bluuebunny/crossref_metadata_2025 huggingface dataset:
Shear-rate dependent effective thermal conductivity of H2O+SiO2 nanofluids
Authors: Sun Chengzhen , Bai Bofeng , Lu Wen-Qiang , Liu Jie
Published: May 2013

Effective thermal conductivity (ETC) of water-based silicon dioxide nanofluids in shear flow fields (flow shear rate range was 0–820 1/s) was measured using a rotating Couette apparatus. The results show that the ETC of the nanofluids in shear flow fields is significantly higher than that in static states. For the flow shear rates lower than a critical value (infinite-shear rate), the ETC asymptotically increases with increasing the flow shear rate; for the flow shear rates higher than the critical value, the ETC displays a plateau value (infinite-shear thermal conductivity). The increase of the ETC with shear rate is more obvious as increase the nanoparticle diameter and the nanoparticle volume fraction. For 16 different measured nanofluids, the infinite-shear rates vary from 445.0 to 712.1 1/s, while the infinite-shear thermal conductivities increase by 9%–17% comparing with the zero-shear thermal conductivities. The conventional ETC prediction correlation proposed for the suspensions containing micro-sized particles is not suitable for the nanofluids qualitatively and quantitatively. Finally, an exponential correlation is proposed based on our measured data to predict the ETC of nanofluids considering the effects of flow shear rate, nanoparticle diameter, and nanoparticle volume fraction.
Measuring dipolar and J coupling between quadrupolar nuclei using double-rotation NMR
Authors: Perras Frédéric A. , Bryce David L.
Published: May 2013

Among the interactions which govern NMR spectra, spin-spin coupling interactions provide the most direct form of structural information which is of interest to chemists. Dipolar coupling may be used to measure internuclear distances directly and J coupling may be used to identify bonding interactions and provide insights into the nature of the bonds. It is well known that the presence of a quadrupolar interaction reintroduces the dipolar interaction in spinning samples; however, similarly to the J coupling, this information is often lost if the observed nucleus is quadrupolar due to quadrupolar spectral broadening. Here we show for multiple spin pairs that double-rotation (DOR) NMR fully removes the effects of the quadrupolar interaction on the NMR spectrum leaving only the effects of dipolar and J couplings. We also demonstrate that the J coupling multiplets do not disappear for quadrupolar A2 spin pairs as they do for spin-1/2 nuclei. With DOR NMR, it is then straightforward to measure homonuclear J coupling constants between magnetically equivalent quadrupolar nuclei. A deeper understanding of the origins of the magnitudes and dominant mechanisms of J coupling for quadrupolar spin pairs in a series of related compounds is obtained by decomposing computed J coupling constants into their major molecular orbital contributions.
Brownian dynamics method for simulation of binding kinetics of patterned colloidal spheres with hydrodynamic interactions
Authors: Liu Jun , Larson Ronald G.
Published: May 2013

We develop a Brownian dynamics simulation method with full hydrodynamic interactions (HI) to study the recognition kinetics between two patterned colloidal spheres. We use a general resistance matrix (12*12) to describe both the far and near-field hydrodynamics of translation, rotation, and translation-rotation coupling between the two spheres, adopted from Jeffrey and Onishi [J. Fluid Mech. 139, 261 (1984)10.1017/S0022112084000355]. We apply the method to the specific binding of “patchy” spheres, including effects of depletion attraction and orientation-specific binding, as are present in “Janus” spheres whose surfaces contain hydrophobic and hydrophilic faces [Q. Chen, S. C. Bae, and S. Granick, Nature (London) 469, 381 (2011)10.1038/nature09713]. The binding times obtained between two non-patterned spheres (of equal or unequal diameter) with or without HI extrapolated to infinite dilution are shown to be in good agreement with theoretical predictions of the Smoluchowski equation. In addition, the binding times for pairs of spheres for three cases of surface patterning of the two spheres (uniform-uniform, uniform-Janus, and Janus-Janus) are compared with or without rotational motion.
Studies of photoconductivity and field effect transistor behavior in examining drift mobility, surface depletion, and transient effects in Si-doped GaN nanowires in vacuum and air
Authors: Sanford N. A. , Robins L. H. , Blanchard P. T. , Soria K. , Klein B. , Eller B. S. , Bertness K. A. , Schlager J. B. , Sanders A. W.
Published: May 2013

Variable intensity photoconductivity (PC) performed under vacuum at 325 nm was used to estimate drift mobility (μ) and density (σs) of negative surface charge for c-axis oriented Si-doped GaN nanowires (NWs). In this approach, we assumed that σs was responsible for the equilibrium surface band bending (∅) and surface depletion in the absence of illumination. The NWs were grown by molecular beam epitaxy to a length of approximately 10 μm and exhibited negligible taper. The free carrier concentration (N) was separately measured using Raman scattering which yielded N = (2.5 ± 0.3)  × 1017 cm−3 for the growth batch studied under 325 nm excitation. Saturation of the PC was interpreted as a flatband condition whereby ∅ was eliminated via the injection of photogenerated holes. Measurements of dark and saturated photocurrents, N, NW dimensions, and dimensional uncertainties, were used as input to a temperature-dependent cylindrical Poisson equation based model, yielding σs in the range of (3.5 to 7.5) × 1011 cm−2 and μ in the range of (850 to 2100) cm2/(V s) across the (75 to 194) nm span of individual NW diameters examined. Data illustrating the spectral dependence and polarization dependence of the PC are also presented. Back-gating these devices, and devices from other growth batches, as field effect transistors (FETs) was found to not be a reliable means to estimate transport parameters (e.g., μ and σs) due to long-term current drift. The current drift was ascribed to screening of the FET back gate by injected positive charge. We describe how these gate charging effects can be exploited as a means to hasten the otherwise long recovery time of NW devices used as photoconductive detectors. Additionally, we present data illustrating comparative drift effects under vacuum, room air, and dry air for both back-gated NW FETs and top-gated NW MESFETs.
Infrared spectroscopy and tunneling dynamics of the vinyl radical in 4He nanodroplets
Authors: Raston Paul L. , Liang Tao , Douberly Gary E.
Published: May 2013

The vinyl radical has been trapped in 4He nanodroplets and probed with infrared laser spectroscopy in the CH stretch region between 2850 and 3200 cm−1. The assigned band origins for the CH2 symmetric (ν3), CH2 antisymmetric (ν2), and lone α-CH stretch (ν1) vibrations are in good agreement with previously reported full-dimensional vibrational configuration interaction computations [A. R. Sharma, B. J. Braams, S. Carter, B. C. Shepler, and J. M. Bowman, J. Chem. Phys. 130, 174301 (2009)]10.1063/1.3120607. For all three bands, a-type and b-type transitions are observed from the lowest symmetry allowed roconvibrational state of each nuclear spin isomer, which allows for a determination of the tunneling splittings in both the ground and excited vibrational levels. Comparisons to gas phase millimeter-wave rotation-tunneling [K. Tanaka, M. Toshimitsu, K. Harada, and T. Tanaka, J. Chem. Phys. 120, 3604–3618 (2004)]10.1063/1.1642583 and high-resolution jet-cooled infrared spectra [F. Dong, M. Roberts, and D. J. Nesbitt, J. Chem. Phys. 128, 044305 (2008)]10.1063/1.2816704 reveal that the He solvent effect is to reduce the ground and ν3 excited state tunneling splittings by ≈20%. This solvent-induced modification of the tunneling dynamics can be reasonably accounted for by assuming either a ≈2.5% increase in the effective barrier height along the tunneling coordinate or a ≈5% increase in the effective reduced mass of the tunneling particles.
Vibrations of porphycene in the S and S1 electronic states: Single vibronic level dispersed fluorescence study in a supersonic jet
Authors: Mengesha Ephriem T. , Sepioł Jerzy , Borowicz Paweł , Waluk Jacek
Published: May 2013

Supersonic jet-isolated porphycene has been studied using the techniques of laser-induced fluorescence excitation, single vibronic level fluorescence, and spectral hole burning, combined with quantum mechanical calculations of geometry and vibrational structure of the ground and lowest electronically excited singlet states. Porphycene is a model for coherent double hydrogen tunneling in a symmetrical double well potential, as evidenced by tunneling splittings observed in electronic absorption and emission. The results led to reliable assignment of low frequency modes in S0 and S1 electronic states. The values of tunneling splitting were determined for ground state vibrational levels. In the case of tautomerization-promoting 2Ag mode, tunneling splitting values significantly increase with the vibrational quantum number. Mode coupling was demonstrated by different values of tunneling splitting obtained for coexcitation of two or more vibrations. Finally, alternation of relative intensity patterns for the components of 2Ag tunneling doublet observed for excitation and emission into different vibrational levels suggests that the energy order of levels corresponding to (+) and (−) combinations of nuclear wave functions is different for even and odd vibrational quantum numbers.
Determination of favorable inter-particle interactions for formation of substitutionally ordered solid phases from a binary mixture of oppositely charged colloidal suspensions
Authors: Pavaskar Ganeshprasad , Punnathanam Sudeep N.
Published: May 2013

The solid phase formed by a binary mixture of oppositely charged colloidal particles can be either substitutionally ordered or substitutionally disordered depending on the nature and strength of interactions among the particles. In this work, we use Monte Carlo molecular simulations along with the Gibbs-Duhem integration technique to map out the favorable inter-particle interactions for the formation of substitutionally ordered crystalline phases from a fluid phase. The inter-particle interactions are modeled using the hard core Yukawa potential but the method can be easily extended to other systems of interest. The study obtains a map of interactions depicting regions indicating the type of the crystalline aggregate that forms upon phase transition.
The Lowe-Andersen thermostat as an alternative to the dissipative particle dynamics in the mesoscopic simulation of entangled polymers
Authors: Khani Shaghayegh , Yamanoi Mikio , Maia Joao
Published: May 2013

Dissipative Particle Dynamics (DPD) has shown a great potential in studying the dynamics and rheological properties of soft matter; however, it is associated with deficiencies in describing the characteristics of entangled polymer melts. DPD deficiencies are usually correlated to the time integrating method and the unphysical bond crossings due to utilization of soft potentials. One shortcoming of DPD thermostat is the inability to produce real values of Schmidt number for fluids. In order to overcome this, an alternative Lowe-Anderson (LA) method, which successfully stabilizes the temperature, is used in the present work. Additionally, a segmental repulsive potential was introduced to avoid unphysical bond crossings. The performance of the method in simulating polymer systems is discussed by monitoring the static and dynamic characteristics of polymer chains and the results from the LA method are compared to standard DPD simulations. The performance of the model is evaluated on capturing the main shear flow properties of entangled polymer systems. Finally the linear and nonlinear viscoelastic properties of such systems are discussed.
Note: Magnetic noise from the inner wall of a magnetically shielded room
Authors: Khan Sheraz , Cohen David
Published: May 2013

We measured the thermal magnetic noise generated by the inner high-permeability wall of a magnetically shielded room. This room houses a magnetoencephalogram (MEG), which contains 102 “small” identical magnetometers. For the measurement, we created two large magnetometers by summing the outputs of 46 magnetometers equally on the helmet's left and right side, to look at the summed noise of the right and left vertical walls. From these summed outputs, we calculated the rms noise amplitude due to all six walls at the MEG location to be ∼0.5 f T/$\sqrt {{\rm Hz}} $ Hz at 100 Hz, only slowly rising with lower frequency. This is well below the system noise of each small MEG magnetometer, hence is negligible for the MEG.
The expansion of a collisionless plasma into a plasma of lower density
Authors: Perego M. , Howell P. D. , Gunzburger M. D. , Ockendon J. R. , Allen J. E.
Published: May 2013

This paper considers the asymptotic and numerical solution of a simple model for the expansion of a collisionless plasma into a plasma of lower density. The dependence on the density ratio of qualitative and quantitative features of solutions of the well-known cold-ion model is explored. In the cold-ion limit, we find that a singularity develops in the ion density in finite time unless the density ratio is zero or close to unity. The classical cold-ion model may cease to be valid when such a singularity occurs and we then regularize the model by the finite ion-temperature Vlasov-Poisson system. Numerical evidence suggests the emergence of a multi-modal velocity distribution.
Bohr-Sommerfeld quantization condition for Dirac states derived from an Ermakov-type invariant
Authors: Thylwe Karl-Erik , McCabe Patrick
Published: May 2013

It is shown that solutions of the second-order decoupled radial Dirac equations satisfy Ermakov-type invariants. These invariants lead to amplitude-phase-type representations of the radial spinor solutions, with exact relations between their amplitudes and phases. Implications leading to a Bohr-Sommerfeld quantization condition for bound states, and a few particular atomic/ionic and nuclear/hadronic bound-state situations are discussed.
Stepwise behavior of the core trajectory in magnetic vortex dynamics under an alternating-current magnetic field
Authors: Shim Je-Ho , Piao Hong-Guang , Hyuk Lee Sang , Kun Oh Suhk , Yu Seong-Cho , Kee Han Seung , Eon Kim Dong , Kim Dong-Hyun
Published: May 2013

We predict that the radial distance of a magnetic vortex core from the disk center shows a stepwise behavior during initial excited motion under an alternating-current magnetic field by means of micromagnetic simulations. The stepwise behavior is clearly observed around the resonance frequency and depends on the amplitude and frequency of the external magnetic field. It has been found that the stepwise behavior originates from the relative phase difference between the gyrovector and the radial distance of the vortex core.
Tracking an imploding cylinder with photonic Doppler velocimetry
Authors: Dolan D. H. , Lemke R. W. , McBride R. D. , Martin M. R. , Harding E. , Dalton D. G. , Blue B. E. , Walker S. S.
Published: May 2013

Cylindrical implosion offers a path to extreme material states, reaching considerably higher pressures than planar geometry. However, diagnosing compressed material in cylindrical geometry is challenging. Time-resolved velocimetry, a standard technique in planar compression, is difficult to incorporate into cylindrical experiments. This paper describes the use of photonic Doppler velocimetry (PDV) in magnetically driven cylindrical compression experiments at the Sandia Z machine. With this diagnostic, it is possible to track the interior of an imploding cylinder beyond 20 km/s. A “leapfrog” implementation is described to support velocities well above the bandwidth limits of standard PDV measurements.
A simplified representation of anisotropic charge distributions within proteins
Authors: Hoppe Travis
Published: May 2013

Effective coarse-grained representations of protein-protein interaction potentials are vital in the modeling of large scale systems. We develop a method to fit an arbitrary number of effective charges to approximate the electrostatic potential of a protein at a given pH in an ionic solution. We find that the effective charges can reproduce an input potential calculated from a high resolution Poisson-Boltzmann calculation. Since the effective charges used in this model are not constrained to the locations of the original charged groups, the extra degrees of freedom allows us to reproduce the field anisotropy with fewer charges. The fitting procedure uses a number of approximations in the charge magnitudes, initial conditions, and multipoles to speed convergence. The most significant gains are found by fitting the multipole moments of the effective charge potential to the moments of the original field. We show that the Yukawa potential is not only sufficient as a pairwise summation in reproducing the potential, but comes naturally from the linearized expansion of the Poisson-Boltzmann equation. We compute interaction energies and find excellent agreement to the original potential. From the effective charge model we compute the electrostatic contribution to the second virial coefficient.
Structure, band gap, and Mn-related mid-gap states in epitaxial single crystal (Zn1−xMgx)1−yMnyO thin films
Authors: Zhu Dapeng , Liu Guolei , Xiao Shuqin , Yan Shishen , He Shumin , Cai Li , Li Qinghao , Cao Qiang , Hu Shujun , Chen Yanxue , Kang Shishou , Mei Liangmo
Published: May 2013

Epitaxial (Zn1−xMgx)1−yMnyO thin films were grown on c-Al2O3 substrates by radio frequency oxygen plasma assisted molecular beam epitaxy. Single crystal structure of the (Zn1−xMgx)1−yMnyO films was revealed by reflection high energy electron diffraction and X-ray diffraction. The band gap of the films can be tuned dramatically with increasing the Mg concentration, while the onset energy of Mn-related mid-gap absorption band only shows a small blue shift. Photoconductivity measurements indicate the Mn-related mid-gap states in (Zn1−xMgx)1−yMnyO films can create free carriers and contribute to charge transfer transitions. The conduction band offset ΔEC = 0.13 eV and valence band offset ΔEV = 0.1 eV were obtained for ZnO/Zn0.8Mg0.2O heterostructures, which increase to ΔEC = 0.21 eV and ΔEV = 0.14 eV for ZnO/Zn0.7Mg0.3O heterostructures.
Optical properties of “black silicon” formed by catalytic etching of Au/Si(100) wafers
Authors: Matsui Yusuke , Adachi Sadao
Published: May 2013

“Black silicon” layers were formed by catalytic etching of Au/Si(100) wafers in HF−H2O2−H2O solutions at room temperature. The structural and optical properties of the catalytic-etched Si layers were investigated by scanning electron microscopy (SEM), wettability observations, Fourier-transform infrared (FTIR) spectroscopy analysis, near-IR−UV transmittance, Raman scattering, photoluminescence (PL), PL excitation, and PL decay measurements. The SEM observation suggested that the vertically well-aligned Si nanowires can be formed in the limited synthesis conditions (H2O2 concentration, deposited Au film thickness, and etching time). FTIR and near-IR−UV transmittance spectra revealed that the catalytic-etched Si layers show optical absorbance about two orders higher in the far-IR−UV region than that for the single-crystalline Si substrate. The Raman scattering spectra were found to be clearly different from those for the bulk single-crystalline Si and were analyzed using a newly developed model. All the catalytic-etched Si samples showed efficient visible emission at ∼2 eV. This emission can be explained by the quantum-mechanical confinement effect, i.e., a relaxation of the momentum conservation at and above the indirect-absorption edge of Si (supra-EgX emission).
Communication: Certifying the potential energy landscape
Authors: Mehta Dhagash , Hauenstein Jonathan D. , Wales David J.
Published: May 2013

It is highly desirable for numerical approximations to stationary points for a potential energy landscape to lie in the corresponding quadratic convergence basin. However, it is possible that an approximation may lie only in the linear convergence basin, or even in a chaotic region, and hence not converge to the actual stationary point when further optimization is attempted. Proving that a numerical approximation will quadratically converge to the associated stationary point is termed certification. Here, we apply Smale's α-theory to stationary points, providing a certification serving as a mathematical proof that the numerical approximation does indeed correspond to an actual stationary point, independent of the precision employed. As a practical example, employing recently developed certification algorithms, we show how the α-theory can be used to certify all the known minima and transition states of Lennard-Jones LJN atomic clusters for N = 7, …, 14.
Improving the intrinsic cut-off frequency of gate-all-around quantum-wire transistors without channel length scaling
Authors: Benali A. , Traversa F. L. , Albareda G. , Aghoutane M. , Oriols X.
Published: May 2013

Progress in high-frequency transistors is based on reducing electron transit time, either by scaling their lengths or by introducing materials with higher electron mobility. For gate-all-around quantum-wire transistors with lateral dimensions similar or smaller than their length, a careful analysis of the displacement current reveals that a time shorter than the transit time controls their high-frequency performance. Monte Carlo simulations of such transistors with a self-consistent solution of the 3D Poisson equation clearly show an improvement of the intrinsic cut-off frequency when their lateral areas are reduced, without length scaling.
Viscous coalescence of droplets: A lattice Boltzmann study
Authors: Gross M. , Steinbach I. , Raabe D. , Varnik F.
Published: May 2013

The coalescence of two resting liquid droplets in a saturated vapor phase is investigated by Lattice Boltzmann simulations in two and three dimensions. We find that, in the viscous regime, the bridge radius obeys a t1/2-scaling law in time with the characteristic time scale given by the viscous time. Our results differ significantly from the predictions of existing analytical theories of viscous coalescence as well as from experimental observations. While the underlying reason for these deviations is presently unknown, a simple scaling argument is given that describes our results well.
Molecular dynamics simulation of Lorentz force microscopy in magnetic nano-disks
Authors: Dias R. A. , Mello E. P. , Coura P. Z. , Leonel S. A. , Maciel I. O. , Toscano D. , Rocha J. C. S. , Costa B. V.
Published: May 2013

In this paper, we present a molecular dynamics simulation to model the Lorentz force microscopy experiment. Experimentally, this technique consists in the scattering of electrons by magnetic structures in surfaces and gases. Here, we will explore the behavior of electrons colliding with nano-magnetic disks. The computational molecular dynamics experiment allows us to follow the trajectory of individual electrons all along the experiment. In order to compare our results with the experimental one reported in literature, we model the experimental electron detectors in a simplified way: a photo-sensitive screen is simulated in such way that it counts the number of electrons that collide at a certain position. The information is organized to give in grey scale the image information about the magnetic properties of the structure in the target. Computationally, the sensor is modeled as a square matrix in which we count how many electrons collide at each specific point after being scattered by the magnetic structure. We have used several configurations of the magnetic nano-disks to understand the behavior of the scattered electrons, changing the orientation direction of the magnetic moments in the nano-disk in several ways. Our results match very well with the experiments, showing that this simulation can become a powerful technique to help to interpret experimental results.
Analysis of polymerization with photo-Fries rearrangement in liquid crystal displays
Authors: Mizusaki Masanobu , Enomoto Satoshi , Hara Yuki , Kikuchi Hideo , Yamada Yuichiro
Published: May 2013

Polymer-sustained-alignment liquid crystal display has high potential for low power consumption, fast response, and low level of image sticking. In this study, we clarified the mechanism for a formation of a polymer layer with polymerization of the monomer 2,6-dimethacryloyl-oxy-naphthalene (2,6-DMANaph) without initiators under UV light exposure. Experimental results revealed that the polymerization of 2,6-DMANaph occurred with the generation of radicals from the monomer as reactive intermediates of a photo-Fries rearrangement. It took about 20 min for 0.5 wt. % of the monomer in the LC to convert to the polymer, indicating that the generation of the radicals derived from the reactive intermediates of the photo-Fries rearrangement is effective for the formation of the polymer layer. Voltage holding ratio of the LC cell having the polymer layer formed from the monomer 2,6-DMANaph was over 99%, which was comparably high value.
Tuning martensitic transformation and large magnetoresistance in Ni50−xCuxMn38Sn12 Heusler alloys
Authors: Jing C. , Yang Y. J. , Li Z. , Wang X. L. , Kang B. J. , Cao S. X. , Zhang J. C. , Zhu J. , Lu B.
Published: May 2013

In this paper, polycrystalline Ni50−xCuxMn38Sn12 alloys (x = 0, 2, 4, 6) were prepared. The influence of Cu doping on the martensitic transformation and magnetic properties were investigated in these alloys. Experimental results indicate that the martensitic transformation temperature decreases and the Curie temperature increases with the increasing of substitution of Cu for Ni. Therefore, the magnetic properties in both austenitic and martensitic phases could be tuned by Cu content in these alloys. In addition, magnetoresistance were also performed and discussed in detail. A large magnetoresistance (up to 39%) was obtained by the magnetic field induced reverse martensitic transformation.
Model study of combined wind and solar electricity production in Hungary
Authors: Jánosi Imre M.
Published: May 2013

Since large-scale and cheap energy storage is an unsolved problem, the main difficulty of using wind and solar electricity is caused by their intermittent nature. It is a widespread belief that the combination of the two renewable technologies generally improves the reliability and supply quality of electricity generation. Indeed, there are some locations where wind speeds are definitely larger during the nights because of the increased stability of the atmospheric boundary layer. However, a proper decision making requires to study the supposed benefits at the very location of designed installations. Here, we report on a model study, where the whole area of Hungary is evenly covered by wind generators and solar photovoltaic units of various composition and total rated power. The combined model output is compared to the recorded electricity consumption in Hungary. Our results indicate that the integrated output of combined renewable production can be definitely lower than the output of “pure” (either solar or wind) resource network of the same rated power. The main reasons are the lack of daily cycle of wind strength and the strong annual seasonality of insolation in the Carpathian basin. Benefits of combined production show up at unrealistically high rated power values which is a consequence of limited capacity factors of both renewable sources around Hungary.
Magnetic distributions of iron–(nickel zinc ferrite) nanocomposites from first order reversal curve analysis
Authors: Giri Anit K. , Hirsh Gary , Duncan Kate J. , Karna Shashi P. , Dennis C. L.
Published: May 2013

First order reversal curve measurements offer a powerful approach to quantify the magnetic property distributions in materials. Here, we have used this approach to quantify magnetic property distributions and understand the nano-scale mechanisms contributing to the magnetic anisotropy of Fe-(Ni0.5Zn0.5)Fe2O4 nanocomposites. The Fe-(Ni0.5Zn0.5)Fe2O4 nanocomposite powders were synthesized using a chemical method involving ferrite precipitation and controlled reduction which resulted in the formation of iron nanoclusters within the ferrite. Two samples with a ∼65% and ∼6% iron composition, respectively, were studied. Transmission electron microscopy measurements yielded an average particle size of ∼15 nm (∼65% Fe) and ∼60 nm (∼6% Fe). The magnetizations at 7 T for the synthesized nanocomposites (M7T = 58 Am2 kg−1 for the ∼65% Fe sample and 55 Am2 kg−1 for the ∼6% Fe sample) are close to that of the bulk saturation magnetization (∼60 Am2 kg−1) of (Ni0.5Zn0.5)Fe2O4. This is not typical in these ferrite systems, due to poor crystallinity. In our samples, the observed large M7T may result from the presence of the iron nanoclusters, as well as improved crystallinity. However, there is a slope to the magnetization at high fields which has typically been attributed to surface spin canting. This may instead be an indication of reduced crystallinity at the surface of the nanoparticles, especially in the ∼65% Fe sample. Furthermore, a difference in interactions between the ferrite and the iron nanoclusters in the two samples results in different anisotropy distributions, as evidenced by a broad transition to saturation for the first sample, and a much sharper transition for the second sample, and confirmed through first order reversal curve measurements.
Enhanced photoemission from glancing angle deposited SiOx-TiO2 axial heterostructure nanowire arrays
Authors: Dhar J. C. , Mondal A. , Singh N. K. , Chattopadhyay K. K.
Published: May 2013

The glancing angle deposition technique has been employed to synthesize SiOx-TiO2 heterostructure nanowire (NW) arrays on indium tin oxide (ITO) coated glass substrate. A field emission gun scanning electron microscopic image shows that the average diameter of the NWs is ∼50 nm. Transmission electron microscopy images show the formation of heterostructure NWs, which consist of ∼180 nm SiOx and ∼210 nm long TiO2. The selected-area electron diffraction shows the amorphous nature of the synthesized NWs, which was also confirmed by X-ray diffraction method. The main band absorption edges at 3.5 eV were found for both the SiOx-TiO2 and TiO2 NW arrays on ITO coated glass plate from optical absorption measurement. Ti3+ defect related sub-band gap transition at 2.5 eV was observed for TiO2 NWs, whereas heterostructure NWs revealed the SiOx optical band gap related transition at ∼2.2 eV. Two fold improved photon absorption as well as five times photoluminescence emission enhancement were observed for the SiOx-TiO2 multilayer NWs compared to TiO2 NWs.
A flaw in the measurement of the ion content of confined water saturated air
Authors: Wieder Irwin
Published: May 2013

Measurements on the conductivity of air are typically performed in open air. There have also been a few measurements made on confined volumes of air in contact with water with widely differing results. It is shown here that those measurements which reported large conductivities and related ion content were seriously flawed and should be disregarded.
Exothermic phenomena and hazardous gas release during thermal oxidation of mesoporous silicon powders
Authors: Loni A. , Canham L. T.
Published: May 2013

We report on the occurrence of exothermic phenomena during the thermal ramping of mesoporous silicon powders in ambient air. For furnace set temperatures of up to 800 °C, discrete exotherms occur during the initial ramp-up stage from room temperature. With an onset around 200 °C, the powder temperature rapidly self-elevates to significantly beyond the concurrent furnace baseline value and cools thereafter, in most cases over a period of a few minutes. A number of periodically spaced exotherms can occur, depending on both the weight and layout of the powder batch. A broadening and amalgamation of exotherms are observed for large batch sizes, indicating a longer-term retention of induced thermal energy, in one case with the powder temperature rising well beyond 1000 °C and being maintained for up to 80 min. We associate these exotherms with dehydrogenation processes, some of which may involve N–H as well as Si–H bonds. Oxidation is accompanied by the release of silanes and hydrogen, care therefore being required to avoid combustion of these pyrophoric gases.
A comprehensive view on performance, emission, and combustion characteristics of biodiesel-diesel blends at advanced injection timings
Authors: Murugesan A. , Subramaniam D. , Avinash A. , Nedunchezhian N.
Published: May 2013

In this article, an endeavor has been made to assess the operating characteristics of a diesel engine fuelled with methyl esters of pungamia, ethyl esters of pungamia, and ethyl esters of neem, added to diesel by percentage volume ranging from B20 to B80. The test runs on diesel fuel in the first phase of work were carried out under standard injection timing of 23° before top dead center (BTDC), so as to establish baseline for other parameters. The similar test procedures were repeated with an advanced injection timings of 26° BTDC and 28° BTDC fuelled with diesel and biodiesel–diesel blends varying from B20 to B100. Experimental results proved that the 3° advancement of injection timing from the standard injection timing proved promising outcomes for biodiesel operated engine, whereas 5° BTDC crank angle degree produced a higher exhaust gas temperature and higher levels of NOx formation.
The simultaneous effect of a fairing tower and increased blade flexibility on a downwind mounted rotor
Authors: Reiso M. , Muskulus M.
Published: May 2013

This is a parametric study on how blade and tower loads for a prototypical downwind offshore wind turbine are affected as the tower geometry and blade properties are changed. Downwind turbines have the potential to reduce the cost of energy, as blades can be more flexible and lighter, but the tower shadow induces additional structural vibrations. In order to reduce the latter, a fairing around the tower has been introduced. The length of the fairing is varied, adjusting the rotor overhang accordingly. Additionally, the blade weight and stiffness are adjusted. The blade and tower fatigue loads are, thereby, significantly decreased. In the first case, a maximum reduction of 8% and 28% (for the blade root bending and tower bottom moment, respectively) was achieved, compared to a downwind version of the National Renewable Energy Laboratory (NREL) 5 MW reference wind turbine on a monopile tower. Using softer and lighter blades resulted in loads even lower than for the conventional upwind rotor of the NREL turbine, up to 5% and 13% less for the blade and tower fatigue loads, respectively. The increased overhang increased the mean tower bending moments, suggesting that an optimal downwind turbine needs to be designed with a compromise between these fatigue and ultimate loads. The power production stayed approximately the same as that of a conventional wind turbine or was slightly higher.
Application of coherent Rayleigh-Brillouin scattering for in situ nanoparticle and large molecule detection
Authors: Shneider M. N. , Gimelshein S. F.
Published: May 2013

Feasibility of using coherent Rayleigh-Brillouin scattering for nanoparticle and large molecule diagnostics is assessed analytically and numerically through the solution of the Boltzmann equation. It has been shown that for particles of about 1 nm in diameter dispersed in a buffer gas, concentrations as small as 0.005% may be detected. The approach is expected to provide information on particle concentration with high spatial and temporal resolution.
Strain induced phase transitions in silicene bilayers: a first principles and tight-binding study
Authors: Lian Chao , Ni Jun
Published: May 2013

Using first principles and tight-binding calculations, we have investigated the structures of silicene bilayers under the isotropic tensile strain. We find that (i) the strain induce several barrierless phase transitions. (ii) After the phase transitions, the bilayer structures become planar, similar with the AA-stacking graphene bilayers, but combined with the strong covalent interlayer bonds. The tight-binding results demonstrate that this silicene bilayer is characterized by intralayer sp2 hybridization and the interlayer sp1 hybridization. (iii) The electronic properties of the silicene bilayers change from semiconducting to metallic with the increase of strain.
Control of two-dimensional growth of AlN and high Al-content AlGaN-based MQWs for deep-UV LEDs
Authors: Yang Weihuang , Li Jinchai , Lin Wei , Li Shuping , Chen Hangyang , Liu Dayi , Yang Xu , Kang Junyong
Published: May 2013

Dense and atomically flat AlN film with root-mean-square roughness value of 0.32 nm was grown on sapphire substrate at a relatively lower temperature by using a three-step epitaxy technique. On the basis of this AlN template, AlGaN-based multiple quantum wells (MQWs) with atomically flat hetero-interfaces were epitaxially grown to suppress nonradiative recombination by introducing In as a surfactant during simultaneous source supply. As a result, single intense- and narrow-peaked photoluminescence was obtained from the MQWs. Finally, the deep ultraviolet light emitting diodes with well-behaved I-V characteristic and strong electroluminescence in the range of 256–312 nm were fabricated successfully.
Identifying indicator traits for breech strike in Merino sheep in a Mediterranean environment
Authors: Greeff J. C. , Karlsson L. J. E. , Schlink A. C.
Published: May 2013

Data from 2833 unmulesed Merino lambs from 49 sires and 1535 dams that were born from 2005 to 2009, were used to identify indicator traits for breech strike in a Mediterranean environment. Sheep were managed in a normal production environment where no preventative treatments were applied to protect them from being struck by flies, but were immediately treated when found to be fly struck. Seventy-seven skin, body conformation, wool, disease and production traits that may contribute to breech strike and that could qualify as potential indicator traits were recorded on progeny at birth, weaning, post-weaning, yearling, spring and at pre- and post-hogget age at ~18 months of age. In all, 31% of ewes and 22% of rams were fly struck in the breech area between birth and hogget shearing. The heritability of and the phenotypic and genetic correlations between the potential indicator traits and breech strike were estimated. The results showed that breech strike is a heritable trait (h2 = 0.51 ± 0.10), and that the most important indicator traits for breech strike were dags, scored at any time, especially at hogget age (rg = 0.81 ± 0.15), spring (rg = 0.77 ± 0.13) or at weaning (rg = 0.64 ± 0.00), urine stain scored at weaning (rg = 0.54 ± 0.13) and marking (rg = 0.51 ± 0.15), neck wrinkle at hogget age (rg = 0.46 ± 0.13) and breech cover (rg = 0.32 ± 0.15) scored at post-weaning shearing. These traits could be used to select indirectly for breech strike resistance in a Mediterranean environment.
A Bayesian Belief Network approach to evaluating complex effects of irrigation-driven agricultural intensification scenarios on future aquatic environmental and economic values in a New Zealand catchment
Authors: Quinn John M. , Monaghan Ross M. , Bidwell Vincent J. , Harris Simon R.
Published: May 2013

Agricultural intensification often has complex effects on a wide range of environmental and economic values, presenting planners with challenging decisions for optimising sustainable benefits. Bayesian Belief Networks (BBNs) can be used as a decision-support tool for evaluating the influence of development scenarios across a range of values. A BBN was developed to guide decisions on water abstraction and irrigation-driven land use intensification in the Hurunui River catchment, New Zealand. The BBN examines the combined effects of different irrigation water sources and four land development scenarios, with and without a suite of on-farm mitigations, on ground and surface water quality, key socioeconomic values (i.e. farm earnings and jobs, and contribution to regional gross domestic production (GDP)) and aquatic values (i.e. salmon, birds, waterscape, contact recreation, periphyton and invertebrates). It predicts high farm earnings, jobs and regional GDP with 150% increase in irrigated area, but a range of positive and negative aquatic environmental outcomes, depending on the location of water storage dams and the application of a suite of on-farm mitigations. This BBN synthesis of a complex system enhanced the ability to include aquatic values alongside economic and social values in land-use and water resource planning and decision making, and has influenced objective setting in Hurunui planning processes.
Managing pollutant inputs from pastoral dairy farming to maintain water quality of a lake in a high-rainfall catchment
Authors: Wilcock Robert J. , Monaghan Ross M. , McDowell Richard W. , Verburg Piet , Horrox Jonny , Chagué-Goff Catherine , Duncan Maurice J. , Rutherford Alison , Zemansky Gil , Scarsbrook Mike R. , Wright-Stow Aslan E. , Howard-Williams Clive , Cotton Sue
Published: May 2013

A study (2004–11) of a dairy catchment stream entering an oligotrophic lake in an area of very high rainfall (~5 m year–1) yielded median concentrations of total nitrogen (TN), total phosphorus (TP), suspended sediment (SS) and Escherichia coli (E. coli) of 0.584, 0.074 and 3.7 g m–3, and 405/100 mL (most probable number method), respectively. Trend analysis indicated significant (P < 0.01) decreases for TN (–0.08 ± 0.02 g m–3 year–1), TP (–0.01 ± 0.005 g m–3 year–1) and SS (–0.45 ± 0.14 g m–3 year–1) and were partly attributable to improved exclusion of cattle from the stream. Water balance calculations indicated that approximately one-half the rainfall left as deep drainage that by-passed catchment outlet flow recorders. Estimates of catchment yields for TN were improved by taking into account groundwater hydrology and concentrations from well samples. Storm-flow monitoring inflows exceeding the 97.5th percentile contributed ~40% of total loads leaving the catchment so that specific yields for SS, TN and TP augmented by groundwater inputs and storm flows were ~960, 45 and 7 kg ha–1 year–1, respectively. These compared well with modelled results for losses from dairy farms in the catchment of 40–60 kg N ha–1 year–1 and 5–6 kg P ha–1 year–1 and indicated that attenuation losses were relatively small.
Envisioning the future of transhumant pastoralism through participatory scenario planning: a case study in Spain
Authors: Oteros-Rozas Elisa , Martín-López Berta , López César A. , Palomo Ignacio , González José A.
Published: May 2013

Transhumance is a practice of nomadic pastoralism that was once common in Mediterranean Europe. This livestock-rearing system is associated with the maintenance of cultural landscapes and the delivery of a wide range of ecosystem services. Although transhumance is still practised in Spain on a small scale, its future is highly uncertain because of socioeconomic constraints and other drivers of change. A participatory scenario-planning exercise with 68 participants, including shepherds, decision-makers, veterinarians, environmental experts, intermediaries from the wool and meat markets, and researchers, was used to envision plausible futures for transhumance and to enlighten policy-making for the maintenance of this practice along the Conquense Drove Road, one of the largest foot-based transhumant social-ecological networks still in use in Spain. Specifically, the aims were to: (1) analyse the drivers influencing the future of transhumance, (2) depict the current situation of transhumance, (3) envision future scenarios for this activity, (4) analyse ecosystem services’ trade-offs between different scenarios and their effect on human wellbeing, and (5) provide some insights for policy-making related to the maintenance of transhumance. Four plausible future scenarios were built, each showing clear trade-offs in the delivery of 19 ecosystem services, such as food, fibre, ecological connectivity, soil fertility, air quality, fire prevention, cultural identity, local ecological knowledge and cultural exchanges, as well as the different dimensions of human wellbeing. As a result of the participatory process, nine management strategies were identified for the maintenance of transhumance. Priority was given to the implementation of payment schemes for ecosystem services, the enhancement of social capital among transhumants and institutional coordination, the improvement of product marketing, and the restoration and conservation of drove roads. Finally, the implications of the current reform of the Common Agricultural Policy in the European Union for the maintenance of transhumance are discussed.
Perceptions and deflections: associations between attitudes towards people with hepatitis C and testing for hepatitis C among Australian gay and bisexual men
Authors: Brener Loren , Ellard Jeanne , Murphy Dean , Callander Denton
Published: May 2013

Background
Research indicates that the incidence of hepatitis C (HCV) among HIV-positive men who have sex with men (MSM) is increasing. Although injecting drug use remains the predominant means of transmission of HCV in the developed world, there is evidence of sexual transmission of HCV among MSM. Stigma associated with HCV has been shown to negatively impact HCV testing and health-seeking behaviour. There is little research that addresses attitudes towards HCV testing among this population. Methods: The current exploratory study focussed on HCV knowledge, HCV testing, sexual practices, perceptions of HCV risk and attitudes towards people with HCV among Australian MSM. The sample consisted of 590 men who completed an online survey. Results: The findings suggest that attitudinal factors related to HCV were associated with HCV testing behaviour. The more negatively respondents felt about people with HCV, the less likely they were to have ever had an HCV test. Behavioural risk factors related to sexual practices (i.e. is condom use and sexual risk activities) were not associated with HCV testing. Testing for HCV was associated with HIV-positive status, more knowledge about HCV and a greater likelihood of ever having injected drugs. Conclusions: The attitudes of MSM towards those who inject drugs are negative, mirroring that of society more generally. Furthermore, these attitudes, coupled with a lack of knowledge of the risk of sexual transmission of HCV among gay men, especially those who are HIV-positive, may act to prevent routine HCV testing among some MSM at potential risk of acquiring HCV.