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  • Polymer and Materials Science  (82)
  • Electron microscopy  (4)
  • 1990-1994  (68)
  • 1975-1979  (18)
  • 1930-1934
  • 1
    Electronic Resource
    Electronic Resource
    Determination of the base-pairing content of four specific tRNAs by infrared spectroscopy (1977)
    New York : Wiley-Blackwell
    Biopolymers 16 (1977), S. 1735-1745 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Infrared spectroscopy was used for the determination of the base-pairing content of four specific tRNAs in deuterium oxide solution. Infrared spectra were obtained in the 1750-1550 cm-1 region at various temperatures ranging from about 15 to 90°C. Melting curves were constructed by plotting the molar extinction coefficient at ν = 1657 cm-1 versus temperature. These transition curves enabled us to determine the ranges of temperature which correspond to the ordered (partially double-stranded) or randomly coiled structure of the tRNA. For a set of wavenumbers the extinction coefficients at these temperatures were used for the calculation of the base-pairing content. The procedure employed here is based on a method described earlier by Thomas [(1969) Biopolymers 7, 325-334]. For the conditions selected for this investigation (Mg2+-free D2O-buffer; 0.01M tris-DCl, 0.015M NaCl, pD 7.5) the results of this determination agree within the limits of errors with the number of base pairs predicted by the cloverleaf model.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.1977.360160810
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  • 2
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300123
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  • 3
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360290404
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  • 4
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300912
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  • 5
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360310702
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  • 6
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 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.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360300704
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  • 7
    Electronic Resource
    Electronic Resource
    Free radicals in colloidal systems: Formation and decay of radicals in the tensides α-hexadecyl-ω-hydroxypoly(oxyethylene) and α-tetradecyl-ω-(sodium sulfonato)tri(oxyethylene) (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 2279-2295 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Organic radicals were produced in the tensides C16H33(OCH2CH2)21OH and C14H29(OCH2CH2)3-SO3Na in aqueous solutions using a short pulse of high energy electrons. The radicals were formed by OH attack on the (OCH2CH2)x-parts of the tensides. The decay of the 250nm absorption of the radicals was recorded at different initial radical concentrations and tenside concentrations. Several radicals could be produced in one micelle. Radicals formed in the same micelle decay within microseconds or faster. The half life time τ1 in a micelle carrying two radicals is 2,0·10-6 s for C16H33(OCH2CH2)21 OH and less than 6·10-7 s for C14H29(OCH2CH2)3SO3Na. A model for intramicellar radical-radical reactions is proposed according to which the rate is faster in tensides of high critical micelle concentration. Single radicals in micelles of C16H33(OCH2CH2)21OH can deactivate each other without leaving the micelles. This intermicellar reaction is discussed in terms of the rate of diffusion-controlled micelle-micelle encounters, an encounter time of 7·10-8s, and the above time τ1 for intramicellar reaction. The observed rate constant 2k of intermicellar reaction is 3,5·106 mol-1·l·s-1. At low tenside concentrations, the bimolecular rate constant increases since more single tenside radicals are present in solution. They react rapidly (ca. 108 mol-1·l·s-1) with radicals in micelles. Single radicals in C14H33(OCH2CH2)3-SO3Na micelles cannot directly react with each other because of the Coulombic repulsion between two anionic micelles. Reaction occurs after the exit of a tenside radical from its micelle, the rate of which depends on the micellar equilibrium Mn⇄Mn-1+M (M: tenside molecule; n: agglomeration number of micelle). A single radical in solution reacts with a single radical in a micelle with 2k = 1,0·108 mol-1·l·s-1 and with another single radical in solution with 4,0·107 mol-1·l·s-1.γ-Irradiation of both tensides in aqueous solution leads to slight increases in viscosity, followed by turbidity beyond the “gel dose” and phase separation. These effects are explained in terms of crosslinking of tenside molecules. Formation of a large network requires bridges between all participating tenside molecules (not only bridges between micelles).
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1978.021790915
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  • 8
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
    Additional Material: 15 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19930240306
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  • 9
    Electronic Resource
    Electronic Resource
    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
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: 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.
    Notes: 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.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19940250606
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  • 10
    Electronic Resource
    Electronic Resource
    Form und Mechanismen von Rissen und Brüchen unter gleichzeitiger korrosiver und dynamischer Beanspruchung mit unterschiedlichen Frequenzen (1978)
    Weinheim : Wiley-Blackwell
    Materialwissenschaft und Werkstofftechnik 9 (1978), S. 406-413 
    Details
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Form and Mechanisms of Cracks and Fractures Caused by Simultaneous Corrosive and Dynamic Stress under Various FrequenciesDistinction of crack nucleation and crack propagation under variable frequencies and electrolytic corrosion. Relationship between crack nucleation and frequency due to differing sliding mechanisms. Crack propagation under decreasing frequencies causes transition from corrosion fatigue to cyclic stress corrosion cracking and finally stress corrosion cracking can be observed. Coordination of that transition with the increasing influence of the KISCC-value as determinant of the crack propagation.The influence of frequency on high temperature materals in hot gas atmosphere is mainly determined by creep mechanisms during top-load phase and the gas-metal-reactions. Accordingly the life time increases with growing load frequency.
    Notes: Anrißphase und Phase des Rißfortschritts bei der Betrachtung der Frequenzabhängigkeit unter elektrolytischer Korrosion. Abhängigkeit der Anrißphase von der Frequenz infolge unterschiedlicher Gleitmechanismen. Beim Rißfortschritt erfolgt mit sinkender Frequenz Übergang von Schwingungsrißkorrosion zu zyklischer Spannungsrißkorrosion und schließlich zu Spannungsrißkorrosion. Zuordnung dieses Übergangs zum zunehmenden Einfluß des KISCC-Wertes als Bestimmungsgröße für den Bruchvorgang.Frequenzabhängigkeit bei Hochtemperaturwerkstoffen in Heißgasatmosphäre im wesentlichen bestimmt durch Kriechvorgänge bei Einwirkung der Oberlast und zeitabhängige Gas-Metall-Reaktionen. Entsprechend verlängern sich die Standzeiten mit zunehmender Belastungsfrequenz.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mawe.19780091108
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