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  • 11
    Electronic Resource
    Electronic Resource
    Thermally stimulated depolarization currents in poly(acrylamide) films (1991)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 42 (1991), S. 379-383 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Der Mechanismus der Ladungsspeicherung in Poly(acrylamid)-Filmen wurde mit der Methode der thermisch stimulierten Depolarisationsströme (TSDC) untersucht. Die TSDC wurden in Abhängigkeit von der Feldstärke, der Temperatur und der Dauer der Polarisation bei verschiedenen Aufheizgeschwindigkeiten gemessen. Bei niedrigen Polarisationstemperaturen wurde in den TSDC-Spektren nur ein Peak gefunden, bei höheren Polarisationstemperaturen traten zwei Peaks auf. Der erste Peak wurde der Dipolorientierung, der zweite der Raumladungspolarisation zugeordnet.
    Notes: The charge storage mechanism in poly(acrylamide) films was studied by means of the technique of thermally stimulated depolarization currents (TSDC). The TSDC were measured as a function of field strength, temperature and time of polarization in dependence on the heating rate. One peak was observed on the TSDC spectra at low polarizing temperatures, while two peaks occurred for higher polarizing temperatures. The first peak was attributed to dipole orientation and the second one to space charge polarization.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1991.010420809
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  • 12
    Electronic Resource
    Electronic Resource
    Electrical conduction in pure and doped poly(acrylamide) films (1991)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 42 (1991), S. 465-469 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die stationäre elektrische Leitung in aus der Lösung erhaltenen Poly(acrylamid)-Filmen wurde im Temperaturbereich von 303 bis 450 K bei unterschiedlichen Feldstärken untersucht. Es wurde festgestellt, daß die Richardson-Schottky- und Poole-Frenkel-Mechanismen gleichzeitig auftreten. In mit Eosin bzw. Rhodamin B dotierten Filmen wurde die elektrische Leitung der Bildung von Charge-Transfer-Komplexen zugeschrieben.
    Notes: The steady state electrical conduction in solution grown poly(acrylamide) films was investigated in the temperature range 303 to 450 K at different field strengths. It was found that the Richardson-Schottky and Poole-Frenkel mechanisms operate simultaneously. In films doped with cosin and rhodamine B, respectively, the electrical conduction was attributed to the formation of charge transfer complexes.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1991.010420915
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  • 13
    Electronic Resource
    Electronic Resource
    Charge transport mechanism in poly(vinyl alcohol) - poly(vinyl pyrrolidone) polyblend films (1990)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 41 (1990), S. 583-586 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Films aus Mischungen von Poly(vinylalkohol) und Poly(vinylpyrrolidon) wurden aus Lösungen der Homopolymere hergestellt. Die stationäre elektrische Leitung wurde im Temperaturbereich 309 K bis 450 K bei Feldstärken von 0,75 bis 46,5 · 106 V/m unter Verwendung unterschiedlichen Elektrodenmaterials untersucht. Der Ladungstransport wird mit der Injektion von Ladungsträgern aus dem Elektrodenmaterial in das Dielektrikum nach einem Richardson Schottky-Mechanismus und nachfolgendem Einfangen und Freisetzung nach dem Poole-Frenkel-Mechanismus erklärt.
    Notes: Polyblend films of poly(vinyl alcohol) and poly(vinyl pyrrolidone) were prepared from solutions of the homopolymers. The steady-state electrical conduction was studied in the temperature range from 309 K to 450 K at the field strength of 0.75 to 46.5 · 106 V/m using different electrode materials. The charge transport is attributed to the injection of charge carriers from the electrode materials into the dielectric according to the Richardson-Schottky mechanism and their subsequent trapping and release according to the Poole-Frenkel mechanism.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1990.010411108
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  • 14
    Electronic Resource
    Electronic Resource
    Thermally stimulated depolarization currents in poly(vinyl alcohol) films (1992)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 43 (1992), S. 68-71 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Poly(vinylalkohol)-Filme wurden bei unterschiedlichen elektrischen Feldstärken und Temperaturen polarisiert. Die Peaktemperatur der TSDC-Spektren verschob sich mit steigender Polungsfeldstärke und Polungstemperatur zu höheren Werten. Die Aktivierungsenergien und die Relaxationsparameter des Prozesses wurden ermittelt. Auf Grund der Ergebnisse wurde der Ursprung der TSDC der Raumladungspolarisation mit einem geringen von der Dipolorientierung herrührenden Beitrag zugeordnet.
    Notes: Poly(vinyl alcohol) films were polarized at different electrical field strengths and temperatures. The peak temperature of the TSDC spectra shifted to higher values with increasing polarizing field strength and polarizing temperature. The activation energies and relaxation parameters of the process were evaluated. Based on the results, the origin of TSDC was attributed to space charge polarization with some contribution of dipole orientation.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1992.010430202
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  • 15
    Electronic Resource
    Electronic Resource
    Copolymerization reactivity ratios of N,N-dimethyl acrylamide and isopropyl methacrylate determined by 1H-NMR spectroscopy (1991)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 192 (1991), S. 51-55 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: N,N-Dimethylacrylamid (DMA) und Isopropylmethacrylat (IPM) wurden in Dimethylformamid mit Azoisobutyronitril als Initiator copolymerisiert. Die Copolymerzusammensetzung wurde 1H-NMR-spektroskopisch ermittelt. Die Copolymerisationsparameter (rDMA = 0,58, rIPM = 2,76) wurden nach Kelen-Tüdős berechnet.
    Notes: Copolymers of N,N-dimethyl acrylamide (DMA) and isopropylmethacrylate (IPM) were prepared in dimethyl formamide using azoisobutyronitrile as initiator. The composition of copolymers was determined by 1H-NMR analysis. Reactivity ratios (rDMA = 0.58, rIPM = 2.76) were calculated from these values by using the Kelen-Tüdős differential linear equation.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1991.051920104
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  • 16
    Electronic Resource
    Electronic Resource
    Conformations of dinucleoside monophosphates in relation to duplex DNA structures (1986)
    New York : Wiley-Blackwell
    Biopolymers 25 (1986), S. 17-30 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Mononucleotide conformations are important in understanding the structural aspects of nucleic acids and polynucleotides. In order to study the influence of stacking interactions between adjacent bases in a polynucleotide on the preferred conformations of mononucleotides, conformational energy calculations have been carried out on dinucleoside monophosphate fragments. Four base sequences - d(ApT), d(TpA), d(CpG), and d(GpC) -  have been analyzed in the framework of helical structures. Flexibility of the furanose ring has been incorporated in the investigations. Energetically favored conformers of the four compounds correspond to a variety of left- and right-handed uniform helical structures, similar to those of the commonly observed polymorphous forms. Implications of these investigations on the further understanding of double-helical polynucleotide conformations are briefly discussed.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360250104
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  • 17
    Electronic Resource
    Electronic Resource
    Reversal of the long-wavelength CD band of poly(dI-dC) · poly(dI-dC) on specific interaction with the 53-58 peptide fragment of the lac repressor (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 329-332 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360260302
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  • 18
    Electronic Resource
    Electronic Resource
    Molecular mechanical studies on left- and right-handed B-DNA (1987)
    New York : Wiley-Blackwell
    Biopolymers 26 (1987), S. 403-414 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular mechanical simulations on base-paired deoxyhexanucleoside phosphates, (dAdT)3 · (dAdT)3, (dTdA)3 · (dTdA)3, (dGdC)3 · (dGdC)3, and (dCdG)3 · (dCdG)3, have been carried out to assess their energetic stabilities in left- and right-handed forms. These hexamers have also been simulated with alternating sugar-puckering profiles with the combinations (purine : C2′-endo-pyrimidine : C3′-endo) and (purine : C3′-endo-pyrimidine C2′-endo). The right-handed models have been found to be the energetically most stable structures and the left-handed structures are significantly destabilized. This instability has been rationalized in terms of competition between stabilizing stacking interactions on one hand, and distortions in the bond angles and torsion angles in the sugar-phosphate backbone on the other.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360260308
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  • 19
    Electronic Resource
    Electronic Resource
    Effects of nucleotide bromination on the stabilities of Z-RNA and Z-DNA: A molecular mechanics/thermodynamic perturbation study (1989)
    New York : Wiley-Blackwell
    Biopolymers 28 (1989), S. 1939-1957 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The structures of ZI- and ZII- form RNA and DNA oligonucleotides were energy minimized in vacuum using the AMBER molecular mechanics force field. Alternating C-G sequences were studied containing either unmodified nucleotides, 8-bromoguanosine in place of all guanosine residues, 5-bromocytidine in place of all cytidine residues, or all modified residues. Some molecules were also energy minimized in the presence of H2O and cations. Free energy perturbation calculations were done in which G8 and C5 hydrogen atoms in one or two residues of Z-form RNAs and DNAs were replaced in a stepwise manner by bromines. Bromination had little effect on the structures of the energy-minimized molecules. Both the minimized molecular energies and the results of the perturbation calculations indicate that bromination of guanosine at C8 will stabilize the Z forms of RNA and DNA relative to the nonbrominated Z form, while bromination of cytidine at C5 stabilizes Z-DNA and destabilizes Z-RNA. These results are in agreement with experimental data. The destabilizing effect of br5C in Z-RNAs is apparently due to an unfavorable interaction between the negatively charged C5 bromine atom and the guanosine hydroxyl group. The vacuum-minimized energies of the ZII- form oligonucleotides are lower than those of the corresponding ZI- form molecules for both RNA and DNA. Previous x-ray diffraction, nmr, and molecular mechanics studies indicate that hydration effects may favor the ZI- conformation over the ZII- form in DNA. Molecular mechanics calculations show that the ZII-ZI energy differences for the RNAs are greater than three times those obtained for the DNAs. This is due to structurally reinforcing hydrogen-bonding interactions involving the hydroxyl groups in the ZII form, especially between the guanosine hydroxyl hydrogen atom and the 3′-adjacent phosphate oxygen. In addition, the cytidine hydroxyl oxygen forms a hydrogen bond with the 5′-adjacent guanosine amino group in the ZII- form molecule. Both of these interactions are less likely in the ZI- form molecule: the former due to the orientation of the GpC phosphate away from the guanosine ribose in the ZI form, and the latter apparently due to competitive hydrogen bonding of the cytidine 2′-hydroxyl hydrogen with the cytosine carbonyl oxygen in the ZI form. The hydrogen-bonding interaction between the cytidine hydroxyl oxygen and the 5′-adjacent guanosine amino group in Z-RNA twists the amino group out of the plane of the base. This may be responsible for differences in the CD and Raman spectra of Z-RNA and Z-DNA.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360281111
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  • 20
    Electronic Resource
    Electronic Resource
    Simulations of the B-DNA molecular dynamics of d(CGCGAATTCGCG)2 and d(GCGCGCGCGC)2: An analysis of the role of initial geometry and a comparison of united and all-atom models (1990)
    New York : Wiley-Blackwell
    Biopolymers 29 (1990), S. 517-532 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular dynamics simulations on the sequence d(CGCGAATTCGCG)2 have been carried out using both united atom and all-atom representations, and starting the simulations both from a regular repeating B-DNA structure and from the x-ray single crystal B-DNA structure. An all-atom B-DNA simulation on the sequence d(GCGCGCGCGC)2 has also been carried out, in order to compare it with a previous united atom simulation. The helix repeats, H-bonding, sugar pucker profiles, and average torsional angles are all in the range observed in crystallographic and nmr studies for B-DNA helices. In some of the sequences, there is a significant bend in the DNA helices. The individual helix repeats, with focus on 3′CpG5′ and 3′GpC5′ units, show the opposite helix repeat to that suggested by Calladine's rules.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290307
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