bluuebunny/crossref_metadata_2025 huggingface dataset:
Suppression and reversal of drop formation on horizontal cylinders due to surfactant convection
Authors: Weidner D. E.
Published: August 2013

When a thin liquid film is applied to the surface of a horizontal cylinder, gravity will cause a drainage of liquid from the top and sides of the cylinder towards the cylinder bottom. If surfactant is present on the surface of the film, this will cause a convection of surfactant resulting in a higher concentration of surfactant on the cylinder bottom compared to the top and sides of the cylinder. The result is a surface tension gradient, which is equivalent to a surface shear stress, and acts to oppose the drainage of the coating layer due to gravity. For sufficiently small cylinders, this cannot only slow the drainage but reverse the flow, causing a net flux of liquid upward from the bottom of the cylinder towards the top of the cylinder. If this flux is sufficiently strong, a “collar” of liquid forms around the cylinder. In this paper, we develop a mathematical model, based on the lubrication approximations, of the gravitational, surface tension, and surface tension gradient forces, and their effects on the evolution of a thin liquid film coating a horizontal circular cylinder. Using finite differences and an alternating direction implicit technique, numerical simulations show that even for comparatively weak surfactants, surface tension gradient effects greatly affect the flow history and must be included to accurately model the evolution of the film. They cannot only slow the drainage of liquid towards a pendant drop on the bottom of the cylinder, but reverse the flux, resulting in a thicker coating on the top of the cylinder compared to the surfactant-free case. Results from the simulation are presented over a wide range of the dimensionless parameters which characterize the problem.
Streamwise development of the wind turbine boundary layer over a model wind turbine array
Authors: Newman Jensen , Lebron Jose , Meneveau Charles , Castillo Luciano
Published: August 2013

The streamwise development of turbulence statistics and mean kinetic energy in a model wind farm consisting of 3 × 5 wind turbines is studied experimentally in a wind tunnel. The analysis uses planar Particle Image Velocimetry data obtained at the centerline plane of the wind farm, covering the inflow as well as four planes in between five downstream wind turbines. The data analysis is organized by dividing these measurement planes into three regions: the above-rotor, rotor-swept, and below-rotor regions. For each field, flow development is quantified using a properly defined relative difference norm based on an integration over each of the regions. Using this norm, it is found that the mean streamwise velocity approaches a fully developed state most rapidly, whereas the flow development is more gradual for the second-order statistics. The vertical entrainment flux of the mean kinetic energy by the Reynolds shear stress, ⟨U⟩⟨u′v′⟩, is observed to develop at a rate similar to that of the Reynolds shear stress rather than the mean streamwise velocity component. Its development is slowest in the layer nearest to the ground. Analysis of various terms in the mean kinetic energy equation shows that the wind turbine boundary layer has not yet reached fully developed conditions by the fifth turbine but that it is approaching such conditions. By comparing the vertical entrainment flux with the horizontal flux due to the mean flow, it is found that the former increases, whereas the latter decreases, as function of downstream distance, but that the former is already an important contributor in the developing region.
Electrical transport phenomena prevailing in undoped nc-Si/a-SiNx:H thin films prepared by inductively coupled plasma chemical vapor deposition
Authors: Das Debajyoti , Sain Basudeb
Published: August 2013

A comprehensive analysis on the electrical transport phenomena prevailing in undoped nc-Si/a-SiNx:H thin films prepared by inductively coupled plasma chemical vapor deposition and its correlation with the specific inhomogeneous structure, consisting of a mixture of different phases involving charge transfer by tunneling and thermionic emission or a connected network of aggregates of such components, has been made for deeper understanding in order to facilitate and improve the device applicability of the material. The nc-Si/a-SiNx:H films exhibit a thermally activated electrical transport above room temperature. Multi-phonon hopping (MPH), following σ∝Ty, occurs below room temperature, involving higher number of acoustic phonons in less crystalline network at higher nitrogenation. In less nitrogenated network, the MPH conduction continues up to the lowest temperature because of less localization of charge carriers within larger size of the nanocrystallites. Mott variable range hopping (Mott-VRH), following ln(σ) ∝ T−¼, is in effect below a certain temperature for highly nitrogenated network. The nature of variations of Mott parameter, T*, hopping activation energy, Wh, optimum hopping distance, rh, and the estimated density of states at the Fermi level, N(EF), identify the increased degree of disorder in the film attributing enhanced amorphous concentration at higher nitrogenation. The transition from MPH to Mott-VRH occurring at higher temperature at relatively higher nitrogenation has been interpreted as the freezing out of the acoustic phonons associated with lower grain size with higher number density at comparatively higher temperature, considering the phonon wavelength approximately of the size of nanocrystallites. The present intrinsic nc-Si/a-SiNx:H material containing nanocrystallites of average size ∼12–2 nm and number density ∼1011–1012 cm−2 providing a significantly wide range of optical band gap, Eg ∼ 1.80–2.75 eV with associated very high electrical conductivity, σD ∼ 10−2–10−6 S cm−1 along with high carrier concentration, ne ∼ 1014–1011 cm−3 and electron mobility, μe ∼ 246–105 cm2 V−1 s−1, seems to be the superior, concerning issues related to usability in device fabrication, among typical wide optical gap silicon dielectric materials available in the literature, e.g., silicon carbide, silicon oxide, and amorphous silicon films with nc-Si inclusions; while being the only comprehensive report on nanocrystalline silicon nitride (nc-Si/a-SiNx:H) thin films, in particular.
A comparative study by the grand canonical Monte Carlo and molecular dynamics simulations on the squeezing behavior of nanometers confined liquid films
Authors: Leng Yongsheng , Xiang Yuan , Lei Yajie , Rao Qi
Published: August 2013

Grand canonical Monte Carlo (GCMC) and liquid-vapor molecular dynamics (LVMD) simulations are performed to investigate the squeezing and phase transition of a simple liquid argon film confined between two solid surfaces. Simulation results show that the LVMD simulation is capable of capturing the major thermodynamic equilibrium states of the confined film, as predicted by the GCMC simulations. Moreover, the LVMD simulations reveal the non-equilibrium squeeze out dynamics of the confined film. The study shows that the solvation force hysteresis, observed in many surface force experiments, is attributed to two major effects. The first is related to the unstable jumps during the laying transitions of the confined film, in which the gradient of force profile is larger than the driving spring constant. The second effect is related to the squeeze out dynamics of the confined film even though the first effect is absent. In general, these two dynamic processes are non-equilibrium in nature and involve significant energy dissipations, resulting in the force hysteresis.
Effective diffusivity in transient state
Authors: Tabor Zbisław , Nowak Paweł , Krzak Małgorzata , Warszyński Piotr
Published: August 2013

The effective diffusivity in a polymer matrix modified with inclusions is usually calculated based on Kalnin-Kotomin's model [J. R. Kalnin, E. A. Kotomin, and J. Maier, J. Phys. Chem. Solids 63, 449–456 (2002)]10.1016/S0022-3697(01)00159-7, which extends the well known Maxwell-Garnett formula. Kalnin-Kotomin's model correctly predicts effective diffusivity for stationary diffusion or for infinite media. In the present paper diffusion in composite media is studied for finite systems under transient conditions. The process of diffusion is modeled numerically and effective diffusion coefficient in the transient state is estimated, which, under certain conditions, is different from the predictions of the Kalnin-Kotomin's model. An analytical model is proposed to explain deviations of the transient effective coefficient of diffusion from the stationary case.
Characteristics of carbon monoxide sensors made by polar and nonpolar zinc oxide nanowires gated AlGaN/GaN high electron mobility transistor
Authors: Hung S. C. , Woon W. Y. , Lan S. M. , Ren F. , Pearton S. J.
Published: August 2013

AlGaN/GaN high electron mobility transistors (HEMTs) with polar and nonpolar ZnO nanowires modified gate exhibit significant changes in channel conductance upon exposure to different concentration of carbon monoxide (CO) at room temperature. The ZnO nanowires, grown by chemical vapor deposition, with perfect crystal quality will attach CO molecules and release electrons, which will lead to a change of surface charge in the gate region of the HEMTs, inducing a higher positive charge on the AlGaN surface, and increasing the piezo-induced charge density in the HEMTs channel. These electrons create an image positive charge on the gate region for the required neutrality, thus increasing the drain current of the HEMTs. The HEMTs source-drain current was highly dependent on the CO concentration. The limit of detection achieved was 400 ppm and 3200 ppm in the open cavity with continuous gas flow using a 50 × 50 μm2 gate sensing area for polar and nonpolar ZnO nanowire gated HEMTs sensor, respectively.
Strain sensing and far-infrared absorption in strained graphene quantum dots
Authors: Qi Fenghua , Jin Guojun
Published: August 2013

We investigate the uniaxial strain modulated electronic structure and optical absorption of a triangular zigzag graphene quantum dot within the tight-binding approach. According to the symmetry analysis, the electronic structure and optical absorption can be correctly characterized before and after the strain is applied. The redshift or blueshift of the absorption peaks can be observed in the optical spectrum by uniaxial tensile or compressive strain, indicating that the strained triangular zigzag graphene quantum dot can be used as a strain sensor. The influence of dot sizes on the sensor sensitivity is also considered. Furthermore, the robustness of such a function against a single vacancy defect is confirmed. On the other hand, by applying a gate voltage on the strained dot, the Fermi energy is shifted away from zero, obvious far-infrared absorption peaks can appear in the optical spectrum, which means it is possible to realize far-infrared photodetectors based on strained graphene quantum dots.
Vacancy reactions near the interface between electroplated Cu and barrier metal layers studied by monoenergetic positron beams
Authors: Uedono A. , Kirimura T. , Wilson C. J. , Croes K. , Demuynck S. , Tőkei Z. , Oshima N. , Suzuki R.
Published: August 2013

Positron annihilation was used to probe vacancy-type defects in electrodeposited Cu films with capping layers. For as-deposited Cu films, two different types of vacancy-type defects were found to coexist: vacancy aggregates (V2-V4) and larger vacancy clusters (∼V10). During the fabrication processes of the capping layers, these defects diffused towards the interface between the capping layers and Cu. On the sample with the capping layers consisting of TaN and SiCN, a vacancy-rich region about 40 nm wide was introduced below the TaN/Cu interface, which was attributed to the blocking of vacancies by the TaN layer, and resulted in their agglomeration. The SiCN layer started degrading at annealing temperatures above 270 °C. Above 570 °C, the size of open spaces and their concentration in the SiCN layer decreased, which can be attributed to the diffusion of Cu atoms into the SiCN layer. Positron annihilation was shown to have a high potential to detect vacancy-type defects and open spaces near the interface between barrier metals and electroplated Cu.
Mechanism of aluminium bio-mineralization in the apoferritin cavity
Authors: Chiarpotto M. , Ciasca G. , Vassalli M. , Rossi C. , Campi G. , Ricci A. , Bocca B. , Pino A. , Alimonti A. , De Sole P. , Papi M.
Published: August 2013

Many experimental evidences point out the correlation between the presence of aluminum-ferritin complex and neursopathological disorders. In these complexes, two different ranges of Aluminium (Al) atoms are usually found, i.e., just few atoms or several hundreds. Here, we investigated the in-vitro Al-apoferritin binding, with the aim to elucidate the mechanism behind the formation of Al-ferritin complexes in-vivo. To this purpose, we studied the mineralization of Al in its ionic and complexed form with citrate demonstrating that high Al levels found in clinical studies can be obtained only conveying Al by small physiological ligands.
Intensive terahertz emission from GaSe0.91S0.09 under collinear difference frequency generation
Authors: Huang Jingguo , Huang Zhiming , Tong Jingchao , Ouyang Cheng , Chu Junhao , Andreev Yury , Kokh Konstantin , Lanskii Grigory , Shaiduko Anna
Published: August 2013

An intensive, broad tunable monochromatic Terahertz (THz) emission is generated from S-doped (2 wt. %) GaSe (solid solution GaSe0.91S0.09) crystals by collinear difference frequency generation method. The generated THz signal of 3.8 ns covers the spectral range of 0.57–3.57 THz (84.0–528.0 μm), with a maximal THz output peak power of 21.8 W at 1.62 THz. The THz power conversion efficiency is of 45% higher than that of undoped GaSe, which is mainly contributed to the improved optical properties. The terahertz source is of great potential to be exploited for the out-of-door applications due to the increased crystal hardness.
Enhancement of efficiency of InGaN-based light emitting diodes through strain and piezoelectric field management
Authors: Pal J. , Migliorato M. A. , Li C.-K. , Wu Y.-R. , Crutchley B. G. , Marko I. P. , Sweeney S. J.
Published: August 2013

We report calculations of the strain dependence of the piezoelectric field within InGaN multi-quantum wells light emitting diodes. Such fields are well known to be a strong limiting factor of the device performance. By taking into account the nonlinear piezoelectric coefficients, which in particular cases predict opposite trends compared to the commonly used linear coefficients, a significant improvement of the spontaneous emission rate can be achieved as a result of a reduction of the internal field. We propose that such reduction of the field can be obtained by including a metamorphic InGaN layer below the multiple quantum well active region.
Nanoscale organization by elastic interactions between H and He platelets in Si
Authors: Reboh S. , Barbot J. F. , Vallet M. , Beaufort M. F. , Rieutord F. , Mazen F. , Cherkashin N. , Fichtner P. F. P. , Grilhé J.
Published: August 2013

We used ion implantation of H and He in Si and thermal treatments to produce two systems allowing to study the effects of global and local mechanical stress fields on the formation energy of H-precipitates called H-platelets. In the first part of the work, the depth-distribution of different crystallographic orientations of the precipitates formed along the implanted layer was characterized by transmission electron microscopy. The global strain in the region was measured by X-ray diffraction, and the depth distribution of strain was reconstructed using a dynamical-theory-based code. Elasticity theory was used to develop a model based on mechanical interactions, explaining the preferential presence of (001)-oriented precipitates in the more stressed region of the implanted layer. In a second part, local sources of stress of nanometer size and cylindrical symmetry were introduced in a deeper region of the matrix, before the nucleation of H-platelets. The local stresses were embodied by (001) He-plate precipitates. Upon annealing, a specific arrangement of crystallographic variants of {111}-oriented H-platelets in a four-fold configuration was observed. To explain these experimental observations, and to calculate the variations of the formation energy of the precipitates under the presence of local stress tensors components, analytical and numerical (finite element method) approaches were used to develop 2D and 3D models based on elasticity theory. The concepts and modeling strategy developed here paves the way for determining the required conditions to create controlled architecture of precipitates at the nanoscale using local stress engineering.
Coherent structures and turbulent spectrum in solar wind plasmas
Authors: Sharma R. P. , Yadav N. , Kumari Anju
Published: August 2013

The present paper investigates the localization of a uniform plane kinetic Alfvén wave (KAW) due to the coupling with the density/magnetic field fluctuations associated with a magnetosonic wave propagating in the transverse direction, i.e., perpendicular to the background magnetic field. To gain the physical insight into this evolution, a simplified analytical model based on the Mathieu equation has also been studied. Numerical method has also been used to analyse the evolution of KAW. The magnetic fluctuation spectrum follows Kolmogorovian scaling above the proton gyroradius scalelength, which is regarded as the inertial range. Below this scale, a steepened spectrum has been obtained in the dispersive range with power law index ∼−2.5, which continues up to the dissipation range. Our results reveal that the proposed mechanism may be an interesting physical mechanism for transferring the energy from larger lengthscales to smaller lengthscales in the solar wind plasmas. Relevance of the present study with Cluster spacecraft observations has also been discussed.
Microwave breakdown for the TE10 mode in a rectangular waveguide
Authors: Malik Hitendra K. , Aria Anil K.
Published: August 2013

Microwave breakdown is studied for the lowest order TE10 mode in a rectangular waveguide with the help of direct variational approach via the continuity equation along with the use of ionisation and attachment frequency. We investigate the role of the ionisation, attachment of electron with neutral gas or air molecules and the diffusion on microwave breakdown threshold in the waveguide filled with air or Ar Gas. We examine the effect of different gases and microwave parameters on the diffusion length and the breakdown threshold of electric field of continuous microwave and pulsed microwave. We also employ numerical approach for obtaining the results and compare them with the ones of variational approach.
Implications of weak-link behavior on the performance of Mo/Au bilayer transition-edge sensors
Authors: Smith Stephen J. , Adams Joseph S. , Bailey Catherine N. , Bandler Simon R. , Busch Sarah E. , Chervenak James A. , Eckart Megan E. , Finkbeiner Fred M. , Kilbourne Caroline A. , Kelley Richard L. , Lee Sang-Jun , Porst Jan-Patrick , Porter Frederick S. , Sadleir John E.
Published: August 2013

Understanding the physical properties of the superconducting-to-normal transition is fundamental for optimizing the design and performance of transition-edge sensors (TESs). Recent critical current IC measurements of square Mo/Au bilayer structures show that they act as weak superconducting links, exhibiting oscillatory, Fraunhofer-like behavior with applied magnetic field. In this paper, we investigate the implications of this behavior for TES x-ray detectors operated in the resistive transition. These devices include normal metal features used for absorber attachment and suppression of detector noise. We present extensive measurements of IC as a function of temperature T and field B, which show a complex temperature and current evolution when compared with the behavior expected from a simple geometry. We introduce a resistively shunted junction model for describing the TES resistive transition as a function of current I, temperature T, and magnetic field B. From this model, we calculate the R(T,I,B) transition and the logarithmic resistance sensitivity with respect to T and I (α and β, respectively), as a function of applied magnetic field and operating point within the resistive transition. Different examples are presented to illustrate the role of critical current on the transition parameters, and results are qualitatively compared with measurements. Results show that the important device parameters α and β exhibit oscillatory behavior with applied magnetic field due to the modulation of the critical current. This in turn affects the signal responsivity and noise, and the predicted energy resolution. These results show the significance of the critical current in determining the performance of TESs and how externally applied and self-induced magnetic fields can affect the transition and, thus, hold promise for future optimization.
Three dimensional microfluidics with embedded microball lenses for parallel and high throughput multicolor fluorescence detection
Authors: Fan Y. J. , Wu Y. C. , Chen Y. , Kung Y. C. , Wu T. H. , Huang K. W. , Sheen H. J. , Chiou P. Y.
Published: August 2013

We report a 3D microfluidic device with 32 detection channels and 64 sheath flow channels and embedded microball lens array for high throughput multicolor fluorescence detection. A throughput of 358 400 cells/s has been accomplished. This device is realized by utilizing solid immersion micro ball lens arrays for high sensitivity and parallel fluorescence detection. High refractive index micro ball lenses (n = 2.1) are embedded underneath PDMS channels close to cell detection zones in channels. This design permits patterning high N.A. micro ball lenses in a compact fashion for parallel fluorescence detection on a small footprint device. This device also utilizes 3D microfluidic fabrication to address fluid routing issues in two-dimensional parallel sheath focusing and allows simultaneous pumping of 32 sample channels and 64 sheath flow channels with only two inlets.
Correlation between I (current)-V (voltage) characteristics and thermally stimulated depolarization current of Mn-doped BaTiO3 multilayer ceramic capacitor
Authors: Yoon Seok-Hyun , Kim Sang-Hyuk , Kim Doo-Young
Published: August 2013

I (Current)-V (voltage) characteristics of Mn-doped BaTiO3 multilayer ceramic capacitor were investigated. The increase of Mn concentration reduced the slope of current increase with increasing dc field and enhanced the dc field to the abrupt increase of current and thereby breakdown. Ohmic, Schottky, and Poole-Frenkel type conduction was successively observed with the increase of dc field in all specimens. The region of Child's law did not appear before breakdown, which suggests space charge limited (SCL) conduction with field enhanced trap barrier lowering. A peak of thermally stimulated depolarization current (TSDC) beyond 300 °C associated with trapped space charges appeared, which increased by the increase of Mn concentration. In addition, the peak intensity increased to a maximum value and then decreased again with increasing polarization dc field in TSDC measurement. Its activation energies were around 1.9 eV for all specimens, which is very close to the energy level for the ionization of Mn3+/Mn2+. These results experimentally demonstrate the role of the variable valence acceptor Mn as trapping center for injected charges, and the occurrence of field enhanced trap charge release, and therefore, the conduction mechanism can be described by the SCL model incorporating the Poole-Frenkel effect.
Kinetics of solid phase crystallization of amorphous silicon analyzed by Raman spectroscopy
Authors: Hong Won-Eui , Ro Jae-Sang
Published: August 2013

Solid phase crystallization (SPC) of amorphous silicon films grown by low pressure chemical vapor deposition was conducted using a tube furnace in nitrogen ambient at temperatures ranging from 560 °C to 1000 °C. The transformed crystalline fraction shows typical sigmoidal curves as a function of annealing time using Raman analysis adopted in this work. Arrhenius plot of the measured incubation time does not fit to the straight line since SPC kinetics has strong temperature dependence and since the heating rate is slow when using a conventional heating method. The grain size decreases as the annealing temperature increases. It, however, is not sensitive to the annealing temperature beyond 800 °C, since SPC kinetics is complete during the period of heating-up according to Raman spectroscopy. It was observed that doping of impurity atoms affect the crystallization kinetics.
Evaporation of a sessile liquid droplet from the shear or flexural surfaces of a quartz tuning fork
Authors: Jung Namchul , Yun Minhyuk , Jeon Sangmin
Published: August 2013

A piezoelectric quartz tuning fork (QTF) has been used to investigate the evaporation of a sessile water droplet with nanogram sensitivity. A water droplet is placed on one facet of a QTF tine and the changes in the resonance frequency and dissipation factor, which are related to the changes in mass and viscous damping, respectively, are measured in situ during the evaporation. Depending on the facet of the QTF tine on which the water droplet is placed, the changes in the frequency and dissipation factor arise in different vibration modes: the flexural or shear modes. The shear mode measurement is affected by the penetration depth, so changes in the frequency and dissipation factor are observed only when the water droplet is sufficiently thin, whereas the changes in the flexural mode measurements are observed during the entire evaporation process. When a droplet of polystyrene nanoparticle suspension is evaporated from the flexural surface, the concentration of the nanoparticle suspension can be determined from the difference in mass between the initial droplet and the dry nanoparticles. In contrast, changes in the physical properties of the suspension are obtained in situ from the evaporation from the shear surface. These results demonstrate that QTFs are useful tools for the investigation of the evaporation of suspensions from solid surfaces.
Solvothermal preparation of potassium niobate/barium titanate nanocomplex ceramics with three dimensional network-configuration of structure-gradient region and their dielectric properties
Authors: Ueno S. , Kawashima H. , Nakashima K. , Kumada N. , Magome E. , Moriyoshi C. , Kuroiwa Y. , Fujikawa Y. , Tanaka D. , Furukawa M. , Wada S.
Published: August 2013

To improve dielectric properties of barium titanate (BaTiO3, BT)-based ceramics, the BT/potassium niobate (KNbO3, KN) nanocomplex ceramics were designed to expect the formation of a three dimensional network-configuration of a structure-gradient region (SGR), where the polar vector can easily rotate. The KN epitaxial nanolayers were formed on BT compacts with a necking structure by a solvothermal method and the maximal dielectric constant of 1450 and the relatively large apparent piezoelectric constant d33* of 318 pm/V were recorded for the KN/BT nanocomplex ceramics. The experimental facts suggest that the configuration of the SGR, in addition to the relative density, is one of the important factors to enhance the dielectric properties of the KN/BT nanocomplex ceramics.
Two-dimensional model of orificed micro-hollow cathode discharge for space application
Authors: Levko D. , Krasik Ya. E. , Vekselman V. , Haber I.
Published: August 2013

In this paper, we describe results of self-consistent two-dimensional (x-z) particle-in-cell simulations, with a Monte Carlo collision model, of an orificed micro-hollow cathode operating in a planar diode geometry. The model includes thermionic electron emission with Schottky effect, secondary electron emission due to cathode bombardment by the plasma ions, several different collision processes, and a non-uniform xenon background gas density in the cathode-anode gap. Simulated results showing behavior of the plasma density, potential distribution, and energy flux towards the hollow cathode and orifice walls, are discussed. In addition, results of simulations showing the effect of different Xe gas pressures, orifice size, and cathode voltage, on operation of the micro-hollow cathode are presented.
Possibility of enhancing the thermoelectric figure of merit of ZnO by sulfur incorporation
Authors: Gather F. , Kronenberger A. , Hartung D. , Becker M. , Polity A. , Klar P. J. , Meyer B. K.
Published: August 2013

The thermal conductivity κ of ZnO can be significantly suppressed by alloying with a few percent of S offering the possibility of enhancing the thermoelectric figure of merit ZT. κ of radio-frequency sputtered wurtzite ZnO1–xSx thin-films was measured in the entire composition range x employing the 3ω-method. Both, incorporation of low amounts of S in ZnO and of O in ZnS reduce κ of the ZnO1–xSx-samples compared to the two binary compounds. The origin of the reduction of κ in the alloys is the formation of localized vibrational modes of S in ZnO and O in ZnS.
High-temperature solar cell for concentrated solar-power hybrid systems
Authors: Yang Yang , Yang Wenzheng , Tang Weidong , Sun Chuandong
Published: August 2013

A high-temperature solar cell is proposed that harvests solar energy at elevated temperatures. Carrier separation is achieved by selective contacts that preferentially extract electrons or holes. The theoretical conversion efficiency of the proposed device is 38.6% at 600 K and an incident solar radiation concentration of 1000. The waste heat of this cell could be used by a secondary thermal converter boosting the total efficiency of the hybrid system above 55%.
Defect induced optical bandgap narrowing in undoped SnO2 nanocrystals
Authors: Kamble Vinayak B. , Umarji Arun M.
Published: August 2013

Unusual optical bandgap narrowing is observed in undoped SnO2 nanoparticles synthesized by the solution combustion method. The estimated crystallite size is nearly 7 nm. Though the quantum confinement effect predicts a larger optical bandgap for materials with small crystallite size than the bulk, the optical bandgap in the as synthesized materials is found to be 2.9 eV compared to the reported value of 3.6 eV for bulk SnO2 particles. The yellow-green photoluminescence emissions and the observed narrowing of the bandgap can be attributed to the deep donor levels of oxygen vacancies, owing to the high exothermicity of the combustion reaction and the faster cooling rates involved in the process.
The demonstration of nonlinear analytic model for the strain field induced by thermal copper filled TSVs (through silicon via)
Authors: Liao M. H. , Yu M.-Y. , Liu G.-H. , Chen C.-H. , Hsu T.-K.
Published: August 2013

The thermo-elastic strain is induced by through silicon vias (TSV) due to the difference of thermal expansion coefficients between the copper (∼18 ppm/ °C) and silicon (∼2.8 ppm/ °C) when the structure is exposed to a thermal ramp budget in the three dimensional integrated circuit (3DIC) process. These thermal expansion stresses are high enough to introduce the delamination on the interfaces between the copper, silicon, and isolated dielectric. A compact analytic model for the strain field induced by different layouts of thermal copper filled TSVs with the linear superposition principle is found to have large errors due to the strong stress interaction between TSVs. In this work, a nonlinear stress analytic model with different TSV layouts is demonstrated by the finite element method and the analysis of the Mohr's circle. The characteristics of stress are also measured by the atomic force microscope-raman technique with nanometer level space resolution. The change of the electron mobility with the consideration of this nonlinear stress model for the strong interactions between TSVs is ∼2–6% smaller in comparison with those from the consideration of the linear stress superposition principle only.
Walking Accessibility to Public Transport: An Analysis Based on Microdata and GIS
Authors: García-Palomares Juan Carlos , Gutiérrez Javier , Cardozo Osvaldo Daniel
Published: August 2013

In this paper we analyse the role of walking accessibility to transit facilities. Microdata and GIS tools have been used to calculate distances walked by different population groups in accessing Metro stations. Distances walked by the population were used to determine the threshold distances of the station service areas and calculate the population covered by the Metro network. With respect to Metro ridership, different distance-decay functions were adjusted and the sensitivity of the population groups to the distance was measured. Two indicators were proposed, based on the distance-decay functions, to measure access quality and potential demand. The Madrid Metro network was used as the study area. Results show that young people and adults, men, immigrants, and public transit captives are willing to walk longer distances and are less sensitive to the effect of distance. When walking distances have been used in order to fix the limit of catchment areas, the amount of the population covered is lower than when a standard threshold (0.5 miles) is used, but overestimations affect each age group in a different way. The access quality indicator shows that the population group in the worst situation is children and that stations in the centre of the network have higher access quality values. However, the synthetic accessibility indicator shows that potential demand is lower for the most central and most peripheral stations than for the stations located in the intermediate areas. It has been proved that both indicators are sensitive to changes in the spatial distribution of population groups within the catchment areas. These results demonstrate some of the advantages of the proposed methodology and argue in favour of its use in public transport planning.
The critical role of nurses to the successful implementation of the National Safety and Quality Health Service Standards
Authors: Twigg Diane E. , Duffield Christine , Evans Gemma
Published: August 2013

The National Safety and Quality Health Service Standards requires health service compliance by 2013 and covers several areas including governance arrangements, partnerships with consumers and eight key clinical processes. Nurses in Australia comprise 62% of the hospital workforce, are the largest component and hence play a critical role in meeting these standards and improving the quality of patient care. Several of the standards are influenced by nursing interventions, which incorporate any direct-care treatment that the nurse performs for a patient that may be nurse or physician initiated. The ability for nurses to undertake these interventions is influenced by the hours of care available, the skill mix of the nursing workforce and the environment in which they practice. Taking into consideration the predicted nursing shortages, the challenge to successfully implement the National Safety and Quality Health Service Standards will be great. This paper examines the role of nursing in the delivery of the National Standards, analyses the evidence with regard to nursing-sensitive outcomes and discusses the implications for health service decision makers and policy.

What is known about the topic?
The National Safety and Quality Health Service Standards have been endorsed for implementation by the Australian Health Ministers. Compliance with the National Safety and Quality Health Service Standards is required by Health Services in 2013. Nurses play a critical role in providing high-quality patient care and meeting accreditation standards. A decline in nursing standards is associated with inadequate staffing levels and skill mix and a lack of effective leadership and results in an increase in patient mortality.

What does this paper add?
The role of nurses in achieving compliance with the standards is discussed. We demonstrate that the capacity for nurses to undertake interventions is influenced by prevailing workforce characteristics. Significant nursing shortages have been identified as possible challenges to successfully implementing the National Safety and Quality Health Service Standards.

What are the implications for practitioners?
Practitioners need to review nursing hours of care, skill mix and the practice environment as part of the actions required to achieve the National Quality and Safety Standards. The Australian Commission on Safety and Quality in Health Care has the opportunity to take the lead by including such indicators in the measurement of hospital performance.
Victorian junior doctors’ perception of their competency and training needs in healthcare management
Authors: Schoenmaker Suzanne G. , Berkenbosch Lizanne , Ahern Susannah , Busari Jamiu O.
Published: August 2013

Introduction. Australian medical speciality colleges have adapted and integrated the CanMEDS Physician Competency Framework into their training programs. The role as manager is one of the competencies and is presently thought to receive little attention during training. The objective of our study was to investigate the perceptions of Australian junior doctors regarding their management skills and their perceived need for management education. Methods. In November and December 2011, 1376 junior doctors from eight Victorian metropolitan health services were invited via email to participate in this study. Participating junior doctors received a questionnaire regarding their self- perceived management skills and knowledge and a medical management training needs assessment. Results. The response rate of one of the health centres was too low (6%) and therefore insufficient for credible conclusions to be drawn. Of the other health services, 194 (16%) out of 1213 junior doctors responded to the survey. Overall, the junior doctors rated their perceived competency on a 1–5 Likert scale as moderate (mean 3.45; s.d. 0.42). Of the 194 residents who responded, 71.3% (n = 139) reported a need for management training. Discussion. The junior doctors of Victoria, Australia perceived their knowledge on medical management as moderate. The results of this study showed that there is a perceived need among junior doctors for more management training. This need seems to confirm that management skills are thought to be valuable in medical practice. Our study also suggests that before the development of specific interventions, there is a need for a gap analysis between the perceived and actual management skills desired in medical residents. The attention paid to the role ‘as manager’ should therefore be embedded in training of all junior doctors. What is known about the topic? The CanMEDS 2005 Framework describes the seven key competencies physicians should possess to meet the needs of patients and society, and was developed by The Royal College of Physicians and Surgeons of Canada. One of these competencies is the role as manager. Published studies have shown that medical residents have a need for education in healthcare management in basic and postgraduate medical training. What does this paper add? In this study we discovered that junior doctors in Victorian metropolitan health services have a moderate perception of their competencies as managers. Previous management experience influenced the perceived competence in a positive way. What are the implications for practitioners? We believe that it is necessary that junior doctors continue to build on existing opportunities to develop their management skills. In order to achieve this, awareness of the importance of management competencies and the possibilities to obtain management experience must be raised among junior doctors. Furthermore, they need to be given the opportunity to obtain experience.
Different responses in leaf pigments and leaf mass per area to altitude between evergreen and deciduous woody species
Authors: Li Yan , Yang Dongmei , Xiang Shuang , Li Guoyong
Published: August 2013

Leaf chlorophyll content is positively associated with photosynthetic capacity and nutrient status, but its functional ecology has seldom been examined thus far. In the present study, we measured leaf chlorophyll and carotenoid concentrations, determined chlorophyll a : chlorophyll b (Chl a : Chl b) and carotenoids : chlorophyll ratios and measured leaf mass per area (LMA) for 63 woody dicot species, including 24 evergreen species and 39 deciduous species, at two altitudes (1800–2400 and 2400–2800 m a.s.l.) of Gongga Mountain, south-west China. The aim of the present study was to determine whether evergreen and deciduous species differ in terms of leaf pigment concentrations and LMA in response to environmental differences associated with changes in elevation. In both life forms, the altitude effect was not significant for chlorophyll and carotenoid concentrations. However, the Chl a : Chl b ratio was significantly higher in evergreen species, whereas LMA was significantly higher in deciduous species, at the high versus low altitude. These observations suggest that evergreen and deciduous species may have different strategies to protect leaf pigments. Mass-based leaf pigment concentrations were lower in evergreen compared with deciduous species, especially at high altitude. LMA was higher in evergreen than deciduous species at both altitudes. Pigment concentrations were negatively correlated with LMA in both life forms at both altitudes. The slope of LMA vs mass-based leaf pigment concentrations was significantly more negative for deciduous than evergreen species, and at low versus high altitude for deciduous species. The findings suggest that deciduous species may invest less photosynthate in leaf pigments but more in inactive components in stressful environments than do evergreens. Thus, the same magnitude of variation in LMA may have different consequences on leaf carbon balance between evergreen and deciduous species, which helps explain why evergreen species are often more likely to occupy more stressful environments than deciduous species.
Solvolysis of 4-Halogeno-4-Alkyl-2,6-di-tert-butylcyclohexa-2,5-dienones Induced by Positive Halogen Donors as Electrophiles
Authors: Omura Kanji
Published: August 2013

Positive halogen donors such as N-iodosuccinimide (NIS) induce solvolysis of dienones 1, as model 4-halogenocyclohexa-2,5-dienones, in different hydroxylic solvents (ROH), yielding the 4-RO-cyclohexa-2,5-dienones (2). The rate of the solvolysis with NIS is highly dependent on the structure of ROH. The problem of such dependency is overcome by running the reaction in ROH diluted with MeCN, a polar aprotic solvent, in place of pure ROH; the rate of the reaction in the ROH-MeCN solvent mixture is almost independent of the structure (or the polarity) of ROH, and the reaction is completed faster or markedly faster than in neat ROH. The results suggest that the solvolysis rate is controlled by the polarity of the solvent system, although the hydrogen-bond acceptability of MeCN for dilution also accelerates the reaction. A mechanism for the solvolysis is proposed, involving electrophilic attack of a positive halogen donor at the halogen atom of 1, generating the 4-oxocyclohexa-2,5-dienyl cation intermediates (8) via the rate-limiting polar transition states.
Sexual behaviours and associated risks in Chinese young people: a meta-analysis
Authors: Yu Xiao-ming , Guo Shuai-jun , Sun Yu-ying
Published: August 2013

Background
The earlier and unprotected sexual behaviour of young Chinese, and the consequences of these actions, have become a health concern, posing a challenge to traditional Chinese concepts. The aim of the present study was to investigate changes in sexual behaviour and associated risks among adolescents and young people in mainland China over the past three decades. Methods: A meta-analysis was undertaken to comprehensively review the sexual behaviour of Chinese young people (aged from 10 to 24 years) over the past 30 years. Relevant data published from 1979 to 2009 in the Chinese literature database were identified and retrieved. Analysis was performed based on set criteria. Results: Seventy-five studies were identified that were published after 1990. Overall, the estimated prevalence of sexual intercourse among young people was 12.6%, with an average age at sexual debut of 19.4 years. The rate of condom use at sexual debut was 37.2%; 53.6% of young people reported not using a condom during the most recent act of sexual intercourse. The rates of unintentional pregnancy and abortion among the sexually active were 15.1% and 10.8%, respectively. Reviewing the data according to decades revealed that the number of young people engaging in sexual intercourse decreased from 14.3% in 1990–1999 to 11.8% in 2000–2009. However, these rates are higher than the prevalence of sexual activity reported before 1990, which, according to sporadic studies, did not exceeded 1%. Conclusions: There have been increases in sexual activity and high-risk sexual behaviour in Chinese young people in the decades since the adoption of the open door policy in China, particularly since the mid-1990s. High-risk sexual behaviours have contributed to certain adverse consequences in adolescents and young people, such as unwanted pregnancy and sexually transmissible infection. Thus, efficacious intervention strategies need to be developed and implemented.
Factors influencing detection probabilities of frogs in the monsoonal tropics of northern Australia: implications for the design of monitoring studies
Authors: Dostine P. L. , Reynolds S. J. , Griffiths A. D. , Gillespie G. R.
Published: August 2013

Context
Failure to acknowledge potential bias from imperfect detection of cryptic organisms such as frogs may compromise survey and monitoring programmes targeting these species.

Aims
The aims of the present study were to identify proximate factors influencing detection probabilities of a range of frog species in monsoonal northern Australia, and to estimate the number of repeat censuses required at a site to have confidence that non-detected species are absent.

Methods
Data on detection or non-detection of frog species based on calling individuals were recorded during 10 wet-season censuses of 29 survey sites in the Darwin region. Factors influencing detection probabilities were identified using occupancy models; model selection was based on the Akaike information criterion. Sampling effort for individual species was calculated using model predictions at different stages of the wet season.

Key results
The covariate water temperature featured in the best-supported models for 7 of the 14 frog species. Six of these species were more likely to be detected when water temperatures were below 30°C. Detection probabilities were also correlated with the number of days since the commencement of the wet season, time since last significant rainfall, air temperature and time after sunset. Required sampling effort for individual species varied throughout the wet season. For example, a minimum of two repeat censuses was required for detection of Litoria caerulea in the early wet season, but this number increased to 13 in the middle stage of the wet season.

Conclusions
Variability in environmental conditions throughout the wet season leads to variability in detection probabilities of frog species in northern Australia. Lower water temperatures, mediated by rainfall immediately before or during surveys, enhances detectability of a range of species. For most species, three repeat surveys under conditions resulting in a high detection probability are sufficient to determine presence at a site.

Implications
Survey and monitoring programmes for frogs in tropical northern Australia will benefit from the results of the present study by allowing targeting of conditions of high detection probability for individual species, and by incorporating sufficient repeat censuses to provide accurate assessment of the status of individual species at a site.