bluuebunny/crossref_metadata_2025_split huggingface dataset:
Kinetic aspects of flocculation by cationic polymers
Authors: Gregory John , Sheiham Ivan 
Published: March 2007

AbstractFlocculation of latex particles by a series of cationic polymers has been investigated, with special attention being paid to the effect of particle concentration. Both initial rate and ultimate extent of flocculation have been examined over a range of polymer concentrations, so that the onset of flocculation and of restabilisation could be established. At low particle concentrations, the effect of the polymers seems to be predominantly charge neutralisation; even high molecular weight polymers do not appear to form ‘bridges’, presumably because of the relatively flat configuration of the adsorbed polymer chains. However, at high particle concentrations, bridging flocculation may occur because adsorbed polymer chains require a finite time to attain their equilibrium configuration.Some practical implications of these findings are briefly discussed.
An X‐ray study on the needle‐like crystal of polyoxymethylene grown in a solution polymerisation system
Authors: Iguchi M. , Murase I. , Watanabe K. 
Published: March 2007

AbstractNeedle‐like crystals of polyoxymethylene, grown in a polymerisation system of trioxane in solution with a cationic catalysis and considered to be single‐crystals of extended‐chains, were investigated by means of X‐ray diffraction. As for the molecular orientation in the crystal, a typical ‘fibre‐pattern’ with c‐axis oriented along the length was obtained from a specimen in which needles were embedded and aligned in a resin matrix. The degree of crystallinity, estimated from the diffraction diagram, was practically 100% (or not less than 95%) and the peak width of crystalline reflections, as narrow as a crystal of low molecular weight substance. Periodicity, as is seen in lamellar‐type crystals, was not observed by X‐ray scattering at small angle. The density measured was in a range, between 1.493 and 1.505, which was not different from the theoretical density.
Studies of the reactions of anhydrosulphites of α‐hydroxy acids, part IX. thermal polymerisation of anhydrosulphites of α‐hydroxy α‐methyl carboxylic acids
Authors: Crowe Alec J. , Tighe Brian J. 
Published: March 2007

AbstractThe anhydrosulphites of a series of unsymmetrically substituted α‐hydroxy acids have been prepared and their susceptibility to polymerisation by thermal decomposition studied. The first order rate determining ring scission process, leading to the formation of a reactive α‐lactone intermediate which then undergoes spontaneous polymerisation, is the predominant mechanism even with substituents up to C8. As the length of the n‐alkyl substituent is increased the rate of decomposition and thus polymerisation increases until a plateau value is reached at around C3. Further increase in substituent length decreases the rate of decomposition, an effect which is attributed to steric hindrance of the leaving group by long (C6—C8) substituents.
Rheology and product properties in injection moulding
Authors: Sleeman Michael J. , West George H. 
Published: March 2007

AbstractThe types of flow occurring in the runner, gate and cavity of a cylindrical bar mould have been investigated and the relation between the flow and local modulus of the moulding determined for crystal polystyrene. The results suggest that non‐isothermal shear flow was occurring in the runner while the gate displayed the characteristics of shear flow when heated to the polymer melt temperature and a complex type of flow when cold. The cavity was found, under normal injection rates, to fill by a jetting mechanism which often produced surface irregularities in the product and progressive filling from the gate was only observed at low injection rates.Investigation of local moulding properties revealed that while considerable variations within a specimen existed, these were apparently not due to the mould filling mechanism. They have been attributed tentatively to the small opening of the mould which takes place during injection and to cooling strain.
Continuous dopaminergic stimulation in Parkinson's disease
Authors: Silverdale Monty 
Published: March 2007

AbstractCurrent treatments for Parkinson's disease (PD) are plagued by motor complications. Here these underlying motor complications are briefly reviewed, and strategies to reduce them are discussed.The rationale behind the use of continuous dopaminergic stimulation is highlighted as this is a strategy that may reduce motor complications and improve the quality of life for patients with PD. Copyright © 2007 Wiley Interface Ltd
Primhe: primary care mental health & education
Authors: Ashworth Mark , Lyons Christina , Baguley Clare , Fisher Denise 
Published: March 2007

AbstractPSYCHLOPS: a patient‐centred outcome measureA group of practitioners who felt existing psychological outcome measures were not sensitive to the emotional complexities of their caseload set about developing a measure themselves. Here the group Chair describes their progress.Workforce development and mental health service deliveryThe authors describe a novel collaboration that moves away from traditional contracting procedures, with PCTs and SHAs working in partnership with education providers to facilitate and implement a new role in primary care mental health services. Copyright © 2007 Wiley Interface Ltd
Steric effects on the mechanism of reaction of nucleophilic substitution of β‐substituted alkoxyvinyl trifluoromethyl ketones with four secondary amines
Authors: Vdovenko Sergey I. , Gerus Igor I. , Kukhar Valery P. 
Published: March 2007

AbstractThe kinetics of the reaction of β‐substituted β‐alkoxyvinyl trifluoromethyl ketones R1O‐CR2CH‐COCF3 (1a–e) [(1a), R1C2H5, R2H; (1b), R1R2CH3; (1c), R1C2H5, R2C6H5; (1d), R1C2H5, R2V−pNO2C6H4; (1e), R1C2H5, R2C(CH3)3] with four aliphatic amines (2a–d) [(2a), (C2H5)2NH; (2b), (i‐C3H7)2NH; (2c), (CH2)5NH; (2d), O(CH2CH2)2NH] was studied in two aprotic solvents, hexane and acetonitrile. The least reactive stereoisomeric form of (1a–d) was the most populated (E‐s‐Z‐o‐Z) form, whereas in (1e), the more reactive form (Z‐s‐Z‐o‐Z) dominated. The reactions studied proceeded via common transition state formation whose decomposition occurred by ‘uncatalyzed’ and/or ‘catalyzed’ route. Shielding of the reaction centre by bulky β‐substituents lowered abruptly both k′ (‘uncatalyzed’ rate constant) and k″ (‘catalyzed’ rate constant) of this reaction. Bulky amines reduced k″ to a greater extent than k′ as a result of an additional steric retardation to the approach of the bulky amine to its ammonium ion in the transition state. An increase in the electron‐withdrawing ability of the β‐substituent increased ‘uncatalyzed’ k′ due to the acceleration of the initial nucleophile attack (k1) and ‘uncatalyzed’ decomposition of transition state (k2) via promoting electrophilic assistance (through transition state 8). The amine basicity determined the route of the reaction: the higher amine basicity, the higher k3/k2 ratio (a measure of the ‘catalyzed’ route contribution as compared to the ‘uncatalyzed’ process) was. ‘Uncatalyzed’ route predominated for all reactions; however in polar acetonitrile the contribution of the ‘catalyzed’ route was significant for amines with high pKa and small bulk. Copyright © 2007 John Wiley & Sons, Ltd.
Strategies to search and design stabilizers of protein–protein interactions: A feasibility study
Authors: Block Peter , Weskamp Nils , Wolf Alexander , Klebe Gerhard 
Published: March 2007

AbstractSince protein–protein interactions play a pivotal role in the communication on the molecular level in virtually every biological system and process, the search and design for modulators of such interactions is of utmost importance. In recent years many inhibitors for specific protein–protein interactions have been developed, however, in only a few cases, small and druglike molecules are able to interfere in the complex formation of proteins. On the other hand, there are several small molecules known to modulate protein–protein interactions by means of stabilizing an already assembled complex. To achieve this goal, a ligand is binding to a pocket, which is located rim‐exposed at the interface of the interacting proteins, for example as the phytotoxin Fusicoccin, which stabilizes the interaction of plant H+‐ATPase and 14‐3‐3 protein by nearly a factor of 100. To suggest alternative leads, we performed a virtual screening campaign to discover new molecules putatively stabilizing this complex. Furthermore, we screen a dataset of 198 transient recognition protein–protein complexes for cavities, which are located rim‐exposed at their interfaces. We provide evidence for high similarity between such rim‐exposed cavities and usual ligands accommodating active sites of enzymes. This analysis suggests that rim‐exposed cavities at protein–protein interfaces are druggable binding sites. Therefore, the principle of stabilizing protein–protein interactions seems to be a promising alternative to the approach of the competitive inhibition of such interactions by small molecules. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Four‐body contact potentials derived from two protein datasets to discriminate native structures from decoys
Authors: Feng Yaping , Kloczkowski Andrzej , Jernigan Robert L. 
Published: March 2007

AbstractTwo‐body inter‐residue contact potentials for proteins have often been extracted and extensively used for threading. Here, we have developed a new scheme to derive four‐body contact potentials as a way to consider protein interactions in a more cooperative model. We use several datasets of protein native structures to demonstrate that around 500 chains are sufficient to provide a good estimate of these four‐body contact potentials by obtaining convergent threading results. We also have deliberately chosen two sets of protein native structures differing in resolution, one with all chains' resolution better than 1.5 Å and the other with 94.2% of the structures having a resolution worse than 1.5 Å to investigate whether potentials from well‐refined protein datasets perform better in threading. However, potentials from well‐refined proteins did not generate statistically significant better threading results. Our four‐body contact potentials can discriminate well between native structures and partially unfolded or deliberately misfolded structures. Compared with another set of four‐body contact potentials derived by using a Delaunay tessellation algorithm, our four‐body contact potentials appear to offer a better characterization of the interactions between backbones and side chains and provide better threading results, somewhat complementary to those found using other potentials. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Identification of novel fragment compounds targeted against the pY pocket of v‐Src SH2 by computational and NMR screening and thermodynamic evaluation
Authors: Taylor Jonathan D. , Gilbert Philip J. , Williams Mark A. , Pitt William R. , Ladbury John E. 
Published: March 2007

AbstractDiscovery of small molecule inhibitors of protein–protein interactions is a major challenge to pharmaceutical development. Fragment‐based approaches have begun to be widely adopted as an effective way of exploring chemical space on a protein surface with reduced library size. On completion of a fragment screen, the subsequent selection of appropriate “hit” molecules for development is a key decision point. Thermodynamic parameters can be used in this decision process. In this work, a fragment identification protocol based on a virtual fragment analysis and selection followed by 19F NMR screening was directed at the phosphotyrosine binding site of the Src SH2 domain. Three new ligands were identified. Isothermal titration calorimetry was used to provide thermodynamic parameters for the physiologically relevant ligand and the selected fragments. One of these fragments possesses a highly favorable enthalpic contribution to complex formation compared to other fragments and to the physiologically relevant ligand suggesting that it would make a good candidate for compound development. Proteins 2007. © 2007 Wiley‐Liss, Inc.
The bioactive conformation of glucose‐dependent insulinotropic polypeptide by NMR and CD spectroscopy
Authors: Alaña Iñigo , Malthouse J. Paul G. , O'Harte Finbarr P. M. , Hewage Chandralal M. 
Published: March 2007

AbstractGlucose‐dependent insulinotropic polypeptide (GIP) is a gastrointestinal incretin hormone, which modulates physiological insulin secretion. Because of its glucose‐sensitive insulinotropic activity, there has been a considerable interest in utilizing the hormone as a potential treatment for type 2 diabetes. Structural parameters obtained from NMR spectroscopy combined with molecular modeling techniques play a vital role in the design of new therapeutic drugs. Therefore, to understand the structural requirements for the biological activity of GIP, the solution structure of GIP was investigated by circular dichroism (CD) followed by proton nuclear magnetic resonance (NMR) spectroscopy. CD studies showed an increase in the helical character of the peptide with increasing concentration of trifluoroethanol (TFE) up to 50%. Therefore, the solution structure of GIP in 50% TFE was determined. It was found that there was an α‐helix between residues 6 and 29, which tends to extend further up to residue 36. The implications of the C‐terminal extended helical segment in the inhibitory properties of GIP on gastric acid secretion are discussed. It is shown that the adoption by GIP of an α‐helical secondary structure is a requirement for its biological activity. Knowledge of the solution structure of GIP will help in the understanding of how the peptide interacts with its receptor and aids in the design of new therapeutic agents useful for the treatment of diabetes. Proteins 2007. © 2007 Wiley‐Liss, Inc.
Study of ordinary chondrites by Mössbauer spectroscopy with high velocity resolution: identification of M1 and M2 sites in silicate phases
Authors: Zhiganova E. V. , Grokhovsky V. I. , Oshtrakh M. I. 
Published: March 2007

AbstractStudy of ordinary chondrites by Mössbauer spectroscopy with high velocity resolution revealed for the first time two crystallographically nonequivalent octahedral sites M1 and M2 in the subspectra of olivine and pyroxene that were observed previously in pure natural or synthetic silicates only. Mössbauer hyperfine parameters and relative areas related to M1 and M2 sites in olivine and pyroxene determined from Mössbauer spectra of ordinary chondrites were analyzed and compared with parameters of pure natural and synthetic silicates. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Micro‐Raman investigation of cubic silicon carbide crystals grown from the travelling zone method
Authors: Lewandowska R. , Eid J. , Camassel J. , Santailler J. L. , Ferrand B. 
Published: March 2007

AbstractMicro‐Raman spectroscopy has been used to investigate two different 3C‐SiC crystals grown from the melt using the travelling‐zone method. The melt was a C‐rich silicon solution held at 1700 °C. Two different (relative) positions of the seed and feed (bottom and up, respectively) were investigated. We show that much better results, with smaller internal strain, can be obtained when placing the seed on top of the feed. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
AFM and FTIR characterization of microcrystalline Si obtained from isothermal annealing of Al/a‐Si:H
Authors: Rojas‐López M. , Orduña‐Díaz A. , Delgado‐Macuil R. , Olvera‐Hernández J. , Navarro‐Contreras H. , Vidal M. A. , Saucedo N. , Mendez‐García V. H. 
Published: March 2007

AbstractAtomic force microscopy and Fourier transform infrared spectroscopy were used to investigate the morphology of the microcrystalline surface, and also the amorphous‐crystalline structural transformation of a‐Si:H films, isothermally annealed during several hours. Crystallization process was strongly influenced by the deposition of an Al layer on the surface of a‐Si:H samples. Representative AFM images show the presence of grains, which increase in diameter with the annealing time. Relative crystallized fraction as a function of the annealing time can be described adequately by using the Avrami equation. The kinetic of this crystallization process suggest a two‐dimensional growth of the Si nuclei. Fourier transform infrared measurements show the presence of an intense band near 512 cm–1 associated to Si–Si bonding. We observed the relative diminishing of the intensity of the Si–H wagging mode at 694 cm–1 with annealing time, suggesting effusion of hydrogen to the surface of microcrystalline films. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Optical measurement of carrier concentration profile in n‐type semiconducting GaAs substrate
Authors: Kitamoto Takuya , Inoue Yusuke , Yamada Masayoshi , Kawase Tomohiro 
Published: March 2007

AbstractThe light absorption below the fundamental energy gap in n‐type GaAs has been investigated precisely. It is experimentally confirmed that there are the three different mechanisms: (a) the enhancement of fundamental absoption due to the shrinkage of energy gap and band filling by doping Si atoms, (b) deep‐level (EL2) absorption, and (c) free‐carrier absorption. It is found that the transmittance measurement at the wavelength longer than about 1000 nm in the free‐carrier absorption region is more useful and direct, compared with that near the fundamental absorption region from 900 nm to 950 nm, precisely to determine the carrier concentration in n‐type GaAs. The two‐dimensional profile of carrier concentration in a VB‐grown 3 ϕ GaAs substrate is measured in high spatial resolution with the short time less than 5 seconds by using a sophisticated near‐infrared transmittance‐measuring equipment. The absolute amount and homogeneity of carrier concentration can be assessed in the range from 0.3 to 3 × 1018 cm–3. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
In‐situ X‐ray photoelectron spectroscopy characterization of Si interlayer based surface passivation process for AlGaAs/GaAs quantum wire transistors
Authors: Akazawa Masamichi , Hasegawa Hideki , Jia Rui 
Published: March 2007

AbstractDetailed properties of the Si interface control layer (Si ICL)‐based surface passivation structure are characterized by in‐situ X‐ray photoelectron spectroscopy (XPS) in an ultra‐high vacuum multi‐chamber system. Si ICLs were grown by molecular beam epitaxy (MBE) on GaAs and AlGaAs(001) and (111)B surfaces, and were partially converted to SiNx by nitrogen radical beam. Freshly MBE‐grown clean GaAs and AlGaAs surfaces showed strong Fermi level pinning. Large shifts of the surface Fermi level position corresponding to reduction of pinning took place after Si ICL growth, particularly on (111)B surface (around 500 meV). However, subsequent surface nitridation increased pinning again. Then, a significant reduction of pinning was obtained by changing SiNx to silicon oxynitride by intentional air‐exposure and subsequent annealing. This has led to realization of a stable passivation structure with an ultrathin oxynitride/Si ICL structure which prevented subcutaneous oxidation during further device processing under air‐exposure. The Si‐ICL‐based passivation process was applied to surface passivation of quantum wire (QWR) transistors where anomalously large side‐gating phenomenon was completely eliminated. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Shear viscosity calculations through a reverse nonequilibrium method
Authors: Cavalcanti W. L. , Chen X. , Müller‐Plathe F. 
Published: March 2007

AbstractIn this work we present the result of an algorithm implementation for reverse nonequilibrium molecular dynamics simulation which allows the prediction of viscosity. A non physical momentum flux is imposed by dividing the simulation box into slabs and applying an exchange of the largest negative and positive velocities atoms between the first and central slabs respectively, as result a velocity gradient is produced. This technique has been successfully implemented for atomistic simulations using a molecular dynamics package YASP which works on analytical potential. However, our work focuses on the implementation of RNEMD method into a molecular dynamics code GMQ which works on numerical potential. The developed code provides a reliable tool to predict viscosities for coarse‐grained models via RNEMD technique. The results for Lennard–Jones liquids are presented as well as their comparison for both molecular dynamics codes. Our results are also in good agreement with experimental data. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Some mechanisms for the incorporation of hydrogen in Hf‐based gate dielectric films on Si
Authors: Driemeier C. , Baumvol I. J. R. 
Published: March 2007

AbstractHf‐based materials are the leading candidates to replace SiO2 gate dielectrics in future Si‐based metal–oxide–semiconductor field‐effect transistors and H inside gate dielectrics has recognized roles on device performance and reliability. In this context, by employing nuclear reaction analyses of 1H and 2H nuclides as well as X‐ray photoelectron spectroscopy, H incorporation in HfSiO, HfSiN, and HfO2 films on Si was accessed. Two technologically relevant H sources were investigated, namely annealing in H2 at 400–600 °C and room temperature exposure to water vapour. We found that annealing in H2 leads to high (when compared to SiO2) bulk H incorporation in HfSiO and HfSiN films, probably reflecting higher density of H trapping sites in these Hf‐based materials. On the other hand, H incorporation in HfO2 films occurs mainly at HfO2 surface, without measurable H incorporation in HfO2 bulk. Moreover, by exposing HfO2 films on Si to water vapour we showed the formation of a hydroxylated HfO2 surface as well as migration of water‐derived species through HfO2 films, incorporating water‐derived species at the interfacial region between HfO2 and Si. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Energetics of silicon nanowires: a molecular dynamics investigation
Authors: Menezes R. D. , Justo J. F. , Assali L. V. C. 
Published: March 2007

AbstractSilicon nanowires, with the 〈100〉 and 〈110〉 growth directions and at several surface facet configurations, were investigated by molecular dynamics simulations. We considered three commonly used interatomic potentials for silicon, and tested the reliability of each model to describe silicon nanowires. We find that, for each growth direction, the facet family plays a central role on the nanowire energy, which follows a universal scaling law as a function of the nanowire perimeter. Those results were discussed in the context of recent experimental and ab initio data. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Mean field approximation for the kinetics of the selective catalytic reduction of NO by ammonia
Authors: Santos M. , Bodanese J. P. , da S. Grandi B. C. 
Published: March 2007

AbstractIn this work we study a catalytic reaction model among three monomers in order to understand the chemical kinetics of the selective catalytic reduction of nitrogen oxide by ammonia (4NO + 4NH3 + O2 → 4N2 + 6H2O). Our model takes into account the formation of the intermediate species in the global scheme of the reaction. In order to determine the dynamical behaviour of the model we used single site approximation method. In this approach we have observed that, depending on the values of the control parameters, the model presents an active or an inactive phase. In fact, the dynamical phase diagram of the model exhibits a first order line separating these two phases. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)