bluuebunny/crossref_metadata_2025 huggingface dataset:
Psychisches Befinden, Beschwerden und Belastungen: Ergebnisse einer repräsentativen Studie
Authors: Schmidt Sören , Petermann Franz , Beutel Manfred E. , Brähler Elmar
Published: April 2011

Zusammenfassung. Die Erfassung von Beschwerden und der Befindlichkeit sind wesentlicher Teil eines klinisch-diagnostischen Prozesses. Da Angststörungen und Depressionen in hohem Maße mit verschiedenen psychischen und körperlichen Belastung einhergehen, wurden in dieser Studie primär die prädiktiven Eigenschaften der Beschwerden-Liste (B-LR) und der Befindlichkeits-Skala (Bf-SR) in revidierter Form mittels Regressionsanalysen (linear und hierarchisch) an einer Stichprobe von N = 2504 untersucht. Als abhängiges Kriterium galt die Ausprägung von Angst- und Depressionssymptomen, ermittelt über das Kurzscreening Patient-Health-Questionnaire-4 (PHQ-4). Da vermutet wurde, dass entsprechende Symptome auch einen Einfluss auf die Qualität sozialer Beziehungen des Betroffenen haben und die globale Lebenszufriedenheit beeinflussen, wurden zudem das Quality of Personal Relationships Inventory (QRI) sowie der Fragebogen zur Lebenszufriedenheit (FLZM) eingesetzt. Sowohl B-LR als auch Bf-SR verfügten über alle Altersgruppen und geschlechtsinvariant über hohe prädiktive Eigenschaften. Die Qualität sozialer Beziehung (QRI) eignet sich nicht zur Vorhersage von Angst und Depressionen. Globale Lebenszufriedenheit nimmt in der Altersgruppe 14–74 gegenläufig zum Anstieg von Angst- und Depressionssymptomen signifikant ab, in der Altersgruppe der ⩾ 75-jährigen Männern leistet diese jedoch keinen signifikanten Beitrag zur Varianzaufklärung. Bei den Frauen dieser Altersgruppe geht eine Erhöhung der Lebenszufriedenheit mit der Zunahme von Angst- und Depressionssymptomen einher. Die Ergebnisse lassen den Schluss zu, dass der Einsatz von B-LR und Bf-SR eine gute Informations- und Handlungsbasis für Forschung und klinische Praxis darstellen. Die unterschiedlichen Tendenzen innerhalb der Analysen zwischen Männern und Frauen weisen auf geschlechtsspezifische Verarbeitungsmechanismen hin. In höherem Alter sollte die Ausprägung von Beschwerden Indikator für die Ermittlung weiterer Ressourcen darstellen, um einen positiven Einfluss auf die Lebenszufriedenheit auszuüben.
Late Quaternary slip rate of the southern Elsinore fault, Southern California: Dating offset alluvial fans via 230Th/U on pedogenic carbonate
Authors: Fletcher Kathryn E. K. , Rockwell Thomas K. , Sharp Warren D.
Published: April 2011

To understand how strain is accommodated along the Pacific‐North American plate boundary and to assess the associated seismic hazard, estimates of long‐term (103–105 year) slip rates for strands of the San Andreas fault system are needed. The mean slip rate over the past ∼40 kyr for the southernmost Elsinore fault, one of the principal strands of the San Andreas fault system in Southern California, was determined using offset alluvial fans dated by U‐series on pedogenic carbonate. Two displaced fans, correlated with their source drainages using distinctive gravel‐clast assemblages, define offsets of 60 ± 20 and 83 ± 31 m. Milligram‐size samples of dense carbonate clast‐coatings from fan soils provide 230Th/U‐based ages of 39.1 ± 5.3 and 46.4 ± 5.3 kyr (all errors are 2σ), respectively, for the offset fans. Our results indicate that the Elsinore fault near its southern terminus slipped at a mean rate of 1.6 ± 0.4 mm/yr over the past ∼40 kyr. However, slip associated with the most recent earthquake on the southern Elsinore fault increases northward from the study area, and if this pattern has repeated through time, the peak slip rate on the southern Elsinore fault may significantly exceed our measured rate.
Formation of a metamorphic complex along an obliquely convergent margin: Structural and thermochronological evolution of the Chugach Metamorphic Complex, southern Alaska
Authors: Gasser Deta , Bruand Emilie , Stüwe Kurt , Foster David A. , Schuster Ralf , Fügenschuh Bernhard , Pavlis Terry
Published: April 2011

This study documents the structural and metamorphic evolution of middle to lower crust along an oblique convergent curved continental margin during a time span of ∼60 Myr. Our study documents the importance of variable obliquity during convergence which led to the development of overprinting fabrics and distinct exhumation histories along strike of the margin. We present structural analyses,40Ar/39Ar, Rb/Sr, and zircon fission track ages from middle to lower crust exposed along the southern Alaskan margin in the Chugach Metamorphic Complex. Together with the metamorphic history and additional geochronology from the literature we derive the following tectonic evolution for this area: accretion of sediments during dextrally oblique convergence led to strain‐partitioned D1structures and greenschist‐facies metamorphism prior to circa 55 Ma. At ∼55–51 Ma, a margin‐parallel stretching phase with vertical thinning (D2) affected the margin and led to andalusite‐sillimanite grade metamorphism and the onset of partial melting. A switch back to dextral transpression (D3) shortly after D2led to rapid cooling of the western and central parts of the complex associated with exhumation of parts of the core of the complex until circa 46 Ma. The southeastern part of the complex cooled and exhumed regularly and slowly until circa 5 Ma due to its highly oblique orientation relative to the convergence direction. An increase in cooling and exhumation occurred after circa 5 Ma in the entire southeastern part of the complex, associated with the Neogene collision of the Yakutat terrane.
The Role of authorized generics in the prescription drug marketplace
Authors: Shcherbakova Natalia , Shepherd Marvin , Lawson Kenneth , Richards Kristin
Published: April 2011

Authorized generics continue to be a controversial phenomenon in the contemporary pharmaceutical marketplace. Proponents of authorized generics consider them an additional player in a healthy competitive pharmaceutical market environment, while opponents note that the entry of authorized generics may be considered anticompetitive under certain circumstances. This study investigated the market share dynamics associated with authorized generics and their direct competitors during the crucial period of initial generic(s) entry. At the end of the 12 months of generic presence, market shares for authorized generics launched with the 180-day marketing exclusivity of an independent generic in the cases of Zocor®, Proscar® and Norvasc® were 37, 52 and 49 per cent, respectively. Meanwhile, market shares for authorized generics launched without the 180-day marketing exclusivity of an independent generic in the cases of Arava® and Ambien® were 21 and 18 per cent, respectively. Authorized generics launched during independent generic 180-day marketing exclusivity dominated the market and had the largest market share when compared to any other single market participant for the case. In the long run, authorized generics might discourage independent generic companies from timely generic introductions. Policy limiting the entry of an authorized generic during the 180-day marketing exclusivity of an independent generic might prevent delayed generic entry.
Creating Bigger Problems: Grand Challenges as Boundary Objects and the Legitimacy of the Information Systems Field
Authors: Winter Susan J , Butler Brian S
Published: April 2011

The impact of a discipline's research is constrained by its ability to articulate compelling problems. Well-crafted problems are the foundation for mobilizing the effort, resources, and attention essential to scientific progress and broader impact. We argue that Information Systems (IS) scholars, individually and collectively, must develop the practice of articulating and engaging large-scale, broad scope problems – or grand challenges. To support this position, we examine the role and value of grand challenge efforts in science and engineering based on a theory of grand challenges as socially constructed boundary objects. Conceptualizing grand challenges in these terms implies strategies and approaches for magnifying the impact of IS research by engaging these types of problems.
Optical emission spectroscopy of metal vapor dominated laser-arc hybrid welding plasma
Authors: Ribic B. , Burgardt P. , DebRoy T.
Published: April 2011

During laser-arc hybrid welding, plasma properties affect the welding process and the weld quality. However, hybrid welding plasmas have not been systematically studied. Here we examine electron temperatures, species densities, and electrical conductivity for laser, arc, and laser-arc hybrid welding using optical emission spectroscopy. The effects of arc currents and heat source separation distances were examined because these parameters significantly affect weld quality. Time-average plasma electron temperatures, electron and ion densities, electrical conductivity, and arc stability decrease with increasing heat source separation distance during hybrid welding. Heat source separation distance affects these properties more significantly than the arc current within the range of currents considered. Improved arc stability and higher electrical conductivity of the hybrid welding plasma result from increased heat flux, electron temperatures, electron density, and metal vapor concentrations relative to arc or laser welding.
A perspective on slow-relaxing molecular magnets built from rare-earths and nitronyl-nitroxide building blocks (invited)
Authors: Bogani Lapo
Published: April 2011

We offer a perspective, accessible to both chemists and physicists, of recent developments in the synthesis and characterization of molecular magnetic materials based on rare-earths and nitronyl-nitroxide radicals. We show both the rationale of the synthetic strategies and the observed behaviors. We highlight the relevance of these findings for synthetic chemists, material scientists, and physicists.
Modeling of the dynamic inelasticity of tantalum single crystal under ramp wave loading
Authors: Ding J. L. , Asay J. R.
Published: April 2011

In a previous study, the behavior of single crystal tantalum under ramp wave loading along the [100] and [110] orientations was characterized. The principal objective of the present study is to gain some insights on the observed single crystal behavior particularly on its precursor response and strong orientation dependence, and the implication of the macroscopic behavior on the possible underlying deformation mechanisms. The approach used to achieve this objective is through the material model development and numerical simulation. A continuum model developed in a previous work for polycrystalline tantalum was first modified to describe the experimental data and extract the material information associated with the data. A rigorous finite deformation single crystal model based on dislocation slip was then developed to gain physical insights into the possible deformation mechanisms. The slip systems considered were the {110}〈111〉 and {112}〈111〉 systems. Dislocation density and its evolution by nucleation or multiplication were incorporated as a key mechanism for describing the precursor behavior in both models. The orientation dependence was modeled through the assumption of anisotropic dislocation nucleation. In the continuum model, different nucleation rates were assumed for the [100] and [110] orientation. In the single crystal model, this anisotropy is assumed to be associated with the twinning/antitwinning asymmetry of the BCC crystals. The precursor for the [100] orientation is attributed mainly to the slips along the antitwinning direction and that for the [110] is to the slips along the twinning direction. The anisotropic dislocation nucleation leads to the orientation dependence of the rate sensitivity of single crystal Ta and the subsequent deformation behavior. Both models were demonstrated to be able to generate reasonably consistent results and to capture the observed material features. Through the developed models, a reasonable understanding was achieved for the evolution of stress, strain, strain rates, strength, temperature, and stress strain relations for single crystal tantalum under ramp wave loading and the possible correlation between the macroscopic behavior and microscopic deformation mechanisms.
Surface electrophoresis of ds-DNA across orthogonal pair of surfaces
Authors: Ghosh Arnab , Patra Tarak K. , Kant Rishi , Singh Rajeev Kr. , Singh Jayant K. , Bhattacharya Shantanu
Published: April 2011

A gel free microchannel device made up of polydimethyl siloxane is fabricated for the surface based electrophoresis of double stranded deoxy-ribonucleic acid (DNA) molecules. In the presence of directional external electric field, DNA fragments near the corners of the microchannel are found to separate faster as compared to those over the base of the channel. This is in spite of the reduction in the mobility of molecules over the channel corners. We performed coarse grained molecular dynamics simulations which reveal that, though the adsorption energy of the DNA fragments increases near the corner, it is the increase in the relative mobility which enhances the separation of the fragments over the corner.
The interface structure and magnetic and electronic properties of a Co2FeAl0.5Si0.5/MgO/Co2FeAl0.5Si0.5 magnetic tunneling junction
Authors: Yu H. L. , Yang G. W.
Published: April 2011

Magnetic tunnel junctions (MTJs) consisting of ferromagnet-insulator-ferromagnet sandwiches have attracted significant interest, and the structure of the interfaces in MTJs plays a crucial role in their performance. The interface structure, and magnetic and electronic properties of a Co2FeAl0.5Si0.5/MgO/Co2FeAl0.5Si0.5 MTJ are studied by first-principles calculations. It is found that three interface structures, the Co-, Fe-, and Al-terminated interfaces, are thermally stable. Local density of states calculations show that interface states form at the Fermi level for the Co- and Fe-terminated interfaces, and their half-metallic properties are destroyed. For the Al-terminated interface, half-metallic behavior remains at the interface, and there are no interface states at the Fermi level. This should heavily suppress the spin-flipping and tunneling caused by interface states located at the Fermi level of a Co2FeAl0.5Si0.5/MgO interface, allowing the transport properties of Co2FeAl0.5Si0.5/MgO/Co2FeAl0.5Si0.5 MTJs to be improved.
Enhanced iron magnetic moment in the ThFe11C2 intermetallic compound
Authors: Benea D. , Isnard O. , Minár J. , Ebert H. , Pop V.
Published: April 2011

Detailed theoretical investigations on the electronic and magnetic properties of the ThFe11C2 compound have been performed using both the linear muffin-tin orbital and Korringa–Kohn–Rostocker methods of band structure calculation. The structure of the ThFe11C2 compound has three inequivalent iron sites with different local environment. A strongly enhanced magnetic moment is observed on certain Fe positions, coexisting with much lower magnetic moments on other iron positions of the lattice. Band structure calculations indeed show that the Fe magnetic moments depend strongly on the local environment. The average Fe magnetic moment obtained from these calculations is in good agreement with the experimental average Fe moment obtained from magnetization measurements. The orbital contribution to the magnetic moment is found to be especially large on the Fe 4b position. Comparing calculated hyperfine fields with experimental results, it is found that the calculated and experimental hyperfine fields are correlated. However, similarly to the results reported before for elemental Fe, the magnitude of all calculated Fe hyperfine fields is about 25% smaller. The agreement with the Mössbauer measurements is improved by scaling the core polarization contribution and by estimating the orbital valence d-electrons contribution to the magnetic hyperfine fields using the local spin density approximation + dynamical mean field theory calculated orbital moments.
Direct observation of twin deformation in YBa2Cu3O7−x thin films by in situ nanoindentation in TEM
Authors: Lee Joon Hwan , Zhang Xinghang , Wang Haiyan
Published: April 2011

The deformation behaviors of YBa2Cu3O7−x (YBCO) thin films with twinning structures were studied via in situ nanoindentation experiments in a transmission electron microscope. The YBCO films were grown on SrTiO3 (001) substrates by pulsed laser deposition. Both ex situ (conventional) and in situ nanoindentation were conducted to reveal the deformation of the YBCO films from the directions perpendicular and parallel to the twin interfaces. The hardness measured perpendicular to the twin interfaces is ∼50% and 40% higher than that measured parallel to the twin interfaces ex situ and in situ, respectively. Detailed in situ movie analysis reveals that the twin structures play an important role in deformation and strengthening mechanisms in YBCO thin films.
Influences of doping and annealing conditions on the photoluminescence from In2O3 nanocrystals and Eu3+ ions co-doped sol-gel SiO2 films
Authors: Lin Tao , Ding Xue-yun , Xu Jun , Wan Neng , Xu Ling , Chen Kun-ji
Published: April 2011

In2O3 nanocrystals and rare-earth Eu3+ ions co-doped SiO2 films were prepared by sol-gel method and subsequently annealed at high temperature to eliminate the hydroxyl groups. The formation of In2O3 nanocrystals with uniform distribution in the annealed sample was confirmed by transmission electron microscopy and x-ray diffraction spectra. A strong characteristic emission from Eu3+ ions can be identified and the influences of In and Eu doping concentrations on photoluminescence properties were systematically evaluated. It was found that the photoluminescence from Eu3+ ions could be enhanced by two orders of magnitude. This was ascribed to the effective absorption of incident photons by In2O3 nanocrystals, the energy transfer process through oxygen vacancy at the surface of In2O3 nanocrystals to nearby Eu3+ ions and the SiO2 matrix free of hydroxyl groups after high temperature annealing.
Indirect Auger recombination as a cause of efficiency droop in nitride light-emitting diodes
Authors: Kioupakis Emmanouil , Rinke Patrick , Delaney Kris T. , Van de Walle Chris G.
Published: April 2011

InGaN-based light-emitting diodes (LEDs) exhibit a significant efficiency loss (droop) when operating at high injected carrier densities, the origin of which remains an open issue. Using atomistic first-principles calculations, we show that this efficiency droop is caused by indirect Auger recombination, mediated by electron-phonon coupling and alloy scattering. By identifying the origin of the droop, our results provide a guide to addressing the efficiency issues in nitride LEDs and the development of efficient solid-state lighting.
The kinetics study of the S + S2 → S3 reaction by the chaperone mechanism
Authors: Du Shiyu , Germann Timothy C. , Francisco Joseph S. , Peterson Kirk A. , Yu Hua-Gen , Lyons James R.
Published: April 2011

The recombination of S atoms has been found to be stepwise from the smallest unit, the elemental S atom, to the most abundant molecule S8. The reaction between S + S2 → S3 has not been reported either experimentally or by theory, but may be a key intermediate step in the formation of sulfur aerosols in low-O2 atmospheres. In this work, the kinetics of this reaction is reported with Ar gas used as the chaperone molecule in the production of S3 via two complex intermediates: SAr + S2 and S2Ar + S. Quasi-classical and classical trajectory methods are used. The rate constant of the S + S2 + Ar → S3 + Ar reaction is determined to be 2.66 × 10−33 cm6  mol−1 s−1 at 298.15 K. The temperature dependence of the reaction is found to be 2.67 × 10−33 exp[143.56(1/T–1/298.15)]. The second-order rate constant of S + S2 → S3 is 6.47 × 10−14 cm3 molecule−1 s−1 at 298.15 K and the Arrhenius-type rate constant is calculated to be 6.25 × 10−14 exp[450.15(1/T–1/298.15)] cm3 molecule−1 s−1. This work provides a rate coefficient for a key intermediate species in studies of sulfur formation in the modern Venus atmosphere and the primitive Earth atmosphere, for which assumed model rate coefficients have spanned nearly 4 orders of magnitude. Although a symmetry-induced mass-independent isotope effect is not expected for a chaperone mechanism, the present work is an important step toward evaluating whether mass-independence is expected for thiozone formation as is observed for ozone formation.
Domain wall modulated superconductivity in Nb/Y3Fe5O12 hybrids
Authors: Yang Zhaorong , Moshchalkov Victor V.
Published: April 2011

In superconductor/ferromagnet hybrids, the stray field and inhomogeneous exchange field coming from magnetic domain walls have opposite influence on the superconductivity if the ferromagnet displays in-plane anisotropy. In this paper, we investigate modulation of superconductivity by the stray field of Bloch walls in Nb/Y3Fe5O12 hybrids where the proximity effect is excluded. By applying in-plane magnetic field, we show that the resistance as a function of magnetic field displays two dips precisely at the saturation field Hs of Y3Fe5O12. The superconducting transition temperature Tc at Hs is higher than that at lower fields, suggesting the suppression of superconductivity by the stray fields of Bloch walls. By effective controlling of the domain walls, the superconductivity can be switched either on or off.
Thermal conductivity anisotropy and grain structure in Ge2Sb2Te5 films
Authors: Lee Jaeho , Li Zijian , Reifenberg John P. , Lee Sangchul , Sinclair Robert , Asheghi Mehdi , Goodson Kenneth E.
Published: April 2011

Although lateral thermal conduction in Ge2Sb2Te5 (GST) films can influence the performance of phase change memory (PCM), there are no data available for the in-plane thermal conductivity. This work measures both the in-plane and the out-of-plane thermal conductivities for the amorphous, face-centered-cubic, and hexagonal-close-packed phases of GST using two independent techniques. For crystalline GST, we report anisotropy favoring out-of-plane conduction by up to 54%, which varies with annealing time. Scaling arguments indicate that the anisotropy may be due to the thermal resistance of amorphous regions near grain boundaries. This explanation is consistent with transmission electron microscopy images showing columnar grains and amorphous phase at grain boundaries.
Determining the defect density of states by temperature derivative admittance spectroscopy
Authors: Li Jian V. , Levi Dean H.
Published: April 2011

We demonstrate that the temperature derivative admittance spectroscopy method can be used to directly determine the defect density of states. The density of defect states is proportional to the temperature derivative of the capacitance. This method is equivalent to the existing frequency derivative method in principle but possesses certain key advantages for detection of deep levels. To illustrate these advantages, we define the activation energy of a fictitious defect the Arrhenius plot of which extends diagonally across the measurable temperature-frequency range. Below this level (that is, shallower defects), the frequency derivative method is advantageous, and above this level (that is, deeper defects), the temperature derivative method is advantageous. The temperature derivative method allows a wider observation window of defect energy that avoids possible detection failure and facilitates simultaneous observation of multiple defects. For deep defects, it also yields more Arrhenius plot data points and therefore enables more accurate extraction of defect energy and capture cross-sections. In general, the temperature derivative method can avoid system noise at low frequency and is relatively immune to baseline effects due to parasitic circuit effects.
Super-high-frequency shielding properties of excimer-laser-synthesized-single-wall-carbon-nanotubes/polyurethane nanocomposite films
Authors: Aïssa B. , Laberge L. L. , Habib M. A. , Denidni T. A. , Therriault D. , El Khakani M. A.
Published: April 2011

Electromagnetic shielding attenuation (ESA) properties of carbon nanotubes/polymer nanocomposite films, in the super high frequency (SHF) X-band (7–12 GHz) domain are studied. The nanocomposite films consisted of thermoset polyurethane (PU) resin blended with single-walled carbon nanotubes (SWCNTs) mats, and deposited on fused quartz substrates. Two different approaches were used to achieve the nanocomposite films, namely (i) through the on-substrate “all-laser” growth approach of SWCNTs directly onto substrate, followed by their infiltration by the PU resin, and (ii) by appropriately dispersing the chemically-purified SWCNTs (in the soot form) into the PU matrix and their subsequent deposition onto quartz substrates by means of a solvent casting process. Characterizations of the ESA properties of the developed nanocomposite films show that they exhibit systematically a deep shielding band, centered at around 9.5 GHz, with an attenuation as high as |− 30| dB, recorded for SWCNT loads of 2.5 wt. % and above. A direct correlation is established between the electrical conductivity of the nanocomposite films and their electromagnetic shielding capacity. The SWCNTs/PU nanocomposites developed here are highly promising shielding materials as SHF notch filters, as their ESA capacity largely exceeds the target value of |− 20| dB generally requested for commercial applications.
Low energy electron beam induced damage on InGaN/GaN quantum well structure
Authors: Nykänen H. , Mattila P. , Suihkonen S. , Riikonen J. , Quillet E. , Homeyer E. , Bellessa J. , Sopanen M.
Published: April 2011

In this paper, low energy electron beam (5–20 keV, 0–500 μAs/cm2) induced damage on a GaN/InGaN/GaN near-surface quantum well structure is studied. Exposure to low energy electron beam is shown to significantly reduce the optical quality of the structure. It is also observed that reducing the electron beam energy causes larger PL intensity reduction. This can be explained by considering the beam penetration depth, which is shown to be smaller with lower e-beam energies. The damage is believed to be attributed to enhanced dislocation mobility upon low energy electron beam irradiation. However, further studies are needed to confirm the mechanism. These results should be taken into consideration in low energy electron beam related sample characterization and preparation.
Large-strain-induced magnetic properties of Co electrodeposited on nanoporous Au
Authors: Hakamada Masataka , Hirashima Fumi , Takahashi Masaki , Nakazawa Takumi , Mabuchi Mamoru
Published: April 2011

Nanostructured Co with large lattice extension and contraction was produced by electrodepositing Co on nanoporous Au. The Co deposited showed a low magnetic saturation of 76 emu/g and a high coercivity of 462 Oe. First-principles calculations showed that the magnetic moment of a Co atom is significantly decreased by lattice contraction. Therefore, the noteworthy magnetic properties of the Co deposited are attributed to the large lattice strain. Also, molecular dynamics simulation showed that the lattice extension and contraction of about 10% are generated in the overall Co crystal. This is in agreement with the experimental results of HRTEM observation. The constraint of the movement of Co atoms by the concave structure of nanoporous Au leads to a wide spread of large strain region.
Invariant relationships deriving from classical scaling transformations
Authors: Bludman Sidney , Kennedy Dallas C.
Published: April 2011

Because scaling symmetries of the Euler–Lagrange equations are generally not variational symmetries of the action, they do not lead to conservation laws. Instead, an extension of Noether's theorem reduces the equations of motion to evolutionary laws that prove useful, even if the transformations are not symmetries of the equations of motion. In the case of scaling, symmetry leads to a scaling evolutionary law, a first-order equation in terms of scale invariants, linearly relating kinematic and dynamic degrees of freedom. This scaling evolutionary law appears in dynamical and in static systems. Applied to dynamical central-force systems, the scaling evolutionary equation leads to generalized virial laws, which linearly connect the kinetic and potential energies. Applied to barotropic hydrostatic spheres, the scaling evolutionary equation linearly connects the gravitational and internal energy densities. This implies well-known properties of polytropes, describing degenerate stars and chemically homogeneous nondegenerate stellar cores.
Forced nonlinear resonance in a system of coupled oscillators
Authors: Glebov Sergei , Kiselev Oleg , Tarkhanov Nikolai
Published: April 2011

We consider a resonantly perturbed system of coupled nonlinear oscillators with small dissipation and outer periodic perturbation. We show that for the large time t∼ɛ-2 one component of the system is described for the most part by the inhomogeneous Mathieu equation while the other component represents pulsation of large amplitude. A Hamiltonian system is obtained which describes for the most part the behavior of the envelope in a special case. The analytic results agree with numerical simulations.
Phase transition of nanotube-confined water driven by electric field
Authors: Fu Zhaoming , Luo Yin , Ma Jianpeng , Wei Guanghong
Published: April 2011

The effects of electric field on the phase behaviors of water encapsulated in a thick single-walled carbon nanotube (SWCNT) (diameter = 1.2 nm) have been studied by performing extensive molecular dynamics simulations at atmospheric pressure. We found that liquid water can freeze continuously into either pentagonal or helical solidlike ice nanotube in SWCNT, depending on the strengths of the external electric field applied along the tube axis. Remarkably, the helical one is new ice phase which was not observed previously in the same size of SWCNT in the absence of electric field. Furthermore, a discontinuous solid–solid phase transition is observed between pentagonal and helical ice nanotubes as the strengths of the external electric field changes. The mechanism of electric-field-induced phase transition is discussed. The dependence of ice structures on the chiralities of SWCNTs is also investigated. Finally, we present a phase diagram of confined water in the electric field−temperature plane.
Maximizing dissipation in a turbulent shear flow by optimal control of its initial state
Authors: Delport S. , Baelmans M. , Meyers J.
Published: April 2011

Turbulent shear flows are known to evolve self-similar at sufficiently high Reynolds numbers. In this regime, flow properties remain constant when normalized with local large-scale reference values. Dissipation of turbulent energy occurs at small scales. Thus, controls which increase dissipation levels in a shear flow may lose their effectiveness once the shear flow attains self-similar behavior governed by large-scale motion. In the current work, we investigate the optimal control of kinetic-energy dissipation in a temporally evolving turbulent mixing layer, with controls acting on its initial condition. Gradient-based optimization is used, relying on direct numerical simulations, and adjoint formulations for the determination of the gradients. Focus is on long optimization time windows T up to 160 nondimensional time units. First we investigate the optimal controls which maximize the total energy dissipation over a simulation time window. For increasing T, optimal controls are found to become also optimal for preceding time horizons. Results indicate that these controls facilitate a fast transition of the mixing layer to a self-similar state, which occurs at nondimensional time t≈160–200. We find that the transition Reynolds number at which self-similarity emerges is a factor of 4–5 lower than transition Reynolds numbers reported for uncontrolled temporal mixing layers. Second, we investigate the maximization of the rate of dissipation at the end of the simulation time window. It is observed that dissipation rate can be increased up to two times higher than self-similar dissipation levels. However, at long optimization time windows this leads to a delay of transition to self-similarity. We further find that optimization is strongly nonconvex, and for the second case, we identify two local optima, which are further discussed in terms of differences in coherent structures emerging during the mixing-layer evolution.
The freestanding sensor-based 3ω technique for measuring thermal conductivity of solids: Principle and examination
Authors: Qiu L. , Tang D. W. , Zheng X. H. , Su G. P.
Published: April 2011

In recent two decades, the 3ω technique has been proven to be valuable for characterizing thermophysical properties of materials from nanoscale to bulk, but some inherent deficiencies in this technique such as laborious and repeated four-pad micro strip heater/sensor deposition process and flimsiness of the micro heater/sensor limit its practical applications. Here, the authors report a novel 3ω technique, based on a freestanding sensor replacing the conventional 3ω heater/sensor adjacent to the specimen surface. A zigzag temperature response curve of the new sensor instead of the classical straight line was observed and used to extract the specimen thermal conductivity. Experimental results which excellently agree with calculation values show that the new technique is of great application value to thermal properties characterization of amorphous bulks and hundreds of microns thick wafers.
Patterns and dynamics in transitional plane Couette flow
Authors: Tuckerman Laurette S. , Barkley Dwight
Published: April 2011

Near transition, plane Couette flow takes the form of large-scale, oblique, and statistically steady alternating bands of turbulent and laminar flow. Properties of these flows are investigated using direct numerical simulation in a tilted computational domain. Four regimes—uniform, intermittent, periodic, and localized—are characterized. The Fourier spectrum along the direction of variation of the pattern is presented, and the component corresponding to the pattern wavenumber is investigated as an order parameter. The mean flow of a periodic pattern is characterized and shown to lead to a relation between the Reynolds number and the wavelength and angle of a pattern.
Superconductivity and spectroscopy of homo- and heterofullerides of alkali metals and thallium
Authors: Kulbachinskii V. A. , Bulychev B. M. , Kytin V. G. , Lunin R. A.
Published: April 2011

Liquid alloys of metals with mercury (amalgams) are used to synthesize the fullerides AnHgxC60 (A=K,Rb,Cs; n=2;3; x<1), AnTlmHgxC60 (A=K,Rb,Cs; n=1;2; m=0.25–2; x<1), and NanC60 (n=2,3). The samples are studied by x-ray diffraction, nuclear magnetic resonance, electron paramagnetic resonance, Raman scattering, and differential scanning calorimetry. The NanC60 (n=2,3) fullerides are not superconducting. Structural phase transitions are observed in them as the temperature is varied. K2HgxC60 is a superconductor with a transition temperature Tc=22K, while K3HgxC60 is not superconducting. RbnHgxC60 (n=2,3) are superconductors with Tc=24–25K. The cesium fullerides with an assumed composition of CsnHgxC60 (n=1–3) are either polymers (n=2,3) or crystallize in a rhombic lattice, but none are superconducting. A maximum Tc=22K is observed in the K2TlmHgxC60 fulleride with a thallium concentration m=0.5. CsnTlmHgxC60 (n=1–3; m=1,2) is not superconducting, but KCsTlC60 produced by means of exchange reactions with TlCl is a superconductor with Tc=21.7K.
High quality Ge thin film grown by ultrahigh vacuum chemical vapor deposition on GaAs substrate
Authors: Tang Shih-Hsuan , Chang Edward Yi , Hudait Mantu , Maa Jer-Shen , Liu Chee-Wee , Luo Guang-Li , Trinh Hai-Dang , Su Yung-Hsuan
Published: April 2011

High-quality epitaxial Ge films were grown on GaAs substrates by ultrahigh vacuum chemical vapor deposition. High crystallinity and smooth surface were observed for these films by x-ray diffraction, transmission electron microscopy, and atomic force microscopy. Direct band gap emission (1550 nm) from this structure was detected by photoluminescence. Valence band offset of 0.16 eV at the Ge/GaAs interface was measured by x-ray photoelectron spectroscopy. N-type arsenic self-doping of 1018/cm−3 in the grown Ge layers was determined using electrochemical capacitance voltage measurement. This structure can be used to fabricate p-channel metal-oxide-semiconductor field-effect transistor for the integration of Ge p-channel device with GaAs n-channel electronic device.
Fourier transform microwave and millimeter wave spectroscopy of quinazoline, quinoxaline, and phthalazine
Authors: McNaughton Don , Godfrey Peter D. , Jahn Michaela K. , Dewald David A. , Grabow Jens-Uwe
Published: April 2011

The pure rotational spectra of the bicyclic aromatic nitrogen heterocycle molecules, quinazoline, quinoxaline, and phthalazine, have been recorded and assigned in the region 13–87 GHz. An analysis, guided by ab initio molecular orbital predictions, of frequency-scanned Stark modulated, jet-cooled millimeter wave absorption spectra (48–87 GHz) yielded a preliminary set of rotational and centrifugal distortion constants. Subsequent spectral analysis at higher resolution was carried out with Fourier transform microwave (FT-MW) spectroscopy (13–18 GHz) of a supersonic rotationally cold molecular beam. The high spectral resolution of the FT-MW instrument provided an improved set of rotational and centrifugal distortion constants together with nitrogen quadrupole coupling constants for all three species. Density functional theory calculations at the B3LYP/6-311+G** level of theory closely predict rotational constants and are useful in predicting quadrupole coupling constants and dipole moments for such species.
Comparison of the interfacial and electrical properties of HfAlO films on Ge with S and GeO2 passivation
Authors: Li X. F. , Liu X. J. , Zhang W. Q. , Fu Y. Y. , Li A. D. , Li H. , Wu D.
Published: April 2011

We report the characteristics of HfAlO films deposited on S- and GeO2-passivated Ge substrates at 150 °C by atomic layer deposition technique using Hf(NO3)4 and Al(CH3)3 as the precursors. The x-ray photoelectron spectroscopic analyses reveal that GeO2 passivation is more effective to suppress GeOx formation than S passivation. It is demonstrated that the capacitors with GeO2 passivation exhibit better electrical properties with less hysteresis, improved interface quality, and reduced leakage current. These results indicate that using GeO2 as an interfacial layer may be a promising approach for the realization of high quality Ge-based transistor devices.
Surface-plasmon-enhanced band-edge emission from Au/GaN powders
Authors: Nakamura Toshihiro , Hosaka Tomohiro , Adachi Sadao
Published: April 2011

Band-edge emission from GaN nanopowders is strongly enhanced by the deposition of Au nanoparticles. This enhancement in photoluminescence emission results from resonant absorption of the defect-related emission caused by the localized surface plasmons in the Au nanoparticles and subsequent charge transfer from Au to GaN. The enhanced band-edge emission is also found to be due to the recombination of excitons bound to shallow defect states. Furthermore, such enhanced band-edge emission shows phonon replicas with an energy separation of 69±2 meV. This energy value corresponds to that of transverse-optical phonons, and not to that of the commonly observed longitudinal-optical phonons.
Conducting interpenetrating polymer network sized to fabricate microactuators
Authors: Khaldi Alexandre , Plesse Cédric , Soyer Caroline , Cattan Eric , Vidal Frédéric , Legrand Christiane , Teyssié Dominique
Published: April 2011

Interpenetrating polymer networks can become successful actuators in the field of microsystems providing they are compatible with microtechnologies. In this letter, we report on a material synthesized from poly(3,4-ethylenedioxythiophene) and polytetrahydrofuran/poly(ethylene oxide) and microsized by decreasing its thickness to 12 μm and patterning the lateral side using plasma etching at high etch rates and with vertical sidewalls. A chemical process and a “self degradation” are proposed to explain such etching rates. Preliminary actuation results show that microbeams can move with very large displacements. These microsized actuators are potential candidates in numerous applications, including microswitches, microvalves, microoptical instrumentation, and microrobotics.
Optical waveguide loss minimized into gallium nitride based structures grown by metal organic vapor phase epitaxy
Authors: Stolz A. , Cho E. , Dogheche E. , Androussi Y. , Troadec D. , Pavlidis D. , Decoster D.
Published: April 2011

The waveguide properties are reported for wide bandgap gallium nitride (GaN) structures grown by metal organic vapor phase epitaxy on sapphire using a AlN/GaN short period-superlattice (SPS) buffer layer system. A detailed optical characterization of GaN structures has been performed using the prism coupling technique in order to evaluate its properties and, in particular, the refractive index dispersion and the propagation loss. In order to identify the structural defects in the samples, we performed transmission electron microscopy analysis. The results suggest that AlN/GaN SPS plays a role in acting as a barrier to the propagation of threading dislocations in the active GaN epilayer; above this defective region, the dislocations density is remarkably reduced. The waveguide losses were reduced to a value around 0.65dB/cm at 1.55 μm, corresponding to the best value reported so far for a GaN-based waveguide.
The 1BL/1RS translocation decreases grain yield of spring wheat germplasm in low yield environments of north-eastern Australia
Authors: Peake Allan S. , Gilmour Arthur , Cooper Mark
Published: April 2011

Wheat (Triticum aestivum L.) lines containing the 1BL/1RS chromosome translocation yield up to 20% more than established wheat cultivars in some Queensland environments. However, 1BL/1RS germplasm possesses a quality defect known as ‘sticky dough’, which is incompatible with the high-speed dough-mixing processes used for bread production in Australia. Therefore, we investigated whether the 1BL/1RS translocation conveyed a yield advantage to locally adapted germplasm across a wide range of environments that was sufficient to justify attempting to overcome the ‘sticky dough’ defect either through plant breeding or by altering the mixing processes. Three sets of recombinant inbred lines (RILs) that segregated for the presence or absence of the 1BL/1RS translocation were developed from crosses between 1BL/1RS germplasm (Seri and Genaro) and established local cultivars (Hartog and Banks), and grown in 11 environments representing six sites across southern Queensland and northern New South Wales and two years. The effect of the 1BL/1RS translocation on grain yield depended on environment and genetic background. In semi-dwarf genotypes of the Hartog/Seri and Hartog/Genaro crosses, the 1BL/1RS RILs had lower grain yield than the 1B RILs in the three lowest yielding environments. This effect was associated with changes in grain number per unit area, suggesting that the negative yield effect of the translocation is expressed before, or at, anthesis. In the higher yielding environments, the 1BL/1RS translocation conveyed a yield advantage in semi-dwarf genotypes of the Banks/Seri cross, but had no consistent effect on yield in semi-dwarf genotypes of the Hartog/Seri and Hartog/Genaro crosses. The 1BL/1RS translocation was also associated with decreased yield in the double-dwarf genotypes of the Hartog/Seri cross across all environments. We conclude that the 1BL/1RS translocation is not useful for local breeding programs, as it decreased yield among the more advanced, semi-dwarf germplasm in low-yielding environments that potentially represent up to 85% of the target population of environments, and had no consistent positive effect on yield in this germplasm in higher yielding environments.
Sward and tiller growth dynamics of Lolium perenne L. as affected by defoliation frequency during autumn
Authors: Poff Jonathan A. , Balocchi Oscar A. , López Ignacio F.
Published: April 2011

A mini-sward study was undertaken between January and September 2008 in Valdivia, Chile, to quantify and compare changes in the herbage production, growth dynamics and nutritive quality of a Lolium perenne sward during autumn in response to different nitrogen (N) application regimes and defoliation frequencies. The N levels used in the present study corresponded to the equivalent of an autumnal application of 0, 25 or 75 kg N/ha. The defoliation frequency was based on leaf regrowth stage, and corresponded to the time taken for 1.5, 2.5 or 3.5 leaves per tiller to expand. The growth dynamic measurements were also related to temperature. The results showed that the level of N had no effect on the studied variables. Plants defoliated at the 3.5-leaf stage showed a higher herbage production, higher tillering and a more balanced nutritional profile than plants cut at the 1.5-leaf stage. The defoliation interval had no effect on leaf elongation or leaf appearance. The leaf elongation rate was linearly related to the mean daily temperature (P < 0.01), and the accumulated leaf and tiller number showed a significant linear relationship (P < 0.01) with the thermal time expressed as growing degree days. From the defoliation frequencies tested here, we can conclude that the best time for grazing L. perenne swards during autumn is at the 3.5-leaf stage due to a higher herbage production, higher tillering rate, more balanced nutritive quality and higher reserve levels of the plant, which provide a more favourable background for subsequent growth.
Nitrogen and sulfur uptake and remobilisation in canola genotypes with varied N- and S-use efficiency differ at vegetative and maturity stages
Authors: Balint Tatjana , Rengel Zdenko
Published: April 2011

Eight canola genotypes chosen from a preliminary screening study with either high or low nitrogen (N) and/or sulfur (S) efficiency indices were tested for consistency in S and/or N efficiency between vegetative stage and maturity. Soil labelling was used to assess 15N/N or 34S/S uptake, and a leaf feeding–labelling technique was used to study transport and remobilisation of N and S. Plants were grown under glasshouse conditions using deficient or adequate N and/or S supply. Nitrogen and S uptake in plants was assessed using the following criteria: growth, N and/or S concentration, and 15N and/or 34S atom excess in above-ground plant parts. Transport and remobilisation of N and S were assessed via the same assessment criteria in plants at 2 days (1st harvest) and 6 days (2nd harvest) after commencement of leaf-labelling. Genotype Wesway was more efficient than Westar in taking up N during the vegetative stage as well as in remobilising N from leaves, stems, and siliques to seeds at maturity. Genotype Surpass 402 CL appeared to be more efficient than Karoo in taking up S during the vegetative stage and particularly during the maturity stage, but was less efficient than Karoo in remobilising S from leaves and stems to siliques and seeds at maturity. Soil and leaf labelling techniques using 15N and 34S appeared to be useful tools for studying uptake, transport, and remobilisation of N and S during the vegetative and maturity stages in canola genotypes differing in N- or S-use efficiency.