bluuebunny/crossref_metadata_2025 huggingface dataset:
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

A 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

C2F4was 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

The 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.
Optical Spectroscopy of Biomolecular Dynamics
Authors: Vöhringer Peter , Haran Gilad
Published: September 2004

Of visible interest: At the Minerva‐Gentner Symposium on Optical Spectroscopy of Biomolecular Dynamics, which took place between 21st and 25th March 2004 at Banz, Germany, scientists from many disciplines came together to compare the study of single molecules to that of ensembles. Fluorescent proteins, time‐resolved IR, and protein folding dynamics were among the main topics discussed.
Structural Phase Transitions in Heavy Alkali Metals Under Pressure
Authors: Osorio‐Guillén Jorge M. , Ahuja Rajeev , Johansson Börje
Published: September 2004

We 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.
Cover Picture: Photostability of Isolated and Paired Nucleobases: NH Dissociation of Adenine and Hydrogen Transfer in its Base Pairs Examined by Laser Spectroscopy (ChemPhysChem 9/2004)
Authors: Hünig Isabel , Plützer Christian , Seefeld Kai A. , Löwenich Dennis , Nispel Michael , Kleinermanns Karl
Published: September 2004

The cover picture shows an artist's view of the interaction of the DNA α helix with light. Prebiotic chemistry supposedly happened under conditions of intense short wavelength radiation without UV‐absorbing oxygen or ozone layer. UV photostability may have been an important factor for the evolutionary selection of the DNA bases besides their capability to form strong hydrogen bonds. The apparent photostability of the genetic code has been ascribed to fast internal conversion of the electronically excited DNA bases to the electronic ground state via doorway states. The results presented on page 1427 by Hünig et al. point to NH dislocation as important pathway to convert photoexcitation of DNA to innoxious heat in the condensed phase.
Attitudes and use of homework assignments in therapy: a survey of German psychotherapists
Authors: Fehm Lydia , Kazantzis Nikolaos
Published: September 2004

There 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

Orthogonal 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.
Temporal price dispersion: Evidence from an online consumer electronics market
Authors: Baye Michael R. , Morgan John , Scholten Patrick
Published: September 2004

Economic theory indicates that e-retailers competing at price comparison sites, such as Shopper.com, must charge prices that cannot be systematically predicted by their rivals. Consistent with theory, we find significant variation in the identity of the low-price firm as well as the level of the lowest price for 36 of the best-selling consumer electronics products sold at Shopper.com between November 1999 and May 2001.The observed pricing patterns can be explained by firms engaging in short-term price promotions in an attempt to avoid the deleterious outcome associated with price competition. Based on our arguments and the evidence presented, the managerial implications are clear: Strategic unpredictability in prices—through the use of hit and run sales—is a widely used and effective weapon for avoiding all-out price competition in online markets.
The influence of pre- and post-purchase service on prices in the online book market
Authors: Cao Yong , Gruca Thomas S.
Published: September 2004

We examine the ability of customer ratings of pre-purchase and post-purchase service to explain price variations in the online book market. In addition, we test whether market leaders leverage their branding advantage by charging higher prices. E-tailer prices were modeled using a market basket of identical books whose posted prices were sampled repeatedly over a 4-month period. Contrary to expectations, posted prices were relatively constant across the time period that included a highly competitive 2000 holiday selling season. E-tailers whose customers were more satisfied with the level of post-purchase service charged significantly higher prices. Differences in satisfaction with pre-purchase service did not explain price differences across all e-tailers. The higher prices of the three market leaders were most likely due to higher satisfaction ratings for both pre- and post-purchase satisfaction. We discuss the implications of these results for managers and academics.
Price dispersion on the internet: A review and directions for future research
Authors: Pan Xing , Ratchford Brian T. , Shankar Venkatesh
Published: September 2004

The explosive growth in Internet retailing has sparked a stream of research on online price dispersion, defined as the distribution of prices (such as range and standard deviation) of an item with the same measured characteristics across sellers of the item at a given point in time. In this paper, we review the empirical and analytical literature on online price dispersion and outline the future directions in this research stream. We address the issue of whether price dispersion is greater or smaller online than off-line, examine whether price dispersion on the Internet has changed over time, discuss multichannel retailing and measurement of price dispersion, explore why Internet price dispersion exists, and investigate the drivers of online price dispersion.
Auction fever: The effect of opponents and quasi-endowment on product valuations
Authors: Heyman James E. , Orhun Yesim , Ariely Dan
Published: September 2004

The wide adoption of dynamic second-price auctions as the format of choice for Internet-based (online) transactions has created an interest in understanding how individuals behave in such environments. The current work concentrates on two dynamic effects, which we call quasi-endowment and opponent effect, and finds that these effects may result in over-bidding. The results of two experimental auctions—one involving hypothetical bids and the other real-money bids—demonstrate that bids reflect valuations that include the nonnormative influences of the two factors. Quasi-endowment and opponent effects could lead to the behaviors of repeated bidding and sniping commonly observed in second-price online auctions such as eBay.
Measuring individual frictional costs and willingness-to-pay via name-your-own-price mechanisms
Authors: Spann Martin , Skiera Bernd , Schäfers Björn
Published: September 2004

Name-your-own-price is a pricing mechanism where the buyer instead of the seller determines the price, because the buyer makes a bid at a certain price, which the seller can either accept or reject. Based on consumers’ bidding behavior at a name-your-own-price seller, we develop and empirically test a model to simultaneously estimate individual willingness-to-pay (WTP) and frictional costs. Further, we compare analytically and empirically bidding behavior and profit implications of the single bid model to those of the repeated bidding model. Thereby, we derive closed form solutions for the optimal bids which describe the influence of willingness-to-pay and frictional costs on consumer's bidding behavior. In addition, we develop a procedure for estimating empirically willingness-to-pay and frictional costs for individual consumers. Finally, we discuss the findings and limitations as well as their implications for providers of name-your-own-price mechanisms.
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

Drosophila 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

The 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

Connective 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

Embryonic 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

New 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

The 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

A 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

In 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

A 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
Thermoreversible hydrogel scaffolds for articular cartilage engineering
Authors: Fisher John P. , Jo Seongbong , Mikos Antonios G. , Reddi A. Hari
Published: September 2004

Articular cartilage has limited potential for repair. Current clinical treatments for articular cartilage damage often result in fibrocartilage and are associated with joint pain and stiffness. To address these concerns, researchers have turned to the engineering of cartilage grafts. Tissue engineering, an emerging field for the functional restoration of articular cartilage and other tissues, is based on the utilization of morphogens, scaffolds, and responding progenitor/stem cells. Because articular cartilage is a water‐laden tissue and contains within its matrix hydrophilic proteoglycans, an engineered cartilage graft may be based on synthetic hydrogels to mimic these properties. To this end, we have developed a polymer system based on the hydrophilic copolymer poly(propylene fumarate‐co‐ethylene glycol) [P(PF‐co‐EG)]. Solutions of this polymer are liquid below 25°C and gel above 35°C, allowing an aqueous solution containing cells at room temperature to form a hydrogel with encapsulated cells at physiological body temperature. The objective of this work was to determine the effects of the hydrogel components on the phenotype of encapsulated chondrocytes. Bovine articular chondrocytes were used as an experimental model. Results demonstrated that the components required for hydrogel fabrication did not significantly reduce the proteoglycan synthesis of chondrocytes, a phenotypic marker of chondrocyte function. In addition, chondrocyte viability, proteoglycan synthesis, and type II collagen synthesis within P(PF‐co‐EG) hydrogels were investigated. The addition of bone morphogenetic protein‐7 increased chondrocyte proliferation with the P(PF‐co‐EG) hydrogels, but did not increase proteoglycan synthesis by the chondrocytes. These results indicate that the temperature‐responsive P(PF‐co‐EG) hydrogels are suitable for chondrocyte delivery for articular cartilage repair. © 2004 Wiley Periodicals, Inc. J Biomed Mater Res 71A: 268–274, 2004
Theoretical study on reaction mechanism of the fluoromethylene radical with nitrogen dioxide
Authors: Zhang Jia‐Xu , Liu Jing‐Yao , Li Ze‐Sheng , Sun Chia‐Chung
Published: September 2004

The complex doublet potential energy surface for the reaction of 1CHF with NO2, including 14 minimum isomers and 30 transition states, is explored theoretically at the B3LYP/6‐311G(d,p) and CCSD(T)/6‐311G(d,p) (single‐point) levels of theory. The initial association between 1CHF and NO2 is found to be the carbon‐to‐middle‐nitrogen attack forming an energy‐rich adduct a (HFCNO2) with no barrier, followed by concerted O‐shift and CN bond rupture leading to product P2 (NO + HFCO), which is the most abundant. In addition, a can take a 1,3‐H‐shift to isomer b (FCN(O)OH) followed by the dissociation to form the second feasible product P4 (OH + FCNO). The least favorable pathway is that b undergoes a concerted OH‐shift to form d (HO(F)CNO), which will dissociate to product P5 (HF+OCNO) via side HF‐elimination. The secondary dissociation of P5 may form product P7 (HF+NO+CO) easily. Furthermore, the 1CHF attack at the end‐O of NO2 is a barrier‐consumed process, and thus may only be of significance at high temperatures. The comparison with the analogous reactions 1CHCl + NO2 is discussed. The present study may be helpful for probing the mechanism of the title reaction and understanding the halogenated carbine chemistry. © 2004 Wiley Periodicals, Inc. J Comput Chem 25: 1888–1894, 2004
Noah Porter's problem and the origins of American psychology
Authors: Richards Graham
Published: September 2004

The twin problems facing nineteenth‐century American “mental and moral philosophy” of the nature of psychological language and the constraints that religious beliefs placed on possibilities of innovation in a “scientific Psychology” are both highly visible in the work of Noah Porter, who was unable to resolve them. They are also more covertly identifiable in the works of James McCosh and others in this school. It is suggested that the transition to the “New Psychology” of the 1880s and 1890s needs to be rethought in light of this in three respects: (a) ironically, it entailed repressing insights into the psychological language problem, (b) the legacy of the religious factor profoundly affected U.S. Psychology and played a less unambiguously negative role in its fortunes than customarily portrayed, and (c) the transition was itself a more complex and protracted process than is portrayed in traditional “revolutionary” accounts. © 2004 Wiley Periodicals, Inc.
Riding natural scientists' coattails onto the endless frontier: The SSRC and the quest for scientific legitimacy
Authors: Solovey Mark
Published: September 2004

This article proposes that the postwar National Science Foundation (NSF) debate constituted a critical, transitional episode in American social science and partisan politics. I show that by responding to powerful conservative critics in the scientific and political communities, the Social Science Research Council's (SSRC's) leading scholars (re)asserted a contested scientistic strategy—to advance the social sciences by following the natural sciences. Further, I reconstruct a wider and longer framework of analysis in order to recover central challenges to the scientistic strategy raised by prominent liberal scholars who rejected the associated commitments to value neutrality and disinterested professionalism. In developing this framework for understanding the contrasting fortunes of each strategy, this article argues that the NSF debate has a deep historical significance—for the social sciences, for American liberalism, and for the nation. © 2004 Wiley Periodicals, Inc.
Stereocontrolled synthesis of (7E,9Z)‐[9,10‐2H]‐conjugated linoleic acid
Authors: Broustal Garance , Loreau Olivier
Published: September 2004

To study the metabolism of minor conjugated linoleic acid isomers (CLAs), (7E,9Z)‐[9,10‐2H] CLA was prepared in three steps from a conjugated enyne precursor. In the labelling step, deuterium atoms were introduced by partial reduction of the triple bond using deuterated disiamylborane and acetic acid‐d4. Deuterated (7E,9Z) CLA was obtained with high isotopic enrichment (>99%) and purity greater than 95%. Copyright © 2004 John Wiley & Sons, Ltd.
Microwave‐enhanced, solvent‐free synthesis of singly and doubly 13C‐labelled trans‐cinnamic acid at the α‐ and β‐carbon positions
Authors: Ma Guibin , Hayes Sophia E.
Published: September 2004

13C‐labelled trans‐cinnamic acid (3‐phenyl‐2‐propenoic acid) has been synthesized in one step using benzaldehyde‐carbonyl‐13C and malonic acid‐2‐13C in the presence of ammonium acetate under microwave irradiation and solvent‐free conditions. Copyright © 2004 John Wiley & Sons, Ltd.
Direct transdifferentiation gives rise to the earliest new hair cells in regenerating avian auditory epithelium
Authors: Roberson David W. , Alosi Julie A. , Cotanche Douglas A.
Published: September 2004

The avian auditory epithelium is capable of complete regeneration after hair cell (HC) loss. Most new HCs arise via cell division, but approximately one‐third of new HCs arise via direct transdifferentiation (DT), in which supporting cells (SCs) alter their phenotype without dividing. In this study, we used synchronous, gentamicin‐induced near‐total HC loss in the basal end of the epithelium and continuous infusion of the cell division marker bromodeoxyuridine (BrdU) to identify the origin of each individual regenerating HC. Early new HCs were identified by immunolabeling for the HC‐specific marker myosin‐VIIa, and mitotic cells with BrdU immunolabeling. The first new HCs arising via DT appear 72–96 hr after gentamicin, 24–48 hr earlier than the first new mitotic HCs. After Day 6, however, most new HCs are mitotic. The “intermediate” morphology that has been suggested to be characteristic of DT is seen in HCs arising via both pathways. These findings suggest that DT is a simpler, more rapid process that produces the first new HCs, and that mitotic regeneration is somewhat slower but ultimately produces most new HCs. The identical morphology of regenerating HCs from both pathways suggests that once HC fate is established, all new HCs follow similar cellular processes during differentiation and reorganization into the regenerated epithelium. © 2004 Wiley‐Liss, Inc.
Finding yourself: How social identity affects leadership
Authors: Ruderman Marian N. , Ernst Christopher
Published: September 2004

In today's increasingly volatile and complex organizational environment, it's as important as ever for leaders to understand themselves. But it's no longer enough for them to be aware of their capabilities, motivations, styles, and values. Leaders now must also gain knowledge of their social identities—their membership in certain social groups defined by categories such as gender, race, and religion and the implications of belonging to these groups.
Investigation of the Interpolymer Complex between Hydroxypropyl Cellulose and Maleic Acid‐Styrene Copolymer, 1
Authors: Bumbu Gina‐Gabriela , Vasile Cornelia , Eckelt John , Wolf Bernhard A.
Published: September 2004

Summary: The hydrogen bonding‐interpolymer association of hydroxypropyl cellulose (HPC) with maleic acid‐styrene (MAc‐S) copolymer has been investigated in dilute aqueous solution by viscometry, turbidimetry and potentiometry. At a mixing ratio between MAc‐S and HPC of 10:90, the solution exhibits a phase separation upon heating, while for other mixing ratio no phase separation could be detected. The stability of the interpolymer complex (IPC) increases as the temperature rises. The stoichiometry of the IPC, in mole units, was estimated as being MAc‐S:HPC = 5:2. The thermodynamic functions (enthalpy and entropy) of the complexation process have been determined.

Dependence of IPC concentration in H2O/MAc‐S/HPC system on the mole fraction of MAc‐S in polymer mixture at different temperatures.

magnified image

Dependence of IPC concentration in H2O/MAc‐S/HPC system on the mole fraction of MAc‐S in polymer mixture at different temperatures.
Cover Picture: Macromol. Chem. Phys. 14/2004
Authors: Yoo Youngjae , Choi Kil‐Yeong , Lee Jae Heung
Published: September 2004

Cover: The picture on the cover shows a schematic representation of the procedure for formation of polycarbonate/MMT nanocomposites via microwave‐aided solid state polymerization.

Further details can be found in the Full Paper by Y. Yoo, K.‐Y. Choi, and J. H. Lee* on page 1863.
A Physical Method of Fabricating Hollow Polymer Spheres Directly from Oil/Water Emulsions of Solutions of Polymers
Authors: Kim Young Baek , Yoon Kyung‐Sup
Published: September 2004

Summary: A new physical method of fabricating hollow spheres from different polymers has been developed. In this method, emulsions were prepared by mixing organic solutions of polystyrene, poly(D,L‐lactide‐co‐glycolide) (PLGA), and bacterial poly(3‐hydroxybutyrate‐co‐3‐hydroxyvalerate) (PHBV), water, and surfactants. The evaporation of solvents at room temperature caused a phase separation that eventually yielded hollow spheres. Molecular weights, concentrations of polymers, and the natures of surfactant and solvent were important aspects of hollow sphere formation and structure. A mechanism for the formation of hollow spheres is proposed based on observations made using an optical microscope equipped with a digital camcorder and using scanning electron microscopy images of hollow spheres obtained under different conditions.

A scanning electron microscopy image of a broken smaller hollow sphere prepared using a 7 wt.‐% polystyrene solution (diameter of the sphere ∼10 micrometers).

magnified image

A scanning electron microscopy image of a broken smaller hollow sphere prepared using a 7 wt.‐% polystyrene solution (diameter of the sphere ∼10 micrometers).
Mapping Acid‐Catalyzed Deprotection in Thin Polymer Films: Fluorescence Imaging Using Prefluorescent 7‐Hydroxycoumarin Probes
Authors: Frenette Mathieu , Coenjarts Chris , Scaiano J. C.
Published: September 2004

Summary: Fluorescent images that illustrate acid‐catalyzed tert‐butoxycarbonyl (tBoc) deprotection patterns in polymer films were obtained using fluorescent sensors based on 7‐hydroxycoumarin dyes. Three commercial 7‐hydroxycoumarins, which are highly fluorescent, become practically nonemissive upon protection of the 7‐hydroxyl position with tBoc. In thin polymer films, the protected “prefluorescent” probes can return to their deprotected, fluorescent states by reaction with catalytic amounts of photogenerated acid and mild heating.

Protected probes become highly fluorescent after acid‐induced deprotection.

magnified image

Protected probes become highly fluorescent after acid‐induced deprotection.
1H and 13C assignments of two new triterpenes from Cladocolea grahami
Authors: Rios María Yolanda , Aguilar‐Guadarrama A. Berenice
Published: September 2004

The structure elucidation and 1H and 13C assignments of the new triterpenes 3β‐palmitoxy‐7β‐hydroxyolean‐12‐ene (1) and its hydrolysis product 3β,7β‐dihydroxyolean‐12‐ene (2) and 3β‐sn‐glyceroyl‐(1″‐palmitoxy)urs‐12‐ene (3), isolated from the aerial parts of Cladocolea grahami (Loranthaceae), are reported. Copyright © 2004 John Wiley & Sons, Ltd.
A 3D finite element simulation model for TBM tunnelling in soft ground
Authors: Kasper Thomas , Meschke Günther
Published: September 2004

A three‐dimensional finite element simulation model for shield‐driven tunnel excavation is presented. The model takes into account all relevant components of the construction process (the soil and the ground water, the tunnel boring machine with frictional contact to the soil, the hydraulic jacks, the tunnel lining and the tail void grouting). The paper gives a detailed description of the model components and the stepwise procedure to simulate the construction process. The soil and the grout material are modelled as saturated porous media using a two‐field finite element formulation. This allows to take into account the groundwater, the grouting pressure and the fluid interaction between the soil and slurry at the cutting face and between the soil and grout around the tail void. A Cam‐Clay plasticity model is used to describe the material behaviour of cohesive soils. The cementitious grouting material in the tail void is modelled as an ageing elastic material with time‐dependent stiffness and permeability. To allow for an automated computation of arbitrarily long and also curvilinear driving paths with suitable finite element meshes, the simulation procedure has been fully automated. The simulation of a tunnel advance in soft cohesive soil below the ground water table is presented and the results are compared with measurements taken from the literature. Copyright © 2004 John Wiley & Sons, Ltd.
Modification of polystyrene properties through grafting with N‐vinylcarboxamido‐2‐methylpropane sulfonic acid monomer
Authors: Aggour Y A
Published: September 2004

Polystyrene (PS) possesses good mechanical properties, but its surface is relatively inert and hydrophobic. Grafting of N‐vinylcarboxamido‐2‐methylpropane sulfonic acid (VCMP) is useful to hydrophilize the PS surface. Grafting was performed using benzoyl peroxide (BPO) as an initiator in toluene:methanol solvent mixture (3:1 volume ratio). The influence of the main factors on grafting, such as temperature, time, concentrations of initiator, PS and VCMP, has been studied. The results show that the initial rate of polymerization and percentage of grafting are enhanced by increased temperature. Furthermore, the specific rate constants of the first order reaction/are determined, and the activation energy of the grafting reaction is estimated. The grafting parameters are established and a suitable mechanism of the reaction is proposed. The grafted PS is to characterized through infrared spectra, intrinsic viscosity, thermogravimetric analysis (TGA) and differential gravimetric analysis (DTG). The kinetics of thermal degradation and the order of the thermal stabilities are given. Also the decomposition activation energies of the thermal degradation are determined, and confirm the thermal stabilities of the polymers used.

© 2004 Society of Chemical Industry
Solvatochromism of dyes. Part IV—Energetic characteristics of merocyanine derivatives of 1‐phenyl‐2‐[2‐(3‐X‐4‐hydroxy‐5‐R‐phenyl)ethenyl]‐3,3‐dimethyl‐3H‐indolium cation
Authors: Wróblewska Elwira K. , Soroka Jacek A. , Soroka Krystyna B. , Ga̧siorowska Monika
Published: September 2004

The fundamental energetic parameters (intercepts and slopes of straight lines approximating energetic levels) of solvatochromic betaines generated by deprotonation of 2‐(4‐hydroxystyryl)‐3H‐indolium salts were determined from solvatochromic data in one‐component solvents. It was demonstrated that the solvatochromism of the investigated dyes can be described by the VBHB (vinylogous amide–betaine–hydrogen‐bonded betaine) physical model. In comparison with similar dyes, the ability to form hydrogen‐bonded solvates is weaker owing to the higher acidity of the dye precursor used. The type of observed solvatochromism was determined. Copyright © 2004 John Wiley & Sons, Ltd.
Angiopoietin 2 expression is related to histological grade, vascular density, metastases, and outcome in prostate cancer
Authors: J:son Lind Anna , Wikström Pernilla , Granfors Torvald , Egevad Lars , Stattin Pär , Bergh Anders
Published: September 2004

BACKGROUND

In several malignant tissues, the angiopoietins are principal regulators of vascular growth and regression, but in normal prostate and prostate tumors the role of the angiopoietins is unknown.

METHODS

Angiopoietin (ang) 1 and 2 were immunolocalized in TUR‐diagnosed prostate tumors with long follow‐up and the expression was related to vascular density and clinopathological variables.

RESULTS

Ang 1 was strongly expressed in the basal epithelial cell layer in non‐malignant tissue, whereas tumors had lower levels localized to the epithelial cells. A weak ang 2 immu‐noreaction was observed in non‐malignant tissue and in low to intermediate Gleason score (GS) tumors, with a similar expression pattern. However, most high GS tumors showed an intense ang 2 staining. Ang 2 was significantly correlated to GS, density of endoglin stained blood vessels, metastases, and to cancer specific survival.

CONCLUSIONS

We conclude that ang 2 probably is an important regulator of angiogenesis in prostate cancer. © 2004 Wiley‐Liss, Inc.
11th International Conference on Phonon Scattering in Condensed Matter (Phonons 2004), St. Petersburg, Russia, 25–30 July 2004
Authors: Kent A. J.
Published: September 2004

Conference Reports are meant to offer an authoritative view on a recently held scientific meeting rather than a comprehensive list of the conference presentations. Authors are invited to describe what they feel were the most interesting contributions.

The full Proceedings of the 11th International Conference on Phonon Scattering in Condensed Matter (Phonons 2004) will be published in phys. stat. sol. (c) in early 2005.
Training ACD/LogP with Experimental Data
Authors: Walker Matthew J.
Published: September 2004

The commercial physical property calculation software, ACD/Labs Physico‐Chemical Laboratory, has the capability to accept experimental data for logP and pKa values which it can use to “train” its model to better predict un‐represented structural classes. An attempt was made to produce a training set, called a “user database” by the software, based on Merck in‐house data, which could be used to train the ACD/LogP model in order to achieve better predictivity on molecules of interest to Merck researchers. A user database consisting of a randomly selected 10% subset of the available Shake‐Flask measured logP data was constructed and used to predict itself as well as the remaining 90% data set. The training produced a modest increase in accuracy of the model, with the R2 value of the prediction improving in the test set from 0.316 to 0.527. Narrowing the selection to a project‐based, targeted subset of the in‐house data in hopes of decreasing the diversity of the set, enhanced the coverage of the model but only produced an improvement in the R2 value from 0.350 to 0.537. Finally, training on a single, small representative of a structural class produced a sizable reduction in the bias of the prediction in a congeneric series of compounds, essentially confirming the original claim of the software developers. These improvements came with an increase in time and machine load to perform the calculation relative to the size of the training set.
Feeding fish with diets of different ratios of C3‐ and C4‐plant‐derived ingredients: a laboratory analysis with implications for the back‐calculation of diet from stable isotope data
Authors: Focken Ulfert
Published: September 2004

Back‐calculation of the diet is one of the most frequent applications of stable isotope techniques in animal ecology. These calculations are often based on two assumptions: a constant trophic shift for all dietary items and a linear response of the isotopic ratios to different mixtures of two isotopically distinct feeds. In a laboratory experiment, fish (Nile tilapia, Oreochromis niloticus) were fed semi‐synthetic diets prepared either from wheat or corn ingredients, or from three blended diets (25, 50, 75% wheat components). Isotopic analysis of the lipid‐free and lipid fraction of the fish after the experiment revealed that the trophic shift was not constant for wheat‐ and corn‐based diets. The isotopic response to the mixed diets was not linear, leading to a statistically significant over‐estimation of the corn component in the back‐calculation. Both effects are in agreement with published data on the isotopic effects of C3‐ and C4‐plant materials in the diet. Copyright © 2004 John Wiley & Sons, Ltd.