bluuebunny/crossref_metadata_2025 huggingface dataset:
A 5‐year prospective clinical and radiographic study of non‐submerged dental implants
Authors: Weber Hans‐Peter , Crohin Constant C. , Fiorellini Joseph P.
Published: February 2009

Osseointegrated implants as anchors for various prosthetic reconstructions have become a predictable treatment alternative. It was expected that implants required submucosal placement during the healing period for successful tissue integration. However, it has been demonstrated that healing and long‐term health of implants could be achieved with equal predictability in a 1‐stage, non‐submerged approach. This prospective 5‐year study not only calculates implant success by life table analysis, but also evaluates the correlation between observed bone level changes with clinical parameters as measured by suppuration, plaque indices, bleeding indices, probing depth, attachment level and mobility. A total of 112 ITI® dental implants were inserted in different areas of the jaws. Clinical and radiographic parameters were evaluated annually for 5 years, whereas a portion of the study group for which 6‐year evaluations were available were included in the life‐table analysis. The overall success rate after 5 years in service was 99.1%, while after 6 years it was reduced to 95.5% due to the fracture of 3 implants in 1 patient. The mean crestal bone loss experienced during the first year was 0.6 mm followed by an annual yearly loss of approximately 0.05 mm. No significant differences could be found between the amount of bone loss measured at each of the yearly follow‐up visits. This suggests that statistically the followed implants did not show any radiographically measurable bone loss following the initial period of bone loss associated with implant placement and osseointegration. Low levels of correlation between the individual and cumulative clinical parameters with radiographically measured bone loss suggests that these parameters are of limited clinical value in assessing and predicting future peri‐implant bone loss.
Fractured prosthetic abutments in osseointegrated implants: a technical complication to cope with
Authors: Luterbacher Stefan , Fourmousis Ioannis , Lang Niklaus P. , Brägger Urs
Published: February 2009

In the present report a repair set to retrieve fractured abutments remaining in the implants of the ITI® Dental Implant System is presented. In 1 case in which such fractures occurred, the repair set was successfully applied. After removal of all particles of the fractured prosthetic abutments and recutting the threads, new abutments were used, and the original suprastructure could be reinserted. The causes for such technical failures are discussed considering the relatively sparse information in the literature on that topic.
Ischemic Postconditioning as a Novel Avenue to Protect against Brain Injury after Stroke
Authors: Zhao Heng
Published: February 2009

Ischemic postconditioning initially referred to a stuttering reperfusion performed immediately after reperfusion, for preventing ischemia/reperfusion injury in both myocardial and cerebral infarction. It has evolved into a concept that can be induced by a broad range of stimuli or triggers, and may even be performed as late as 6 h after focal ischemia and 2 days after transient global ischemia. The concept is thought to be derived from ischemic preconditioning or partial/gradual reperfusion, but in fact the first experiment for postconditioning was carried out much earlier than that of preconditioning or partial/gradual reperfusion, in the research on myocardial ischemia. This review first examines the protective effects and parameters of postconditioning in various cerebral ischemic models. Thereafter, it provides insights into the protective mechanisms of postconditioning associated with reperfusion injury and the Akt, mitogen-activated protein kinase (MAPK), protein kinase C (PKC), and ATP-sensitive K+ (KATP) channel cell signaling pathways. Finally, some open issues and future challenges regarding clinical translation of postconditioning are discussed.
Acute Mobile Phones Exposure Affects Frontal Cortex Hemodynamics as Evidenced by Functional Near-Infrared Spectroscopy
Authors: Curcio Giuseppe , Ferrara Michele , Limongi Tania , Tempesta Daniela , Sante Gabriele Di , De Gennaro Luigi , Quaresima Valentina , Ferrari Marco
Published: February 2009

This study aimed to evaluate by functional near-infrared spectroscopy (fNIRS), the effects induced by an acute exposure (40 mins) to a GSM (Global System for Mobile Communications) signal emitted by a mobile phone (MP) on the oxygenation of the frontal cortex. Eleven healthy volunteers underwent two sessions (Real and Sham exposure) after a crossover, randomized, double-blind paradigm. The whole procedure lasted 60 mins: 10-mins baseline (Bsl), 40-mins (Exposure), and 10-mins recovery (Post-Exp). Together with frontal hemodynamics, heart rate, objective and subjective vigilance, and self-evaluation of subjective symptoms were also assessed. The fNIRS results showed a slight influence of the GSM signal on frontal cortex, with a linear increase in [HHb] as a function of time in the Real exposure condition (F4,40 = 2.67; P = 0.04). No other measure showed any GSM exposure-dependent changes. These results suggest that fNIRS is a convenient tool for safely and noninvasively investigating the cortical activation in MP exposure experimental settings. Given the short-term effects observed in this study, the results should be confirmed on a larger sample size and using a multichannel instrument that allows the investigation of a wider portion of the frontal cortex.
Magnetic properties and exchange bias in Mn2O3∕Mn3O4 nanoclusters
Authors: Wang Z. H. , Geng D. Y. , Hu W. J. , Ren W. J. , Zhang Z. D.
Published: February 2009

Mn 2 O 3 ∕ Mn 3 O 4 nanoclusters were prepared by air oxidation of Mn3O4 nanoparticles. The nanoparticles located at the surface of the Mn2O3∕Mn3O4 nanoclusters are oxidized to Mn2O3 to form the special structure of the Mn2O3∕Mn3O4 nanoclusters. An exchange bias was observed in the Mn2O3∕Mn3O4 nanoclusters, which was induced by exchange coupling between ferromagnetic Mn3O4 and antiferromagnetic Mn2O3 phases.
Reversible switching between bidomain states by injection of current pulses in a magnetic wire with out-of-plane magnetization
Authors: Boulle O. , Heyne L. , Rhensius J. , Kläui M. , Rüdiger U. , Joly L. , Le Guyader L. , Nolting F. , Heyderman L. J. , Malinowski G. , Swagten H. J. M. , Koopmans B. , Ulysse C. , Faini G.
Published: February 2009

The influence of current pulses on the domain structure of a 2μm wide wire composed of a soft out-of-plane magnetized magnetic material is studied by high spatial resolution nonintrusive magnetic imaging. The injection of current pulses (1012A∕m2) leads to stable magnetic states composed of two domains with opposite magnetization direction separated by a domain wall parallel to the wire. The direction of the magnetization in the domains is reversed back and forth by applying successive current pulses with opposite polarity. The formation and control of the domain states by the current is attributed to the effect of the Oersted field, which is calculated to be large enough to induce the switching.
Effects of A-site cation disorder on structure and magnetocaloric properties in Y and Sr codoped La2∕3Ca1∕3MnO3 compounds
Authors: Ji Qing , Lv Bin , Wang P. F. , Cai H. L. , Wu X. S. , Liu G. H. , Luo G. S.
Published: February 2009

Structural and magnetocaloric properties for the perovskite manganite La2∕3−xYxCa1∕3−ySryMnO3 (x<0.2) have been studied. These compounds with the fixed A-site average ionic radii of 1.204Å and Mn4+∕Mn3+ ratio were prepared by conventional solid-state reaction technique. The lattice parameters were obtained from refining x-ray diffraction diagrams preformed by Rietveld refinement method. The ferromagnetic ordering temperature TC increases abruptly owing to the increase in the competition between A-site size-disorder degree σ2 and double-exchange interaction resulting from Mn–O–Mn bond angle. Phase transition may be broadened due to the cation disordering at A-site. Sample with x=0.01 appears a large magnetic entropy ΔSM=3.3Jkg−1K−1 at the Curie temperature TC=274K, which may be used as a promising candidate for magnetic refrigerant near room temperature.
Ru/FeCoB double layered film with high in-plane magnetic anisotropy field of 500 Oe
Authors: Hirata Ken-ichiro , Hashimoto Atsuto , Matsuu Toshimitsu , Nakagawa Shigeki
Published: February 2009

FeCoB layers prepared on Ru underlayer possess a high saturation magnetization Ms and a high in-plane magnetic anisotropy filed Hk. Effects of preparation conditions were investigated. Low Ar gas pressure condition and thicker film thickness were effective to attain distortion of FeCo crystallite. As the crystallinity of Ru underlayer became higher, higher Hk was induced. The accumulation of anisotropic stress in the film caused by the oblique incidences of depositing atoms with high energy seems to be one of the important effects to attain high anisotropy field. It was succeeded to prepare the Ru/FeCoB film with high Hk of 500 Oe.
Tractable spin-pure methods for bond breaking: Local many-electron spin-vector sets and an approximate valence bond model
Authors: Small David W. , Head-Gordon Martin
Published: February 2009

For a given number of electrons, total spin, and matching spin z-component, we construct a set that spans the many-electron spin subspace associated with these spin values. Each vector in the set is tensorially related to spin-pure vectors of six electrons or less. We show that in the limit of separated atoms coupled to any allowed overall spin, the corresponding spin vector has a simple form relative to the introduced sets. From this, we set up a model that is computationally simple, spin pure, size consistent, and able to properly treat molecules as they dissociate into atoms or fragments.
Polyaniline nanowires-gold nanoparticles hybrid network based chemiresistive hydrogen sulfide sensor
Authors: Shirsat Mahendra D. , Bangar Mangesh A. , Deshusses Marc A. , Myung Nosang V. , Mulchandani Ashok
Published: February 2009

We report a sensitive, selective, and fast responding room temperature chemiresistive sensor for hydrogen sulfide detection and quantification using polyaniline nanowires-gold nanoparticles hybrid network. The sensor was fabricated by facile electrochemical technique. Initially, polyaniline nanowires with a diameter of 250–320 nm bridging the gap between a pair of microfabricated gold electrodes were synthesized using templateless electrochemical polymerization using a two step galvanostatic technique. Polyaniline nanowires were then electrochemically functionalized with gold nanoparticles using cyclic voltammetry technique. These chemiresistive sensors show an excellent limit of detection (0.1 ppb), wide dynamic range (0.1–100 ppb), and very good selectivity and reproducibility.
Dependence of critical current of spin transfer torque-driven magnetization dynamics on free layer thickness
Authors: Taniguchi Tomohiro , Imamura Hiroshi
Published: February 2009

The dependence of the critical current of spin transfer torque-driven magnetization dynamics on the free layer thickness was studied by taking into account both the finite penetration depth of the transverse spin current and spin pumping. We showed that the critical current remains finite in the zero-thickness limit of the free layer for both parallel and antiparallel alignments. We also showed that the remaining value of the critical current of parallel to antiparallel switching is larger than that of antiparallel to parallel switching.
Magnetic field dependent critical current density of Bi–Sr–Ca–Cu–O superconductor in bulk and tape form with addition of Fe3O4 magnetic nanoparticles
Authors: Abd-Shukor R. , Kong W.
Published: February 2009

The (Bi,Pb)2Sr2Ca2Cu3O10-(Fe3O4)x superconductor for x=0, 0.01, 0.03, and 0.05 were prepared. The average size of Fe3O4 used was 40 nm. The maximum critical current density (Jc) in the bulk form was observed in the x=0.01 sample. Based on this result, Ag sheathed high temperature superconductor tapes with starting compositions (Bi,Pb)2Sr2Ca2Cu3O10-(Fe3O4)0.01 were fabricated using the powder in tube method. The microstructure, phase formation, critical temperature, and transport critical current density were studied. The Jc of the nanosized Fe3O4 added tapes is 5130 A/cm2 at 77 K and 23130 A/cm2 at 30 K in zero fields. The nonadded tapes showed a lower Jc, 3090 A/cm2 at 77 K and 12 400 A/cm2 at 30 K. A sudden decrease in Jc in low magnetic fields (B<0.10 T) when applied parallel and perpendicular to the tapes surface was observed. By adding magnetic nanoparticles, the full vortex magnetic energy can be used to enhance Jc and thus, magnetic nanoparticles such as Fe3O4 can act as an effective flux pinning center leading to the enhancement of Jc in the bulk as well as the tape form.
Comparative analysis of intermittent burst temporal characteristics at the edge of the CASTOR and Tore Supra tokamaks
Authors: Nanobashvili I. , Devynck P. , Gunn J. P. , Nanobashvili S. , Stöckel J. , Van Oost G.
Published: February 2009

Temporal characteristics of intermittent positive bursts of plasma density in the scrape-off layer of the CASTOR and Tore Supra tokamaks are investigated. A monotonic radial decrease of average burst rate together with an increase of average burst duration is observed in the Tore Supra tokamak [I. Nanobashvili et al., Czech. J. Phys. 56, 1339 (2006); I. Nanobashvili et al., J. Nucl. Mater. 363–365, 622 (2007)]. At the edge of the CASTOR tokamak the temporal characteristics stay nearly constant within a quite wide radial region. The reason is that radially elongated turbulent structures (streamers) govern the radial transport in CASTOR [P. Devynck et al., Phys. Plasmas 13, 102505 (2006)]. A comparative analysis allows to conclude that radial transport at the edge of the Tore Supra tokamak is governed by blob-like structures. Plasma biasing at the edge of CASTOR significantly modifies the burst characteristics, reduces plasma transport, and considerably improves the confinement.
Resonance and antiresonance effects in electronic transport through several-quantum-dot combinations
Authors: Sun Z. Z. , Zhang R. Q. , Fan W. , Wang X. R.
Published: February 2009

We investigated the resonance and antiresonance effects in electronic transport through several-quantum-dot combinations by using the nonequilibrium Green’s function method. All distinctive quantum-dot (QD) arrangements with one to three QDs and with different architectures were studied systematically. The theoretical and numerical results show that a peak in the current-voltage spectrum can be attributed to the resonance effect, whereas a dip is due to the antiresonance effect. The results will help experimenters to better understand their electronic measurements.
First-principles calculations of enhanced ferromagnetism in ZnO codoped with cobalt and nitrogen
Authors: Assadi M. H. N. , Zhang Y. B. , Li S.
Published: February 2009

Using first-principles calculations based on density functional theory, N-codoped ZnO:Co has been demonstrated to be potentially a p-type diluted magnetic semiconductor. By investigating 13 geometrically distinct configurations, Co and N dopants are found to have a tendency toward staying close to each other with most stable –O–Co–N–Co–O– complexes. The dominant ferromagnetic interaction is due to the hybridization between N 2p and Co 3d states, which is strong enough to lead to hole-mediated ferromagnetism at room temperature. The ferromagnetic coupling strongly relies on the distance of N from Co, while it weakly depends on the direction of aligned Co ions.
Quantitative analysis of signal transduction in motile and phototactic cells by computerized light stimulation and model based tracking
Authors: Streif Stefan , Staudinger Wilfried Franz , Oesterhelt Dieter , Marwan Wolfgang
Published: February 2009

To investigate the responses of Halobacterium salinarum to stimulation with light (phototaxis and photokinesis), we designed an experimental setup consisting of optical devices for automatic video image acquisition and computer-controlled light stimulation, and developed algorithms to analyze physiological responses of the cells. Cells are categorized as motile and nonmotile by a classification scheme based on the square displacement of cell positions. Computerized tracking based on a dynamic model of the stochastic cell movement and a Kalman filter-based algorithm allows smoothed estimates of the cell tracks and the detection of physiological responses to complex stimulus patterns. The setup and algorithms were calibrated which allows quantitative measurements and systematic analysis of cellular sensing and response. Overall, the setup is flexible, extensible, and consists mainly of commercially available products. This facilitates modifications of the setup and algorithms for physiological studies of the motility of cells or microorganisms.
Long range resonance energy transfer from a dye molecule to graphene has (distance)−4 dependence
Authors: Swathi R. S. , Sebastian K. L.
Published: February 2009

In our previous report on resonance energy transfer from a dye molecule to graphene [J. Chem. Phys.129, 054703 (2008)], we had derived an expression for the rate of energy transfer from a dye to graphene. An integral in the expression for the rate was evaluated approximately. We found a Yuwaka-type dependence of the rate on the distance. We now present an exact evaluation of the integral involved, leading to very interesting results. For short distances (z<20 Å), the present rate and the previous rate are in good agreement. For larger distances, the rate is found to have a z−4 dependence on the distance, exactly. Thus we predict that for the case of pyrene on graphene, it is possible to observe fluorescence quenching up to a distance of 300 Å. This is in sharp contrast to the traditional fluorescence resonance energy transfer where the quenching is observable only up to 100 Å.
Localizing normal modes in large molecules
Authors: Jacob Christoph R. , Reiher Markus
Published: February 2009

We show how vibrational spectra obtained from quantum chemical calculations can be analyzed by transforming the calculated normal modes contributing to a certain band in the vibrational spectrum to a set of localized modes. This is achieved by determining the unitary transformation that leads to modes which are maximally localized with respect to a suitably defined criterion. We demonstrate that these localized modes are more appropriate for the analysis of calculated vibrational spectra of polypeptides and proteins than the normal modes, which are usually delocalized over the whole system. Both the frequencies at which the bands in the vibrational spectra appear and the total intensities of these bands can be interpreted in terms of the localized modes. Furthermore, we show how coupling constants for the interaction between the localized modes, which can be employed to rationalize the observed band shapes, can be extracted from the calculations.
Competition between self-assembly and surface adsorption
Authors: Dudowicz Jacek , Douglas Jack F. , Freed Karl F.
Published: February 2009

We investigate a minimal equilibrium polymerization model for the competition between self-assembly on a boundary and in solution that arises when an assembling system is in the presence of an adsorbing interface. Adsorption generally occurs upon cooling, but assembly (equilibrium polymerization) may arise either upon cooling or heating. Both cases are shown to exhibit a coupling between adsorption and self-assembly. When both assembly and adsorption proceed upon cooling, a change in the ratio of the enthalpy of adsorption to the enthalpy of assembly in solution can switch the system between a predominance of self-assembly in solution to assembly on the substrate. If assembly is promoted by heating and adsorption by cooling, as in many self-assembling proteins in aqueous solution, then a self-assembly analog of a closed loop phase boundary is found. In particular, the order parameter for assembly on the surface exhibits a peak as a function of temperature. As demonstrated by illustrative examples, the coupling between surface adsorption and self-assembly provides a powerful means of switching self-assembly processes on and off. Understanding and controlling this switching phenomenon will be useful in designing and directing self-assembly processes on surfaces for applications to nanomanufacturing and in developing treatments for diseases arising from pathological adsorption-induced assembly.
Simulations and experiments of intense ion beam current density compression in space and time
Authors: Sefkow A. B. , Davidson R. C. , Gilson E. P. , Kaganovich I. D. , Anders A. , Coleman J. E. , Leitner M. , Lidia S. M. , Roy P. K. , Seidl P. A. , Waldron W. L. , Yu S. S. , Welch D. R.
Published: February 2009

The Heavy Ion Fusion Science Virtual National Laboratory has achieved 60-fold longitudinal pulse compression of ion beams on the Neutralized Drift Compression Experiment (NDCX) [P. K. Roy et al., Phys. Rev. Lett. 95, 234801 (2005)]. To focus a space-charge-dominated charge bunch to sufficiently high intensities for ion-beam-heated warm dense matter and inertial fusion energy studies, simultaneous transverse and longitudinal compression to a coincident focal plane is required. Optimizing the compression under the appropriate constraints can deliver higher intensity per unit length of accelerator to the target, thereby facilitating the creation of more compact and cost-effective ion beam drivers. The experiments utilized a drift region filled with high-density plasma in order to neutralize the space charge and current of an ∼300 keV K+ beam and have separately achieved transverse and longitudinal focusing to a radius <2 mm and pulse duration <5 ns, respectively. Simulation predictions and recent experiments demonstrate that a strong solenoid (Bz<100 kG) placed near the end of the drift region can transversely focus the beam to the longitudinal focal plane. This paper reports on simulation predictions and experimental progress toward realizing simultaneous transverse and longitudinal charge bunch focusing. The proposed NDCX-II facility would capitalize on the insights gained from NDCX simulations and measurements in order to provide a higher-energy (>2 MeV) ion beam user-facility for warm dense matter and inertial fusion energy-relevant target physics experiments.
Breakup of drops in a microfluidic T junction
Authors: Leshansky A. M. , Pismen L. M.
Published: February 2009

We propose a mechanism of droplet breakup in a symmetric microfluidic T junction driven by pressure decrement in a narrow gap between the droplet and the channel wall. This mechanism works in a two-dimensional setting where the capillary (Rayleigh–Plateau) instability of a cylindrical liquid thread, suggested earlier [D. Link, S. Anna, D. Weitz, and H. Stone, Phys. Rev. Lett. 92, 054503 (2004)] as the cause of breakup, is not operative, but it is likely to be responsible for the breakup also in three dimensions. We derive a dependence of the critical droplet extension on the capillary number Ca by combining a simple geometric construction for the interface shape with lubrication analysis in a narrow gap where the surface tension competes with the viscous drag. The theory, formally valid for Ca1/5⪡1, shows a very good agreement with numerical results when it is extrapolated to moderate values of Ca.
Electromigration-induced bond improvement for three-dimensional integrated circuits
Authors: Leong H. L. , Gan C. L. , Thompson C. V. , Pey K. L. , Li H. Y.
Published: February 2009

Bonded Cu interconnects were stressed with increasing current while the contact resistance was measured. Interconnects with high initial contact resistance exhibited a contact resistance reduction phenomenon at a critical current density. The higher the initial contact resistance is, the lower the current required to trigger this phenomenon. Interconnects with low initial contact resistances exhibit this phenomenon only when stressed at a higher temperature. Electromigration is shown to be the most likely mechanism responsible for this phenomenon. This behavior can be used for low-temperature improvement of the quality of bonded interconnects for three-dimensional integrated circuits.
A two junction, four terminal photovoltaic device for enhanced light to electric power conversion using a low-cost dichroic mirror
Authors: Rühle Sven , Segal Akiba , Vilan Ayelet , Kurtz Sarah R. , Grinis Larissa , Zaban Arie , Lubomirsky Igor , Cahen David
Published: February 2009

A low-cost dichroic mirror can be used successfully for solar spectrum splitting to enhance solar to electrical energy conversion. The mirror is optimized for use with a polycrystalline silicon photovoltaic cell (pc-Si). With the dichroic mirror simultaneous excitation of a medium-efficient (11.1%) commercial pc-Si and a custom-made high band gap GaInP cell (12.3%), yields 16.8% efficiency, with both cells operating at maximum power. Our results clearly show that what is missing for this simple low-cost enhancement of Si solar cell efficiency are low-cost high band gap cells.
Resampling improves the efficiency of a “fast-switch” equilibrium sampling protocol
Authors: Lyman Edward , Zuckerman Daniel M.
Published: February 2009

We recently applied a multistage reweighting scheme to demonstrate the sampling of equilibrium configurational distributions of peptides from nonequilibrium, simulated annealing trajectories [E. Lyman and D. M. Zuckerman, J. Chem. Phys. 127, 065101 (2007)]. Here we demonstrate that a statistical variance reduction technique, resampling, improves the efficiency of the protocol by about a factor of 3 in a penta-alanine system. While we are not optimistic for the ultimate efficiency of purely temperature-based sampling methods, resampling-type improvements ought to find application in other (formally equivalent) nonequilibrium sampling protocols, such as Jarzynski-relation calculations and annealing-based NMR structure calculations.
Enhanced exchange bias in sub-50-nm IrMn/CoFe nanostructure
Authors: Rahman M. Tofizur , Shams Nazmun N. , Wang Ding Shuo , Lai Chih-Huang
Published: February 2009

The exchange bias field (Hex) of IrMn/CoFe deposited on a large-area nanoporous anodized alumina (AAO) is tailored by varying the pore density (D) and the network width (w) of AAO. The Hex increases with increasing D and reaches its maximum at D=5.6×1010 cm−2 and w∼28 nm. The enhancement in Hex, twice larger than that of the continuous film, is attributed to the reduction in antiferromagnetic (AFM) and ferromagnetic (FM) domain sizes. The suppression of Hex is observed for further increase in D, which may result from the excessive misalignment of AFM and FM spins and weakened AFM anisotropy.
Robust, easily shaped, and epoxy-free carbon-fiber-aluminum cathodes for generating high-current electron beams
Authors: Liu Lie , Li Limin , Wen Jianchun , Wan Hong
Published: February 2009

This paper presents the construction of carbon-fiber-aluminum (CFA) cathode by squeezing casting and its applications for generating high-current electron beams to drive high-power microwave sources. The fabrication process avoided using epoxy, a volatile deteriorating the vacuum system. These cathodes had a higher hardness than conventional aluminum, facilitating machining. After surface treatment, carbon fibers became the dominator determining emission property. A multineedle CFA cathode was utilized in a triode virtual cathode oscillator (vircator), powered by a ∼450 kV, ∼400 ns pulse. It was found that 300–400 MW, ∼250 ns microwave was radiated at a dominant frequency of 2.6 GHz. Further, this cathode can endure high-current-density emission without detectable degradation in performance as the pulse shot proceeded, showing the robust nature of carbon fibers as explosive emitters. Overall, this new class of cold cathodes offers a potential prospect of developing high-current electron beam sources.
Lattice strain in bulk GaN epilayers grown on CrN/sapphire template
Authors: Lee S. W. , Ha Jun-Seok , Lee Hyun-Jae , Lee Hyo-Jong , Goto H. , Hanada T. , Goto T. , Fujii Katsushi , Cho M. W. , Yao T.
Published: February 2009

Microphotoluminescence spectroscopy is used to investigate local strain in GaN films grown on c-sapphire with CrN buffer, where the CrN buffer is partly etched. Biaxial compressive strain dominates GaN films grown on CrN buffer/c-plane sapphire. The emission energies of D0X, FXA, and FXA-1LO emission lines shift gradually from a high value to a low one, as the excitation laser beam scans from the unetched side of the sample to the etched side, while the emission intensities show only a slight change. No cracking occurs in the GaN film during etching except a change in bending of the detached part of the GaN film from convex to concave as determined by surface profiler. Both the lattice parameter and the energy position of the bound exciton emission peaks from a completely detached GaN are almost the same as those reported for strain-free GaN. The line width of the (0002) ω scan of a GaN film is narrowed from 352 to 331 arc sec through detaching presumably due to decrease in bending. Those properties suggest that gradual lattice strain relaxation takes place in GaN layers grown on CrN buffer as etching of CrN buffer proceeds and that the chemical lift-off enables to detach a GaN film from a sapphire substrate without generating defects.
One-step synthesis of Ge–SiO2 core-shell nanowires
Authors: Sutter Eli , Camino Fernando , Sutter Peter
Published: February 2009

We report on a one-step process based on thermal evaporation at moderate temperatures that yields single-crystalline Ge nanowires (NWs) encapsulated in SiO2 shells. The dielectric shell forms around the Ge NW core during the NW growth process itself, an advantage in the assembly of NW devices such as surround-gate NW field-effect transistors (FETs). The formation of the core-shell structures proceeds via an unconventional vapor-liquid-solid process involving root growth of SiGe NWs and selective Si oxidation by background oxygen in the reactor. Electrical measurements of the p-type Ge–SiO2 FET devices show efficient gate control and hole mobilities of 20 cm2/V s.
Random telegraph signal noise in gate-all-around silicon nanowire transistors featuring Coulomb-blockade characteristics
Authors: Zhuge Jing , Zhang Liangliang , Wang Runsheng , Huang Ru , Kim Dong-Won , Park Donggun , Wang Yangyuan
Published: February 2009

Random telegraph signal (RTS) noise is experimentally investigated in silicon nanowire transistors (SNWTs) fabricated with complementary-metal-oxide-semiconductor compatible top-down approach. The observed RTS is found to have Coulomb-blockade characteristics rather than those described by conventional Shockley–Read–Hall theory. The capture and emission time constants of oxide traps strongly depend on the gate bias due to strong quantum confinement and enhanced electrical field in nanowire structures. Amplitude of single RTS in SNWTs is found within 10%, while large amplitude of multilevel RTS up to 34% at room temperature is observed due to the ultranarrow channel and the behavior of independent multitraps in SNWTs. Widely spread time constants of oxide traps and slow RTS of very long-time constants (several hundred seconds) are also observed in SNWTs.
Coupling efficiency of monolithic, waveguide-integrated Si photodetectors
Authors: Ahn Donghwan , Hong Ching-yin , Kimerling Lionel C. , Michel Jurgen
Published: February 2009

A waveguide-integrated photodetector provides a small-footprint, low-capacitance design that overcomes the bandwidth-efficiency trade-off problem of free space optics. High performance silicon devices are critical to the emergence of electronic-photonic integrated circuits on the complementary metal oxide semiconductor platform. We have fabricated vertical p-i-n silicon photodetectors that are monolithically integrated with compact silicon oxynitride channel waveguides. We report over 90% coupling efficiency of 830 nm light from the silicon oxynitride (SiOxNy) channel waveguide to the silicon photodetector. We analyze the dependence of coupling on waveguide index by comparing coupling from low index-contrast waveguides and high index-contrast waveguides.
Injectorless quantum cascade laser with low voltage defect and improved thermal performance grown by metal-organic chemical-vapor deposition
Authors: Dey Dibyendu , Wu Wei , Memis Omer Gokalp , Mohseni Hooman
Published: February 2009

We demonstrate a strain-compensated injectorless quantum cascade laser (I-QCL), grown by metal-organic chemical-vapor deposition, with a very low voltage defect operating up to room temperature. We experimentally study the effect of voltage defect on thermal performance by comparing the rise in core temperature over a 300 ns pulse width of I-QCL and conventional QCL, working in pulsed mode using time-resolved step scan. I-QCL shows approximately eight times lower rate of rise in core temperature compared to conventional QCL.
High mobility organic thin film transistors based on monocrystalline rubrene films grown by low pressure hot wall deposition
Authors: Chen Yi , Shih Ishiang
Published: February 2009

Monocrystalline rubrene (5,6,11,12-tetraphenylnaphthacene) films with thickness between 1 and 10 μm and grain sizes as large as 100 μm×2 mm were deposited on thin film transistor substrates at rates ∼500 nm/min by a low pressure and hot wall deposition method. Organic thin film transistors with these high quality thin films as active channels have field effect mobility as high as 2.4 cm2/V s and ON/OFF current ratios around 106. The morphology and crystallinity of rubrene films under different deposition conditions were also studied to determine the optimal film deposition conditions.
Study of weak ferromagnetism in polycrystalline multiferroic Eu doped bismuth ferrite
Authors: Reddy V. Raghavendra , Kothari Deepti , Gupta Ajay , Gupta S. M.
Published: February 2009

Room temperature spontaneous magnetization and dielectric anomaly at Néel temperature are observed in 15% Eu doped bismuth ferrite indicating the multiferroic nature of the sample. With 15% Eu doping structural transformation from rhombohedral to triclinic is observed. Fe3+ and Eu3+ oxidation states are observed from F57e and E151u Mossbauer measurements, respectively. The high field F57e Mossbauer spectrum in longitudinal geometry shows an enhancement in the intensity of lines corresponding to Δm=0 transitions, i.e., second and fifth lines in six line pattern. This observation suggests that the origin of spontaneous magnetization is due to weak ferromagnetism of Dzyaloshinskii–Moriya type.
The intrinsic elasticity of twin walls: Ferrielectric twin walls in ferroelastic CaTiO3
Authors: Goncalves-Ferreira Liliana , Redfern Simon A. T. , Atacho Emilio , Salje Ekhard K. H.
Published: February 2009

Computer simulation of ferrielectric domain walls in ferroelastic CaTiO3 demonstrate that twin walls possess almost the same compressibility as the bulk. The Ti–Ti repetition length inside the wall is approximately 0.2% greater than the equivalent lattice parameter of the bulk. A slight reduction in the uniaxial compressibility perpendicular to the twin wall is compared with predictions of various theoretical models which give either large softening or large hardening. Simple spring models predict correctly that any change is expected to be small for relevant potentials far from the ferroelastic transition point.
Origin of the ambipolar operation of a pentacene field-effect transistor fabricated on a poly(vinyl alcohol)-coated Ta2O5 gate dielectric with Au source/drain electrodes
Authors: Takebayashi Satoko , Abe Shigeomi , Saiki Koichiro , Ueno Keiji
Published: February 2009

Pentacene field-effect transistors (FETs) were fabricated on a poly(vinyl alcohol) (PVA)-coated Ta2O5 gate dielectric using Au source/drain electrodes. Their device characteristics were examined before and after annealing the FETs in a vacuum. Before annealing, the pentacene FET showed an ambipolar operation with hole mobility of 0.1 cm2 V−1 s−1 and electron mobility of 0.005 cm2 V−1 s−1. After annealing at 50 °C, however, the p-type operation characteristics almost diminished and an enhanced n-type operation was observed. Na+ ions in the PVA are supposed to change the character of the injection barrier at the Au/pentacene junction and enable the n-type operation.
Size-dependent oxidation behavior for the anomalous initial thermal oxidation process of Si
Authors: Cui H. , Sun Y. , Yang G. Z. , Yang G. W. , Wang C. X.
Published: February 2009

To have a clear insight into the physical origin of the anomalous initial oxidation behavior for silicon oxidation, we proposed a kinetics model by introducing the nanosize effect into the oxidation process. The rate equation of oxide growth was calculated based on our model, and these results are in excellent agreement with experiments. Notably, the present model not only bridges the breakdown of Deal–Grove model [B. E. Deal and A. S. Grove, J. Appl. Phys. 36, 3770 (1965)] in the anomalous initial region but also accurately describes the oxidation process in the whole oxidation regions over a wide temperature range.
Electrical spin injection from Fe into ZnSe(001)
Authors: Hanbicki A. T. , Kioseoglou G. , Holub M. A. , van ’t Erve O. M. J. , Jonker B. T.
Published: February 2009

We have electrically injected spin-polarized current from ferromagnetic Fe(001) contacts into n-type ZnSe(001) using reverse-biased Schottky tunnel barriers which form at the Fe/ZnSe interface. Electrons transport through 3000 Å of n-ZnSe and radiatively recombine in GaAs, where the circular polarization of the electroluminescence provides a quantitative measure of spin polarization. We measure electron spin polarizations over 50% in the GaAs up to 100 K. Spin injection efficiencies achieved in Fe/ZnSe are comparable to those reported for Fe/AlGaAs or Fe/GaAs Schottky tunnel structures, consistent with the common band symmetries of the Fe majority band and the conduction band of the respective semiconductor.
Breakdown of the Debye approximation for the acoustic modes with nanometric wavelengths in glasses
Authors: Monaco Giulio , Giordano Valentina M.
Published: February 2009

On the macroscopic scale, the wavelengths of sound waves in glasses are large enough that the details of the disordered microscopic structure are usually irrelevant, and the medium can be considered as a continuum. On decreasing the wavelength this approximation must of course fail at one point. We show here that this takes place unexpectedly on the mesoscopic scale characteristic of the medium range order of glasses, where it still works well for the corresponding crystalline phases. Specifically, we find that the acoustic excitations with nanometric wavelengths show the clear signature of being strongly scattered, indicating the existence of a cross-over between well-defined acoustic modes for larger wavelengths and ill-defined ones for smaller wavelengths. This cross-over region is accompanied by a softening of the sound velocity that quantitatively accounts for the excess observed in the vibrational density of states of glasses over the Debye level at energies of a few milli-electronvolts. These findings thus highlight the acoustic contribution to the well-known universal low-temperature anomalies found in the specific heat of glasses.
Angiotensin II signaling increases activity of the renal Na-Cl cotransporter through a WNK4-SPAK-dependent pathway
Authors: San-Cristobal Pedro , Pacheco-Alvarez Diana , Richardson Ciaran , Ring Aaron M. , Vazquez Norma , Rafiqi Fatema H. , Chari Divya , Kahle Kristopher T. , Leng Qiang , Bobadilla Norma A. , Hebert Steven C. , Alessi Dario R. , Lifton Richard P. , Gamba Gerardo
Published: February 2009

Mutations in the kinase WNK4 cause pseudohypoaldosteronism type II (PHAII), a syndrome featuring hypertension and high serum K
+
levels (hyperkalemia). WNK4 has distinct functional states that regulate the balance between renal salt reabsorption and K
+
secretion by modulating the activities of renal transporters and channels, including the Na-Cl cotransporter NCC and the K
+
channel ROMK. WNK4's functions could enable differential responses to intravascular volume depletion (hypovolemia) and hyperkalemia. Because hypovolemia is uniquely associated with high angiotensin II (AngII) levels, AngII signaling might modulate WNK4 activity. We show that AngII signaling in
Xenopus
oocytes increases NCC activity by abrogating WNK4's inhibition of NCC but does not alter WNK4's inhibition of ROMK. This effect requires AngII, its receptor AT1R, and WNK4, and is prevented by the AT1R inhibitor losartan. NCC activity is also increased by WNK4 harboring mutations found in PHAII, and this activity cannot be further augmented by AngII signaling, consistent with PHAII mutations providing constitutive activation of the signaling pathway between AT1R and NCC. AngII's effect on NCC is also dependent on the kinase SPAK because dominant-negative SPAK or elimination of the SPAK binding motif in NCC prevent activation of NCC by AngII signaling. These effects extend to mammalian cells. AngII increases phosphorylation of specific sites on SPAK and NCC that are necessary for activation of each in mpkDCT cells. These findings place WNK4 in the signaling pathway between AngII and NCC, and provide a mechanism by which hypovolemia maximizes renal salt reabsoprtion without concomitantly increasing K
+
secretion.
Effect of clinical audits of radiation use in one hospital district in finland
Authors: Hirvonen-Kari M. , Salo S. , Dean K. , Kivisaari L.
Published: February 2009

Background: A clinical audit is a systematic, independent, and documented process to improve the quality of radiological processes and radiation safety for patients.

Purpose: To evaluate the effect of an audit process by comparing the results of two consecutive audits at the same units.

Material and Methods: Audits were carried out twice at each imaging unit in the southwest hospital district of Finland: first, at the end of 2003, and again in November 2007. Both evaluations were carried out in a similar way: by interviewing personnel and examining documents, independent experts from other hospital districts ensured that diagnostic medical imaging processes at each unit were carried out according to generally accepted standards for good medical radiological procedures. The results of the consecutive audits were compared in order to analyze the effects of the clinical audits.

Results: The use of radiation was in accordance with the requirements and standards of good medical procedures at every audited unit during both evaluations. The list of audit criteria was fulfilled satisfactorily on both occasions at all of the audited units, and clearly better during the second run. In the first audit, the auditors made 80 recommendations for improving diagnostic procedures and, in the second audit, 53 recommendations. During the first audit, most of the recommendations (22/80) concerned instructions in the fundamental practice of examining a patient. During the second audit, most recommendations were in the category of radiation doses.

Conclusion: The clinical audit had a positive impact on the practice of work procedures in radiological departments. Most of the recommendations made after the first audit had been taken into consideration by the time of the second audit.
Colonization Sites of USA300 Methicillin-ResistantStaphylococcus aureusin Residents of Extended Care Facilities
Authors: Shurland Simone M. , Stine O. Colin , Venezia Richard A. , Johnson Jennifer K. , Zhan Min , Furuno Jon P. , Miller Ram R. , Johnson Tamara , Roghmann Mary-Claire
Published: February 2009

Background.

The anterior nares are the most sensitive single site for detecting methicillin-resistantStaphylococcus aureus(MRSA) colonization. Colonization patterns of USA300 MRSA colonization are unknown.

Objectives.

To assess whether residents of extended care facilities who are colonized with USA300 MRSA have different nares or skin colonization findings, compared with residents who are colonized with non-USA300 MRSA strains.

Methods.

The study population included residents of 5 extended care units in 3 separate facilities who had a recent history of MRSA colonization. Specimens were obtained weekly for surveillance cultures from the anterior nares, perineum, axilla, and skin breakdown (if present) for 3 weeks. MRSA isolates were categorized as USA300 MRSA or non-USA300 MRSA.

Results.

Of the 193 residents who tested positive for MRSA, 165 were colonized in the anterior nares, and 119 were colonized on their skin. Eighty-four percent of USA300 MRSA-colonized residents had anterior nares colonization, compared with 86% of residents colonized with non-USA300 MRSA (P= .80). Sixty-six percent of USA300 MRSA–colonized residents were colonized on the skin, compared with 59% of residents colonized with non-USA300 MRSA (P= .30).

Conclusions.

Colonization patterns of USA300 MRSA and non-USA300 MRSA are similar in residents of extended care facilities. Anterior nares cultures will detect most—but not all—people who are colonized with MRSA, regardless of whether it is USA300 or non-USA300 MRSA.
Adverse Events After Administration of Tetanus-Diphtheria-Acellular Pertussis Vaccine to Healthcare Workers
Authors: Sandora Thomas J. , Pfoh Elizabeth , Lee Grace M.
Published: February 2009

Healthcare workers who received the tetanus-diphtheria–acellular pertussis (Tdap) vaccine were surveyed about adverse events. Local adverse events were more common among women and among those who received the Tdap vaccine less than 5 years after they had received the tetanus-diphtheria vaccine. Systemic adverse events were more common among healthcare workers aged less than 30 years. These findings provide guidance for counseling of healthcare workers who receive Tdap vaccine.
Biomarker discovery in MALDI-TOF serum protein profiles using discrete wavelet transformation
Authors: Alexandrov Theodore , Decker Jens , Mertens Bart , Deelder Andre M. , Tollenaar Rob A. E. M. , Maass Peter , Thiele Herbert
Published: February 2009

Motivation: Automatic classification of high-resolution mass spectrometry proteomic data has increasing potential in the early diagnosis of cancer. We propose a new procedure of biomarker discovery in serum protein profiles based on: (i) discrete wavelet transformation of the spectra; (ii) selection of discriminative wavelet coefficients by a statistical test and (iii) building and evaluating a support vector machine classifier by double cross-validation with attention to the generalizability of the results. In addition to the evaluation results (total recognition rate, sensitivity and specificity), the procedure provides the biomarker patterns, i.e. the parts of spectra which discriminate cancer and control individuals. The evaluation was performed on matrix-assisted laser desorption ionization time-of-flight (MALDI-TOF) serum protein profiles of 66 colorectal cancer patients and 50 controls.

Results: Our procedure provided a high recognition rate (97.3%), sensitivity (98.4%) and specificity (95.8%). The extracted biomarker patterns mostly represent the peaks expressing mean differences between the cancer and control spectra. However, we showed that the discriminative power of a peak is not simply expressed by its mean height and cannot be derived by comparison of the mean spectra. The obtained classifiers have high generalization power as measured by the number of support vectors. This prevents overfitting and contributes to the reproducibility of the results, which is required to find biomarkers differentiating cancer patients from healthy individuals.

Availability: The data and scripts used in this study are available at http://www.math.uni-bremen.de/~theodore/MALDIDWT.

Contact:  theodore@math.uni-bremen.de

Supplementary information:  Supplementary data are available at Bioinformatics online.