bluuebunny/crossref_metadata_2025 huggingface dataset:
Nucleation of liquid droplets and voids in a stretched Lennard-Jones fcc crystal
Authors: Baidakov Vladimir G. , Tipeev Azat O.
Published: September 2015

The method of molecular dynamics simulation has been used to investigate the phase decay of a metastable Lennard-Jones face-centered cubic crystal at positive and negative pressures. It is shown that at high degrees of metastability, crystal decay proceeds through the spontaneous formation and growth of new-phase nuclei. It has been found that there exists a certain boundary temperature. Below this temperature, the crystal phase disintegrates as the result of formation of voids, and above, as a result of formation of liquid droplets. The boundary temperature corresponds to the temperature of cessation of a crystal–liquid phase equilibrium when the melting line comes in contact with the spinodal of the stretched liquid. The results of the simulations are interpreted in the framework of classical nucleation theory. The thermodynamics of phase transitions in solids has been examined with allowance for the elastic energy of stresses arising owing to the difference in the densities of the initial and the forming phases. As a result of the action of elastic forces, at negative pressures, the boundary of the limiting superheating (stretching) of a crystal approaches the spinodal, on which the isothermal bulk modulus of dilatation becomes equal to zero. At the boundary of the limiting superheating (stretching), the shape of liquid droplets and voids is close to the spherical one.
Nonlinear fractional Schrödinger equation on a half-line
Authors: Kaikina Elena I.
Published: September 2015

We study the initial-boundary value (IBV) problem for the nonlinear fractional Schrödinger equation ut+iuxx+iu2u+i∂x12u=0,t>0,x>0u(x,0)=u0(x),x>0,u(0,t)=h(t),t>0, where ∂x12u=12π∫0∞sign (x−y)x−yuy(y)dy. We prove the global in time existence of solutions of IBV problem for nonlinear fractional Schrödinger equation with inhomogeneous Dirichlet boundary conditions. Also, we are interested in the study of the asymptotic behavior of solutions.
Relaxation times and modes of disturbed aggregate distribution in micellar solutions with fusion and fission of micelles
Authors: Zakharov Anatoly I. , Adzhemyan Loran Ts. , Shchekin Alexander K.
Published: September 2015

We have performed direct numerical calculations of the kinetics of relaxation in the system of surfactant spherical micelles under joint action of the molecular mechanism with capture and emission of individual surfactant molecules by molecular aggregates and the mechanism of fusion and fission of the aggregates. As a basis, we have taken the difference equations of aggregation and fragmentation in the form of the generalized kinetic Smoluchowski equations for aggregate concentrations. The calculations have been made with using the droplet model of molecular surfactant aggregates and two modified Smoluchowski models for the coefficients of aggregate-monomer and aggregate-aggregate fusions which take into account the effects of the aggregate size and presence of hydrophobic spots on the aggregate surface. A full set of relaxation times and corresponding relaxation modes for nonequilibrium aggregate distribution in the aggregation number has been found. The dependencies of these relaxation times and modes on the total concentration of surfactant in the solution and the special parameter controlling the probability of fusion in collisions of micelles with other micelles have been studied.
Temperature-dependent optical measurements of the dominant recombination mechanisms in InAs/InAsSb type-2 superlattices
Authors: Aytac Y. , Olson B. V. , Kim J. K. , Shaner E. A. , Hawkins S. D. , Klem J. F. , Flatté M. E. , Boggess T. F.
Published: September 2015

Temperature-dependent measurements of carrier recombination rates using a time-resolved optical pump-probe technique are reported for mid-wave infrared InAs/InAs1−xSbx type-2 superlattices (T2SLs). By engineering the layer widths and alloy compositions, a 16 K band-gap of ∼235 ± 10 meV was achieved for five unintentionally and four intentionally doped T2SLs. Carrier lifetimes were determined by fitting lifetime models based on Shockley-Read-Hall (SRH), radiative, and Auger recombination processes to the temperature and excess carrier density dependent data. The minority carrier (MC), radiative, and Auger lifetimes were observed to generally increase with increasing antimony content and decreasing layer thickness for the unintentionally doped T2SLs. The MC lifetime is limited by SRH processes at temperatures below 200 K in the unintentionally doped T2SLs. The extracted SRH defect energy levels were found to be near mid-bandgap. Also, it is observed that the MC lifetime is limited by Auger recombination in the intentionally doped T2SLs with doping levels greater than n ∼ 1016 cm−3.
Codoping of zinc and tungsten for practical high-performance amorphous indium-based oxide thin film transistors
Authors: Kizu Takio , Mitoma Nobuhiko , Miyanaga Miki , Awata Hideaki , Nabatame Toshihide , Tsukagoshi Kazuhito
Published: September 2015

Using practical high-density sputtering targets, we investigated the effect of Zn and W codoping on the thermal stability of the amorphous film and the electrical characteristics in thin film transistors. zinc oxide is a potentially conductive component while W oxide is an oxygen vacancy suppressor in oxide films. The oxygen vacancy from In-O and Zn-O was suppressed by the W additive because of the high oxygen bond dissociation energy. With controlled codoping of W and Zn, we demonstrated a high mobility with a maximum mobility of 40 cm2/V s with good stability under a negative bias stress in InWZnO thin film transistors.
Neutron, fluorescence, and optical imaging: An in situ combination of complementary techniques
Authors: Wagner D. , Börgardts M. , Grünzweig C. , Lehmann E. , Müller T. J. J. , Egelhaaf S. U. , Hermes H. E.
Published: September 2015

An apparatus which enables the simultaneous combination of three complementary imaging techniques, optical imaging, fluorescence imaging, and neutron radiography, is presented. While each individual technique can provide information on certain aspects of the sample and their time evolution, a combination of the three techniques in one setup provides a more complete and consistent data set. The setup can be used in transmission and reflection modes and thus with optically transparent as well as opaque samples. Its capabilities are illustrated with two examples. A polymer hydrogel represents a transparent sample and the diffusion of fluorescent particles into and through this polymer matrix is followed. In reflection mode, the absorption of solvent by a nile red-functionalized mesoporous silica powder and the corresponding change in fluorescent signal are studied.
GeSe monolayer semiconductor with tunable direct band gap and small carrier effective mass
Authors: Hu Yonghong , Zhang Shengli , Sun Shaofa , Xie Meiqiu , Cai Bo , Zeng Haibo
Published: September 2015

Two dimensional materials, befitting nanoscale electronics, can benefit strain-tunable applications due to their ultrathin and flexible nature. Based on the first-principles calculations within the generalized gradient approximation, GeSe monolayer with a distorted NaCl-type structure is predicted. The GeSe monolayer is found to be a direct semiconductor with a band gap of (1.16 ± 0.13) eV against the bulk counterpart. The electronic responses of the GeSe monolayer to strain are found to be sensitive and anisotropic, and the transitions between direct and indirect band gap are repeatedly met in the course of energy engineering by uniaxial and biaxial strains. The direct band gap of the GeSe monolayer is tunable by small strain within a large energy range (0.95–1.48 eV). The carrier effective masses in the GeSe monolayer are also tunable by strain in a low mass range (0.03–0.61 m0). These intriguing properties make GeSe monolayer a promising two-dimensional material for nanomechanics, thermoelectrics, and optoelectronics.
Efficient neutron production from sub-nanosecond laser pulse accelerating deuterons on target front side
Authors: Klir D. , Krasa J. , Cikhardt J. , Dudzak R. , Krousky E. , Pfeifer M. , Rezac K. , Sila O. , Skala J. , Ullschmied J. , Velyhan A.
Published: September 2015

Neutron-producing experiments have been carried out on the Prague Asterix Laser System. At the fundamental wavelength of 1.315 μm, the laser pulse of a 600 J energy and 300 ps duration was focused on a thick deuterated-polyethylene target. Neutron yields reached (4.1 ± 0.8) × 108 at the peak intensity of ≈3 × 1016 W/cm2. A more detailed analysis of neutron time-of-flight signals showed that a significant fraction of neutron yields was produced both by the 2H(d,n)3He reaction and by other neutron-producing reactions. Neutron energies together with delayed neutron and gamma emission showed that MeV deuterons escaped from a laser-produced plasma and interacted ≈50 ns later with a borosilicate blast-shield glass. In order to increase DD neutron yields and to characterize deuteron beams via nuclear reactions, a secondary deuterated polyethylene target was used in a pitcher-catcher scheme at the target front side. In this experimental arrangement, the neutron yield reached (2.0 ± 0.5) × 109 with the peak neutron fluence of (2.5 ± 0.5) × 108 n/sr. From the neutron yield, it was calculated that the secondary target was bombarded by 2 × 1014 deuterons in the 0.5–2.0 MeV energy range. The neutron yield of 2 × 109 at the laser energy of 600 J implied the production efficiency of 3 × 106 n/J. A very important result is that the efficient neutron production was achieved with the low contrast, sub-nanosecond laser pulse of the intensity of 1016 W/cm2. The latter parameters can be achieved in a rep-rate mode more easily than ultra-high intensities and contrasts.
Elastic properties of nanopolycrystalline diamond: The nature of ultrahigh stiffness
Authors: Erohin S. V. , Sorokin P. B.
Published: September 2015

Recent experimental reports on the production of nanopolycrystalline diamond with outstanding mechanical stiffness highlight the importance of theoretical investigation of this unusual effect. Here, we provide the comprehensive theoretical investigation of such material. We traced the evolution of the nanopolycrystalline diamond stiffness characterized by bulk modulus with the grain size increasing up to 10 nm and found samples with bulk modulus higher than that of diamond. We studied nature of such specific behavior and proposed a mechanism of stiffening in nanopolycrystalline diamond which could explain reference experimental results.
Correlation between the band gap expansion and melting temperature depression of nanostructured semiconductors
Authors: Li Jianwei , Zhao Xinsheng , Liu Xinjuan , Zheng Xuejun , Yang Xuexian , Zhu Zhe
Published: September 2015

The band gap and melting temperature of a semiconductor are tunable with the size and shape of the specimen at the nanometer scale, and related mechanisms remain as yet unclear. In order to understand the common origin of the size and shape effect on these two seemingly irrelevant properties, we clarify, correlate, formulate, and quantify these two properties of GaAs, GaN, InP, and InN nanocrystals from the perspectives of bond order-length-strength correlation using the core-shell configuration. The consistency in the theoretical predictions, experimental observations, and numerical calculations verify that the broken-bond-induced local bond contraction and strength gain dictates the band gap expansion, while the atomic cohesive energy loss due to bond number reduction depresses the melting point. The fraction of the under-coordinated atoms in the skin shell quantitatively determines the shape and size dependency. The atomic under-coordination in the skin down to a depth of two atomic layers inducing a change in the local chemical bond is the common physical origin.
Electronic and magnetic properties of Si substituted Fe3Ge
Authors: Shanavas K. V. , McGuire Michael A. , Parker David S.
Published: September 2015

Using first principles calculations, we studied the effect of Si substitution in the hexagonal Fe3Ge. We find the low temperature magnetic anisotropy in this system to be planar and originating mostly from the spin-orbit coupling in Fe-d states. Reduction of the unitcell volume reduces the magnitude of in-plane magnetic anisotropy, eventually turning it positive which reorients the magnetic moments to the axial direction. Substituting Ge with the smaller Si ions also increases the anisotropy, potentially enhancing the region of stability of the axial magnetization, which is beneficial for magnetic applications such as permanent magnets. Our experimental measurements on samples of Fe3Ge1−xSix confirm these predictions and show that substitution of about 6% of the Ge with Si increases by approximately 35 K the temperature range over which anisotropy is uniaxial.
Multi-band terahertz active device with complementary metamaterial
Authors: Qiao Shen , Zhang Yaxin , Liang Shixiong , Sun Linlin , Sun Han , Xu Gaiqi , Zhao Yuncheng , Yang Ziqiang
Published: September 2015

We describe a multi-band terahertz-active device using a composite structure made of complementary metamaterial and doped silicon that can be dynamically controlled. This special complementary metamaterial exhibits three resonances that produce three pass-bands. The pass-bands can be uniformly manipulated by exploiting the photoinduced characteristics of the doped silicon. Simulations were performed to analyze the magnetic field and surface current distributions. The simulation results agree well with experimental results obtained from terahertz time-domain spectroscopy. Using an 808-nm-wavelength laser beam, a modulation depth of up to 80% was obtained. In numerical simulations, we used a conductivity mode to characterize photoinduction. The development of multi-band terahertz-active devices has many potential applications, for example, in filters, modulators, switches, and sensors.
Fabry-Perot resonances in a symmetric three layer structure
Authors: Ragulis Paulius , Matulis Algirdas , Kancleris Žilvinas
Published: September 2015

The transmission of the electromagnetic waves through the symmetric three layer structure has been investigated and it was shown that the resonant transmission (known as Fabry-Perot resonance) is a periodic function of the distance between the outside dielectric layers. We also showed that in the case of the symmetric structure the initial scattering problem can be reformulated into two reflection ones. This procedure applied to our three layer structure enabled us to obtain rather simple expressions for the description of the resonant frequencies that perfectly fit those obtained experimentally either in free space or in X band waveguide as well.
Three-terminal stand-alone superconducting terahertz emitter
Authors: Zhou Xianjing , Zhu Qiang , Ji Min , An Deyue , Hao Luyao , Sun Hancong , Ishida Shigeyuki , Rudau Fabian , Wieland Raphael , Li Jun , Koelle Dieter , Eisaki Hiroshi , Yoshida Yoshiyuki , Hatano Takeshi , Kleiner Reinhold , Wang Huabing , Wu Peiheng
Published: September 2015

We report on the electrothermal behavior and the terahertz emission properties of a stand-alone Bi2Sr2CaCu2O8 intrinsic Josephson junction stack contacted in a three-terminal configuration. One terminal is used as a collective ground while the other two, contacting the stack from its right and left side, allow to vary the current injection profile. At high bias, a hot spot forms in the stack. Its appearance and position can be controlled by varying the ratios of the injected currents. Depending on this ratio, the emitted power can vary by an order of magnitude. Further, for a given total injection current, the device allows to vary the emission frequency on a 10% level by altering the injection profile. The overall tunability of the emission frequency, varying also the total bias current, is on the order of 20%.
A bandgap-engineered HgCdTe PBπn long-wavelength infrared detector
Authors: Qiu W. C. , Jiang T. , Cheng X. A.
Published: September 2015

In this paper, the HgCdTe PBπn (π represents p-type absorption layer) long-wavelength infrared detector based on bandgap-engineering is designed and validated by the preliminary experiments. Numerical simulation was applied to calculate the current-voltage (I-V) characteristic and zero-bias resistance-area product (R0A) for PBπn detectors and traditional pn photodiodes. The results show that the performance of PBπn detector was significantly improved compared with that of conventional pn photodiodes. The design of PBπn barrier structure can essentially reduce the dark current, while significantly improving the responsivity. In addition, when reverse biased, optimized PBπn device can also suppress Auger processes in the absorption layer under the high temperature up to 215 K. The proposed HgCdTe long wavelength infrared detectors based on vertical PBπn structure pave the way for development of high performance and high operation temperature infrared sensor applications.
Gate length and temperature dependence of negative differential transconductance in silicon quantum well metal-oxide-semiconductor field-effect transistors
Authors: Naquin Clint , Lee Mark , Edwards Hal , Mathur Guru , Chatterjee Tathagata , Maggio Ken
Published: September 2015

Introducing quantum transport into silicon transistors in a manner compatible with industrial fabrication has the potential to transform the performance horizons of large scale integrated silicon devices and circuits. Explicit quantum transport as evidenced by negative differential transconductances (NDTCs) has been observed in a set of quantum well (QW) transistors fabricated using industrial silicon complementary metal-oxide-semiconductor processing. Detailed gate length and temperature dependence characteristics of the NDTCs in these devices have been measured. The QW potential was formed via lateral ion implantation doping on a commercial 45 nm technology node process line, and measurements of the transfer characteristics show NDTCs up to room temperature. Gate length dependence of NDTCs shows a correlation of the interface channel length with the number of NDTCs formed as well as with the gate voltage (VG) spacing between NDTCs. The VG spacing between multiple NDTCs suggests a quasi-parabolic QW potential profile. The temperature dependence is consistent with partial freeze-out of carrier concentration against a degenerately doped background.
Molecular simulations and lattice dynamics determination of Stillinger-Weber GaN thermal conductivity
Authors: Liang Zhi , Jain Ankit , McGaughey Alan J. H. , Keblinski Pawel
Published: September 2015

The bulk thermal conductivity of Stillinger-Weber (SW) wurtzite GaN in the [0001] direction at a temperature of 300 K is calculated using equilibrium molecular dynamics (EMD), non-equilibrium MD (NEMD), and lattice dynamics (LD) methods. While the NEMD method predicts a thermal conductivity of 166 ± 11 W/m·K, both the EMD and LD methods predict thermal conductivities that are an order of magnitude greater. We attribute the discrepancy to significant contributions to thermal conductivity from long-mean free path phonons. We propose that the Grüneisen parameter for low-frequency phonons is a good predictor of the severity of the size effects in NEMD thermal conductivity prediction. For weakly anharmonic crystals characterized by small Grüneisen parameters, accurate determination of thermal conductivity by NEMD is computationally impractical. The simulation results also indicate the GaN SW potential, which was originally developed for studying the atomic-level structure of dislocations, is not suitable for prediction of its thermal conductivity.
Manipulating the ferromagnetism in narrow-bandwidth Pr1-xCaxMnO3 (0 ≤ x ≤ 0.6) by means of the Mn-Ru t2g ferromagnetic super-exchanges
Authors: Wang Y. L. , Liu M. F. , Xie Y. L. , Yan Z. B. , Dong S. , Liu J.-M.
Published: September 2015

The concurrent ferromagnetic and metal-insulator transitions via the double-exchange route and electronic phase separation scenario represent the core ingredients of the physics of manganites. In this work, a Ca2+ and Ru4+ co-substitution of Pr3+ and Mn3+ in narrow-bandwidth and insulating PrMnO3, namely, Pr1-xCaxMn1-xRuxO3 (PCMRO, x ≤ 0.6), is carried out in order to investigate an alternative approach to effectively manipulate the ferromagnetism of PrMnO3-based manganites. It is revealed that PCMRO over the whole substitution range is homogeneous solid solution with increased lattice distortion. The preference of Ru4+ valence state and the absence of Mn4+ valence state disable the Mn3+-Mn4+ eg-orbital double-exchange, and the random occupation of Ru4+ in the lattice excludes the charge ordering and electronic phase separation. While all these consequences should favor antiferromagnetic insulating states, nevertheless, a high-temperature ferromagnetic transition is triggered by the co-substitution and the magnetization can reach up to ∼1.0 μB/f.u. at x ∼ 0.2–0.3, much bigger than the moment (<0.1 μB/f.u.) of Pr1−xCaxMnO3 in the weak ferromagnetic insulator state. It is suggested that this strong ferromagnetism is substantially ascribed to the Mn3+-Ru4+ t2g-orbital ferromagnetic super-exchange, and a simple geometric network illustration of the magnetism and electrical transport is presented.
Junction size dependence of ferroelectric properties in e-beam patterned BaTiO3 ferroelectric tunnel junctions
Authors: Singh A. V. , Althammer M. , Rott K. , Reiss G. , Gupta A.
Published: September 2015

We investigate the switching characteristics in BaTiO3-based ferroelectric tunnel junctions patterned in a capacitive geometry with circular Ru top electrode with diameters ranging from ∼430 to 2300 nm. Two different patterning schemes, viz., lift-off and ion-milling, have been employed to examine the variations in the ferroelectric polarization, switching, and tunnel electro-resistance resulting from differences in the pattering processes. The values of polarization switching field are measured and compared for junctions of different diameter in the samples fabricated using both patterning schemes. We do not find any specific dependence of polarization switching bias on the size of junctions in both sample stacks. The junctions in the ion-milled sample show up to three orders of resistance change by polarization switching and the polarization retention is found to improve with increasing junction diameter. However, similar switching is absent in the lift-off sample, highlighting the effect of patterning scheme on the polarization retention.
Correlation between laser absorption and radiation conversion efficiency in laser produced tin plasma
Authors: Matsukuma Hiraku , Sunahara Atsushi , Yanagida Tatsuya , Tomuro Hiroaki , Kouge Kouichiro , Kodama Takeshi , Hosoda Tatsuya , Fujioka Shinsuke , Nishimura Hiroaki
Published: September 2015

The correlation between the laser absorption and the conversion efficiency (CE) for 13.5 nm extreme ultraviolet (EUV) light in a laser-produced tin plasma was investigated. The absorption rate α and the CE were measured simultaneously for a laser-pre-formed low-density tin target as a function of the time delay between the pre-pulse and the main laser pulse. A clear and positive correlation between α and CE was found with increasing delay time; however, the CE decreases rapidly at longer delay times. This result is partly attributed to a reduction in the absorption rate, but is mainly attributed to the self-absorption of EUV light in excessively long-scale plasmas.
Magneto-optic transmittance modulation observed in a hybrid graphene–split ring resonator terahertz metasurface
Authors: Zanotto Simone , Lange Christoph , Maag Thomas , Pitanti Alessandro , Miseikis Vaidotas , Coletti Camilla , Degl'Innocenti Riccardo , Baldacci Lorenzo , Huber Rupert , Tredicucci Alessandro
Published: September 2015

By placing a material in close vicinity of a resonant optical element, its intrinsic optical response can be tuned, possibly to a wide extent. Here, we show that a graphene monolayer, spaced a few tenths of nanometers from a split ring resonator metasurface, exhibits a magneto-optical response which is strongly influenced by the presence of the metasurface itself. This hybrid system holds promises in view of thin optical modulators, polarization rotators, and nonreciprocal devices, in the technologically relevant terahertz spectral range. Moreover, it could be chosen as the playground for investigating the cavity electrodynamics of Dirac fermions in the quantum regime.
Dynamic microscale temperature gradient in a gold nanorod solution measured by diffraction-limited nanothermometry
Authors: Li Chengmingyue , Gan Xiaosong , Li Xiangping , Gu Min
Published: September 2015

We quantify the dynamic microscale temperature gradient in a gold nanorod solution using quantum-dot-based microscopic fluorescence nanothermometry. By incorporating CdSe quantum dots into the solution as a nanothermometer, precise temperature mapping with diffraction-limited spatial resolution and sub-degree temperature resolution is achieved. The acquired data on heat generation and dissipation show an excellent agreement with theoretical simulations. This work reveals an effective approach for noninvasive temperature regulation with localized nanoheaters in microfluidic environment.
Polarization-induced resistive switching behaviors in complex oxide heterostructures
Authors: Wu Lei , Zhang Chao , Dong Chunhui , Jia Chenglong , Jiang Changjun , Xue Desheng
Published: September 2015

Complex oxide heterostructures are fabricated by growing La0.67Ca0.33MnO3 films on ferroelectric 0.71Pb(Mg1/3Nb2/3)O3-0.29PbTiO3 (011) single-crystal substrates. The nonvolatile or pulsed resistive switching behaviors induced by an electric field are achieved simultaneously. Further analyses indicate that the different resistive switching behaviors are resulted from co-control of piezostrain and polarization current effects. With decreasing in-plane read current from 0.1 mA to 0.001 mA, the polarization current effect gradually begins to play a more important role than the piezostrain effect. Consequently, the nonvolatile resistive switching behavior is converted to pulse resistive switching behavior. The results further enhance the application of complex oxides in multifunctional memory devices.
Lowering of the cavitation threshold in aqueous suspensions of porous silicon nanoparticles for sonodynamic therapy applications
Authors: Sviridov A. P. , Osminkina L. A. , Nikolaev A. L. , Kudryavtsev A. A. , Vasiliev A. N. , Timoshenko V. Yu.
Published: September 2015

A significant decrease of the cavitation threshold in aqueous suspensions of porous silicon nanoparticles (PSi NPs) with sizes about 100 nm as compared with pure water was observed for ultrasound irradiation (USI) with therapeutic frequency (0.88 MHz) and intensities (about 1 W/cm2). This effect is explained by porous morphology of PSi NPs, which promotes the nucleation of cavitation bubbles. In vitro experiments revealed a suppression of the proliferation of cancer cells with the introduced PSi NPs after exposure to USI related to the enhanced cavitation processes, which led to the cell destruction. The obtained results demonstrate that PSi NPs are prospective for applications as sonosensitizers in mild cancer therapy.
Localized tip enhanced Raman spectroscopic study of impurity incorporated single GaN nanowire in the sub-diffraction limit
Authors: Patsha Avinash , Dhara Sandip , Tyagi A. K.
Published: September 2015

The localized effect of impurities in single GaN nanowires in the sub-diffraction limit is reported using the study of lattice vibrational modes in the evanescent field of Au nanoparticle assisted tip enhanced Raman spectroscopy (TERS). GaN nanowires with the O impurity and the Mg dopants were grown by the chemical vapor deposition technique in the catalyst assisted vapor-liquid-solid process. Symmetry allowed Raman modes of wurtzite GaN are observed for undoped and doped nanowires. Unusually very strong intensity of the non-zone center zone boundary mode is observed for the TERS studies of both the undoped and the Mg doped GaN single nanowires. Surface optical mode of A1 symmetry is also observed for both the undoped and the Mg doped GaN samples. A strong coupling of longitudinal optical (LO) phonons with free electrons, however, is reported only in the O rich single nanowires with the asymmetric A1(LO) mode. Study of the local vibration mode shows the presence of Mg as dopant in the single GaN nanowires.
The influence of interlayer exchange coupling in giant-magnetoresistive devices on spin diode effect in wide frequency range
Authors: Ziętek Sławomir , Ogrodnik Piotr , Skowroński Witold , Wiśniowski Piotr , Czapkiewicz Maciej , Stobiecki Tomasz , Barnaś Józef
Published: September 2015

Spin diode effect in a giant magnetoresistive strip is measured in a broad frequency range, including resonance and off-resonance frequencies. The off-resonance dc signal is relatively strong and also significantly dependent on the exchange coupling between magnetic films through the spacer layer. The measured dc signal is described theoretically by taking into account magnetic dynamics induced by Oersted field created by an ac current flowing through the system.
Reduction of effective terahertz focal spot size by means of nested concentric parabolic reflectors
Authors: Neumann V. A. , Laurita N. J. , Pan LiDong , Armitage N. P.
Published: September 2015

An ongoing limitation of terahertz spectroscopy is that the technique is generally limited to the study of relatively large samples of order 4 mm across due to the generally large size of the focal beam spot. We present a nested concentric parabolic reflector design which can reduce the terahertz focal spot size. This parabolic reflector design takes advantage of the feature that reflected rays experience a relative time delay which is the same for all paths. The increase in effective optical path for reflected light is equivalent to the aperture diameter itself. We have shown that the light throughput of an aperture of 2 mm can be increased by a factor 15 as compared to a regular aperture of the same size at low frequencies. This technique can potentially be used to reduce the focal spot size in terahertz spectroscopy and enable the study of smaller samples.
Structural, dielectric and magnetic properties of nickel substituted cobalt ferrite nanoparticles: Effect of nickel concentration
Authors: Velhal Ninad B. , Patil Narayan D. , Shelke Abhijeet R. , Deshpande Nishad G. , Puri Vijaya R.
Published: September 2015

Nickel substituted cobalt ferrite nanoparticles with composition Co1−xNixFe2O4 (0.0 ≤ x ≤ 1.0) was synthesized using simple, low temperature auto combustion method. The X-ray diffraction patterns reveal the formation of cubic phase spinel structure. The crystallite size varies from 30-44 nm with the nickel content. Porous and agglomerated morphology of the bulk sample was displayed in the scanning electron microscopy. Micro Raman spectroscopy reveals continuous shift of Eg and Eg(2) stokes line up to 0.8 Ni substitution. The dispersion behavior of the dielectric constant with frequency and the semicircle nature of the impedance spectra show the cobalt nickel ferrite to have high resistance. The ferromagnetic nature is observed in all the samples, however, the maximum saturation magnetization was achieved by the 0.4 Ni substituted cobalt ferrite, which is up to the 92.87 emu/gm at 30K.
Control over overall shape and size in de novo designed proteins
Authors: Lin Yu-Ru , Koga Nobuyasu , Tatsumi-Koga Rie , Liu Gaohua , Clouser Amanda F. , Montelione Gaetano T. , Baker David
Published: September 2015

Significance

We describe how protein size and shape can be sculpted by de novo protein design. Precise control over protein shape will be critical for completely de novo design of high-affinity binding proteins, enzymes, and protein-based nanomaterials. The systematic procedure for design of αβ-protein structures from scratch described in this paper should be broadly useful.
RodZ links MreB to cell wall synthesis to mediate MreB rotation and robust morphogenesis
Authors: Morgenstein Randy M. , Bratton Benjamin P. , Nguyen Jeffrey P. , Ouzounov Nikolay , Shaevitz Joshua W. , Gitai Zemer
Published: September 2015

Significance

The bacterial actin homolog, MreB, is a key determinant of rod-cell shape but the mechanism by which it functions has remained a topic of much debate. Recently it was shown that MreB exists as small polymers that actively rotate around the cell circumference. This rotation is widely conserved, yet its mechanism and function have remained unknown. Here we show that MreB rotates because cytoplasmic MreB filaments are coupled to periplasmic cell wall synthesis through the transmembrane protein RodZ, which acts as a transmembrane linker. Furthermore, by genetically uncoupling MreB rotation from growth we establish MreB rotation acts as a robustness mechanism for rod-like shape determination. This work thus explains the mystery of MreB rotation and suggests a new model for bacterial cell shape maintenance.
Estimating Cohort Survival through Tributaries for Salmonid Populations with Variable Ages at Migration
Authors: Buchanan Rebecca A. , Skalski John R. , Mackey Gregory , Snow Charles , Murdoch Andrew R.
Published: September 2015

Survival of juvenile anadromous Pacific salmonids from their earliest age of seaward movement (“out-migration”) through the tributaries that connect their rearing grounds to larger-order rivers (“cohort survival”) is an important yet often unmonitored factor in the complex life history of these species. Populations with variable age at out-migration (e.g., steelhead Oncorhynchus mykiss) or multiple juvenile rearing strategies (e.g., Chinook Salmon O. tshawytscha) raise particular challenges in survival monitoring. A multiple-state release–recapture model is presented to estimate cohort survival for salmonid species with variable age at out-migration and demonstrated in two case studies. Annual releases of fish tagged with passive integrated transponder (PIT) tags from the same brood year (cohort) and their detections by instream PIT-tag detection arrays in tributaries and at hydroelectric dams are used to estimate survival through tributaries and the age composition of juvenile migrants reaching downstream sites. The 2010 cohort of Chinook Salmon from the Chiwawa River in Washington State had estimated survival of 0.59 to the middle Wenatchee River array in Tumwater Dam Reservoir (river distance of 30 km) and 0.12 to McNary Dam (364 km) on the Columbia River. The age composition shifted from 60.1% subyearlings at the Wenatchee River array to 100% yearlings at McNary Dam, reflecting the use of the Wenatchee River as a nonnatal rearing area, whereas McNary Dam is in the migratory corridor. The 2010 cohort of steelhead from the Twisp River in Washington State had estimated survival from the yearling stage of 0.30 to Rocky Reach Dam (146 km from the Twisp River mouth) on the Columbia River and 0.17 to McNary Dam (439 km). The low survival to the Columbia River resulted from both mortality and adoption of a resident life history and reflects the diverse population structure in the Twisp River.

Received February 4, 2015; accepted June 11, 2015
Invisible disasters: the effects of Israeli occupation on Palestinian gender roles
Authors: Dana Karam , Walker Hannah
Published: September 2015

Women’s participation in the First Intifada allowed for increased gender equality in Palestine. However, the weakness of the Palestinian Authority, established by the signing of the Oslo Accords, created space for non-state organizations like Hamas to gain a foothold in Palestine. Likewise, during the post-Oslo period conservative positions on gender resurged. This paper re-examines the structural factors that facilitated increased gender inequality and argues that the nature of the occupation itself serves as the greatest force for gender inequality in Palestine. To develop and test our theory, we draw on original, large-n survey data and in-depth interviews.
Visuospatial Ability as a Predictor of Novice Performance in Ultrasound-guided Regional Anesthesia
Authors: Shafqat Atif , Ferguson Eamonn , Thanawala Vishal , Bedforth Nigel M. , Hardman Jonathan G. , McCahon Robert A.
Published: September 2015

AbstractAbstract

Visuospatial testing predicts novice performance in performing ultrasound-guided needle placement on a benchtop model, and anxiety adversely affects performance. These factors may prove useful in creating tailored training of ultrasound-guided regional anesthesia designed to meet individual learner’s needs.

Background

Visuospatial ability correlates positively with novice performance of simple laparoscopic tasks. The aims of this study were to identify whether visuospatial ability could predict technical performance of an ultrasound-guided needle task by novice operators and to describe how emotional state, intelligence, and fear of failure impact on this.

Methods

Sixty medical student volunteers enrolled in this observational study. The authors used an instructional video to standardize training for ultrasound-guided needle advancement in a turkey breast model and assessed volunteers’ performance independently by two assessors using composite error score (CES) and global rating scale (GRS). The authors assessed their “visuospatial ability” with mental rotation test (MRT), group embedded figures test, and Alice Heim group ability test. Emotional state was judged with UWIST Mood Adjective Checklist (UMACL), and fear of failure and general cognitive ability were judged with numerical reasoning test.

Results

High CES scores (high error rate) were associated with low MRT scores (ρ = −0.54; P < 0.001). Better GRS scores were associated with better MRT scores (ρ = 0.47; P < 0.001). Regarding emotions, GRS scores were low when anxiety levels were high (ρ = −0.35; P = 0.005) and CES scores (errors) were low when individuals reported feeling vigorous and active (ρ = −0.30; P = 0.01).

Conclusions

An MRT predicts novice performance of an ultrasound-guided needling task on a turkey model and as a trait measure could be used as a tool to focus training resources on less-able individuals. Anxiety adversely affects performance. Therefore, both may prove useful in directing targeted training in ultrasound-guided regional anesthesia.
Cardiac Output and Cerebral Blood Flow
Authors: Meng Lingzhong , Hou Wugang , Chui Jason , Han Ruquan , Gelb Adrian W.
Published: September 2015

AbstractAbstract

Cerebral blood flow (CBF) is rigorously regulated by various powerful mechanisms to safeguard the match between cerebral metabolic demand and supply. The question of how a change in cardiac output (CO) affects CBF is fundamental, because CBF is dependent on constantly receiving a significant proportion of CO. The authors reviewed the studies that investigated the association between CO and CBF in healthy volunteers and patients with chronic heart failure. The overall evidence shows that an alteration in CO, either acutely or chronically, leads to a change in CBF that is independent of other CBF-regulating parameters including blood pressure and carbon dioxide. However, studies on the association between CO and CBF in patients with varying neurologic, medical, and surgical conditions were confounded by methodologic limitations. Given that CBF regulation is multifactorial but the various processes must exert their effects on the cerebral circulation simultaneously, the authors propose a conceptual framework that integrates the various CBF-regulating processes at the level of cerebral arteries/arterioles while still maintaining autoregulation. The clinical implications pertinent to the effect of CO on CBF are discussed. Outcome research relating to the management of CO and CBF in high-risk patients or during high-risk surgeries is needed.

Cardiac output causally affects cerebral blood flow. A conceptualization is proposed for the purpose of integrating at the level of cerebral resistance vessel various mechanisms that regulate the cerebral circulation and jointly determine the brain perfusion.
Cost-Effectiveness of Cetuximab as First-line Treatment for Metastatic Colorectal Cancer in the United States
Authors: Shankaran Veena , Ortendahl Jesse D. , Purdum Anna G. , Bolinder Bjorn , Anene Ayanna M. , Sun Gordon H. , Bentley Tanya G.K.
Published: September 2015

Purpose:

We conducted a cost-effectiveness analysis incorporating recent phase III clinical trial (FIRE-3) data to evaluate clinical and economic tradeoffs associated with first-line treatments of KRAS wild-type (WT) metastatic colorectal cancer (mCRC).

Materials and Methods:

A cost-effectiveness model was developed using FIRE-3 data to project survival and lifetime costs of FOLFIRI plus either cetuximab or bevacizumab. Hypothetical KRAS-WT mCRC patients initiated first-line treatment and could experience adverse events, disease progression warranting second-line treatment, or clinical response and hepatic metastasectomy. Model inputs were derived from FIRE-3 and published literature. Incremental cost-effectiveness ratios (ICERs) were reported as US$ per life year (LY) and quality-adjusted life year (QALY). Scenario analyses considered patients with extended RAS mutations and CALGB/SWOG 80405 data; 1-way and probabilistic sensitivity analyses were conducted.

Results:

Compared with bevacizumab, KRAS-WT patients receiving first-line cetuximab gained 5.7 months of life at a cost of $46,266, for an ICER of $97,223/LY ($122,610/QALY). For extended RAS-WT patients, the ICER was $77,339/LY ($99,584/QALY). Cetuximab treatment was cost-effective 80.3% of the time, given a willingness-to-pay threshold of $150,000/LY. Results were sensitive to changes in survival, treatment duration, and product costs.

Conclusions:

Our analysis of FIRE-3 data suggests that first-line treatment with cetuximab and FOLFIRI in KRAS (and extended RAS) WT mCRC patients may improve health outcomes and use financial resources more efficiently than bevacizumab and FOLFIRI. This information, in combination with other studies investigating comparative effectiveness of first-line options, can be useful to clinicians, payers, and policymakers in making treatment and resource allocation decisions for mCRC patients.
Impact of Roux-en-Y Gastric Bypass Surgery on Pharmacokinetics of Administered Drugs: Implications and Perspectives
Authors: Srinivas Nuggehally R.
Published: September 2015

Obesity epidemic has grown out of proportion with increased heath cost because of comorbidity associated with obesity. Due to mediocre benefit from pharmacological interventions, bariatric surgery popularly known as Roux-en-Y gastric bypass (RYGB) surgery has been increasingly practiced. Although RYGB significantly reduces body mass index, it also alters the local gut environment leading to significant changes in the drug absorption and bioavailability. The focus of the review is to present and critically evaluate case studies pertaining to pharmacokinetic data gathered till date on subjects after RYGB. A large portion of the reviewed examples showed reduced area under the concentration versus time curve [area under curve (AUC)] of drugs after RYGB (44%), whereas equal number of investigations showed increased (26%) or unaltered AUC (26%) after RYGB. There was one instance (4%), where the AUC was highly variable and individual subject dependent. Examination of drugs that showed reduced bioavailability suggested that a complex interplay of various factors such as solubility, permeability, metabolic enzymes, and transporters may have contributed for the observed effect. The increased bioavailability seemed to be related to permeability enhancement and generally in drug classes that have reduced metabolism. Based on the review, there is a significant risk of therapy failure for certain drugs because of subtherapeutic plasma levels. The need to readjust doses immediately after RYGB may be considered based on the therapeutic drug monitoring (TDM) findings. It seems prudent to initiate TDM for certain disease areas or drug classes until stable doses are established after RYGB through the appropriate pharmacokinetic and/or pharmacodynamics surrogate, as appropriate.
Contests with deadly weapons: telson sparring in mantis shrimp (Stomatopoda)
Authors: Green P. A. , Patek S. N.
Published: September 2015

Mantis shrimp strike with extreme impact forces that are deadly to prey. They also strike conspecifics during territorial contests, yet theoretical and empirical findings in aggressive behaviour research suggest competitors should resolve conflicts using signals before escalating to dangerous combat. We tested how
Neogonodactylus bredini
uses two ritualized behaviours to resolve size-matched contests: meral spread visual displays and telson (tailplate) strikes. We predicted that (i) most contests would be resolved by meral spreads, (ii) meral spreads would reliably signal strike force and (iii) strike force would predict contest success. The results were unexpected for each prediction. Contests were not resolved by meral spreads, instead escalating to striking in 33 of 34 experiments. The size of meral spread components did not strongly correlate with strike force. Strike force did not predict contest success; instead, winners delivered more strikes. Size-matched
N. bredini
avoid deadly combat not by visual displays, but by ritualistically and repeatedly striking each other's telsons until the loser retreats. We term this behaviour ‘telson sparring', analogous to sparring in other weapon systems. We present an alternative framework for mantis shrimp contests in which the fight itself is the signal, serving as a non-lethal indicator of aggressive persistence or endurance.
Relationships within Cladobranchia (Gastropoda: Nudibranchia) based on RNA-Seq data: an initial investigation
Authors: Goodheart Jessica A. , Bazinet Adam L. , Collins Allen G. , Cummings Michael P.
Published: September 2015

Cladobranchia (Gastropoda: Nudibranchia) is a diverse (approx. 1000 species) but understudied group of sea slug molluscs. In order to fully comprehend the diversity of nudibranchs and the evolution of character traits within Cladobranchia, a solid understanding of evolutionary relationships is necessary. To date, only two direct attempts have been made to understand the evolutionary relationships within Cladobranchia, neither of which resulted in well-supported phylogenetic hypotheses. In addition to these studies, several others have addressed some of the relationships within this clade while investigating the evolutionary history of more inclusive groups (Nudibranchia and Euthyneura). However, all of the resulting phylogenetic hypotheses contain conflicting topologies within Cladobranchia. In this study, we address some of these long-standing issues regarding the evolutionary history of Cladobranchia using RNA-Seq data (transcriptomes). We sequenced 16 transcriptomes and combined these with four transcriptomes from the NCBI Sequence Read Archive. Transcript assembly using Trinity and orthology determination using H
a
MS
t
R yielded 839 orthologous groups for analysis. These data provide a well-supported and almost fully resolved phylogenetic hypothesis for Cladobranchia. Our results support the monophyly of Cladobranchia and the sub-clade Aeolidida, but reject the monophyly of Dendronotida.