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  • Polymer and Materials Science  (391)
  • ASTROPHYSICS  (222)
  • 1980-1984  (613)
  • 1970-1974
  • 1981  (326)
  • 1980  (287)
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  • 1980-1984  (613)
  • 1970-1974
Year
  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 2783-2786 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 1511-1517 
    ISSN: 0021-8995
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: The hardening process of natural (Hevea brasiliensis) rubber, that takes place when this rubber is stored in dry conditions over long periods of time, has been correlated with the presence of reactive “abnormal” groups directly grafted on the polymeric chain and in the serum of the latex. In the present work, natural Hevea (HR) and Guayule (Parthenium argentatum) rubber (GR) were stored under accelerated conditions and the changes in Mooney viscosity and molecular weight measured. The results showed that while HR undergoes hardening, GR keeps its Mooney viscosity constant, as does a constant viscosity (CV) Hevea rubber. These results are explained by the absence of functional “abnormal” groups that sustain the hardening reactions.
    Additional Material: 4 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Acta Polymerica 32 (1981), S. 465-466 
    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: The deformation stability of polybutylene terephthalate in dependence on stress and temperature was determined. The lifetime of the polymer is described as a function of these parameters. The results are compared with the values obtained with other polymers.
    Notes: Die Deformationsstabilität von Polybutylenterephthalat wurde in Abhängigkeit von der Spannung und der Temperatur bestimmt. Die Lebensdauer des Polymers kann als eine Funktion dieser Parameter angegeben werden. Die Ergebnisse werden mit den an anderen Polymeren erhaltenen Werten verglichen.
    Additional Material: 4 Ill.
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  • 4
    Publication Date: 2019-06-28
    Description: The 1.24-sec pulsations of Her X-1 in the energy range 13-75 keV have been analyzed in data obtained from the UCSD/MIT experiment on HEAO 1 during observations of the source on three dates in February 1978 and three in August 1978. Observational results are (1) the main pulse broadens somewhat with increasing energy; (2) the pulsation light curve undergoes pronounced changes at the leading edge of the main pulse from day to day; (3) spectral hardening within the main pulse is confirmed; (4) a 40-60 keV spectral feature in the spectrum is confirmed; (5) this feature is resolved, the pulse width broadening is greater than 20%, and its centroid varies with pulsation phase; and (6) the 13-75 keV spectrum does not noticeably vary from day to day, except for an overall intensity factor. Some implications of these results for the prevailing models of Her X-1 and the HZ Her-Her X-1 system are briefly discussed.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 240
    Format: text
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  • 5
    Publication Date: 2019-06-28
    Description: On five occasions in 1977 and 1978, Cygnus X-1 was observed using the low-energy detectors of the UCSD/MIT Hard X-ray and Low-Energy Gamma Ray experiment on the HEAO 1 satellite. Rapid (times between 0.08 and 1000 sec) variability was found in the 10-140 keV band. The power spectrum was white for frequencies between 0.001 and 0.05 Hz and was proportional to the inverse of the frequency for frequencies between 0.05 and 3 Hz, indicating correlations on all time scales less than approximately 20 s. The shape of the energy spectrum was correlated with intensity; it was harder at higher intensity. If the emission is produced by Comptonization of a soft photon flux in a hot cloud, the heating of the cloud cannot be constant; it must vary on time scales up to approximately 20 s. A variable accretion rate could cause the observed effects.
    Keywords: ASTROPHYSICS
    Type: Astrophysical Journal; vol. 246
    Format: text
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  • 6
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Measurement of the equilibrium distribution of persistence length fragments of DNA in high concentration in the ultracentrifuge shows that the reduced osmotic pressure rises much faster than linearly. From analysis of the data in terms of the Zimm cluster integral we infer that the net interactions between helices are purely repulsive at all distances. A theoretical equation of state derived from scaled particle theory with one adjustable parameter is in excellent agreement with the experimental data so long as the salt concentration is not excessively low. The parameter represents the hard-core radius in a simplified approximation to the potential function for the electrostatic repulsion between helices. Its value depends on the salt concentration, and it shrinks at high salt to a radius in close agreement with direct structural estimates. At a particular value of the osmotic pressure that is only slightly salt dependent, the solution undergoes a reversible transition to a denser, turbid, optically anisotropic phase. The relation between DNA volume fraction, including the electrostatic radius, at the transition point and the effective asymmetry of the molecules as a function of salt is in approximate correspondence with various theoretical treatments. However, the experimental function extrapolates to the correct limit for spherical particles. The work needed to bring DNA to a high concentration is estimated. The results suggest that the phase transition is first order.
    Additional Material: 7 Ill.
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  • 7
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Poly(hydroxyalkyl-L-glutamine) (alkyl = ethyl, propyl, butyl) solutions have been studied by CD as functions of temperature and activity of calcium chloride and sodium perchlorate. Helical content is altered by changes in salt activity and temperature. The helicity of poly(hydroxybutyl-L-glutamine) and poly(hydroxypropyl-L-glutamine) falls to zero in a monotonic fashion with increasing calcium chloride activity. A nonzero helicity reappears at activities in excess of 5-50 mol kg-1. Poly(hydroxypropyl-L-glutamine) is much more sensitive to calcium chloride than is poly(hydroxybutyl-L-glutamine), and both polypeptides are more sensitive to calcium chloride than are typical proteins. Markedly different behavior is observed with sodium perchlorate. This salt acts as a helix stabilizer at low activities but becomes a destabilizer at activities higher than 0.3-1.0 mol kg-1. In this respect the effect of sodium perchlorate on nonionic poly(hydroxyalkyl-L-glutamines) resembles that seen with cationic poly(L-lysine) and poly(L-arginine). Helix stabilization at low sodium perchlorate activity is moderate for poly(hydroxybutyl-L-glutamine) and large for poly(hydroxypropyl-L-glutamine) and poly(hydroxyethyl-L-glutamine).
    Additional Material: 16 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 20 (1981), S. 853-864 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have estimated the absorption of microwave radiation by the four acoustic modes of poly(dG)·poly(dC) in B conformation. The eigenvectors used in this calculation are those obtained from a refined normal coordinate analysis by fitting the velocity of the longitudinal acoustic mode to that observed by Brillouin scattering. The acoustic modes couple to the radiation field when translational invariance is broken such as for finite segments of helix and as may be the case in vivo. Calculations for various helix lengths show that the estimated absorption is greater than that of water by at least two to three orders of magnitude in some cases.
    Additional Material: 5 Ill.
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  • 9
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Simultaneous curve fitting for the ionization parameters of oxidized and reduced horse heart cytochrome c in 0.15M KCl and 20°C yields values for the ionization constants (as pK′) and the heats of ionization (ΔHi) which can reconstruct either the potentiometric or thermal titration curves. Reduced cytochrome c requires 8 sets of groups, whereas oxidized cytochrome c requires 10 sets of groups. The additional groups in the oxidized preparation appear to involve the ferriheme (pK′, 9.25; ΔHi, 13.7 kcal/mol) and a tyrosine (pK′ ≃ 10.24) that is not present in the reduced form. The potentiometric and thermal difference curves (reduced - oxidized) involve the appearance of 17 kcal/mol centered at pH 9.7 and 5.8 kcal/mol centered at pH 4.9. The carboxyl groups in both species appear to be normal for the hydrogen-bonded form. Only one histidine has normal ionization properties (pK′, 6.7; ΔHi, 7.5 kcal/mol), as do 17 of the lysine residues (pK′, 10.8; ΔHi, 11.5 kcal/mol).
    Additional Material: 4 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 181 (1980), S. 453-467 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Existing evidence suggests that the solid-state polymerization of disubstituted diacetylenes is controlled by (a) the packing of the monomeric units in the crystal lattice, and (b) the elastic strain which is present in partially polymerized crystals. To investigate these ideas further, a number of closely related bis(arylsulfonate) derivatives of 2,4-hexadiyne-1,6-diol, analogous materials to the extensively investigated bis(p-toluenesulfonate) ester of this diol, have been synthesized, and their solid-state reactivity studied. Topochemical polymerization was observed only for those compounds with benzenesulfonate and p-methoxybenzenesulfonate substituents. In the case of the latter, structurally different reactive and unreactive crystalline modifications were obtained. Polymerization kinetics for the reactive modification differ strikingly from those of the p-toluenesulfonate compound, despite the fact that the initial elastic strains in the two materials appear comparable.
    Additional Material: 9 Ill.
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