huang M. L. , Lin T. D. , Pi T. W. , Kwo J. , Hong M.
Published: October 2012

High κ gate dielectrics of HfO2 and Al2O3 were deposited on molecular beam epitaxy-grown In0.2Ga0.8As pristine surface using in-situ atomic-layer-deposition (ALD) without any surface treatment or passivation layer. The ALD-HfO2/p-In0.2Ga0.8As interface showed notable reduction in the interfacial density of states (Dit), deduced from quasi-static capacitance-voltage and conductance-voltage (G-V) at room temperature and 100 °C. More significantly, the midgap peak commonly observed in the Dit(E) of ALD-oxides/In0.2Ga0.8As is now greatly diminished. The midgap Dit value decreases from ≥15 × 1012 eV−1 cm−2 for ALD-Al2O3 to ∼2–4 × 1012 eV−1 cm−2 for ALD-HfO2. Further, thermal stability at 850 °C was achieved in the HfO2/In0.2Ga0.8As, whereas C-V characteristics of Al2O3/p-In0.2Ga0.8As degraded after the high temperature annealing. From in-situ x-ray photoelectron spectra, the AsOx, which is not the oxidized state from the native oxide, but is an induced state from adsorption of trimethylaluminum and H2O, was found at the ALD-Al2O3/In0.2Ga0.8As interface, while that was not detected at the ALD-HfO2/In0.2Ga0.8As interface.
Nanoparticle enhanced evaporation of liquids: A case study of silicone oil and water
Authors: Zhang Wenbin , Shen Rong , Lu Kunquan , Ji Ailing , Cao Zexian
Published: October 2012

Evaporation is a fundamental physical phenomenon, of which many challenging questions remain unanswered. Enhanced evaporation of liquids in some occasions is of enormous practical significance. Here we report the enhanced evaporation of the nearly permanently stable silicone oil by dispersing with nanopariticles including CaTiO3, anatase and rutile TiO2. An evaporation rate as high as 1.33 mg/h·cm2 was measured in silicone oil when dispersed with 100 nm-sized CaTiO3 particles. Dependence of evaporation rate on the chemistry, size and structure of the particles suggests that some weak absorption sites on the particles half floating on the liquid surface are responsible for the facilitated evaporation of liquid molecules. Enhanced evaporation is also observed for water when dispersed with anatase TiO2 particles. The results can inspire the research of atomistic mechanism for nanoparticle enhanced evaporation and exploration of evaporation control techniques for treatment of oil pollution and restoration of dirty water.
On the estimation of the magnetocaloric effect by means of microwave technique
Authors: Aleshkevych Pavlo
Published: October 2012

The method based on low-field microwave absorption measurements is presented to estimate the relative change of entropy with magnetic field. This method is illustrated on both the polycrystalline Gd5Si2Ge2 alloy and the single crystalline La0.7Ca0.3MnO3 manganite. It is shown that there is the simple functional relation between magnetization and non-resonant absorption over a narrow temperature range near the magnetic phase transition. The magnetoresistance is assumed to be the dominating mechanism underlying this relation.
Risk factors for nonsuicidal self‐injury in Japanese college students: The moderating role of mood regulation expectancies
Authors: Tresno Fiona , Ito Yoshimi , Mearns Jack
Published: October 2012

Self‐injurious behavior is increasing among college students, and is common in both psychiatric and nonclinical populations. People's engaging in self‐injury is associated with childhood maltreatment, poor negative mood regulation expectancies, and depression. During times of distress, maltreated children without healthy coping strategies tend to have impairment in mood regulation, which contributes to engaging in self‐injury. This study investigated differences between nonsuicidal self‐injury (NSSI) and non‐self‐injury groups in history of childhood maltreatment, negative mood regulation expectancies, and depression in a sample of Japanese college students. We also assessed risk factors for self‐injurious behavior, including mood regulation expectancies as a moderator of the relationship between childhood maltreatment and NSSI. Participants were 313 undergraduate students, who completed anonymous self‐report questionnaires—Deliberate Self‐Harm Inventory, Child Abuse and Trauma Scale, Negative Mood Regulation Scale, and short version of the Center for Epidemiological Studies–Depression Scale. Ten percent (n = 31) of all participants had injured themselves. Consistent with past literature, participants with self‐injury history reported more severe childhood maltreatment, poorer mood regulation expectancies, and more depression, compared to non‐self‐injurers. Frequency of NSSI positively correlated with childhood maltreatment and depression, and negatively correlated with negative mood regulation expectancies. Regression analysis revealed that stronger expectancies for negative mood regulation interacted with maltreatment to predict self‐injury: More maltreatment was associated with more self‐injury, particularly among those with weaker expectancies. Results suggested childhood maltreatment, low expectancies for negative mood regulation, and depression predicted self‐injury. Consistent with our moderation hypothesis, strong expectancies for negative mood regulation buffered the effects of childhood maltreatment, reducing the risk for self‐injury.
Simultaneous temperature and flux controllability for heat equations with memory
Authors: Avdonin S. , Pandolfi L.
Published: October 2012

It is known that, in the case of the heat equation with memory, temperature can be controlled to an arbitrary square integrable target provided that the system evolves for a sufficiently long time. The control is the temperature on the boundary. In this paper we consider heat equations with memory (one-dimensional space variable) and we first show that when the control is square integrable, then the flux is square integrable too. Then we prove that both temperature and flux can be simultaneously controlled to a pair of independent targets, both square integrable. This solves a problem first raised by Renardy.

The method of proof relies on moment theory, and one of the contributions of this paper is the identification ofL\mathcal {L}-bases and Riesz bases especially suited to heat equations with memory, which so appear to be endowed with a very rich bases structure.
Averaging of incompressible flows on two-dimensional surfaces
Authors: Dolgopyat Dmitry , Koralov Leonid
Published: October 2012

We consider a process on a compact two-dimensional surface which consists of the fast motion along the stream lines of an incompressible periodic vector field perturbed by white noise. It gives rise to a process on the graph naturally associated to the structure of the stream lines of the unperturbed flow. It has been shown by Freidlin and Wentzell that if the unperturbed motion is periodic for almost all the initial points, then the corresponding process on the graph weakly converges to a Markov process. We consider the situation when the unperturbed motion is not periodic and the flow has ergodic components of positive measure. We show that the process on the graph still converges to a Markov process, which spends a positive proportion of time in the vertices corresponding to the ergodic components of the flow.

As shown in a companion paper (Deterministic and stochastic perturbations of area preserving flows on a two-dimensional torus, by D. Dolgopyat, M. Freidlin, and L. Koralov), these results allow one to describe the viscosity regularization of dissipative deterministic perturbations of incompressible flows. In the case of surfaces of higher genus, the limiting process may exhibit intermittent behavior in the sense that the time axis can be divided into the intervals of random lengths where the particle stays inside one ergodic component separated by the intervals where the particle moves deterministically between the components.
Assessing the relationship between conservation of function and conservation of sequence using photosynthetic proteins
Authors: Ashkenazi Shaul , Snir Rotem , Ofran Yanay
Published: October 2012

Motivation: Assessing the false positive rate of function prediction methods is difficult, as it is hard to establish that a protein does not have a certain function. To determine to what extent proteins with similar sequences have a common function, we focused on photosynthesis-related proteins. A protein that comes from a non-photosynthetic organism is, undoubtedly, not involved in photosynthesis.

Results: We show that function diverges very rapidly: 70% of the close homologs of photosynthetic proteins come from non-photosynthetic organisms. Therefore, high sequence similarity, in most cases, is not tantamount to similar function. However, we found that many functionally similar proteins often share short sequence elements, which may correspond to a functional site and could reveal functional similarities more accurately than sequence similarity.

Conclusions: These results shed light on the way biological function is conserved in evolution and may help improve large-scale analysis of protein function.

Contact:  yanay@ofranlab.org

Supplementary information: Supplementary data are available at Bioinformatics online.
Development of colour-producing β-keratin nanostructures in avian feather barbs
Authors: Prum Richard O , Dufresne Eric R , Quinn Tim , Waters Karla
Published: October 2012

The non-iridescent structural colours of avian feather barbs are produced by coherent light scattering from amorphous (i.e. quasi-ordered) nanostructures of β-keratin and air in the medullary cells of feather barb rami. Known barb nanostructures belong to two distinct morphological classes. ‘Channel’ nanostructures consist of β-keratin bars and air channels of elongate, tortuous and twisting forms. ‘Spherical’ nanostructures consist of highly spherical air cavities that are surrounded by thin β-keratin bars and sometimes interconnected by tiny passages. Using transmission electron microscopy, we observe that the colour-producing channel-type nanostructures of medullary β-keratin in feathers of the blue-and-yellow macaw (Ara ararauna, Psittacidae) develop by intracellular self-assembly; the process proceeds in the absence of any biological prepattern created by the cell membrane, endoplasmic reticulum or cellular intermediate filaments. We examine the hypothesis that the shape and size of these self-assembled, intracellular nanostructures are determined by phase separation of β-keratin protein from the cytoplasm of the cell. The shapes of a broad sample of colour-producing channel-type nanostructures from nine avian species are very similar to those self-assembled during the phase separation of an unstable mixture, a process called spinodal decomposition (SD). In contrast, the shapes of a sample of spherical-type nanostructures from feather barbs of six species show a poor match to SD. However, spherical nanostructures show a strong morphological similarity to morphologies produced by phase separation of a metastable mixture, called nucleation and growth. We propose that colour-producing, intracellular, spongy medullary β-keratin nanostructures develop their characteristic sizes and shapes by phase separation during protein polymerization. We discuss the possible role of capillary flow through drying of medullary cells in the development of the hollow morphology of typical and spongy feather medullary cells.
Iridescence: views from many angles
Authors: Meadows Melissa G , Butler Michael W , Morehouse Nathan I , Taylor Lisa A , Toomey Matthew B , McGraw Kevin J , Rutowski Ronald L
Published: October 2012

Iridescent colours have been fascinating to humans throughout history; they are flashy, shimmering, dynamic, and examples surround us, from the commonly seen iridescent sheen of oily street puddles to the exotic, gaudy displays of birds-of-paradise featured in nature documentaries. Iridescent colours and the structures that produce them have unique properties in comparison with other types of colourants found in nature. Scientists from a variety of disciplines study the optics, development, heritability, chemical make-up, origin, evolution, functions and biomimetic technological applications of naturally occurring iridescent colours. For the first time, graduate students at Arizona State University brought together these scientists, along with educators and artists, at ‘Iridescence: more than meets the eye’, a conference to promote interdisciplinary communication and collaboration in the study of iridescent coloration from all of these perspectives. Here, we summarize the outcomes of this conference, introduce the papers that follow in this special journal issue and briefly review the current status of our understanding of iridescence.
Stabilizing entangled states with quasi-local quantum dynamical semigroups
Authors: Ticozzi Francesco , Viola Lorenza
Published: October 2012

We provide a solution to the problem of determining whether a target pure state can be asymptotically prepared using dissipative Markovian dynamics under
fixed
locality constraints. Besides recovering existing results for a large class of physically relevant entangled states, our approach has the advantage of providing an explicit stabilization test solely based on the input state and constraints of the problem. Connections with the formalism of frustration-free parent Hamiltonians are discussed, as well as control implementations in terms of a switching output-feedback law.