bluuebunny/crossref_metadata_2025 huggingface dataset:
Aszites und Makrohämaturie nach Bagatelltrauma unter Alkoholeinfluss
Authors: Bürkner  , Neuhaus  , Schöb
Published: February 2010

Isolierte Blasenrupturen nach Bagatelltraumen stellen eine seltene abdominelle Verletzung dar. Sowohl die Diagnostik als auch die Therapie fordern Notfallmediziner und Chirurgen heraus. Dieser Fall berichtet von einem 46-jährigen Patienten, welcher nach einem Sturz unter Alkoholeinfluss mit einer Commotio cerebri hospitalisiert wurde. Im Ultraschall des Abdomens sowie konsekutiv in der CT des Abdomens zeigte sich freie Flüssigkeit. Zudem konnte eine Makrohämaturie nachgewiesen werden. In der retrograden Zystographie kam ein intraperitonealer Kontrastmittelaustritt zur Darstellung. Die Blasenruptur wurde laparoskopisch bestätigt und zweireihig intrakorporal übernäht. Postoperativ zeigte der Patient einen komplikationslosen Verlauf mit Entlassung am vierten postoperativen Tag und korrekter retrograder Zystographie 10 Tage postoperativ sowie konsekutiver Entfernung des Blasenkatheters.
Local sorting, bend curvature, and particle mobility in meandering gravel bed rivers
Authors: Clayton Jordan A.
Published: February 2010

Hydraulic, grain scale sorting of mixed bed sediment influences the mobility of grains in discrete areas of river channels. To assess this effect, local values of surface grain size sorting were compared with measurements of bed load at corresponding locations in a bend of the Colorado River in Rocky Mountain National Park (RMNP), and the distribution of local Shields stress through the reach was derived from a two‐dimensional flow model. With decreasing degrees of local sorting, the relative mobility of the fine‐ and coarse‐size fractions of the load appeared to decrease and increase, respectively. Furthermore, back‐calculated critical Shields stress values for sediment entrainment decreased with values of local sorting, particularly for the upstream portion of the reach where particles were more poorly sorted and coarse grains had higher relative exposure. To evaluate the pervasiveness of these and other patterns of sorting in gravel rivers, detailed field measurements of channel topography and surface grain size (317 pebble counts) were obtained for seven additional reaches of differing curvature (radius of curvature/width from 1 to 28) near the headwaters of the Colorado and Fall rivers in RMNP. Moderately curved and tight bends (radius of curvature/width ≤ 7) were significantly better sorted than comparatively straight reaches. Values of local sorting decreased with distance downstream for the majority of curved channels, reflecting a reduction in the standard deviation of surface grain sizes toward the lower end of the reach; this effect increased slightly with bend sharpness.
Permafrost evidence for severe winter cooling during the Younger Dryas in northern Alaska
Authors: Meyer Hanno , Schirrmeister Lutz , Yoshikawa Kenji , Opel Thomas , Wetterich Sebastian , Hubberten Hans‐W. , Brown Jerry
Published: February 2010

The Younger Dryas cold event, a rapid reversion to glacial climate conditions at the Pleistocene‐Holocene transition, has generally been attributed to the release of meltwater from the Laurentide Ice Sheet to the North Atlantic or Arctic oceans. The reaction of the North Pacific region to this “shutdown” of the thermohaline circulation in the North Atlantic during Younger Dryas is little understood. In this paper, we present the first radiocarbon‐dated centennial‐scale stable water isotope record from permafrost in northern Alaska. This Late Glacial winter climate reconstruction from Barrow ice wedges demonstrates the existence of a Younger Dryas cold event, formerly believed to be reduced or absent in this area. Our stable isotope data display a gradual change of the atmospheric moisture source conditions during the Younger Dryas, likely associated with the successive opening of the Bering Strait.
Fabric induced weakness of tectonic faults
Authors: Niemeijer André , Marone Chris , Elsworth Derek
Published: February 2010

Mature fault zones appear to be weaker than predicted by both theory and experiment. One explanation involves the presence of weak minerals, such as talc. However, talc is only a minor constituent of most fault zones and thus the question arises: what proportion of a weak mineral is needed to satisfy weak fault models? Existing studies of fault gouges indicate that >30% of the weak phase is necessary to weaken faults ‐ a proportion not supported by observations. Here we demonstrate that weakening of fault gouges can be accomplished by as little as 4 wt% talc, provided the talc forms a critically‐aligned, through‐going layer. Observations of foliated fault rocks in mature, large‐offset faults suggest they are produced as a consequence of ongoing fault displacement and thus our observations may provide a common explanation for weakness of mature faults.
Equatorial ionosphere bottom‐type spread F observed by OI 630.0 nm airglow imaging
Authors: Takahashi H. , Abdu M. A. , Taylor M. J. , Pautet P.‐D. , de Paula E. , Kherani E. A. , Medeiros A. F. , Wrasse C. M. , Batista I. S. , Sobral J. H. A. , Gobbi D. , Arruda D. , Paulino I. , Vadas S. , Fritts D.
Published: February 2010

Bottom‐type spread F events were observed in the south American equatorial region by a VHF coherent radar and an ionosonde at São Luís (2.5°S, 44.3°W), an ionosonde at Fortaleza (3.9°S, 38.4° W) and an airglow OI 630.0 nm imager at Cariri (7.4°S, 36.5°W) and Brasilia (14.8°S, 47.6°W). In the evening of September 30, 2005, a long duration (∼70 minutes) bottom side scattering layer, confined in a narrow height region, was observed. At the same time all‐sky imager observed sinusoidal intensity depletions in the zonal plane extending more than 1500 km and elongated along the magnetic meridian. No strong spread F structures developed during the period. Subsequently well developed plasma bubbles were observed. This suggests that the observed bottom‐type spread F is an initial phase of the plasma bubbles. We report, for the first time, longitudinal and latitudinal extension of the bottom‐type spread F as diagnosed by optical imagers.
Compaction‐induced stress variations with depth in an active anticline: Northern Apennines, Italy
Authors: Carminati Eugenio , Scrocca Davide , Doglioni Carlo
Published: February 2010

It is shown that the stress field can vary with depth, even within a homogeneous tectonic setting, as documented for the active Mirandola fault‐related fold along the buried front of the northern Apennines. Analyses of borehole breakouts and other well data, integrated with seismological information and field evidence, show that extension perpendicular to the fold axis, above approximately 1200 m, changes to a strike‐slip stress field and finally to compression near the main detachment at depth. Similar along‐depth strain variations recognized in non‐active anticlines are usually explained by invoking tangential longitudinal strain folding (i.e., stretching above and shortening below a neutral surface) or gravitational instabilities. However, in this study, we propose that differential compaction may play a significant and generally overlooked role. With the aid of numerical modeling, it is shown that where fold limbs are onlapped by highly compactable deposits (as in the Mirandola area), differential compaction induces stretching at shallow (<1–2 km) depths. The amount of stretching is a function of the shape of the fold and of the thickness of the syn‐tectonic sediments. We conclude that in the Mirandola case study, the stress variations observed with depth are the result of a combination of a regional compression at depth and local tension driven by differential compaction of growth strata on the limbs of the anticline with respect to its crest.
Nondimensional control parameters governing the behavior of one‐dimensional fault slip: Effects of shear heating, inelastic pore creation, and fluid flow
Authors: Suzuki Takehito , Yamashita Teruo
Published: February 2010

We theoretically study the dynamic slip of a one‐dimensional fault considering thermoporoelastic effects including shear heating, fluid flow, and inelastic pore creation. We find that the qualitative nature of system behavior can be understood in terms of three nondimensional parameters: Su, S′u, and P*0. The parameter Su represents the relative dominance of the effect of inelastic pore creation on the fluid pressure change over that of shear heating, while S′u is associated with the dominance of the fluid flow effect over the effect of shear heating. The parameter P*0 denotes the initial fluid pressure. We observe the slip‐weakening and slip‐strengthening behaviors in the ranges Su < −P*0 and Su > −P*0, respectively, irrespective of the value of S′u. We can understand both fast and slow fault slips comprehensively on the basis of our model. Ordinary high‐speed fault slip can be simulated with Su slightly larger than −P*0, S′u near the lower limit, and σs0 ∼ 100 MPa. We need the conditions of Su ≫ −P*0, sufficiently large values for S′u, and sufficiently smaller values for σs0 to model much slower fault slip. Our present study also provides a model for the mechanism of negligible frictional heating on the San Andreas fault. We actually found that the temperature rise on the fault is negligibly low in the range of slip strengthening if the values of σs0 and S′u are small enough and/or the value of Su is significantly larger than a threshold.
Modeling brine and nutrient dynamics in Antarctic sea ice: The case of dissolved silica
Authors: Vancoppenolle Martin , Goosse Hugues , de Montety Anne , Fichefet Thierry , Tremblay Bruno , Tison Jean‐Louis
Published: February 2010

Sea ice ecosystems are characterized by microalgae living in brine inclusions. The growth rate of ice algae depends on light and nutrient supply. Here, the interactions between nutrients and brine dynamics under the influence of algae are investigated using a one‐dimensional model. The model includes snow and ice thermodynamics with brine physics and an idealized sea ice biological component, characterized by one nutrient, namely, dissolved silica (DSi). In the model, DSi follows brine motion and is consumed by ice algae. Depending on physical ice characteristics, the brine flow is either advective, diffusive, or turbulent. The vertical profiles of ice salinity and DSi concentration are solutions of advection‐diffusion equations. The model is configured to simulate the typical thermodynamic regimes of first‐year Antarctic pack ice. The simulated vertical profiles of salinity and DSi qualitatively reproduce observations. Analysis of results highlights the role of convection in the lowermost 5–10 cm of ice. Convection mixes saline, nutrient‐poor brine with comparatively fresh, nutrient‐rich seawater. This implies a rejection of salt to the ocean and a flux of DSi to the ice. In the presence of growing algae, the simulated ocean‐to‐ice DSi flux increases by 0–115% compared to an abiotic situation. In turn, primary production and brine convection act in synergy to form a nutrient pump. The other important processes are the flooding of the surface by seawater and the percolation of meltwater. The former refills nutrients near the ice surface in spring. The latter, if present, tends to expell nutrients from the ice in summer.
McNutt Outlines Priorities for the U.S. Geological Survey
Authors: Showstack Randy
Published: February 2010

For Marcia McNutt, the new director of the U.S. Geological Survey (USGS) and science advisor to the secretary of the interior, the clock is ticking. “Everyone feels that we have perhaps 3 years in which a very ambitious agenda needs to be accomplished,” McNutt told Eos in a recent exclusive interview. “We want to make sure by the end of [U.S. President Obama's] first term we have got significant accomplishments on issues such as climate change, environment, and energy, and other things that are important to the president.”

“Everything is on a fast track to move quickly,” she said. “Everything had to be done yesterday, if not last week.” While the political process often requires immediate scientific information, the scientific process can take a bit longer, McNutt said, noting that it is fortunate research at the USGS has persisted in many areas.
Analysis of multistate models for electromigration failure
Authors: Dwyer V. M.
Published: February 2010

The application of a multistate Markov chain is considered as a model of electromigration interconnect degradation and eventual failure. Such a model has already been used [Tan et al., J. Appl. Phys. 102, 103703 (2007)], maintaining that, in general, it leads to a failure distribution described by a gamma mixture, and that as a result, this type of distribution (rather than a lognormal) should be used as a prior in any Bayesian mode fitting and subsequent reliability budgeting. Although it appears that the model is able to produce reasonably realistic resistance curves R(t), we are unable to find any evidence that the failure distribution is a simple gamma mixture except under contrived conditions. The distributions generated are largely sums of exponentials (phase-type distributions), convolutions of gamma distributions with different scales, or roughly normal. We note also some inconsistencies in the derivation of the gamma mixture in the work cited above and conclude that, as it stands, the Markov chain model is probably unsuitable for electromigration modeling and a change from lognormal to gamma mixture distribution generally cannot be justified in this way. A hidden Markov model, which describes the interconnect behavior at time t rather than its resistance, in terms of generally observed physical processes such as void nucleating, slitlike growth (where the growth is slow and steady), transverse growth, current shunting (where the resistance jumps in value), etc., seems a more likely prospect, but treating failure in such a manner would still require significant justification.
Pinning induced by inter-domain wall interactions in planar magnetic nanowires
Authors: Hayward T. J. , Bryan M. T. , Fry P. W. , Fundi P. M. , Gibbs M. R. J. , Im M.-Y. , Fischer P. , Allwood D. A.
Published: February 2010

We have investigated pinning potentials created by inter-domain wall magnetostatic interactions in planar magnetic nanowires. We show that these potentials can take the form of an energy barrier or an energy well depending on the walls’ relative monopole moments, and that the applied magnetic fields required to overcome these potentials are significant. Both transverse and vortex wall pairs are investigated and it is found that transverse walls interact more strongly due to dipolar coupling between their magnetization structures. Simple analytical models which allow the effects of inter-domain wall interactions to be estimated are also presented.
Method and basis set dependence of anharmonic ground state nuclear wave functions and zero-point energies: Application to SSSH
Authors: Kolmann Stephen J. , Jordan Meredith J. T.
Published: February 2010

One of the largest remaining errors in thermochemical calculations is the determination of the zero-point energy (ZPE). The fully coupled, anharmonic ZPE and ground state nuclear wave function of the SSSH radical are calculated using quantum diffusion Monte Carlo on interpolated potential energy surfaces (PESs) constructed using a variety of method and basis set combinations. The ZPE of SSSH, which is approximately 29 kJ mol−1 at the CCSD(T)/6-31G∗ level of theory, has a 4 kJ mol−1 dependence on the treatment of electron correlation. The anharmonic ZPEs are consistently 0.3 kJ mol−1 lower in energy than the harmonic ZPEs calculated at the Hartree–Fock and MP2 levels of theory, and 0.7 kJ mol−1 lower in energy at the CCSD(T)/6-31G∗ level of theory. Ideally, for sub-kJ mol−1 thermochemical accuracy, ZPEs should be calculated using correlated methods with as big a basis set as practicable. The ground state nuclear wave function of SSSH also has significant method and basis set dependence. The analysis of the nuclear wave function indicates that SSSH is localized to a single symmetry equivalent global minimum, despite having sufficient ZPE to be delocalized over both minima. As part of this work, modifications to the interpolated PES construction scheme of Collins and co-workers are presented.
Phase compatibility and thermoelectric properties of compounds in the Sr–Ca–Co–O system
Authors: Wong-Ng W. , Liu G. , Martin J. , Thomas E. L. , Lowhorn N. , Kaduk J. A.
Published: February 2010

Two low-dimensional cobaltite series in the Sr–Ca–Co–O system have been investigated for their solid solution limit, structure, and compatibility phase relationships (850 °C in air). Thermoelectric properties have been measured for selected members of these solid solutions. In (Ca,Sr)3Co4O9, which has a misfit layered structure, Sr was found to substitute in the Ca site to a limit of (Ca0.8Sr0.2)3Co4O9. Compounds in the homologous series, An+2ConCo′O3n+3 [where A=Sr, Ca, (Ca,Sr), or (Sr,Ca)], consist of one-dimensional parallel Co2O66− chains that are built from successive alternating face-sharing CoO6 trigonal prisms and “n” units of CoO6 octahedra along the hexagonal c-axis. In the Can+2ConCo′O3n+3 series, only the n=1 phase (Ca3Co2O6) could be prepared under the present synthesis conditions. Sr substitutes in the Ca site of Ca3Co2O6 to a limit of (Ca0.9Sr0.1)3Co2O6. In the Srn+2ConCo′O3n+3 series, Ca substitutes in the Sr site of the n=2, 3, and 4 members to a limit of (Sr0.7Ca0.3)4Co3O9, (Sr0.67Ca0.33)5Co4O12, and (Sr0.725Ca0.275)6Co5O15, respectively. While the members of the Can+2ConCo′O3n+3 and Srn+2ConCo′O3n+3 series have reasonably high Seebeck coefficients and relatively low thermal conductivity, the electrical conductivity needs to be increased in order to achieve high ZT values.
Reactive dc magnetron sputtering of (GeOx–SiO2) superlattices for Ge nanocrystal formation
Authors: Zschintzsch M. , Jeutter N. M. , von Borany J. , Krause M. , Mücklich A.
Published: February 2010

The motivation of this work is the tailored growth of Ge nanocrystals for photovoltaic applications. The use of superlattices provides a reliable method to control the Ge nanocrystal size after phase separation. In this paper, we report on the deposition of (GeOx–SiO2) superlattices via reactive dc magnetron sputtering and the self-ordered Ge nanocrystal formation during subsequent annealing. Attention is directed mainly to define proper deposition conditions for tuning the GeOx composition between elemental Ge (x=0) and GeO2 (x=2) by the variation in the deposition temperature and the oxygen partial pressure. A convenient process window has been found which allows sequential GeOx–SiO2 deposition without changing the oxygen partial pressure during deposition. The phase separation and Ge nanocrystal formation after subsequent annealing were investigated with in situ x-ray scattering, Raman spectroscopy, and electron microscopy. By these methods the existence of 2–5 nm Ge nanocrystals at annealing temperatures of 600–750 °C has been confirmed which is within the superlattice stability range. The technique used allows the fabrication of superlattice stacks with very smooth interfaces (roughness<1 nm); thus the Ge nanocrystal layers could be separated by very thin SiO2 films (d<3 nm) which offers interesting possibilities for charge transport via direct tunneling.
An automated algorithm for the generation of dynamically reconstructed trajectories
Authors: Komalapriya C. , Romano M. C. , Thiel M. , Marwan N. , Kurths J. , Kiss I. Z. , Hudson J. L.
Published: February 2010

The lack of long enough data sets is a major problem in the study of many real world systems. As it has been recently shown [C. Komalapriya, M. Thiel, M. C. Romano, N. Marwan, U. Schwarz, and J. Kurths, Phys. Rev. E 78, 066217 (2008)], this problem can be overcome in the case of ergodic systems if an ensemble of short trajectories is available, from which dynamically reconstructed trajectories can be generated. However, this method has some disadvantages which hinder its applicability, such as the need for estimation of optimal parameters. Here, we propose a substantially improved algorithm that overcomes the problems encountered by the former one, allowing its automatic application. Furthermore, we show that the new algorithm not only reproduces the short term but also the long term dynamics of the system under study, in contrast to the former algorithm. To exemplify the potential of the new algorithm, we apply it to experimental data from electrochemical oscillators and also to analyze the well-known problem of transient chaotic trajectories.
A new flexible scatterometer for critical dimension metrology
Authors: Wurm Matthias , Pilarski Frank , Bodermann Bernd
Published: February 2010

At Physikalisch-Technische Bundesanstalt, the National Metrology Institute of Germany, a new type of deep ultraviolet scatterometer has been developed and set up. The concept of the system is very variable and versatile, so that many different types of measurements, e.g., classical scatterometry, ellipsometric scatterometry, polarization-dependent reflectometry, and ellipsometry can be performed. The main application is the characterization of linewidth/critical dimension (CD), grating period (pitch), and edge profile of periodically nanostructured surfaces mainly, but not only, on photomasks. Different operation wavelength between 840 and 193 nm can be used, giving also access to a variety of different at-wavelength metrology connected with state-of-the-art photolithography. It allows to adapt and to vary the measurand and measurement geometry to optimize the sensitivity and the unambiguity for the measurement problem. In this paper the concept, design, and performance of the system is described in detail. First measurement examples are shown and current and future applications are discussed.
Design and development of a radio frequency quadrupole linac postaccelerator for the Variable Energy Cyclotron Center rare ion beam project
Authors: Dechoudhury S. , Naik V. , Mondal M. , Chatterjee A. , Pandey H. K. , Mandi T. K. , Bandyopadhyay A. , Karmakar P. , Bhattacharjee S. , Chouhan P. S. , Ali S. , Srivastava S. C. L. , Chakrabarti A.
Published: February 2010

A four-rod type heavy-ion radio frequency quadrupole (RFQ) linac has been designed, constructed, and tested for the rare ion beam (RIB) facility project at VECC. Designed for cw operation, this RFQ is the first postaccelerator in the RIB beam line. It will accelerate A/q≤14 heavy ions coming from the ion source to the energy of around 100 keV/u for subsequent acceleration in a number of Interdigital H-Linac. Operating at a resonance frequency of 37.83 MHz, maximum intervane voltage of around 54 kV will be needed to achieve the final energy over a vane length of 3.12 m for a power loss of 35 kW. In the first beam tests, transmission efficiency of about 90% was measured at the QQ focus after the RFQ for O5+ beam. In this article the design of the RFQ including the effect of vane modulation on the rf characteristics and results of beam tests will be presented.
Two-dimensional symmetric and antisymmetric generalizations of exponential and cosine functions
Authors: Hrivnák Jiří , Patera Jiří
Published: February 2010

The properties of the four families of the recently introduced special functions of two real variables, denoted here by E± and cos±, are studied. The superscripts + and − refer to the symmetric and antisymmetric functions, respectively. The functions are considered in all details required for their exploitation in Fourier expansions of digital data, sampled on square grids of any density, and for general position of the grid in the real plane relative to the lattice defined by the underlying group theory. The quality of continuous interpolation, resulting from the discrete expansions, is studied, exemplified, and compared for some model functions.
Multifunctional integrating sphere setup for luminous flux measurements of light emitting diodes
Authors: Poikonen Tuomas , Manninen Pasi , Kärhä Petri , Ikonen Erkki
Published: February 2010

A multifunctional setup based on the absolute integrating sphere method for measuring luminous flux of light emitting diodes (LEDs) is presented. The total luminous flux in 2π and 4π geometries and partial luminous flux with variable cone angle can be measured with the same custom-made integrating sphere. The number and area of ports and baffles of the sphere was minimized. The sphere has three ports: a main port, a detector port, and an auxiliary port, located in the same hemisphere. The other hemisphere is free of ports. The main port is used for the calibration of the sphere as well as for the LED under test. Only one absolute calibration of the integrating sphere photometer is needed for measuring LEDs in all three geometries. The spatial nonuniformity correction is needed only for LEDs with low directivity or having significant minor beams. The expanded uncertainty (k=2) for the measurement setup varies between 1.2% and 4.6% depending on the measurement geometry, color, and the angular spread of the LED light beam. A complete calibration procedure of the constructed integrating sphere photometer is presented as well as comparison measurements with a goniophotometer.
Asymptotic independence of the extreme eigenvalues of Gaussian unitary ensemble
Authors: Bornemann Folkmar
Published: February 2010

We give a short, operator-theoretic proof of the asymptotic independence (including a first correction term) of the minimal and maximal eigenvalue of the n×n Gaussian unitary ensemble in the large matrix limit n→∞. This is done by representing the joint probability distribution of the extreme eigenvalues as the Fredholm determinant of an operator matrix that asymptotically becomes diagonal. As a corollary, we get that the correlation of the extreme eigenvalues asymptotically behaves like n−2/3/4σ2, where σ2 denotes the variance of the Tracy–Widom distribution. While we conjecture that the extreme eigenvalues are asymptotically independent for Wigner random Hermitian matrix ensembles, in general, the actual constant in the asymptotic behavior of the correlation turns out to be specific and can thus be used to distinguish the Gaussian unitary ensemble statistically from certain other Wigner ensembles.
Analysis of breakdown characteristics in high-k dielectrics under electrostatic discharge impulse stress
Authors: Chen Chun-Heng , Liao Ming Han , Chiu Fu-Chien , Hwang Huey-Liang
Published: February 2010

Transmission line pulse measurements were used to investigate the reliability of the HfO2 dielectric under an electrostatic discharge event. Time-dependent dielectric breakdown of the gate oxide was characterized down to the microsecond time regime. The positive oxide-trapped charges Qot+ were observed beyond a certain electric field and the corresponding centroid evolution was examined. In the high-field stress regime, the field acceleration parameter of the HfO2 dielectric is smaller than that of the silicon oxynitride. We also demonstrated this phenomenon can be attributed to the stronger phonon-assisted tunneling process in the high-k dielectrics.
Hyperfine interaction and Stark effect in the b Π3-X ∑1+(,) band of copper monofluoride, CuF
Authors: Wang Fang , Steimle Timothy C.
Published: February 2010

The low-rotational levels of the b Π3-X ∑1+(0,0) band of copper monofluoride, CuF, were recorded field free and in the presence of a static electric field. The field-free spectrum was analyzed to produce a refined set of fine and hyperfine parameters for the b Π3(v=0) state. The permanent electric dipole moment, μ, for the b Π3(v=0) and X ∑1+(v=0) states were determined to be 2.36(2) and 5.26(2) D, respectively, from the analysis of the observed Stark shifts. The experimental μ values are compared to theoretical predictions. The change in μ upon excitation and the hyperfine parameters are discussed in terms of the proposed electronic configuration for the b Π3 and X ∑1+ states. The optical Stark spectroscopy of the A Π23/2-X ∑2+(0,0) subband of YO was also recorded and analyzed to precisely calibrate the electric field strength. The determined μ values are 3.714(5) and 4.542(40) D for the A Π23/2(v=0) and X ∑2+(v=0) states, respectively.
Hydrogen and inert species in solid phase epitaxy
Authors: Lieten R. R. , Degroote S. , Clemente F. , Leys M. , Borghs G.
Published: February 2010

The incorporation of hydrogen during deposition of amorphous germanium can influence solid phase epitaxy in many ways. We show that Ge–H bonds are not important during the crystallization process. However, atomic hydrogen is important during deposition to obtain a highly disordered layer. We have found that highly disordered layers can also be obtained when using a beam of inert gas species during ultrahigh vacuum deposition. These inert species effectively increase the disorder of the layer by limiting the surface mobility of adsorbed germanium atoms. In this way subsequent solid phase epitaxy can be improved significantly.
Electron proportional gas counter for linear and elliptical Mössbauer polarimetry
Authors: Tanczikó F. , Sajti Sz. , Deák L. , Merkel D. G. , Endrőczi G. , Nagy D. L. , Bottyán L. , Olszewski W. , Szymański K.
Published: February 2010

Design, characterization, and selected applications of a novel electron detector dedicated to conventional perpendicular- and low-angle-incidence conversion electron Mössbauer spectroscopy are presented. The setup is suitable for varying the incident angle and external magnetic fields on Mössbauer source and absorber. Test experiments were performed on α-F57e films using a conventional single-line C57o(Rh) and magnetically split, C57o(α-Fe) Mössbauer sources. The integral “blackness effect” in conversion-electron Mössbauer spectra of F57e isotope-enriched absorbers is demonstrated and shown to be pronounced at shallow angles of incidence. In order to determine the alignment and sign of the hyperfine field in an isotope-enriched absorber, the blackness effect is accounted for in a semiempirical way by using single-line source/absorber experimental relative intensities determined independently. This method works with high accuracy for linear polarimetry; however it is only a rough approximation in the case of nearly circular polarimetry.
Thickness dependent absorption spectra in conjugated polymers: Morphology or interference?
Authors: Gaudin Olivier P. M. , Samuel Ifor D. W. , Amriou Samia , Burn Paul L.
Published: February 2010

The thickness dependence of the absorption spectrum of spin-coated films of poly[2-(2′-ethylhexyloxy)-5-methoxy-1,4-phenylenevinylene] has been studied using reflectivity and variable angle spectroscopic ellipsometry measurements. It is found that, for films with thicknesses in the range of 18–178 nm, a single set of optical constants is sufficient to simulate accurately all the experimental data used, including the absorption spectra, independently of the film thickness or the processing conditions. Thus, the observed changes in the absorption spectrum with thickness can be fully accounted for by reflectivity and interference effects alone without the need to invoke morphology differences between films.
Growth and characterization of In-polar and N-polar InAlN by metal organic chemical vapor deposition
Authors: Brown David F. , Keller Stacia , Mates Thomas E. , Speck James S. , DenBaars Steven P. , Mishra Umesh K.
Published: February 2010

In x Al 1 − x N layers, with 0.09≤x≤0.23, were grown on GaN on both the In-polar and N-polar orientations by metal organic chemical vapor deposition. The impact of growth conditions, including temperature and the group-III flow rates, on the surface morphology and indium mole fraction was investigated. In-polar layers had a smooth surface morphology characterized by mounds which decreased in size with increasing supersaturation during growth. Smooth N-polar InAlN was achieved through the use of vicinal sapphire substrates with misorientation angles of 3°–5° toward ⟨101¯0⟩GaN, and a trend of an increase in step bunching with decreasing supersaturation was observed for N-polar InAlN layers. The indium incorporation increased with decreasing growth temperature and increasing growth rate for both In-polar and N-polar layers. The indium incorporation was similar for both orientations on samples which were coloaded in our reactor.
High speed infrared camera diagnostic for heat flux measurement in NSTX
Authors: Ahn J.-W. , Maingi R. , Mastrovito D. , Roquemore A. L.
Published: February 2010

A new high speed infrared camera has been successfully implemented and produced first set of heat flux measurements on the lower divertor tiles in the NSTX tokamak. High spatial and temporal resolutions, 6.4 mm and 1.6–6.3 kHz, respectively, enable us to investigate detailed structure of heat flux deposition pattern caused by transient events such as edge localized modes. A comparison of the data with a slow infrared camera viewing the same region of interest shows good agreement between the two independent measurements. Data analysis for various plasma conditions is in progress.
Wide-bandgap Zn2GeO4 nanowire networks as efficient ultraviolet photodetectors with fast response and recovery time
Authors: Yan Chaoyi , Singh Nandan , Lee Pooi See
Published: February 2010

Ultraviolet (UV) photodetectors based on ternary Zn2GeO4 nanowire (NW) networks are demonstrated. The devices show fast response and recovery time, which is attributed to the unique NW-NW junction barrier dominated conductance for network devices. The UV-light induced barrier height modulation is much faster than the oxygen adsorption/desorption processes. The wide-band gap Zn2GeO4 NWs also exhibit high wavelength selectivity for deep UV detection. We demonstrate that ternary oxide NW-networks are ideal building blocks for nanoscale photodetectors with superior performance and facile fabrication processes.
Study of defect-dipoles in an epitaxial ferroelectric thin film
Authors: Folkman C. M. , Baek S. H. , Nelson C. T. , Jang H. W. , Tybell T. , Pan X. Q. , Eom C. B.
Published: February 2010

We have analyzed the defect contributions to the in-plane polarization switching of epitaxial (001) BiFeO3 thin films on (110) TbScO3 substrates. Interdigitated electrodes were patterned with respect to ferroelectric stripe domains in the BiFeO3 film. Polarization measurements exhibited a clear double hysteresis caused by the presence of a static defect field (∼40 kV/cm); the field resulted from ordered defect-dipoles initially aligned to the spontaneous polarization. By monitoring the defect field, both realignment and disassociation of the defect-dipoles were demonstrated. These results establish the arrangement of defect-dipoles in epitaxial ferroelectric thin films, guiding technologies and opening an avenue for defect related studies.
Carrier transport simulation in a model liquid crystalline system with the biaxial Gay–Berne potential
Authors: Goto Masanao , Takezoe Hideo , Ishikawa Ken
Published: February 2010

In this paper, we performed carrier transport simulation to understand the unusual temperature dependence of the carrier mobility observed in nematic liquid crystals. For this purpose, we made a model liquid crystalline system consisting of biaxial Gay–Berne particles, and then we simulated hopping transport between these particles. The hopping rate was formulated suitably for the biaxial Gay–Berne particles based on the investigation of the electronic overlaps between actual aromatic molecules. The carrier transport simulation was performed by master equation method on the model system prepared by N-P-T ensemble Monte Carlo simulation. We reproduced gradual mobility increase in the nematic phase as a result of the change in the short range molecular order.
The longitudinal optic-like mode in molten alkali halides: A molecular dynamics approximation to inelastic x-ray scattering experiments
Authors: Alcaraz O. , Trullàs J.
Published: February 2010

The contribution of the long-wavelength fluctuations in the particle number, mass, and charge densities to the inelastic x-ray scattering dynamical structure factor for molten NaI and other molten alkali halides is accurately analyzed in the high frequencies region of the longitudinal optic-like mode. Molecular dynamics simulation results at low wave numbers are reported for the time correlations between the density components in the reciprocal space, namely, the corresponding intermediate scattering functions, and their spectra, namely, the dynamical structure factors. The time correlations between the longitudinal currents and their spectra are also reported. The importance of cross correlations is discussed. Moreover, the role played by the collective behavior of the two ionic species is also investigated. It is concluded that the longitudinal optic-like mode in molten alkali halides is unlikely to be detected by inelastic x-ray scattering experiments.
Circumstantial evidence in support of bivelocity hydrodynamic theory for mixtures
Authors: Brenner Howard
Published: February 2010

Based upon findings with respect to the viability of the expression jv=−ρDv∇v̂ hypothesized to represent the constitutive equation for the diffusive volume flux in ideal binary mixtures (ρ=mass density, v̂=1/ρ=specific volume, and Dv=volume diffusion coefficient), implicit evidence is offered in support of the recently developed theory of bivelocity continuum hydrodynamics for mixtures. Present findings for the case of mixtures add to existing evidence already available for the single-component case, thus supporting the viability of bivelocity hydrodynamic theory in general.
Electron velocity shear driven instability in relativistic regime
Authors: Sundar Sita , Das Amita
Published: February 2010

The electron magnetohydrodynamics model has been generalized to incorporate relativistic effects. The model is then employed to study the instability associated with sheared electron velocity flow in the relativistic regime. The instability has features similar to the conventional velocity shear driven Kelvin–Helmholtz-like mode [A. Das and P. Kaw, Phys. Plasmas 8, 4518 (2001)] in the weakly relativistic regime. However, in the strongly relativistic regime the instability shows certain distinct characteristics. The threshold value of the wave number is found to be considerably higher than the inverse shear width of the equilibrium velocity profile in this regime. Thus, the unstable domain of the wave-number space is considerably wider in this case. Also the mode does not remain purely growing but acquires a real frequency even for an antisymmetric velocity profile. These features of the mode have been understood by realizing that in the strongly relativistic regime the relativistic mass factor γ0 for the equilibrium has much sharper variations than that of the velocity profile.
Optical gain improvement in type-II InGaN/GaNSb/GaN quantum well structures composed of InGaN/and GaNSb layers
Authors: Park Seoung-Hwan , Ahn Doyeol , Koo Bun-Hei , Oh Jae-Eung
Published: February 2010

Optical gain characteristics of type-II InGaN/GaNSb quantum well (QW) structure are investigated by using the multiband effective mass theory. These results are compared with those of conventional InGaN/GaN QW structures. The transition wavelength rapidly increases with increasing the Sb composition in GaNSb layer while it is less sensitive to the In composition in InGaN layer. Hence, longer wavelength QW structures with a relatively lower In composition can be easily obtained by controlling Sb composition, compared to the conventional type-I InGaN/GaN QW structures. The optical gain and the differential gain (dg/dn) of a type-II QW structure are shown to be much larger than that of a conventional QW structure in an investigated range of carrier densities. This is due to the reduction in the effective well width, in addition to the increase in the optical matrix element.
The impact of piezoelectric polarization and nonradiative recombination on the performance of (0001) face GaN/InGaN photovoltaic devices
Authors: Wierer J. J. , Fischer A. J. , Koleske D. D.
Published: February 2010

The impact of piezoelectric polarization and nonradiative recombination on the short-circuit current densities (Jsc) of (0001) face GaN/InGaN photovoltaic devices is demonstrated. P-i-n diodes consisting of 170 nm thick intrinsic In0.09Ga0.91N layers sandwiched by GaN layers exhibit low Jsc∼40 μA/cm2. The piezoelectric polarization at the GaN/InGaN heterointerfaces creates drift currents opposite in direction needed for efficient carrier collection. Also, nonradiative recombination centers produce short carrier lifetimes, limiting Jsc. Alternative structures with intrinsic InGaN layers sandwiched by n-type InGaN or graded InyGa1−yN (y=0–0.09) layer and a p-type In0.015Ga0.985N layer have favorable potentials, longer carrier lifetimes, and improve Jsc to ∼0.40 mA/cm2.
Effect of Mg doping in the barrier of InGaN/GaN multiple quantum well on optical power of light-emitting diodes
Authors: Han Sang-Heon , Cho Chu-Young , Lee Sang-Jun , Park Tae-Young , Kim Tae-Hun , Park Seung Hyun , Won Kang Sang , Won Kim Je , Kim Yong Chun , Park Seong-Ju
Published: February 2010

We report on Mg doping in the barrier layers of InGaN/GaN multiple quantum wells (MQWs) and its effect on the properties of light-emitting diodes (LEDs). Mg doping in the barriers of MQWs enhances photoluminescence intensity, thermal stability, and internal quantum efficiency of LEDs. The light output power of LEDs with Mg-doped MQW barriers is higher by 19% and 27% at 20 and 200 mA, respectively, than that of LEDs with undoped MQW barriers. The improvement in output power is attributed to the enhanced hole injection to well layers in MQWs with Mg-doped barriers.
Hollow-core resonator based on out-of-plane two-dimensional photonic band-gap crystal cladding at microwave frequencies
Authors: Humbert Georges , Le Floch Jean-Michel , Mouneyrac David , Férachou Denis , Aubourg Michel , Tobar Michael E. , Cros Dominique , Blondy Jean-Marc
Published: February 2010

We report on the demonstration of a resonator based on electromagnetic field confinement in a hollow-core by implementing an out-of-plane two-dimensional (2D) photonic band-gap (PBG) crystal cladding. In contrast with in-plane 2D PBG crystal devices, the PBG crystal studied here is perpendicular to the propagation axis. A resonator was constructed with silica rods to prove the concept at frequencies around 30 GHz. We show that the technique has the potential to reach quality factors (Q) of 5×105.
Improved crystal quality and performance of GaN-based light-emitting diodes by decreasing the slanted angle of patterned sapphire
Authors: Cheng Ji-Hao , Wu YewChung Sermon , Liao Wei-Chih , Lin Bo-Wen
Published: February 2010

Periodic triangle pyramidal array patterned sapphire substrates (PSSs) with various slanted angles were fabricated by wet etching. It was found beside normal wurtzite GaN, zinc blende GaN was found on the sidewall surfaces of PSS. The crystal quality and performance of PSS-LEDs improved with decrease in slanted angle from 57.4° to 31.6°. This is because most of the growth of GaN was initiated from c-planes. As the growth time increased, GaN epilayers on the bottom c-plane covered these pyramids by lateral growth causing the threading dislocation to bend toward the pyramids.
How many surface plasmons are locally excited on the ridges of metallic lamellar gratings?
Authors: Wang B. , Lalanne P.
Published: February 2010

In contrast to earlier classical studies that analyze the surface Bloch modes supported by metallic gratings composed of slits as collective surface-plasmon-polaritons (SPPs) resonances (or poles) of the entire periodic problem, we study the normalized rate of SPPs that are locally launched on every individual ridge of metallic lamellar gratings. With this “microscopic” description at the unit-cell level, we further explain how these individual SPPs constructively interfere to build up the classical collective resonances. The approach, which combines analytical treatments and fully-vectorial computations, shines new light on an important and classical phenomenon of grating diffraction.
Band offsets of Al2O3/InxGa1−xAs (x=0.53 and 0.75) and the effects of postdeposition annealing
Authors: Nguyen N. V. , Xu M. , Kirillov O. A. , Ye P. D. , Wang C. , Cheung K. , Suehle J. S.
Published: February 2010

Band offsets at the interfaces of InxGa1−xAs/Al2O3/Al where x=0.53 and 0.75 were determined by internal photoemission and spectroscopic ellipsometry. The photoemission energy threshold at the InxGa1−xAs/Al2O3 interface was found to be insensitive to the indium composition but shifted to a lower energy after a postdeposition annealing at high temperatures. Subthreshold electron photoemission was also observed for the annealed sample and was attributed to interfacial layer formation during the annealing process.
Magnetism in Co-doped tris-8-hydroxyquinoline aluminum studied by first-principles calculations
Authors: Wang Fenggong , Pang Zhiyong , Lin Liang , Fang Shaojie , Dai Ying , Han Shenghao
Published: February 2010

The electronic and magnetic properties of Co-doped tris-8-hydroxyquinoline aluminum (Alq3) are studied by first-principles calculations. Our results indicate that the local magnetic moments in doped Alq3 originate from the localized d states of Co atom. Electron transfer takes place from Co atom to Alq3 molecule, which is mainly localized on the quinolate ligand, resulting in formation of bound magnetic polarons. The indirect ferromagnetic exchange interaction between two bound magnetic polarons antialigning with the same magnetic ion promotes the collective magnetism found in recent experiments.
Effect of In incorporated into SbTe on phase change characteristics resulting from changes in electronic structure
Authors: Jang Moon Hyung , Park Seung Jong , Lim Dong Heok , Park Sung Jin , Cho Mann-Ho , Ko Dae-Hong , Heo M. Y. , Sohn Hyun Chul , Kim Sang-Ok
Published: February 2010

The effects of the In content of InSbTe films with various stoichiometries (Sb2Te2.7, In0.5Sb2Te2.9, and In2.6Sb2Te2.9) on phase change characteristics were investigated. With increasing incorporation of In atoms into Sb2Te3, various crystalline phases, i.e., In2Te3, Sb, and In3SbTe2, were observed due to the bond energy between the constituent atoms, while only Sb2Te3 and the Sb2Te2 phases were observed in the case of Sb2Te2.7 and In0.5Sb2Te2.9 films. In addition, the shifts in binding energy of the Sb 3d and In 3d peaks in x-ray photoelectron spectra after the annealing treatment were directly related to the amount of incorporated In. The observed changes in electronic structure suggest that the changes in electrical conductivity and crystalline phase are directly related to the extent of In incorporation.
A contour-mode film bulk acoustic resonator of high quality factor in a liquid environment for biosensing applications
Authors: Xu Wencheng , Choi Seokheun , Chae Junseok
Published: February 2010

This letter reports an acoustic resonator of high quality factors (Qs) operating in liquid media. The film bulk acoustic resonator (FBAR) is made of a ring-shaped piezoelectric aluminum nitride thin film, and is excited in a contour mode. By having a low motional resistance upon coupling with liquids, the contour mode FBAR achieved Qs up to 189, more than 12× over the state-of-the-art FBARs in liquids. The resonator was characterized by an aptamer—thrombin binding pair for a biosensor and showed a mass resolution of 1.78 ng/cm2.
Tunable interfacial properties of epitaxial graphene on metal substrates
Authors: Gao Min , Pan Yi , Zhang Chendong , Hu Hao , Yang Rong , Lu Hongliang , Cai Jinming , Du Shixuan , Liu Feng , Gao H.-J.
Published: February 2010

We report on tuning interfacial properties of epitaxially-grown graphenes with different kinds of metal substrates based on scanning tunneling microscopy experiments and density functional theory calculations. Three kinds of metal substrates, Ni(111), Pt(111), and Ru(0001), show different interactions with the epitaxially grown graphene at the interfaces. The different interfacial interaction making graphene n-type and p-type doped, leads to the polarity change of the thermoelectric property of the graphene/metal systems. These findings may give further insights to the interfacial interactions in the graphene/metal systems and promote the use of graphene-based heterostructures in devices.