bluuebunny/crossref_metadata_2025_split huggingface dataset:
Determining the density profile of confined polymer brushes with neutron reflectivity
Authors: Hamilton W. A. , Smith G. S. , Alcantar N. A. , Majewski J. , Toomey R. G. , Kuhl T. L. 
Published: July 2004

AbstractPolymer molecules at solid or fluid interfaces have an enormous spectrum of applications in a wide variety of technologies as lubricants, adhesion modifiers, and protective surface coatings. Because polymer brushes have great potential to be used in such applications, there is a need to determine their structure and efficiency in reduced spaces. Using neutron reflectivity, we have directly quantified the density distribution of opposing polymer brushes under confinement in good solvent conditions under confinement. Our measurements show that the density profile in the overlap region between opposing polymer brushes flattens, consistent with predictions from molecular‐dynamics simulations. In addition, a significant increase in the density at the anchoring surfaces due to the collapse of the brush layers was observed. This collapse of the brushes in restricted geometries suggests that high‐density brushes do not interpenetrate significantly under good solvent conditions. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3290–3301, 2004
Using neutron reflectivity to determine the dynamic properties of a copolymer in a homopolymer matrix
Authors: Arlen Michael J. , Dadmun M. D. , Hamilton William A. 
Published: July 2004

AbstractA protocol for using neutron reflectivity to monitor the dynamic properties of a copolymer in a homopolymer matrix is described. This technique may be used to monitor a broad range of systems, as long as the copolymer and homopolymer form a miscible blend at low copolymer concentrations. Moreover, with knowledge of the Flory–Huggins interaction parameter between the copolymer and homopolymer, the molecular dynamic parameters of the copolymer, such as the tracer diffusion coefficient, segmental friction factor, and longest relaxation time, can be quantitatively determined. This technique is demonstrated by the determination of these parameters for a series of styrene/methyl methacrylate alternating copolymers dispersed in a matrix of deuterated poly(methyl methacrylate). Interestingly, the segmental friction factor of these alternating copolymers is significantly different from that of similar diblock copolymers. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3235–3247, 2004
Neutron reflectivity study of glassy polymer brushes in density fluctuating supercritical carbon dioxide
Authors: Koga Tadanori , Ji Y. , Seo Y. S. , Gordon C. , Qu F. , Rafailovich M. H. , Sokolov J. C. , Satija S. K. 
Published: July 2004

AbstractBy using in situ neutron reflectivity, we measured the swelling behavior of two types of polymer brushes, deuterated polystyrene with a trichlorosilane end group and deuterated polystyrene‐block‐poly(4‐vinylpyridine) block copolymer, in supercritical carbon dioxide (scCO2). The measurements were conducted in the pressure range of 0.1–20 MPa at 36 °C. The pressure dependence of the brush height clearly showed an anomalous peak at the density fluctuation ridge (pressure = 8.2 MPa) that defined the maximum long‐range density fluctuation amplitude in the pressure–temperature phase diagram of carbon dioxide (CO2). The density profile of the brush, which could be approximated by a simple step function, and the magnitude of the brush height both indicated that the solvent quality of scCO2 for the deuterated polystyrene brushes was still poor even at the density fluctuation ridge. In addition, atomic force microscopy images for the frozen polystyrene brush prepared by the rapid drying of CO2 showed a phase‐separated structure, as predicted from the numerical calculations of Grest and Murat, as a function of the variable Nσ, where N is the polymerization index and σ is the grafting density. © 2004 Wiley Periodicals, Inc. J Polym Sci Part B: Polym Phys 42: 3282–3289, 2004
An atomic resolution structure for human fibroblast growth factor 1
Authors: Bernett Matthew J. , Somasundaram Thayumanasamy , Blaber Michael 
Published: July 2004

AbstractA 1.10‐Å atomic resolution X‐ray structure of human fibroblast growth factor 1 (FGF‐1), a member of the β‐trefoil superfold, has been determined. The β‐trefoil is one of 10 fundamental protein superfolds and is the only superfold to exhibit 3‐fold structural symmetry (comprising 3 “trefoil” units). The quality of the diffraction data permits unambiguous assignment of Asn, Gln, and His rotamers, Pro ring pucker, as well as refinement of atomic anisotropic displacement parameters (ADPs). The FGF‐1 structure exhibits numerous core‐packing defects, detectable using a 1.0‐Å probe radius. In addition to contributing to the relatively low thermal stability of FGF‐1, these defects may also permit domain motions within the structure. The availability of refined ADPs allows a translation/libration/screw (TLS) analysis of putative rigid body domains. The TLS analysis shows that β‐strands 6–12 together form a rigid body, and there is a clear demarcation in TLS motions between the adjacent carboxyl‐ and amino‐termini. Although separate from β‐strands 6–12, the individual β‐strands 1–5 do not exhibit correlated motions; thus, this region appears to be comparatively flexible. The heparin‐binding contacts of FGF‐1 are located within β‐strands 6–12; conversely, a significant portion of the receptor‐binding contacts are located within β‐strands 1–5. Thus, the observed rigid body motion in FGF‐1 appears related to the ligand‐binding functionalities. Proteins 2004. © 2004 Wiley‐Liss, Inc.
The B‐ring substituent at C‐7 of colchicine and the α‐C‐terminus of tubulin communicate through the “tail–body” interaction
Authors: Chakraborty Shalmali , Gupta Suvroma , Sarkar Taradas , Poddar Asim , Pena Jose , Solana Rafael , Tarazona Raquel , Bhattacharyya Bhabatarak 
Published: July 2004

AbstractThe carboxy terminals of αβ‐tubulins are flexible regions rich in acidic amino acid residues that play an inhibitory role in the polymerization of tubulin to microtubules. We have shown that the binding of colchicine and its B‐ring analogs (with C‐7 substituents) to tubulin are pH sensitive and have high activation energies. Under identical conditions, the binding of analogs without C‐7 substituents is pH independent and has lower activation energy. β‐C‐terminus‐truncated tubulin (αβs) shows similar pH sensitivity and activation energy to native tubulin (αβ). Removal of the C‐termini of both subunits of tubulin (αsβs) or the binding of a basic peptide P2 to the negatively charged α‐C‐terminus of tubulin causes a colchicine–tubulin interaction independent of pH with a low activation energy. Tubulin dimer structure shows that the C‐terminal α‐tail is too far from the colchicine binding site to interact directly with the bound colchicine. Therefore, it is likely that the interaction of the α‐C‐terminus with the main body of tubulin indirectly affects the colchicine–tubulin interaction via conformational changes in the main body. We therefore conclude that in the presence of tail–body interaction, a B‐ring substituent makes contact with the α‐tubulin and induces significant conformational changes in α‐tubulin. Proteins 2004. © 2004 Wiley‐Liss, Inc.
Crystallographic studies of V44 mutants of Clostridium pasteurianum rubredoxin: Effects of side‐chain size on reduction potential
Authors: Park Il Yeong , Eidsness Marly K. , Lin I‐Jin , Gebel Erika B. , Youn Buhyun , Harley Jill L. , Machonkin Timothy E. , Frederick Ronnie O. , Markley John L. , Smith Eugene T. , Ichiye Toshiko , Kang ChulHee 
Published: July 2004

AbstractUnderstanding the structural origins of differences in reduction potentials is crucial to understanding how various electron transfer proteins modulate their reduction potentials and how they evolve for diverse functional roles. Here, the high‐resolution structures of several Clostridium pasteurianum rubredoxin (Cp Rd) variants with changes in the vicinity of the redox site are reported in order to increase this understanding. Our crystal structures of [V44L] (at 1.8 Å resolution), [V44A] (1.6 Å), [V44G] (2.0 Å) and [V44A, G45P] (1.5 Å) Rd (all in their oxidized states) show that there is a gradual decrease in the distance between Fe and the amide nitrogen of residue 44 upon reduction in the size of the side chain of residue 44; the decrease occurs from leucine to valine, alanine or glycine and is accompanied by a gradual increase in their reduction potentials. Mutation of Cp Rd at position 44 also changes the hydrogen‐bond distance between the amide nitrogen of residue 44 and the sulfur of cysteine 42 in a size‐dependent manner. Our results suggest that residue 44 is an important determinant of Rd reduction potential in a manner dictated by side‐chain size. Along with the electric dipole moment of the 43‐44 peptide bond and the 44–42 NHS type hydrogen bond, a modulation mechanism for solvent accessibility through residue 41 might regulate the redox reaction of the Rds. Proteins 2004. © 2004 Wiley‐Liss, Inc.
The electronic structure and magnetic property of metal‐oxo, porphyrin manganese‐oxo, and μ‐oxo‐bridged manganese porphyrin dimer
Authors: Koizumi K. , Shoji M. , Nishiyama Y. , Maruno Y. , Kitagawa Y. , Soda K. , Yamanaka S. , Okumura M. , Yamaguchi K. 
Published: July 2004

AbstractHybrid density functional theory (HDFT) and post Hartree–Fock CCSD(T) methods are applied to elucidate the binding energies and the optimized MO distances of transition metal oxides: MO (M = Cr, Mn, Fe, Co, Ni, Cu). The HDFT method can reproduce the CCSD(T) results, in agreement with the experimental ones. The nature of the manganese–oxygen bonds in the Mn(VI)O, Mn(IV)O porphyrin (PP), and Mn(V)O PP systems are examined in relation to possible mechanisms of oxygen evolution from H2O2 and H2O in native and non‐native manganese complexes. It is found that the radical character of the high‐valent (PP)Mn(V)O bond is remarkable, showing the strong potential to generate molecular oxygen because of its high reactivity. The electronic structure and magnetic property of μ‐oxo‐bridged manganese porphyrin dimer (PPMn(III)OMn(III)PP) are investigated for further discussion of structure and reactivity of PPMn(X)O (X = II–IV). The potential curve for release of molecular oxygen from PPMn(II)O2 is also examined to show weak affinity of O2 in the Mn complex where the oxidation number (X) of Mn is low. Implications of the computational results are also discussed in relation to oxygen evolution reactions. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Conformational studies of benzyl alcohol and benzyl fluoride
Authors: Utzat Karissa , Restrepo Albeiro A. , Bohn Robert K. , Michels H. Harvey 
Published: July 2004

AbstractThe conformations of several benzyl compounds, C6H5CH2X, have been characterized by rotational spectra and theoretical structure calculations. We have observed the microwave spectrum of benzyl alcohol and its OD isotopomer at high resolution in a pulsed‐jet Fourier transform microwave spectrometer. The spectrum is consistent with an asymmetric stable conformation characterized by a CCCO dihedral angle of approximately 60°. The spectrum is strongly perturbed by tunneling interactions. The transitions are split into doublets consistent with tunneling interactions between two equivalent conformational minima. The observed splittings diminish upon deuterium substitution. These observations are similar to those previously reported by us for benzyl fluoride. However, the minimum energy conformation for benzyl fluoride has the CCF plane orthogonal to the plane of the phenyl ring. This conformation for benzyl fluoride is consistent with a model that minimizes steric repulsion between the fluorine of the CH2F group and the closest hydrogens located on the phenyl ring. For benzyl alcohol, previous studies have suggested a weak attraction between the π electrons of the phenyl ring and the substituent OH group as the explanation for the observed stable conformation. A theoretical analysis of the atomic charges in benzyl alcohol suggests another possible explanation of the observed structure. Atomic charges generated by fits to the electrostatic potential indicate a relatively strong dipole–dipole coupling between the CH group in the methylene side chain and the closest CH group in the phenyl ring. This results in a nearly planar orientation of the CH group in the methylene side chain with the phenyl ring, a conformation that yields the observed CCCO dihedral angle. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Fulleride superconductivity compared and contrasted with RVB theory of high Tc cuprates
Authors: Squire Richard H. , March Norman H. 
Published: July 2004

AbstractRecently we proposed a microscopic mechanism for alkali‐metal doped Fulleride superconductivity. The aim of the current study is to compare and contrast such Fulleride superconductivity with that of high Tc cuprates. We focused earlier on “topological” superconductivity in the Fulleride case and so it seemed natural to make contact with the resonating valence bond treatment of Anderson et al. for the high Tc cuprates. Finally, some experimental points of contact involve the product of electrical resistivity and nuclear spin lattice relaxation times in the normal state of both classes of superconductors considered here. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Planck–Benzinger thermal work function in biological systems
Authors: Chun Paul W. 
Published: July 2004

AbstractThe Planck–Benzinger methodology provides a means of determining the innate temperature‐invariant enthalpy and thermal agitation energy, or the heat capacity integrals, ∫ ΔCp°(T)dT, and allows precise determination of 〈TCp〉, 〈Th〉, 〈Ts〉, and 〈Tm〉. It is a method for evaluating [ΔH − ΔH°(T0)], the heat of reaction for biological molecules at room temperature. The results imply that the negative Gibbs free energy change minimum at a well‐defined stable temperature, 〈Ts〉, where the bound unavailable energy TΔS° = 0, has its origin in the sequence‐specific hydrophobic interactions. Each case confirms the existence of a thermodynamic molecular switch wherein a change of sign in ΔCp°(T)reaction leads to true negative minimum in the Gibbs free energy change of reaction and, hence, a maximum in the related equilibrium constant, Keq. At this temperature, 〈TS〉, ΔH°(TS)(−) = ΔG°(TS)(−)min, the maximum work can be accomplished in biological systems. Application of the Planck–Benzinger methodology to biological systems has demonstrated a basic rule for life processes, in that there is a lower cutoff point, 〈Th〉, where entropy is favorable but enthalpy is unfavorable, that is, ΔH°(Th)(+) = TΔS°(Th)(+), and an upper cutoff, 〈Tm〉, above which enthalpy is favorable but entropy unfavorable, that is, ΔH°(Tm)(−) = TΔS°(Tm)(−). Only between these two limits, that is, where ΔG°(T) = 0, is the net chemical driving force favorable for such biological processes as protein folding; protein–protein, protein–nucleic acid or protein‐membrane interactions; and protein–self‐assembly. Indeed, all interacting biological systems examined using the Planck–Benzinger methodology have shown such a thermodynamic switch at the molecular level, suggesting that its existence may be universal. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2004
Fast determination of the total free resveratrol content in wine by direct‐exposure‐probe, positive‐ion chemical ionization and collision‐induced‐dissociation mass spectrometry
Authors: Flamini Riccardo , Vedova Antonio Dalla 
Published: July 2004

AbstractIn the present work, a fast method has been developed for the determination of total free resveratrol in wine extracts by positive‐ion chemical ionization using methane as reagent gas and direct introduction of the sample into the mass spectrometer. Quantitative analysis is performed using 4′,5,7‐trihydroxyflavone as internal standard, by recording the product ions atm/z135 for resveratrol andm/z153 for the internal standard, both generated by collision‐induced dissociation experiments on the related [M+H]+ions. The method showed sufficient repeatability and satisfactory linearity in the range of concentration studied. Alternatively, because of the marked effect of matrices on the compounds released in the vaporization step, quantitative analysis was performed by addition of standard resveratrol to the sample, and the total free resveratrol content extrapolated from the calibration curve. Calibration curves for three different wine extracts had correlation coefficients between 0.91 and 0.99, and total free resveratrol contents between 11.8 and 17.2 mg/L were found. This method enabled us to determine the resveratrol‐potential of wine within a few minutes, thereby overcoming the time‐ and solvent‐consuming procedures needed for chromatographic methods. Copyright © 2004 John Wiley & Sons, Ltd.
Determination of linkage position and anomeric configuration in Hex‐Fuc disaccharides using electrospray ionization tandem mass spectrometry
Authors: Xue Jun , Song Liguo , Khaja Sirajud D. , Locke Robert D. , West Christopher M. , Laine Roger A. , Matta Khushi L. 
Published: July 2004

AbstractFixed‐energy sequential tandem mass spectrometry (MSn) capabilities offered by quadrupole ion trap instruments have been explored in a systematic study of six isomers of Gal‐Fucα‐OBenzyl disaccharides. Under collision‐induced dissociation (CID), sodiated molecular species generated in the positive‐ion electrospray ionization mode yield simple and predictable mass spectra. Information on interglycosidic linkages and configurations can be deduced from the relative intensities of the selected diagnostic fragments arising from the glycosidic bond cleavages and corroborated by the fragments arising from cross‐ring cleavages. As the CID patterns are not dependent on the number of prior tandem mass spectrometric steps, structures can be unambiguously assigned by matching the spectra with a library. The rules governing the fragmentation behavior of this class of oligosaccharides were tested for a representative isomeric disaccharide, Glcβ1,3Fucα‐OAllyl. The findings establish a basis for using MSn with a quadrupole ion trap instrument to elucidate structures of hexose‐fucose subunits from more complicated oligosaccharides. Energy‐resolved mass spectra were also acquired by CID tandem triple‐quadrupole mass spectrometry. The breakdown behavior of the molecular ions revealed patterns which could differentiate stereoisomers of Gal‐Fuc disaccharides over a range of collision energy from 20 to 50 eV. Copyright © 2004 John Wiley & Sons, Ltd.
Hamburger Sichel – Das neue Dach des Zentralen Omnibusbahnhofs
Authors: Keil Andreas , Werwigk Michael , Kempkes Marian 
Published: July 2004

AbstractWeithin sichtbares Markenzeichen des neuen Zentralen Omnibus Bahnhofs (ZOB) Hamburg ist das signifikante Dach, das sich mit über 4000 m2 und einer Länge von knapp 200 m über die gesamte Anlage spannt. Die Anordnung der Bustaschen führte zu der sichelförmigen Geometrie des Daches, das wie ein überdimensionaler Bumerang über dem Busbahnhof mit seinen Betriebsgebäuden schwebt.Das Dach steht einseitig auf einer Kolonnade schlanker Stützen, die dem Bogen der in 12 m Höhe liegenden, gekrümmten Stahl‐Stabrippenschale folgt. Daran angeschlossen sind Kragträger unterschiedlicher Länge, unter denen die großflächige Glaseindeckung punktförmig an Pfetten abgehängt ist.Dieser Beitrag beschreibt den Entwurf, die Konstruktion und ausgewählte Besonderheiten bei Herstellung und Montage.
Der neue Flughafen in Bankok – eine ingenieurtechnische Herausforderung
Authors: Sobek Werner , Linder Josef , Krampen Jürgen 
Published: July 2004

AbstractDer neue Flughafen in Bangkok ist z. Z. eine der größten Baustellen der Welt. Planung und Ausführung dieses Projektes erforderten von Planern und beteiligten Firmen extreme Sorgfalt und eine äußerst intensive Zusammenarbeit in allen Phasen des Projekts. Im nachfolgenden Artikel soll zunächst ein Überblick über die Gesamtmaßnahme gegeben werden, bevor dann am Beispiel der über 3100 m langen ‘Concoursen’ die vorbildliche Zusammenarbeit von Planern und ausführenden Firmen erläutert wird.
Berechnung von Stahlverbundträgern – Ein Rechenmodell zur Berücksichtigung von verformbaren, teiltragfähigen Verbundanschlüssen
Authors: Jost Markus , Odenbreit Christoph 
Published: July 2004

AbstractTypische Verbundanschlüsse, wie z. B. in Bild 1 dargestellt, haben oft nicht die volle Tragfähigkeit des angeschlossenen Verbundträgers und sind auch zu biegeweich, um das volle Stützmoment, das sich aus der elastischen Berechnung unter der Annahme einer vollen Einspannung ergibt, aufbauen zu können. Andererseits sind aber die Steifigkeiten und die Tragfähigkeiten in den Anschlüssen zu groß, um sie einfach zu vernachlässigen. Im folgenden Artikel wird eine Methode vorgestellt, um die rechnerischen Kennwerte von Verbundanschlüssen zu ermitteln, das Verhalten des Anschlusses als bilineare Feder abzubilden und die Gesamtberechnung des Verbundträgers durchzuführen.
Trag‐ und Ermüdungsverhalten liegender Kopfbolzendübel unter Quer‐ und Längsschub
Authors: Kürschner Kai , Kuhlmann Ulrike 
Published: July 2004

AbstractNeue interessante Verbundquerschnitte aus Stahlbeton und Baustahl im Hoch‐ und Brückenbau führen unter Berücksichtigung konstruktiver, fertigungstechnischer und wirtschaftlicher Gesichtspunkte zu einer liegenden, d.h. randnahen Anordnung von Kopfbolzendübeln. Infolge des geringen Abstands der Dübelreihe zum freien Plattenrand ergeben sich gegenüber stehenden bzw. randfernen Kopfbolzen unterschiedliche Bettungseigenschaften der Dübel im umgebenden Stahlbeton und somit auch ein abweichendes Trag‐ und Ermüdungsverhalten der Verbundfuge. Im Hinblick auf zukünftige Anwendungen von liegenden Kopfbolzendübeln werden auf Grundlage experimenteller und theoretischer Untersuchungen einfache Bemessungs‐ und Konstruktionsregeln für den Nachweis der Verbundfuge unter ruhendem Querschub, ruhendem Quer‐ und Längsschub und nicht ruhendem Längsschub vorgestellt.
Zur Toleranzklassifizierung im Stahlbau
Authors: Urbańska‐Galewska Elżbieta 
Published: July 2004

AbstractIn den letzten Jahrzehnten gab es wesentliche Veränderungen beim Bau von Stahlkonstruktionen. Die Genauigkeit bei der Herstellung und Montage wurde von mehreren europäischen und nationalen Normen bestimmt. Diese stimmen jedoch oft nicht überein und führen nicht immer zur richtigen Montage. Im Beitrag werden die Fragen der Imperfektion und der Toleranz in den aktuellen Normen besprochen und die Idee der Einführung von Genauigkeitsklassen für die Ausführung von Stahlkonstruktionen, in Abhängigkeit von mehreren projekttechnischen und wirtschaftlichen Faktoren, dargestellt. Zu diesem Zweck wird eine neue Klassifizierung der zulässigen Fertigungsabweichungen vorgeschlagen. Sie ist abhängig vom Ort des Auftretens und der Wertigkeit innerhalb der Montage. Dargestellt wird die Bestimmungsart der Fertigungsgenauigkeit von Koordinationsmontagemaßen mit Hilfe der Toleranzanalyse und ‐synthese, wobei die Methoden der Toleranzanalyse beschrieben werden. Die vorgeschlagene Methode der Toleranzklassifizierung ist ein modernes Werkzeug für die notwendige Qualitätssicherung von Stahlkonstruktionen ohne Zusatzkosten. Ein Zahlenbeispiel verdeutlicht die Methoden der Toleranzanalyse und ‐synthese.