bluuebunny/crossref_metadata_2025_split huggingface dataset:
Ultrafast Electron Dynamics in Metals
Authors: Pitarke Jose M. , Zhukov Vladlen P. , Keyling Robert , Chulkov Evgueni V. , Echenique Pedro M. 
Published: September 2004

AbstractDuring the last decade, significant progress has been achieved in the rapidly growing field of the dynamics of hot carriers in metals. Here we present an overview of the recent achievements in the theoretical understanding of electron dynamics in metals, and focus on the theoretical description of the inelastic lifetime of excited hot electrons. We outline theoretical formulations of the hot‐electron lifetime that originates in the inelastic scattering of the excited quasiparticle with occupied states below the Fermi level of the solid. First‐principles many‐body calculations are reviewed. Related work and future directions are also addressed.
A Computational Investigation of HCN2+ Isomeric Structures: Implications for the Chemistry of Titan's Atmosphere
Authors: Antoniotti Paola , Borocci Stefano , Bronzolino Nicoletta , Grandinetti Felice 
Published: September 2004

AbstractThe structure and stability of various HCN2+ isomeric structures have been investigated at the complete active space SCF (CASSCF) and multireference–configuration interaction [MR‐CI‐SD(Q)] levels of theory with the 6‐31G(d) and 6‐311G(d,p) basis sets. The investigated species include the singlet (S) and triplet (T) open‐chain HNCN+ ions 1S, 1S′, and 1T, the open‐chain HCNN+ ions 2S, 2S′, and 2T, the HCN2+ cyclic structures 3S and 3T, and the HNCN+ cyclic structures 4S and 4T. All these species have been identified as true energy minima on the CASSCF(8,7)/6‐31G(d) potential energy surface, and their optimised geometries, refined at the CASSCF(8,8)/6‐31G(d) level of theory, have been used to perform single point calculations at the [MR‐CI‐SD(Q)]/6‐311G(d,p) computational level. The most stable structure was the HNCN+ ion 1T, whose absolute enthalpy of formation at 298.15 K has been estimated as 333.9±2 kcal mol−1 using the Gaussian‐3 (G3) procedure. The two species closest in energy to 1T are the triplet HCNN+ ion 2T and the singlet diazirinyl cation 3S, whose G3 enthalpies of formation at 298.15 K are 343.5±2 and 340.6±2 kcal mol−1, respectively. Finally, we have discussed the implications of our calculations for the detailed structure of the HCN2+ ions formed in the reaction between N3+ and HCN, experimentally observed by flowing afterglow‐selected ion flow/drift tube mass spectrometry and possibly occurring in Titan's atmosphere.
The Diels–Alder Reaction of Ethene and 1,3‐Butadiene: An Extended Multireference ab initio Investigation
Authors: Lischka Hans , Ventura Elizete , Dallos Michal 
Published: September 2004

AbstractThe concerted and stepwise mechanisms of the Diels–Alder reaction between 1,3‐butadiene and ethene have been investigated using highly correlated multireference methods (MRAQCC) and extended basis sets. Full MRAQCC geometry optimizations have been performed in all cases. The best estimate for the energy barrier of the Diels–Alder reaction is 22 kcal mol−1. Anti‐ and gauche‐out minima for the biradical structures and corresponding fragmentation saddle points have been determined. The biradical anti fragmentation saddle point is located 6.5 kcal mol−1 above the concerted saddle point. The gauche‐in structure does not correspond to a local minimum, but leads on geometry optimization directly to cyclohexene.
Surface Chemistry and Structure of Purified, Ozonized, Multiwalled Carbon Nanotubes Probed by NEXAFS and Vibrational Spectroscopies
Authors: Banerjee Sarbajit , Hemraj‐Benny Tirandai , Balasubramanian Mahalingam , Fischer Daniel A. , Misewich James A. , Wong Stanislaus S. 
Published: September 2004

AbstractUnderstanding of oxidative processes such as solution‐phase ozonolysis in multiwalled carbon nanotubes (MWNTs) is of fundamental importance in devising applications of these tubes as components in composite materials, as well as for development of cutting and filling protocols. We present here an evaluation of various spectroscopic tools to study the structure and composition of functionalized nanotubes. We demonstrate near‐edge X‐ray absorption fine structure (NEXAFS) spectroscopy as a particularly useful and effective technique for studying the surface chemistry of carbon nanotubes.
Mechanism and Kinetics of the Reaction of OH Radicals with Glyoxal and Methylglyoxal: A Quantum Chemistry+CVT/SCT Approach
Authors: Galano Annia , Alvarez‐Idaboy J. Raúl , Ruiz‐Santoyo Ma. Esther , Vivier‐Bunge Annik 
Published: September 2004

AbstractA theoretical study of the mechanism and kinetics of the OH hydrogen abstraction from glyoxal and methylglyoxal is presented. Optimum geometries, frequencies, and gradients have been computed at the BHandHLYP/6–311++G(d,p) level of theory for all the stationary points, as well as for 12 additional points along the minimum energy path (MEP). Energies were obtained by single‐point calculations at the above geometries using CCSD(T)/6–311++G(d,p) to produce the potential energy surface. The rate coefficients were calculated for the temperature range 200–500 K by using canonical variational theory (CVT) with small‐curvature tunneling (SCT) corrections. Our analysis suggests a stepwise mechanism, which involves the formation of a reactant complex. The overall agreement between the calculated and experimental kinetic data is very good. This agreement supports the reliability of the Arrhenius parameters of the glyoxal + OH reaction that are proposed in this work for the first time. The Arrhenius expressions that best describe the studied reactions arek1=(9.63±0.23)×10−13exp[(517±7)/T] andk2=(3.93±0.11)×10−13exp[(1060±8)/T] cm3 molecule−1 s−1for glyoxal and methylglyoxal, respectively.
Coherent Oscillation and Ultrafast Internal Conversion of Tetrafluoroethene after Excitation at 197 nm
Authors: Trushin Sergei A. , Sorgues Sébastien , Fuß Werner , Schmid Wolfram E. 
Published: September 2004

AbstractC2F4was excited by using a 150 fs pulse in its longest‐wavelength band to the Rydberg (3 s) state and then probed by photoionization techniques at 810 nm. The molecule relaxes in two consecutive steps (time constants 29 and 118 fs), probably via the ππ* state, which is lowered in energy by stretching and twisting the CC bond. A coherent oscillation (350 fs) was found, which we assign to an overtone of the twist vibration (47.6 cm−1) in this state. We also conclude that dissociation to singlet and some triplet CF2only takes place in the hot ground state of C2F4, from where also the C2F4triplet state is populated. The potentials and their conical intersections are discussed with respect to relaxation and dissociation, including also some new considerations of thermal processes.
Fabrication, Characterisation and Voltammetric Studies of Gold Amalgam Nanoparticle Modified Electrodes
Authors: Welch Christine M. , Nekrassova Olga , Dai Xuan , Hyde Michael E. , Compton Richard G. 
Published: September 2004

AbstractThe fabrication, characterisation, and electroanalytical application of gold and gold amalgam nanoparticles on glassy carbon electrodes is examined. Once the deposition parameters for gold nanoparticle electrodes were optimised, the analytical utility of the electrodes was examined in CrIII electroanalysis. It was found that gold nanoparticle modified (Au‐NM) electrodes possess higher sensitivity than gold macroelectrodes. In addition, gold amalgam nanoparticle modified (AuHg‐NM) electrodes were fabricated and characterised. The response of those electrodes was recorded in the presence of important environmental analytes (heavy metal cations). It was found AuHg‐NM electrodes demonstrate a unique voltammetric behaviour and can be applied for electroanalysis when enhanced sensitivity is crucial.
Structural Phase Transitions in Heavy Alkali Metals Under Pressure
Authors: Osorio‐Guillén Jorge M. , Ahuja Rajeev , Johansson Börje 
Published: September 2004

AbstractWe performed a theoretical study of the crystal structures of cesium and rubidium under high compressions. Our results confirm the recent high‐pressure experimental observations of new complex crystal structures for the Cs III and Rb III phases. The calculated transition pressures agree extremely well with the measured data. Thus, it is now certain that the famous isostructural phase transition in cesium is actually a new crystallographic phase transition. A d‐orbital occupation number of about 0.52 is crucial for the occurrence of these complex structures.
Attitudes and use of homework assignments in therapy: a survey of German psychotherapists
Authors: Fehm Lydia , Kazantzis Nikolaos 
Published: September 2004

AbstractThere has been continued empirical research on the role of homework assignments in psychotherapy, but little is known about their use in clinical practice. Although attitudes are an important factor in determining whether practitioners use homework assignments, existing data is limited to the frequency and types of assignments used in therapy. One hundred and forty German psychologists were surveyed regarding their use of and attitudes towards homework assignments. Practitioners reported a variety of attitudes regarding the effects of homework on treatment outcome, the process of integrating homework into therapy and patient compliance with homework. We suggest that consideration should be given to therapist attitudes (or beliefs) in future conceptual or empirical work designed to examine homework effects in psychotherapy. Copyright © 2004 John Wiley & Sons, Ltd.
Comparison of coded orthogonal frequency division multiplexing and multicarrier code division multiple access systems for power line communications
Authors: Katsis P. L. , Papadopoulos G. D. , Pavlidou F.‐N. 
Published: September 2004

AbstractOrthogonal frequency division multiplexing (OFDM) and multicarrier code division multiple access (MC‐CDMA) systems are comparatively evaluated for power line communications (PLC) in a frequency‐selective fading environment with additive coloured Gaussian noise which is used to model the actual in‐home power line channel. OFDM serves as a benchmark in order to measure the performance of various MC‐CDMA systems, since multicarrier modulation systems are considered the best candidate for this kind of channel. Both single‐user and multi‐user cases are taken into account, making use of the appropriate combiner schemes to take full advantage of each case.System efficiency is enhanced by the application of different coding techniques, a fact which shows that powerful coding can make the difference under such a hostile medium. The impact of block interleaving is investigated, while the simulation examines how different modulation schemes fair under the imposed channel conditions as well. The performance of the system is assessed by the commonly used bit error rate vs signal‐to‐noise ratio diagrams and there is also a comparison regarding throughput efficiency among all the tested systems. As stated in Section 4, a promising PLC application is attained. Copyright © 2004 John Wiley & Sons, Ltd.
Sequence and embryonic expression of three zebrafish fringe genes: lunatic fringe, radical fringe, and manic fringe
Authors: Qiu Xuehui , Xu Haoying , Haddon Catherine , Lewis Julian , Jiang Yun‐Jin 
Published: September 2004

AbstractDrosophila fringe and its homologues in vertebrates code for glycosyltransferases that modify Notch, altering the sensitivity of this receptor protein to its ligands Delta and Serrate and, thereby, playing an essential part in the demarcation of tissue boundaries. We describe the isolation and characterization of three zebrafish (Danio rerio) fringe homologues: lunatic fringe (lfng), radical fringe (rfng), and manic fringe (mfng). In addition to the sites previously described (Prince et al. [2001] Mech. Dev. 105:175–180; Leve et al. [ 2001] Dev. Genes Evol. 211:493–500), lfng is also expressed in the sensory patches of the inner ear. The newly described rfng is expressed in adaxial cells, tectum, rhombomere boundaries, and formed somites, but the expression of mfng is only detectable by reverse transcription‐polymerase chain reaction and not by whole‐mount in situ hybridization (WISH) during early embryonic development; later, it is expressed in the sensory patches of the ear. In mib mutants, where Notch signaling is defective and rhombomere boundaries fail to form, the rfng expression in hindbrain is almost completely lost. None of the three zebrafish fringe genes is detectably expressed in the posterior presomitic mesoderm, suggesting that, in contrast with chick and mouse, the somitogenesis oscillator in this tissue in the zebrafish does not depend on Fringe activity. Developmental Dynamics 231:621–630, 2004. © 2004 Wiley‐Liss, Inc.
In vivo comparative study of RNAi methodologies by in ovo electroporation in the chick embryo
Authors: Rao M. , Baraban J.H. , Rajaii F. , Sockanathan S. 
Published: September 2004

AbstractThe combination of emergent RNA interference (RNAi) technology with in ovo electroporation in the chick embryo has the potential to provide a powerful and rapid means for functional analyses of novel genes in vivo. In this study, we show that electroporation of short 21‐bp RNA duplexes (siRNAs) is a quick and simple method for silencing exogenous and endogenous gene expression in vivo. Quantitative comparisons with two other RNAi protocols that use long double‐stranded RNA duplexes and endonuclease‐digested duplexes (esiRNAs) demonstrate that siRNAs are significantly more effective at reducing gene expression. Furthermore, we also find that much higher amounts of siRNA are required for silencing of endogenous gene expression relative to plasmid‐borne reporter constructs. In short, these results demonstrate that siRNAs are the most effective type of double‐stranded RNA duplex for silencing gene expression and suggest that there might be important differences between silencing endogenous and exogenous genes. Finally, we review the parameters for each of these RNA‐based methods of RNAi and the controls required to analyze RNAi data in the context of the developing vertebrate embryo. Developmental Dynamics 231:592–600, 2004. © 2004 Wiley‐Liss, Inc.
Connective tissue growth factor expression and Smad signaling during mouse heart development and myocardial infarction
Authors: Chuva De Sousa Lopes Susana M. , Feijen Alie , Korving Jeroen , Korchynskyi Olexander , Larsson Jonas , Karlsson Stefan , Ten Dijke Peter , Lyons Karen M. , Goldschmeding Roel , Doevendans Pieter , Mummery Christine L. 
Published: September 2004

AbstractConnective tissue growth factor (CTGF) is reported to be a target gene of transforming growth factor β (TGFβ) and bone morphogenetic protein (BMP) in vitro. Its physiological role in angiogenesis and skeletogenesis during mouse development has been described recently. Here, we have mapped expression of CTGF mRNA during mouse heart development, postnatal adult life, and after experimental myocardial infarction. Furthermore, we investigated the relationship between CTGF and the BMP/TGFβ signaling pathway in particular during heart development in mutant mice. Postnatally, CTGF expression in the heart became restricted to the atrium. Strikingly, 1 week after myocardial infarction, when myocytes have disappeared from the infarct zone, CTGF and TGFβ expression as well as activated forms of TGFβ but not BMP, Smad effector proteins are colocalized exclusively in the fibroblasts of the scar tissue, suggesting possible cooperation between CTGF and TGFβ during the pathological fibrotic response. Developmental Dynamics 231:542–550, 2004. © 2004 Wiley‐Liss, Inc.
Self‐organization of vertebrate mesoderm based on simple boundary conditions
Authors: Green Jeremy B.A. , Dominguez Isabel , Davidson Lance A. 
Published: September 2004

AbstractEmbryonic development requires cell movements whose coordination is robust and reproducible. A dramatic example is the primary body axis of vertebrates: despite perturbation, cells in prospective axial tissue coordinate their movements to make an elongated body axis. The spatial cues coordinating these movements are not known. We show here that cells deprived of preexisting spatial cues by physical dissociation and reaggregation nonetheless organize themselves into an axis. Activin‐induced cells that are reaggregated into a flat disc initially round up into a ball before elongating perpendicular to the disc. Manipulations of the geometry of the disc and immunofluorescence micrography reveal that the edge of the disc provides a circumferential alignment zone. This finding indicates that physical boundaries provide alignment cues and that circumferential “hoop stress” drives the axial extrusion in a manner resembling late‐involuting mesoderm of Xenopus and archenteron elongation in other deuterostome species such as sea urchins. Thus, a population of cells finds its own midline based on the form of the population's boundaries using an edge‐aligning mechanism. This process provides a remarkably simple organizing principle that contributes to the reliability of embryonic development as a whole. Developmental Dynamics 231:576–581, 2004. © 2004 Wiley‐Liss, Inc.
A Calix[4]arene Monoalkyl Ether as a Model of a Tris(phenolate) Ligand with a Hemilabile Anisole Moiety: Syntheses, Molecular Structures and Bonding of Calix[4]arene Ether Supported Titanium Complexes and Their Catalytic Activity in Epoxidation Reactions
Authors: Friedrich Andreas , Radius Udo 
Published: September 2004

AbstractNew mononuclear titanium complexes [TiCl(Rcalix)] [R = Me (1), Bz (2), SiMe3 (3)] supported by p‐tert‐butylcalix[4]arene mono(organyl)ethers (Rcalix) were prepared in good yield from H2R2calix and [TiCl4(THF)2]. The crystallographically characterized complex [TiCl(Mecalix)] (1) reacts readily with NaCp and LiNR2 to afford the complexes [TiCp(Mecalix)] (4) and [Ti(NR2)(Mecalix)] [R = Me (5), Et (6), iPr (7), Ph (8)], respectively. Reactions of [Ti(NR2)(Mecalix)] (5) with alcohols, phenols and thiols proceed cleanly with amide exchange, as exemplified by the synthesis of [Ti(OR)(Mecalix)] [R = Me (10), iPr (11), tBu (12), 4‐tBuC6H4 (13), 2,6‐iPr2C6H3 (14)], and [Ti(StBu)(Mecalix)] (15). Depending on the steric demand of the ligand coordinated to the [Ti(Mecalix)] complex fragment these compounds are monomeric or dimeric in the solid state, as demonstrated by the molecular structures of monomeric [Ti(OC6H3‐2,6‐iPr2)(Mecalix)] (14) and [Ti(StBu)(Mecalix)] (15), or dimeric [{Ti(OMe)(Mecalix)}2] (10). In all complexes the calix[4]arene ligand adopts an elliptically distorted cone conformation in which the distance of the titanium atom from the anisole oxygen atom varies between 2.342 Å and 2.438 Å for the structurally characterized complexes, with the exception of the Cp complex 4. MP2 calculations on model complexes demonstrate that the titanium−anisole oxygen bond is weak, with a particularly shallow potential energy surface in the region between 2.30 Å and 2.80 Å. The Mecalix ligand system therefore might be described as a tris(phenolate) ligand with a hemilabile anisole group in the titanium compounds reported. Despite the labile anisole ether titanium bond, isomerization of the calix[4]arene ligand to a paco coordination mode, as described earlier for the Me2calix complexes [Ti(OC6H4‐4‐R)2(Me2calix)], has not been observed in these complexes. Preliminary results on the catalytic epoxidation of cyclooctene with TBHP using calix[4]arene‐stabilized titanium(IV) complexes are also briefly presented. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)
Surface Resistance and Potentiometric Response of Polymeric Membranes Doped with Nonionic Surfactants
Authors: Muslinkina Liya , Pretsch Ernö 
Published: September 2004

AbstractThe influence of lipophilic, electrically neutral surfactants added to the membrane on the ion transfer resistance between an aqueous sample and a polymeric ion‐selective membrane has been studied by electric impedance spectroscopy and potentiometry. An increase in the surface resistance and a shift of the apparently super‐Nernstian response to lower sample ion activities has been observed when using the nonpolar bis(2‐ethylhexyl) sebacate as plasticizer.
Microfluidics simulation using adaptive unstructured grids
Authors: Waltz Jacob 
Published: September 2004

AbstractA methodology for microfluidics simulation is presented. The methodology solves the three‐dimensional incompressible Navier–Stokes equations with an adaptive unstructured Finite Element method. A semi‐implicit Fractional Step procedure is used for time integration. The entire methodology has been parallelized for shared‐memory architectures via an algebraic domain decomposition. Results from both verification problems and prototypical applications are included. Copyright © 2004 John Wiley & Sons, Ltd.
Comparative study of lattice‐Boltzmann and finite volume methods for the simulation of laminar flow through a 4:1 planar contraction
Authors: Al‐Jahmany Yarub Y. , Brenner Gunther , Brunn Peter O. 
Published: September 2004

AbstractIn the present paper, a comparative study of numerical solutions for Newtonian fluids based on the lattice‐Boltzmann method (LBM) and the classical finite volume method (FVM) is presented for the laminar flow through a 4:1 planar contraction at a Reynolds number of value one, Re=1. In this study, the stress field for LBM is directly obtained from the distribution function. The calculations of the stress based on the FVM‐data use the evaluations of velocity gradients with finite differences. The stress field for both LBM and FVM is expressed in the present study in terms of the shear stress and the first normal stress difference. The lateral and axial profiles of the velocity, the shear stress and the first normal stress difference for both methods are investigated. It is shown that the LBM results for the velocity and the stresses are in excellent agreement with the FVM results. Copyright © 2004 John Wiley & Sons, Ltd.
Biocompatibility of components of a female controlled drug delivery system
Authors: Warrier Bharat K. , Kostoryz Elisabet , Lee Chi H. 
Published: September 2004

AbstractA female controlled drug delivery system (FcDDS) containing sodium dodecyl sulfate as a microbicide, ethylenediaminetetraacetic acid (EDTA) as a synergistic microbicide, and lactic acid as a pH modulator was developed as an intravaginal barrier device against sexually transmitted diseases. The host response of the vagina to the FcDDS was evaluated through biocompatibility tests including cell viability, estrogenicity, and cytotoxicity assays on HeLa cervical cells and NIH:Ovcar‐3 ovarian cells. Gel electrophoresis and reverse transcriptase polymerase chain reaction assays on HeLa cervical cell lines were also performed to elucidate the effects of EDTA on the expression of particular proteins of interest. The results of the cell viability test showed no significant difference in viability of cells upon exposure to EDTA at concentrations less than 0.035% that was reported to exert spermicidal activity. EDTA at concentrations less than 0.035% did not cause any cytotoxicity. The results of reverse transcriptase polymerase chain reaction analysis revealed that EDTA induced the expression of a 67‐kDa protein in HeLa cells, which was identified as elastin binding protein (a part of the elastin receptor complex). This work has demonstrated that FcDDS containing EDTA is biocompatible and safe to be used as an intravaginal barrier device. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 209–216, 2004