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  • Artikel  (1.304)
  • Analytical Chemistry and Spectroscopy  (707)
  • Physics  (597)
  • 1995-1999  (250)
  • 1980-1984  (848)
  • 1965-1969  (206)
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  • 1
    ISSN: 1075-4261
    Schlagwort(e): cholelithiasis ; gallstone ; bile salts ; periodic precipitation ; fractal precipitation ; Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: This is the first observation that both chaotic and periodic patterns are formed in metal ions-deoxycholate-gel systems. It is an in vitro model for approximating the conditions present during gallstone formation. The experimental results suggest that a nonlinear scientific concept such as the “butterfly effect” should be considered in understanding gallstone formation. This effect suggests that a butterfly flapping its wings in Beijing today may lead to a thunderstorm in New York months later. Applying this concept to biology, minor changes in the local chemical environment within biological systems may lead to large variations in the structure and morphology of gallstone through changes in the behavior of biological mineralization process. © 1997 John Wiley & Sons, Inc. Biospect 3: 195-205, 1997
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science Part A-2: Polymer Physics 6 (1968), S. 1183-1202 
    ISSN: 0449-2978
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: Crosslinked samples of polyethylene were prepared by electron irradiation of both high- and low-density polymers in the crystalline state. A further crosslinked sample was obtained by curing a high-density polyethylene by reaction with dicumyl peroxide at 180°C. The stress-strain-birefringenece relations were obtained on specimens cut from these samples at temperatures between 130 and 250°C. All samples showed a substantial decrease in stress-optical coefficient with increasing degree of crosslinking and with increasing temperature. The stress-optical properties at each temperature were extrapolated to zero degree of crosslinking to give quantities characteristic of the Gaussian network. Comparison of these properties with the theory of networks of rotational isomeric chains with both independent and interdependent rotation allows estimates to be obtained for (1) the trans-gauche energy differences in rotation around skeletal bonds and (2) the difference in principal optical polarizabilities for the CH2 group in the elastomeric state. This latter quantity is shown to be more nearly given by Denbigh's than by Bunn and Daubeny's bond polarizability values.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 3
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 2925-2933 
    ISSN: 0887-6266
    Schlagwort(e): ionic conductivity ; DC conductivity ; rigid-rod polymer ; depletion measurement ; X-ray scattering ; anisotropic ; polymer electrolyte ; polyelectrolyte ; conducting polymers ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The conductivity study results of lithium-doped sulfonated PBI, a conjugated rigid rod polymer, poly[(1,7-dihydrobenzo[1,2-d:4,5-d′]dimidazole-2,6-diyl)-2-(2-sulfo)-p-phenylene], derivatized with pendants of propane sulfonate Li+ ionomer are reported. The room-temperature DC four-probe conductivity parallel to the surface of cast films was as large as 8.3 × 10-3 S/cm. Similar measurements with an eight-probe configuration showed no difference between bulk and surface conductivity. The ionic nature of the conductivity was indicated by constant voltage depletion experiments and by secondary ion mass spectroscopy measurements of the residues near the electrodes. The DC two-probe conductivity measured transverse to the sample surface was three to four orders of magnitude smaller than longitudinal conductivity, while the AC two-probe conductivity was even less. Electron microscopy indicated that the films had a layered structure parallel to the surfaces. This structural anisotropy was confirmed by refractive index values obtained from wave-guide experiments and by wide angle X-ray scattering. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 2925-2933, 1997
    Zusätzliches Material: 11 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 4
    Digitale Medien
    Digitale Medien
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 65-73 
    ISSN: 0887-6266
    Schlagwort(e): poly(ether ether ketone) (PEEK) ; poly(ether ketone ketone) (PEKK) ; solvent-induced crystallization ; Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie , Physik
    Notizen: The relationship between semicrystalline morphology and glass transition temperature has been investigated for solvent-crystallized poly(ether ether ketone) (PEEK) and poly(ether ketone ketone) (PEKK). Solvent-crystallized specimens of both PEEK and PEKK displayed a sizeable positive offset in Tg compared to quenched amorphous specimens as well as thermally crystallized specimens of comparable bulk crystallinity; the offset in Tg for the crystallized samples reflected the degree of constraint imposed on the amorphous segments by the crystallites. Small-angle X-ray scattering studies revealed markedly smaller crystal long periods (d) for the solvent-crystallized specimens compared to samples prepared by direct cold crystallization. The strong inverse correlation observed between Tg and interlamellar amorphous thickness (lA) based on a simple two-phase model was in excellent agreement with data reported previously for PEEK, and indicated the existence of a unique relationship between glass transition temperature and morphology in these poly(aryl ether ketones) over a wider range of sample preparation history and lamellar structure than was previously reported. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 65-73, 1998
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 5
    Digitale Medien
    Digitale Medien
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 712-716 
    ISSN: 0951-4198
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Physik
    Notizen: A variety of ionophores have been studied by packed column supercritical-fluid chromatography combined with mass spectrometry. One of the ionophores, lasalocid, provided particularly good multiple-reaction monitoring signal-to-noise responses when analysed by tandem mass spectrometry and this approach shows considerable potential for the analysis of this compound in medicated animal feeds. A capillary supercritical-fluid chromatograph has been interfaced to an unmodified benchtop quadrupole mass spectrometer and this combination has enabled the molecular weight determination of the sodium salt of an ionophore.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 6
    ISSN: 1052-9306
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: As part of a study to make a comparative analysis of selected halogenated compounds in man and the environmental media, a quantitative gas chromatographic mass spectrometric analysis of the levels of the halogenated compounds found in the breath, blood and urine of an exposed population (Old Love Canal area, Niagara, New York) and their immediate environment (air and water) was undertaken. In addition, levels of halogenated hydrocarbons in air samples taken in the general Buffalo, Niagara Falls area were determined.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 7
    Digitale Medien
    Digitale Medien
    New York, NY [u.a.] : Wiley-Blackwell
    Biospectroscopy 1 (1995), S. 291-296 
    ISSN: 1075-4261
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Deoxycholic acid is an important physiological bile acid. The binding of bile salts with metal ions has received more attention due to its clinical significance. In this study, a series of copper and zinc deoxycholate complexes were synthesized. EXAFS and FTIR spectroscopic techniques were used for characterization. The results indicated that both the carboxyl and hydroxyl groups of deoxycholic acid are binding to the Cu (or Zn) ion to form a new complex. There are six oxygen atoms surrounding the metal ion with the average bond lengths of Cu-O and Zn-O are 1.95 and 2.06 Å respectively. © 1995 John Wiley & Sons, Inc.
    Zusätzliches Material: 6 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 8
    ISSN: 1075-4261
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Biologie , Physik
    Notizen: Rapid advances in the generation of intense tunable ultrashort mid-infrared (IR) laser pulses allow the use of ultrafast IR pump-probe and vibrational echo experiments to investigate the dynamics of the fundamental vibrational transition of CO bound to the active site of heme proteins. The studies were performed using a free-electron laser (FEL) and an experimental set up at the Stanford University FEL Center. These novel techniques are discussed in some detail. Pump-probe experiments on myoglobin-CO (MbCO) measure CO vibrational relaxation (VR). The VR process involves loss of vibrational excitation from CO to the protein and solvent. Infrared vibrational echoes measure CO vibrational dephasing. The quantum mechanical treatment of the force-correlation function description of vibrational dynamics in condensed phases is described briefly. A quantum mechanical treatment is needed to explain the temperature dependence of VR in Mb-CO from 10 to 300 K. A molecular-level description including elements of heme protein structure in the treatment of vibrational dynamics is also discussed. Vibrational relaxation of CO in Mb occurs on the 10-11-s time scale. VR was studied in proteins with single-site mutations, proteins from different species, and model heme compounds. A roughly linear relationship between carbonyl stretching frequency and VR rate has been observed. The dominant VR pathway is shown to involve anharmonic coupling from CO through the π-bonded network of the porphyrin, to porphyrin vibrations with frequencies 〉 400 cm-1. The heme protein influences VR of bound ligands at the active site primarily via altering the through π-bond coupling between CO and heme. Preliminary vibrational echo studies of the effects of protein conformational relaxation dynamics on ligand dephasing are also reported. © 1996 John Wiley & Sons, Inc.
    Zusätzliches Material: 12 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 9
    Digitale Medien
    Digitale Medien
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 19 (1981), S. 2817-2834 
    ISSN: 0360-6376
    Schlagwort(e): Physics ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Thermal degradation behavior of poly(1,3-phenylene isophthalamide) and poly(chloro-2,4-phenylene isophthalamide) was investigated with the aid of some appropriate model compounds. The pyrolysis products of these materials were identified by gas chromatography (GC), gas chromatography/Fourier transform infrared spectroscopy (GC/FT-IR), and gas chromatography/mass spectrometry (GC/MS). The residual chars were characterized by IR spectroscopy. Thermogravimetric analysis (TGA) was applied to study the effect of end-group concentration on the degradation characteristics of the two polyamides. Kinetic parameters that describe the thermal degradation of the polyamides were also evaluated by TGA. The results of this investigation suggest that the thermal decomposition of these aromatic polyamides involves homolytic as well as hydrolytic cleavages of the amide units.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 10
    ISSN: 0030-4921
    Schlagwort(e): Chemistry ; Analytical Chemistry and Spectroscopy
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The effects of protonation and hydrogen bonding in linear Schiff bases obtained from n-butylamine with butyraldehyde, crotonaldehyde, sorbaldehyde and all-trans-retinal were studied by means of 15N and 13C NMR. The protonation-induced chemical shifts (Δδ) are an order of magnitude larger for 15N than for 13C. For 15N, this effect was found to increase with the extent of conjugation, culminating in the retinylideneimine (Δδ = -146 ppm), which constitutes a model for the study of the structure of the Schiff base linkage in visual pigments and related systems. Theoretical calculations of protonation-induced Δδ values based on MINDO/ 3 are in agreement with experimental results.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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