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  • Articles  (1,835)
  • Chemistry  (1,412)
  • Humans  (329)
  • Female  (159)
  • Analytical Chemistry and Spectroscopy  (129)
  • Cell & Developmental Biology
  • 1980-1984  (1,131)
  • 1970-1974  (392)
  • 1965-1969  (312)
  • Physics  (1,835)
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  • Articles  (1,835)
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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 17 (1973), S. 269-282 
    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 development of gel permeation chromatography (GPC) has provided a convenient tool for the rapid determination of molecular weight distribution. The question has arisen as to the suitability of the method for specification purposes. The present work, suggested by the Naval Air Systems Command, represents an attempt to assess the precision of the method through a series of tests carried out by a number of laboratories using identical procedures on the same samples. Ten laboratories agreed to take part. Naval Ordnance Station, Indian Head, worked out standard conditions for operation of the chromatograph, for calibration of the columns, and for analysis of the GPC curves. Two samples of polystyrene were used by the various organizations for calibration of their instruments. Number-average molecular weight, heterogeneity index, and cumulative molecular weight distribution curves were determined on four samples of carboxyl-terminated polybutadiene (CTPB) and two samples of hydroxyl-terminated polybutadiene (HTPB), all unidentified except by letter code. All laboratories used identical directions for setting up CTPB and HTPB calibration curves which were based on curves determined from vapor-pressure osmometer molecular weights and GPC count numbers of fractionated material. Variation among the different laboratories was 0.15 in heterogeneity index, and a maximum of 1200 in molecular weight provided one aberrant set of values was eliminated. The six samples had heterogeneity indices from 1.15 to 1.54, while molecular weight varied from approximately 3000 to 6000. The average coefficient of variation of the molecular weight values was 6.2 ± 0.7%, which is quite acceptable. Variation in heterogeneity index was too great for specification purposes when considered among the different laboratories, but may be sufficiently good when measured by any one laboratory.
    Additional Material: 7 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 16 (1972), S. 3353-3360 
    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: Two independently derived distribution function methods validate both the calibration curve and the dispersion correction of the “effective linear calibration” method used in gel permeation chromatography (GPC). Experimental conditions are specified for making the method more useful by permitting linear extrapolation of the calibration line, \documentclass{article}\pagestyle{empty}\begin{document}$ V_R = C_1 + C_2 \log M, $\end{document} and for using a minimum number of standards. The independent methods quantitatively relate known differential of integral distribution functions for standard samples to their respective chromatograms. As such, they are useful calibration methods also, but are limited in scope and range.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 169 (1973), S. 177-189 
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die elektroinitiierte Polymerisation von N-Vinylcarbazol (VCZ) wurde in Aceton bei 25°C mit Zinkbromid als Katalysator unter Verwendung von Platinelektroden eingehend untersucht. Die Polymerisationsgeschwindigkeit erwies sich als direkt abhängig von der Stromstärke, der Zinkbromid-Konzentration und dem anfänglichen Wassergehalt des Solvens.Die Molekulargewichte der entstandenen Polymeren (1000-6000) sind unabhängig von der Stromstärke, der Zinkbromid-Konzentration und dem Umsetzungsgrad des Monomeren zum Polymeren, werden jedoch beeinflußt durch Wasser, die Monomerkonzentration und das Elektrodenmaterial. Die chemische Zusammensetzung der Polymeren ändert sich nicht mit der Stromstärke, der Zinkbromid-Konzentration, dem Umsetzungsgrad und dem Elektrodenmaterial. Sie ändert sich jedoch ein wenig mit dem Wassergehalt des Acetons.
    Notes: The electroinitiated polymerization of N-vinylcarbazole (VCZ) in acetone solvent at 25°C with zinc bromide, as catalyst, and platinum electrodes was investigated in detail. The polymerization rate was found to be directly dependent on current strength, zinc bromide concentration and the initial water content of the solvent.The molecular weights of the formed polymers (1000-6000) are independent of current strength, zinc bromide concentration and degree of conversion of monomer to polymer, but are affected by water, monomer concentration, and by the type of electrodes used. The chemical composition of the polymer is invariant with current strength, zinc bromide concentration, degree of conversion, and electrode material but does vary slightly with the water content of acetone.
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  • 4
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 18 (1974), S. 3543-3553 
    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: An analytical procedure for determining the antioxidant (i.e., Akroflex CD) content in neoprene rubber has been developed. The method is based on the infrared absorption analyses of chloroform extractables from the cured rubber at 1600 cm-1 and 1300 cm-1. Good agreement is found between these two independent sets of measurements. In an attempt to elucidate the antioxidant loss mechanism found with neoprene, thermal aging studies were carried out over the temperature range of 80°-200°C. Using the infrared analytical procedure, antioxidant loss rates at the different temperatures were established. The activation energy value (5.1 kcal/mole) for the loss rate as well as other aging data suggest that the antioxidant is lost by a diffusion mechanism.
    Additional Material: 9 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 26 (1981), S. 509-519 
    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 deterioration of polyolefin, poly(ethylene terephthalate), and polyamide films under soil burial conditions extending up to 32 months has been investigated. Based on changes in their elongation at break, the films can be ranked in order of increasing sensitivity to degradation: Polyester ≃ polypropylene 〈 low-density polyethylene ≃ high-density polyethylene 〈 nylon 6.6. The degraded nylon 6.6 and polyethylene films were characterized by infrared and luminescence spectroscopy and scanning electron microscopy, as well as by wet analysis for hydroperoxides. From a comparison with the well-known oxidative sensitivity of nylon 6.6 in oxygenated water at slightly elevated temperatures, the rapid deterioration of nylon 6.6 film during soil burial was also concluded to be an oxidative process. The somewhat smaller, but significant, embrittlement of the polyethylenes studied could not be simply explained by thermal oxidation (with only trace oxidation products detectable) or microbiological attack (deterioration being unaffected by surface activation to enhance wettability).
    Additional Material: 5 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 2 (1980), S. 5-10 
    ISSN: 0142-2421
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: Mean free paths for inelastic scattering (λ) of low energy electrons in poly(methylmethacrylate) (PMMA) have been determined by measuring Al Kα excited C 1s and Si 2s photoelectron signal intensities as a function of ellipsometrically determined thicknesses of PMMA overlayers on silicon substrates. The λ values obtained are 29 ± 4 Å for 1196 eV electrons and 33 ± 5 Å for 1328 eV electrons. These data are necessary for the quantitative analysis of the surface region of PMMA and similar polymers by X-ray photoelectron spectroscopy (XPS). The magnitude of the λ values determined indicates that XPS measurements can provide chemical information about the surface region of polymers, such as PMMA, in the depth range of ∼6 to 100 Å. The results of this study are compared and discussed with respect to λ values determined for other organic compounds.
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  • 7
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 9 (1980), S. 230-238 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The IR spectra (1400 cm-1 to 160 cm-1) of the gases at ambient temperature and the Raman spectra (below 1400 cm-1) of the liquids near -196°C are reported for CF3OF and CF3OCl. All fundamentals are assigned under Cs symmetry and the results of a normal coordinate analysis are presented. The assignments of Smardzewski and Fox are adopted with one exception for both CF3OF and CF3OCl: the CF3 rock of A″ symmetry is assigned near 430 cm-1 and the two bands between 200 cm-1 and 300 cm-1 are assigned to an A′ fundamental, involving CF3 rocking and COX bending and a Δν=2 transition in the CF3 torsion. An extra band at 548 cm-1 in the Raman spectrum of liquid CF3 COl near -196°C is assigned to a CF3OCl⃛Cl2 complex. The values of the force constants d(OX) for CF3OX molecules are suggested to be near those for X2O molecules. More than half the normal modes of A′ symmetry show extensive mixing of symmetry coordinates. In some of these cases the symmetry coordinate for which the normal mode is named is the largest but not the dominant contributor to the potential energy distribution, while in others this symmetry coordinate is not even the largest contributor to the potential energy distribution. No normal modes of A′ symmetry are present in which ν(CO), δs(CF3), δ(COX), or δ(CF3) symmetry coordinates are dominant, and the mode conventionally labeled as v(CO) should be labeled as νs(CF3). For the remaining A′ normal modes and all the A″ normal modes, the symmetry coordinate for which the normal mode is named is dominant in the potential energy distribution.
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  • 8
    Electronic Resource
    Electronic Resource
    Chichester [u.a.] : Wiley-Blackwell
    Journal of Raman Spectroscopy 14 (1983), S. 144-149 
    ISSN: 0377-0486
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Raman spectra of thallous carbonate have been studied to c. 52 kbar and mid-IR spectra to 36 kbar. Details of the assignment have also been established using single-crystal IR reflectance and Raman spectroscopy. Phase transitions were found near 13 and 38 kbar on the basis of the Raman evidence, thus supporting the earlier conclusions of Meisalo and Kalliomaki based on x-ray powder and optical results. Analysis of possible space group relations between phases III (ambient) and IV showed that IV must be orthorhombic and adopt one of the D2hn groups, where n = 17, 19, 21, 25 or 28. Structural relationships between the phases are discussed.
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  • 9
    Publication Date: 1981-12-04
    Description: Leucine catabolism is regulated by either of the first two degradative steps: (reversible) transamination to the keto acid or subsequent decarboxylation. A method is described to measure rates of leucine transamination, reamination, and keto acid oxidation. The method is applied directly to humans by infusing the nonradioactive tracer, L-[15N,1-13C]leucine. Leucine transamination was found to be operating several times faster than the keto acid decarboxylation and to be of equal magnitude in adult human males under two different dietary conditions, postabsorptive and fed. These results indicate that decarboxylation, not transamination, is the rate-limiting step in normal human leucine metabolism.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Matthews, D E -- Bier, D M -- Rennie, M J -- Edwards, R H -- Halliday, D -- Millward, D J -- Clugston, G A -- AM-25994/AM/NIADDK NIH HHS/ -- HD-10667/HD/NICHD NIH HHS/ -- RR-00954/RR/NCRR NIH HHS/ -- New York, N.Y. -- Science. 1981 Dec 4;214(4525):1129-31.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/7302583" target="_blank"〉PubMed〈/a〉
    Keywords: Adult ; Carbon Isotopes ; Humans ; Kinetics ; Leucine/*metabolism ; Male ; Models, Biological ; Nitrogen Isotopes ; Oxidation-Reduction
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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  • 10
    Publication Date: 1983-12-23
    Description: Endotoxin-free thymosin fraction 5 elevated corticotropin, beta-endorphin, and cortisol in a dose- and time-dependent fashion when administered intravenously to prepubertal cynomolgus monkeys. Two synthetic component peptides of thymosin fraction 5 had no acute effects on pituitary function, suggesting that some other peptides in thymosin fraction 5 were responsible for its corticotropin-releasing activity. In agreement with these observations, total thymectomy of juvenile macaques was associated with decreases in plasma cortisol, corticotropin, and beta-endorphin. These findings indicate that the prepubertal primate thymus contains corticotropin-releasing activity that may contribute to a physiological immunoregulatory circuit between the developing immunological and pituitary-adrenal systems.〈br /〉〈span class="detail_caption"〉Notes: 〈/span〉Healy, D L -- Hodgen, G D -- Schulte, H M -- Chrousos, G P -- Loriaux, D L -- Hall, N R -- Goldstein, A L -- CA 24974/CA/NCI NIH HHS/ -- New York, N.Y. -- Science. 1983 Dec 23;222(4630):1353-5.〈br /〉〈span class="detail_caption"〉Record origin:〈/span〉 〈a href="http://www.ncbi.nlm.nih.gov/pubmed/6318312" target="_blank"〉PubMed〈/a〉
    Keywords: Adrenocorticotropic Hormone/*blood ; Animals ; Dose-Response Relationship, Drug ; Endorphins/blood ; Female ; Hydrocortisone/blood ; Kinetics ; Macaca fascicularis ; Thymectomy ; Thymosin/analogs & derivatives/*pharmacology ; Thymus Gland/*physiology ; beta-Endorphin
    Print ISSN: 0036-8075
    Electronic ISSN: 1095-9203
    Topics: Biology , Chemistry and Pharmacology , Computer Science , Medicine , Natural Sciences in General , Physics
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