bluuebunny/crossref_metadata_2025 huggingface dataset:
Analysis of terahertz generation via nanostructure enhanced plasmonic excitations
Authors: Gao Yaohui , Chen Meng-Ku , Yang Chia-En , Chang Yun-Ching , Yin Stuart , Hui Rongqing , Ruffin Paul , Brantley Christina , Edwards Eugene , Luo Claire
Published: October 2009

In this paper, we conduct a quantitative study on the physical mechanism of electrons dynamics near the nanostructured metal film surfaces, as well as the efficiency of generated terahertz radiation associated with different types of nanostructures. The simulation results show that although the oscillating motion of emitted electrons outside the metal surface may affect the terahertz generation efficiency to some extent, this efficiency is predominantly determined by the electric field magnitude inside the metal film associated with nanostructure enhanced plasmonic excitations. Due to the field enhancement effect of the nanostructure, an appropriately designed nanostructured surface could greatly enhance the strength of generated terahertz signal via the increased nonlinear interactions between the light and the nanostructures.
Transport simulations of reversed field pinch plasmas: An integrated model coupling magnetohydrodynamics and impurity physics
Authors: Predebon I. , Paccagnella R. , Puiatti M. E. , Valisa M.
Published: October 2009

An integrated one-dimensional model for the description of plasma transport in the reversed field pinch is presented. The model unifies magnetohydrodynamics and particle/energy transport in a single framework, with the inclusion of impurity physics. Up to now, the applications of the code concern the chaotic regimes of the reversed field pinch, with the intent to clarify the role of the turbulent dynamo for the discharge sustainment and the relative weight of the source/sink terms in the energy balance equations.
Dissociative charge exchange dynamics of HN2+ and DN2+
Authors: Savee John D. , Thomas Richard D. , Mann Jennifer E. , Continetti Robert E.
Published: October 2009

Translational spectroscopy coupled with coincidence detection techniques has been used to study the dissociation dynamics of ground state H/D+N2 products resulting from charge exchange between keV beams of HN2+/DN2+ and cesium. Analysis of the product kinetic energy release suggests that dissociation of HN2 and DN2 proceeds from initial populations in the A2″, 2 A2′, and 3s Rydberg electronic states of the neutral molecule. Although all three excited electronic states must eventually couple to the 1 A2′ ground state of HN2/DN2, the resulting dissociation dynamics exhibit a significant dependence on the initial electronic state. Potential mechanisms are discussed in light of the observed product kinetic energy release distributions.
Ionic liquid-functionalized carbon nanoparticles-modified cathode for efficiency enhancement in polymer solar cells
Authors: Chen Xiaohong , Yang Jiaxiang , Lu Jiong , Manga Kiran Kumar , Loh Kian Ping , Zhu Furong
Published: October 2009

The power conversion efficiency (PCE) of regioregular poly(3-hexylthiophene) (P3HT) and {6,6}-phenyl C61-butyric acid methylester (PCBM)-based polymer solar cells was increased using an ionic liquid-functionalized carbon nanoparticles (ILCNs) thin film-modified cathode. The PCE of P3HT:PCBM based-polymer solar cells with a conventional aluminum (Al)-only cathode was increased by 20%–30% when the identical devices were made with an ILCNs-modified Al cathode, but its PCE was 10% lower than that of devices with LiF/Al cathode, measured under AM1.5G illumination of 100 mW/cm2. The ILCN interlayer approach, however, offers practical advantages to LiF in terms of its solution-processability, which is compatible with low cost, large area, and flexible solar cell fabrication.
Electron conductance of N,N′-bis-(1-naphthl)-diphenyl-1,1′-biphenyl-4,4′-diamine at low temperatures
Authors: Gao X. D. , He Y. , Zhang S. T. , Yin X. R. , Ding B. F. , Ding X. M. , Hou X. Y.
Published: October 2009

The electron conductance of N,N′-bis-(1-naphthl)-diphenyl-1,1′-biphenyl-4,4′-diamine was found to increase with decreasing temperature experimentally. This phenomenon is quite abnormal since for most organic materials the conductance increases with increasing temperature. A probable explanation was given according to a previous work about soliton diffusion in polyacetylene within the framework of SSH model.
The photoelectron spectrum of the ethoxide anion: Conical intersections, the spin-orbit interaction, and sequence bands
Authors: Dillon Joseph J. , Yarkony David R.
Published: October 2009

The negative ion photoelectron spectrum of the ethoxide anion (ethoxide-h5) and that of its fully deuterated analog, ethoxide-d5, are calculated using the multimode vibronic coupling approach. A two state quasidiabatic Hamiltonian Hd is constructed which includes all terms through second order in the full 18 dimensional internal coordinate space. Hd is centered at the ab initio determined minimum energy crossing (MEX) point on the symmetry-allowed A2″−A2′ accidental seam of conical intersection and determined from ab initio energy gradients and derivative couplings. It reproduces the local topography of the A2″−A2′ MEX, in addition to accurately representing the geometries, energetics, and harmonic frequencies of equilibrium and saddle point structures located on the ground electronic state potential energy surface in the vicinity of the MEX. Spin-orbit effects are included. The results for ethoxy-h5 are compared to photoelectron and slow electron velocity-map imaging (SEVI) spectra. By comparing the measured and predicted photoelectron spectrum, the accuracy of the electronic structure treatment is inferred. The existence of sequence bands in the SEVI spectrum is established.
Percolation of two-dimensional multiwall carbon nanotube networks
Authors: Lee Heon Sang , Yun Chang Hun , Kim Sun Kug , Choi Ji Hoon , Lee Cheol Jin , Jin Hyoung-Joon , Lee Hyunjung , Park Sang Joon , Park Min
Published: October 2009

We highlight the significance of multiwall carbon nanotube (MWCNT) shape on the electrical percolation. For rodlike MWCNTs, percolation threshold depends on aspect ratio (L/d). For random coil-like MWCNTs, the percolation threshold does not depend on L/d but depends on the shape factor of MWCNTs represented by the ratio between static bending persistence length and diameter. Surface resistivities of various MWCNTs converge into single curve when we plot their dimensionless surface concentration versus surface resistivity. The surface resistivity of MWCNT films decrease with increasing temperature, particularly at low concentrations, indicating the films can be used as a negative temperature coefficient thermistor.
Extended performance GeSn/Si(100) p-i-n photodetectors for full spectral range telecommunication applications
Authors: Mathews Jay , Roucka Radek , Xie Junqi , Yu Shui-Qing , Menéndez José , Kouvetakis John
Published: October 2009

First-generation n-i-GeSn/p-Si(100) photodiode detectors with Ge0.98Sn0.02 active layers were fabricated under complementary metal oxide semiconductor compatible conditions. It is found that, even at this low Sn concentration, the detector quantum efficiencies are higher than those in comparable pure-Ge device designs processed at low temperature. Most significantly, the spectral range of the GeSn device responsivity is dramatically increased—to at least 1750 nm—well beyond the direct band gap of Ge (1550 nm). This allows coverage of all telecommunication bands using entirely group IV materials.
Electronic properties of ZnO field-effect transistors fabricated by spray pyrolysis in ambient air
Authors: Adamopoulos George , Bashir Aneeqa , Wöbkenberg Paul H. , Bradley Donal D. C. , Anthopoulos Thomas D.
Published: October 2009

We report the application of spray pyrolysis (SP) for the deposition of high quality zinc oxide (ZnO) films and the fabrication of thin-film transistors. The chemical, structural, optical, and electronic properties of as-deposited ZnO films are studied using infrared spectroscopy, atomic force microscopy, UV-visible spectroscopic ellipsometry, and field-effect measurements. SP ZnO films are found to be uniform and polycrystalline with a band gap of 3.32 eV. ZnO transistors exhibit n-channel characteristics with electron mobility in the range 10–22 cm2/Vs. Device performance is found to depend on the work function of source/drain metal electrodes and on the device architecture employed.
Spurious-free cantilever excitation in liquid by piezoactuator with flexure drive mechanism
Authors: Asakawa Hitoshi , Fukuma Takeshi
Published: October 2009

We have developed a cantilever holder for spurious-free cantilever excitation in liquid by piezoactuator. In the holder, generation and propagation of an acoustic wave are suppressed by “acoustic barriers,” i.e., boundaries between two materials having significantly different acoustic impedance while cantilever vibration is excited by “flexure drive mechanism” utilizing elastic deformation of a flexure hinge made of a material having a low elastic modulus. The holder enables to obtain amplitude and phase curves without spurious peaks in liquid using a piezoactuator, which ensures stability and accuracy of dynamic-mode atomic force microscopy in liquid.
Close-packed hemiellipsoid arrays: A photonic band gap structure patterned by nanosphere lithography
Authors: Fu Wai Yuen , Wong Kenneth Kin-Yip , Choi H. W.
Published: October 2009

A self-assembled hexagonal close-packed hemiellipsoidal photonic crystal structure was fabricated on GaN material. An ordered monolayer silica nanosphere coating served as a hard mask in an inductively coupled plasma etching process. The shape of the arrayed hemiellipsoids can be controlled by adjusting the etch selectivities and durations according to the fabrication model. The existence of a photonic band gap is established through planar transmissivity measurement whereby a transmission dip centered at 440 nm was identified. A threefold enhancement in light extraction was achieved, as determined from the measured angular photoluminescence emission pattern.
Spherical brushes within spherical cavities: A self-consistent field and Monte Carlo study
Authors: Cerdà Juan J. , Sintes Tomás , Toral Raúl
Published: October 2009

We present an extensive numerical study on the behavior of spherical brushes confined into a spherical cavity. Self-consistent field (SCF) and off-lattice Monte Carlo (MC) techniques are used in order to determine the monomer and end-chain density profiles and the cavity pressure as a function of the brush properties. A comparison of the results obtained via SCF, MC, and the Flory theory for polymer solutions reveals SCF calculations to be a valuable alternative to MC simulations in the case of free and softly compressed brushes, while the Flory’s theory accounts remarkably well for the pressure in the strongly compressed regime. In the range of high compressions, we have found the cavity pressure P to follow a scale relationship with the monomer volume fraction v, P∼vα. SCF calculations give α=2.15±0.05, whereas MC simulations lead to α=2.73±0.04. The underestimation of α by the SCF method is explained in terms of the inappropriate account of the monomer density correlations when a mean field approach is used.
Single-crystalline cubic MgZnO films and their application in deep-ultraviolet optoelectronic devices
Authors: Wang L. K. , Ju Z. G. , Zhang J. Y. , Zheng J. , Shen D. Z. , Yao B. , Zhao D. X. , Zhang Z. Z. , Li B. H. , Shan C. X.
Published: October 2009

By employing a relatively low growth temperature and oxygen-rich conditions, single-crystalline cubic MgZnO films were prepared. A solar-blind deep ultraviolet (DUV) photodetector was finished on the MgZnO film. The maximum responsivity of the photodetector is 396 mA/W at 10 V bias, which is almost three orders of magnitude larger than the highest value ever reported in MgZnO-based solar-blind photodetectors. The dark current density is 1.5×10−11 A/cm2, comparable with the smallest value ever reported in solar-blind photodetectors. The improved performance reveals that the single-crystalline cubic MgZnO films have great potential applications in DUV optoelectronic devices.
Carbon-coated silicon nanowire array films for high-performance lithium-ion battery anodes
Authors: Huang Rui , Fan Xing , Shen Wanci , Zhu Jing
Published: October 2009

Carbon-coated silicon nanowire array films prepared by metal catalytic etching of silicon wafers and pyrolyzing of carbon aerogel were used for lithium-ion battery anodes. The films exhibited an excellent first discharge capacity of 3344 mAh g−1 with a Coulombic efficiency of 84% at a rate of 150 mA g−1 between 2 and 0.02 V and a significantly enhanced cycling performance, i.e., a reversible capacity of 1326 mAh g−1 was retained after 40 cycles. These improvements were attributed to the uniform and continuous carbon coatings, which increased electronic contact and conduction and buffered large volume changes during lithium ion insertion/extraction.
A theoretical study of water equilibria: The cluster distribution versus temperature and pressure for (H2O)n, n=1–60, and ice
Authors: Lenz Annika , Ojamäe Lars
Published: October 2009

The size distribution of water clusters at equilibrium is studied using quantum-chemical calculations in combination with statistical thermodynamics. The necessary energetic data is obtained by quantum-chemical B3LYP computations and through extrapolations from the B3LYP results for the larger clusters. Clusters with up to 60 molecules are included in the equilibrium computations. Populations of different cluster sizes are calculated using both an ideal gas model with noninteracting clusters and a model where a correction for the interaction energy is included analogous to the van der Waals law. In standard vapor the majority of the water molecules are monomers. For the ideal gas model at 1 atm large clusters [56-mer (0–120 K) and 28-mer (100–260 K)] dominate at low temperatures and separate to smaller clusters [21–22-mer (170–280 K) and 4–6-mer (270–320 K) and to monomers (300–350 K)] when the temperature is increased. At lower pressure the transition from clusters to monomers lies at lower temperatures and fewer cluster sizes are formed. The computed size distribution exhibits enhanced peaks for the clusters consisting of 21 and 28 water molecules; these sizes are for protonated water clusters often referred to as magic numbers. If cluster-cluster interactions are included in the model the transition from clusters to monomers is sharper (i.e., occurs over a smaller temperature interval) than when the ideal-gas model is used. Clusters with 20–22 molecules dominate in the liquid region. When a large icelike cluster is included it will dominate for temperatures up to 325 K for the noninteracting clusters model. Thermodynamic properties (Cp, ΔH) were calculated with in general good agreement with experimental values for the solid and gas phase. A formula for the number of H-bond topologies in a given cluster structure is derived. For the 20-mer it is shown that the number of topologies contributes to making the population of dodecahedron-shaped cluster larger than that of a lower-energy fused prism cluster at high temperatures.
Universal scaling of the electron distribution function in one-dimensional simulations of relativistic laser-plasma interactions
Authors: Sherlock M.
Published: October 2009

A formula based on simulations is given for the distribution function of energetic electrons which stream in the forward direction when a relativistically intense laser pulse irradiates a short-scale-length dense plasma at normal incidence. If the energy absorption fraction is known, the entire function can be characterized in terms of the laser intensity I. A number of important characteristics can then be obtained, including the fast-electron energy, current density, and angle of ejection. An objective means for calculating the fast-electron energy is proposed which gives a value of ∼0.6 of the vacuum oscillatory energy. This reduction in energy is shown to be consistent with the energy required to draw a return current. These results could be used to provide the characteristics of the electron source in theory and simulation of intense laser-solid interactions.
Generation of extreme ultraviolet radiation with a Bessel–Gaussian beam
Authors: Van Dao Lap , Dinh Khuong Ba , Hannaford Peter
Published: October 2009

The generation of few high-order harmonics in the extreme ultraviolet is enhanced by focusing the fundamental femtosecond laser beam with a combination of lens and axicon in an infinite gas cell. We show that this combination leads to an improvement in the phase-matched generation of harmonics in the cutoff region, with a higher photon flux and a better spatial beam profile. A high atom density through the use of a high gas pressure can be used and the absorption limit of the harmonic generation is obtained for an interaction length of a few millimeters.
Ferromagnet-semiconductor nanowire coaxial heterostructures grown by molecular-beam epitaxy
Authors: Hilse M. , Takagaki Y. , Herfort J. , Ramsteiner M. , Herrmann C. , Breuer S. , Geelhaar L. , Riechert H.
Published: October 2009

GaAs–MnAs core-shell structures are grown by molecular-beam epitaxy using wurtzite GaAs nanowires on GaAs(111)B. The nanowire structures curve due to the strain at the heterointerface when the substrate is not rotated during the growth, evidencing the diffusion length in the MnAs overgrowth being less than the perimeter of the columns. The MnAs growth is thus demonstrated to take place by direct deposition on the sidewall. The MnAs envelope is m-plane-oriented with the c-axis along the nanowire axis. The magnetic easy axis hence lies in the surface plane of the substrate, which is confirmed by magnetization measurements and magnetic-force microscopy.
Crossover of angular dependent magnetoresistance with the metal-insulator transition in colossal magnetoresistive manganite films
Authors: Chen Y. Z. , Sun J. R. , Zhao T. Y. , Wang J. , Wang Z. H. , Shen B. G. , Pryds N.
Published: October 2009

The temperature and magnetic field dependence of angular dependent magnetoresistance (AMR) along two orthogonal directions ([100] and [01¯1]) was investigated in a charge-orbital-ordered Sm0.5Ca0.5MnO3 (SCMO) film grown on (011)-oriented SrTiO3 substrates. A dramatic decrease of AMR magnitude in both directions was observed with the appearance of magnetic-field-induced metal-insulator transition, which further led to a sign crossover in the AMR effect. The AMR crossover may give a direct evidence of the drastic modification of electronic structure or possible orbital reconstruction with the magnetic-destruction of charge/orbital ordering in SCMO films.
Photoluminescence and Raman scattering in axial Si/Ge nanowire heterojunctions
Authors: Chang H.-Y. , Tsybeskov L. , Sharma S. , Kamins T. I. , Wu X. , Lockwood D. J.
Published: October 2009

In crystalline, dislocation-free, Si/Ge nanowire axial heterojunctions grown using the vapor-liquid-solid technique, photoluminescence and Raman spectroscopy reveal a SiGe alloy transition layer with preferential chemical composition and strain. In addition to the lattice mismatch, strain in Si/Ge nanowires is observed from a temperature dependent study to be affected by the difference in Si and Ge thermal expansion. The conclusions are supported by analytical transmission electron microscopy measurements.
Achievement of 6.03% conversion efficiency of dye-sensitized solar cells with single-crystalline rutile TiO2 nanorod photoanode
Authors: Yang Weiguang , Wan Farong , Wang Yali , Jiang Chunhua
Published: October 2009

The rutile TiO2 nanorods (RTNs) with the length of 40–130 nm and diameters approximately 8–15 nm, containing some 300–500 nm sized RTN aggregates and 6% of anatase TiO2 nanocrystals, were prepared by surfactant-assisted hydrothermal method. The dye-sensitized solar cell (DSC) based on the RTNs exhibited power conversion efficiency of 6.03%. As compared to P25 TiO2 based DSC, RTNs based DSC shows improved light-harvesting and Brunauer–Emmett–Teller surface area, leading to an increase in short-circuit current (Jsc) by 40.6%.
Spin transfer torque switching of magnetic tunnel junctions using a conductive atomic force microscope
Authors: Evarts Eric R. , Cao Limin , Ricketts David S. , Rizzo Nicholas D. , Bain James A. , Majetich Sara A.
Published: October 2009

We show that a nonmagnetic conductive atomic force microscopy probe can be used to read and write magnetic bits using current passed between the tip and bit. The bits were patterned using electron beam lithography from a magnetic tunnel junction (MTJ) film with in-plane shape anisotropy using an MgO tunnel barrier. Probes were made having a thick Pt coating and could deliver up to several milliamps, so that MTJ structures were easily switched repeatedly using the spin transfer torque effect.
A body-centered-cubic polymorph of the Ge2Sb2Te5 phase change alloy
Authors: Cheng Y. Q. , Xu M. , Sheng H. W. , Meng Y. , Han X. D. , Ma E.
Published: October 2009

In Ge2Sb2Te5 (GST), the prototype phase-change alloy for data storage, in situ x-ray diffraction experiments reveal a pressure-induced crystalline-amorphous-crystalline transition sequence, all at the same fixed composition and in one experimental cycle. A body-centered-cubic polymorph is discovered at high pressures; the formation of this phase is attributable to its high packing density rendered possible by the switch from covalent to metallic bonding as predicted by ab initio calculations.
The MoS2 nanotube hybrids
Authors: Remškar M. , Viršek M. , Mrzel A.
Published: October 2009

The MoS2 nanotube hybrids represent a family of nanomaterials, where nanotubes serve as nanoreactors and in some cases also as nanocontainers of MoS2 fullerenelike particles, which have in situ grown in a confined geometry of nanotubes. A simple temperature control of morphology, size, and inner structure of nanohybrids leads to a selective morphology such as coaxial nanotubes, “mama”-tubes with encapsulated nano-onions, the growth of MoS2 nanobuds or it facilitates a release of MoS2 nano-onions, which then form weakly bonded self-assemblies. Growth mechanism is discussed based on atomic probe electron microscopy, x-ray diffraction and high-resolution transmission electron microscopy.
Piezoresistive transduction in multilayer polycrystalline silicon resonators
Authors: Cross J. D. , Ilic B. R. , Zalalutdinov M. K. , Zhou W. , Baldwin J. W. , Houston B. H. , Craighead H. G. , Parpia J. M.
Published: October 2009

We demonstrate piezoresistive transduction of mechanical motion from out-of-plane flexural micromechanical resonators made from stacked thin films. The resonators are fabricated from two highly doped polycrystalline silicon layers separated by an interlayer dielectric. We examine two interlayer materials: thermal silicon dioxide and stoichiometric silicon nitride. We show that via one-time dielectric breakdown, the film stack functions as a vertical piezoresistor effectively transducing the motion of the resonators. We obtain a gauge factor of ∼5, which is sufficient to detect the resonator motion. The simple film stack constitutes a vertically oriented piezoresistor that is readily integrated with micro- and nanoscale resonators.
Modified adiabatic approximation: Charge asymmetry in HD+ and HD
Authors: Strasburger Krzysztof
Published: October 2009

The modified adiabatic approximation is discussed, in which the interaction of electrons with nuclei is partitioned between the electronic and nuclear Hamiltonian, in order to simulate the finite nuclear mass effect. The proposed formalism is universal and can be used in calculations for molecules of any size. The effect of electron localization on the deuteron in vibrationally excited states of HD+ and the permanent dipole moment of HD, typically both explained in terms of nonadiabatic couplings between g and u states, are well reproduced with this method.
Micromechanical magnetometer using an all-silicon nonlinear torsional resonator
Authors: Antonio D. , Dolz M. I. , Pastoriza H.
Published: October 2009

In this work, a micromagnetometer employing a nonlinear torsional resonator with a high quality factor Q is presented experimentally. Oscillatory rotation of a conducting plate in the sensed magnetic field H induces eddy currents that dissipate energy. Due to the nonlinear response of the oscillator, the resulting mechanical damping originates frequency shifts in the resonance curve that depend on H. Nonlinearity results from the electrostatic detection, which introduces high order electrical spring constants. The device is fabricated with a standard silicon process and does not incorporate ferromagnetic materials. An analytical nonlinear model that correctly describes the device is also introduced.
Improved dielectric strength of barium titanate-polyvinylidene fluoride nanocomposite
Authors: Dou Xiaoliang , Liu Xiaolin , Zhang Yong , Feng Huan , Chen Jian-Feng , Du Song
Published: October 2009

Barium titanate-polyvinydene fluoride nanocomposites with improved dielectric strength were prepared, in which on the surface of the barium titanate nanoparticle was coated. The results showed that the dielectric breakdown strength of the nanocomposites increase significantly up to 250 kV/mm and then decrease. Microstructural investigations revealed that the coated barium titanate nanoparticles were well-dispersed in polyvinydene fluoride. Fourier transform infrared spectroscopy confirmed that there is a large coverage of cross-linking in both interfaces of the barium titanate–titanate and the titanate–polyvinydene fluoride, which can connect the composites to form an organically integrated body, which result in the increase of the dielectric strength of the nanocomposites.
Enhancing the photocurrent in poly(3-hexylthiophene)/[6,6]-phenyl C61 butyric acid methyl ester bulk heterojunction solar cells by using poly(3-hexylthiophene) as a buffer layer
Authors: Liang Chin-Wei , Su Wei-Fang , Wang Leeyih
Published: October 2009

This work presents an approach for improving the unfavorable vertical composition gradients of poly(3-hexylthiophene) (P3HT) and [6,6]-phenyl C61 butyric acid methyl ester (PCBM) in the photoactive layer of bulk heterojunction solar cells. The proposed method involves simply depositing a thin layer of P3HT on top of poly(3,4-ethylenedioxythiophene):poly(styrene-sulfonate) (PEDOT:PSS) prior to the P3HT:PCBM blend is spin coated. The results from photoluminescence and photovoltaic measurements indicate that incorporating this P3HT layer significantly enhances the electron blocking ability of PEDOT:PSS, the efficiency of photoinduced electron transfer and the photocurrent of the device, resulting in an improvement of the power conversion efficiency from 3.98% to 5.05%.
Silver-copper alloy nanoparticles for metal enhanced luminescence
Authors: Chowdhury Sanchari , Bhethanabotla Venkat R. , Sen Rajan
Published: October 2009

Large metal enhanced luminescence was realized at the vicinity of easily fabricated Ag–Cu alloy nanoparticles upon tuning of their surface plasmon resonance spectra by changing only one experimental variable—the annealing temperature, for maximum spectral overlap with the emission and excitation spectra of the luminophores. We observed strong emission enhancement of luminophores (141.48±19.20 times for Alexa Fluor 488 and 23.91±12.37 times for Alexa Fluor 594) at the vicinity of these Ag–Cu nanoparticles, which is significantly larger than for pure Ag nanoparticles. We present theoretical calculations to provide insights into these experimental findings.
Ionized-oxygen vacancies related dielectric relaxation in heteroepitaxial K0.5Na0.5NbO3/La0.67Sr0.33MnO3 structure at elevated temperature
Authors: Miao J. , Xu X. G. , Jiang Y. , Cao L. X. , Zhao B. R.
Published: October 2009

Ferroelectric K0.5Na0.5NbO3 (KNN) thin film was epitaxially grown on La0.67Sr0.33MnO3 (LSMO) buffered LaAlO3 substrate by pulse laser deposition. The crystallographic structure of KNN/LSMO was confirmed by x-ray diffraction. Interestingly, a dielectric relaxor feature was found in the temperature range 200–350 °C. The activation energies for relaxation and conduction of the films were found to be 1.87 and 0.63–0.71 eV, respectively. The mechanism for dielectric relaxation in KNN/LSMO structure was discussed under a thermally activated process. The remnant polarization and coercive field of the films were 21.3 μC/cm2 and 91 kV/cm, respectively.
Graphitic carbon growth on Si(111) using solid source molecular beam epitaxy
Authors: Hackley J. , Ali D. , DiPasquale J. , Demaree J. D. , Richardson C. J. K.
Published: October 2009

Solid source molecular beam epitaxy is used to explore the growth of carbon films directly on Si(111). It is shown that graphitic carbon is grown by the implementation of a thin amorphous carbon film that suppresses the formation of SiC precipitates. Raman scattering measurements show the D and G vibrational phonon modes, indicating graphitic ordering in the carbon film. X-ray photoelectron spectroscopy is used to verify the formation of sp2 bonds in the graphitic carbon films and confirms the suppression of SiC.
Theoretical investigation of the potential energy surface of the van der Waals complex CH4–N2
Authors: Kalugina Yulia N. , Cherepanov Victor N. , Buldakov Mikhail A. , Zvereva-Loëte Natalia , Boudon Vincent
Published: October 2009

The interaction potential energy surface of the van der Waals CH4–N2 complex has been calculated for a broad range of intermolecular separations and configurations in the approximation of rigid interacting molecules at the CCSD(T) and MP2 levels of theory using the correlation consistent aug-cc-pVTZ basis set. The BSSE correction was taken into account for all the calculations. The most stable configurations of the complex were found. Binding energies were calculated in the CBS limit with accounting for the molecular deformations. The harmonic and anharmonic fundamental vibrational frequencies and rotational constants for the ground and first excited vibrational states were calculated for the most stable configurations at the MP2 level of theory with BSSE correction. Fitting parameters were found for the most stable configuration for the Lennard-Jones and Esposti–Werner potentials.
Dual-gate organic thin film transistors as chemical sensors
Authors: Park Young Min , Salleo Alberto
Published: October 2009

An organic/inorganic hybrid sensing device is proposed based on a dual-gate organic thin film transistor architecture using polythiophenes as semiconductors and AlOx as the top dielectric. When a polar molecule adsorbs on the top dielectric, the threshold voltage of the bottom gate transistor shifts leading to several orders of magnitude increase of the current at an appropriately chosen gate voltage. The devices are tested by exposing them to a saturated water atmosphere, which leads to a four orders of magnitude current increase within one minute. This sensor design maintains some advantages of organic semiconductors such as low-temperature processing and fabrication on flexible substrates. Finally, it can be operated at low voltages with the potential for extremely low-power operation.
Observations on the melting of Au nanoparticle deposits and alloying with Ni via in situ synchrotron radiation x-ray diffraction
Authors: Kao Tzu-Hsuan , Song Jenn-Ming , Chen In-Gann , Dong Teng-Yuan , Hwang Weng-Sing , Lee Hsin-Yi
Published: October 2009

Through monitoring the evolution of the x-ray diffraction peaks, the transient low temperature melting of Au nanoparticles and following alloying with the substrate were demonstrated via in situ synchrotron radiation x-ray diffraction. Upon heating, the broad diffraction peak of nanosized Au particles with the average diameter of 2.5 nm was suppressed at about 200 °C and soon became sharp due to melting and subsequent solidification. If the test was conducted on a Ni film, an unstable intermetallic compound Au3Ni appeared with crystallized Au, which resulted from the reaction between the supercooled liquid of Au and Ni. However, it decomposed at 275 °C and above.
Epitaxial growth and magnetoelectric relaxor behavior in multiferroic 0.8Pb(Fe1/2Nb1/2)O3–0.2Pb(Mg1/2W1/2)O3 thin films
Authors: Peng Wei , Lemée N. , Dellis J.-L. , Shvartsman V. V. , Borisov P. , Kleemann W. , Trontelj Z. , Holc J. , Kosec M. , Blinc R. , Karkut M. G.
Published: October 2009

We present electric and magnetic properties of 0.8Pb(Fe1/2Nb1/2)O3–0.2Pb(Mg1/2W1/2)O3 films epitaxially grown on (001) SrTiO3 substrates using pulsed laser deposition. A narrow deposition window around 710 °C and 0.2 mbar has been identified to achieve epitaxial single-phase thin films. A typical Vogel–Fulcher relaxorlike dielectric and magnetic susceptibility dispersion is observed, suggesting magnetoelectric relaxor behavior in these films similar to the bulk. We determine a magnetic cluster freezing temperature of 36 K, while observing weak ferromagnetism via magnetic hysteresis loops up to 300 K.
Bipolar resistive electrical switching of silver tetracyanoquinodimethane based memory cells with dedicated silicon dioxide “switching layer”
Authors: Müller R. , Genoe J. , Heremans P.
Published: October 2009

We demonstrate reliable and durable (>100 write/erase cycles) bipolar resistive electrical switching of silver tetracyanoquinodimethane (AgTCNQ) based memories by incorporating a dedicated SiO2 “switching layer” and limiting the on state current by a current compliance. Switching back to the off state required voltages of opposite polarity with higher current intensity; keeping the same current compliance level typically prevented—and exceptionally lead to time delayed—off switching. Simultaneous growth and dissolution of the conductive channels could be observed during the on to off transition. All of these findings give further evidence that the switching mechanism involves electrochemical processes.
Structure of penetrable sphere fluids and mixtures near a slit hard wall: A modified bridge density functional approximation
Authors: Kim Soon-Chul , Seong Baek-Seok , Suh Soong-Hyuck
Published: October 2009

The modified density functional theory, which is based both on the bridge density functional and the contact value theorem, has been proposed for the structural properties of penetrable sphere fluids and their mixtures near a slit hard wall. The Verlet-modified bridge function proposed by Choudhury and Ghosh [J. Chem. Phys. 119, 4827 (2003)] for one-component system has been extended for fluid mixtures. The radial distribution functions obtained from the Verlet-modified bridge function are in excellent agreement with computer simulations over a wide range of density and temperature and better than those obtained from the standard integral theories including the Percus–Yevick and hypernetted-chain closures. The calculated particle density distributions confined in a slit pore are also found to be reasonably good compared to the simulation data. Even for high density systems the accuracy of the hypernetted-chain and the mean-field approximation functionals increase with increasing temperature. However, the agreement between theory and simulation slightly deteriorates in the systems of low temperature.
Conversion of magnetic structure by slight dopants in geometrically frustrated antiperovskite Mn3GaN
Authors: Takenaka K. , Inagaki T. , Takagi H.
Published: October 2009

We found that a few percent of Fe dopants at the Mn sites alters the antiferromagnetic spin structure of Mn3GaN and induces a first-order antiferromagnetic-ferromagnetic phase transition accompanied by a large volume change. The drastic conversion of the spin alignment originates from phase competition due to a geometrical frustration in the Mn6N octahedron. This result demonstrates that the magnetic and other unique related properties of manganese antiperovskites are controllable by element substitution. Comparing with the ferromagnetic state in Mn3Ga(N1−xCx), we discuss a possible spin structure that accounts for the conversion of the magnetic states.
Ultraviolet emission from a ZnO rod homojunction light-emitting diode
Authors: Sun X. W. , Ling B. , Zhao J. L. , Tan S. T. , Yang Y. , Shen Y. Q. , Dong Z. L. , Li X. C.
Published: October 2009

Ultraviolet electroluminescence was demonstrated at room temperature from a ZnO rod homojunction light-emitting diode array. The p-type doping was realized by phosphorous (P) ion implantation into defect-free ZnO rods followed by annealing. High resolution transmission electron microscopy shows the lattice compression of annealed single crystalline P-doped ZnO rod compared to the as-grown ZnO rod, suggesting atomically incorporation of P into the ZnO wurtzite structure. p-type doping was confirmed by low temperature photoluminescence spectra and single rod current-voltage characterization.
ADAR1 is required for hematopoietic progenitor cell survival via RNA editing
Authors: XuFeng Richard , Boyer Matthew J. , Shen Hongmei , Li Yanxin , Yu Hui , Gao Yindai , Yang Qiong , Wang Qingde , Cheng Tao
Published: October 2009

Adenosine Deaminase Acting on RNA 1 (ADAR1) is an RNA-editing enzyme that converts adenosine to inosine, following RNA transcription. ADAR1's essential role in embryonic development, especially within the hematopoietic lineage, has been demonstrated in knock-out mice. However, a specific role for ADAR1 in adult hematopoietic progenitor cells (HPCs) remains elusive. In this report, we show that ADAR1 is required for survival of differentiating HPCs as opposed to more primitive cells in adult mice by multiple strategies targeting floxed ADAR1 for deletion by Cre recombinase. As a consequence, ADAR1-deficient hematopoietic stem cells (HSCs) were incapable of reconstituting irradiated recipients although being phenotypically present in the recipient bone marrow. While an effect on HSCs cannot be completely ruled out, the preferential effect of ADAR1 absence on HPCs over more primitive hematopoietic cells was consistent with the increased expression of ADAR1 within HPCs, as well as the inability of ADAR1-deficient HPCs to form differentiated colonies and increased apoptotic fraction during
ex vivo
culture. Moreover, we have obtained direct evidence that ADAR1 functions in HPCs via an RNA-editing dependent mechanism. Therefore, ADAR1 plays an essential role in adult hematopoiesis through its RNA editing activity in HPCs.
Optical control of zebrafish behavior with halorhodopsin
Authors: Arrenberg Aristides B. , Del Bene Filippo , Baier Herwig
Published: October 2009

Expression of halorhodopsin (NpHR), a light-driven microbial chloride pump, enables optical control of membrane potential and reversible silencing of targeted neurons. We generated transgenic zebrafish expressing enhanced NpHR under control of the Gal4/UAS system. Electrophysiological recordings showed that eNpHR stimulation effectively suppressed spiking of single neurons in vivo. Applying light through thin optic fibers positioned above the head of a semi-restrained zebrafish larva enabled us to target groups of neurons and to simultaneously test the effect of their silencing on behavior. The photostimulated volume of the zebrafish brain could be marked by subsequent photoconversion of co-expressed Kaede or Dendra. These techniques were used to localize swim command circuitry to a small hindbrain region, just rostral to the
commissura infima Halleri
. The kinetics of the hindbrain-generated swim command was investigated by combined and separate photo-activation of NpHR and Channelrhodopsin-2 (ChR2), a light-gated cation channel, in the same neurons. Together this “optogenetic toolkit” allows loss-of-function and gain-of-function analyses of neural circuitry at high spatial and temporal resolution in a behaving vertebrate.
Vortex structures in dense electron–positron–ion plasmas
Authors: Haque Q
Published: October 2009

A linear dispersion relation for electrostatic quantum drift and acoustic waves has been found for dense electron–positron–ion magnetoplasmas. Both the fermion and thermal temperature effects have been considered for electrons and positrons. In the nonlinear regime, a stationary solution in the form of dipolar vortices has been obtained. For illustration, the results were applied to the astrophysical plasma of the atmosphere of neutron stars/pulsars.
Interaction of highly charged clusters with surface
Authors: Parilis E S
Published: October 2009

The purpose of this paper is to draw attention to phenomena occurring on solid surfaces under impact of new kinds of projectiles—slow, very large and highly charged clusters produced in modern electrospray ionization sources.

It is known that slow highly charged atomic ions, for instance Xe+44, approaching a non-metal surface cause sputtering, erosion and create craters and blisters via the mechanism of Coulomb explosion following a cascade Auger neutralization, emitting vast amounts of secondary electrons.

The same mechanism should create analogous nano-features on a non-metal surface under impacts of clusters containing up to 108–109 molecules with a mass of up to 109–1010 amu and a diameter as large as 103 nm, their charge reaching several 103 e, albeit the charge-to-mass ratio would not exceed 10−7–10−6 e amu−1. When accelerated using a voltage of up to 104 V, the clusters can acquire a kinetic energy of 104 keV, but a very slow velocity, less than 5×104 cm s−1, which corresponds to about 10−2 eV atom−1, well below the threshold of kinetic electron emission. The conditions are favorable for Auger neutralization-induced potential electron emission.

The estimates, inevitably approximate in the absence of any experimental data, predict that the diameter of the craters could be around 10 nm, the number of sputtered atoms could be as large as 105 atoms per cluster and the yield of ejected electrons could reach up to several thousand electrons per cluster. These numbers show that both experimental studies of the phenomena and a search for their possible applications are worth performing.
Lipoprotein components and risk of congestive heart failure in 84 740 men and women in the Apolipoprotein MOrtality RISk study (AMORIS)
Authors: Holme Ingar , Aastveit Are H. , Hammar Niklas , Jungner Ingmar , Walldius Göran
Published: October 2009

Aims

Few studies have analysed the influence of lipoprotein components (LC) on the development of congestive heart failure (HF) in large healthy populations. We examined LC together with glucose, haptoglobin (Hp), and uric acid (UA) as risk factors for HF in the Apolipoprotein MOrtality RISk (AMORIS) study. We also explored the possible interaction between these factors and the apolipoprotein B to apolipoprotein A‐1 ratio (apoB/apoA‐1) in HF.

Methods and results

This was a prospective study of HF conducted over 11.8 years through links with the Swedish hospital discharge and mortality registers. Lipoprotein components and other risk factors were measured in 84 740 men and women during health check‐ups. All LC were strongly associated with HF per gender adjusted for risk factors. Relationships were stronger for men than for women. Among LC the apoB/apoA‐1 ratio was the strongest risk factor for HF in men and triglycerides (TG) in women, but differences in strength were not large. The Hp and UA added predictive information to that of the apoB/apoA‐1 ratio, but glucose did not. There was no detectable interaction (synergistic effects) on relative risk between apoB/apoA‐1 and these three additional factors.

Conclusion

Over and above adjustment factors, the apoB/apoA‐1 ratio and TG were the most predictive of the LC, but all LC were highly significantly related to the development of HF.
Evaluating management strategies to implement the recovery plan for Iberian hake (Merluccius merluccius); the impact of censored catch information
Authors: Jardim Ernesto , Cerviño Santiago , Azevedo Manuela
Published: October 2009

Jardim, E., Cerviño, S., and Azevedo, M. 2010. Evaluating management strategies to implement the recovery plan for Iberian hake (Merluccius merluccius); the impact of censored catch information. – ICES Journal of Marine Science, 67: 258–269. Iberian hake assessment revealed an increase in fishing mortality (F) despite enforcement of a recovery plan. Recent landings exceeded the total allowable catch and discarding rates were high. Alternative management strategies based on F control were evaluated with respect to the probability of recovering spawning-stock biomass (SSB), expected profits, and robustness to uncertainty on catch information and stock dynamics. Results showed that the use of censored catch data, i.e. excluding the Gulf of Cádiz or discards, may lead to inappropriate conclusions. Reducing fishing mortality was necessary for SSB to recover. An Fmax strategy with discard reduction showed the highest probability of rebuilding SSB and led the fishery to sustainable exploitation, with an expected %SPR of 30–40% in 2025, mean individual weight in the landings of 450 g in 2015, and yield increasing by >20%. Because of uncertainty in the estimates of maximum sustainable yield, management strategies based on FMSY were least robust, but all strategies were robust to alternative stock–recruit models.
An investigation of the spawning behaviour of the chokka squid Loligo reynaudii and the potential effects of temperature using acoustic telemetry
Authors: Downey Nicola J. , Roberts Michael J. , Baird Dan
Published: October 2009

Downey, N. J., Roberts, M. J., and Baird, D. 2010. An investigation of the spawning behaviour of the chokka squid Loligo reynaudii and the potential effects of temperature using acoustic telemetry. – ICES Journal of Marine Science, 67: 231–243. Spawning aggregations of chokka squid are influenced by environmental conditions. Acoustic telemetry was used to monitor the behaviour of spawning squid in relation to environmental variability. During the November squid-fishery closed seasons of 2003–2006, hexagonal VR2 receiver arrays were moored on and around active spawning aggregations in Kromme Bay, South Africa. In all, 45 squid were tagged (V9P-6L-S256 transmitters) and released within these arrays. Three presence–absence behaviours were identified: (i) arrival on the spawning site at dawn and departure after dusk, (ii) continuous presence for a number of days, and (iii) presence interrupted by frequent but short periods of absence. Movement between spawning sites was both diurnal and nocturnal. Squid presence at the monitored sites increased after dawn and decreased towards and after dusk. Occasionally, a core aggregation of squid remained on the spawning sites at night. Temperature data at the sites indicated occasional upwelling, and although the role of temperature in the spawning process is not well understood, data suggest that it is linked to the continuation and or interruption of spawning after an aggregation has formed. The initial formation of spawning aggregations appears to be triggered by upwelling events.
The transient swimming of a waving sheet
Authors: Pak On Shun , Lauga Eric
Published: October 2009

Small-scale locomotion plays an important role in biology. Different modelling approaches have been proposed in the past. The simplest model is an infinite inextensible two-dimensional waving sheet, originally introduced by Taylor, which serves as an idealized geometrical model for both spermatozoa locomotion and ciliary transport in Stokes flow. Here, we complement classic steady-state calculations by deriving the transient low-Reynolds number swimming speed of such a waving sheet when starting from rest (small-amplitude initial-value problem). We also determine the transient fluid flow in the ‘pumping’ setup where the sheet is not free to move but instead generates a net fluid flow around it. The time scales for these two problems, which in general govern transient effects in transport and locomotion at low Reynolds numbers, are also derived using physical arguments.