bluuebunny/crossref_metadata_2025_split huggingface dataset:
Hole–polar phonon interaction scattering mobility in chain structured TlSe0.75S0.25 crystals
Authors: Qasrawi A. F. , Gasanly N. M. 
Published: March 2009

AbstractIn this study, the electrical resistivity, charge carriers density and Hall mobility of chain structured TlSe0.75S0.25 crystal have been measured and analyzed to establish the dominant scattering mechanism in crystal. The data analyses have shown that this crystal exhibits an extrinsic p‐type conduction. The temperature‐dependent dark electrical resistivity analysis reflected the existence of three energy levels located at 280 meV, 68 meV and 48 meV. The temperature dependence of carrier density was analyzed by using the single donor–single acceptor model. The carrier concentration data were best reproduced assuming the existence of an acceptor impurity level being located at 68 meV consistent with that observed from resistivity measurement. The model allowed the determination of the hole effective mass and the acceptor–donor concentration difference as 0.44m0 and 2.2 × 1012 cm–3, respectively. The Hall mobility of the TlSe0.75S0.25 crystal is found to be limited by the scattering of charged carriers over the (chain) boundaries and the scattering of hole–polar phonon interactions above and below 300 K, respectively. The value of the energy barrier height at the chain boundaries was found to be 261 meV. The polar phonon scattering mobility revealed the high‐frequency and static dielectric constants of 13.6 and 15.0, respectively. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Beyond the AlGaN/GaN HEMT: new concepts for high‐speed transistors
Authors: Palacios Tomas 
Published: March 2009

AbstractSolid state power amplifiers operating at mm‐ and sub‐mm‐wave frequencies are key components of numerous communication, sensors and defense systems. Nitride semiconductors have the potential to provide unprecedented levels of power at these frequencies. However, a multidimensional design and optimization is required to achieve acceptable levels of power gain and efficiency at high frequencies. In this paper we discuss some of the main challenges to increase the operating frequency of nitride transistors. New solutions are proposed to increase the electron confinement, electron velocity and access resistances of deeply scaled devices (Abstract figure) and to unleash their great potential. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Porous silicon versus its composite with C60: testing in vitro
Authors: Kuznetsov S. N. , Volkova T. O. , Pikulev V. B. , Saren A. A. , Gardin Yu. E. , Gurtov V. A. 
Published: March 2009

AbstractWe have studied in vitro an efficiency of the promising photosensitizer for photodynamic therapy (PDT) on the base of porous silicon (PSi) impregnated with fullerene C60. It is shown that a low concentration addition of fullerene boosts sharply a cancer cell killing in comparison with the pristine PSi. A dark toxicity of the proposed composite drug for PDT does not exceed that for the pristine PSi as it was revealed for observation period of five days. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Investigation of humidity adsorption in porous silicon layers
Authors: Kovacs Andras , Meister Dirk , Mescheder Ulrich 
Published: March 2009

AbstractThe dependence of humidity adsorption in porous silicon (PS) layers on the fabrication conditions (current density and oxidation) has been investigated. As‐prepared and additionally oxidized PS layers have been investigated using physical gas (N2) adsorption measurement at 77 K, water vapor adsorption measurements at room temperature, impedance spectroscopy and contact angle measurement. Pore size distributions and specific surface areas have been calculated using the BJH and BET model. Additional oxidation of porous layer promotes the humidity adsorption and improves the wetting compared to as‐fabricated porous Si layers. The correlation between adsorption isotherms, electrical parameters and surface effects are presented and discussed in respect to the use of PS for humidity sensing. Oxidation of PS layers improves the sensitivity of PS based humidity sensors considerably. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Photoreflectance spectroscopy for the qualification of GaAsSb alloys introduced in ultrafast heterojunction bipolar transistors on InP
Authors: Chouaib Houssam , Bru‐Chevallier Catherine , Apostoluk Aleksandra , Rudno‐Rudzinski Wojciech , Pelouard Jean‐Luc , Lijadi Melania , Bove Philippe 
Published: March 2009

AbstractGaAsSb is an important III–V semiconductor ternary alloy which is currently used as the thin base layer in high speed InP Heterojunction Bipolar Transistors (HBT). Up to now, very little is known about physical properties of GaAsSb alloys, such as surface Fermi level pinning and Schottky barrier heights with different contact metals. However such parameters impact directly the cut‐off frequency of HBT devices. Photoreflectance spectroscopy is applied to specific samples differing by their Sb concentration. The exploitation of Franz–Keldysh Oscillations (FKO) spectra allows determining the Fermi level pinning at the free surface of GaAsSb as a function of the alloy composition. Micro‐electroreflectance spectroscopy is also applied to Schottky diodes performed on the same structures, with Ti deposited at the GaAsSb surface. The Schottky barrier height between GaAsSb and Ti is derived from the FKO system recorded in the micro‐electroreflectance spectra. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
The magnetic properties of DyFe2Si2 and its crystal‐field levels
Authors: Liu Z.‐S. , Diviš M. , Sechovský V. 
Published: March 2009

AbstractWe used a two‐ion model to derive analytic formulas for the magnetization of DyFe2Si2 with its lowest crystal‐field (CF) states in the presence of an external field exerted in the easy c and hard a directions, respectively, and then evaluated the initial spontaneous magnetization and the Néel temperature of the magnet with the formulas obtained. In comparison with experimental data, our theoretical results suggest that the magnetic process along the easy axis is dominated by the two lowest CF states in the temperature range at least up to 20 K, but the magnetic behaviour in the hard a direction is governed by the six states of the three lowest CF doublets. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Highly nonlinear phenomena of self‐organization of quasi‐two‐dimensional electron gas in high magnetic and electric fields
Authors: Maglevanny I. I. 
Published: March 2009

AbstractThe transverse electric field Ey that appears in lateral superlattices (2SLs) under Hall‐measurement conditions, i.e. in the presence of a longitudinal applied electric field Ex and applied magnetic field H normal to the SL plane (H ∥ OZ) is calculated. In contrast to previous works devoted to this problem both applied electric and magnetic fields are treated as control parameters. By introducing the generalized function of entropy production (the synergetic potential) the kinetic behavior of a quasi‐two‐dimensional nonequilibrium electron gas is investigated from the viewpoint of self‐organization and catastrophe theory. The field Ey contains both the Hall field and the spontaneous transverse electric field that exists without H. The magnetoresistance caused by the appearance of a spontaneous transverse EMF is investigated. Spontaneous transverse EMF, current–voltage characteristics and magnetoresistance are multivalued and sign‐changing functions of applied electric and magnetic fields. From the model computer simulations the observed multistability exhibits a large difference in the behavior of the system in high magnetic fields as compared to low one. The novel nonlinear effects such as first‐order nonequilibrium phase transitions and hysteresis, induced by magnetic field are predicted. As the magnetic field is increased the nonlinear behaviors show self‐organized hierarchical complexity, which manifests itself in fractalization of bifurcation set, whose self‐similar fine structure leading to fractal‐like folds of critical manifold sheets, resulting in fuzzy bifurcations, was discovered. Complex nonlinear behaviors including macrostate crisis and chaotic‐looking intermittency of Hall‐effect characteristics were discovered in limited narrow ranges of the control parameter space. (© 2009 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Efficient moist physics schemes for data assimilation. II: Deep convection
Authors: Stiller O. 
Published: March 2009

AbstractThe development of a cost‐effective convection scheme for a linear 4D‐Var model is described. The very noisy and unsteady behaviour of the Met Office's nonlinear mass‐flux convection scheme motivated an approach in which the linear model is designed to correspond to its nonlinear counterpart only in a time‐average sense. Technically this is implemented in a numerically efficient way by pre‐processing (mainly time‐averaging) the linear scheme's main input files outside the linear model. The new linear scheme includes only two terms from the nonlinear parametrization's sensitivities; one originates from the subsidence part, while the other, the dominant term, involves convective mass‐flux perturbations resulting from the convective available potential energy (CAPE) closure relationship. Including these terms required error mitigation measures, partially to compensate for neglected terms that in some situations have the opposite sign to the represented terms. Measures were also taken to increase the scheme's stability as well as its numerical efficiency. The introduction of this scheme into the Met Office numerical weather prediction (NWP) system led to clear improvements of the forecast skill. Linearization test results show that the new scheme improves the match between linear and nonlinear models. Consistent with its statistical interpretation, precipitation increments of the linear scheme show a reasonable correlation to their nonlinear counterparts only if the nonlinear precipitation is averaged over time intervals of several hours. ©Crown Copyright 2009. Reproduced with the permission of HMSO. Published by John Wiley & Sons Ltd.
The local ETKF and SKEB: Upgrades to the MOGREPS short‐range ensemble prediction system
Authors: Bowler Neill E. , Arribas Alberto , Beare Sarah E. , Mylne Kenneth R. , Shutts Glenn J. 
Published: March 2009

AbstractThe Met Office has been routinely running a short‐range global and regional ensemble prediction system (EPS) since the summer of 2005. This article describes a major upgrade to the global ensemble, which affected both the initial condition and model uncertainty perturbations applied in that ensemble. The change to the initial condition perturbations is to allow localization within the ensemble transform Kalman filter (ETKF). This enables better specification of the ensemble spread as a function of location around the globe. The change to the model uncertainty perturbations is the addition of a stochastic kinetic energy backscatter scheme (SKEB). This adds vorticity perturbations to the forecast in order to counteract the damping of small‐scale features introduced by the semi‐Lagrangian advection scheme.Verification of ensemble forecasts is presented for the global ensemble system. It is shown that the localization of the ETKF gives a distribution of the spread as a function of latitude that better matches the forecast error of the ensemble mean. The SKEB scheme has a substantial effect on the power spectrum of the kinetic energy, and with the scheme a shallowing of the spectral slope is seen in the tail. A k−5/3 slope is seen at wavelengths shorter than 1000 km and this better agrees with the observed spectrum. The local ETKF significantly improves forecasts at all lead times over a number of variables. The SKEB scheme increases the rate of growth of ensemble spread in some variables, and improves forecast skill at short lead times. ©Crown Copyright 2009. Reproduced with the permission of HMSO. Published by John Wiley & Sons Ltd.
Ensemble transform Kalman filter perturbations for a regional ensemble prediction system
Authors: Bowler Neill E. , Mylne Kenneth R. 
Published: March 2009

AbstractThe Met Office has been routinely running a short‐range ensemble prediction system since the summer of 2005. This system consists of two component ensembles, a global ensemble that provides lateral boundary conditions to a regional ensemble. The global ensemble calculates the initial condition perturbations using a local version of the ensemble transform Kalman filter (ETKF). This article details tests of an ETKF run specifically for the regional ensemble.The perturbations using the ETKF for the regional ensemble contain more detail on small scales and less power on large scales. This extra small‐scale detail persists for less than 18 h. These perturbations are overall smaller than the ones derived from the global ensemble, since they have been explicitly scaled to match the average error of the ensemble mean forecast at T + 6 h. Aside from the difference in the overall scaling of the perturbations, the skill of the two ensembles is very similar, with slightly higher skill being seen when the perturbations are derived from the global ensemble. The ETKF for the regional ensemble was implemented during May 2007. This change has recently been reversed, following these results.These comparisons may shed some light on whether the regional ensemble is providing a ‘dynamical downscaling’ of the global ensemble, or unique information of its own. In these tests the ensemble run with perturbations from the global ensemble was slightly more skilful than the regional perturbations ensemble, indicating that improving on dynamical downscaling is likely to be difficult. ©Crown Copyright 2009. Reproduced with the permission of HMSO. Published by John Wiley & Sons Ltd.
Density Functional Theory‐based Quantitative Structure Activity Relationship (QSAR) Study of Alkanol and Alkanthiol Derivatives
Authors: Mehdipour Ahmad Reza , Safarpour Mohammad Ali , Taghavi Fariba , Jamali Maryam 
Published: March 2009

AbstractThe usefulness of the quantum chemical descriptors and a novel group of descriptors called quantum topological molecular similarity (QTMS) indices, calculated at the level of density functional theory (DFT) using 6‐311++G** basis set for QSAR study of anesthetic drugs was examined. A data set containing 24 alkanol and alkanethiol derivatives with known activity was used. Three types of molecular descriptors including QTMS, chemical and quantum chemical was used to derive a quantitative relationship between the anesthetic potency and structural properties. MLR and GA‐PLS were employed to model the relationships between molecular descriptors and biological activity of molecules. Some multiparametric equations containing three descriptors with appropriate statistical qualities were obtained Also, GA‐PLS regression was used to model the structure‐activity relationships more accurately. The results showed that the results obtained by GA‐PLS are similar to MLR and confirmed that hydroxyl group might be the most important region in anesthetic activity of alkanols and akanethiols.
Novel Pirinixic Acids as PPARα Preferential Dual PPARα/γ Agonists
Authors: Zettl Heiko , Dittrich Michaela , Steri Ramona , Proschak Ewgenij , Rau Oliver , Steinhilber Dieter , Schneider Gisbert , Lämmerhofer Michael , Schubert‐Zsilavecz Manfred 
Published: March 2009

AbstractPirinixic acid is a moderate agonist of both the alpha and the gamma subtype of the peroxisome proliferator activated receptor (PPAR). Previously, we have shown that α‐alkyl substitution leads to balanced low micromolar‐active dual agonists of PPARα and PPARγ. Taking α‐hexyl pirinixic acid as a new scaffold, we further optimized PPAR activity by enlargement of the lipophilic backbone by substituting the 2,3‐dimethylphenyl with biphenylic moieties. Such a substitution pattern had only minor impact on PPARγ activity but further increased PPARα activity leading to nanomolar activities. Supporting docking studies proposed that the (R)‐enantiomer should fit the PPARα ligand‐binding pocket better and thus be more active than the (S)‐enantiomer. Single enantiomers of selected active analogues were then prepared by enantio‐selective synthesis and enantio‐selective preparative HPLC, respectively. Biological data for the distinct enantiomers fully corroborated the docking experiments and substantiate a stereochemical impact on PPAR activation.
Dynamic update of Java applications—balancing change flexibility vs programming transparency
Authors: Gregersen Allan Raundahl , Jørgensen Bo Nørregaard 
Published: March 2009

AbstractThe ability to dynamically change the behavior of an application is becoming an important issue in contemporary rich client software development. Not only can programmers benefit from dynamic updates during the development of concurrent applications where recreation of complex application states can be avoided during test and debugging but also at post‐deployment time where applications can be updated transparently without going through the well‐known halt, redeploy and restart scheme. In this paper, we explain how our dynamic update framework achieves transparent dynamic updates of running Java applications while guaranteeing both type and thread safety. A novel feature of our approach is that it supports full redefinition of classes by allowing changes to the type hierarchy. Our approach is based on a lightweight runtime system, which is injected into an application via bytecode transformations at class loading. We show how our approach can add dynamic update capabilities to rich client development by integrating it with the NetBeans rich client platform. Performance experiments on our NetBeans implementation show that the overhead of our approach is low when applied to component application programming interface classes. To the best of our knowledge no other existing approach achieves the same level of low overhead and programming transparency. Copyright © 2009 John Wiley & Sons, Ltd.
Upgrading mainland Europe's oldest iron suspension footbridge
Authors: Wouters Ine , Bouw Michael de , Adriaenssens Sigrid , Verdonck Ann 
Published: March 2009

AbstractWissekerke castle park in Belgium contains mainland Europe's oldest remaining iron suspension bridge (1824). In 1989, after years of neglect, the Kruibeke town council bought the castle, park and finally, in 2006, the bridge. The Architectural Engineering Lab of the Vrije Universiteit Brussel (æ‐lab) was consulted to put the refurbishment on the right lines and to check whether this bridge can stand the shift in function from private to public.This paper places the pedestrian bridge within the framework of 19th century bridge construction, determines its historical value, characterizes the used materials by metallographic methods combined with tensile and hardness tests, re‐analyses the structure, proposes strengthening strategies and concludes with a renovation proposal that preserves all of the authentic elements, causes the least visual impact, is durable and guarantees continued public use.
A Simple Mechanochemical Route to Layered Double Hydroxides: Synthesis of Hydrotalcite‐Like Mg‐Al‐NO3‐LDH by Manual Grinding in a Mortar
Authors: Ay Ahmet N. , Zümreoglu‐Karan Birgül , Mafra Luis 
Published: March 2009

AbstractHydrotalcite‐like Mg‐Al‐NO3‐layered double hydroxide (LDH) was successfully prepared in a mortar by manually grinding the hydrated magnesium and aluminum nitrate salts with sodium hydroxide. Various techniques, including XRD, MAS NMR, FTIR, SEM; thermogravimetric and differential thermal analyses (TGA,DTA), surface area and zeta potential measurements were used to establish a correlation between the LDH samples prepared in the mortar and by co‐precipitation. The LDH prepared in the mortar showed all the characteristics of a layered structure but with a lower crystallinity. This product was tested for its anion exhange property with tetraborate anions and 52 % of the theoretical exchange capacity was reached. The mortar route does not require heating/refluxing treatment, CO2‐free atmosphere and solvent as in the conventional preparation methods and allows obtaining LDHs in a short reaction time.
[Fe(C6H14N2)2][Sb6S10] – Using a Transition Metal Complex Acting as a Pillar for the Generation of a Three‐dimensional Thioantimonate(III) Network
Authors: Kiebach Ragnar , Warratz Ralph , Näther Christian , Bensch Wolfgang 
Published: March 2009

AbstractThe new three‐dimensional thioantimonate [Fe(C6H14N2)2][Sb6S10] was obtained under solvothermal conditions. The compound crystallizes in space group P with a = 6.174(4), b = 9.679(2), c = 12.772(3) Å, α = 72.08(3), β = 88.15(3), γ = 89.51(3)°, Z = 2. Trigonal pyramidal [SbS3] units and [SbS4] groups are joined to form a two‐dimensional [Sb6S10]2– layer. The in‐situ formed [Fe(C6H14N2)2]2+ complexes act like pillars joining the layers into a three‐dimensional framework through Fe–S bonds. The Fe–S bond lengths are long which may be caused by a pronounced Jahn–Teller distortion. The optical bandgap of 2.0 eV is in agreement with the brownish color of the compound. The Mössbauer spectrum shows a doublet with an isomer shift typical for Fe2+ in the high spin state. In the Raman spectrum the Sb–S stretching modes of the [SbS3] and [SbS4] groups can be distinguished. Upon heating in nitogen the compound is decomposed in one step yielding Sb2S3 and FeSb2S4.
[Cu(H2O)(C5H14N2)2][VO3]2 – A Metavanadate Containing Right‐ and Left‐Handed Helical Chains
Authors: Wutkowski Adam , Näther Christian , Bensch Wolfgang 
Published: March 2009

AbstractThe new metavanadate [Cu(H2O)(C5H14N2)2][VO3]2 (C5H14N2 is 2,2‐dimethylpropyldiamine) (1) was synthesized under solvothermal conditions. The compound crystallizes in the rhombohedral space group R3m with a = 28.6984(15), c = 6.4309(3), V = 4586.9(4) Å3, Z = 9. The main structural motifs are helical metavanadate {VO3}nn– chains made by corner‐sharing [VO4]3– tetrahedra and [Cu(H2O)(C5H14N2)2]2+ complexes with the Cu2+ ion being in a distorted square‐pyramidal coordination environment. The complexes are located between left‐ and right‐handed metavanadate chains.The arrangement of the chains and the [Cu(H2O)(C5H14N2)2]2+ complexes generates channels with liphophilic walls running along [001]. It seems that the orientation of the [Cu(H2O)(C5H14N2)2]2+ moieties is fixed between the metavanadate chains by strong hydrogen bonding interactions. This special arrangement prevents Cu–O bond formation as observed in many Cu2+ containing metavanadate compounds. The compound decomposes in at least three steps. The optical bandgap was determined to 3.04 eV.
Hydrothermal Synthesis of Chiral Metal(II) Phosphinates Derived from Camphor
Authors: Beckmann Jens , Duthie Andrew , Rüttinger Roman , Schwich Torsten 
Published: March 2009

AbstractThe diastereoselective synthesis of bis(3‐endo‐camphoryl)phosphinic acid (1) and its 2‐bornen‐2‐yl ester 2 from the reaction of lithium camphor enolate with phosphorus trichloride and the hydrothermal synthesis of three chiral molecular metal(II) phosphinates of the type M(O2PR2)2·2R2P(O)OH [M = Co (3); Ni (4); Pb (5); R = 3‐endo‐camphoryl] from the reaction of 1 with metal(II) acetates or nitrates is described. The molecular structures of 1–5 are reported.
BaAuP and BaAuAs, Synthesis via Disproportionation of Gold upon Interaction with Pnictides as Bases
Authors: Nuss Jürgen , Jansen Martin 
Published: March 2009

AbstractGold disproportinates in the presence of the Zintl phases Ba3P2 or Ba3As2 forming BaAuP and BaAuAs, respectively, and BaAu2. The air and moisture sensitive ternary compounds crystallise in the ZrBeSi type of structure, an ordered variant of AlB2: BaAuP (P63/mmc; a = 440.68(6) pm; c = 899.8(2) pm; R1 = 0.0237; 183 independent reflections); BaAuAs (P63/mmc; a = 453.53(5) pm; c = 902.7(1) pm; R1 = 0.0255; 168 independent reflections). Both compounds, which are accessible as pure phases by reacting BaP or BaAs with gold, can be classified as poor metallic conductors.