bluuebunny/crossref_metadata_2025 huggingface dataset:
הערות על דרכי השימוש של ר' נפתלי בכרך במקורות טרום-לוריאנים
Authors: באומגרטן אליעזר
Published: December 2013

ומי יתן והיה לבב אנשי גדולי הדור שיש בידם למחות לגעור בם, עד שיאמרו הנוסח שהוא ישן נושן בדפוס, ולא חדשים מקרוב באו, לא שערום אבותיכם. ובודאי מי שהוא מוחה וגוער בם ראוי לו לבא במחיצת הקלירי ורבי שמעון הגדול זלה"ה, ועם אותם שיסדו התפלות דהיינו אנשי כנסת הגדולה. 'וגם הקולות יחדלון', ויקחו להם כוונה נכונה בסודי התפילות כמו שראוי להיות
Influence of Negative Stereotypes and Beliefs on Neuropsychological Test Performance in a Traumatic Brain Injury Population
Authors: Kit Karen A. , Mateer Catherine A. , Tuokko Holly A. , Spencer-Rodgers Julie
Published: December 2013

The impact of stereotype threat and self-efficacy beliefs on neuropsychological test performance in a clinical traumatic brain injury (TBI) population was investigated. A total of 42 individuals with mild-to-moderate TBI and 42 (age-, gender-, educationally matched) healthy adults were recruited. The study consisted of a 2 (Type of injury: control, TBI) × 2 (Threat Condition: reduced threat, heightened threat) between-participants design. The purpose of the reduced threat condition was to reduce negative stereotyped beliefs regarding cognitive effects of TBI and to emphasize personal control over cognition. The heightened threat condition consisted of an opposing view. Main effects included greater anxiety, motivation, and dejection but reduced memory self-efficacy for head-injured-groups, compared to control groups. On neuropsychological testing, the TBI-heightened-threat-group displayed lower scores onInitial Encoding(initial recall) and trended toward displaying lower scores onAttention(working memory) compared to the TBI-reduced-threat-group. No effect was found for Delayed Recall measures. Memory self-efficacy mediated the relation between threat condition and neuropsychological performance, indicating a potential mechanism for the threat effect. The findings highlight the impact of stereotype threat and self-referent beliefs on neuropsychological test performance in a clinical TBI population. (JINS, 2013,20, 1–11)
Microbial population and functional dynamics associated with surface potential and carbon metabolism
Authors: Ishii Shun’ichi , Suzuki Shino , Norden-Krichmar Trina M , Phan Tony , Wanger Greg , Nealson Kenneth H , Sekiguchi Yuji , Gorby Yuri A , Bretschger Orianna
Published: December 2013

Microbial extracellular electron transfer (EET) to solid surfaces is an important reaction for metal reduction occurring in various anoxic environments. However, it is challenging to accurately characterize EET-active microbial communities and each member’s contribution to EET reactions because of changes in composition and concentrations of electron donors and solid-phase acceptors. Here, we used bioelectrochemical systems to systematically evaluate the synergistic effects of carbon source and surface redox potential on EET-active microbial community development, metabolic networks and overall electron transfer rates. The results indicate that faster biocatalytic rates were observed under electropositive electrode surface potential conditions, and under fatty acid-fed conditions. Temporal 16S rRNA-based microbial community analyses showed that Geobacter phylotypes were highly diverse and apparently dependent on surface potentials. The well-known electrogenic microbes affiliated with the Geobacter metallireducens clade were associated with lower surface potentials and less current generation, whereas Geobacter subsurface clades 1 and 2 were associated with higher surface potentials and greater current generation. An association was also observed between specific fermentative phylotypes and Geobacter phylotypes at specific surface potentials. When sugars were present, Tolumonas and Aeromonas phylotypes were preferentially associated with lower surface potentials, whereas Lactococcus phylotypes were found to be closely associated with Geobacter subsurface clades 1 and 2 phylotypes under higher surface potential conditions. Collectively, these results suggest that surface potentials provide a strong selective pressure, at the species and strain level, for both solid surface respirators and fermentative microbes throughout the EET-active community development.
Tunable single-photon frequency conversion in a Sagnac interferometer
Authors: Yan Wei-Bin , Huang Jin-Feng , Fan Heng
Published: December 2013

Quantum information carriers like photons might be manipulated, stored and transmitted in different quantum systems. It is important to integrate those systems efficiently. The capability of converting photons from one wavelength to another wavelength is a key requirement for combining the photons in telecommunications band for quantum transmission and the photons in near-visible band for quantum storage. Here, we investigate the tunable single-photon frequency conversion in the five-level emitter-Sagnac interferometer system. We show that the efficient single-photon conversion can be achieved in this scheme, at the same time, the frequencies of the input and output photons can be tuned in a large scale by controlling the frequencies and Rabi frequencies of the external driving fields. The realization of this scheme may lead to the efficient combination of quantum storage system with the quantum communication system.
Kinetic Monte Carlo simulations of heterogeneously catalyzed oxidation reactions
Authors: Hess Franziska , Over Herbert
Published: December 2013

In this perspective, we focus on the catalyzed oxidation of CO and HCl over the model catalyst RuO2(110) and how the kinetics of these reactions can only properly be modeled by kinetic Monte Carlo (kMC) simulations when lateral interactions of the surface species are taken into account.
Homogeneous catalytic reduction of CO2 with hydrosilanes
Authors: Fernández-Alvarez Francisco J. , Aitani Abdullah M. , Oro Luis A.
Published: December 2013

Catalytic CO2 hydrosilylation is a chemical process that could be potentially applied to large-scale transformations.
[IrCl{N(CHCHPtBu2)2}]−: a versatile source of the IrI(PNP) pincer platform
Authors: Kinauer Markus , Scheibel Markus G. , Abbenseth Josh , Heinemann Frank W. , Stollberg Peter , Würtele Christian , Schneider Sven
Published: December 2013

The iridium(ii) complex [IrCl{N(CHCHPtBu2)2}] is reduced by KC8 to give the anionic iridium(i) pincer complex [IrCl{N(CHCHPtBu2)2}]− which was isolated and fully characterized upon stabilization of the counter cation with crown ether as [K(15-cr-5)2][IrCl{N(CHCHPtBu2)2}].
Branched polyethylene mimicry by metathesis copolymerization of fatty acid-based α,ω-dienes
Authors: Lebarbé Thomas , Neqal Mehdi , Grau Etienne , Alfos Carine , Cramail Henri
Published: December 2013

Fully bio-based linear branched polyethylene mimics bearing ester functions were synthesized by metathesis copolymerization of linear and branched α,ω-dienes obtained from fatty acid derivatives.
High-performance n-Si/α-Fe2O3 core/shell nanowire array photoanode towards photoelectrochemical water splitting
Authors: Qi Xiaopeng , She Guangwei , Huang Xing , Zhang Taiping , Wang Huimin , Mu Lixuan , Shi Wensheng
Published: December 2013

We report n-Si/α-Fe2O3 core/shell nanowire array photoanodes exhibiting excellent performance for photoelectrochemical water splitting. The material size-related charge transfer processes and band position changes in the composite photoelectrodes were investigated.
A metal-catalyst free, flexible and free-standing chitosan/vacuum-stripped graphene/polypyrrole three dimensional electrode interface for high performance dopamine sensing
Authors: Liu Jing , He Ziming , Xue Jingwen , Yang Tan Timothy Thatt
Published: December 2013

A free-standing chitosan/vacuum stripped graphene/polypyrrole scaffold with a hierarchical porous structure was demonstrated as a high performance dopamine sensing electrode.
Fragmented polymer nanotubes from sonication-induced scission with a thermo-responsive gating system for anti-cancer drug delivery
Authors: Chen Guofang , Chen Ruoyao , Zou Chunxiao , Yang Danwen , Chen Zhe-Sheng
Published: December 2013

Fragmented polymer nanotubes with a thermo-responsive gating system were prepared by a 2-fold “grafting-from” strategy and sonication-induced scission for efficient drug delivery. In vitro thermo-responsive DOX drug release and chemotoxicity were testified with such nanocarriers.
Novel evidence for the specific interaction between cholesterol and α-haemolysin of Escherichia coli
Authors: Vazquez Romina F. , Maté Sabina M. , Bakás Laura S. , Fernández Marisa M. , Malchiodi Emilio L. , Herlax Vanesa S.
Published: December 2013

Several toxins that act on animal cells present different, but specific, interactions with cholesterol or sphingomyelin. In the present study we demonstrate that HlyA (α-haemolysin) of Escherichia coli interacts directly with cholesterol. We have recently reported that HlyA became associated with detergent-resistant membranes enriched in cholesterol and sphingomyelin; moreover, toxin oligomerization, and hence haemolytic activity, diminishes in cholesterol-depleted erythrocytes. Considering these results, we studied the insertion process, an essential step in the lytic mechanism, by the monolayer technique, finding that HlyA insertion is favoured in cholesterol- and sphingomyelin-containing membranes. On the basis of this result, we studied the direct interaction with either of the lipids by lipid dot blotting, lysis inhibition and SPR (surface plasmon resonance) assays. The results of the present study demonstrated that an interaction between cholesterol and HlyA exists that seems to favour a conformational state of the protein that allows its correct insertion into the membrane and its further oligomerization to form pores.
Directional lane‐allocation concerning demand uncertainty
Authors: Zhang Lihui , Zhong Shaopeng
Published: December 2013

Regarding the one‐way restriction as a special case of the lane‐allocation operation, this study formulates the general lane‐allocation problem as a mathematical program with complementarity constraints (MPCC). Recognising the day‐to‐day and within‐day travel demand variations, another counterpart of the MPCC is formulated to obtain a robust lane‐allocation scheme that performs better against a set of worst‐case demand scenarios. Solution algorithms based on active sets are proposed to address the problems by sequentially solving some relaxed‐MPCC and a binary knapsack problem. Numerical examples are presented to validate the proposed model and algorithm.
Identifying factors affecting drivers’ selection of unconventional outside left‐turn lanes at signallised intersections
Authors: Liu Pan , Xu Chengcheng , Wang Wei , Wan Jingjing
Published: December 2013

An unconventional outside left‐turn lane design has been increasingly used at signallised intersections in the urban areas in China. The unconventional outside left‐turn lane design allows an exclusive left‐turn lane to be located to the right of through lanes. The study presented in this paper evaluated the factors that affected drivers’ selection of left‐turn lanes at signallised intersections where both inside and outside left‐turn lanes were provided. A binary logit model was developed to quantitatively evaluate the impact of contributing factors on drivers’ selection of outside left‐turn lanes. It was found that the chance of a driver choosing the outside left‐turn lane would increase with an increase in the traffic volume on the major street and the queue length in the inside left‐turn lane; and would decrease with an increase in the distance between the upstream side street to the signallised intersection. In addition, drivers of heavy vehicles and those from the upstream right‐side side streets were more likely to select outside left‐turn lanes. Based on the data analysis results, a procedure was proposed to help transportation professionals determine if outside left‐turn lanes were needed given traffic conditions and geometric characteristics of a signallised intersection.
Real‐time freeway sideswipe crash prediction by support vector machine
Authors: Qu Xu , Wang Wei , Wang Wenfu , Liu Pan
Published: December 2013

This study presents the applications of a pattern classifier named support vector machine (SVM) in predicting freeway sideswipe crash potential. Historical loop detector data for sideswipe crashes and corresponding non‐crash cases were collected from Interstate‐894 in the Milwaukee, Wisconsin, USA. Two sets of significant explanatory features were aggregated from the collected detector data to capture the prevailing traffic state and variances between adjacent lanes. Then, three SVMs with different nonlinear kernel function were formulated with the significant features as inputs. To comparatively evaluate the performance of SVM models against other commonly applied crash potential predictors, the multi‐layer perceptron (MLP) artificial neural network models were also developed to predict sideswipe crash potential. The results showed that SVM models offers similar overall accuracy as the premier MLP model, but SVMs achieved better sideswipe crash identification at higher false alarm rates. The research also investigated the potential of using the SVM model for evaluating the impacts of traffic factors on sideswipe crash. Sensitivity analysis conducted on the trained SVM models successfully identified the variables’ impact on sideswipe crash. These results affirmed the superior performance of SVM technique in crash potential prediction analysis.
Dynamic speed guidance for active highway signal coordination: roadside against in‐car strategies
Authors: Sun Jian , Chen Shenyang
Published: December 2013

The effectiveness of signal coordination can be undermined by over‐long spacing and different vehicle dynamic characteristics between neighbouring signal intersections in a signalised highway system. This study presents two dynamic speed guidance (DSG) strategies based on the traffic environment and facility deployment to congregate the traffic flow and optimise the arterial coordinated signal control system. One of them is the in‐car display for individual guidance, and the other is the roadside display for group guidance. The two DSG strategies are calculated using the rolling horizon approach. A simulation platform that integrates data communication, traffic mobility and DSG application is programmed based on VISSIM, a microscopic simulation model. A section of Cao'an highway is used to assess the efficiency of two DSG strategies. The assessment results show that both the average stops and travel time of arterial vehicles can be optimised with the application of the two DSG strategies. In addition, the in‐car strategy provides a significant benefit for on‐board unit equipped vehicles, even in a low level of market penetration rate.
Printed monopole antenna with tapered feed line, feed region and patch for super wideband applications
Authors: Manohar Murli , Kshetrimayum Rakhesh Singh , Gogoi Anup Kumar
Published: December 2013

A novel and compact super wideband (SWB) exponentially tapered feed region and patch printed monopole antenna is proposed. This antenna is fed by a 50‐Ω triangular tapered feed line. The antenna operates over a bandwidth of 2.5–80 GHz with a return loss of 10 dB or more. The dimensions of the proposed antenna are 40 × 30 × 1.6 mm3. An exponential curve is employed in the feed region and a triangular tapered feed line is used. The ground plane feed gap is optimised to 1.3 mm. The proposed tapered monopole antenna has demonstrated an ultra‐large bandwidth with satisfactory radiation properties. Two particular antennas are examined, one with a rectangular feed line and another with a triangular tapered feed line. The performance of the antenna in frequency domain is investigated, and a good agreement is achieved between the simulation and experimental results. In addition, the time domain characteristics of the proposed antenna are evaluated experimentally. This antenna can be used in ultra‐wideband or SWB applications.
Efficient unconditionally stable one‐step leapfrog ADI‐FDTD method with low numerical dispersion
Authors: Kong Yong‐Dan , Chu Qing‐Xin , Li RongLin
Published: December 2013

An efficient unconditionally stable one‐step leapfrog alternating‐direction‐implicit finite‐difference time‐domain (ADI‐FDTD) method based on the controlling parameters is presented. First, three controlling parameters are introduced to the matrices of the Maxwell's equations to decrease the numerical dispersion error, and then the formulation of an efficient one‐step leapfrog ADI‐FDTD method is derived. Second, the analysis shows that the proposed method is unconditionally stable. Moreover, the numerical dispersion relation of the proposed method is derived analytically. Third, the process of determination of the controlling parameters is shown. Furthermore, the effects of the propagation angle, mesh size, time step and frequency on the dispersion characteristics of the proposed method are also investigated. The result shows that the normalised numerical phase velocity error (NNPVE) and maximum NNPVE of the proposed method are decreased significantly. Finally, two numerical examples are simulated to demonstrate the accuracy and efficiency of the proposed method.
Fabrication and optical properties of zirconia nanoparticle array on a patterned hydrophilic-hydrophobic substrate
Authors: Yang Mi-Sun , Son Seong-Jin , Park ByeongChan , Kee Moon Byung , Jang Jae-Won
Published: December 2013

This study presents a convenient method for nanoparticles (NPs) patterning with high controllability of the number of NPs. Dot-array of zirconia (ZrO2) NPs were fabricated on a microcontact printed hydrophilic-hydrophobic substrate without any post-functionalization on ZrO2 NPs. Because the substrate has hydrophilic patterns with hydrophobic passivation, ZrO2 colloids in de-ionized water were selectively deposited on the substrate; thus, an “electrostatic approach” by functionalization of ZrO2 NPs is not required. In addition, the number of patterned NPs was controllable by size of hydrophilic area, deposition time, and concentration of colloidal NPs. The number of NPs increases over ten times as the size of polydimethylsiloxane (PDMS) dot stamp increase from 5 to 10 μm in diameter, while it increases twice and four times by increasing deposition time (1 to 60 min) and concentration of NPs colloidal solution (16 to 57 mM), respectively. Moreover, ellipsometric reflectance of the dot-arrays of ZrO2 NPs patterned with different concentrations of NP solutions was measured and discussed in comparison with the absorbance spectrum of a powder sample of ZrO2 NPs.
Creating a single twin boundary between two CdTe (111) wafers with controlled rotation angle by wafer bonding
Authors: Sun Ce , Lu Ning , Wang Jinguo , Lee Jihyung , Peng Xin , Klie Robert F. , Kim Moon J.
Published: December 2013

The single twin boundary with crystallographic orientation relationship (1¯1¯1¯)//(111) [01¯1]//[011¯] was created by wafer bonding. Electron diffraction patterns and high-resolution transmission electron microscopy images demonstrated the well control of the rotation angle between the bonded pair. At the twin boundary, one unit of wurtzite structure was found between two zinc-blende matrices. High-angle annular dark-field scanning transmission electron microscopy images showed Cd- and Te-terminated for the two bonded portions, respectively. The I-V curve across the twin boundary showed increasingly nonlinear behavior, indicating a potential barrier at the bonded twin boundary.
Q-factor of (In,Ga)N containing III-nitride microcavity grown by multiple deposition techniques
Authors: Gačević Ž. , Rossbach G. , Butté R. , Réveret F. , Glauser M. , Levrat J. , Cosendey G. , Carlin J.-F. , Grandjean N. , Calleja E.
Published: December 2013

A 3λ/2 (In,Ga)N/GaN resonant cavity, designed for ∼415 nm operation, is grown by molecular beam epitaxy and is sandwiched between a 39.5-period (In,Al)N/GaN distributed Bragg reflector (DBR), grown on c-plane GaN-on-sapphire pseudo-substrate by metal-organic vapor phase epitaxy and an 8-period SiO2/ZrO2 DBR, deposited by electron beam evaporation. Optical characterization reveals an improvement in the cavity emission spectral purity of approximately one order of magnitude due to resonance effects. The combination of spectrophotometric and micro-reflectivity measurements confirms the strong quality (Q)-factor dependence on the excitation spot size. We derive simple analytical formulas to estimate leak and residual absorption losses and propose a simple approach to model the Q-factor and to give a quantitative estimation of the weight of cavity disorder. The model is in good agreement with both transfer-matrix simulation and the experimental findings. We point out that the realization of high Q-factor (In,Ga)N containing microcavities on GaN pseudo-substrates is likely to be limited by the cavity disorder.
Origin of long-lived oscillations in 2D-spectra of a quantum vibronic model: Electronic versus vibrational coherence
Authors: Plenio M. B. , Almeida J. , Huelga S. F.
Published: December 2013

We demonstrate that the coupling of excitonic and vibrational motion in biological complexes can provide mechanisms to explain the long-lived oscillations that have been obtained in nonlinear spectroscopic signals of different photosynthetic pigment protein complexes and we discuss the contributions of excitonic versus purely vibrational components to these oscillatory features. Considering a dimer model coupled to a structured spectral density we exemplify the fundamental aspects of the electron-phonon dynamics, and by analyzing separately the different contributions to the nonlinear signal, we show that for realistic parameter regimes purely electronic coherence is of the same order as purely vibrational coherence in the electronic ground state. Moreover, we demonstrate how the latter relies upon the excitonic interaction to manifest. These results link recently proposed microscopic, non-equilibrium mechanisms to support long lived coherence at ambient temperatures with actual experimental observations of oscillatory behaviour using 2D photon echo techniques to corroborate the fundamental importance of the interplay of electronic and vibrational degrees of freedom in the dynamics of light harvesting aggregates.
Automated fit of high-dimensional potential energy surfaces using cluster analysis and interpolation over descriptors of chemical environment
Authors: Fournier René , Orel Slava
Published: December 2013

We present a method for fitting high-dimensional potential energy surfaces that is almost fully automated, can be applied to systems with various chemical compositions, and involves no particular choice of function form. We tested it on four systems: Ag20, Sn6Pb6, Si10, and Li8. The cost for energy evaluation is smaller than the cost of a density functional theory (DFT) energy evaluation by a factor of 1500 for Li8, and 60 000 for Ag20. We achieved intermediate accuracy (errors of 0.4 to 0.8 eV on atomization energies, or, 1% to 3% on cohesive energies) with rather small datasets (between 240 and 1400 configurations). We demonstrate that this accuracy is sufficient to correctly screen the configurations with lowest DFT energy, making this function potentially very useful in a hybrid global optimization strategy. We show that, as expected, the accuracy of the function improves with an increase in the size of the fitting dataset.
Freak waves in weakly nonlinear unidirectional wave trains over a sloping bottom in shallow water
Authors: Gramstad O. , Zeng H. , Trulsen K. , Pedersen G. K.
Published: December 2013

Using a Boussinesq model with improved linear dispersion, we show numerical evidence that bottom non-uniformity can provoke significantly increased probability of freak waves as a wave field propagates into shallower water, in agreement with recent experimental results [K. Trulsen, H. Zeng, and O. Gramstad, “Laboratory evidence of freak waves provoked by non-uniform bathymetry,” Phys. Fluids 24, 097101 (2012)]. Increased values of skewness, kurtosis, and probability of freak waves can be found on the shallower side of a bottom slope, with a maximum close to the end of the slope. The increased probability of freak waves is typically seen to endure some distance into the shallower domain, before it decreases and reaches a stable value depending on the depth. The maxima of the statistical parameters are observed both in the case where there is a region of constant depth after the slope, and in the case where the uphill slope is immediately followed by a downhill slope. In the case that waves propagate over a slope from shallower to deeper water, however, we do not find any increase in freak wave occurrence.
Optical transmission modules for multi-channel superconducting quantum interference device readouts
Authors: Kim Jin-Mok , Kwon Hyukchan , Yu Kwon-kyu , Lee Yong-Ho , Kim Kiwoong
Published: December 2013

We developed an optical transmission module consisting of 16-channel analog-to-digital converter (ADC), digital-noise filter, and one-line serial transmitter, which transferred Superconducting Quantum Interference Device (SQUID) readout data to a computer by a single optical cable. A 16-channel ADC sent out SQUID readouts data with 32-bit serial data of 8-bit channel and 24-bit voltage data at a sample rate of 1.5 kSample/s. A digital-noise filter suppressed digital noises generated by digital clocks to obtain SQUID modulation as large as possible. One-line serial transmitter reformed 32-bit serial data to the modulated data that contained data and clock, and sent them through a single optical cable. When the optical transmission modules were applied to 152-channel SQUID magnetoencephalography system, this system maintained a field noise level of 3 fT/√Hz @ 100 Hz.
Development of radon sources with a high stability and a wide range
Authors: Fukutsu K. , Yamada Y.
Published: December 2013

A solid 222Rn (radon) source using a fibrous and porous SiC ceramic disk was developed. The emission rate of radon emanated from the disk depended on the content of 226Ra and the sintering temperature. A 226Ra sulfate (226RaSO4) solution was dropped on a fibrous SiC ceramic disk (33 mmϕ) of 1 mm in thickness, and sintered at 400 °C. The radon concentration from a disk containing 226Ra of 1.85 MBq was measured to be 38 kBq  m−3 at a carrier airflow rate of 0.5 L min−1. By adjusting the 226Ra content or the sweep airflow rate, the radon concentrations were easily controlled over a wide range of over three orders of magnitude. The concentration was very stable for a long term. The compactness of the source disk made is easy for handling the source container and the shielding of gamma radiation from 226Ra and its decay products. Such advantages in a radon generation system are desirable for experiments of high-level, large-scale radon exposure.
Design of a new electron cyclotron resonance ion source at Oshima National College of Maritime Technology
Authors: Asaji T. , Hirabara N. , Izumihara T. , Hitobo T. , Nakamizu T. , Ohba T. , Nakamura T. , Furuse M. , Kato Y.
Published: December 2013

A new electron cyclotron resonance ion/plasma source has been designed and will be built at Oshima National College of Maritime Technology by early 2014. We have developed an ion source that allows the control of the plasma parameters over a wide range of electron temperatures for material research. A minimum-B magnetic field composed of axial mirror fields and radial cusp fields was designed using mainly Nd-Fe-B permanent magnets. The axial magnetic field can be varied by three solenoid coils. The apparatus has 2.45 GHz magnetron and 2.5–6.0 GHz solid-state microwave sources.
Study on a negative hydrogen ion source with hot cathode arc discharge
Authors: Lin S. H. , Fang X. , Zhang H. J. , Qian C. , Ma B. H. , Wang H. , Li X. X. , Zhang X. Z. , Sun L. T. , Zhang Z. M. , Yuan P. , Zhao H. W.
Published: December 2013

A negative hydrogen (H−) ion source with hot cathode arc discharge was designed and fabricated as a primary injector for a 10 MeV PET cyclotron at IMP. 1 mA dc H− beam with ɛ N, RMS = 0.08 π mm mrad was extracted at 25 kV. Halbach hexapole was adopted to confine the plasma. The state of arc discharge, the parameters including filament current, arc current, gas pressure, plasma electrode bias, and the ratio of ${\rm I}_{{\rm e}^ - } /{\rm I}_{{\rm H}^ - }$Ie−/IH− were experimentally studied. The discussion on the result, and opinions to improve the source were given.
Thickness dependent functional properties of PbZr0.52Ti0.48O3/La0.67Sr0.33MnO3 heterostructures
Authors: Barrionuevo D. , Ortega N. , Kumar A. , Chatterjee R. , Scott J. F. , Katiyar R. S.
Published: December 2013

The ultra thin ferroelectric PbZr0.52Ti0.48O3 (PZT) films with various thicknesses ranging from 100 (P100) to 10 (P10) nm were grown on La0.67Sr0.33MnO3/(LaAlO3)0.3(Sr2AlTaO6)0.7 (LSMO/LSAT) (001) substrates deposited by pulsed laser deposition technique. The x-ray diffraction patterns of the heterostructures show only (00l) (l = 1 and/or 2) reflections corresponding to the LSAT substrate, PZT, and LSMO layers. The atomic force microscopy studies show that the root mean square surface roughnesses of P100 and P10 films are 2.39 and 0.99 nm, respectively. An increase of both real (ε′) and imaginary (ε″) permittivities was observed when thickness of PZT increases from 10 nm to 100 nm. Temperature dependent ε′ presents an anomaly, related to ferromagnetic-metal to paramagnetic-insulator transition of the LSMO, in the range of 350–500 K. The dielectric anomalies and magnetic phase transition temperature shifted to the lower temperature values with decrease in the PZT films thicknesses. The values of the remanent polarization (Pr) and coercive field (Ec) of the heterostructures were in the range of 24–42 μC/cm2–170–1300 kV/cm. An appreciable increase of saturated magnetization (Ms) was observed with increase of PZT layer thickness. The average Ms values of PZT/LSMO heterostructure were 170, 150, 100, and 45 emu/cm3 for 100, 50, 25, and 10 nm at 300 K, respectively. Enhancement in magnetization with increase in PZT thickness may be due to the interface effect between PZT/LSMO layers.
Analytical approximations for spiral waves
Authors: Löber Jakob , Engel Harald
Published: December 2013

We propose a non-perturbative attempt to solve the kinematic equations for spiral waves in excitable media. From the eikonal equation for the wave front we derive an implicit analytical relation between rotation frequency Ω and core radius R0. For free, rigidly rotating spiral waves our analytical prediction is in good agreement with numerical solutions of the linear eikonal equation not only for very large but also for intermediate and small values of the core radius. An equivalent Ω(R+) dependence improves the result by Keener and Tyson for spiral waves pinned to a circular defect of radius R+ with Neumann boundaries at the periphery. Simultaneously, analytical approximations for the shape of free and pinned spirals are given. We discuss the reasons why the ansatz fails to correctly describe the dependence of the rotation frequency on the excitability of the medium.
Active patterning and asymmetric transport in a model actomyosin network
Authors: Wang Shenshen , Wolynes Peter G.
Published: December 2013

Cytoskeletal networks, which are essentially motor-filament assemblies, play a major role in many developmental processes involving structural remodeling and shape changes. These are achieved by nonequilibrium self-organization processes that generate functional patterns and drive intracellular transport. We construct a minimal physical model that incorporates the coupling between nonlinear elastic responses of individual filaments and force-dependent motor action. By performing stochastic simulations we show that the interplay of motor processes, described as driving anti-correlated motion of the network vertices, and the network connectivity, which determines the percolation character of the structure, can indeed capture the dynamical and structural cooperativity which gives rise to diverse patterns observed experimentally. The buckling instability of individual filaments is found to play a key role in localizing collapse events due to local force imbalance. Motor-driven buckling-induced node aggregation provides a dynamic mechanism that stabilizes the two-dimensional patterns below the apparent static percolation limit. Coordinated motor action is also shown to suppress random thermal noise on large time scales, the two-dimensional configuration that the system starts with thus remaining planar during the structural development. By carrying out similar simulations on a three-dimensional anchored network, we find that the myosin-driven isotropic contraction of a well-connected actin network, when combined with mechanical anchoring that confers directionality to the collective motion, may represent a novel mechanism of intracellular transport, as revealed by chromosome translocation in the starfish oocyte.
Hydration layer structures on calcite facets and their roles in selective adsorptions of biomolecules: A molecular dynamics study
Authors: Zhu Beibei , Xu Xurong , Tang Ruikang
Published: December 2013

The selective adsorptions of biomolecules onto crystal faces are the key issues in the studies of biomineralization. Frequently, the adsorption processes are understood by using the direct binding model between organic compounds and inorganic crystals during the molecular dynamic studies. However, water molecules near crystals always exhibit intense ordering and preferential orientation to form structured hydration layer. By using the adsorption of poly acrylic acid oligomer, acrylic acid (AA) dimer, onto calcite as an example, we demonstrate that the induced hydration layers contribute significant effects on the organic-inorganic interactions. In particular, on calcite (104) plane, two carboxyl groups of AA dimer both interact with the crystal but the molecule has to compete with water due to the well-structured hydration layer. On (110) plane, although only one carboxyl group of AA dimer interacts with this surface, the water layer is relatively loose so that the molecule can easily replace water. With a consideration of the hydration layer, our free energy analysis indicates that AA dimer has a stronger interaction with (110) face than with (104) face, which is consistent with the experimental observations. The study follows that the attachment of organic additive onto inorganic crystal facet is greatly mediated by near-surface hydration layers, and therefore, the critical role of structured water layers must be taken into account in the understanding of biomineralization interfaces.
Effects of electron recirculation on a hard x-ray source observed during the interaction of a high intensity laser pulse with thin Au targets
Authors: Compant La Fontaine A. , Courtois C. , Lefebvre E. , Bourgade J. L. , Landoas O. , Thorp K. , Stoeckl C.
Published: December 2013

The interaction of a high intensity laser pulse on the preplasma of a high-Z solid target produced by the pulse's pedestal generates high-energy electrons. These electrons subsequently penetrate inside the solid target and produce bremsstrahlung photons, generating an x-ray source which can be used for photonuclear studies or to radiograph high area density objects. The source characteristics are compared for targets with thin (20 μm) and thick (100 μm) Au foils on the Omega EP laser at Laboratory for Laser Energetics. Simulations using the particle-in-cell code CALDER show that for a 20 μm thickness Au target, electrons perform multiple round-trips in the target under the effect of the laser ponderomotive potential and the target electrostatic potential. These relativistic electrons have random transverse displacements, with respect to the target normal, attributed to electrostatic fluctuation fields. As a result, the x-ray spot size is increased by a factor 2 for thin target compared to thick targets, in agreement with experimental results. In addition, the computed doses agree with the measured ones provided that electron recirculation in the thin target is taken into account. A dose increase by a factor 1.7 is then computed by allowing for recirculation. In the 100 μm target case, on the other hand, this effect is found to be negligible.
Langmuir probe measurements in a time-fluctuating-highly ionized non-equilibrium cutting arc: Analysis of the electron retarding part of the time-averaged current-voltage characteristic of the probe
Authors: Prevosto L. , Kelly H. , Mancinelli B.
Published: December 2013

This work describes the application of Langmuir probe diagnostics to the measurement of the electron temperature in a time-fluctuating-highly ionized, non-equilibrium cutting arc. The electron retarding part of the time-averaged current-voltage characteristic of the probe was analysed, assuming that the standard exponential expression describing the electron current to the probe in collision-free plasmas can be applied under the investigated conditions. A procedure is described which allows the determination of the errors introduced in time-averaged probe data due to small-amplitude plasma fluctuations. It was found that the experimental points can be gathered into two well defined groups allowing defining two quite different averaged electron temperature values. In the low-current region the averaged characteristic was not significantly disturbed by the fluctuations and can reliably be used to obtain the actual value of the averaged electron temperature. In particular, an averaged electron temperature of 0.98 ± 0.07 eV (= 11400 ± 800 K) was found for the central core of the arc (30 A) at 3.5 mm downstream from the nozzle exit. This average included not only a time-average over the time fluctuations but also a spatial-average along the probe collecting length. The fitting of the high-current region of the characteristic using such electron temperature value together with the corrections given by the fluctuation analysis showed a relevant departure of local thermal equilibrium in the arc core.
Low dipolar interactions in dense aggregates of aligned magnetic nanowires
Authors: Panagiotopoulos I. , Fang W. , Aït-Atmane K. , Piquemal J.-Y. , Viau G. , Dalmas F. , Boué F. , Ott F.
Published: December 2013

Magnetic interactions in aggregates of polyol-synthesized cobalt nanowires are studied by δM plots. Negative δM values are obtained as expected for magnetostatic coupling between physically isolated nanowires, without exchange interactions. Very weak interactions (down to δM = −0.05) are achieved by alignment and dispersion into polymeric matrices. We attribute this to the fact that during the fabrication of the composite materials, the nanowires reorganize so as to minimize the dipolar interactions. Since the δM-plots are sensitive to the nature of the demagnetized state, it is shown by micromagnetic simulations that the ac demagnetized state provides the best choice of a starting point since it ensures that macroscopic configurations consisting of single domain states of each wire are compared. The low interactions observed in these materials suggest that these composite materials are candidates for rare-earth free permanent magnets since demagnetization phenomena are minimized.
Hydrodynamic motion of a large prestressed concrete bucket foundation for offshore wind turbines
Authors: Zhang Puyang , Ding Hongyan , Le Conghuan
Published: December 2013

A large prestressed concrete bucket foundation (LPCBF) was used for the first offshore wind turbine in the Qidong sea area of Jiangsu Province in China. The most critical technique of the foundation is the self-floating towing technique based on a reasonable subdivision inside the bucket. To predict the dynamic behaviors of the LPCBF in waves supported by the air cushion, the hydrodynamic software MOSES is used to simulate the three-dimensional motion of the foundation in the towing construction site. The prototype foundation models are established using MOSES with a water draft of 4 m, 5 m, and 6 m in given environmental conditions. The results show that the hydrodynamic responses of the large floater with air cushions depend not only on the wave conditions but also on the mass of the water column, air cushion height, and air pressure distribution. In addition, the hydrodynamic characteristics can be tuned resulting in small dynamic responses in a particular sea state by changing the draft and water plug height. The floating technique of the LPCBF with supported air cushions in waves is highly competitive for saving cost while using few expensive types of equipment during the towing transportation.
Tailoring the energy level alignment at the Co/Alq3 interface by controlled cobalt oxidation
Authors: Haag Norman , Steil Sabine , Großmann Nicolas , Fetzer Roman , Cinchetti Mirko , Aeschlimann Martin
Published: December 2013

We have studied the influence of oxygen exposure at the prototypical interface between cobalt and the organic semiconductor tris(8-hydroxyquinoline)aluminum (III) (Alq3) by photoemission spectroscopy. We find that oxidation of the cobalt leads to a gradual suppression of hybrid interface states, to a progressive change in the work function and to a continuous energetic shift of the molecular orbitals towards higher binding energies. Based on these observations, we propose controlled oxidation of the ferromagnetic electrode as an easy and effective possibility to tune the performance of organic spintronics devices.
Nonvolatile electric-field modulation of magnetic anisotropy in perpendicularly magnetized L1-FePt/(001)[Pb(Mg1/3Nb2/3)]0.7-(PbTiO3)0.3 heterostructures
Authors: Tsai Wu-Chang , Liao Sheng-Chieh , Huang Kuo-Feng , Wang Ding-Shuo , Lai Chih-Huang
Published: December 2013

We grow perpendicular L10-FePt films epitaxially on (001)[Pb(Mg1/3Nb2/3)]0.7-(PbTiO3)0.3 ferroelectric substrates. Due to the magnetostriction effect, the out-of-plane coercivity (Hc⊥) of the L10-FePt varies with applied electric fields, showing an asymmetric butterfly-like loop. The Hc⊥ at the zero-electric-field state (Hc⊥,0) shows a nonvolatile change, depending on the direction of the poling electric field. The magnitude of nonvolatile magnetic anisotropy change, induced by the ferroelectric field effect, can be comparable to the anisotropy change induced by pure electric fields. The nonvolatile magnetic anisotropy change is inversely proportional to the FePt thickness and can be eliminated by inserting a metallic intermediate layer.
Design and experiment of a cross-shaped mode converter for high-power microwave applications
Authors: Peng Shengren , Yuan Chengwei , Zhong Huihuang , Fan Yuwei
Published: December 2013

A compact mode converter, which is capable of converting a TM01 mode into a circularly polarized TE11 mode, was developed and experimentally studied with high-power microwaves. The converter, consisting of two turnstile junctions, is very short along the wave propagation direction, and therefore is suitable for designing compact and axially aligned high-power microwave radiation systems. In this paper, the principle of a converter working at 1.75 GHz is demonstrated, as well as the experimental results. The experimental and simulation results are in good agreement. At the center frequency, the conversion efficiency is more than 95%, the measured axial ratio is about 0.4 dB, and the power-handing capacity is excess of 1.9 GW.
Polyphosphonium-based bipolar membranes for rectification of ionic currents
Authors: Gabrielsson Erik O. , Berggren Magnus
Published: December 2013

Bipolar membranes (BMs) have interesting applications within the field of bioelectronics, as they may be used to create non-linear ionic components (e.g., ion diodes and transistors), thereby extending the functionality of, otherwise linear, electrophoretic drug delivery devices. However, BM based diodes suffer from a number of limitations, such as narrow voltage operation range and/or high hysteresis. In this work, we circumvent these problems by using a novel polyphosphonium-based BM, which is shown to exhibit improved diode characteristics. We believe that this new type of BM diode will be useful for creating complex addressable ionic circuits for delivery of charged biomolecules.
Structural, dynamic, and vibrational properties during heat transfer in Si/Ge superlattices: A Car-Parrinello molecular dynamics study
Authors: Ji Pengfei , Zhang Yuwen , Yang Mo
Published: December 2013

The structural, dynamic, and vibrational properties during heat transfer process in Si/Ge superlattices are studied by analyzing the trajectories generated by the ab initio Car-Parrinello molecular dynamics simulation. The radial distribution functions and mean square displacements are calculated and further discussions are made to explain and probe the structural changes relating to the heat transfer phenomenon. Furthermore, the vibrational density of states of the two layers (Si/Ge) are computed and plotted to analyze the contributions of phonons with different frequencies to the heat conduction. Coherent heat conduction of the low frequency phonons is found and their contributions to facilitate heat transfer are confirmed. The Car-Parrinello molecular dynamics simulation outputs in the work show reasonable thermophysical results of the thermal energy transport process and shed light on the potential applications of treating the heat transfer in the superlattices of semiconductor materials from a quantum mechanical molecular dynamics simulation perspective.
Enhanced Fano resonance in silver ellipsoidal plasmonic crystal cavity
Authors: Dillu Venus , Sinha R. K.
Published: December 2013

Enhancement in the asymmetric line shape of Fano resonance is observed and extensively examined for cavities in plasmonic crystals of ellipsoidal silver nanoparticles with hexagonal arrangement. Scattering models for ellipsoidal and cylindrical nanoparticles are compared and it is found that the spectral interference between the cavity mode and the background scattering mode results in a sharp asymmetric peak, which is the defining characteristic of Fano resonance. It is found that the cavity in ellipsoidal nanoparticles yields high transmission at a wavelength of 1600 nm compared with its cylindrical counterpart. Higher harmonic generation is also observed, which confirms the ultrahigh cavity response in ellipsoidal nanoparticles. The effect of power variation on the Fano resonance profile is described, and its application in the field of switching is explored. In addition, the influence of mutual interparticle coupling on Fano line shapes for transverse electric and transverse magnetic polarization is reported. The extraordinary rise in asymmetric line shapes of the Fano resonance promises profound applications in the field of sensing, switching, and lasing devices.