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  • Polymer and Materials Science  (68)
  • Gas chromatography
  • 1990-1994  (71)
  • 1
    Digitale Medien
    Digitale Medien
    Indirect GC determination of ethephon in drinking water by a combination of reactive headspace sampling with adsorptive enrichment/thermal desorption (1993)
    Springer
    Chromatographia 37 (1993), S. 361-364 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Headspace sampling ; PTV-System ; Ethephon in drinking water
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary An indirect GC method is described for the determination of Ethephon in drinking water on the basis of the headspace analysis of the ethylene formed from Ethephon. In order to reach the necessary detection limit, the entire volume of the static headspace distribution is transferred into a cold injection system (CIS). There, the ethylene is adsorbed on Carbosieve SIII at 10°C and, subsequently, desorbed at 300 °C. The water vapour included in the headspace is completely eliminated through the splitting system. By means of this technique, a detection limit of 0.05 μg/l water was reached.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02272249
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  • 2
    Digitale Medien
    Digitale Medien
    Size and shape parameter of the actin-binding protein profilin in solution: A depolarized and polarized dynamic light scattering study (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 219-222 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360300123
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  • 3
    Digitale Medien
    Digitale Medien
    Restrained energy refinement with two different algorithms and force fields of the structure of the α-amylase inhibitor tendamistat determined by nmr in solution (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 695-706 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The solution structure of an α-amylase inhibitor, tendamistat, calculated from nmr data with the distance geometry program DISMAN is subjected to restrained energy minimization. To study the influence of force field parametrizations and the convergence behavior of refinement algorithms, two different programs were used. AMBER is an established software package including a steepest descent and/or conjugent gradient optimizer in the Euclidian space; the name AMBER also represents a force field. The program FANTOM (fast Newton-Raphson torsion angle energy minimizer) is a new restrained energy refinement implementation of the Newton-Raphson algorithm, which uses second derivatives of the conformational energy in dihedral angle space with the ECEPP/2 force field. For both programs the normal energy force field was supplemented with an additional potential of the form ΣA(di - ui)6 (if di 〉 ui), which enforces upper limits ui to selected distances di as measured by nmr. Improvements of the intramolecular interactions with a decrease of the internal energies of about 1000 kcal/mol could be achieved without increasing the distance constraint violations. The restrained energy refinements caused only small changes of the molecular geometries: The root mean square distance values for the backbone atoms between the initial DISMAN structure and the refined structures are about 0.5 Å for AMBER and about 0.7 Å for FANTOM. Local conformational changes during the restrained energy minimizations are analyzed with respect to hydrogen-bond formation, and with respect to comparisons of the solution structure and the crystal structure.
    Zusätzliches Material: 4 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360290404
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  • 4
    Digitale Medien
    Digitale Medien
    Internal dynamics of tRNAPhe studied by depolarized dynamic light scattering (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 975-983 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: The collective internal dynamics of transfer RNAphe from brewer's yeast in solution was studied by depolarized dynamic light scattering (DDLS). Within the melting region of tRNA the depolarized spectra consist of two Lorentzian, where the narrow (slow) component describes the overall rotation of the macromolecule. The broad component is attributed to the collective reorientation of the bases within the biopolymer. At high temperature only this relaxation process is observed in the spectrum. The viscosity dependence of the collective internal relaxation process is described by the Stokes-Einstein-Debye equation for rotational diffusion. Estimates of the internal orientational pair correlation factor from the integral depolarized intensities of tRNAPhe solutions indicates that the observed dynamics correspond to the collective reorientation of approximately 5 bases. A comparison of the results presented with DDLS studies on the aggregation of the mononucleotide guanosine-5′-monophosphate confirms this result. For a further characterization of the relaxation process we studied the effect of hydrostatic pressure (1-1000 bar) on the depolarized spectra of tRNA. While other spectroscopic methods like nmr, fluorescence polarization anisotropy decay, or ESR give information about the very local motion of a single base within the DNA or RNA, this study shows that by DDLS one can characterize collective internal motions of macromolecules.
    Zusätzliches Material: 3 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360300912
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  • 5
    Digitale Medien
    Digitale Medien
    Internal dynamics of linear and superhelical DNA as studied by photon correlation spectroscopy (1991)
    New York : Wiley-Blackwell
    Biopolymers 31 (1991), S. 813-825 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Photon correlation spectroscopy has been used to study the translational (D0)and internal dynamics of monodisperse linear and polydisperse superhelical plasmid-DNAs. Scattering vector dependent correlation functions were measured and analyzed with the inverse Laplace transform CONTIN written by S. Provencher. For scattering vectors (q) lower than 1.3 × 105cm-1, D0 can be separated from internal dynamics. Using the measured D0value, the q dependence of internal modes was determined. Extrapolation of the internal relaxation times for q → 0 yields the longest internal relaxation time t1. This time can be connected to the persistence length in terms of the Berg-Soda model, which describes the molecule as a semiflexible circular polymer with hydrodynamic interactions. The calculated length of 76 nm for DNA, I = 0.15 mol/L, is a little higher than the one obtained from static light scattering data without excluded volume corrections. A comparison of experimental and simulated correlation functions for the Berg-Soda model shows that the model gives a fairly good description of the dynamics of the linear molecule, whereas large discrepancies between model and experimental functions are observed for the superhelical DNA. Small differences between model and experimental functions are mainly attributed to the neglect of the torsional modes that may be coupled to bending and flexing modes. For the superhelical DNA the agreement is improved if the calculation is carried out with a linear molecule, with shorter contour length and increased diameter. Both quantities can be derived from the known superhelix tilt angle.
    Zusätzliches Material: 8 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360310702
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  • 6
    Digitale Medien
    Digitale Medien
    Dynamics of F-actin and F-actin/filamin networks as studied by photon correlation spectroscopy (1990)
    New York : Wiley-Blackwell
    Biopolymers 30 (1990), S. 677-689 
    Details
    ISSN: 0006-3525
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Chemie und Pharmazie
    Notizen: Photon correlation spectroscopy was used to study both F-actin and F-actin/filamin networks in solution. The measured autocorrelation functions were analyzed with the inverse Laplace transform CONTIN. The resulting frequency distributions consist of maximal five relatively narrow peaks. This rather unexpected finding disagrees with the frequency spectra calculated for an entangled rigid rod model. For this model, we expect spectra consisting of a single broad peak. Factors like flexibility, deviation from an experimental length distribution, interference with chemical reactions, and translation rotation coupling that would influence the profile of the frequency distribution could be excluded by comparison of the data with model calculations or qualitative estimates. We conclude that our data for F-actin are consistent with the dynamics of an infinite network stable on the time scale of the observed modes. Further support for this interpretation is provided by a comparison with frequency spectra of actin/filamin networks. These appear to be very similar in shape. The main peak of these spectra that corresponds to the slow motions shifts to lower frequencies with increasing cross-link density. It appears that higher frequency modes of the gel are more efficiently damped with progressive cross-link density, resulting in a predominance of the slow motions in the spectra. This behavior has been already found in other systems and seems to be a general feature of cross-linked systems.
    Zusätzliches Material: 7 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/bip.360300704
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  • 7
    Digitale Medien
    Digitale Medien
    Fluorine-induced chemiluminescence detection of phosphine, alkyl phosphines and monophosphinate esters (1991)
    Springer
    Chromatographia 31 (1991), S. 342-346 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Chemiluminescence detection ; Phosphine derivatives ; Headspace analysis ; Fluorine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary Phosphine, alkylated phosphines and monophosphinate esters are detected with high sensitivity in capillary gas chromatography (GC) by their chemiluminescent reactions with molecular fluorine. Detection limits are estimated to be 1.3 pg, 0.5 pg, 8 pg, and 17 pg for phosphine, trimethyl phosphine, trimethyl phosphinate ester, and triethyl phosphine, respectively. As found earlier with alkylated sulfur, selenium and tellurium compounds, the detector exhibits a linear response. For triethyl phosphine, a linear range of greater than three orders of magnitude was demonstrated. Emission spectra were obtained for the trimethyl phosphine and triethyl phosphine systems. Chemiluminescence emitters include electronically excited HCF, vibrationally excited HF, and an unknown species in the trimethyl phosphine system. Banded emission from vibrationally excited HF and a broad continuum were observed for both trimethyl phosphine and triethyl phosphine; however, HCF emission was observed only for TMP. Under the conditions employed, the principal emitter is HCF for trimethyl phosphine and HF and the unknown emitter for triethyl phosphine. This detector may have important applications in investigations of the biogeochemical cycling of phosphorus.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02262189
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  • 8
    Digitale Medien
    Digitale Medien
    Purity of carbon dioxide as limiting factor in trace-level analysis by on-line supercritical fluid extraction/capillary gas chromatography (1991)
    Springer
    Chromatographia 32 (1991), S. 543-545 
    Details
    ISSN: 1612-1112
    Schlagwort(e): Gas chromatography ; Supercritical fluid extraction ; GC detectors ; Purity of gases
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Summary The usefulness of several grades of carbon dioxide for online supercritical fluid extraction/capillary gas chromatography has been studied. If trace-level work has to be performed, no single grade can be recommended for all modes of detection studied. Good-quality carbon dioxide is available for use with flame ionization and thermionic detectors. With electron-capture detection, however, distinct problems still exist.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1007/BF02327900
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  • 9
    Digitale Medien
    Digitale Medien
    Einfluß der Oberflächenvorbehandlung auf das Wachstum von PACVD-TiN Schichten (1993)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 24 (1993), S. 86-90 
    Details
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Notizen: Ziel der Untersuchungen war die Analyse der Schichtwachstumsprozesse bei der plasmaunterstützten CVD-Abscheidung (PACVD) von Titannitridschichten auf Stählen im Niedertemperaturbereich ≤ 500°C.Im Vordergrund standen werkstoffkundliche Untersuchungen der verschiedenen Schichtwachstumsstadien, die sich als Funktion der Beschichtungsdauer ergeben. Die Herstellung der Schichten erfolgte in einer Puls-Plasma-CVD-Anlage. Um den gesamten Wachstumsprozeß vom Beginn der Abscheidung bis zum Wachstum geschlossener Schichten zu untersuchen, wurden die Proben bei konstanten Abscheidungsbedingungen jeweils unterschiedlich lange dem Reaktionsgasfluß ausgesetzt. Der Abbruch des Beschichtungsprozesses für die entsprechende Probe nach einer festgelegten Beschichtungszeit wurde durch die Verwendung eines Probenwechslers gewährleistet.Die Bildung der TiN-Schichten wurde an Proben aus dem Schnellarbeitsstahl S 6-5-2 (DIN 1.3343) im vergüteten Zustand untersucht. Es wurde festgestellt, daß bei diesem Substratwerkstoff zwei Oberflächenqualitäten mit unterschiedlich guten Anlagerungsbedingungen für, während der Vorbehandlung entstehende, adhäsive Verbindungen vorliegen. Die Bildung von Keimen und das Wachstum von Agglomeraten wird wesentlich durch diese Sorptionsschichten beeinflußt. Die Zahl der gebildeten Agglomerate ist bei Proben, die einer Vorbehandlung im Plasma ausgesetzt wurden, um den Faktor 10 größer als bei Proben, die während dieser Vorbehandlung abgedeckt waren. Es wurden neue Modellvorstellungen für die Entstehung und das Wachstum von Schichten entwickelt.
    Zusätzliches Material: 15 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mawe.19930240306
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  • 10
    Digitale Medien
    Digitale Medien
    Hochtemperaturverhalten von Werkstoffen aus neuartig gefertigten GasturbinenschaufelnDieser Aufsatz ist dern Gedenken an den viel zu früh verstorbenen Herrn Dipl.-Ing. Karl Heinz Keienhurg gewidmet, der als Federführer der Vorhabengruppe “Herstellung von Gasturbinenschaufeln” ganz wesentlich an der Gemeinschaftsarbeit beteiligt war (1994)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 25 (1994), S. 235-243 
    Details
    ISSN: 0933-5137
    Schlagwort(e): Chemistry ; Polymer and Materials Science
    Quelle: Wiley InterScience Backfile Collection 1832-2000
    Thema: Maschinenbau
    Beschreibung / Inhaltsverzeichnis: High temperature behaviour of materials for gas turbine blades manufactured in new technologyOn gas turbine blades for the middle and last stages of stationary gas turbines, the service-relevant material properties were examined. The specimens were taken from forged blades of alloys Nimonic 101 and Udimet 720 and from two fine grain versions of cast blades of alloy IN-792. In the range of service relevant temperatures long-term creep rupture tests, annealing tests, relaxations tests as well as low and high cycle fatigue tests were carried out.
    Notizen: An in neuer Technologie gefertigten Schaufeln für die mittleren bis hinteren Laufreihen von stationären Gasturbinen wurden betriebsrelevante Werkstoffeigenschaften bestimmt. Die Untersuchungen erfolgten an den Schmiedelegierungen Nimonic 101 and Udimet 720 und an zwei Feinkornvarianten der Gußlegierung IN-792. Im Bereich der Anwendungstemperaturen wurden Langzeitstandversuche, Glühversuche, Relaxationsversuche sowie nieder- und hochfrequente zyklische Versuche durchgeführt.
    Zusätzliches Material: 13 Ill.
    Materialart: Digitale Medien
    URL: http://dx.doi.org/10.1002/mawe.19940250606
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