bluuebunny/crossref_metadata_2025 huggingface dataset:
Spin wave isolator based on frequency displacement nonreciprocity in ferromagnetic bilayer
Authors: Shichi Shinsuke , Kanazawa Naoki , Matsuda Kenji , Okajima Shingo , Hasegawa Takashi , Okada Takekazu , Goto Taichi , Takagi Hiroyuki , Inoue Mitsuteru
Published: March 2015

We demonstrated the spin wave isolator using bilayer ferromagnetic media comprising single crystalline and poly-crystalline yttrium iron garnet films, which can control the propagation frequency of magnetostatic waves by the direction of applied magnetic field. This isolator's property does not depend on their thickness then this can be downsized and integrated for nano-scale magnonic circuits. Calculated dispersion relationship shows good agreement with measured one.
The same number of optimized parameters scheme for determining intermolecular interaction energies
Authors: Kristensen Kasper , Ettenhuber Patrick , Eriksen Janus Juul , Jensen Frank , Jørgensen Poul
Published: March 2015

We propose the Same Number Of Optimized Parameters (SNOOP) scheme as an alternative to the counterpoise method for treating basis set superposition errors in calculations of intermolecular interaction energies. The key point of the SNOOP scheme is to enforce that the number of optimized wave function parameters for the noninteracting system is the same as for the interacting system. This ensures a delicate balance between the quality of the monomer and dimer finite basis set calculations. We compare the SNOOP scheme to the uncorrected and counterpoise schemes theoretically as well as numerically. Numerical results for second-order Møller-Plesset perturbation theory (MP2) and coupled-cluster with single, double, and approximate triple excitations (CCSD(T)) show that the SNOOP scheme in general outperforms the uncorrected and counterpoise approaches. Furthermore, we show that SNOOP interaction energies calculated using a given basis set are of similar quality as those determined by basis set extrapolation of counterpoise-corrected results obtained at a similar computational cost.
Exact coherent structures and chaotic dynamics in a model of cardiac tissue
Authors: Byrne Greg , Marcotte Christopher D. , Grigoriev Roman O.
Published: March 2015

Unstable nonchaotic solutions embedded in the chaotic attractor can provide significant new insight into chaotic dynamics of both low- and high-dimensional systems. In particular, in turbulent fluid flows, such unstable solutions are referred to as exact coherent structures (ECS) and play an important role in both initiating and sustaining turbulence. The nature of ECS and their role in organizing spatiotemporally chaotic dynamics, however, is reasonably well understood only for systems on relatively small spatial domains lacking continuous Euclidean symmetries. Construction of ECS on large domains and in the presence of continuous translational and/or rotational symmetries remains a challenge. This is especially true for models of excitable media which display spiral turbulence and for which the standard approach to computing ECS completely breaks down. This paper uses the Karma model of cardiac tissue to illustrate a potential approach that could allow computing a new class of ECS on large domains of arbitrary shape by decomposing them into a patchwork of solutions on smaller domains, or tiles, which retain Euclidean symmetries locally.
Stabilizing shallow color centers in diamond created by nitrogen delta-doping using SF6 plasma treatment
Authors: Osterkamp Christian , Lang Johannes , Scharpf Jochen , Müller Christoph , McGuinness Liam Paul , Diemant Thomas , Behm R. Jürgen , Naydenov Boris , Jelezko Fedor
Published: March 2015

Here we report the fabrication of stable, shallow (<5 nm) nitrogen-vacancy (NV) centers in diamond by nitrogen delta doping at the last stage of the chemical vapor deposition growth process. The NVs are stabilized after treating the diamond in SF6 plasma, otherwise the color centers are not observed, suggesting a strong influence from the surface. X-ray photoelectron spectroscopy measurements show the presence of only fluorine atoms on the surface, in contrast to previous studies, indicating very good surface coverage. We managed to detect hydrogen nuclear magnetic resonance signal from protons in the immersion oil, revealing a depth of the NVs of about 5 nm.
Reliable and integrated technique for determining resonant frequency in radio frequency resonators. Application to a high-precision resonant cavity-based displacement sensor
Authors: Jauregui Rigoberto , Asua Estibaliz , Portilla Joaquin , Etxebarria Victor
Published: March 2015

This paper presents a reliable and integrated technique for determining the resonant frequency of radio frequency resonators, which can be of interest for different purposes. The approach uses a heterodyne scheme as phase detector coupled to a voltage-controlled oscillator. The system seeks the oscillator frequency that produces a phase null in the resonator, which corresponds to the resonant frequency. A complete explanation of the technique to determine the resonant frequency is presented and experimentally tested. The method has been applied to a high-precision displacement sensor based on resonant cavity, obtaining a theoretical nanometric precision.
Controlling the magnetic susceptibility in an artificial elliptical quantum ring by magnetic flux and external Rashba effect
Authors: Omidi Mahboubeh , Faizabadi Edris
Published: March 2015

Magnetic susceptibility is investigated in a man-made elliptical quantum ring in the presence of Rashba spin-orbit interactions and the magnetic flux. It is shown that magnetic susceptibility as a function of magnetic flux changes between negative and positive signs periodically. The periodicity of the Aharonov-Bohm oscillations depends on the geometry of the region where magnetic field is applied, the eccentricity, and number of sites in each chain ring (the elliptical ring is composed of chain rings). The magnetic susceptibility sign can be reversed by tuning the Rashba spin-orbit strength as well. Both the magnetic susceptibility strength and sign can be controlled via external spin-orbit interactions, which can be exploited in spintronics and nanoelectronics.
Quantum logic gates from time-dependent global magnetic field in a system with constant exchange
Authors: Nenashev A. V. , Zinovieva A. F. , Dvurechenskii A. V. , Gornov A. Yu. , Zarodnyuk T. S.
Published: March 2015

We propose a method that implements a universal set of one- and two-quantum-bit gates for quantum computation in a system of coupled electron pairs with constant non-diagonal exchange interaction. In our proposal, suppression of the exchange interaction is performed by the continual repetition of single-spin rotations. A small g-factor difference between the electrons allows for addressing qubits and avoiding strong magnetic field pulses. Numerical experiments were performed to show that, to implement the one- and two-qubit operations, it is sufficient to change the strength of the magnetic field by a few Gauss. This introduces one and then the other electron in a resonance. To determine the evolution of the two-qubit system, we use the algorithms of optimal control theory.
Dynamics of classical particles in oval or elliptic billiards with a dispersing mechanism
Authors: da Costa Diogo Ricardo , Dettmann Carl P. , de Oliveira Juliano A. , Leonel Edson D.
Published: March 2015

Some dynamical properties for an oval billiard with a scatterer in its interior are studied. The dynamics consists of a classical particle colliding between an inner circle and an external boundary given by an oval, elliptical, or circle shapes, exploring for the first time some natural generalizations. The billiard is indeed a generalization of the annular billiard, which is of strong interest for understanding marginally unstable periodic orbits and their role in the boundary between regular and chaotic regions in both classical and quantum (including experimental) systems. For the oval billiard, which has a mixed phase space, the presence of an obstacle is an interesting addition. We demonstrate, with details, how to obtain the equations of the mapping, and the changes in the phase space are discussed. We study the linear stability of some fixed points and show both analytically and numerically the occurrence of direct and inverse parabolic bifurcations. Lyapunov exponents and generalized bifurcation diagrams are obtained. Moreover, histograms of the number of successive iterations for orbits that stay in a cusp are studied. These histograms are shown to be scaling invariant when changing the radius of the scatterer, and they have a power law slope around −3. The results here can be generalized to other kinds of external boundaries.
Note: Fast neutron efficiency in CR-39 nuclear track detectors
Authors: Cavallaro S.
Published: March 2015

CR-39 samples are commonly employed for fast neutron detection in fusion reactors and in inertial confinement fusion experiments. The literature reported efficiencies are strongly depending on experimental conditions and, in some cases, highly dispersed. The present note analyses the dependence of efficiency as a function of various parameters and experimental conditions in both the radiator-assisted and the stand-alone CR-39 configurations. Comparisons of literature experimental data with Monte Carlo calculations and optimized efficiency values are shown and discussed.
The efficacy of post porosity plasma protection against vacuum-ultraviolet damage in porous low-k materials
Authors: Lionti K. , Darnon M. , Volksen W. , Magbitang T. , Dubois G.
Published: March 2015

As of today, plasma damage remains as one of the main challenges to the reliable integration of porous low-k materials into microelectronic devices at the most aggressive node. One promising strategy to limit damage of porous low-k materials during plasma processing is an approach we refer to as post porosity plasma protection (P4). In this approach, the pores of the low-k material are filled with a sacrificial agent prior to any plasma treatment, greatly minimizing the total damage by limiting the physical interactions between plasma species and the low-k material. Interestingly, the contribution of the individual plasma species to the total plasma damage is not fully understood. In this study, we investigated the specific damaging effect of vacuum-ultraviolet (v-UV) photons on a highly porous, k = 2.0 low-k material and we assessed the P4 protective effect against them. It was found that the impact of the v-UV radiation varied depending upon the v-UV emission lines of the plasma. More importantly, we successfully demonstrated that the P4 process provides excellent protection against v-UV damage.
Modulational instability, nonautonomous breathers and rogue waves for a variable-coefficient derivative nonlinear Schrödinger equation in the inhomogeneous plasmas
Authors: Wang Lei , Li Min , Qi Feng-Hua , Xu Tao
Published: March 2015

Under investigation in this paper is a variable-coefficient derivative nonlinear Schrödinger (vc-DNLS) equation modeling the nonlinear Alfvén waves in the inhomogeneous plasmas. The modulation instability is examined for this inhomogeneous nonlinear model. The nonautonomous breather and rogue wave solutions of the vc-DNLS equation are obtained via the modified Darboux transformation. It is found that the velocity and amplitude of the breather can be controlled by the inhomogeneous magnetic field and nonuniform density. Such novel phenomena as breather amplification and nonlinear Talbot effect-like property are demonstrated with the proper choices of the inhomogeneous parameters. Furthermore, dynamics of the fundamental rogue wave, periodical rogue wave, and composite rogue wave are graphically discussed. The trajectories and amplitudes of the rogue waves can be manipulated by the inhomogeneous magnetic field and nonuniform density. In addition, the nonlinear tunneling of the rogue waves and breathers is studied. As an application, a sample model is treated with our results, and the graphical illustrations exhibit the compressing, expanding, and fluctuating phenomena of the Alfvén rogue waves.
A numerical study on bow shocks around the lightning return stroke channel
Authors: Chen Qiang , Chen Bin , Chen P. F. , Yi Yun , Mao Yunfei , Xiong Run
Published: March 2015

Bow shock structures are important to various hydrodynamics and magnetohydrodynamics (MHD) phenomena in geophysics and astrophysics. The formation and propagation of bow shocks around the lightning return stroke channel are investigated based on the self-similar motion theory and simulated with a two-dimensional Eulerian finite volume resistive radiation MHD code. In this framework, as verification of theoretical models, the evolving structures of many quantities, such as the plasma density, temperature, pressure, shock velocity, and magnetic field, can be obtained, which present all the characteristics of bow shocks in the lightning return stroke processes. The evolution characteristics and the configuration of the curved return stroke channels, e.g., the non-ideal effects and the scaling laws, are discussed in detail. The results may have applications for some observed features of the return stroke channels and other phenomena in the lightning discharge plasmas.
High-power green and blue electron-beam pumped surface-emitting lasers using dielectric and epitaxial distributed Bragg reflectors
Authors: Klein T. , Klembt S. , Kozlovsky V. I. , Zheng A. , Tiberi M. D. , Kruse C.
Published: March 2015

ZnSe-based electron-beam pumped vertical-cavity surface-emitting lasers for the green (λ = 530 nm) and blue (λ = 462 nm) spectral region have been realized. Structures with and without epitaxial bottom distributed Bragg reflector have been fabricated and characterized. The samples consist of an active region containing 20 quantum wells with a cavity length varying between an optical thickness of 10 λ to 20 λ. The active material is ZnCdSSe in case of the green devices and ZnSe for the blue ones. Room temperature single mode lasing for structures with and without epitaxial bottom mirror with a maximum output power up to 5.9 W (green) and 3.3 W (blue) is achieved, respectively.
Electrical and photovoltaic characteristics of MoS2/Si p-n junctions
Authors: Hao Lanzhong , Liu Yunjie , Gao Wei , Han Zhide , Xue Qingzhong , Zeng Huizhong , Wu Zhipeng , Zhu Jun , Zhang Wanli
Published: March 2015

Bulk-like molybdenum disulfide (MoS2) thin films were deposited on the surface of p-type Si substrates using dc magnetron sputtering technique and MoS2/Si p-n junctions were formed. The vibrating modes of E12g and A1g were observed from the Raman spectrum of the MoS2 films. The current density versus voltage (J-V) characteristics of the junction were investigated. A typical J-V rectifying effect with a turn-on voltage of 0.2 V was shown. In different voltage range, the electrical transporting of the junction was dominated by diffusion current and recombination current, respectively. Under the light illumination of 15 mW cm−2, the p-n junction exhibited obvious photovoltaic characteristics with a short-circuit current density of 3.2 mA cm−2 and open-circuit voltage of 0.14 V. The fill factor and energy conversion efficiency were 42.4% and 1.3%, respectively. According to the determination of the Fermi-energy level (∼4.65 eV) and energy-band gap (∼1.45 eV) of the MoS2 films by capacitance-voltage curve and ultraviolet-visible transmission spectra, the mechanisms of the electrical and photovoltaic characteristics were discussed in terms of the energy-band structure of the MoS2/Si p-n junctions. The results hold the promise for the integration of MoS2 thin films with commercially available Si-based electronics in high-efficient photovoltaic devices.
Magnetic behavior of La-doped Fe3O4 studied by perturbed angular correlation spectroscopy with 111Cd and 140Ce
Authors: Matos I. T. , Bosch-Santos B. , Cabrera-Pasca G. A. , Carbonari A. W.
Published: March 2015

In this paper, the local magnetic properties of La-doped Fe3O4 (5% and 10%) bulk and Nanoparticles (NPs) samples were studied by measuring hyperfine interactions in a wide range of temperature from 10 to 900 K with perturbed γ-γ angular correlation spectroscopy using 111In(111Cd) and 140La(140Ce) as probe nuclei. Results for the temperature dependence of the magnetic hyperfine field (Bhf) for bulk and NP samples, pure and doped with La show that its behavior follows a second order Brillouin-like transition from which the Curie temperature (TC) was determined (TC ∼ 855 K). Results also show two different regions in NP samples: the core where a minor fraction of probe nuclei with well defined magnetic dipole frequency was observed and the shell where a major fraction with broad distributed electric quadrupolar frequency (surface effect in NP) was observed. The Verwey transition TV ∼ 120 K, due the order disorder phase, was also observed in all samples. The results are discussed in terms of the magnetic exchange interaction between Fe2+ and Fe3+ ions in the two regions of NP.
Study of breakdown voltage of indium-gallium-zinc-oxide-based Schottky diode
Authors: Xin Qian , Yan Linlong , Luo Yi , Song Aimin
Published: March 2015

In contrast to the intensive studies on thin-film transistors based on indium gallium zinc oxide (IGZO), the research on IGZO-based diodes is still very limited, particularly on their behavior and stability under high bias voltages. Our experiments reveal a sensitive dependence of the breakdown voltage of IGZO Schottky diodes on the anode metal and the IGZO film thickness. Devices with an Au anode are found to breakdown easily at a reverse bias as low as −2.5 V, while the devices with a Pd anode and a 200-nm, fully depleted IGZO layer have survived up to −15 V. All diodes are fabricated by radio-frequency magnetron sputtering at room temperature without any thermal treatment, yet showing an ideality factor as low as 1.14, showing the possibility of achieving high-performance Schottky diodes on flexible plastic substrate.
Detection and imaging of the oxygen deficiency in single crystalline YBa2Cu3O7−δ thin films using a scanning positron beam
Authors: Reiner M. , Gigl T. , Jany R. , Hammerl G. , Hugenschmidt C.
Published: March 2015

Single crystalline YBa2Cu3O7−δ (YBCO) thin films were grown by pulsed laser deposition in order to probe the oxygen deficiency δ using a mono-energetic positron beam. The sample set covered a large range of δ (0.191 < δ < 0.791) yielding a variation of the critical temperature Tc between 25 and 90 K. We found a linear correlation between the Doppler broadening of the positron electron annihilation line and δ determined by X-ray diffraction. Ab-initio calculations have been performed in order to exclude the presence of Y vacancies and to ensure the negligible influence of potentially present Ba or Cu vacancies to the found correlation. Moreover, scanning with the positron beam allowed us to analyze the spatial variation of δ, which was found to fluctuate with a standard deviation of up to 0.079(5) within a single YBCO film.
The impact of plasma dynamics on the self-magnetic-pinch diode impedance
Authors: Bennett Nichelle , Welch Dale R. , Webb Timothy J. , Mazarakis Michael G. , Kiefer Mark L. , Crain M. Dale , Droemer Darryl W. , Gignac Raymond E. , Johnston Mark D. , Leckbee Joshua J. , Molina Isidro , Nielsen Dan , Obregon Robert , Romero Tobias , Simpson Sean , Smith Chase C. , Wilkins Frank L. , Ziska Derek
Published: March 2015

The self-magnetic-pinch diode is being developed as an intense electron beam source for pulsed-power-driven x-ray radiography. The basic operation of this diode has long been understood in the context of pinched diodes, including the dynamic effect that the diode impedance decreases during the pulse due to electrode plasma formation and expansion. Experiments being conducted at Sandia National Laboratories' RITS-6 accelerator are helping to characterize these plasmas using time-resolved and time-integrated camera systems in the x-ray and visible. These diagnostics are analyzed in conjunction with particle-in-cell simulations of anode plasma formation and evolution. The results confirm the long-standing theory of critical-current operation with the addition of a time-dependent anode-cathode gap length. The results may suggest that anomalous impedance collapse is driven by increased plasma radial drift, leading to larger-than-average ion vr × Bθ acceleration into the gap.
Influence of Ga-concentration on the electrical and magnetic properties of magnetoelectric CoGaxFe2−xO4/BaTiO3 composite
Authors: Ni Yan , Zhang Zhen , Nlebedim Cajetan I. , Jiles David C.
Published: March 2015

Multiferroic materials exhibit magnetoelectric (ME) coupling and promise new device applications including magnetic sensors, generators, and filters. An effective method for developing ME materials with enhanced ME effect is achieved by the coupling through the interfacial strain between piezoelectric and magnetostrictive materials. In this study, the electrical and magnetic properties of Ga doped magnetoelectric CoGaxFe2−xO4/BaTiO3 composite are studied systematically. It is found that Ga doping improves the sensitivity of magnetoelastic response and stabilizes the magnetic phase of the composites. More importantly, Ga doping reduces the electrical conductivity of composite, as well as the dielectric loss. An enhancement of the electrostrain with doping Ga is also observed. Quantitative estimation indicates that magnetoelectric coupling is enhanced for Ga-doped CoGaxFe2−xO4/BaTiO3 composites. Thus, the present work is beneficial to the practical application of composite CoFe2O4/BaTiO3-based multiferroic materials.
Evaluation of pulsed laser annealing for flexible multilayer MoS2 transistors
Authors: Kwon Hyuk-Jun , Kim Sunkook , Jang Jaewon , Grigoropoulos Costas P.
Published: March 2015

To realize the proper electrical characteristics of field-effect transistors, the quality of the contact and interface must be improved because they can substantially distort the extracted mobility, especially for materials with low densities of states like molybdenum disulfide (MoS2). We show that mechanically flexible MoS2 thin-film transistors (TFTs) with selectively laser annealed source/drain electrodes achieve enhanced device performance without plastic deformation including higher field-effect mobility (from 19.59 to 45.91 cm2 V−1 s−1) in the linear regime, decreased subthreshold swing, and enhanced current saturation. Furthermore, numerical thermal simulations, measured current-voltage characteristics, and contact-free mobility extracted from the Y-function method suggest that the enhanced performance originated from a decrease in the Schottky barrier effect at the contact and an improvement of the channel interface. These results demonstrate that picosecond laser annealing can be a promising technology for building high performance flexible MoS2 TFTs in flexible/stretchable circuitry, which should be processed at low temperatures.
Zinc oxide modified with benzylphosphonic acids as transparent electrodes in regular and inverted organic solar cell structures
Authors: Lange Ilja , Reiter Sina , Kniepert Juliane , Piersimoni Fortunato , Pätzel Michael , Hildebrandt Jana , Brenner Thomas , Hecht Stefan , Neher Dieter
Published: March 2015

An approach is presented to modify the work function of solution-processed sol-gel derived zinc oxide (ZnO) over an exceptionally wide range of more than 2.3 eV. This approach relies on the formation of dense and homogeneous self-assembled monolayers based on phosphonic acids with different dipole moments. This allows us to apply ZnO as charge selective bottom electrodes in either regular or inverted solar cell structures, using poly(3-hexylthiophene):phenyl-C71-butyric acid methyl ester as the active layer. These devices compete with or even surpass the performance of the reference on indium tin oxide/poly(3,4-ethylenedioxythiophene) polystyrene sulfonate. Our findings highlight the potential of properly modified ZnO as electron or hole extracting electrodes in hybrid optoelectronic devices.
Ion polarization behavior in alumina under pulsed gate bias stress
Authors: Liu Yu , Diallo Abdou Karim , Katz Howard E.
Published: March 2015

Alkali metal ion incorporation in alumina significantly increases alumina capacitance by ion polarization. With high capacitance, ion-incorporated aluminas become promising high dielectric constant (high-k) gate dielectric materials in field-effect transistors (FETs) to enable reduced operating voltage, using oxide or organic semiconductors. Alumina capacitance can be manipulated by incorporation of alkali metal ions, including potassium (K+), sodium (Na+), and lithium (Li+), having different bond strengths with oxygen. To investigate the electrical stability of zinc tin oxide-based transistors using ion incorporated alumina as gate dielectrics, pulsed biases at different duty cycles (20%, 10%, and 2% representing 5 ms, 10 ms, and 50 ms periods, respectively) were applied to the gate electrode, sweeping the gate voltage over series of these cycles. We observed a particular bias stress-induced decrease of saturation field-effect mobility accompanied by threshold voltage shifts (ΔVth) in potassium and sodium-incorporated alumina (abbreviated as PA and SA)-based FETs at high duty cycle that persisted over multiple gate voltage sweeps, suggesting a possible creation of new defects in the semiconductor. This conclusion is also supported by the greater change in the mobility-capacitance (μC) product than in capacitance itself. Moreover, a more pronounced ΔVth over shorter times was observed in lithium-incorporated alumina (abbreviated as LA)-based transistors, suggesting trapping of electrons in existing interfacial states. ΔVth from multiple gate voltage sweeps over time were fit to stretched exponential forms. All three dielectrics show good stability using 50-ms intervals (20-Hz frequencies), corresponding to 2% duty cycles.
Residual tensile stress in robust insulating rhombohedral Bi1−xLaxFe1−yTiyO3 multiferroic ceramics and its ability to pin ferroelectric polarization switching
Authors: Zhang Linlin , Yu Jian
Published: March 2015

Robust insulating rhombohedral Bi1−xLaxFe1−yTiyO3 multiferroic ceramics with 0.02 ≤ x ≤ 0.12 and 0.01 ≤ y ≤ 0.08 are prepared by a refined solid-state reaction electroceramic processing. Residual internal tensile stresses existed in the ceramics according to unit cell volume enlargement observed by X-ray diffraction and frequency redshifts of Raman modes related to Bi motion and oxygen octahedral rotation detected by Raman scattering measurements. Residual internal tensile stresses in the ceramics are believed to originate from structural phase transitions through an intermediate paraelectric rhombohedral phase with a negative thermal expansion coefficient in the transformation from paraelectric cubic to ferroelectric rhombohedral phases. All of the rhombohedral Bi1−xLaxFe1−yTiyO3 ceramics exhibited a pinched polarization versus electric field hysteresis loop indicative of ferroelectric subswitching. We argue that the residual internal tensile stresses are responsible for such ferroelectric polarization subswitching behavior in the Bi1−xLaxFe1−yTiyO3 ceramics.
Non-equilibrium Green's function calculation of AlGaAs-well-based and GaSb-based terahertz quantum cascade laser structures
Authors: Yasuda H. , Hosako I.
Published: March 2015

We investigate the performance of terahertz quantum cascade lasers (THz-QCLs) based on AlxGa1−xAs/AlyGa1−yAs and GaSb/AlGaSb material systems to realize higher-temperature operation. Calculations with the non-equilibrium Green's function method reveal that the AlGaAs-well-based THz-QCLs do not show improved performance, mainly because of alloy scattering in the ternary compound semiconductor. The GaSb-based THz-QCLs offer clear advantages over GaAs-based THz-QCLs. Weaker longitudinal optical phonon–electron interaction in GaSb produces higher peaks in the spectral functions of the lasing levels, which enables more electrons to be accumulated in the upper lasing level.
Phase Behaviours of Polybutadiene–Polyacrylic Acid Brushes in Compressed Carbon Dioxide
Authors: Zhang Rui , Liu Lixiao , Wen Yicun , Cang Yu , Shi Guixin , Zhao Yingyi , Liu Xiaoling , Lin Ying , Xu Jun , Zhou Zhiming , Guo Xuhong
Published: March 2015

Our present work investigated the phase behaviour of polybutadiene–poly acrylic acid (PB–PAA) brushes–solvent–CO2 ternary system in detail. The phase separation pressures increased with increasing temperatures and solid contents of PB–PAA solution, and decreased with increasing sizes of the brushes. Considering that the expansion of water was much smaller than that of ethanol by compressed CO2, a higher cloud point pressure of CO2 could be employed to reach the phase separation when water was added as the co-solvent. Owing to the penetration of CO2 into the periphery of the shell, the chains of the polymer brushes initially shrank and then turned to aggregations before finally precipitating upon CO2 addition. Our results provide a simple and effective way for separation and recovery of polymer brushes that could promote a wider range of their applications.
Protosternini (Coleoptera : Hydrophilidae) corroborated as monophyletic and its larva described for the first time: a review of the myrmecophilous genus Sphaerocetum
Authors: Fikáček Martin , Maruyama Munetoshi , Komatsu Takashi , von Beeren Christoph , Vondráček Dominik , Short Andrew E. Z.
Published: March 2015

The genus Sphaerocetum Fikáček, 2010 is reviewed on the basis of specimens collected from mixed ant nests shared by Camponotus Mayr, 1861 and Crematogaster Lund, 1831 ants in Peninsular Malaysia. Two new species, S. arboreum, sp. nov. and S. hortulanum, sp. nov., are described. A larva of S. arboreum was collected in the same nest as the adults, implying that it is likely that the entire life cycle takes place inside the ant nest; its association with adults was confirmed by cox1 sequences. It is described in detail and represents the first known larva of the tribe Protosternini. Fragments of four genes (cox1, cox2, 18S and 28S) were amplified for S. arboreum and combined with previously generated data in order to test the position of the genus within the subfamily Sphaeridiinae. The analyses revealed Sphaerocetum as a sister taxon to Protosternum Sharp, 1890, corroborating the monophyly of the tribe Protosternini. Bayesian analysis revealed an alternative hypothesis of the phylogenetic position of the tribe, indicating that Protosternini is a sister-group to Omicrini. This position is supported by the chaetotaxy of the maxillary stipes of the larva, which lacks the increased number of stout setae on the inner face present in all other Sphaeridiinae larvae except Omicrini.
Evaluation of a spring-powered captive bolt gun for killing kangaroo pouch young
Authors: Sharp T. M. , McLeod S. R. , Leggett K. E. A. , Gibson T. J.
Published: March 2015

Context During commercial harvesting or non-commercial kangaroo culling programs, dependent young of shot females are required to be euthanased to prevent suffering and because they would be unlikely to survive. However, the current method for killing pouch young, namely a single, forceful blow to the base of the skull, is applied inconsistently by operators and perceived by the public to be inhumane. Aims To determine whether an alternative method for killing pouch young, namely a spring-operated captive bolt gun, is effective at causing insensibility in kangaroo pouch young. Methods Trials of spring-operated captive bolt guns were conducted first on the heads of 15 dead kangaroo young and then on 21 live pouch young during commercial harvesting. We assessed the effectiveness at causing insensibility in live animals and damage caused to specific brain areas. We also measured depth of bolt penetration and skull thickness. Performance characteristics (e.g. bolt velocity) of two types of spring-operated guns were also measured and compared with cartridge-powered devices. Key results When tested on the heads of dead animals, the spring-operated captive bolt gun consistently produced a large entrance cavity and a well defined wound tract, which extended into the cerebrum, almost extending the full thickness of the brain, including the brainstem. When tested on live pouch young, the captive bolt gun caused immediate insensibility in only 13 of 21 animals. This 62% success rate is significantly below the 95% minimum acceptable threshold for captive bolt devices in domestic animal abattoirs. Failure to stun was related to bolt placement, but other factors such as bolt velocity, bolt diameter and skull properties such as thickness and hardness might have also contributed. Spring-operated captive bolt guns delivered 20 times less kinetic energy than did cartridge-powered devices. Conclusions Spring-operated captive bolt guns cannot be recommended as an acceptable or humane method for stunning or killing kangaroo pouch young. Implications Captive bolt guns have potential as a practical alternative to blunt head trauma for effective euthanasia and reducing animal (and observer) distress. However, operators must continue to use the existing prescribed killing methods until cartridge-powered captive bolt guns have been trialled as an alternative bolt propelling method.
Attachment and performance of Argos satellite tracking devices fitted to black cockatoos (Calyptorhynchus spp.)
Authors: Groom Christine , Warren Kris , Le Souef Anna , Dawson Rick
Published: March 2015

Context
Studying interactions between a wildlife species and its spatial environment can enable a deeper understanding of its ecology. Studies of spatial ecology are generally undertaken by attaching tracking devices to selected individuals and following their movements. Highly mobile species, such as black cockatoos (Calyptorhynchus spp.), that occupy habitats with patchy resources are ideal candidates. The powerful beak and chewing habits of black cockatoos make it difficult to successfully attach tracking devices to them.

Aims
We developed a safe technique for attaching tracking devices to black cockatoos and assessed the impact of the tracking devices, as well as their performance in relation to battery life, retention time and accuracy of location fixes.

Methods
We describe a technique for attaching Telonics (Mesa, AZ, USA) Argos Avian Transmitter TAV 2617 tracking devices to the two central tail feathers of black cockatoos.

Key results
Of 26 tracking devices fitted (24 to Carnaby’s cockatoos, C. latirostris; two to Baudin’s cockatoos, C. baudinii), 20 exhibited longer retention time than the nominal battery life. One tracking device was chewed until it was non-functional before release and two were presumed chewed after release because their tracking devices failed prematurely. There was no evidence that the tracking devices inhibited the flight capability of cockatoos. The performance of the Argos tracking devices exceeded expectations with regard to retention times, battery life and overall accuracy of location fixes. The tracking devices enabled detection of instances of rapid long-distance movements, including one bird that travelled 70 km between night roosts while migrating. Most study birds (68%) remained within 50 km of their release sites while monitored.

Conclusion
The tracking devices were a suitable choice for black cockatoos and for the purpose of this study. They posed minimal snag risk, were of suitable dimensions for tail attachment and they enabled data to be collected even if birds dispersed long distances. The main limitations that must be considered when assessing their suitability for future research projects are the errors associated with location fixes, limited retention time in relation to moulting of tail feathers and limited battery life.

Implications
The development of a method for successfully attaching tracking devices to black cockatoos opens the possibility to study aspects of the ecology of black cockatoos and other highly mobile species that was not previously possible.
Population recovery of the yellow-footed rock-wallaby following fox control in New South Wales and South Australia
Authors: Sharp Andy , Norton Melinda , Havelberg Chris , Cliff Wendy , Marks Adam
Published: March 2015

Context Introduced herbivores and carnivores have significantly altered ecosystems across Australia and have been implicated in the decline and extinction of many species, particularly in the arid and semiarid zones. The experimental confirmation of agents of decline is a fundamental step in threatened species management, allowing for an efficient allocation of resources and effective species recovery. Aims Following unsuccessful attempts to increase the abundance of yellow-footed rock-wallaby populations through concerted goat control across the southern extent of their range, the primary aim of our study was to determine whether fox predation was limiting the recovery of wallaby populations. Methods Intensive fox-control programs (1080 baiting) were initiated around wallaby subpopulations in New South Wales and South Australia. Wallaby numbers were monitored for a three-year period before and after the initiation of fox control, and ANCOVA used to examine for differences between the subpopulation’s rate of increase (r). Observational data were used to determine the demographic effects of fox predation on wallaby colonies in New South Wales. Key results Wallaby subpopulations that were treated with fox control increased significantly, while experimental control subpopulations remained at consistently low levels. Juvenile and subadult wallabies were apparent within the treated New South Wales subpopulation, but almost absent from the control subpopulation, suggesting that fox predation focussed primarily on these age classes. Conclusions Fox predation is a major limiting factor for southern wallaby populations and fox control should be the primary management action to achieve species recovery. Implications Although a significant limiting factor, the regulatory effect of fox predation was not assessed and, as such, it cannot be confirmed as being the causal factor responsible for the historic declines in wallaby abundance. The determination of whether fox predation acts in a limiting or regulatory fashion requires further experimentation, but its resolution will have significant implications for the strategic allocation of conservation resources.
Global trends in antimicrobial use in food animals
Authors: Van Boeckel Thomas P. , Brower Charles , Gilbert Marius , Grenfell Bryan T. , Levin Simon A. , Robinson Timothy P. , Teillant Aude , Laxminarayan Ramanan
Published: March 2015

Significance

Antimicrobials are used in livestock production to maintain health and productivity. These practices contribute to the spread of drug-resistant pathogens in both livestock and humans, posing a significant public health threat. We present the first global map (228 countries) of antibiotic consumption in livestock and conservatively estimate the total consumption in 2010 at 63,151 tons. We project that antimicrobial consumption will rise by 67% by 2030, and nearly double in Brazil, Russia, India, China, and South Africa. This rise is likely to be driven by the growth in consumer demand for livestock products in middle-income countries and a shift to large-scale farms where antimicrobials are used routinely. Our findings call for initiatives to preserve antibiotic effectiveness while simultaneously ensuring food security in low- and lower-middle-income countries.
Global politics, American hegemony and vulnerability, and Jungian-psychosocial studies: why there are no winners in the battle between Trickster Pedro Urdemales and the Gringos
Authors: Samuels Andrew
Published: March 2015

The author reviews the distortions of global politics wrought by US power and also by US vulnerability. It is understandable that many in the West are far from proud of the achievements of their culture. Those whose concern is for the management of climate change via ecopsychology are right to challenge ‘climate change denial’. But it is problematic when ‘salvation’ is sought from other cultures alleged to have a closer connection to ‘nature’ (itself a problematic term). Though well-meaning, this, the author contends, is politically and psychologically damaging. The author charges many Jungian attempts to compare the ‘Western psyche’ and the ‘psyche’ of indigenous peoples such as the Navajo Native Americans with cultural colonialism, Orientalism, and idealisation. He suggests that other political pathways and projects are needed if the desires of analytical psychology and Jungian studies to exercise social responsibility are to be realised.
Split subvarieties of group embeddings
Authors: Perrin Nicolas
Published: March 2015

Let

G
G

be a connected reductive group and

X
X

an equivariant compactification of

G
G

. In

X
X

, we study generalised and opposite generalised Schubert varieties, and their intersections called generalised Richardson varieties and projected generalised Richardson varieties. Any complete

G
G

-embedding has a canonical Frobenius splitting, and we prove that the compatibly split subvarieties are the generalised projected Richardson varieties extending a result of Knutson, Lam and Speyer to the situation.
Computing time-periodic solutions of a model for the vortex sheet with surface tension
Authors: Ambrose David , Kondrla Mark , Valle Michael
Published: March 2015

We compute time-periodic solutions of a simple model for the vortex sheet with surface tension. The model has the same dispersion relation as the full system of evolution equations, and it also has the same destabilizing nonlinearity (if the surface tension parameter were to be set to zero, then this nonlinearity would cause an analogue of the Kelvin-Helmholtz instability). The numerical method uses a gradient descent algorithm to minimize a functional which measures whether a solution of the system is time periodic. We find continua of genuinely time-periodic solutions bifurcating from equilibrium.
Automatic determination of NET (neutrophil extracellular traps) coverage in fluorescent microscopy images
Authors: Coelho Luis Pedro , Pato Catarina , Friães Ana , Neumann Ariane , von Köckritz-Blickwede Maren , Ramirez Mário , Carriço João André
Published: March 2015

Motivation: Neutrophil extracellular traps (NETs) are believed to be essential in controlling several bacterial pathogens. Quantification of NETs in vitro is an important tool in studies aiming to clarify the biological and chemical factors contributing to NET production, stabilization and degradation. This estimation can be performed on the basis of fluorescent microscopy images using appropriate labelings. In this context, it is desirable to automate the analysis to eliminate both the tedious process of manual annotation and possible operator-specific biases.

Results: We propose a framework for the automated determination of NET content, based on visually annotated images which are used to train a supervised machine-learning method. We derive several methods in this framework. The best results are obtained by combining these into a single prediction. The overall Q2 of the combined method is 93%. By having two experts label part of the image set, we were able to compare the performance of the algorithms to the human interoperator variability. We find that the two operators exhibited a very high correlation on their overall assessment of the NET coverage area in the images (R2 is 97%), although there were consistent differences in labeling at pixel level (Q2, which unlike R2 does not correct for additive and multiplicative biases, was only 89%).

Availability and implementation: Open source software (under the MIT license) is available at https://github.com/luispedro/Coelho2015_NetsDetermination for both reproducibility and application to new data.

Contact:  luis@luispedro.org

Supplementary information  :  Supplementary data are available at Bioinformatics online.
MAGNA++: Maximizing Accuracy in Global Network Alignment via both node and edge conservation
Authors: Vijayan V. , Saraph V. , Milenković T.
Published: March 2015

Motivation: Network alignment aims to find conserved regions between different networks. Existing methods aim to maximize total similarity over all aligned nodes (i.e. node conservation). Then, they evaluate alignment quality by measuring the amount of conserved edges, but only after the alignment is constructed. Thus, we recently introduced MAGNA (Maximizing Accuracy in Global Network Alignment) to directly maximize edge conservation while producing alignments and showed its superiority over the existing methods. Here, we extend the original MAGNA with several important algorithmic advances into a new MAGNA++ framework.

Results: MAGNA++ introduces several novelties: (i) it simultaneously maximizes any one of three different measures of edge conservation (including our recent superior S3 measure) and any desired node conservation measure, which further improves alignment quality compared with maximizing only node conservation or only edge conservation; (ii) it speeds up the original MAGNA algorithm by parallelizing it to automatically use all available resources, as well as by reimplementing the edge conservation measures more efficiently; (iii) it provides a friendly graphical user interface for easy use by domain (e.g. biological) scientists; and (iv) at the same time, MAGNA++ offers source code for easy extensibility by computational scientists.

Availability and implementation: http://www.nd.edu/∼cone/MAGNA++/

Contact: tmilenko@nd.edu
Solubis: optimize your protein
Authors: De Baets Greet , Van Durme Joost , van der Kant Rob , Schymkowitz Joost , Rousseau Frederic
Published: March 2015

Motivation: Protein aggregation is associated with a number of protein misfolding diseases and is a major concern for therapeutic proteins. Aggregation is caused by the presence of aggregation-prone regions (APRs) in the amino acid sequence of the protein. The lower the aggregation propensity of APRs and the better they are protected by native interactions within the folded structure of the protein, the more aggregation is prevented. Therefore, both the local thermodynamic stability of APRs in the native structure and their intrinsic aggregation propensity are a key parameter that needs to be optimized to prevent protein aggregation.

Results: The Solubis method presented here automates the process of carefully selecting point mutations that minimize the intrinsic aggregation propensity while improving local protein stability.

Availability and implementation: All information about the Solubis plugin is available at http://solubisyasara.switchlab.org/.

Contact:  joost.schymkowitz@switch.vib-kuleuven.be or Frederic.Rousseau@switch.vib-kuleuven.be

Supplementary information: Supplementary data are available at Bioinformatics online.