bluuebunny/crossref_metadata_2025 huggingface dataset:
Theoretical study of photodetachment processes of anionic boron cluster. III. ${\rm B}_7^-$B7−
Authors: Reddy S. Rajagopala , Mahapatra S.
Published: February 2014

Photodetachment spectroscopy of \documentclass[12pt]{minimal}\begin{document}$B_7^{-}$\end{document}B7− is theoretically studied in this paper. Calculated photodetachment bands are compared with the available experimental results and assigned to the vibronic structure of the electronic ground and excited states of the neutral B7 cluster. The complex structure of photodetachment bands is found to arise from many stable isomers of \documentclass[12pt]{minimal}\begin{document}$B_7^{-}$\end{document}B7− of different symmetry point group. In this study we focus on three most stable isomers of \documentclass[12pt]{minimal}\begin{document}$B_7^{-}$\end{document}B7− and examine their photodetachment bands. Extensive quantum chemistry calculations are carried out to establish the potential energy surfaces and the coupling surfaces of the electronic states of neutral B7 originating from each of the three isomers. A diabatic electronic ansatz is employed and the nuclear dynamics is studied both by time-independent and time-dependent quantum mechanical methods. Both agreements and discrepancies of the theoretical results with the experimental findings are discussed.
The low temperature magnetostructural transition in Pr0.50Sr0.50CoO3: Bulk versus thin film behavior
Authors: Padilla-Pantoja J. , Herrero-Martín J. , Torrelles X. , Bozzo B. , Blasco J. , Ritter C. , García-Muñoz J. L.
Published: February 2014

We present a comparative study of the magnetic transitions in metallic Pr0.50Sr0.50CoO3 (PSCO) perovskites prepared in polycrystalline and thin film forms. As the bulk system, the strained epitaxial PSCO (010) film grown on LAO (100) is metallic in all the temperature range, with a ferromagnetic transition at 225 K, close to Tc ∼ 235 K in the ceramic PSCO specimen. Unlike the bulk system, the PSCO film does not show the second magnetic transition on cooling. In the ceramic sample, the second magnetic transition is coupled to an orthorhombic-to-monoclinic symmetry change. There is a contraction of the average ⟨Pr-O⟩ bond distance in the monoclinic phase below Ta, but the ⟨Co-O⟩ bond length is not modified across the transition. The orthorhombic to monoclinic structural transition stabilizes four short Pr-O2 bonds to basal oxygens in CoO6 octahedra. A strong hybridization of Pr 4f and O 2p orbitals in these bonds can be activated at Ta and probably assist the magnetostructural transition.
A general methodology for inverse estimation of the elastic and anelastic properties of anisotropic open-cell porous materials—with application to a melamine foam
Authors: Cuenca Jacques , Van der Kelen Christophe , Göransson Peter
Published: February 2014

This paper proposes an inverse estimation method for the characterisation of the elastic and anelastic properties of the frame of anisotropic open-cell foams used for sound absorption. A model of viscoelasticity based on a fractional differential constitutive equation is used, leading to an augmented Hooke's law in the frequency domain, where the elastic and anelastic phenomena appear as distinctive terms in the stiffness matrix. The parameters of the model are nine orthotropic elastic moduli, three angles of orientation of the material principal directions and three parameters governing the anelastic frequency dependence. The inverse estimation consists in numerically fitting the model on a set of transfer functions extracted from a sample of material. The setup uses a seismic-mass measurement repeated in the three directions of space and is placed in a vacuum chamber in order to remove the air from the pores of the sample. The method allows to reconstruct the full frequency-dependent complex stiffness matrix of the frame of an anisotropic open-cell foam and in particular it provides the frequency of maximum energy dissipation by viscoelastic effects. The characterisation of a melamine foam sample is performed and the relation between the fractional-derivative model and other types of parameterisations of the augmented Hooke's law is discussed.
Observation of separate cation and anion electrophoretic mobilities in pure ionic liquids
Authors: Zhang Zhiyang , Madsen Louis A.
Published: February 2014

Ionic liquids (ILs) continue to show relevance in many fields, from battery electrolytes, to carbon capture, to advanced separations. These highly ion-dense fluids present unique challenges in understanding their electrochemical properties due to deviations in behavior from existing electrolyte theories. Here we present a novel characterization of ILs using electrophoretic NMR (ENMR) to determine separate cation and anion mobilities. This method uses an applied electric field coincident with a pulsed magnetic field gradient to encode the E-field driven flow into NMR signals for cations (1H) and anions (19F). We describe the detailed design of these experiments, including quantitative analysis of artifact mitigation and necessary control experiments. We then explore mobilities and diffusion coefficients for two representative ILs: 1-ethyl-3-methyl imidazolium tetrafluoroborate ([C2mim][BF4]) and 1-ethyl-3-methyl imidazolium trifluoromethanesulfonate ([C2mim][TfO]). We further use the individual ion mobilities to calculate the bulk net conductivity, which closely agrees with bulk conductivity measurements obtained using impedance spectroscopy. These observations represent the first reliable measurements of cation and anion mobilities in pure ILs, with errors of ±7%. We discuss this advanced experimental methodology in detail, as well as implications of these sensitive measurements for understanding conduction mechanisms in ion-dense electrolytes.
Interplay between chain stiffness and excluded volume of semiflexible polymers confined in nanochannels
Authors: Muralidhar Abhiram , Tree Douglas R. , Wang Yanwei , Dorfman Kevin D.
Published: February 2014

The properties of channel-confined semiflexible polymers are determined by a complicated interplay of chain stiffness and excluded volume effects. Using Pruned-Enriched Rosenbluth Method (PERM) simulations, we study the equilibrium properties of channel-confined polymers by systematically controlling chain stiffness and excluded volume. Our calculations of chain extension and confinement free energy for freely jointed chains with and without excluded volume show excellent agreement with theoretical predictions. For ideal wormlike chains, the extension is seen to crossover from Odijk behavior in strong confinement to zero-stretching, bulk-like behavior in weak confinement. In contrast, for self-avoiding wormlike chains, we always observe that the linear scaling of the extension with the contour length is valid in the long-chain limit irrespective of the regime of confinement, owing to the coexistence of stiffness and excluded volume effects. We further propose that the long-chain limit for the extension corresponds to chain lengths wherein the projection of the end-to-end distance along the axis of the channel is nearly equal to the mean span parallel to the axis. For DNA in nanochannels, this limit was identified using PERM simulations out to molecular weights of more than 1 megabase pairs; the molecular weight of λ-DNA is found to exhibit nearly asymptotic fractional extension for channels sizes used commonly in experiments.
Line interference effects using a refined Robert-Bonamy formalism: The test case of the isotropic Raman spectra of autoperturbed N2
Authors: Boulet Christian , Ma Qiancheng , Thibault Franck
Published: February 2014

A symmetrized version of the recently developed refined Robert-Bonamy formalism [Q. Ma, C. Boulet, and R. H. Tipping, J. Chem. Phys. 139, 034305 (2013)] is proposed. This model takes into account line coupling effects and hence allows the calculation of the off-diagonal elements of the relaxation matrix, without neglecting the rotational structure of the perturbing molecule. The formalism is applied to the isotropic Raman spectra of autoperturbed N2 for which a benchmark quantum relaxation matrix has recently been proposed. The consequences of the classical path approximation are carefully analyzed. Methods correcting for effects of inelasticity are considered. While in the right direction, these corrections appear to be too crude to provide off diagonal elements which would yield, via the sum rule, diagonal elements in good agreement with the quantum results. In order to overcome this difficulty, a re-normalization procedure is applied, which ensures that the off-diagonal elements do lead to the exact quantum diagonal elements. The agreement between the (re-normalized) semi-classical and quantum relaxation matrices is excellent, at least for the Raman spectra of N2, opening the way to the analysis of more complex molecular systems.
Lattice Boltzmann simulations of a pitch-up and pitch-down maneuver of a chord-wise flexible wing in a free stream flow
Authors: Qi Dewei , He Guowei , Liu Yingming
Published: February 2014

A rapid pitch-up and pitch-down maneuver of a chord-wise flexible wing in a steady free stream is studied by using a lattice Boltzmann flexible particle method in a three-dimensional space at a chord based Reynolds number of 100. The pitching rates, flexibility, and wing density are systematically varied, and their effects on aerodynamic forces are investigated. It is demonstrated that the flexibility can be utilized to significantly improve lift forces. The flexible wing has a larger angular momentum due to elasticity and inertia and generates a larger leading edge vortex as compared with a rigid wing. Such lift enhancement occurs mainly during the pitch-down motion while a large stall angle is produced during the pitch-up motion. At a low pitch rate, the flexibility cannot improve lift.
Finite-element optimisation of electrocaloric multilayer capacitors
Authors: Crossley S. , McGinnigle J. R. , Kar-Narayan S. , Mathur N. D.
Published: February 2014

We used finite element analysis to model the flow of heat in multilayer capacitors (MLCs) that comprise good electrocaloric materials and high-thermal-conductivity electrodes. An ideal heat pump based on these MLCs could develop a sustained cooling power of 81.7 kW m−2. This supersedes the 36 kW m−2 predicted by a lumped thermal model [S. Kar-Narayan and N. D. Mathur, Appl. Phys. Lett. 95, 242903 (2009)]. We show that geometrical optimization increases predicted cooling power to 215 kW m−2.
Calculation of absorption spectra involving multiple excited states: Approximate methods based on the mixed quantum classical Liouville equation
Authors: Bai Shuming , Xie Weiwei , Zhu Lili , Shi Qiang
Published: February 2014

We investigate the calculation of absorption spectra based on the mixed quantum classical Liouville equation (MQCL) methods. It has been shown previously that, for a single excited state, the averaged classical dynamics approach to calculate the linear and nonlinear spectroscopy can be derived using the MQCL formalism. This work focuses on problems involving multiple coupled excited state surfaces, such as in molecular aggregates and in the cases of coupled electronic states. A new equation of motion to calculate the dipole-dipole correlation functions within the MQCL formalism is first presented. Two approximate methods are then proposed to solve the resulted equations of motion. The first approximation results in a mean field approach, where the nuclear dynamics is governed by averaged forces depending on the instantaneous electronic states. A modification to the mean field approach based on first order moment expansion is also proposed. Numerical examples including calculation of the absorption spectra of Frenkel exciton models of molecular aggregates, and the pyrazine molecule are presented.
Effects of reactant rotation on the dynamics of the OH + CH4 → H2O + CH3 reaction: A six-dimensional study
Authors: Song Hongwei , Li Jun , Jiang Bin , Yang Minghui , Lu Yunpeng , Guo Hua
Published: February 2014

The dynamics of the hydrogen abstraction reaction between methane and hydroxyl radical is investigated using an initial state selected time-dependent wave packet method within a six-dimensional model. The ab initio calibrated global potential energy surface of Espinosa-García and Corchado was used. Integral cross sections from several low-lying rotational states of both reactants have been obtained using the centrifugal sudden and J-shifting approximations. On the empirical potential energy surface, the rotational excitation of methane has little effect on the reaction cross section, but excited rotational states of OH inhibit the reactivity slightly. These results are rationalized with the newly proposed sudden vector projection model.
CO2 isolated line shapes by classical molecular dynamics simulations: Influence of the intermolecular potential and comparison with new measurements
Authors: Larcher G. , Tran H. , Schwell M. , Chelin P. , Landsheere X. , Hartmann J.-M. , Hu S.-M.
Published: February 2014

Room temperature absorption spectra of various transitions of pure CO2 have been measured in a broad pressure range using a tunable diode-laser and a cavity ring-down spectrometer, respectively, in the 1.6 μm and 0.8 μm regions. Their spectral shapes have been calculated by requantized classical molecular dynamics simulations. From the time-dependent auto-correlation function of the molecular dipole, including Doppler and collisional effects, spectral shapes are directly computed without the use of any adjusted parameter. Analysis of the spectra calculated using three different anisotropic intermolecular potentials shows that the shapes of pure CO2 lines, in terms of both the Lorentz widths and non-Voigt effects, slightly depend on the used potential. Comparisons between these ab initio calculations and the measured spectra show satisfactory agreement for all considered transitions (from J = 6 to J = 46). They also show that non-Voigt effects on the shape of CO2 transitions are almost independent of the rotational quantum number of the considered lines.
Electro-optically responsive composites of gold nanospheres in 5CB liquid crystal under direct current and alternating current joint action
Authors: Hadjichristov Georgi B. , Marinov Yordan G. , Petrov Alexander G. , Bruno Emanuela , Marino Lucia , Scaramuzza Nicola
Published: February 2014

Direct current (DC) electro-optical (EO) control of transmitted laser beam intensity based on EO controlled coherent light scattering and diffraction by stationary longitudinal texture pattern (LTP) is achieved in planar-oriented cells with a composite mixture of polymer-coated gold spherical nanoparticles (Au-NPs) with a mean diameter of about 12 nm and the room-temperature nematic pentylcyanobiphenyl (5CB). At relatively low DC voltage of about 5 V, the effective scattering/diffraction by Au-NPs/5CB composites leads to a spatial spreading of transmitted coherent light from a low-power continuous wave laser beam, resulting in a drastic reduction of its local intensity. The effect is polarization dependent and is strongest when the polarization of the input laser beam is along the LTP. The EO response of Au-NPs/5CB mixtures is studied under DC and alternating current (AC) joint action with the aim of the potential use of these composite materials as EO controlled diffusers. The specific V-shaped sharp dip in the DC voltage-dependent coherent light transmittance of Au-NPs/5CB planar films, as well as the possibility for erasing the scattering/diffractive LTP in the films by joint low AC voltage, can be useful for EO applications in the field of process control and for detection of weak dynamic electric fields.
Two charged states of hydrogen on the SrTiO3(001) surface
Authors: Takeyasu Kotaro , Fukada Keisuke , Ogura Shohei , Matsumoto Masuaki , Fukutani Katsuyuki
Published: February 2014

The effects of hydrogen exposure on the electronic structure of two types of SrTiO3(001) surfaces, oxygen-deficient (OD) and nearly-vacancy-free (NVF) surfaces, were investigated with ultraviolet photoemission spectroscopy and nuclear reaction analysis. Upon molecular hydrogen exposure to the OD surface which reveals in-gap states at 1.3 eV below the Fermi level, the in-gap state intensity was reduced to half the initial value at a hydrogen coverage of 0.9 ± 0.7 × 1014 cm−2. On the NVF surface which has no in-gap state, on the other hand, atomic-hydrogen exposure induced in-gap states, and the hydrogen saturation coverage was evaluated to be 3.1 ± 0.8 × 1014 cm−2. We argue that H is positively charged as H∼0.3 + on the NVF surface by being coordinated to the O atom, whereas H is negatively charged as H− on the OD surface by occupying the oxygen vacancy site. The stability of H− at the oxygen vacancy site is discussed.
Correlation between magnetic interactions and domain structure in A1 FePt ferromagnetic thin films
Authors: Álvarez N. , Sallica Leva E. , Valente R. C. , Vásquez Mansilla M. , Gómez J. , Milano J. , Butera A.
Published: February 2014

We have investigated the relationship between the domain structure and the magnetic interactions in a series of FePt ferromagnetic thin films of varying thickness. As-made films grow in the magnetically soft and chemically disordered A1 phase that may have two distinct domain structures. Above a critical thickness dcr ∼ 30 nm the presence of an out of plane anisotropy induces the formation of stripes, while for d < dcr planar domains occur. Magnetic interactions have been characterized using the well known DC demagnetization - isothermal remanent magnetization remanence protocols, δM plots, and magnetic viscosity measurements. We have observed a strong correlation between the domain configuration and the sign of the magnetic interactions. Planar domains are associated with positive exchange-like interactions, while stripe domains have a strong negative dipolar-like contribution. In this last case we have found a close correlation between the interaction parameter and the surface dipolar energy of the stripe domain structure. Using time dependent magnetic viscosity measurements, we have also estimated an average activation volume for magnetic reversal, ⟨Vac⟩∼1.37×104 nm3, which is approximately independent of the film thickness or the stripe period.
Random laser action from flexible biocellulose-based device
Authors: dos Santos Molíria V. , Dominguez Christian T. , Schiavon João V. , Barud Hernane S. , de Melo Luciana S. A. , Ribeiro Sidney J. L. , Gomes Anderson S. L. , de Araújo Cid B.
Published: February 2014

We demonstrate random lasing action in flexible bacterial cellulose (BC) membrane containing a laser-dye and either dielectric or metallic nanoparticles (NPs). The novel random laser system consists of BC nanofibers attached with Rhodamine 6G molecules and having incorporated either silica or silver NPs. The laser action was obtained by excitation of the samples with a 6 ns pulsed laser at 532 nm. Minimum laser threshold of ≈0.7 mJ/pulse was measured for the samples with silica NPs, whereas a laser threshold of 2.5 mJ/pulse for a system based on silver NPs was obtained. In both cases a linewidth narrowing from ≈50 to ≈4 nm was observed. Potential applications in biophotonics and life sciences are discussed for this proof-of-concept device.
Ferroelectric nanocomposites of polyvinylidene fluoride/polymethyl methacrylate blend and BaTiO3 particles: Fabrication of β-crystal polymorph rich matrix through mechanical activation of the filler
Authors: Mofokeng Tladi G. , Luyt Adriaan S. , Pavlović Vera P. , Pavlović Vladimir B. , Dudić Duško , Vlahović Branislav , Djoković Vladimir
Published: February 2014

Nanocomposites of polyvinylidene fluoride/polymethyl methacrylate (PVDF/PMMA) blend and mechanically activated barium titanate (BaTiO3) particles were prepared by melt mixing. Modification of filler by means of mechanical activation has a profound effect on the crystallization of PVDF in the blend matrix. Raman analysis showed that the modified BaTiO3 particles, due to higher specific surfaces, induce, predominantly, the crystallization of the electrically active β-phase of PVDF, while the initial micron size particles induce the formation of the most common but non-polar α-crystal form. The introduction of activated particles reduces the overall crystallinity but slightly affects the crystallization and melting temperatures of the matrix. Dielectric spectroscopy revealed that at fixed filler content the dielectric constant of the blend increases with decreasing of the particle size (increasing of the activation time). A similar trend was observed for the storage moduli in dynamic mechanical analysis; the stiffness of the composite was higher when mechanically activated particles were used.
Effect of dopant compensation on the temperature dependence of the transport properties in p-type monocrystalline silicon
Authors: Veirman J. , Martel B. , Dubois S. , Stendera J.
Published: February 2014

In this paper, we investigate the temperature variations of the hole transport properties in initially uncompensated boron-doped Czochralski silicon progressively compensated through thermal donors activation. After each donor generation anneal, the boron and thermal donor concentrations in the samples are determined using (1) the change in carrier concentration at room temperature and (2) the analysis of the temperature variation of the carrier concentration in the range 77–350 K. By comparing both methods with theory, evidence is brought that down to 77 K the Hall factor is unaffected by compensation up to high compensation levels. This is of great interest for researchers working on new solar-grade materials since it nicely suggests that Hall factor models previously established for non-compensated silicon can be applied to compensated samples, for example, when extracting the individual dopant concentrations from the temperature variations of the hole concentration. At very high compensation levels, anomalous Hall data lead to erroneously low carrier mobility values. We showed that this artifact was due to the formation of a n-p-n transistor, arising from the preferential formation of thermal donors in the sample's subsurface. After rejecting these unphysical data from the analysis, we confirm that the hole mobility is greatly affected by compensation in the temperature range investigated. We eventually confront our experimental data to current mobility models and discuss the possible sources of discrepancy.
An iterative inter-track interference mitigation method for two-dimensional magnetic recording systems
Authors: Warisarn C. , Losuwan T. , Supnithi P. , Kovintavewat P.
Published: February 2014

At high recording density, the readback signal of two-dimensional magnetic recording is inevitably corrupted by the two-dimensional (2D) interference consisting of inter-symbol interference and inter-track interference (ITI), which can significantly degrade the overall system performance. This paper proposes an iterative ITI mitigation method using three modified 2D soft-output Viterbi algorithm (2D-SOVA) detectors in conjunction with an iterative processing technique to combat the 2D interference. The codeword of the outer code is divided and then written on three separate tracks. For every iteration, all 2D-SOVA detectors exchange the soft information to improve the reliability of the a priori information and use it in the branch metric calculation, before feeding the refined soft information to the outer decoder. Simulation results show that the proposed method outperforms the conventional receiver and the existing partial ITI mitigation method.
Effect of proton irradiation on AlGaN/GaN high electron mobility transistor off-state drain breakdown voltage
Authors: Hwang Ya-Hsi , Li Shun , Hsieh Yueh-Ling , Ren Fan , Pearton Stephen J. , Patrick Erin , Law Mark E. , Smith David J.
Published: February 2014

The effect of proton irradiation on the off-state drain breakdown voltage of AlGaN/GaN high electron mobility transistors (HEMTs) grown on Si substrates was studied by irradiating protons from the backside of the samples through via holes fabricated directly under the active area of the HEMTs. There was no degradation of drain current nor enhancement of off-state drain voltage breakdown voltage observed for HEMTs irradiated with 275 keV protons, for which the defects created by the proton irradiation were intentionally placed in the GaN buffer. HEMTs with defects positioned in the 2 dimensional electron gas channel region and AlGaN barrier using 330 keV protons not only showed degradation of both drain current and extrinsic transconductance but also exhibited an improvement of the off-state drain breakdown voltage. Finite-element simulations showed the enhancement of the latter were due to a reduction in electric field strength at the gate edges by introduction of charged defects.
Enhanced Raman spectroscopy induced by surface defects in ripple-like CdS microbelts
Authors: Xianghua Zeng , Chuan Hu , Min Zhou , Weiwei Xia , Xiangdong Meng
Published: February 2014

Both normal and ripple-like CdS microbelts (MBs) were prepared and their optical properties were investigated by photoluminescent and Raman measurements. One emission at ∼510 nm for normal CdS MBs and two emissions around 513 and 725 nm for ripple-like one were observed. The longitudinal optical phonon mode (1LO) at ∼304 cm−1 and its overtone mode (2LO) at ∼605 cm−1, multiphonon processes and surface phonon peaked at 281 cm−1 were observed, the larger integrated intensities ratio of 2LO to 1LO indicates a strong exciton-phonon coupling interaction. Furthermore, more than 4 times larger enhanced Raman scattering for the ripple-like MBs than the normal one were observed, and the enhanced Raman scattering is mainly associated with the surface defects, which lead to a strong Fröhlich interaction through the charge transfer, not by the deformation potential through surface plasmon enhancement.
Ag2O dependent up-conversion luminescence properties in Tm3+/Er3+/Yb3+ co-doped oxyfluorogermanate glasses
Authors: Hu Yuebo , Qiu Jianbei , Song Zhiguo , Zhou Dacheng
Published: February 2014

Up-conversion (UC) luminescence properties of Ag/Tm3+/Er3+/Yb3+ co-doped oxyfluorogermanate glasses have been studied to assess the effective role of silver nanoparticles as a sensitizer for Tm3+ and Er3+ ions. The X-ray diffraction patterns obtained in this work do not reveal any crystalline phase in the glass. However, the absorption spectra reveal that surface plasmons resonance band of Ag undergoes a distinct split with two maxima and a very broad absorption peak with a background that extends toward the near infrared (NIR) with the increasing of Ag2O added concentration. Transmission electron microscope images confirm that silver nanoparticles have been precipitated from matrix glasses and show their distribution, size, and shapes. In addition, changes in UC luminescence intensity of four emission bands 476, 524, 546, and 658 nm corresponding to 1G4 → 3H6 (Tm3+), (2H11/2, 4S3/2) → 4I15/2 (Er3+), and 4F9/2 → 4I15/2 (Er3+) transitions, respectively, as a function of silver addition to the base composition have been measured under 980 nm excitation. It is confirmed that Ag2O added concentration plays an important role in increasing the UC luminescence intensity; however, further increase in Ag2O added concentration reduces the intensity.
A technique for giant mechanical energy harvesting using ferroelectric/antiferroelectric materials
Authors: Patel Satyanarayan , Chauhan Aditya , Vaish Rahul
Published: February 2014

Ferroelectric materials are widely employed as piezoelectric materials for numerous energy harvesting systems. However, conventional systems employing direct piezoelectric effect for vibrational energy harvesting suffer from low energy density and high actuation frequency requirements. In this regards, the authors have presented a new technique for giant mechanical energy conversion using ferroelectric/antiferroelectric materials in a cyclic manner. The proposed method will allow for large electromechanical energy conversion in a wide frequency domain. The cycle was simulated for polycrystalline Pb0.99Nb0.02[(Zr0.57Sn0.43)0.94Ti0.06]0.98O3 (PNZST) antiferroelectric bulk ceramic. It was observed that for cycle parameters of (20 to 60 kV·cm−1 and 0 to 250 MPa), a harvesting energy density of 689 kJ·m−3·cycle−1 can be obtained for uniaxial compressive stress. While an energy density of 919 kJ·m−3·cycle−1 can be obtained for radial compressive stress with cycle parameters of (20 to 60 kV·cm−1 and 0 to 360 MPa). This is several orders of magnitude larger than the highest energy density reported in the literature.
Textured Pr2Fe14B flakes with submicron or nanosize thickness prepared by surfactant-assisted ball milling
Authors: Zuo Wen-Liang , Liu Rong-Ming , Zheng Xin-Qi , Wu Rong-Rong , Hu Feng-Xia , Sun Ji-Rong , Shen Bao-Gen
Published: February 2014

The textured Pr2Fe14B nanoflakes were produced by surfactant-assisted ball milling (SABM). Single phase tetragonal structure was characterized for the samples before and after SABM by X-ray diffraction (XRD). The thickness and length of the as-milled flakes are mainly in the range of 50–150 nm and 0.5–2 μm, respectively. For the field-aligned Pr2Fe14B nanoflakes, the out-of-plane texture (the easy magnetization direction (EMD) along the c-axis) is indicated from the increasing (00l) peaks in the XRD patterns. SEM image demonstrates that the EMD is parallel to flaky surface, which is different from the RCo5 (R = rare earth) system with EMD perpendicular to the surface. We propose a hypothesis that the easy glide planes are related with the area of crystal planes. In addition, a large coercivity Hc = 3.9 kOe is observed in the Pr2Fe14B flakes with strong texture.
Effect of internal electric field on InAs/GaAs quantum dot solar cells
Authors: Kasamatsu Naofumi , Kada Tomoyuki , Hasegawa Aiko , Harada Yukihiro , Kita Takashi
Published: February 2014

We studied time-resolved carrier recombination in InAs/GaAs quantum dot (QD) solar cells. The electric field in a p-i-n diode structure spatially separates photoexcited carriers in QDs, strongly affecting the conversion efficiency of intermediate-band solar cells. The radiative decay lifetime is dramatically reduced in a strong electric field (193 kV/cm) by efficient recombination due to strong carrier localization in each QD and significant tunneling-assisted electron escape. Conversely, an electric field of the order of 10 kV/cm maintains electronic coupling in the stacked QDs and diminishes tunneling-assisted electron escape.
Sensitivity studies for the main r process: β-decay rates
Authors: Mumpower M. , Cass J. , Passucci G. , Surman R. , Aprahamian A.
Published: February 2014

The pattern of isotopic abundances produced in rapid neutron capture, or r-process, nucleosynthesis is sensitive to the nuclear physics properties of thousands of unstable neutron-rich nuclear species that participate in the process. It has long been recognized that the some of the most influential pieces of nuclear data for r-process simulations are β-decay lifetimes. In light of experimental advances that have pushed measurement capabilities closer to the classic r-process path, we revisit the role of individual β-decay rates in the r process. We perform β-decay rate sensitivity studies for a main (A > 120) r process in a range of potential astrophysical scenarios. We study the influence of individual rates during (n, γ)-(γ, n) equilibrium and during the post-equilibrium phase where material moves back toward stability. We confirm the widely accepted view that the most important lifetimes are those of nuclei along the r-process path for each astrophysical scenario considered. However, we find in addition that individual β-decay rates continue to shape the final abundance pattern through the post-equilibrium phase, for as long as neutron capture competes with β decay. Many of the lifetimes important for this phase of the r process are within current or near future experimental reach.
Thermal Decomposition of Diethylketone Cyclic Triperoxide in Polar Solvents
Authors: Barreto Gastón P. , Alvarez Elida E. , Eyler Gladys N. , Cañizo Adriana I. , Allegretti Patricia E.
Published: February 2014

The thermolysis of diethylketone cyclic triperoxide (3,3,6,6,9,9-hexaethyl-1,2,4,5,7,8-hexaoxacyclononane, DEKTP) was studied in different polar solvents (ethanol, 2-propanol, 1-butanol, 2-butanol, 2-methyl-2-propanol, and acetonitrile). The rate constant values (kd) are higher for reactions performed in secondary alcohols probably because of the possibility to form a cyclic adduct with the participation of the hydrogen atom bonded to the secondary carbon. The kinetic parameters were correlated with the physicochemical properties of the selected solvents. The products of the DEKTP thermal decomposition in different polar solvents support a radical-based decomposition mechanism.
Sperm survival kinetics in different types of bull semen: progressive motility, plasma membrane integrity, acrosomal status and reactive oxygen species generation
Authors: Ahmad Mushtaq , Ahmad Nasim , Riaz Amjad , Anzar Muhammad
Published: February 2014

This study was designed to compare the kinetics of sperm survival in different types of bull semen. Fresh ejaculates from four bulls were pooled, diluted in Tris-citric acid-egg yolk-glycerol extender, cooled to 4°C, frozen in LN2 and thawed at 37°C. Fresh, diluted, cooled and frozen–thawed semen were incubated at 37°C, and evaluated at 0, 2, 4, 6, 12 and 24 h after the beginning of incubation. In Experiment 1, progressive sperm motility, normal acrosomes and plasma membrane integrity and asymmetry were determined. In Experiment 2, generation of superoxide anion (O2•) along with plasma membrane permeability and generation of hydrogen peroxide (H2O2) along with plasma membrane integrity were assessed. In Experiment 1, frozen–thawed semen had shorter survival times for progressive sperm motility, and spermatozoa with intact plasma membranes and acrosomes (IPM-IACR) as compared with other types of semen (P < 0.05). Fresh spermatozoa underwent a necrotic pathway, diluted and cooled spermatozoa underwent an apoptosis-like pathway and frozen–thawed spermatozoa underwent both necrotic and apoptosis-like pathways. In Experiment 2, spermatozoa in all four types of semen exhibited O2•– generation and increased plasma membrane permeability, and became necrotic without H2O2 generation during incubation (P < 0.05). In conclusion, frozen–thawed semen had shorter sperm longevity, which has important implications relating to the timing of artificial insemination. Different types of semen followed different death pathways. During incubation, spermatozoa in all types of semen generated O2•–, which increased the permeability and compromised the integrity of the plasma membrane.
Effect of ageing on surface charge characteristics and adsorption behaviour of cadmium and arsenate in two contrasting soils amended with biochar
Authors: Nagodavithane Chamali Laksala , Singh Balwant , Fang Yunying
Published: February 2014

Biochar has been recognised as an effective amendment for the remediation of contaminated soils; however, there is limited knowledge on the effects of biochar ageing in soil on its adsorption behaviour for cationic and anionic species. Biochars are considered to develop negative charge from oxidation with ageing, which may create additional interaction mechanisms for adsorption processes. In the present study, surface charge characteristics and cadmium (Cd) and arsenate (AsO43–) adsorption behaviour of aged biochar were investigated in two soils with variable charge, an Oxisol and an Inceptisol, by comparing (i) unamended soils, and soils amended with (ii) fresh biochar (450°C) and (iii) biochar (450°C) aged for 12 months, applied at a rate of 2% w/w. Surface charge characteristics were assessed using the ‘index’ ion adsorption method, with a LiCl electrolyte. Batch adsorption studies were conducted using fresh and aged soil–biochar mixtures. In contrast to previous studies, the results provided no evidence of an increase in cation exchange capacity as a consequence of biochar ageing. There was an increase in Cd adsorption in the presence of aged biochar in both soil types compared with unamended soils and soils amended with fresh biochar. Results also indicated an increase in AsO43– adsorption in the Inceptisol amended with aged biochar, whereas a decrease in AsO43– adsorption was observed in the Oxisol amended with aged biochar. Overall, the study has highlighted that adsorption behaviour of aged biochar varies depending on the ion it interacts with, soil properties and solution pH.
Toxicity effects of oral gavage of aqueous solutions of cube-root powder and sodium nitrite in common carp
Authors: Morgan D. K. J. , Kumar H. , Ling N. , Hicks B. J.
Published: February 2014

Context Common carp (Cyprinus carpio) is a highly invasive freshwater pest fish that has been linked to waterway degradation when it has been introduced and exists at high densities. The deployment of a toxic bait may be a logistically simple tool that wildlife managers could use to reduce carp populations. Rotenone, the piscicide most commonly used in previous attempts to produce a carp bait is very expensive, albeit highly toxic to carp. We investigated the toxicity of two potential alternative piscicides to carp. Aim To determine the oral toxicity of two alternative cheaper toxins to carp, cube-root powder (CRP) and sodium nitrite (nitrite). Methods CRP or nitrite was administered in an aqueous solution by gavage to lightly sedated captive carp. The aqueous solution consisted of a 30 : 70 mixture (w/w) of the surfactant, Polysorbate 80, to increase the absorption of toxins through the intestine, and water. Key results The LD50 of CRP and nitrite in carp was 135.7 mg kg–1 and 122.0 mg kg–1, respectively. Conclusions Both CRP and nitrite are toxic to carp at dose rates low enough to be incorporated into a piscicide bait for this species. Implications Both CRP and nitrite appear to be viable alternative oral piscicides to rotenone for carp and warrant further investigation of delivery in bait.
Habitats associated with vehicle collisions with wild pigs
Authors: Beasley James C. , Grazia Tracy E. , Johns Paul E. , Mayer John J.
Published: February 2014

Context Over the past few decades, the frequency of wild pig–vehicle collisions (WPVCs) and number of human fatalities associated with these accidents have increased with expanding populations of this species, particularly in regions outside its native distribution. Aims To better understand this widespread and growing human safety threat, we quantified habitat attributes associated with 311 WPVC locations occurring between 1983 and 2012 at the Savannah River Site (SRS) in South Carolina, USA, to test the hypothesis that WPVCs occur more frequently in areas proximal to preferred habitats (i.e. riparian and bottomland hardwood habitats). Methods At each collision site, we measured the distance to the nearest wetland and stream, as well as the composition of habitats within 100-m and 1699-m buffers. We then contrasted habitat attributes associated with collision sites with those from randomly selected locations along the same roads, to identify habitat characteristics contributing to a higher incidence of these accidents. Key results WPVCs were non-randomly distributed across both spatial scales measured, with collisions occurring more frequently in areas of preferred habitat for this species. Specifically, collisions occurred in areas closer to streams and containing less pine forest than at random locations at both spatial scales evaluated. Conclusions Similar to vehicle accidents with other ungulate species, our study suggested that vehicle collisions involving wild pigs are spatially clustered around preferred habitat types. Management efforts to reduce vehicle collisions with wild pigs should be focussed in areas where roadways bisect preferred habitats such as stream crossings and bottomland hardwood or other riparian habitats. Implications These data will aid in the development of mitigation strategies to reduce the frequency and impacts of WPVCs in areas of high wild-pig densities. However, given the paucity of data on WPVC mitigation, additional research is needed to quantify the efficacy of various methods (e.g. signage, fencing, underpasses) at reducing the frequency and severity of collisions with this species.
Histone demethylase Jmjd3 is required for the development of subsets of retinal bipolar cells
Authors: Iida Atsumi , Iwagawa Toshiro , Kuribayashi Hiroshi , Satoh Shinya , Mochizuki Yujin , Baba Yukihiro , Nakauchi Hiromitsu , Furukawa Takahisa , Koseki Haruhiko , Murakami Akira , Watanabe Sumiko
Published: February 2014

Significance

The role of repressive gene regulation through histone modifications is known in various biological processes. Histone H3 trimethyl Lys27 (H3K27me3) represses gene expression, and our goal was to understand how this methylation regulates cell differentiation in the vertebrate retina. In this work, we focused on the role of demethylase (Jmjd3) of H3K27me3 in retinal development. Spatiotemporal expression patterns of Jmjd3 during retinal development were shown. Suppression of Jmjd3 expression during retinal development resulted in the failure of differentiation of retinal cell subsets. Lowered expression of genes essential for differentiation of the subsets by loss of expression of Jmjd3 was observed. Therefore, we propose that lineage-specific H3K27me3 demethylation of critical gene loci by spatiotemporal-specific Jmjd3 expression is required for appropriate maturation of retinal cells.
Toward a poetics of aging: The links between literature and life
Authors: Randall William L. , McKim A. Elizabeth
Published: February 2014

Inquiries concerning the nature of ‘biographical aging’ within the emerging field of ‘narrative gerontology’ have pointed to the need for a detailed consideration of the parallels between lived texts and literary ones. This article draws on a number of such parallels in order to outline what might be called apoeticsof aging. The central proposal is organized around 3 key concepts: narrative imagination, narrative identity, and narrative environment. The article concludes by speculating on some of the applications of the proposal in relation to growing old, as opposed to merely getting old. (Aging, Narrative, Gerontology, Poetics, Imagination)
An exploratory study of mother-child storytelling in East India and Northeast United States
Authors: Harkins Debra A. , Ray Sukanya
Published: February 2014

This study examined cultural variations in parental goals of storytelling and story constructions to and with young children. Sixty-five (34 East India; 36 USA) mothers and their four-to-five year old children were audio taped as they read a non-worded picture storybook. East India mothers told longer stories that included more evaluative comments and responses to their child's questions than US mothers. Content and evaluation of character and story action reflected cultural themes of collectivism of India and individualism of USA. Enculturation through storytelling is discussed. (Mother-Child Storytelling, Individualism, Collectivism, Narrative)
Beyond the counter-narrative
Authors: Adame Alexandra L. , Knudson Roger M.
Published: February 2014

The discourse of the medical model of mental illness tends to dominate people’s conceptions of the origins and treatments of psychopathology. This reductionistic discourse defines people’s experiences of psychological distress and recovery in terms of illnesses, chemical imbalances, and broken brains. However, the master narrative does not represent every individual’s lived experience, and alternative narratives of mental health and recovery exist that challenge our traditional understandings of normality and psychopathology. Guided by the method of interpretive interactionism, we examined how psychiatric survivors position themselves in relation to the medical model’s narrative of recovery. In its inception, the psychiatric survivor movement created a counter-narrative of protest in opposition to the medical model’s description and treatment of psychopathology. Since then, the movement has moved beyond the counter-narrative and has constructed an alternative narrative; one that is not defined in opposition to the master narrative but instead participates in an entirely different discourse.
The narrative reconstruction of psychotherapy
Authors: Adler Jonathan M. , McAdams Dan P.
Published: February 2014

Going to psychotherapy represents an atypical, usually unanticipated, and often emotionally significant experience in the life course. As with many such events, people construct stories about therapy experiences in order to make sense out of them and to provide their lives with a sense of unity and purpose. Yet beyond these purposes, the storying of psychotherapy is also central to the maintenance of the therapeutic gains achieved during the course of treatment (e.g., Frank, 1961; Spence, 1982). In the present study, the psychotherapy stories of 76 community adults are assessed using grounded theory methodology to determine narrative patterns that distinguish between individuals who currently show different constellations of psychological health. Two dimensions of current psychological health — ego development, or complex meaning making processes, and psychological well-being — serve as the basis for comparisons between participants. Four ways of storying psychotherapy are described, and preliminary interpretations for these types are suggested. In summary: participants high in ego development and high in well-being emphasized their personal agency throughout their stories; participants high in ego development and low in well-being prominently featured their therapists and pointed to the therapeutic alliance as the mechanism of treatment; participants low in ego development and high in well-being adopted components of dominant cultural narratives of therapy; and the stories of participants low in ego development and low in well-being presented an interpretive challenge, lacking a certain standard of narrative coherence. The themes we identified lay the groundwork for future research on the narrative construction of psychotherapy and may prove useful to clinicians as they strive to help their clients to co-construct successful stories about their therapeutic work together.
Telling stories their way
Authors: Bailey Alison L. , Moughamian Ani C.
Published: February 2014

Fifty-nine mother-child dyads were studied when children were 3, 4 and 5 years to examine (1) parental verbal support of children’s personal narratives, and (2) how support may relate to later literacy outcomes. Supporting narration by prompting for specific events was the most widespread and frequent scaffold when children were 3 and 4 years old. All mothers decreased the number and range of support types by the time children were 5, but specific event prompts were used more frequently by mothers of children who were readers by the end of 1st grade than by mothers of emergent readers. Mothers of readers also used more of their own narration to add to the detail of stories and to elicit responses when children were 4 and 5. Mothers of emergent readers used proportionately more prompts for non-specific events and for correction of stories. Emergent readers were less responsive than readers at all 3 time points.