bluuebunny/crossref_metadata_2025 huggingface dataset:
Improved V/f control strategy for microgrids based on master–slave control mode
Authors: Wang Can , Yang Ping , Ye Chao , Wang Yuewu , Xu Zhirong
Published: May 2016

The V/f control adopted by the master power supply has problems of slow dynamic response, poor anti‐interference ability in response to micro‐source output power fluctuations and loads abrupt change. Aiming at problems of the output voltage mentioned above, an improved V/f control strategy based on compound control is proposed in this study. The improved V/f control strategy is composed of two parts, feedforward compensation and robust feedback control. The design of the feedforward compensator is realised by the method of approximate full compensation. The design of the robust feedback controller is transformed into solving a convex optimisation problem with linear matrix inequality constraints and linear objective functions. The designed V/f control strategy is verified by a variety of comparative tests. Test comparisons show that the controller can get better voltage output characteristics, dynamic characteristics and robustness in response to micro‐source output power fluctuations, loads abrupt change or non‐linear loads and unbalanced loads.
Approach for ambipolar behaviour suppression in tunnel FET by workfunction engineering
Authors: Nigam Kaushal , kondekar Pravin , Sharma Dheeraj
Published: May 2016

A dual material control gate tunnel field effect transistor (TFET) for asymmetric doping at source and drain regions is proposed. The gate consists of three segment different workfunctions ϕ1, ϕ2, and ϕ3, which are named as tunnelling gate (M1), control gate (M2), and auxiliary gate (M3), respectively. Forward to this, three possible combinations of ϕ1, ϕ2 and ϕ3 to maintain the dual workfunctionality of the device (ϕ2 = ϕ3 > ϕ1, ϕ1 = ϕ2 > ϕ3, ϕ1 = ϕ3 < ϕ2) were considered. Further, the comparison of these possible combinations are performed with conventional TFET (ϕ1 = ϕ2 = ϕ3). Among these ϕ1 = ϕ3 < ϕ2, generates most optimum results in terms of suppression of ambipolar behaviour, and enhancement in ON state current (ION) of the device. The proposed device shows significant improvement in terms of ION (1.66 × 10−5A/μ m for SiO2), ION/IOFF (7.22 × 1011), and sub‐threshold swing (∼19 mV/decade) as compared with conventional and the dual material TFET devices. Further, the analysis of analogue/RF performance is performed for the devices showing optimum performance in terms of suppression of ambipolar behaviour.
Pediatric Meningeal Tumors of the Sylvian Fissure Region without Dural Attachment: A Series of Three Patients and Review of the Literature
Authors: Donovan Daniel , Thavapalan Varoon
Published: May 2016

Pediatric meningeal tumors are rare, but those in the region of the sylvian fissure without dural attachment are extremely rare, with only 24 previously reported cases in the world literature. In this series, we report two additional cases of sylvian fissure meningioma without dural attachment and one case of perisylvian meningioangiomatosis in the medial temporal lobe. All three patients presented with complex partial seizures, but the diagnosis was delayed in each case because the symptoms were misinterpreted to be behavioral rather than epileptic. The seizures were eventually confirmed with electroencephalogram, and subsequent imaging showed enhancing masses within the sylvian fissure region that were at least partially calcified in all three cases. Each patient underwent craniotomy. In the first case, gross total resection was achieved, and in the second case, a small residual portion of tumor was densely calcified and adherent to the middle cerebral artery branches. Both of these were World Health Organization (WHO) grade I meningiomas. The third patient underwent biopsy and limited resection of meningioangiomatosis. No dural attachments were noted in any of the tumors, but one of the meningiomas was intraparenchymal in location, surrounding the sylvian fissure in both the frontal and temporal lobes, which has been described in only a small number of these cases previously. The patients underwent pre- and postsurgical neuropsychiatric testing and did not experience any significant cognitive deficits. At 10-year follow-up, the patient who had gross total resection of the tumor has had no recurrence and is seizure-free without anticonvulsant medications. The incompletely resected intraparenchymal meningioma in the second patient recurred after 5 years, however, and at repeat surgery was found to have transformed to a WHO grade II tumor. Radiation therapy was delivered and the tumor has been stable for 2 years, but the patient continues to have occasional seizures despite medication. The patient with meningioangiomatosis has had no further growth and has excellent control of seizures but remains on medication. We review the clinical presentation of these rare tumors and discuss the treatment, outcomes, and possible relationship of meningiomas to meningioangiomatosis.
Hamiltonian surface charges using external sources
Authors: Troessaert Cédric
Published: May 2016

In this work, we interpret part of the boundary conditions as external sources in order to partially solve the integrability problem present in the computation of surface charges associated to gauge symmetries in the hamiltonian formalism. We start by describing the hamiltonian structure of external symmetries preserving the action up to a transformation of the external sources of the theory. We then extend these results to the computation of surface charges for field theories with non-trivial boundary conditions.
Self-diffusiophoretic colloidal propulsion near a solid boundary
Authors: Mozaffari Ali , Sharifi-Mood Nima , Koplik Joel , Maldarelli Charles
Published: May 2016

Self-propelled, chemically powered colloidal locomotors are swimmers designed to transverse small scale landscapes in a range of applications involving micropumping, sensing, and cargo transport. Although applications can require precise navigation and onboard steering mechanisms, here we examine by calculation how locomotors through their hydrodynamic interaction can navigate along a boundary. We adopt an engine model consisting of a spherical Janus colloid coated with a symmetrical catalyst cap, which converts fuel into a product solute. The solute is repelled from the colloid through a repulsive interaction, which occurs over a distance much smaller than the swimmer radius. Within this thin interaction layer, a concentration difference develops along the surface, which generates a pressure gradient as pressure balances the interaction force of the solute with the surface. The pressure gradient drives a slip flow towards the high concentration, which propels the particle oppositely, away from product accumulation (self-diffusiophoresis). To study boundary guidance, the motion near an infinite no-slip planar wall that does not adsorb solute is obtained by analytical solution of the solute conservation and the Stokes equations using bispherical coordinates. Several regimes of boundary interaction unfold: When the colloid is oriented with its cap axisymmetrically facing the wall, it is repelled by the accumulation of solute in the gap between the swimmer and the wall. With the cap opposite to the wall, the swimmer moves towards the wall by the repulsion from the solute accumulating on the cap side, but very large caps accumulate solute in the gap, and the motor stops. For oblique approach with the cap opposite to the wall and small cap sizes, the swimmer is driven to the wall by accumulation on the cap side, but rotates as it approaches the wall, and eventually scatters as the cap reorients and faces the wall. For a swimmer approaching obliquely with a larger cap (again facing away from the wall), boundary navigation results as the accumulation of product in the gap suppresses rotation and provides a normal force, which directs the swimmer to skim along the surface at a fixed distance and orientation or to become stationary. We also demonstrate how gravity can force transitions between skimming and stationary states.
Simulation of bubble expansion and collapse in the vicinity of a free surface
Authors: Koukouvinis P. , Gavaises M. , Supponen O. , Farhat M.
Published: May 2016

The present paper focuses on the numerical simulation of the interaction of laser-generated bubbles with a free surface, including comparison of the results with instances from high-speed videos of the experiment. The Volume Of Fluid method was employed for tracking liquid and gas phases while compressibility effects were introduced with appropriate equations of state for each phase. Initial conditions of the bubble pressure were estimated through the traditional Rayleigh Plesset equation. The simulated bubble expands in a non-spherically symmetric way due to the interference of the free surface, obtaining an oval shape at the maximum size. During collapse, a jet with mushroom cap is formed at the axis of symmetry with the same direction as the gravity vector, which splits the initial bubble to an agglomeration of toroidal structures. Overall, the simulation results are in agreement with the experimental images, both quantitatively and qualitatively, while pressure waves are predicted both during the expansion and the collapse of the bubble. Minor discrepancies in the jet velocity and collapse rate are found and are attributed to the thermodynamic closure of the gas inside the bubble.
Force measurement using strain-gauge balance in a shock tunnel with long test duration
Authors: Wang Yunpeng , Liu Yunfeng , Luo Changtong , Jiang Zonglin
Published: May 2016

Force tests were conducted at the long-duration-test shock tunnel JF12, which has been designed and built in the Institute of Mechanics, Chinese Academy of Sciences. The performance tests demonstrated that this facility is capable of reproducing a flow of dry air at Mach numbers from 5 to 9 at more than 100 ms test duration. Therefore, the traditional internal strain-gauge balance was considered for the force tests use in this large impulse facility. However, when the force tests are conducted in a shock tunnel, the inertial forces lead to low-frequency vibrations of the test model and its motion cannot be addressed through digital filtering because a sufficient number of cycles cannot be found during a shock tunnel run. The post-processing of the balance signal thus becomes extremely difficult when an averaging method is employed. Therefore, the force measurement encounters many problems in an impulse facility, particularly for large and heavy models. The objective of the present study is to develop pulse-type sting balance by using a strain-gauge sensor that can be applied in the force measurement of 100 ms test time, especially for the force test of the large-scale model. Different structures of the S-series (i.e., sting shaped balances) strain-gauge balance are proposed and designed, and the measuring elements are further optimized to overcome the difficulties encountered during the measurement of aerodynamic force in a shock tunnel. In addition, the force tests were conducted using two large-scale test models in JF12 and the S-series strain-gauge balances show good performance in the force measurements during the 100 ms test time.
Development and performance of a suprathermal electron spectrometer to study auroral precipitations
Authors: Ogasawara Keiichi , Grubbs Guy , Michell Robert G. , Samara Marilia , Stange Jason L. , Trevino John A. , Webster James , Jahn Jörg-Micha
Published: May 2016

The design, development, and performance of Medium-energy Electron SPectrometer (MESP), dedicated to the in situ observation of suprathermal electrons in the auroral ionosphere, are summarized in this paper. MESP employs a permanent magnet filter with a light tight structure to select electrons with proper energies guided to the detectors. A combination of two avalanche photodiodes and a large area solid-state detector (SSD) provided 46 total energy bins (1 keV resolution for 3−20 keV range for APDs, and 7 keV resolution for >20 keV range for SSDs). Multi-channel ultra-low power application-specific integrated circuits are also verified for the flight operation to read-out and analyze the detector signals. MESP was launched from Poker Flat Research Range on 3 March 2014 as a part of ground-to-rocket electrodynamics-electrons correlative experiment (GREECE) mission. MESP successfully measured the precipitating electrons from 3 to 120 keV in 120-ms time resolution and characterized the features of suprathermal distributions associated with auroral arcs throughout the flight. The measured electrons were showing the inverted-V type spectra, consistent with the past measurements. In addition, investigations of the suprathermal electron population indicated the existence of the energetic non-thermal distribution corresponding to the brightest aurora.
High power microwave source with a three dimensional printed metamaterial slow-wave structure
Authors: French David M. , Shiffler Don
Published: May 2016

For over the last decade, the concept of metamaterials has led to new approaches for considering the interaction of radiation with complex structures. However, practical manifestations of such a device operating at high power densities have proven difficult to achieve due to the resonant nature of metamaterials and the resultant high electric fields, which place severe constraints on manufacturing the slow wave structures. In this paper, we describe the first experimental manifestation of a high power microwave device utilizing a metallic slow wave structure (metamaterial-like) fabricated using additive manufacturing. The feasibility of utilizing additive manufacturing as a technique for building these relatively complicated structures has thus been demonstrated. The MW class microwave source operates in the C-band and shows frequency tunablility with electron beam voltage. The basic electromagnetic characteristics of this device, the construction using additive manufacturing, and the basic performance as a microwave oscillator are considered. Due to the tunable nature of the device, it shows promise not only as an oscillator but also as a microwave amplifier. Therefore, the dispersive characteristics and a discussion of the anticipated gain is included as it relates to an amplifier configuration.
Character of intermolecular interaction in pyridine-argon complex: Ab initio potential energy surface, internal dynamics, and interrelations between SAPT energy components
Authors: Makarewicz Jan , Shirkov Leonid
Published: May 2016

The pyridine-Ar (PAr) van der Waals (vdW) complex is studied using a high level ab initio method. Its structure, binding energy, and intermolecular vibrational states are determined from the analytical potential energy surface constructed from interaction energy (IE) values computed at the coupled cluster level of theory with single, double, and perturbatively included triple excitations with the augmented correlation consistent polarized valence double-ζ (aug-cc-pVDZ) basis set complemented by midbond functions. The structure of the complex at its global minimum with Ar at a distance of 3.509 Å from the pyridine plane and shifted by 0.218 Å from the center of mass towards nitrogen agrees well with the corresponding equilibrium structure derived previously from the rotational spectrum of PAr. The PAr binding energy De of 392 cm−1 is close to that of 387 cm−1 calculated earlier at the same ab initio level for the prototypical benzene-Ar (BAr) complex. However, under an extension of the basis set, De for PAr becomes slightly lower than De for BAr. The ab initio vdW vibrational energy levels allow us to estimate the reliability of the methods for the determination of the vdW fundamentals from the rotational spectra. To disclose the character of the intermolecular interaction in PAr, the symmetry-adapted perturbation theory (SAPT) is employed for the analysis of different physical contributions to IE. It is found that SAPT components of IE can be approximately expressed in the binding region by only two of them: the exchange repulsion and dispersion energy. The total induction effect is negligible. The interrelations between various SAPT components found for PAr are fulfilled for a few other complexes involving aromatic molecules and Ar or Ne, which indicates that they are valid for all rare gas (Rg) atoms and aromatics.
Preferential site occupancy of alloying elements in TiAl-based phases
Authors: Holec David , Reddy Rajeev K. , Klein Thomas , Clemens Helmut
Published: May 2016

First principles calculations are used to study the preferential occupation of ternary alloying additions into the binary Ti-Al phases, namely, γ-TiAl, α2-Ti3Al, βo-TiAl, and B19-TiAl. While the early transition metals (TMs, group IVB, VB, and VIB elements) prefer to substitute for Ti atoms in the γ-, α2-, and B19-phases, they preferentially occupy Al sites in the βo-TiAl. Si is, in this context, an anomaly, as it prefers to sit on the Al sublattice for all four phases. B and C are shown to prefer octahedral Ti-rich interstitial positions instead of substitutional incorporation. The site preference energy is linked with the alloying-induced changes of energy of formation, hence alloying-related (de)stabilisation of the phases. We further show that the phase-stabilisation effect of early TMs on βo-phase has a different origin depending on their valency. Finally, an extensive comparison of our predictions with available theoretical and experimental data (which is, however, limited mostly to the γ-phase) shows a consistent picture.
Intermediate vibrational coordinate localization with harmonic coupling constraints
Authors: Hanson-Heine Magnus W. D.
Published: May 2016

Optimized normal coordinates can significantly improve the speed and accuracy of vibrational frequency calculations. However, over-localization can occur when using unconstrained spatial localization techniques. The unintuitive mixtures of stretching and bending coordinates that result can make interpreting spectra more difficult and also cause artificial increases in mode-coupling during anharmonic calculations. Combining spatial localization with a constraint on the coupling between modes can be used to generate coordinates with properties in-between the normal and fully localized schemes. These modes preserve the diagonal nature of the mass-weighted Hessian matrix to within a specified tolerance and are found to prevent contamination between the stretching and bending vibrations of the molecules studied without a priori classification of the different types of vibration present. Relaxing the constraint can also be used to identify which normal modes form specific groups of localized modes. The new coordinates are found to center on more spatially delocalized functional groups than their fully localized counterparts and can be used to tune the degree of vibrational correlation energy during anharmonic calculations.
Distinguishing Raman from strongly coupled Brillouin amplification for short pulses
Authors: Jia Qing , Barth Ido , Edwards Matthew R. , Mikhailova Julia M. , Fisch Nathaniel J.
Published: May 2016

Plasma-based amplification by strongly coupled Brillouin scattering has recently been suggested for the compression of a short seed laser to ultrahigh intensities in sub-quarter-critical-density plasmas. However, by employing detailed spectral analysis of particle-in-cell simulations in the same parameter regime, we demonstrate that, in fact, Raman backscattering amplification is responsible for the growth and compression of the high-intensity, leading spike, where most of the energy compression occurs, while the ion mode only affects the low-intensity tail of the amplified pulse. The critical role of the initial seed shape is identified. A number of subtleties in the numerical simulations are also pointed out.
Faceted particles: An approach for the enhancement of the elasticity and the yield-stress of magnetorheological fluids
Authors: Vereda Fernando , Segovia-Gutiérrez Juan Pablo , de Vicente Juan , Hidalgo-Alvarez Roque
Published: May 2016

Faceted particles have been used to prepare dilute magnetorheological (MR) fluids with enhanced aggregate strength. The measured storage modulus of these suspensions is significantly larger than that of the MR fluids prepared with spherical particles, and comparable to that of the rod-based fluids, whereas no sign of formation of a percolated system was observed at the largest concentration we studied (5 vol. %). Finite element method calculations confirm that the more intimate surface contacts between faceted particles lead to larger magnetic interparticle forces than the point contacts associated with the spherical particles. The contribution of friction is expected to be significant but remains unknown.
A molecular dynamics study of the effect of thermal boundary conductance on thermal transport of ideal crystal of n-alkanes with different number of carbon atoms
Authors: Rastgarkafshgarkolaei Rouzbeh , Zeng Yi , Khodadadi J. M.
Published: May 2016

Phase change materials such as n-alkanes that exhibit desirable characteristics such as high latent heat, chemical stability, and negligible supercooling are widely used in thermal energy storage applications. However, n-alkanes have the drawback of low thermal conductivity values. The low thermal conductivity of n-alkanes is linked to formation of randomly oriented nano-domains of molecules in their solid structure that is responsible for excessive phonon scattering at the grain boundaries. Thus, understanding the thermal boundary conductance at the grain boundaries can be crucial for improving the effectiveness of thermal storage systems. The concept of the ideal crystal is proposed in this paper, which describes a simplified model such that all the nano-domains of long-chain n-alkanes are artificially aligned perfectly in one direction. In order to study thermal transport of the ideal crystal of long-chain n-alkanes, four (4) systems (C20H42, C24H50, C26H54, and C30H62) are investigated by the molecular dynamics simulations. Thermal boundary conductance between the layers of ideal crystals is determined using both non-equilibrium molecular dynamics (NEMD) and equilibrium molecular dynamics (EMD) simulations. Both NEMD and EMD simulations exhibit no significant change in thermal conductance with the molecular length. However, the values obtained from the EMD simulations are less than the values from NEMD simulations with the ratio being nearly three (3) in most cases. This difference is due to the nature of EMD simulations where all the phonons are assumed to be in equilibrium at the interface. Thermal conductivity of the n-alkanes in three structures including liquid, solid, and ideal crystal is investigated utilizing NEMD simulations. Our results exhibit a very slight rise in thermal conductivity values as the number of carbon atoms of the chain increases. The key understanding is that thermal transport can be significantly altered by how the molecules and the nano-domains are oriented in the structure rather than by the length of the n-alkane molecules.
A structure of CdS/CuxS quantum dots sensitized solar cells
Authors: Shen Ting , Bian Lu , Li Bo , Zheng Kaibo , Pullerits Tönu , Tian Jianjun
Published: May 2016

This work introduces a type of CdS/CuxS quantum dots (QDs) as sensitizers in quantum dot sensitized solar cells by in-situ cationic exchange reaction method where CdS photoanode is directly immersed in CuCl2 methanol solution to replace Cd2+ by Cu2+. The p-type CuxS layer on the surface of the CdS QDs can be considered as hole transport material, which not only enhances the light harvesting of photoanode but also boosts the charge separation after photo-excitation. Therefore, both the electron collection efficiency and power conversion efficiency of the solar cell are improved from 80% to 92% and from 1.21% to 2.78%, respectively.
Continuous waves probing in dynamic acoustoelastic testing
Authors: Scalerandi M. , Gliozzi A. S. , Ait Ouarabi M. , Boubenider F.
Published: May 2016

Consolidated granular media display a peculiar nonlinear elastic behavior, which is normally analysed with dynamic ultrasonic testing exploiting the dependence on amplitude of different measurable quantities, such as the resonance frequency shift, the amount of harmonics generation, or the break of the superposition principle. However, dynamic testing allows measuring effects which are averaged over one (or more) cycles of the exciting perturbation. Dynamic acoustoelastic testing has been proposed to overcome this limitation and allow the determination of the real amplitude dependence of the modulus of the material. Here, we propose an implementation of the approach, in which the pulse probing waves are substituted by continuous waves. As a result, instead of measuring a time-of-flight as a function of the pump strain, we study the dependence of the resonance frequency on the strain amplitude, allowing to derive the same conclusions but with an easier to implement procedure.
Controlled heat flux measurement across a closing nanoscale gap and its comparison to theory
Authors: Ma Y. , Ghafari A. , Budaev B. V. , Bogy D. B.
Published: May 2016

We present here a controlled measurement of heat flux across a closing gap that is initially less than 10 nm wide between two solid surfaces at different temperatures. The measured heat transfer is compared with our published theoretical analyses of this phenomenon that show thermal radiation dominates the heat transfer for gaps wider than about 1–2 nm, but phonon conduction dominates between 1 and 2 nm and contact. The experiments employ a thermal actuator mounted on a rocking base block for coarse positioning that supplies Joule heating to an embedded element to cause thermal expansion of a localized region for less than 10 nm spacing control, together with an embedded near-surface resistive temperature sensor to measure its temperature change due to the heat flux across the gap. The measured results are in general agreement with the theoretical predictions, and they also agree with common sense expectations. This paper not only shows nano-scale heat transfer measurement across a closing gap, it also lends additional strong support to the validity of the referenced theoretical developments. The proposed experimental approach can provide support to design of future devices for nano-scale heat transfer measurement.
Computer-automated tuning of semiconductor double quantum dots into the single-electron regime
Authors: Baart T. A. , Eendebak P. T. , Reichl C. , Wegscheider W. , Vandersypen L. M. K.
Published: May 2016

We report the computer-automated tuning of gate-defined semiconductor double quantum dots in GaAs heterostructures. We benchmark the algorithm by creating three double quantum dots inside a linear array of four quantum dots. The algorithm sets the correct gate voltages for all the gates to tune the double quantum dots into the single-electron regime. The algorithm only requires (1) prior knowledge of the gate design and (2) the pinch-off value of the single gate T that is shared by all the quantum dots. This work significantly alleviates the user effort required to tune multiple quantum dot devices.
Study of energy band discontinuity in NiZnO/ZnO heterostructure using X-ray photoelectron spectroscopy
Authors: Dewan Sheetal , Tomar Monika , Goyal Anshu , Kapoor A. K. , Tandon R. P. , Gupta Vinay
Published: May 2016

A heterostructure based on ZnO and Ni doped ZnO (NiZnO) thin films has been prepared on c-plane sapphire substrate by pulsed laser deposition technique. X-ray photo electron spectroscopy has been utilized to study the energy band discontinuities, i.e., valence band offset (ΔEv) and conduction band offset (ΔEc) at the interface of NiZnO and ZnO thin films. A type-II band alignment is identified at the interface of prepared heterostructure from the computed data, which is attractive for the realization of efficient optoelectronic devices.
Impact of built-in potential across LaFeO3/SrTiO3 heterojunctions on photocatalytic activity
Authors: Nakamura Kentarou , Mashiko Hisanori , Yoshimatsu Kohei , Ohtomo Akira
Published: May 2016

Polar-nonpolar interfaces between insulating LaFeO3 (LFO) and semiconducting SrTiO3 (STO) were investigated to elucidate effects of built-in potential on photocarrier dynamics during water oxidation reactions. The LFO films were grown on the TiO2- and SrO-terminated (001) Nb-doped STO substrates by using pulsed-laser deposition. The photocurrent-voltage curves varied depending on the interface termination. Potential profiles across the interface were established from these curves as well as capacitance-voltage curves. The presence of a depletion (accumulation) region near the SrO- (TiO2-) terminated interface facilitates (suppresses) the extraction of photocarriers generated in STO. On the other hand, the difference in the built-in potential in LFO barely reflects the magnitude of the photocurrent.
Revealing flow behaviors of metallic glass based on activation of flow units
Authors: Ge T. P. , Wang W. H. , Bai H. Y.
Published: May 2016

Atomic level flow plays a critical role in the mechanical behavior of metallic glass (MG) while the connection between the flow and the heterogeneous microstructure of the glass remains unclear. We describe the heterogeneity of MGs as the elastic matrix with “inclusions” of nano-scale liquid-like flow units, and the plastic flow behavior of MGs is considered to be accommodated by the flow units. We show that the model can explain the various deformation behaviors, the transformation from inhomogeneous deformation to homogeneous flow upon strain rate or temperature, and the deformation map in MGs, which might provide insights into the flow mechanisms in glasses and inspiration for improving the plasticity of MGs.
Proton beam shaped by “particle lens” formed by laser-driven hot electrons
Authors: Zhai S. H. , Shen B. F. , Wang W. P. , Zhang H. , He S. K. , Lu F. , Zhang F. Q. , Deng Z. G. , Dong K. G. , Wang S. Y. , Zhou K. N. , Xie N. , Wang X. D. , Zhang L. G. , Huang S. , Liu H. J. , Zhao Z. Q. , Gu Y. Q. , Zhang B. H. , Xu Z. Z.
Published: May 2016

Two-dimensional tailoring of a proton beam is realized by a “particle lens” in our experiment. A large quantity of electrons, generated by an intense femtosecond laser irradiating a polymer target, produces an electric field strong enough to change the trajectory and distribution of energetic protons flying through the electron area. The experiment shows that a strip pattern of the proton beam appears when hot electrons initially converge inside the plastic plate. Then the shape of the proton beam changes to a “fountain-like” pattern when these hot electrons diffuse after propagating a distance.
High dense structure boosts stability of antiferroelectric phase of NaNbO3 polycrystalline ceramics
Authors: Chao Lumen , Hou Yudong , Zheng Mupeng , Zhu Mankang
Published: May 2016

For NaNbO3, its intrinsic phase transition sequence is still controversial in literature. In this paper, high-densified NaNbO3 ceramics derived from mechanochemical nanostructures presented a stabilized antiferroelectric characteristic. In addition to the Tc of 360 °C, another diffuse dielectric anomaly appeared around 100 °C, which did not vanish after O2 annealing treatment. The fine structure analysis indicated that this dielectric anomaly belongs to first order phase transition from P phase to Q phase. Moreover, even exerting the strong electric field close to breakdown value, the normal ferroelectric loops cannot be induced, proving the large free energy difference between these two phases.
How do we capture the emergency nurse practitioners’ contribution to value in health service delivery?
Authors: Jennings Natasha , Lutze Matthew , Clifford Stuart , Maw Michael
Published: May 2016

The emergency nurse practitioner is now a well established and respected member of the healthcare team. Evaluation of the role has focused on patient safety, effectiveness and quality of care outcomes. Comparisons of the role continue to focus on cost, with findings based on incomplete and almost impossible to define, recognition of contribution to service delivery by paralleled practitioners. Currently there is no clear definition as to how nurse practitioners contribute to value in health service delivery. Robust and rigorous research needs to be commissioned taking into consideration the unique hybrid nature of the emergency nurse practitioner role and focusing on the value they contribute to health care delivery.
Effects of variable-intensity logging and the influence of habitat variables on the distribution of the Greater Glider Petauroides volans in montane forest, southeastern New South Wales
Authors: P. Kavanagh Rodney , P. Kavanagh Rodney
Published: May 2016

Populations of arboreal marsupials were assessed in forests before and after logging at different levels of logging intensity to determine the sensitivity of these species to habitat disturbance. The logging treatments imposed were unlogged controls and two intensities of integrated logging for sawlogs and woodchips. The mean basal area of trees retained in logged blocks ranged from 83% to 35% of pre-logging levels. The objective of the study was to develop better methods for managing arboreal marsupials within the wood production forests of southeastern New South Wales. Seven species of arboreal marsupials were recorded during the study, but the Greater Glider Petauroides volans was the only species recorded in sufficient numbers for analysis (86% of all records). No significant differences were observed between the treatments in counts of the Greater Glider before and after logging. However, given the observed trend and an a priori expectation of a decline in numbers of this species following intensive logging, a one-tailed statistical test was applied which resulted in a significant difference at P = 0.08 for the contrast between the unlogged controls and the most intensively logged treatment. The existence of a threshold in logging intensity within the range of 21 % to 39% retention of tree basal area, below which numbers of the Greater Glider suffer a marked decline, was inferred on the basis of comparisons with the results of other studies. Factors other than logging were important in determining the distribution of the Greater Glider. Elevation, in particular, was a significant environmental variable, with Greater Gliders more likely to occur in forests above 845 m a.s.1. The presence and absence of particular tree species also influenced the distribution of the Greater Glider. Forests containing Manna Gum E. viminalis and Mountain Gum E. dalrympleana were highly preferred compared to forests with a high proportion of E. obliqua. The presence of E. cypellocarpa appeared to improve the quality of habitat for the Greater Glider in forests dominated by E. obliqua. This study has shown that Greater Glider populations can be maintained at or near pre-logging levels when at least 40% of the original tree basal area is retained thoughout logged areas and when the usual practice of retaining unlogged forest in riparian strips is applied.
Variation in the recruitment behaviour of seagrass seeds: implications for population dynamics and resource management
Authors: J. Inglis Graeme
Published: May 2016

Effective conservation of marine organisms requires an understanding of the processes that affect the establishment, persistence and extinction of local populations. Our knowledge of the recruitment of seagrasses comes largely from studies done at small spatial and temporal scales within extant meadows. Descriptions of the demography of local populations, therefore, typically emphasize prolific ramet production and only a minor role for sexual propagules. Recent genetic and field studies, however, have shown greater variation in recruitment behaviour than previously suspected. In this paper, I review what is known about the seeds of seagrasses ? including their dormancy, dispersability and requirements for germination and establishment ? and examine the utility of recent conceptual models, developed for terrestrial clonal plants, to explain the long-term dynamics of seagrass populations. Sizable variation among species in seed size and dispersal strategy appears to be related predictably to variation in life-history and rates of recruitment. Species with small, poorly-dispersed fruits (e.g., Halophila, Halodule) are more likely to form persistent seed reserves and be rapid colonizers of disturbances within established meadows. Genera with large, buoyant fruits, capable of moderate dispersal (e.g., Thalassia, Posidonia), in contrast, appear to recruit rarely within existing meadows of conspecifics. Our ability to model long-term changes in demography and community structure is likely to benefit from a better knowledge of the importance of seed supply and microsite availability to recruitment.
Seagrass responses to and recovery (?) from seven years of brown tide
Authors: P. Onuf C.
Published: May 2016

Most harmful algal blooms are relatively short, violent paroxysms to aquatic systems. The Texas brown tide was unique in its 7-year domination of upper Laguna Madre wherein it reduced light penetrating 1 m from 31 to 63% on an annual basis between June 1990 and May 1997. In response, seagrasses declined in biomass in deep areas for two years. Over the next three years, bare areas opened up in the deepest areas of the seagrass meadow and the outer seagrass boundary retreated landward. In the last two years of the brown tide, regression of the dominant species, Halodule wrightii, slowed and stopped, and Halophila engelmanni, a previously minor species, revegetated some areas. Subsequent to cessation of meadow retreat, water clarity improved to pre-brown tide levels, consistent with the hypothesis that regeneration of nutrients from retreating sea grass meadow may have been the source of the nutrient subsidy required to sustain the brown tide at high concentration. However, after a short interlude of clear water and Halodule recovery, a resurgence of the bloom occurred and areas of regrowth succumbed. Although human activities did not seem to be involved in initiation or persistence of the brown tide, nutrients brought in by runoff from agricultural lands may have contributed to the return of bloom conditions.
Roles for veterinarians in wildlife conservation
Authors: Martin Anne
Published: May 2016

When it comes to conservation, veterinarians and other wildlife professionals have not always worked together. However, the gulf between them is rapidly narrowing as each becomes more aware of the need to co-operate with the other. Veterinarians have had to accept that their most effective role is as a member of a team, and that they need to acquire a broad understanding of biological and ecological issues in order to make meaningful contributions to wildlife conservation. In turn, biologists, ecologists, wildlife managers and others have begun to appreciate the unique skills of experienced wildlife veterinarians and the importance of disease as a threatening process. There is still progress to be made, but this will occur as the importance of multidisciplinary teamwork is better understood by all. There are many activities in wildlife management and conservation which can involve veterinarians, but veterinarians must be concerned with more than just the diagnosis and treatment of sick animals. The breadth and depth of their possible contributions extend far beyond this narrow view.
Distribution of the native earthworm fauna of the Perth metropolitan sector of the Swan Coastal Plain
Authors: Abbott Ian , Wills Allan
Published: May 2016

Assessment of areas suitable for inclusion in a comprehensive, adequate and representative (CAR) reserve system has been based primarily on distribution of original native vegetation and occurrence of vertebrates, particularly birds and mammals. However, reliable predictors of vertebrate and floristic diversity are not necessarily adequate predictors of invertebrate diversity. We sampled the earthworm fauna of the Perth metropolitan Swan Coastal Plain (SCP) to examine whether vegetation-based criteria are sufficient for identifying a conservation estate for native earthworms. Twenty-one native species were collected from 136 sample localities. All five previously described native species from the region and three native species previously collected but not formally described were again collected, while 13 previously uncollected species were found. Species abundances of native earthworms were uneven, in common with species-abundance relationships for many other invertebrate assemblages, with 10 singleton occurrences of species and few common species. Species diversity increased away from the coast across the sandy geomorphic units Quindalup, Spearwood and Bassendean. Our study did not resolve whether dlifferences in earthworm faunas reflect the gradient in soil qualities across these units, gradients in species-area effects, habitat diversity effects or a combination of these. Blocks of remnant vegetation identified in the Western Australian Government's Bush Forever plan as containing natural areas of regional conservation value are also likely to support at least one native earthworm species. However, many of the blocks of remnant vegetation so identified are not within the formal conservation estate. Two species identified in this survey fortuitously persist only in remnant vegetation patches not considered regionally significant. Actual regional diversity was estimated to be 38 native species, indicating many uncollected relatively rare species. Although earthworms are a low diversity group compared with other invertebrates, the localized distributions of most species indicate that the formal conservation estate does not provide adequate protection. Ongoing degradation of unprotected remnant vegetation will result in extinctions of localized invertebrate species.
"Paradise" and "Cloverdowns": following natural systems
Authors: melvin Dean
Published: May 2016

Two properties, "Paradise" and "Cloverdowns", are farmed by the Melvin family near Dowerin in the central wheatbelt of Western Australia (see Fig. 1, Hobbs 2003). The annual average rainfall is 350 mm and, before Europeans settled the area, it was well vegetated with perennial vegetation. The sandplain soils were dominated by mallees Eucalyptus spp., Kwongan or heath (predominantly Myrtaceae, Proteaceae and Leguminosae), and patches of York Gum E. loxophleba woodland. The heavier soils such as the brown sandy loams and red brown loams were clothed in woodland of Salmon Gum E. salmonophloia and York gum. The gravelly sands were covered by Tamma scrub which was dominated by sheoak Allocasuarina spp.
Carnivore persistence in fragmented habitats in urban southern California
Authors: A. Tigas Lourraine , H. Van Vuren Dirk , M. Sauvajot Raymond
Published: May 2016

We investigated the responses of carnivores to habitat fragmentation in urban southern California. We used scat, track, and remote camera surveys to determine presence and residence of carnivores on habitat fragments of various sizes (4.4-561.0 ha) and degrees of isolation (10-750 m). Fragment area explained a significant portion of the variation in all four measures of species richness (total species present, native species present, total species resident, and native species resident). Isolation was of secondary importance and was significant only for species presence. We suggest that fewer carnivore species at smaller or more isolated fragments resulted from foraging decisions based on lower food reward in smaller fragments and greater movement costs for more distant fragments. Carnivore species responded differentially to fragmentation. Bobcats Lynx rufus were fragmentation-sensitive and apparently required large fragments, thus they may be useful as focal species for conservation planning. In contrast, Coyotes Canis latrans were more fragmentation-tolerant and, along with smaller species such as Northern Raccoons Procyon lotor, Striped Skunks Mephitis mephitis, and Virginia Opossums Didelphis virginiana, can persist in smaller fragments. Our results suggest that most of the common carnivores can persist in fragmented urban habitat, provided that fragments are sufficiently large and in close proximity.
Invasion of native vegetation by Coolatai Grass Hyparrhenia hirta: impacts on native vegetation and management implications
Authors: L. McArdle c. Nadolny S. , M. Sindel b.
Published: May 2016

Coolatai Grass Hyparrhenia hirta is an exotic perennial grass and environmental weed that is spreading rapidly in parts of southeastern Australia. This study examined the effects of Coolatai Grass invasion on the composition of ground strata vegetation within Kwiambal National Park in northern New South Wales. Plots that were heavily infested with Coolatai Grass together with matching control plots were surveyed. Coolatai Grass infestation reduced the richness of native ground strata plants and their projected groundcover, but did not affect the number of exotic species in plots. The control plots varied markedly in floristic composition, but infested sites were more homogenous, with Coolatai Grass clearly dominating the ground strata vegetation. Coolatai Grass appears to increase in abundance following fire; it persists under heavy grazing and is resistant to many herbicides. Spot spraying small swards and isolated tussocks with glyphosate or flupropanate provides prospects of control on a small scale, but there are no suitable methods for largescale control. Changes to roadside management practices could help to reduce the spread of Coolatai Grass, but research into seed bank dynamics and appropriate control techniques is required, as well as increased awareness of the threat to native vegetation posed by the species.
Metrics for assessing the biodiversity values of farming systems and agricultural landscapes
Authors: Williams Jann
Published: May 2016

This paper reviews current approaches to assessing biodiversity values in agricultural landscapes in southern and eastern Australia and makes recommendations about their applicability to revegetation for commercial and non-commercial purposes. A typology based on the quantitative measurement of structural, functional and compositional attributes of biodiversity at multiple scales is used as the framework for the review. Metrics currently used to assess biodiversity primarily focus on conservation outcomes for natural systems rather than other cultural, social and economic values. They cover a range of scales (from local to global), landscape contexts (from intact to relictual) and levels of organization (from genes to ecosystems). Surrogate measures are commonly used to assess biodiversity, particularly vegetation type and condition. Recently developed metrics are beginning to attach weightings to different habitat attributes and incorporate "natural" benchmarks. While expert panels play an important role in developing and assessing biodiversity metrics, a number of untested assumptions underpin current approaches. Rigorous testing and validation is therefore required if the current set of metrics is to serve as a reliable indicator of biodiversity across agricultural landscapes in Australia. While it is encouraging that more explicit and repeatable measures are being developed, as well as metrics that score the biodiversity value of a broad range of land uses, clearer definitions and objectives are required. Metrics also need further development and testing for aquatic species and systems and their interface with terrestrial systems, non-woody terrestrial systems, revegetation and the persistence of species across the landscape. Importantly, there is a need for greater cross-fertilization between ecologists, agricultural, social and other scientists, and private land managers to identify specific and measurable attributes of biodiversity within a farming systems context. This will help ensure that the conservation and utilization of biodiversity becomes an integral part of natural resource management in rural landscapes.