bluuebunny/crossref_metadata_2025 huggingface dataset:
Continuum kinetic and multi-fluid simulations of classical sheaths
Authors: Cagas P. , Hakim A. , Juno J. , Srinivasan B.
Published: February 2017

The kinetic study of plasma sheaths is critical, among other things, to understand the deposition of heat on walls, the effect of sputtering, and contamination of the plasma with detrimental impurities. The plasma sheath also provides a boundary condition and can often have a significant global impact on the bulk plasma. In this paper, kinetic studies of classical sheaths are performed with the continuum kinetic code, Gkeyll, which directly solves the Vlasov-Maxwell equations. The code uses a novel version of the finite-element discontinuous Galerkin scheme that conserves energy in the continuous-time limit. The fields are computed using Maxwell equations. Ionization and scattering collisions are included; however, surface effects are neglected. The aim of this work is to introduce the continuum kinetic method and compare its results with those obtained from an already established finite-volume multi-fluid model also implemented in Gkeyll. Novel boundary conditions on the fluids allow the sheath to form without specifying wall fluxes, so the fluids and fields adjust self-consistently at the wall. The work presented here demonstrates that the kinetic and fluid results are in agreement for the momentum flux, showing that in certain regimes, a multi-fluid model can be a useful approximation for simulating the plasma boundary. There are differences in the electrostatic potential between the fluid and kinetic results. Further, the direct solutions of the distribution function presented here highlight the non-Maxwellian distribution of electrons in the sheath, emphasizing the need for a kinetic model. The densities, velocities, and the potential show a good agreement between the kinetic and fluid results. However, kinetic physics is highlighted through higher moments such as parallel and perpendicular temperatures which provide significant differences from the fluid results in which the temperature is assumed to be isotropic. Besides decompression cooling, the heat flux is shown to play a role in the temperature differences that are observed, especially inside the collisionless sheath.
Broadening effects on opacity calculation of CH plasmas
Authors: Ghorashi Seyed Alaeddin , Mahdavi Mohammad
Published: February 2017

Opacity is a function of the temperature and electron density of plasma. The plasma density can be determined by measurements of Stark-broadened K-shell spectral lines. The purpose of this work is to obtain a more detailed structure of opacity with regard to broadening effects. For this aim, the opacity frequency dependency and mean opacity of mixed plasmas are calculated under local thermodynamic equilibrium (LTE) conditions. The LTE state in inertial confinement fusion occurs when the collisional deexcitation rate from the upper level to the lower level greatly exceeds the spontaneous decay rate. Since the thermal radiation can be absorbed by the CH-ablator, by studying the behavior of the CH Polystyrene opacity, one can obtain the temperature and density of the plasma in investigations of matter found in stellar interiors, inertial fusion implosions, and Z pinches as a diagnostic technique. The main aspect of diagnostic application is spectrum broadening. The final results show that the Stark-broadened line shape is dependent on the density. Also, it is shown that the resonance peak and spectrum broadening of the opacity spectrum of a mixed plasma such as the CH-plasma is larger than a single atom plasma such as Carbon.
Controlling of strong tunable THz emission with optimal incommensurate multi-color laser field
Authors: Zhang Lei , Wang Guo-Li , Zhao Song-Feng , Zhou Xiao-Xin
Published: February 2017

Based on the photocurrent model, we study terahertz (THz) emission from argon plasmas induced by incommensurate-frequency two- and three-color laser fields. In order to enhance the THz radiation at an arbitrary frequency efficiently, a genetic algorithm is applied to search for the optimum laser parameters. For the longer two-color field, our optimizations show that the THz tunability is mainly determined by two laser frequencies, which approximately meets the law Ω = 2ω1−ω2. However, for the shorter laser pulse, the tunability of the THz wave with lower frequency also depends on the relative phase. To control the tunable THz emission, we systematically investigated how to generate the stronger THz wave with the shorter spectrum width using the optimal synthesized waveform. We found that the THz intensity can be enhanced by about an order with three-color field compared with the two-color cases. We also show that the tunable single ultrashort THz pulses can be obtained by using an optimized 50-fs two-color pulse.
Vibronic enhancement of excitation energy transport: Interplay between local and non-local exciton-phonon interactions
Authors: Lee Myeong H. , Troisi Alessandro
Published: February 2017

It has been reported in recent years that vibronic resonance between vibrational energy of the intramolecular nuclear mode and excitation-energy difference is crucial to enhance excitation energy transport in light harvesting proteins. Here we investigate how vibronic enhancement induced by vibronic resonance is influenced by the details of local and non-local exciton-phonon interactions. We study a heterodimer model with parameters relevant to the light-harvesting proteins with the surrogate Hamiltonian quantum dynamics method in a vibronic basis. In addition, the impact of field-driven excitation on the efficiency of population transfer is compared with the instantaneous excitation, and the effect of multi-mode vibronic coupling is presented in comparison with the coupling to a single effective vibrational mode. We find that vibronic enhancement of site population transfer is strongly suppressed with the increase of non-local exciton-phonon interaction and increasing the number of strongly coupled high-frequency vibrational modes leads to a further decrease in vibronic enhancement. Our results indicate that vibronic enhancement is present but may be much smaller than previously thought and therefore care needs to be taken when interpreting its role in excitation energy transport. Our results also suggest that non-local exciton-phonon coupling, which is related to the fluctuation of the excitonic coupling, may be as important as local exciton-phonon coupling and should be included in any quantum dynamics model.
A simplified model for the determination of current-voltage characteristics of a high pressure hydrogen plasma arc
Authors: Gueye P. , Cressault Y. , Rohani V. , Fulcheri L.
Published: February 2017

This paper focuses on the modeling of a hydrogen arc column at very high pressure (20 bar). The problem is solved from Elenbaas-Heller equation where the radiation is carefully considered with the net emission coefficient. The absorption spectrum requires the integration of background continuum, molecular bands, and line spectra. This work directly aims to predict the electric current-voltage characteristics which is key for the design of new processes. We propose also a new analytic solution which generalizes the channel model of electric arc to the case when the volume radiation makes a significant contribution to the energy balance. The presented formalism allows a better determination of the plasma thickness parameter Rp for net emission coefficient method in cylindrical arcs and gives satisfactory results in comparison to earlier experimental works on high pressure hydrogen plasma.
Computational insights into the concomitant changes of hollow interior
evolution in [SbnAunSbn]m (n=3, 4, 5, 6; m=
-3, -2, -1, -2) complex
Authors: Zhu Tingting , Ning Ping , Tang Lihong , Li Kai , Bao Shuangyou , Jin Xu , Song Xin , Zhang Xiuying , Han Shuang
Published: February 2017

A series of novel all-metal sandwich species, [SbnAunSbn]m (n= 3, 4, 5, 6; m= -3, -2, -1, -2), are carefully designed and are systematically investigated in term of structure, bonding nature, stability, and potential application. These results show that [SbnAunSbn]m (n=3, 4, 5, 6; m= -3, -2, -1, -2), have local minimum values on their potential energy surfaces. For the Sb-Sb and Sb-Au bond, they are obviously covalent features, while in Au-Au, there is a typical aurophilic interaction. Furthermore, these species present expected stability owing to the positive dissociation energy, great Egap, ionization potential (IP), aromaticity and perfected mechanical stability. Interestingly, [Sb5Au5Sb5]- and [Sb6Au6Sb6]2- are aromatic, while both [Sb3Au3Sb3]3- and [Sb4Au4Sb4]2- possess conflicting aromaticity. And all the title species hold tube aromaticty and δ aromaticty. prediction The application suggests that the Sb site is favorable for absorbing CO in the units, and [Sb3Au3Sb3]3- is more suitable than others; CO is absorbed by the p-p interaction between the C and Sb atoms.
Use of thermocouples and argon line broadening for gas temperature measurement in a radio frequency atmospheric microplasma jet
Authors: Doyle S. J. , Xu K. G.
Published: February 2017

This paper presents the use of thermocouples and line broadening of argon 2p-1s emission lines for the measurement of gas temperature of an atmospheric argon microplasma jet. The measured temperatures are compared with rotational spectra fitting of OH (A-X) and N2 (C-B) emission. An rf microplasma jet with two electrical configurations and different temperature ranges was used. The calculated gas temperatures with thermocouples, argon lines, and OH ranged from 290 to 423 K and 393-510 K for the two configurations, depending on the rf power. The temperature from fitting the N2 spectra overestimated the gas temperatures in both configurations (593-680 and 664-853 K). The non-nitrogen temperature measurements agree well with each other within the measurement uncertainty. The results show that not all optical emission temperature methods are appropriate and the accuracy of argon line broadening is dependent on the device configuration. The results also show that conventional thermocouples are surprisingly accurate and viable for these plasmas.
A facile synthesis of CH3NH3PbBr3 perovskite quantum dots and their application in flexible nonvolatile memory
Authors: Yang Kaiyu , Li Fushan , Veeramalai Chandrasekar Perumal , Guo Tailiang
Published: February 2017

In this work, we present a simple and facile one step synthesis strategy to prepare CH3NH3PbBr3 perovskite quantum dots and apply them into the nonvolatile memory. Resistive switching phenomenon was observed in this perovskite quantum dots and polymer composite based memory device with the ON/OFF current ratio larger than 103 as well as good reproducibility and reliability. Flexible memory was also demonstrated, and a possible resistance switching mechanism was discussed. Our work paves a way for the application of organolead halide perovskite quantum dots in flexible and transparent nonvolatile memories.
Effect of secondary electron emission on nonlinear dust acoustic wave propagation in a complex plasma with negative equilibrium dust charge
Authors: Bhakta Subrata , Ghosh Uttam , Sarkar Susmita
Published: February 2017

In this paper, we have investigated the effect of secondary electron emission on nonlinear propagation of dust acoustic waves in a complex plasma where equilibrium dust charge is negative. The primary electrons, secondary electrons, and ions are Boltzmann distributed, and only dust grains are inertial. Electron-neutral and ion-neutral collisions have been neglected with the assumption that electron and ion mean free paths are very large compared to the plasma Debye length. Both adiabatic and nonadiabatic dust charge variations have been separately taken into account. In the case of adiabatic dust charge variation, nonlinear propagation of dust acoustic waves is governed by the KdV (Korteweg-de Vries) equation, whereas for nonadiabatic dust charge variation, it is governed by the KdV-Burger equation. The solution of the KdV equation gives a dust acoustic soliton, whose amplitude and width depend on the secondary electron yield. Similarly, the KdV-Burger equation provides a dust acoustic shock wave. This dust acoustic shock wave may be monotonic or oscillatory in nature depending on the fact that whether it is dissipation dominated or dispersion dominated. Our analysis shows that secondary electron emission increases nonadiabaticity induced dissipation and consequently increases the monotonicity of the dust acoustic shock wave. Such a dust acoustic shock wave may accelerate charge particles and cause bremsstrahlung radiation in space plasmas whose physical process may be affected by secondary electron emission from dust grains. The effect of the secondary electron emission on the stability of the equilibrium points of the KdV-Burger equation has also been investigated. This equation has two equilibrium points. The trivial equilibrium point with zero potential is a saddle and hence unstable in nature. The nontrivial equilibrium point with constant nonzero potential is a stable node up to a critical value of the wave velocity and a stable focus above it. This critical value increases with increasing secondary electron emission. Thus, in the presence of secondary electron emission, higher velocity shock waves are monotonic. The results have been numerically explained considering the presence of Al2O3 dust grains in the plasma.
Microplasma generation by slow microwave in an electromagnetically induced transparency-like metasurface
Authors: Tamayama Yasuhiro , Sakai Osamu
Published: February 2017

Microplasma generation using microwaves in an electromagnetically induced transparency (EIT)-like metasurface composed of two types of radiatively coupled cut-wire resonators with slightly different resonance frequencies is investigated. A microplasma is generated in either of the gaps of the cut-wire resonators as a result of strong enhancement of the local electric field associated with resonance and slow microwave effects. The threshold microwave power for plasma ignition is found to reach a minimum at the EIT-like transmission peak frequency, where the group index is maximized. A pump–probe measurement of the metasurface reveals that the transmission properties can be significantly varied by varying the properties of the generated microplasma near the EIT-like transmission peak frequency and the resonance frequency. The electron density of the microplasma is roughly estimated to be of order 1×1010 cm−3 for a pump power of 15.8 W by comparing the measured transmission spectrum for the probe wave with the numerically calculated spectrum. In the calculation, we assumed that the plasma is uniformly generated in the resonator gap, that the electron temperature is 2 eV, and that the elastic scattering cross section is 20×10−16 cm2.
Sensitive and predictable separation of microfluidic droplets by size using in-line passive filter
Authors: Ding Ruihua , Ung W. Lloyd , Heyman John A. , Weitz David A.
Published: February 2017

Active manipulation of droplets is crucial in droplet microfluidics. However, droplet polydispersity decreases the accuracy of active manipulation. We develop a microfluidic “droplet filter” that accurately separates droplets by size. The droplet filter has a sharp size cutoff and is capable of distinguishing droplets differing in volume by 20%. A simple model explains the behavior of the droplets as they pass through the filter. We show application of the filter in improving dielectric sorting efficiency.
Photon-induced selenium migration in TiSe2
Authors: Lioi David B. , Gosztola David J. , Wiederrecht Gary P. , Karapetrov Goran
Published: February 2017

TiSe2 is a member of the transition metal dichalcogenide family of layered van der Waals materials that exhibits some distinct electronic and optical properties. Here, we perform the Raman spectroscopy and microscopy studies on single crystal TiSe2 to investigate the thermal and photon-induced defects associated with the diffusion of selenium to the surface. Additional phonon peaks near 250 cm−1 are observed in the laser-irradiated regions that are consistent with the formation of amorphous and nanocrystalline selenium on the surface. Temperature dependent studies of the threshold temperature and laser intensity necessary to initiate selenium migration to the surface show an activation barrier for the process of 1.55 eV. The impact of these results on the properties of strongly correlated electron states in TiSe2 is discussed.
Effectiveness of oxide trench array as a passive temperature compensation structure in AlN-on-silicon micromechanical resonators
Authors: Xie Qingyun , Wang Nan , Sun Chengliang , Randles Andrew B. , Singh Pushpapraj , Zhang Xiaolin , Gu Yuandong
Published: February 2017

This Letter presents the effectiveness of an oxide trench array (OTA) as a passive temperature compensation structure for aluminum nitride on silicon (AlN-on-Si) quasi-surface acoustic wave (SAW) micromechanical resonators over a wide temperature range. Two types of devices, namely, those with OTA and their reference counterparts without OTA, are designed, fabricated, and characterized over a wide temperature range of 360 °C. Experimental results show that the resonator with OTA has a first-order temperature coefficient of frequency (TCf1) at room temperature (20 °C) of 6.66 ppm/°C, which is lower than that of the reference device without OTA by 72% in magnitude. A high turnover temperature of 197 °C is achieved. Furthermore, the second-order temperature stability of the device has also improved. OTA is experimentally demonstrated to be an effective structure for passive temperature compensation, hence paving the way for using AlN-on-Si resonators as ultrasonic sensors or timing devices in ruggedized environments where the large fluctuation in temperature places stringent demands on temperature stability.
Josephson junction microwave modulators for qubit control
Authors: Naaman O. , Strong J. A. , Ferguson D. G. , Egan J. , Bailey N. , Hinkey R. T.
Published: February 2017

We demonstrate Josephson junction based double-balanced mixer and phase shifter circuits operating at 6–10 GHz and integrate these components to implement both a monolithic amplitude/phase vector modulator and an I/Q quadrature mixer. The devices are actuated by flux signals, dissipate no power on chip, exhibit input saturation powers in excess of 1 nW, and provide cryogenic microwave modulation solutions for integrated control of superconducting qubits.
Boron doped GaN and InN: Potential candidates for spintronics
Authors: Fan S. W. , Huang X. N. , Yao K. L.
Published: February 2017

The full potential linearized augmented plane wave method together with the Tran-Blaha modified Becke-Johnson potential is utilized to investigate the electronic structures and magnetism for boron doped GaN and InN. Calculations show the boron substituting nitrogen (BN defects) could induce the GaN and InN to be half-metallic ferromagnets. The magnetic moments mainly come from the BN defects, and each BN defect would produce the 2.00 μB total magnetic moment. The electronic structures indicate the carriers-mediated double exchange interaction plays a crucial role in forming the ferromagnetism. Positive chemical pair interactions imply the BN defects would form the homogeneous distribution in GaN and InN matrix. Moderate formation energies suggest that GaN and InN with BN defects could be fabricated experimentally.
Enhancement in red emission at room temperature from europium doped ZnO nanowires by 1,10 phenanthroline-europium interface induced resonant excitations
Authors: Dhara Soumen , Raychaudhuri A. K.
Published: February 2017

We show that europium doped ZnO nanowires after surface modification with organic ligand, 1,10 phenanthroline (phen) leads to strong red emission at 613 nm which is a characteristic emission from the atomic levels of Eu3+. Surface modification with phen leads to formation of phenanthroline-europium interface on the surface of the nanowires due to attachment of Eu3+ ions. After an optimized surface modification with phen, intensity of both the UV emission (band edge) and red emission improved by two orders of magnitude at room temperature. We observed multiple energy transfer pathways to the energy levels of Eu3+ ions through the phenanthroline-europium interface, which found to be very effective to the significant enhancement of emission from the dopant Eu3+. This study shows a new insight in to the energy transfer process from phen to the europium doped ZnO system.
Impact of phase transition sequence on the electrocaloric effect in Pb(Nb,Zr,Sn,Ti)O3 ceramics
Authors: Xu Zunping , Fan Zhongming , Liu Xiaoming , Tan Xiaoli
Published: February 2017

The phase transition sequence in PbZrO3-based ceramics can be readily altered by chemical modification. In Pb0.99Nb0.02[(Zr0.57Sn0.43)0.92Ti0.08]0.98O3 (PNZST 43/8/2), the sequence is ferroelectric–antiferroelectric–paraelectric during heating, while in Pb0.99Nb0.02(Zr0.85Sn0.13Ti0.02)0.98O3 (PNZST 13/2/2), it is antiferroelectric–ferroelectric–paraelectric during heating. The electrocaloric effect associated with the antiferroelectric ↔ ferroelectric phase transition is studied in both ceramics via indirect measurement. PNZST 43/8/2 is observed to display a positive electrocaloric effect; in contrast, PNZST 13/2/2 exhibits a negative effect.
Effect of distribution of electric field on low-pressure gas breakdown
Authors: Fu Yangyang , Yang Shuo , Zou Xiaobing , Luo Haiyun , Wang Xinxin
Published: February 2017

A low-pressure gas breakdown in a gap of the non-uniform electric field between two plane-parallel electrodes was studied. The experiments were specially designed to neatly separate the effect of a centered dielectric tube in between the electrodes on the breakdown from the effect of the electric field distribution determined by the electrode geometry on the breakdown. For a given electrode radius and an interelectrode distance, when the diameter of the centered dielectric tube in between the electrodes is smaller, the breakdown voltage is lower, which is most possibly as a result of the flashover more easily happening along the surface of the smaller tube on which the more charged particles are accumulated. When the dielectric tube in between the electrodes is removed, the breakdown voltage depends not only on the product of gas pressure and gap length but also on the aspect ratio of the gas gap, i.e., Ub = f(pd, d/r). Furthermore, Ub = f(pd, d/r) was proved to automatically fulfill two necessary conditions for the similar discharges in the non-uniform electric field, which implies that Ub = f(pd, d/r) is an expression of the similarity theorem in the breakdown of a gap between two plane-parallel electrodes and confirms Townsend's prediction that the general similarity theorem can be applied equally to the breakdowns in non-uniform fields.
Novel switching design for finite-time stabilization: Applications to memristor-based neural networks with time-varying delay
Authors: Cai Zuo-Wei , Huang Jian-Hua , Huang Li-Hong
Published: February 2017

The aim of this paper is to provide a novel switching control design to solve finite-time stabilization issues of a discontinuous or switching dynamical system. In order to proceed with our analysis, we first design two kinds of switching controllers: switching adaptive controller and switching state-feedback controller. Then, we apply the proposed switching control technique to stabilize the states of delayed memristor-based neural networks (DMNNs) in finite time. Based on a famous finite-time stability theorem, the theory of differential inclusion and the generalized Lyapunov functional method, some sufficient conditions are obtained to guarantee the finite-time stabilization control of DMNNs. The feedback functions of our model are allowed to be unbounded, and the upper bounds of the settling time for stabilization are also given. Finally, the validity of designed method and the theoretical results are illustrated by numerical examples.
Optically controllable nanobreaking of metallic nanowires
Authors: Zhou Lina , Lu Jinsheng , Yang Hangbo , Luo Si , Wang Wei , Lv Jun , Qiu Min , Li Qiang
Published: February 2017

Nanobreaking of nanowires has shown its necessity for manufacturing integrated nanodevices as nanojoining does. In this letter, we develop a method for breaking gold pentagonal nanowires by taking advantage of the photothermal effect with a 532 nm continuous-wave (CW) laser. The critical power required for nanobreaking is much lower for perpendicular polarization than that for parallel polarization. By controlling the polarization and the power of the irradiation light for nanobreaking, the nanowires can be cut into segments with gap widths ranging from dozens of nanometers to several micrometers. This CW light-induced single point nanobreaking of metallic nanowires provides a highly useful and promising method in constructing nanosystems.
Time-multiplexed amplification in a hybrid-less and coil-less Josephson parametric converter
Authors: Abdo Baleegh , Chavez-Garcia Jose M. , Brink Markus , Keefe George , Chow Jerry M.
Published: February 2017

Josephson parametric converters (JPCs) are superconducting devices capable of performing nondegenerate, three-wave mixing in the microwave domain without losses. One drawback limiting their use in scalable quantum architectures is the large footprint of the auxiliary circuit needed for their operation, in particular, the use of off-chip, bulky, broadband hybrids and magnetic coils. Here, we realize a JPC that eliminates the need for these bulky components. The pump drive and flux bias are applied in the Hybrid-Less, Coil-Less (HLCL) device through an on-chip, lossless, three-port power divider and an on-chip flux line, respectively. We show that the HLCL design considerably simplifies the circuit and reduces the footprint of the device while maintaining a comparable performance to state-of-the-art JPCs. Furthermore, we exploit the tunable bandwidth property of the JPC and the added capability of applying alternating currents to the flux line in order to switch the resonance frequencies of the device, hence demonstrating time-multiplexed amplification of microwave tones that are separated by more than the dynamical bandwidth of the amplifier. Such a measurement technique can potentially serve to perform a time-multiplexed, high-fidelity readout of superconducting qubits.
Effect of large magnetic islands on screening of external magnetic perturbation fields at slow plasma flow
Authors: Li L. , Liu Y. Q. , Huang X. , Luan Q. , Zhong F. C.
Published: February 2017

A toroidal resistive magneto-hydrodynamic plasma response model, involving large magnetic islands, is proposed and numerically investigated, based on local flattening of the equilibrium pressure profile near a rational surface. It is assumed that such islands can be generated near the edge of the tokamak plasma, due to the penetration of the resonant magnetic perturbations, used for the purpose of controlling the edge localized mode. Within this model, it is found that the local flattening of the equilibrium pressure helps to mitigate the toroidal curvature induced screening effect [Glasser et al., Phys. Fluids 7, 875 (1975)]—the so called Glasser-Greene-Johnson screening, when the local toroidal flow near the mode rational surface is very slow (for example, as a result of mode locking associated with the field penetration). The saturation level of the plasma response amplitude is computed, as the plasma rotation frequency approaches zero. The local modification of the plasma resistivity inside the magnetic island is found to also affect the saturation level of the plasma response at vanishing flow.
Mapping the cyclic plastic zone to elucidate the mechanisms of crack tip deformation in bulk metallic glasses
Authors: Scudino S. , Shahid R. N. , Escher B. , Stoica M. , Li B. S. , Kruzic J. J.
Published: February 2017

Developing damage-tolerant bulk metallic glasses (BMGs) requires knowledge of the physical mechanisms governing crack propagation. While fractography suggests that fatigue crack propagation occurs in an incremental manner, conclusive evidence of alternating crack tip blunting and resharpening is lacking. By mapping the strain fields in both the monotonic and cyclic plastic zones, it is shown that the characteristic compressive stresses required to resharpen the crack tip are developed in a BMG upon unloading. This result confirms the mechanism of fatigue crack propagation in BMGs. Broader implications of these findings are that the effect of shear banding is rather diffuse and plastic deformation ahead of a stress concentration, such as a crack tip, appears to extend well beyond the extent of visible shear bands on the sample surface.
Turning the undesired voids in silicon into a tool: In-situ fabrication of free-standing 3C-SiC membranes
Authors: Khazaka Rami , Michaud Jean François , Vennéguès Philippe , Alquier Daniel , Portail Marc
Published: February 2017

In this contribution, we present a method to form free-standing cubic silicon carbide (3C-SiC) membranes in-situ during the growth stage. To do so, we exploit the presence of voids in the silicon (Si) epilayer underneath the 3C-SiC membrane, in stark contrast to the conventional view of voids as defects. The shape and the size of the 3C-SiC membranes can be controlled by a preceding patterning step of the Si epilayer. Afterwards, by controlling the expansion of voids in Si, the structured sacrificial layer is consumed during the 3C-SiC growth step. Consequently, the membranes are grown and released simultaneously in a single step process. This straightforward technique is expected to markedly simplify the fabrication process of membranes by reducing the fabrication duration and cost. Furthermore, it helps to overcome several technical issues and presents the cornerstone for micro and nano-electromechanical systems applications, profiting from the outstanding properties of cubic silicon carbide.
Crystal structure and magnetic properties of Li1-xNaxFePO4 based on Mössbauer spectroscopy
Authors: Ko Byung Ug , Choi Hyunkyung , Kouh Taejoon , Kim Sam Jin , Kim Chul Sung
Published: February 2017

The Na-doped Li1-xNaxFePO4 (x = 0.0, 0.01, 0.05, 0.1, 1) samples were synthesized by solid-state reaction method and investigated with X-ray diffractometer (XRD), vibrating sample magnetometer (VSM) and Mössbauer spectrometer. Based on XRD patterns, analyzed by the Rietveld refinement method, Li1-xNaxFePO4 samples were determined to have an orthorhombic structure with space group Pnma. From the temperature-dependent magnetization curve, we have determined the Néel temperature (TN) and observed abnormal antiferromagnetic behavior. Below TN, the Mössbauer spectra appeared to have asymmetrical line-shapes and were analyzed with one set of eight absorption lines. The Mössbauer spectra also showed the Néel temperature (TN) as well as the abnormal antiferromagnetic behavior as in the temperature-dependent magnetization curve. The abnormal antiferromagnetic behavior is expected to be originated from the spin reorientation and the corresponding spin reorientation temperature (TS) is determined experimentally.
The correlation of material properties and deposition condition of ZnON thin films
Authors: Gao Haibo , Zhang Xiaodan , Zhao Ying , Yan Baojie
Published: February 2017

Amorphous and nanocrystalline Zinc Oxynitride (nc-ZnON) has been found to be one kind of potential materials for thin film transistors in the application of advanced display because of their high carrier mobility and low persistent photocurrent. We report a systematic study of ZnON properties and their correlation to the deposition conditions in a reactive sputtering process using a metallic Zn target in a gas mixture of Ar, N2 and O2. The most sensitive parameter to the material properties is O2 and N2 flow rates. At given N2 and Ar flow rates, the ZnON materials show polycrystalline ZnO properties when a relatively high O2 flow rate is used; become a mixture of ZnO and Zn3N2 with a nanocrystalline structure when a medium O2 flow rate is used; and finally show polycrystalline Zn3N2 properties when a small or no O2 flow rate is used. The RF power also shows a strong influence on the material properties. At a given gas mixture, a low RF power produces polycrystalline ZnO-like materials and a high power produces polycrystalline Zn3N2-like materials. At an optimized medium RF power, the material shows nc-ZnON properties. Finally, under the optimized condition, the nc-ZnON films are made with an optical bandgap of 1.3-1.5 eV, electron mobility above 80 cm2/V.s and electron density of 1x1018 cm-3, which are suitable for high quality TFTs in advanced display application.
Comparison of microhabitat use in young regrowth and unlogged forest by the eastern pygmy-possum (Cercartetus nanus)
Authors: Law Bradley , Chidel Mark , Britton Alf , Threlfall Caragh
Published: February 2017

We describe microhabitat use and response to disturbance by the eastern pygmy-possum (Cercartetus nanus) in heathy dry sclerophyll forest using spool-and-line-tracking. We compared unlogged forest with forest regenerating four years after selective logging. Structural and floristic attributes were scored along spool lines and compared with a random line for each possum. We found that possums (n = 23) selected areas based on both structural and floristic attributes. Possums selected dense understorey, especially that comprising flowering hairpin banksia (Banksia spinulosa) and Gymea lily (Doryanthes excelsa). Fallen logs were not selected by nocturnally active possums. Spool lines in regrowth forest had less eucalypt cover and more understorey cover (e.g. D. excelsa and B. spinulosa) than unlogged forest. Conversely, cover of Banksia serrata was less in regrowth than unlogged forest. Spool lines were commonly found both at ground level (mean = 52–57% of lengths) and above the ground (43–48% of lengths). There was no difference in the mean spool height between the logging treatments (regrowth: 0.47 ± 0.14 m; unlogged: 0.49 ± 0.10 m; ± s.e.). Overall, our results suggest that the dense, flowering understorey that regenerates after selective logging is suitable for use and is the primary attribute selected by active pygmy-possums.
Influence of zeolite (clinoptilolite) supplementation on characteristics of digestion and ruminal fermentation of steers fed a steam-flaked corn-based finishing diet
Authors: Urías-Estrada J. D. , López-Soto M. A. , Barreras A. , Aguilar-Hernández J. A. , González-Vizcarra V. M. , Estrada-Angulo A. , Zinn R. A. , Mendoza G. D. , Plascencia A.
Published: February 2017

Four Holstein steers (328 ± 14 kg) with ruminal and duodenal cannulas were used in a 4 × 4 Latin square design to examine the effect of level of zeolite supplementation (0, 10, 20 or 30 g clinoptilolite-Ca/kg of diet) in a steam-flaked corn-based finishing diet on the characteristics of ruminal fermentation and nutrient digestion. Zeolite was top-dressed with the basal diet at time of feeding; therefore, intake of organic matter (OM), neutral detergent fibre (NDF), starch and N was equal in all treatments. Zeolite supplementation did not affect site and extent of digestion of N or NDF. Zeolite linearly decreased (P < 0.01) NH3-N flow to duodenum, but did not affect duodenal flow of microbial N, feed N, or microbial efficiency. Inclusion of zeolite linearly increased (P = 0.02) ruminal OM digestion and tended (linear, P = 0.08) to increase ruminal digestion of starch. Zeolite supplementation increased (linear effect, P < 0.01) faecal excretion of ash, resulting in decreased total tract DM digestion (linear effect, P = 0.04). However, total tract digestion of OM tended to increase (P = 0.06) with increasing zeolite supplementation. Thus, dilution of the diet with zeolite did not depress dietary digestible energy. There were no treatment effects on ruminal pH. Total ruminal volatile fatty acid concentration tended (P = 0.08) to increase as zeolite increased. Zeolite supplementation decreased ruminal molar proportion of acetate and increased molar proportion of propionate (linear effect, P < 0.01), resulting in decreased (linear effect, P < 0.01) of acetate: propionate ratio. Supplementation with zeolite at levels of up to 30 g of zeolite/kg of diet may enhance ruminal OM digestion, largely due to the tendency of increased ruminal starch digestion. Zeolite supplementation altered ruminal volatile fatty acid molar proportions (decreased acetate : propionate ratio), and therefore may have an positive impact on energy efficiency.
DNA ploidy variation and distribution in the Lepidosperma costale complex (Cyperaceae): implications for conservation and restoration in a biodiversity hotspot
Authors: Wallace Mark J. , Guja Lydia K. , Jouault Marie A. , Fuller Kathy A. , Barrett Russell L. , Krauss Siegfried L. , Barrett Matthew D.
Published: February 2017

Intraspecific ploidy variation is an important component of angiosperm biodiversity; however, this variation is rarely considered in conservation programs. This is of particular concern when conservation activities include augmentation, reintroduction or ecological restoration because there are potentially negative consequences when ploidy variants are unintentionally mixed within populations. We surveyed regional ploidy variation in the Lepidosperma costale Nees species complex (Schoeneae: Cyperaceae) in the South West Australian Floristic Region, an international biodiversity hotspot. Several L. costale sensu lato populations are threatened by iron-ore extraction, including the rare L. gibsonii R.L.Barrett, and these populations are the subject of ecological restoration programs. The DNA ploidy of 2384 individuals from 28 populations across the range of the species complex was determined and four DNA ploidy levels were discovered, namely, diploid, triploid, tetraploid and pentaploid. Diploids and tetraploids were the most common cytotypes and were largely geographically segregated, even at an exhaustively studied contact zone. Triploids were found at a low frequency in two populations. The rarity of triploids suggests substantial interploidy sterility, and that mixing of ploidy variants should, therefore, be avoided when restoring L. costale s.l. populations. These data provide a guide for L. costale s.l. germplasm collection and suggest that polyploidy may be an important driver of diversification in these sedges.
Changes in smoking, drinking, overweight and physical inactivity in young Australian women 1996–2013
Authors: Powers Jennifer R. , Loxton Deborah , Anderson Amy E. , Dobson Annette J. , Mishra Gita D. , Hockey Richard , Brown Wendy J.
Published: February 2017

Issue addressed

Smoking, risky drinking, overweight and obesity, and physical inactivity are health‐risk factors (HRFs) that contribute significantly to morbidity worldwide. Several initiatives have been introduced over the past two decades to reduce these HRFs. This paper examines changes in the prevalence of HRFs in young women (aged 18–23 years) between 1996 and 2013, overall and within demographic groups.

Methods

Data from two cohorts of the Australian Longitudinal Study on Women's Health, born in 1973–78 (n = 14 247) and 1989–95 (n = 17 012) were weighted to provide national estimates. Prevalence ratios were used to compare HRFs in 2013 relative to 1996.

Results

In 1996, 32% were current smokers, 38% were risky drinkers, 22% were overweight or obese and 7% were physically inactive. In 2013, corresponding estimates were 19%, 35%, 33% and 6%. Between 1996 and 2013, overall smoking prevalence decreased, but remained over 43% among least educated women. Overweight and obesity increased in all demographic groups.

Conclusions

The findings suggest that only smoking, which has been the subject of changes in taxation, legislation and regulation, declined significantly, in all except the least educated women. In contrast, the prevalence of overweight and obesity, which has largely been addressed through awareness campaigns and voluntary actions by the food industry, increased markedly in all demographic sub‐groups.

So what?

The findings show that comprehensive health promotion interventions, such as those for tobacco control, are successful (but may still be ineffective among less educated women). In contrast the measures to control population weight gain among young women have been futile so far.
Persistent or long-term coronavirus infection in Australian bats
Authors: Smith Craig
Published: February 2017

When the World Health Organization declared the end of the global outbreak of severe acute respiratory syndrome (SARS) on the 5 July 2003, more than 8000 cases with over 800 fatalities had been reported in 32 countries worldwide and financial costs to the global economy were close to $US40 billion1,2. Coronaviruses were identified as being responsible for the outbreaks of both SARS and Middle East respiratory syndrome (MERS, the latter in 2013). Subsequently, bats (order Chiroptera) were identified as the natural hosts for a large number of novel and genetically diverse coronaviruses, including the likely ancestors to SARS-like and MERS-like coronaviruses3–8.
Ecologists, economics and politics: problems and contradictions in applying neoliberal ideology to nature conservation in Australia
Authors: Boon Paul I. , Prahalad Vishnu
Published: February 2017

In a recent Forum Essay in Pacific Conservation Biology, the well known ecologist Harry Recher argued that over the past three decades Australia had experienced a ‘failure of science’ and a concomitant ‘death of nature’. In this essay we examine some of the propositions put forward by Recher (2015), with particular reference to the role played by neoliberal ideology in nature conservation in Australia. Since the early 1980s the neoliberal value system has effectively shaped a new paradigm for nature conservation in Australia with its own language, tools and institutions, and through such a process has redefined nature in its own terms. We focus on two of the most significant neoliberal, free-market mechanisms – (1) monetary valuation of biodiversity and of ecosystem services, and (2) the provision of complementary areas to offset losses of high-quality habitat – and show how they have come to dominate policy development and on-ground activities in wetland management and conservation in Australia. Despite the wide reach of neoliberal ideology, ecologists and conservation biologists seem largely unaware of its practical implications. In some cases, such as with offset programs and with carbon valuation, they have become complicit with the ruling ideology, without, it seems to us, being fully aware of their involvement, tacit or explicit, or of the likely connotations of that participation. Hedging the future of wetland conservation to ‘market-driven environmentalism’ is simply an expected overreach in the broader context of neoliberal economic and political ideology, and provides rich grounds for a critique in support of a more considered approach to nature conservation.
Sensitivity of soil organic carbon to grazing management in the semi-arid rangelands of south-eastern Australia
Authors: Orgill S. E. , Waters C. M. , Melville G. , Toole I. , Alemseged Y. , Smith W.
Published: February 2017

This study compared the effects of grazing management on soil organic carbon (OC) stocks in the semi-arid rangelands of New South Wales, Australia. A field survey was conducted at three locations (Brewarrina, Cobar–North and Cobar–South), with paired sites of long-term (>8 years) rotational grazing management and continuously grazed pastures (either set stocked or no stocking). At each location, soil OC, carbon (C) fractions, soil nitrogen (N) and microsite and site factors (including ground cover and woody vegetation) were measured. The control of total grazing pressure (TGP) through rotational grazing and exclusion fencing did not increase soil C stocks compared with continuous grazing for the majority of comparisons. However, in some parts of the landscape, higher soil C stock was found with TGP control, for example on the ridges (21.6 vs 13.3 t C ha–1 to 0.3 m). C stocks increased with litter and perennial ground cover and with close proximity to trees. At Brewarrina, C stocks were positively affected by perennial plant cover (P < 0.001) and litter (P < 0.05), whereas at Cobar–North and Cobar–South C stocks were positively affected by the presence of trees (P < 0.001), with higher C stocks in close proximity to trees, and with increasing litter cover (P < 0.01). The present study demonstrates that natural resource benefits, such as increased perennial cover, can be achieved through controlling TGP in the rangelands but increases in soil C may be limited in certain parts of the landscape. These findings also highlight that interactions between managed and unmanaged TGP and microsite factors, such as ground cover and proximity to woody vegetation, need to be considered when evaluating the role of changed grazing management on soil C.
Microtrolling: an Economical Method to Nonlethally Sample and Tag Juvenile Pacific Salmon at Sea
Authors: Duguid William D. P. , Juanes Francis
Published: February 2017

Mortality of juvenile Pacific salmon Oncorhynchus spp. in their first marine year is hypothesized to be a primary driver of variable recruitment in a changing ocean. Much contemporary research focuses on diet, distribution, growth, and survival during this period; however, existing methods of capturing juvenile salmon at sea are expensive and may be limited by topography and tidal currents. We assessed the feasibility of using a small vessel and modified recreational fishing gear (microtrolling) to nonlethally capture, sample, and tag juvenile Chinook Salmon O. tshawytscha during their first marine summer. Sampling was conducted in the Strait of Georgia, British Columbia, from August to October 2014. We captured 168 Chinook Salmon, 13 Coho Salmon O. kisutch, and 1 Chum Salmon O. keta in 72 h of active fishing; Chinook Salmon CPUE was greatest between 6 and 19 m and increased late in the afternoon and on the flood tide. To assess short‐term mortality related to capture, PIT tagging, and sampling, we maintained 66 microtroll‐captured Chinook Salmon (41 of which were PIT‐tagged) overnight in a net pen; only one mortality and one incidence of tag loss were observed. Microtrolling proved effective for systematically sampling juvenile Chinook Salmon across depths and habitats. Unlike alternative methods of sampling juvenile Pacific salmon (trawling and purse seining), the utility of microtrolling is likely limited to studies of Chinook Salmon and possibly Coho Salmon. The low cost of this method has potential to facilitate participation of frequently excluded stakeholders, including First Nations and community groups, in marine research on juvenile Pacific salmon.

Received June 10, 2016; accepted November 1, 2016 Published online February 21, 2017
Texture modification of magnesium alloys during electropulse treatment
Authors: Zhang Ruikun , Li Xiaohui , Kuang Jie , Li Xiaopei , Tang Guoyi
Published: February 2017

Differential speed rolling (DSR) at room temperature has been carried out on two Mg–1Gd and Mg–1Zn–1Gd rare-earth-containing magnesium alloys with different thickness reductions. The cold-rolled samples were selected to investigate the microstructure and texture evolution during the electropulse treatment (EPT). Both grain refinement and texture modification have been achieved for the three cold-rolled samples, which were accompanied by nucleation and nuclei growth during EPT. The recrystallisation process could be attributed to enhanced climb activity of dislocations by EPT, which produces not only a thermal effect but also an athermal effect. Compared with Mg–1Gd, Mg–1Zn–1Gd shows a smaller recrystallisation rate, which should be related to the solute segregation and could be one of the reasons for the texture modification of the alloy.

This paper is part of a themed issue on Materials in External Fields.