bluuebunny/crossref_metadata_2025 huggingface dataset:
High-energy x-ray backlighter spectrum measurements using calibrated image plates
Authors: Maddox B. R. , Park H. S. , Remington B. A. , Izumi N. , Chen S. , Chen C. , Kimminau G. , Ali Z. , Haugh M. J. , Ma Q.
Published: February 2011

The x-ray spectrum between 18 and 88 keV generated by a petawatt laser driven x-ray backlighter target was measured using a 12-channel differential filter pair spectrometer. The spectrometer consists of a series of filter pairs on a Ta mask coupled with an x-ray sensitive image plate. A calibration of Fuji™ MS and SR image plates was conducted using a tungsten anode x-ray source and the resulting calibration applied to the design of the Ross pair spectrometer. Additionally, the fade rate and resolution of the image plate system were measured for quantitative radiographic applications. The conversion efficiency of laser energy into silver Kα x rays from a petawatt laser target was measured using the differential filter pair spectrometer and compared to measurements using a single photon counting charge coupled device.
Free energy of conformational transition paths in biomolecules: The string method and its application to myosin VI
Authors: Ovchinnikov Victor , Karplus Martin , Vanden-Eijnden Eric
Published: February 2011

A set of techniques developed under the umbrella of the string method is used in combination with all-atom molecular dynamics simulations to analyze the conformation change between the prepowerstroke (PPS) and rigor (R) structures of the converter domain of myosin VI. The challenges specific to the application of these techniques to such a large and complex biomolecule are addressed in detail. These challenges include (i) identifying a proper set of collective variables to apply the string method, (ii) finding a suitable initial string, (iii) obtaining converged profiles of the free energy along the transition path, (iv) validating and interpreting the free energy profiles, and (v) computing the mean first passage time of the transition. A detailed description of the PPS↔R transition in the converter domain of myosin VI is obtained, including the transition path, the free energy along the path, and the rates of interconversion. The methodology developed here is expected to be useful more generally in studies of conformational transitions in complex biomolecules.
Ferromagnetic Si/Mn27Si47 core/shell nanowire arrays
Authors: Liu Hailong , She Guangwei , Ling Shiting , Mu Lixuan , Shi Wensheng
Published: February 2011

Arrays of Si/Mn27Si47 core/shell nanowire (NW) are synthesized by an in situ reaction between Si NW arrays and MnCl2. Results from XRD and transition electron microscopy (TEM) indicated that the shells have single-crystalline tetragonal Mn27Si47 structure with the axial direction perpendicular to (204) face. The thickness of the Mn27Si47 shell can be controlled by adjusting the growth conditions. The Si/Mn27Si47 NW arrays exhibited enhanced ferromagnetism compared with the bulk higher manganese silicides (HMS). The Curie temperature of the Si/Mn27Si47 core/shell NW arrays is about 150 K, which is much higher than that of the bulk HMS. Due to the excellent compatibility of Si/Mn27Si47 with Si-based nanowire devices, these core/shell structures should have wide potential applications in the Si-based self-assembly nanowire devices.
Characterization of negative refraction with multilayered mushroom-type metamaterials at microwaves
Authors: Kaipa Chandra S. R. , Yakovlev Alexander B. , Silveirinha Mário G.
Published: February 2011

In this paper, it is shown that bulk metamaterials formed by multilayered mushroom-type structures enable broadband negative refraction. The metamaterial configurations are modeled using homogenization methods developed for a uniaxial wire medium loaded with periodic metallic elements (for example, patch arrays). It is shown that the phase of the transmission coefficient decreases with the increasing incidence angle, resulting in the negative spatial shift of the transmitted wave. The homogenization model results are obtained with the uniform plane-wave incidence, and the full-wave results are generated with a Gaussian beam excitation, showing a strong negative refraction in a significant frequency band. Having in mind a possible experimental verification of our findings, we investigate the effect of introducing air gaps in between the metamaterial layers, showing that even in such simple configuration the negative refraction phenomenon is quite robust.
A three dimensional rate equation model for the dynamical sensing effect of magnetostrictive Galfenol
Authors: Weetman Philip , Akhras George
Published: February 2011

A three-dimensional computational model for the dynamical sensing response of Galfenol magnetostrictive devices based on the rate equations is developed. The sensing model calculates the fraction of magnetic moments oriented along each of the energetically preferred directions of the crystal as a function of time, which can then be used to determine the time evolution of the total magnetization. Results from this 3D sensing model are compared to quasistatic loading experiments for the validation and extraction of phenomenological parameters. Using these extracted parameters, calculations are made for the dynamical sensing response. Thermodynamic effects are also incorporated into the model by a Boltzmann distribution of the magnetic moments in the crystal. Good quantitative agreement between the model and experiment at low magnetic bias fields and qualitative agreement at higher magnetic bias fields is obtained.
Field electron emission characteristic of graphene
Authors: Wang Weiliang , Qin Xizhou , Xu Ningsheng , Li Zhibing
Published: February 2011

The field electron emission current from graphene is calculated analytically on a semiclassical model. The unique electronic energy band structure of graphene and the field penetration in the edge from which electrons emit have been taken into account. The relation between the effective vacuum barrier height and the applied field is obtained. The calculated slope of the Fowler-Nordheim plot of the current-field characteristic is in agreement with existing experiments.
Thermal transport around tears in graphene
Authors: Loh G. C. , Teo E. H. T. , Tay B. K.
Published: February 2011

Tears in any material act as barriers to phonon transport. In this study, molecular dynamics simulations are employed to investigate thermal transport around tears in graphene. Specifically, thermal boundary conductance across different tear orientations and lengths is computed. Analysis of vibrational density of states suggests that long-wavelength acoustic phonons within the spectrum range 0–700 cm−1 are vital to thermal transport across the tears. Different phonon scattering phenomena are observed for both tear orientations. It is proposed that the dissimilitude of the scattering processes encountered by phonons carrying energy around the tears to the opposite end explains why thermal transport is generally more efficient for longitudinal tears in our simulations.
Reduction of lattice thermal conductivity from planar faults in the layered Zintl compound SrZnSb2
Authors: Prytz Ø. , Flage-Larsen E. , Toberer E. S. , Snyder G. J. , Taftø J.
Published: February 2011

The layered Zintl compound SrZnSb2 is investigated using transmission electron microscopy (TEM) to understand the low lattice thermal conductivity. The material displays out-of-phase boundaries with a spacing from 100 down to 2 nm. Density functional theory calculations confirm that the TEM-derived defect structure is energetically reasonable. The impact of these defects on phonon scattering is analyzed within the Debye–Callaway model, which reveals a significant reduction in the acoustic phonon mean free path. This enhancement in phonon scattering leads to an ∼30% reduction in lattice thermal conductivity at 300 K.
Combined ultrasonic elastic wave velocity and microtomography measurements at high pressures
Authors: Kono Yoshio , Yamada Akihiro , Wang Yanbin , Yu Tony , Inoue Toru
Published: February 2011

Combined ultrasonic and microtomographic measurements were conducted for simultaneous determination of elastic property and density of noncrystalline materials at high pressures. A Paris–Edinburgh anvil cell was placed in a rotation apparatus, which enabled us to take a series of x-ray radiography images under pressure over a 180° angle range and construct accurately the three-dimensional sample volume using microtomography. In addition, ultrasonic elastic wave velocity measurements were carried out simultaneously using the pulse reflection method with a 10° Y-cut LiNbO3 transducer attached to the end of the lower anvil. Combined ultrasonic and microtomographic measurements were carried out for SiO2 glass up to 2.6 GPa and room temperature. A decrease in elastic wave velocities of the SiO2 glass was observed with increasing pressure, in agreement with previous studies. The simultaneous measurements on elastic wave velocities and density allowed us to derive bulk (Ks) and shear (G) moduli as a function of pressure. Ks and G of the SiO2 glass also decreased with increasing pressure. The negative pressure dependence of Ks is stronger than that of G, and as a result the value of Ks became similar to G at 2.0–2.6 GPa. There is no reason why we cannot apply this new technique to high temperatures as well. Hence the results demonstrate that the combined ultrasonic and microtomography technique is a powerful tool to derive advanced (accurate) P–V–Ks–G–(T) equations of state for noncrystalline materials.
A small-angle scattering chamber for x-ray photon correlation spectroscopy at low temperatures
Authors: Steinmann Ricardo , Chushkin Yuriy , Caronna Chiara , Chavanne Joel , Madsen Anders
Published: February 2011

A low temperature sample environment for x-ray photon correlation spectroscopy measurements in small-angle scattering geometry is presented. The chamber has been designed to allow investigations of dynamical phenomena in supercooled liquids and the typical working temperature range is 110–330 K with a thermal stability ΔT/T down to 10−4. A variable external magnetic field up to 0.12 T can be applied, which is of interest in studies of, e.g., ferrofluids and liquid crystalline materials. Here, technical details about the sample environment are given together with examples of recent applications.
Three-dimensional imaging of undercut and sidewall structures by atomic force microscopy
Authors: Cho Sang-Joon , Ahn Byung-Woon , Kim Joonhui , Lee Jung-Min , Hua Yueming , Yoo Young K. , Park Sang-il
Published: February 2011

Sidewall surface roughness is an important parameter in electronic device manufacture. At present, no high resolution technique exists to quantitatively characterize this property for undercut structures created by semiconductor processing techniques. We developed a three-dimensional atomic force microscope (3D-AFM) to measure the surface roughness of undercut sidewalls with nanometer precision. Decoupled from the positional scanner, the 3D-AFM probe had a variable tilt up to 40° off the normal. Nonorthogonal scans resolved the sidewall surface roughness, base width, and acute critical angle for undercut structures, including a metal overhang and the transmission line of a photonic device. Compatible with standard cantilevers, the 3D-AFM demonstrates great potential for characterizing the sidewalls of soft materials such as photoresist.
Note: Accuracy of velocity correction for impact of a laser-accelerated miniature flyer with lithium fluoride shock-compressed along the [100] axis
Authors: Wakabayashi Kunihiko , Matsumura Tomoharu , Nakayama Yoshio , Koshi Mitsuo
Published: February 2011

We performed miniature flyer impact experiments to investigate the relationship between the apparent (ua) and actual (uA) particle velocities measured by a velocity interferometer in single-crystal lithium fluoride (LiF) that was shock-compressed along the [100] axis. The miniature flyer was accelerated to velocities in the range 652.5–1937.6 m/s by a tabletop pulsed laser. An empirical relationship of ua = (1.2749 ± 0.0102)uA was obtained. The obtained relationship agreed well with the results of a previous study within the experimental errors and its uncertainty was less than ±1%. This result indicates that the present experimental technique is effective for measuring the relationship between ua and uA of shocked transparent materials with a comparable accuracy to conventional methods.
Global smooth solutions for 1D thermally radiative magnetohydrodynamics
Authors: Qin Yuming , Hu Guili
Published: February 2011

This paper is concerned with the global existence of smooth solutions to equations describing one-dimensional motion of a self-gravitating, radiative of magnetohydrodynamics gas. We have proved that for any arbitrary large smooth initial data, the problem under consideration admits a unique globally smooth (classical) solution. Our results have improved the results given by Zhang and Xie [J. Differ. Equations 52, 1853–1882 (2008)].
Adhesive-free colloidal probes for nanoscale force measurements: Production and characterization
Authors: Indrieri M. , Podestà A. , Bongiorno G. , Marchesi D. , Milani P.
Published: February 2011

We describe novel approaches for the production and characterization of epoxy- and adhesive-free colloidal probes for atomic force microscopy (AFM). Borosilicate glass microspheres are strongly attached to commercial AFM cantilevers exploiting the capillary adhesion force due to the formation of a water meniscus, and then a thermal annealing of the sphere-cantilever system at a temperature slightly below the softening point of borosilicate glass. Controlling the wettability of the surfaces involved turned out to be a crucial element for the control of surface adhesion and for the implementation of a completely adhesive-free production method of colloidal probes. Moreover, we present a statistical characterization protocol of the probe dimensions and roughness based on the AFM inverse imaging of colloidal probes on spiked gratings. We have assessed the influence of defects of the grating on the characterization of the probe, and discussed the accuracy of our characterization technique in comparison to the methods based on scanning electron or optical microscopy, or on the manual analysis of AFM inverse images.
Optically detected nuclear magnetic resonance in n-GaAs using an on-chip microcoil
Authors: Chen Y. S. , Huang J. , Reuter D. , Ludwig A. , Wieck A. D. , Bacher G.
Published: February 2011

Optically detected nuclear magnetic resonance (NMR) with micrometer resolution is demonstrated in n-GaAs using an on-chip microcoil. To trace the Overhauser field, the electron Larmor frequency is monitored via time-resolved magneto-optical Kerr rotation. Sweeping the frequency of the rf magnetic field induced by an on-chip microscale current loop, nuclear spin depolarization is achieved for each isotope species. The experimental data indicate an impact of a local quadrupole field, most likely caused by ionized donors, on the amplitude and linewidth of the NMR spectrum. By applying rf pulse sequences, the Rabi oscillation of A75s nuclear spins is obtained with an effective dephasing time of ∼200 μs.
Assignment of the vibrational spectra of lithium hydroxide monohydrate, LiOH·H2O
Authors: Parker Stewart F. , Refson Keith , Bewley Robert I. , Dent Geoffrey
Published: February 2011

The assignment of the vibrational spectra of lithium hydroxide monohydrate, LiOH·H2O, has been controversial for more than half-a-century. Here we show that only the combination of all three forms of vibrational spectroscopy: infrared, Raman and inelastic neutron scattering spectroscopies coupled with periodic-density functional theory calculations is able to satisfactorily assign the spectra. All previous work based on empirical criteria is, at least partially, incorrect. The librational modes of water do not follow the expected rock > wag > twist order and the calculations indicate that complete or partial deuterium substitution would not be useful in assigning the modes.
Calorimetry of epitaxial thin films
Authors: Cooke David W. , Hellman F. , Groves J. R. , Clemens B. M. , Moyerman S. , Fullerton E. E.
Published: February 2011

Thin film growth allows for the manipulation of material on the nanoscale, making possible the creation of metastable phases not seen in the bulk. Heat capacity provides a direct way of measuring thermodynamic properties of these new materials, but traditional bulk calorimetric techniques are inappropriate for such a small amount of material. Microcalorimetry and nanocalorimetry techniques exist for the measurements of thin films but rely on an amorphous membrane platform, limiting the types of films which can be measured. In the current work, ion-beam-assisted deposition is used to provide a biaxially oriented MgO template on a suspended membrane microcalorimeter in order to measure the specific heat of epitaxial thin films. Synchrotron x-ray diffraction showed the biaxial order of the MgO template. X-ray diffraction was also used to prove the high quality of epitaxy of a film grown onto this MgO template. The contribution of the MgO layer to the total heat capacity was measured to be just 6.5% of the total addenda contribution. The heat capacity of a Fe.49Rh.51 film grown epitaxially onto the device was measured, comparing favorably to literature data on bulk crystals. This shows the viability of the MgO/SiNx-membrane-based microcalorimeter as a way of measuring the thermodynamic properties of epitaxial thin films.
Multiple phosphorus chemical sites in heavily phosphorus-doped diamond
Authors: Okazaki Hiroyuki , Yoshida Rikiya , Muro Takayuki , Nakamura Tetsuya , Wakita Takanori , Muraoka Yuji , Hirai Masaaki , Kato Hiromitsu , Yamasaki Satoshi , Takano Yoshihiko , Ishii Satoshi , Oguchi Tamio , Yokoya Takayoshi
Published: February 2011

We have performed high-resolution core level photoemission spectroscopy on a heavily phosphorus (P)-doped diamond film in order to elucidate the chemical sites of doped-phosphorus atoms in diamond. P 2p core level study shows two bulk components, providing spectroscopic evidence for multiple chemical sites of doped-phosphorus atoms. This indicates that only a part of doped-phosphorus atoms contribute to the formation of carriers. From a comparison with band calculations, possible origins for the chemical sites are discussed.
Li+ ion emission from a hot-plate alumina-silicate source stimulated by flash heating with an infrared laser
Authors: Ni P. A. , Kwan J. W. , Roy P. K. , Waldron W. L.
Published: February 2011

The Neutralized Drift Compression Experiment-II accelerator under construction at Lawrence Berkeley National Laboratory has been designed to employ a lithium-doped alumino-silicate (Al-Si) hot-plate surface-ionization ion source. In order to achieve the design 1 mA/cm2 current density, the emitter must be constantly kept at a high temperature, leading to the accelerated loss of Li material as ions or neutrals. As a result, the estimated lifetime of the source is 50 h. This lifetime can be extended if the source is kept at low temperature during standby, and pulse heated to the high temperature during the ion extraction phase only. A pulsed heating technique based on an infrared laser (CO2 gas discharge, λ = 10.6 μm) is described in this paper. The feasibility of ion current emission stimulated by flash heating with an infrared (IR) laser was demonstrated. High repeatability of the laser-stimulated ion current was observed, creating an opportunity for modulation and gating of the ion current with a laser pulse. It was found that with the available low power (≈115 W/cm2) IR laser, current densities as high as 0.8 mA/cm2 could be achieved with a 2.8 mm diameter source. Various approaches for scaling to a larger (10 cm diameter) source and the application of short pulse, high power lasers are discussed. The results and conclusions of this paper may apply to various species of hot-plate ion sources.
Theory of ionic polymer conductor network composite
Authors: Wang Xiao , Hong Wei
Published: February 2011

Ionic polymer conductor network composite (IPCNC) is a mixed conductor consisting of a network of loaded ionomer and another network of metallic particles. It is known that the microstructure of the composite, especially that of the electrodes, plays a dominating role in the performance of an IPCNC. However, the microstructure of IPCNC has seldom been addressed in theoretical models. This letter formulates a continuum field theory for IPCNC by considering a supercapacitorlike microstructure with a large distributed interfacial area. The theory is then applied to the study of the equilibrium deformation and electrochemistry in a thin-sheet IPCNC actuator.
Some consequences of high temperature water vapor spectroscopy: Water dimer at equilibrium
Authors: Tretyakov M. Yu. , Makarov D. S.
Published: February 2011

It is shown that the evolution of water vapor spectra in the 2500–5000 cm−1 range recorded at 650 K and pressures up to 130 atms after subtraction of monomer contribution may be interpreted qualitatively well on the basis of experimental data on water dimer and trimer obtained from cold molecular beams and in He droplets. The proposed spectroscopic model considers water vapor as a mixture of nonideal monomers, dimers, and trimers at chemical equilibrium. The effect of line mixing is taken into account in the monomer spectrum modeling. Decomposition of the high temperature spectra allowed determining a dimer equilibrium constant that was compared with the previously known values. The contribution of water trimer is assessed. The performed analysis indicates that the number of bound dimers in water vapor is quite large, even at such a high temperature.
Tuning anomalous Hall conductivity in L1 FePt films by long range chemical ordering
Authors: Chen M. , Shi Z. , Xu W. J. , Zhang X. X. , Du J. , Zhou S. M.
Published: February 2011

For L10 FePt films, the anomalous Hall conductivity σxy=−aσxx−b, where a=a0f(T), b=b0f(T), and f(T) is the temperature dependence factor of the spontaneous magnetization. With increasing chemical long range ordering S, a0 changes its sign accompanied by a reduction of its magnitude and b0 increases monotonically. The spin-orbit coupling strength is suggested to increase with increasing S. As an approach, the long range chemical ordering can be used to control the anomalous Hall effect in ferromagnetic alloy films.
Electronic structure of bismuth telluride quasi-two-dimensional crystal: A first principles study
Authors: Li Xin , Ren Hao , Luo Yi
Published: February 2011

The electronic structures of atomically thin layers of bismuth telluride (Bi2Ti3) have been studied by using density functional theory. It is found that quintuple layers of Bi2Te3 are semiconductor with localized shallow bands. The weak covalent Bi–Te2 interaction in quintuple layer allows to further exfoliate it to form bilayer and trilayer sheets. In the latter cases, the valence electrons cannot fully occupy all the valence bands and the sheets become metallic.
Influence of the p-type doping concentration on reflection-mode GaN photocathode
Authors: Wang Xiaohui , Chang Benkang , Ren Ling , Gao Pin
Published: February 2011

Four different p-type doping GaN photocathodes are activated by Cs/O, and the quantum efficiency (QE) curves are obtained. According to the QE equation, the curves are fitted. Both the QE curves and the fitting results show that the optimal p-type doping concentration is at 1017 cm−3. The electron diffusion length and surface-electron escape probability can be balanced well at 1017 cm−3. To a certain degree, thick emission layer is conducive to improving the QE, which is more obvious with the long wavelength.
Failure of one-dimensional Smoluchowski diffusion models to describe the duration of conformational rearrangements in floppy, diffusive molecular systems: A case study of polymer cyclization
Authors: Cheng Ryan R. , Makarov Dmitrii E.
Published: February 2011

Motivated by recent experimental efforts to measure the duration of individual folding/unfolding transitions in proteins and RNA, here we use simulations to study the duration of a simple transition mimicking an elementary step in biopolymer folding: the closure of a loop in a long polymer chain. While the rate of such a transition is well approximated by a one-dimensional Smoluchowski model that views the end-to-end distance dynamics of a polymer chain as diffusion governed by the one-dimensional potential of mean force, the same model fails rather dramatically to describe the duration of such transitions. Instead, the latter timescale is well described by a model where the chain ends diffuse freely, uninfluenced by the average entropic force imposed by the polymer chain. The effective diffusion coefficient then depends on the length scale of the loop closure transition. Our findings suggest that simple one-dimensional models, when applied to estimate the duration of reactive events in complex molecular systems, should be used with caution.
A first-principles study of the influence of helium atoms on the optical response of small silver clusters
Authors: Pereiro M. , Baldomir D. , Arias J. E.
Published: February 2011

Optical excitation spectra of Agn and Agn@He60 (n = 2, 8) clusters are investigated in the framework of the time-dependent density functional theory (TDDFT) within the linear response regime. We have performed the ab initio calculations for two different exact exchange functionals (GGA-exact and LDA-exact). The computed spectra of Agn@He60 clusters with the GGA-exact functional accounting for exchange-correlation effects are found to be generally in a relatively good agreement with the experiment. A strategy is proposed to obtain the ground-state structures of the Agn@He60 clusters and in the initial process of the geometry optimization, the He environment is simulated with buckyballs. A redshift of the silver clusters spectra is observed in the He environment with respect to the ones of bare silver clusters. This observation is discussed and explained in terms of a contraction of the Ag–He bonding length and a consequent confinement of the s valence electrons in silver clusters. Likewise, the Mie–Gans predictions combined with our TDDFT calculations also show that the dielectric effect produced by the He matrix is considerably less important in explaining the redshifting observed in the optical spectra of Agn@He60 clusters.
Doping induced spin filtering effect in zigzag graphene nanoribbons with asymmetric edge hydrogenation
Authors: Kang Jun , Wu Fengmin , Li Jingbo
Published: February 2011

The magnetic and spin dependent transport properties of asymmetrically hydrogenated zigzag graphene nanoribbons, which are C–H2 bonded at one edge while C–H bonded at the other, are investigated from first-principles calculations. Due to their special distributions of the density of states near Fermi level, a perfect (100%) spin filtering effect can be achieved in such graphene nanoribbons through p-type or n-type doping. Moreover, a negative differential resistance effect is observed in both doping case, which results from the reducing of conductance near Fermi level with increasing bias voltage.
Tunable magnonic frequency and damping in [Co/Pd]8 multilayers with variable Co layer thickness
Authors: Pal S. , Rana B. , Hellwig O. , Thomson T. , Barman A.
Published: February 2011

We report the experimental observation of collective picosecond magnetization dynamics in [Co/Pd]8 multilayers with perpendicular magnetic anisotropy. The precession frequency shows large and systematic variation from about 5 GHz to about 90 GHz with the decrease in the Co layer thickness from 1.0 to 0.22 nm due to the linear increase in the perpendicular magnetic anisotropy. The damping coefficient α is found to be inversely proportional to the Co layer thickness and a linear relation between the perpendicular magnetic anisotropy and α is established. We discuss the possible reasons behind the enhanced damping as the d-d hybridization at the interface and spin pumping. These observations are significant for the applications of these materials in spintronics and magnonic crystals.
InAs inserted InGaAs buried channel metal-oxide-semiconductor field-effect-transistors with atomic-layer-deposited gate dielectric
Authors: Xue Fei , Zhao Han , Chen Yen-Ting , Wang Yanzhen , Zhou Fei , Lee Jack C.
Published: February 2011

Performance improvement of InGaAs buried channel metal-oxide-semiconductor field-effect-transistors (MOSFETs) has been achieved by inserting InAs layer and properly designing the inserted layer position. In0.7Ga0.3As and InAs channel buried channel MOSFETs were fabricated and analyzed including drive current, transconductance, effective mobility, and subthreshold swing. All InAs buried channel devices show good off-state and saturation property. By inserting InAs in the middle of InGaAs channel (InGaAs/InAs/InGaAs channel), 37% enhancement of high field effective channel mobility was achieved over devices with pure InGaAs channel. Devices with InAs inserted in the middle exhibits peak effective channel mobility around 6140 cm2/V s and subthreshold swing of 107 mV/dec.
Hospital churn and casemix instability: implications for planning and educating the nursing workforce
Authors: Chiarella Mary , Roydhouse Jessica K.
Published: February 2011

Health workforce planning is a priority for Australian governments at both state and federal levels. Nursing shortages are a significant problem and addressing these shortages is likely to be a component of any workforce plan. This paper looks at the case of hospital nursing and argues that casemix, workforce and management instability inhibit workforce planning for hospital nursing. These issues are related and any efforts to objectively plan the hospital nursing workforce must seek to address them in order to succeed.

What is known about the topic?
Multiple Australian jurisdictions are looking at the issue of health workforce planning. The nursing workforce is a major component of the health workforce and nursing shortages are a problem affecting many healthcare systems and hospitals, and present significant challenges to planning for the nursing workforce.

What does this paper add?
This paper explores the barriers to health workforce planning with regard to acute-care hospital nursing and identifies three inter-related instabilities that are obstacles to objective health workforce planning for this group of health professionals. In addition, the paper sets out strategies to address these instabilities, most specifically in relation to the role and preparation of acute-care nurses.

What are the implications for practitioners?
The paper provides insight into the factors that affect workforce planning and the relationships between them, and the implications of these factors for nurses’ skill and educational requirements.
Magnetoresistance curves of spin valves using the (1 1 0) cobalt ferrite pinning layer
Authors: Matsuda H , Sakakima H
Published: February 2011

Magnetic and magnetoresistance (MR) properties of spin valves composed of Co/Cu/Co/(1 1 0) cobalt ferrite (CFO) were studied, which showed complicated MR properties. It was confirmed from the in-plane magnetization curves that the epitaxial (1 1 0) CFO films have easy axes along the ⟨1 1 0⟩ direction and hard axes along the ⟨0 0 1⟩ direction due to in-plane tensile stress. The spin valves showed quite different MR curves depending on the direction of the magnetic field applied in the plane of (1 1 0) CFO. Butterfly-shaped MR curves, which implied the difference in the coercive fields between the top and bottom Co layers, were observed when the field was applied along the ⟨0 0 1⟩ direction of CFO. On the other hand, when the field was applied along the ⟨1 1 0⟩, unusually shaped MR curves, which showed large MR ratio in spite of the hard direction of the Co layer, were observed. This MR behaviour might indicate the parallel and anti-parallel magnetization configuration between the top and bottom Co layers at zero fields. These magnetic and MR properties could be explained using the micromagnetic calculation of magnetization processes by assuming strong 90° coupling between the bottom Co and CFO layers, and CFO pinning layers having continuous spin rotation at the interface near the bottom Co layer with an exchange stiffness coupling as a spring magnet.
Micromagnetic study of size-dependent picosecond dynamics in single nanomagnets
Authors: Pal Semanti , Kumar Dheeraj , Barman Anjan
Published: February 2011

We present the micromagnetic simulation study of the dynamics of single cylindrical nickel nanomagnets of varying size (aspect ratio), as the shapes of the elements change from disc-like to pillar-like structure. The magnetic ground states change from multi-domain to vortex to out-of-plane magnetized single domain structure and the time-resolved dynamics reveal three distinct modes originating from the centre and end modes of the out-of-plane magnetization (mode 1 and mode 3) and precession of the in-plane magnetization (mode 2). The mode frequencies show strong size dependence including a sharp jump at diameter D = 250 nm (aspect ratio = 0.6), followed by a sharp increase in the frequency with reduced diameter in mode 1. Macrospin simulations reproduce the size variation of frequency of mode 1 only for D ⩽ 250 nm, where the ground states take quasi-single domain configurations. Further analyses after the application of monochromatic harmonic fields to the samples show that size dependence of frequency stems from the variation of the dynamical modes with the continuously varying static magnetic configurations with size and the sharp jump in frequency at D = 250 nm is due to the transition from vortex gyration to precession of the out-of-plane magnetization. Further simulations of local excitation of the sample show the formation of perpendicular standing spin waves and spatial oscillation of the vortex core in nanomagnets with varying aspect ratios.
Ballistic phonon transmission in a symmetric converging–diverging contact of a semiconductor nanowire
Authors: Zou Ming-Liang , Huang Wei-Qing , Huang Gui-Fang , Yao Jing-Jing , Zhang Jian-Hui
Published: February 2011

We study ballistic phonon transmission in a symmetric converging–diverging contact (CDC) of a semiconductor nanowire at low temperatures. Transmission spectra reveal a strong dependence on the length and throat width of the CDC. The spectrum changes from an ascending zigzag pattern into a curve with plateaus as the length of the CDC increases from very small to long enough. The throat width of the CDC has a dominant influence on phonon transmission. For a fixed throat width of the CDC, the thermal conductance decreases with increasing length of the CDC at lower temperatures, and vice versa at higher temperatures. A comparison is made with the phonon transmission in an abrupt constriction. The results suggest that a catenoidal or tapering contact, rather than an abrupt junction, is one of the most critical factors to experimentally observe the quantized limiting value for thermal conductance at very low temperatures (Schwab et al 2000 Nature
404 974).
Protein kinase Cδ regulates vaccinia-related kinase 1 in DNA damage–induced apoptosis
Authors: Park Choon-Ho , Choi Bo-Hwa , Jeong Min-Woo , Kim Sangjune , Kim Wanil , Song Yun Seon , Kim Kyong-Tai
Published: February 2011

Vaccinia-related kinase 1 (VRK1) is a novel serine/threonine kinase that plays an important role in cell proliferation. However, little is known about the upstream regulators of VRK1 activity. Here we provide evidence for a role of protein kinase Cδ (PKCδ) in the regulation of murine VRK1. We show that PKCδ interacts with VRK1, phosphorylates the Ser-355 residue in the putative regulatory region, and negatively regulates its kinase activity in vitro. Intriguingly, PKCδ-induced cell death was facilitated by phosphorylation of VRK1 when cells were exposed to a DNA-damaging agent. In addition, p53 played a critical role in the regulation of DNA damage–induced cell death accompanied by PKCδ-mediated modulation of VRK1. In p53-deficient cells, PKCδ-mediated phosphorylation of VRK1 had no effect on cell viability. However, cells overexpressing p53 exhibited significant reduction of cell viability when cotransfected with both VRK1 and PKCδ. Taken together, these results indicate that PKCδ regulates phosphorylation and down-regulation of VRK1, thereby contributing to cell cycle arrest and apoptotic cell death in a p53-dependent manner.
Direct binding of RalA to PKCη and its crucial role in morphological change during keratinocyte differentiation
Authors: Shirai Yasuhito , Morioka Shoko , Sakuma Megumi , Yoshino Ken-ichi , Otsuji Chihiro , Sakai Norio , Kashiwagi Kaori , Chida Kazuhiro , Shirakawa Ryutaro , Horiuchi Hisanori , Nishigori Chikako , Ueyama Takehiko , Saito Naoaki
Published: February 2011

During differentiation, keratinocytes undergo a dramatic shape change from small and round to large and flat, in addition to production of proteins necessary for the formation of epidermis. It has been shown that protein kinase C (PKC) η is crucial for keratinocyte differentiation. However, its role in this process has yet to be fully elucidated. Here, we show that catalytic activity is not necessary for enlarged and flattened morphology of human keratinocytes induced by overexpression of PKCη, although it is important for gene expression of the marker proteins. In addition, we identify the small G protein RalA as a binding partner of PKCη, which binds to the C1 domain, an indispensable region for the morphological change. The binding led activation of RalA and actin depolymerization associated with keratinocyte differentiation. siRNA techniques proved that RalA is involved in not only the keratinocyte differentiation induced by PKCη overexpression but also normal keratinocyte differentiation induced by calcium and cholesterol sulfate. These results provide a new insight into the molecular mechanism of cytoskeletal regulation leading to drastic change of cell shape.
Alternative attachment factors and internalization pathways for GIII.2 bovine noroviruses
Authors: Mauroy Axel , Gillet Laurent , Mathijs Elisabeth , Vanderplasschen Alain , Thiry Etienne
Published: February 2011

Bovine noroviruses belong to the family Caliciviridae, genus Norovirus. Two genotypes have been described and viruses genetically related to the Jena and Newbury2 strains have been classified into genotypes 1 and 2, respectively. In this study, virus-like particles (VLP) of the previously detected B309 Belgian strain, genetically related to genotype 2 bovine noroviruses, were used to investigate virus–host interactions in vitro. B309 VLP were shown to bind to several bovine cell lines. This binding was not affected by heparinase or chondroitinase treatment but was significantly inhibited by both sodium periodate, α-galactosidase, trypsin and phospholipase C treatment. Cell treatment by neuraminidase also moderately affected this binding. Taken together, these results show that, in addition to a galactosyl residue, sialic acid could also be involved in binding to susceptible cells. In addition, both the cholesterol-dependent pathway and macropinocytosis are used for B309 VLP internalization by Madin–Darby bovine kidney cells. The data increase the knowledge on bovine norovirus cell interactions.
A 1.2–1.6-GHz Substrate-Integrated-Waveguide RF MEMS Tunable Filter
Authors: Sekar Vikram , Armendariz Marcelino , Entesari Kamran
Published: February 2011

This paper presents a high-performance substrate-integrated-waveguide RF microelectromechanical systems (MEMS) tunable filter for 1.2-1.6-GHz frequency range. The proposed filter is developed using packaged RF MEMS switches and utilizes a two-layer structure that effectively isolates the cavity filter from the RF MEMS switch circuitry. The two-pole filter implemented on RT/Duroid 6010LM exhibits an insertion loss of 2.2-4.1 dB and a return loss better than 15 dB for all tuning states. The relative bandwidth of the filter is 3.7 ± 0.5% over the tuning range. The measuredQuof the filter is 93-132 over the tuning range, which is the best reportedQin filters using off-the-shelf RF MEMS switches on conventional printed circuit board substrates. In addition, an upper stopband rejection better than 28 dB is obtained up to 4.0 GHz by employing low-pass filters at the bandpass filter terminals at the cost of 0.7-1.0-dB increase in the insertion loss.
Prevalence of chronic obstructive pulmonary disease in Korea: The fourth Korean National Health and Nutrition Examination Survey, 2008
Authors: YOO KWANG H. , KIM YOUNG S. , SHEEN SEUNG S. , PARK JOO H. , HWANG YONG I. , KIM SANG‐HA , YOON HO I. , LIM SUNG C. , PARK JAE Y. , PARK SEOUNG J. , SEO KI H. , KIM KI U. , OH YEON‐MOK , LEE NA Y. , KIM JI S. , OH KYUNG W. , KIM YOUNG T. , PARK IN‐WON , LEE SANG‐DO , KIM SE K. , KIM YOUNG K. , HAN SUNG K.
Published: February 2011

Background and objective:  Because the mortality and social burden associated with COPD is increasing, repeated surveys of the prevalence of COPD have been used to assess risk factors, detect potential patients, and establish early diagnoses and management protocols. We report the prevalence of spirometrically detected COPD in Korea in 2008, using data from the fourth Korean National Health and Nutrition Survey.

Methods:  Using nationwide stratified random sampling, based on the Korean Statistical Office census, 6840 subjects aged ≥19 years underwent spirometry, which was performed by four trained technicians, during 2008. The place of residence, levels of education and income and smoking status, as well as other results from a COPD survey questionnaire were also assessed.

Results:  Airflow obstruction (FEV1/FVC < 0.7) was detected in 8.8% of subjects aged ≥19 years (11.6% of men and 5.9% of women) and COPD was detected in 13.4% of subjects aged ≥40 years (19.4% of men and 7.9% of women). Of the 6840 subjects, 27.3% were current smokers and 17.2% were former smokers, and the prevalence of COPD was higher in current and former smokers than in never smokers. Approximately 94% of patients with COPD had mild‐to‐moderate disease, without apparent symptoms; only 2.4% had been diagnosed by a physician and only 2.1% of patients had been treated. The independent risk factors for COPD were smoking, advanced age and male gender.

Conclusions:  Although the prevalence of COPD in Korea is high, the disease is underdiagnosed and most COPD patients are under‐treated.
Cough reflex sensitivity and airway inflammation in patients with chronic cough due to non‐acid gastro‐oesophageal reflux
Authors: QIU ZHIHONG , YU LI , XU SHUCHANG , LIU BO , ZHAO TING , LÜ HANJING , QIU ZHONGMIN
Published: February 2011

Background and objective:  The aim of this study was to explore the pathogenesis of chronic cough caused by non‐acid reflux.

Methods:  Seven patients with chronic cough due to non‐acid reflux, 12 patients with chronic cough due to acid reflux, 10 patients with gastro‐oesophageal reflux disease without cough and 12 healthy volunteers were recruited for the study. All subjects underwent oesophageal multi‐channel intraluminal impedance measurements combined with pH monitoring, and assessment of cough reflex sensitivity to capsaicin and induced sputum cytology. The concentrations of substance P, mast cell tryptase, prostaglandin D2 and histamine in induced sputum were measured by ELISA.

Results:  Cough threshold C2 and C5 did not differ between patients with chronic cough due to non‐acid or acid reflux, but the values were significantly lower than those for patients with gastro‐oesophageal reflux disease without cough and healthy volunteers. Weakly acidic reflux episodes were obviously more frequent in patients with chronic cough due to non‐acid reflux than in the other three groups. Sputum substance P and mast cell tryptase concentrations were remarkably increased in patients with chronic cough, but were similar for those with cough due to non‐acid or acid reflux. There were significant inverse correlations between substance P levels and cough threshold C2 or C5 in patients with cough due to non‐acid or acid reflux, and between mast cell tryptase levels and cough threshold C2 in patients with cough due to acid reflux.

Conclusions:  Chronic cough due to non‐acid reflux may be related to cough reflex hypersensitivity caused by neurogenic airway inflammation and mast cell activation, in which weakly acidic reflux is possibly a major factor.
Belonging and community: understandings of ‘home’ and ‘friends’ among the English poor, 1750–18501
Authors: SNELL K. D. M.
Published: February 2011

This article is based on unique ‘narratives of the poor’, that is, letters from poor people to their parishes of settlement, petitions to the London Refuge of the Destitute, and letters from mothers to the London Foundling Hospital, with supportive evidence from newspapers. These display fundamental concepts among the English poor, who were often poorly literate, and who comprised the majority of the population. Discussion focuses upon their understandings of ‘home’, ‘belonging’, ‘friends’, and ‘community’. These key concepts are related here to modern discussions, to set important concerns into historical perspective. ‘Friends’, valuably studied by sociologists such as Pahl, had a wide meaning in the past. ‘Home’ meant (alongside abode) one's parish of legal settlement, where one was entitled to poor relief under the settlement/poor laws. This was where one ‘belonged’. Ideas of ‘community’ were held and displayed even at a distance, among frequently migrant poor, who wrote to their parishes showing strong ties of attachment, right, and local obligation. This discussion explores these issues in connection with belonging and identity. It elucidates the meaning and working of poor law settlement, and is also an exploration of popular mentalities and the semi‐literate ways in which these were expressed.