bluuebunny/crossref_metadata_2025 huggingface dataset:
Dielectric and structural properties of aqueous nonpolar solute mixtures
Authors: Shvab I. , Sadus Richard J.
Published: September 2012

The dielectric properties and molecular structure of water mixtures with different nonpolar solutes (methane and noble gases) are studied using molecular dynamics. The water-water, water-solute, and solute-solute interactions are calculated using the combination of a polarizable potential [J. Li, Z. Zhou, and R. J. Sadus, J. Chem. Phys. 127, 154509 (2007)10.1063/1.2786449] for water plus the Lennard-Jones potential. The effect of solute size and concentration on the solubility of the system, hydrogen bonding, dielectric constant, and dipole moment are investigated over a temperature range of 278–750 K and solute percentage mole fractions up to 30%. Solute particles affect the structure of water, resulting in the compression of oxygen-oxygen and oxygen-hydrogen radial distribution functions. The influence of the solute extends both to relatively low concentrations and high temperatures. The coordination numbers of aqueous solutions of the nonpolar solutes appear to be proportional to the size of the solute particles. Our study shows the destructive influence of the nonpolar solute on both the tetrahedral water structure and hydrogen bond formation at solute concentrations greater than 30%. The presence of nonpolar particles typically decreases both the dielectric constant and dipole moment. The decrease of dielectric constant and water dipole moment is directly proportional to the solute concentration and temperature.
Pulsed laser ablation of complex oxides: The role of congruent ablation and preferential scattering for the film stoichiometry
Authors: Wicklein S. , Sambri A. , Amoruso S. , Wang X. , Bruzzese R. , Koehl A. , Dittmann R.
Published: September 2012

By combining structural and chemical thin film analysis with detailed plume diagnostics and modeling of the laser plume dynamics, we are able to elucidate the different physical mechanisms determining the stoichiometry of the complex oxides model material SrTiO3 during pulsed laser deposition. Deviations between thin film and target stoichiometry are basically a result of two effects, namely, incongruent ablation and preferential scattering of lighter ablated species during their motion towards the substrate in the O2 background gas. On the one hand, a progressive preferential ablation of the Ti species with increasing laser fluence leads to a regime of Ti-rich thin film growth at larger fluences. On the other hand, in the low laser fluence regime, a more effective scattering of the lighter Ti plume species results in Sr rich films.
Perspective: Advances and challenges in treating van der Waals dispersion forces in density functional theory
Authors: Klimeš Jiří , Michaelides Angelos
Published: September 2012

Electron dispersion forces play a crucial role in determining the structure and properties of biomolecules, molecular crystals, and many other systems. However, an accurate description of dispersion is highly challenging, with the most widely used electronic structure technique, density functional theory (DFT), failing to describe them with standard approximations. Therefore, applications of DFT to systems where dispersion is important have traditionally been of questionable accuracy. However, the last decade has seen a surge of enthusiasm in the DFT community to tackle this problem and in so-doing to extend the applicability of DFT-based methods. Here we discuss, classify, and evaluate some of the promising schemes to emerge in recent years. A brief perspective on the outstanding issues that remain to be resolved and some directions for future research are also provided.
Electronic transitions of platinum monoboride
Authors: Ng Y. W. , Wong Yat Sing , Pang H. F. , Cheung A. S.-C.
Published: September 2012

The electronic transition spectrum of platinum monoboride (PtB) radical has been observed for the first time. Using laser vaporization/reaction free jet expansion and laser induced fluorescence spectroscopy, the optical spectrum of PtB in the visible region between 455 and 520 nm has been studied. Gas-phase PtB molecule was produced by the reaction of diborane (B2H6) seeded in argon and laser ablated platinum atom. Seven vibrational bands of the Pt11B radical have been recorded and analyzed. The observation of Pt isotopic molecules and the Pt10B isotope confirmed the carrier of the bands. Two different transition systems, namely: the [20.2]3/2–X2Σ+ and the [21.2]1/2–X2Σ+ systems were identified. PtB was determined to have an X2Σ+ ground state and the bond length, re, was determined to be 1.741 Å.
Experimental and theoretical studies of ammonia generation: Reactions of H2 with neutral cobalt nitride clusters
Authors: Yin Shi , Xie Yan , Bernstein Elliot R.
Published: September 2012

Ammonia generation through reaction of H2 with neutral cobalt nitride clusters in a fast flow reactor is investigated both experimentally and theoretically. Single photon ionization at 193 nm is used to detect neutral cluster distributions through time-of-flight mass spectrometry. ComNn clusters are generated through laser ablation of Co foil into N2/He expansion gas. Mass peaks ComNH2 (m = 6, 10) and ComNH3 (m = 7, 8, 9) are observed for reactions of H2 with the ComNn clusters. Observation of these products indicates that clusters ComN (m = 7, 8, 9) have high reactivity with H2 for ammonia generation. Density functional theory (DFT) calculations are performed to explore the potential energy surface for the reaction Co7N + 3/2H2 → Co7NH3, and a barrierless, thermodynamically favorable pathway is obtained. An odd number of hydrogen atoms in ComNH3 (m = 7, 8, 9) probably come from the hydrogen molecule dissociation on two active cobalt nitride clusters based on the DFT calculations. Both experimental observations and theoretical calculations suggest that hydrogen dissociation on two active cobalt nitride clusters is the key step to form NH3 in a gas phase reaction. A catalytic cycle for ammonia generation from N2 and H2 on a cobalt metal catalyst surface is proposed based on our experimental and theoretical investigations.
Symmetry interplay in Brownian photomotors: From a single-molecule device to ensemble transport
Authors: Dekhtyar Marina L. , Rozenbaum Viktor М.
Published: September 2012

Unlike most of Brownian motor models in which the state of a point particle is described by a single scalar fluctuating parameter, we consider light-induced dichotomic fluctuations of electron density distributions in an extended molecule moving in the electrostatic periodic potential of a polar substrate. This model implies that the potential energy profiles of two motor states differ substantially and their symmetry is dictated by the interplay between the symmetries of the substrate potential and of molecular electronic states. As shown, a necessary condition for the occurrence of directed motion, the asymmetry of the potential energy profiles, is satisfied for (i) symmetric electron density distributions in molecules on asymmetric substrates and (ii) asymmetric electron density distributions in molecules on symmetric substrates. In the former case, the average velocity of directed motion is independent of molecular orientations and the ensemble of molecules moves as a whole, whereas in the latter case, oppositely oriented molecules move counterdirectionally thus causing the ensemble to diffuse. Using quantum chemical data for a specific organic-based photomotor as an example, we demonstrate that the behavior of molecular ensembles is controllable by switching on/off resonance laser radiation: they can be transported as a whole or separated into differently oriented molecules depending on the ratio of symmetric and antisymmetric contributions to the substrate electrostatic potential and to the molecular electron density distributions.
Infrared-to-visible upconversion emission in Er3+ doped TeO2-WO3-Bi2O3 glasses with silver nanoparticles
Authors: de Campos Vitor P. P. , Kassab Luciana R. P. , de Assumpção Thiago A. A. , da Silva Diego S. , de Araújo Cid B.
Published: September 2012

The influence of silver nanoparticles (NPs) on the frequency upconversion luminescence in Er3+ doped TeO2-WO3-Bi2O3 glasses is reported. The effect of the NPs on the Er3+ luminescence was controlled by appropriate heat-treatment of the samples. Enhancement up to 700% was obtained for the upconverted emissions at 527, 550, and 660 nm, when a laser at 980 nm is used for excitation. Since the laser frequency is far from the NPs surface plasmon resonance frequency, the luminescence enhancement is attributed to the local field increase in the proximity of the NPs and not to energy transfer from the NPs to the emitters as is usually reported. This is the first time that the effect is investigated for tellurite-tungstate-bismutate glasses and the enhancement observed is the largest reported for a tellurium oxide based glass.
Degradation analysis and characterization of multifilamentary conduction patterns in high-field stressed atomic-layer-deposited TiO2/Al2O3 nanolaminates on GaAs
Authors: Miranda E. , Suñé J. , Das T. , Mahata C. , Maiti C. K.
Published: September 2012

In this paper, the effects of applying a high-field electrical stress on TiO2/Al2O3 nanolaminates grown by atomic layer deposition onto a p-type GaAs substrate are investigated. First, it is shown that the current-time (I-t) characteristic of the devices during a constant voltage stress follows the extended Curie-von Schweidler law for dielectric degradation. The application of voltage sweeps from negative to positive bias and back also reveals an hysteretic behavior of the current-voltage (I-V) characteristic typical of the resistive switching mechanism ocurring in these and others high permittivity oxide films. Second, we show that after the detection of the breakdown event the capacitors exhibit a random spot pattern on the top metal electrode (Al) associated with the generation of multifilamentary conduction paths running across the insulating film. The number of generated spots depends on the magnitude of the electrical stress and for a sufficiently large density, it is possible to demonstrate that they are spatially uncorrelated. The analysis is carried out using spatial statistics techniques such as the intensity plot, the interspot distance histogram, and the pair correlation function.
Real-space mapping of nanoplasmonic hotspots via optical antenna-gap loading
Authors: Mastel S. , Grefe S. E. , Cross G. B. , Taber A. , Dhuey S. , Cabrini S. , Schuck P. J. , Abate Y.
Published: September 2012

Plasmonic hotspots located in the nanogaps of infrared optical antennas are mapped in the near-field. The enhanced evanescent field resonance is shown to depend strongly on excitation wavelength, the excitation and detection laser polarization, and gap size. In addition, we demonstrate that in nanogap hotspot imaging using scattering probes, the probe tip can be considered as a load in the gap of the antenna, and the impedance of the load can then be tuned from inductive to capacitive or vice versa by changing the dielectric value of the tip load. Experimental results are in agreement with finite-difference time-domain simulations.
Nondestructive measurement of the minority carrier diffusion length in InP/InGaAs/InP double heterostructures
Authors: Zemel A. , Mizrahi U. , Fishman T.
Published: September 2012

The present work demonstrates a simple nondestructive method for the measurement of the minority carrier diffusion length in InP/InGaAs/InP heterostructures. In this measurement technique, a beam of helium-neon laser is applied on the 1 μm-thick InP cap layer of the InP/InGaAs/InP heterostructure, and the resulted InGaAs photoluminescence image is detected by an InGaAs focal plane array. The values of the minority carrier diffusion length which were deduced from the image scans will be presented and discussed. With a further work, this technique could become a useful tool for the selection of InP/InGaAs/InP layered structures prior to the fabrication of InGaAs detectors.
GaN-based light emitting diodes with micro- and nano-patterned structures by femtosecond laser nonlinear decomposition
Authors: Chen Jiun-Ting , Lai Wei-Chih , Chang Yun-Chorng , Sheu Jinn-Kong , Sen Wen-Chih
Published: September 2012

The multiple micro/nano-patterning on p-GaN surface by femtosecond (fs) laser irradiation through a micro-ball lens array (MBLA) mask has been established to improve the light extraction efficiency of GaN-based light-emitting diodes (LEDs). This technique was meant for the high-speed surface micro/nano-patterning of a p-GaN surface on a large area using fs laser irradiation. Compared with conventional LEDs with flat surfaces, dual-scale roughened structures on p-GaN surface LEDs used in the present experiment scatter and increase the effective critical angle, increasing the escape probability of photons. The relationship of the hole size on p-GaN surface and the refractive index of the MBLA material would be also discussed. With an injection current of 20 mA, the output power of the experimental LEDs markedly improved by a magnitude of 48% compared with conventional GaN-based LEDs.
Thermally activated control of microfluidic friction
Authors: Dey Ranabir , DasGupta Sunando , Chakraborty Suman
Published: September 2012

Contrary to the common belief that fluid friction unilaterally determines the thermal characteristics of a microfluidic device, we show here that fluid frictional characteristics of a microfluidic device may essentially be thermally tuned, delineating a non-intuitive two-way coupling. Our experiments reveal that the interfacial phenomena triggered by thermal alteration of interfaces with certain topographical and wettability characteristics may reduce the interfacial friction to a considerable extent. This has far-ranging scientific and technological consequences towards obtaining improved throughput in microfluidic devices with applications ranging from biotechnology to electronics cooling.
Laser triggered sequential folding of microstructures
Authors: Laflin Kate E. , Morris Christopher J. , Muqeem Tanziyah , Gracias David H.
Published: September 2012

In order to fabricate complex origami inspired devices, it is necessary to control folding pathways and enable sequential folding. We demonstrate sequential folding of microstructures from afar by the directed heating of pre-stressed hinges using low power, 40–80 mW handheld, commercial lasers. We observed that the hinge-actuation and consequently folding time varied with laser irradiance, wavelength, and distance. We highlight possible applications by sequential folding of patterned and nested microstructures.
Broadband super-Planckian thermal emission from hyperbolic metamaterials
Authors: Guo Yu , Cortes Cristian L. , Molesky Sean , Jacob Zubin
Published: September 2012

We develop the fluctuational electrodynamics of metamaterials with hyperbolic dispersion and show the existence of broadband thermal emission beyond the black body limit in the near field. This arises due to the thermal excitation of unique bulk metamaterial modes, which do not occur in conventional media. We consider a practical realization of the hyperbolic metamaterial and estimate that the effect will be observable using the characteristic dispersion (topological transitions) of the metamaterial states. Our work paves the way for engineering the near-field thermal emission using metamaterials.
Interplay between intrinsic and stacking-fault magnetic domains in bi-layered manganites
Authors: Hossain M. A. , Burkhardt Mark H. , Sarkar S. , Ohldag H. , Chuang Y.-D. , Scholl A. , Young A. T. , Doran A. , Dessau D. S. , Zheng H. , Mitchell J. F. , Dürr H. A. , Stöhr J.
Published: September 2012

We present a low temperature x-ray photoemission electron microscopy study of the bi-layered manganite compound La1.2Sr1.8Mn2O7 (BL-LSMO) to investigate the influence of stacking faults, which are structurally and magnetically different from the bi-layered host. In BL-LSMO, small magnetic moment persists to T*=300 K, well above the Curie temperature of 120 K (TC). Our magnetic images show that 3D stacking faults are responsible for the T* transition. Furthermore, close to the TC, stacking faults are well coupled to the bi-layered host with latter magnetic domains controlling the spin direction of the stacking faults. Contrary to recent reports, we find that stacking faults do not seed magnetic domains in the host via an exchange spring mechanism and the intrinsic TC of the BL-LSMO is not lower than 120 K.
Field-controllable exchange bias in epitaxial Fe films grown on GaAs
Authors: Choi Seonghoon , Yoo Taehee , Khym S. , Lee Sanghoon , Liu X. , Furdyna J. K.
Published: September 2012

We report that exchange bias observed in epitaxial Fe films grown on GaAs (001) substrates can be controlled by the direction of the cooling field. The effect is investigated by measuring the shift of field-cooled hysteresis loops toward specific field directions, as revealed by field scans of the planar Hall resistance at 3 K. The value of the unidirectional magnetic anisotropy corresponding to such field-controllable exchange is obtained from the angular dependence of the planar Hall effect.
Detection of spin-orbit coupling of surface electron layer via reciprocal spin Hall effect in InN films
Authors: Mei F. H. , Tang N. , Wang X. Q. , Duan J. X. , Zhang S. , Chen Y. H. , Ge W. K. , Shen B.
Published: September 2012

Swirly photocurrent in InN films arising from reciprocal spin Hall effect (RSHE) is observed under normal incidence of circularly polarized light at room temperature. It is found that the swirly current is a superposition of the RSHE currents from the surface and bulk layer of InN. The effective spin-orbit coupling coefficient (SOC) in the surface electron layer is suggested to be of opposite sign to that in the bulk. The results constitute a comprehensive understanding of the role of surface electron layer in spin transport in InN. This work reveals an approach to explore spin-orbit coupling in systems like InN.
Effects of microwave annealing on electrical enhancement of amorphous oxide semiconductor thin film transistor
Authors: Teng Li-Feng , Liu Po-Tsun , Lo Yuan-Jou , Lee Yao-Jen
Published: September 2012

By using microwave annealing technology instead of thermal furnace annealing, this work elucidates the electrical characteristics of amorphous InGaZnO thin film transistor (a-IGZO TFT) with a carrier mobility of 13.5 cm2/Vs, threshold voltage of 3.28 V, and subthreshold swing of 0.43 V/decade. This TFT performance with microwave annealing of 100 s is well competitive with its counterpart with furnace annealing at 450 °C for 1 h. A physical mechanism for the electrical improvement is also deduced. Owing to its low thermal budget and selective heating to materials of interest, microwave annealing is highly promising for amorphous oxide in semiconductor TFT manufacturing.
Minimizing scattering from antireflective surfaces replicated from low-aspect-ratio black silicon
Authors: Christiansen Alexander B. , Clausen Jeppe , Asger Mortensen N. , Kristensen Anders
Published: September 2012

The scattering properties of randomly structured antireflective black silicon polymer replica have been investigated. Using a two-step casting process, the structures can be replicated in Ormocomp on areas of up to 3 in. in diameter. Fourier analysis of scanning electron microscopy images of the structures shows that the scattering properties of the surfaces are related to the spatial periods of the nanostructures. Structures with a dominating spatial period of 160 nm, a height of 200 nm, and aspect ratio of 1.3 show insignificant scattering of light with wavelength above 500 nm and lower the reflectance by a factor of two.
On the nature of enthalpy relaxation below and above the glass transition of metallic glasses
Authors: Mitrofanov Yu. P. , Makarov A. S. , Khonik V. A. , Granato A. V. , Joncich D. M. , Khonik S. V.
Published: September 2012

Within the framework of the interstitialcy theory, we derived a simple and testable expression for the heat flow (enthalpy relaxation rate) occurring upon warming of glass at a constant rate. Formally, this heat flow is mostly determined by the shear moduli of glass and parent crystal. The underlying physical reason is relaxation of an intrinsic interstitialcy-like defect system. An extensive check of the derived heat flow law for temperatures near the glass transition showed good agreement with the experiment specially performed on two Pd-based metallic glasses.
Self-assembled NaNbO3-Nb2O5 (ferroelectric-semiconductor) heterostructures grown on LaAlO3 substrates
Authors: Wang Zhiguang , Li Yanxi , Chen Bo , Viswan Ravindranath , Li Jie-Fang , Viehland D.
Published: September 2012

We deposited NaNbO3 (NNO)-Nb2O5 (NO) self-assembled heterostructures on LaAlO3 (LAO) to form ferroelectric-semiconductor vertically integrated nanostructures. The NNO component formed as nanorods embedded in a NO matrix. X-ray diffraction confirmed epitaxial growth of both NNO and NO phases. Phase distribution was detected by scanning electron microscopy. The NNO/NO volume ratio was strongly dependent on the deposition temperature due to the volatility of sodium. Piezoelectric force microscopy revealed a good piezoelectric response in the NNO component with a piezoelectric coefficient of D33 ≈ 12 pm/V, with SrRuO3 (SRO) acting as bottom electrode. The current-voltage characterization of NNO-NO/SRO-LAO showed a typical diode rectifying behavior.
Enhanced thermoelectric performance through energy-filtering effects in nanocomposites dispersed with metallic particles
Authors: Liu M. , Qin X. Y.
Published: September 2012

The thermoelectric properties of semiconductor materials with metallic nanoinclusions were investigated by using the Boltzmann transport equation under the relaxation time approximation. The results showed that the Seebeck coefficient can be significantly enhanced due to interface potential barrier induced by metallic nanoinclusions, leading to the optimized power factor at T < 700 K as barrier height is around kBT larger than the Fermi energy (here, kB is the Boltzmann constant). Additionally, it was found that high-concentration nanoinclusions with radius 1–2 nm can effectively enhance the thermoelectric performance of nanocomposites through energy-selective carrier scattering.
The charged interface between Pt and water: First principles molecular dynamics simulations
Authors: Ikeshoji Tamio , Otani Minoru , Hamada Ikutaro , Sugino Osamu , Morikawa Yoshitada , Okamoto Yasuharu , Qian Yumin , Yagi Ichizo
Published: September 2012

The charged interface between a platinum electrode and an aqueous solution is investigated by first-principles molecular dynamics simulations in which charges in the system are controlled by the effective screening medium method under periodic boundary conditions. H3O+ and OH are located above or on the Pt surface. Water molecules rotate to screen the electric field induced by the charge accumulated on the Pt surface. The time-averaged electrostatic potential near the Pt surface is structured with a flattened “bulk” region. The potential difference between the Pt Fermi level and the bulk potential is proportional to the charge and is used to estimate the Pt electrode potential via the PZC (potential of the zero charge). The surface charge significantly polarizes the water molecules near the Pt surface. The OH stretching frequency of molecules on the negatively charged (7 ∼ 14 μC/cm2) Pt electrode shift to lower values (red shift) by 100 ∼ 200 cm−1. For the positively charged Pt lattice, a complex feature results from a charge transfer reaction that takes place there. The electrode structure is also influenced by accumulated charge as the distance between the top surface Pt layer and the next layer underneath increases for both the negatively and positively charged surfaces.
Synthesis, Structure, Physical Properties, and Displacement Current Measurement of an n-Type Organic Semiconductor: 2:3,5:6-Bis(1,1-dicyanoethylene-2,2-dithiolate)-quinone
Authors: Xiao Jinchong , Azuma Yasuo , Liu Yi , Li Gang , Wei Fengxia , Tan Ke Jie , Kloc Christian , Zhang Hua , Majima Yutaka , Zhang Qichun
Published: September 2012

An n-type organic semiconductor 2:3,5:6-bis(1,1-dicyanoethylene-2,2-dithiolate)-quinone (BDQ) has been successfully synthesised and characterised. The single crystal structure of BDQ, determined by single-crystal X-ray crystallography, indicated that BDQ is a planar molecule with strong face-to-face π-π stacking (3.40 Å) and S···S interactions (3.66 Å) between neighbouring molecules, which might be in favour of the effective charge transport. The UV-vis spectrum shows that BDQ has shoulder absorption up to 550 nm (2.25 eV). The electrochemical property displays that the HOMO-LUMO gap of BDQ obtained from the half-wave redox potential is 1.92 eV. The displacement current measurement of BDQ-based devices is demonstrated and discussed.
Selective transport capacity for K+ over Na+ is linked to the expression levels of PtSOS1 in halophyte Puccinellia tenuiflora
Authors: Guo Qiang , Wang Pei , Ma Qing , Zhang Jin-Lin , Bao Ai-Ke , Wang Suo-Min
Published: September 2012

The plasma membrane Na+/H+ antiporter (SOS1) was shown to be a Na+ efflux protein and also involved in K+ uptake and transport. PtSOS1 was characterised from Puccinellia tenuiflora (Griseb.) Scribn. et Merr., a monocotyledonous halophyte that has a high selectivity for K+ over Na+ by roots under salt stress. To assess the contribution of PtSOS1 to the selectivity for K+ over Na+, the expression levels of PtSOS1 and Na+, K+ accumulations in P. tenuiflora exposed to different concentrations of NaCl, KCl or NaCl plus KCl were analysed. Results showed that the expression levels of PtSOS1 in roots increased significantly with the increase of external NaCl (25–150 mM), accompanied by an increase of selective transport (ST) capacity for K+ over Na+ by roots. Transcription levels of PtSOS1 in roots and ST values increased under 0.1–1 mM KCl, then declined sharply under 5–10 mM KCl. Under 150 mM NaCl, PtSOS1 expression levels in roots and ST values at 0.1 mM KCl was significantly lower than that at 5 mM KCl with the prolonging of treatment time. A significant positive correlation was found between root PtSOS1 expression levels and ST values under various concentrations of NaCl, KCl or 150 mM NaCl plus 0.1 or 5 mM KCl treatments. Therefore, it is proposed that PtSOS1 is the major component of selective transport capacity for K+ over Na+ and hence, salt tolerance of P. tenuiflora. Finally, we hypothesise a function model of SOS1 in regulating K+ and Na+ transport system in the membrane of xylem parenchyma cells by sustaining the membrane integrity; it also appears that this model could reasonably explain the phenomenon of Na+ retrieval from the xylem when plants are exposed to severe salt stress.
Differential responses of the mangrove Avicennia marina to salinity and abscisic acid
Authors: Reef Ruth , Schmitz Nele , Rogers Britt A. , Ball Marilyn C. , Lovelock Catherine E.
Published: September 2012

Salinisation of the soil can cause plant water deficits, ion and nutrient imbalances and toxic reactions. The halophyte, Avicennia marina (Forssk.) Vierh., is a mangrove that tolerates a wide range of soil salinities. In order to understand how salinity affects plant growth and functioning and how salinity responses are influenced by the water deficit signalling hormone abscisic acid (ABA) we grew A. marina seedlings under two non-growth limiting salinities: 60% seawater and 90% seawater and with and without exogenously supplied ABA. We measured growth, photosynthesis, sap flow, aquaporin gene expression, hydraulic anatomy and nutrient status as well as sap ABA concentrations. ABA addition resulted in a drought phenotype (reduced sap flow, transpiration rates and photosynthesis and increased water use efficiency and aquaporin expression). In contrast, growth in high salinity did not lead to responses that are typical for water deficits, but rather, could be characterised as drought avoidance strategies (no reduction in sap flow, transpiration rates and photosynthesis and reduced aquaporin expression). Tissue nutrient concentrations were higher in seedlings grown at high salinities. We did not find evidence for a role for ABA in the mangrove salinity response, suggesting ABA is not produced directly in response to high concentrations of NaCl ions.
Competency requirements for middle and senior managers in community health services
Authors: Liang Zhanming , Howard Peter F. , Koh Lee C. , Leggat Sandra
Published: September 2012

The Australian health system has been subjected to rapid changes in the last 20 years to meet increasingly unmet health needs. Improvement of the efficiency and comprehensiveness of community-based services is one of the solutions to reducing the increasing demand for hospital care. Competent managers are one of the key contributors to effective and efficient health service delivery. However, the understanding of what makes a competent manager, especially in the community health services (CHS), is limited. Using an exploratory and mixed-methods approach, including focus group discussions and an online survey, this study identified five key competencies required by senior and mid-level CHS managers in metropolitan, regional and rural areas of Victoria: Interpersonal, communication qualities and relationship management; Operations, administration and resource management; Knowledge of the health care environment; Leading and managing change; and Evidence-informed decision-making. This study confirms that core competencies do exist across different management levels and improves our understanding of managerial competency requirements for middle to senior CHS managers, with implications for current and future health service management workforce development.
Calcium buffering properties of sarcoplasmic reticulum and calcium-induced Ca2+ release during the quasi-steady level of release in twitch fibers from frog skeletal muscle
Authors: Fénelon Karine , Lamboley Cédric R.H. , Carrier Nicole , Pape Paul C.
Published: September 2012

Experiments were performed to characterize the properties of the intrinsic Ca2+ buffers in the sarcoplasmic reticulum (SR) of cut fibers from frog twitch muscle. The concentrations of total and free calcium ions within the SR ([CaT]SR and [Ca2+]SR) were measured, respectively, with the EGTA/phenol red method and tetramethylmurexide (a low affinity Ca2+ indicator). Results indicate SR Ca2+ buffering was consistent with a single cooperative-binding component or a combination of a cooperative-binding component and a linear binding component accounting for 20% or less of the bound Ca2+. Under the assumption of a single cooperative-binding component, the most likely resting values of [Ca2+]SR and [CaT]SR are 0.67 and 17.1 mM, respectively, and the dissociation constant, Hill coefficient, and concentration of the Ca-binding sites are 0.78 mM, 3.0, and 44 mM, respectively. This information can be used to calculate a variable proportional to the Ca2+ permeability of the SR, namely d[CaT]SR/dt ÷ [Ca2+]SR (denoted release permeability), in experiments in which only [CaT]SR or [Ca2+]SR is measured. In response to a voltage-clamp step to −20 mV at 15°C, the release permeability reaches an early peak followed by a rapid decline to a quasi-steady level that lasts ∼50 ms, followed by a slower decline during which the release permeability decreases by at least threefold. During the quasi-steady level of release, the release amplitude is 3.3-fold greater than expected from voltage activation alone, a result consistent with the recruitment by Ca-induced Ca2+ release of 2.3 SR Ca2+ release channels neighboring each channel activated by its associated voltage sensor. Release permeability at −60 mV increases as [CaT]SR decreases from its resting physiological level to ∼0.1 of this level. This result argues against a release termination mechanism proposed in mammalian muscle fibers in which a luminal sensor of [Ca2+]SR inhibits release when [CaT]SR declines to a low level.
cAMP controls rod photoreceptor sensitivity via multiple targets in the phototransduction cascade
Authors: Astakhova Luba A. , Samoiliuk Evgeniia V. , Govardovskii Victor I. , Firsov Michael L.
Published: September 2012

In early studies, both cyclic AMP (cAMP) and cGMP were considered as potential secondary messengers regulating the conductivity of the vertebrate photoreceptor plasma membrane. Later discovery of the cGMP specificity of cyclic nucleotide–gated channels has shifted attention to cGMP as the only secondary messenger in the phototransduction cascade, and cAMP is not considered in modern schemes of phototransduction. Here, we report evidence that cAMP may also be involved in regulation of the phototransduction cascade. Using a suction pipette technique, we recorded light responses of isolated solitary rods from the frog retina in normal solution and in the medium containing 2 µM of adenylate cyclase activator forskolin. Under forskolin action, flash sensitivity rose more than twofold because of a retarded photoresponse turn-off. The same concentration of forskolin lead to a 2.5-fold increase in the rod outer segment cAMP, which is close to earlier reported natural day/night cAMP variations. Detailed analysis of cAMP action on the phototransduction cascade suggests that several targets are affected by cAMP increase: (a) basal dark phosphodiesterase (PDE) activity decreases; (b) at the same intensity of light background, steady background-induced PDE activity increases; (c) at light backgrounds, guanylate cyclase activity at a given fraction of open channels is reduced; and (d) the magnitude of the Ca2+ exchanger current rises 1.6-fold, which would correspond to a 1.6-fold elevation of [Ca2+]in. Analysis by a complete model of rod phototransduction suggests that an increase of [Ca2+]in might also explain effects (b) and (c). The mechanism(s) by which cAMP could regulate [Ca2+]in and PDE basal activity is unclear. We suggest that these regulations may have adaptive significance and improve the performance of the visual system when it switches between day and night light conditions.
Simulated annealing reveals the kinetic activity of SGLT1, a member of the LeuT structural family
Authors: Longpré Jean-Philippe , Sasseville Louis J. , Lapointe Jean-Yves
Published: September 2012

The Na+/glucose cotransporter (SGLT1) is the archetype of membrane proteins that use the electrochemical Na+ gradient to drive uphill transport of a substrate. The crystal structure recently obtained for vSGLT strongly suggests that SGLT1 adopts the inverted repeat fold of the LeuT structural family for which several crystal structures are now available. What is largely missing is an accurate view of the rates at which SGLT1 transits between its different conformational states. In the present study, we used simulated annealing to analyze a large set of steady-state and pre–steady-state currents measured for human SGLT1 at different membrane potentials, and in the presence of different Na+ and α-methyl-d-glucose (αMG) concentrations. The simplest kinetic model that could accurately reproduce the time course of the measured currents (down to the 2 ms time range) is a seven-state model (C1 to C7) where the binding of the two Na+ ions (C4→C5) is highly cooperative. In the forward direction (Na+/glucose influx), the model is characterized by two slow, electroneutral conformational changes (59 and 100 s−1) which represent reorientation of the free and of the fully loaded carrier between inside-facing and outside-facing conformations. From the inward-facing (C1) to the outward-facing Na-bound configuration (C5), 1.3 negative elementary charges are moved outward. Although extracellular glucose binding (C5→C6) is electroneutral, the next step (C6→C7) carries 0.7 positive charges inside the cell. Alignment of the seven-state model with a generalized model suggested by the structural data of the LeuT fold family suggests that electrogenic steps are associated with the movement of the so-called thin gates on each side of the substrate binding site. To our knowledge, this is the first model that can quantitatively describe the behavior of SGLT1 down to the 2 ms time domain. The model is highly symmetrical and in good agreement with the structural information obtained from the LeuT structural family.
Use-dependent block of the voltage-gated Na+ channel by tetrodotoxin and saxitoxin: Effect of pore mutations that change ionic selectivity
Authors: Huang Chien-Jung , Schild Laurent , Moczydlowski Edward G.
Published: September 2012

Voltage-gated Na+ channels (NaV channels) are specifically blocked by guanidinium toxins such as tetrodotoxin (TTX) and saxitoxin (STX) with nanomolar to micromolar affinity depending on key amino acid substitutions in the outer vestibule of the channel that vary with NaV gene isoforms. All NaV channels that have been studied exhibit a use-dependent enhancement of TTX/STX affinity when the channel is stimulated with brief repetitive voltage depolarizations from a hyperpolarized starting voltage. Two models have been proposed to explain the mechanism of TTX/STX use dependence: a conformational mechanism and a trapped ion mechanism. In this study, we used selectivity filter mutations (K1237R, K1237A, and K1237H) of the rat muscle NaV1.4 channel that are known to alter ionic selectivity and Ca2+ permeability to test the trapped ion mechanism, which attributes use-dependent enhancement of toxin affinity to electrostatic repulsion between the bound toxin and Ca2+ or Na+ ions trapped inside the channel vestibule in the closed state. Our results indicate that TTX/STX use dependence is not relieved by mutations that enhance Ca2+ permeability, suggesting that ion–toxin repulsion is not the primary factor that determines use dependence. Evidence now favors the idea that TTX/STX use dependence arises from conformational coupling of the voltage sensor domain or domains with residues in the toxin-binding site that are also involved in slow inactivation.
THE GALFA-H i COMPACT CLOUD CATALOG
Authors: Saul Destry R. , Peek J. E. G. , Grcevich J. , Putman M. E. , Douglas K. A. , Korpela E. J. , Stanimirović S. , Heiles C. , Gibson S. J. , Lee M. , Begum A. , Brown A. R. H. , Burkhart B. , Hamden E. T. , Pingel N. M. , Tonnesen S.
Published: September 2012

We present a catalog of 1964 isolated, compact neutral hydrogen clouds from the Galactic Arecibo L-Band Feed Array Survey Data Release One. The clouds were identified by a custom machine-vision algorithm utilizing the difference of Gaussian kernels to search for clouds smaller than 20′. The clouds have velocities typically between |V
LSR| =20 and 400 km s−1, line widths of 2.5–35 km s−1, and column densities ranging from 1 to 35 × 1018 cm−2. The distances to the clouds in this catalog may cover several orders of magnitude, so the masses may range from less than a solar mass for clouds within the Galactic disk, to greater than 104 
M
☉ for high-velocity clouds (HVCs) at the tip of the Magellanic Stream. To search for trends, we separate the catalog into five populations based on position, velocity, and line width: HVCs; galaxy candidates; cold low-velocity clouds (LVCs); warm, low positive-velocity clouds in the third Galactic quadrant; and the remaining warm LVCs. The observed HVCs are found to be associated with previously identified HVC complexes. We do not observe a large population of isolated clouds at high velocities as some models predict. We see evidence for distinct histories at low velocities in detecting populations of clouds corotating with the Galactic disk and a set of clouds that is not corotating.
Exchange bias induced by O ion implantation in ferromagnetic thin films
Authors: Demeter J , Menéndez E , Schrauwen A , Teichert A , Steitz R , Vandezande S , Wildes A R , Vandervorst W , Temst K , Vantomme A
Published: September 2012

Exchange bias (EB) is induced by oxygen implantation in three different ferromagnetic materials: polycrystalline Co, highly textured Co and polycrystalline Ni. These systems are compared in order to study the influence of the grain boundary density and the intrinsic ferromagnet/antiferromagnet coupling strength on the implantation-induced EB. Special emphasis is given to the role of the implantation profile in the EB properties. The implantation profile is thoroughly characterized and its correlation with the magnetic depth profile, i.e. the magnetization as a function of depth, for different magnetic states is studied. This is achieved by modelling the implanted system as a layered system. In the three systems, the magnetization reversal mechanism is studied. In this way the effect of the implantation process on the reversal mechanism is unraveled. Irrespective of the particular system, the magnetization reverses solely by domain wall nucleation and motion, as opposed to Co/CoO bilayer systems, where a change in the reversal mechanism is observed upon the first reversal.
Polariton lasers. Hybrid light–matter lasers without inversion
Authors: Bajoni Daniele
Published: September 2012

The full text of this corrigendum is available in the PDF.
Edge stability analysis of ITER baseline plasma simulations
Authors: Saarelma S. , Casper T. , Chapman I.T. , Huijsmans G.T.A , Kwon O. , Lee J. , Loarte A.
Published: September 2012

A stability analysis using equilibria from CORSICA transport simulations finds that the maximum stable pedestal pressure in ITER 15 MA baseline plasma is 110 kPa corresponding to a pedestal temperature of 5.9 keV. The height of the stable pedestal is robust for the assumption of the pedestal height varying only by about 10% if the width of the pedestal is varied by 30%. A conducting first wall has a stabilizing effect on the peeling–ballooning modes that limit the edge pressure. However, the stabilization is unlikely to significantly change the stability limits, but could affect the ELM dynamics by lowering the growth rate of the ELM triggering peeling–ballooning modes. The entire pedestal region is stable against n = ∞ ballooning modes for all studied pedestal temperatures. This is due to the high bootstrap current keeping the magnetic shear in the region of large pressure gradient.
Deuterium retention in tungsten and tungsten–tantalum alloys exposed to high-flux deuterium plasmas
Authors: Zayachuk Y. , 't Hoen M.H.J. , Zeijlmans van Emmichoven P.A. , Uytdenhouwen I. , van Oost G.
Published: September 2012

A direct comparison of deuterium retention in samples of tungsten and two grades of tungsten–tantalum alloys—W–1% Ta and W–5% Ta, exposed to deuterium plasmas (ion flux ∼1024 m−2 s−1, ion energy at the biased target ∼50 eV) at the plasma generator Pilot-PSI was performed using thermal desorption spectroscopy (TDS). No systematic difference in terms of total retention in tungsten and tungsten–tantalum was identified. The measured retention value for each grade did not deviate by more than 24% from the value averaged over the three grades exposed to the same conditions. No additional desorption peaks appeared in the TDS spectra of the W–Ta samples as compared with the W target, indicating that no additional kinds of traps are introduced by the alloying of W with Ta. In the course of the experiment the same samples were exposed to the same plasma conditions several times, and it is demonstrated that samples with the history of prior exposures yield an increase in deuterium retention of up to 130% under the investigated conditions compared with the samples that were not exposed before. We consider this as evidence that exposure of the considered materials to ions with energy below the displacement threshold generates additional traps for deuterium. The positions of the release peaks caused by these traps are similar for W and W–Ta, which indicates that the corresponding traps are of the same kind.
POLARIMETRIC IMAGING OF LARGE CAVITY STRUCTURES IN THE PRE-TRANSITIONAL PROTOPLANETARY DISK AROUND PDS 70: OBSERVATIONS OF THE DISK*
Authors: Hashimoto J. , Dong R. , Kudo T. , Honda M. , McClure M. K. , Zhu Z. , Muto T. , Wisniewski J. , Abe L. , Brandner W. , Brandt T. , Carson J. , Egner S. , Feldt M. , Fukagawa M. , Goto M. , Grady C. A. , Guyon O. , Hayano Y. , Hayashi M. , Hayashi S. , Henning T. , Hodapp K. , Ishii M. , Iye M. , Janson M. , Kandori R. , Knapp G. , Kusakabe N. , Kuzuhara M. , Kwon J. , Matsuo T. , Mayama S. , McElwain M. W. , Miyama S. , Morino J.-I. , Moro-Martin A. , Nishimura T. , Pyo T.-S. , Serabyn G. , Suenaga T. , Suto H. , Suzuki R. , Takahashi Y. , Takami M. , Takato N. , Terada H. , Thalmann C. , Tomono D. , Turner E. L. , Watanabe M. , Yamada T. , Takami H. , Usuda T. , Tamura M.
Published: September 2012

We present high-resolution H-band polarized intensity (FWHM = 0.″1: 14 AU) and L′-band imaging data (FWHM = 0.″11: 15 AU) of the circumstellar disk around the weak-lined T Tauri star PDS 70 in Centaurus at a radial distance of 28 AU (0.″2) up to 210 AU (1.″5). In both images, a giant inner gap is clearly resolved for the first time, and the radius of the gap is ∼70 AU. Our data show that the geometric center of the disk shifts by ∼6 AU toward the minor axis. We confirm that the brown dwarf companion candidate to the north of PDS 70 is a background star based on its proper motion. As a result of spectral energy distribution fitting by Monte Carlo radiative transfer modeling, we infer the existence of an optically thick inner disk at a few AU. Combining our observations and modeling, we classify the disk of PDS 70 as a pre-transitional disk. Furthermore, based on the analysis of L′-band imaging data, we put an upper limit of ∼30 to ∼50 M
J on the mass of companions within the gap. Taking into account the presence of the large and sharp gap, we suggest that the gap could be formed by dynamical interactions of sub-stellar companions or multiple unseen giant planets in the gap.
Groups acting on semimetric spaces and quasi-isometries of monoids
Authors: Gray Robert , Kambites Mark
Published: September 2012

We study groups acting by length-preserving transformations on spaces equipped with asymmetric, partially-defined distance functions. We introduce a natural notion of quasi-isometry for such spaces and exhibit an extension of the Švarc-Milnor lemma to this setting. Among the most natural examples of these spaces are finitely generated monoids and semigroups and their Cayley and Schützenberger graphs. We apply our results to show that a number of important properties of monoids are quasi-isometry invariants.
The dynamics of food chains under climate change and nutrient enrichment
Authors: Binzer Amrei , Guill Christian , Brose Ulrich , Rall Björn C.
Published: September 2012

Warming has profound effects on biological rates such as metabolism, growth, feeding and death of organisms, eventually affecting their ability to survive. Using a nonlinear bioenergetic population-dynamic model that accounts for temperature and body-mass dependencies of biological rates, we analysed the individual and interactive effects of increasing temperature and nutrient enrichment on the dynamics of a three-species food chain. At low temperatures, warming counteracts the destabilizing effects of enrichment by both bottom-up (via the carrying capacity) and top-down (via biological rates) mechanisms. Together with increasing consumer body masses, warming increases the system tolerance to fertilization. Simultaneously, warming increases the risk of starvation for large species in low-fertility systems. This effect can be counteracted by increased fertilization. In combination, therefore, two main drivers of global change and biodiversity loss can have positive and negative effects on food chain stability. Our model incorporates the most recent empirical data and may thus be used as the basis for more complex forecasting models incorporating food-web structure.