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  • 1
    Electronic Resource
    Electronic Resource
    Epoxy resin cure. II. FTIR analysis (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 3713-3726 
    Details
    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: Fourier transform infrared (FTIR) spectroscopy is used to determine the cure rate of an epoxy resin consisting of Tetraglycidyl-4,4′-diaminodiphenyl methane (TGDDM) and diaminodiphenylsulfone (DDS). Cure rates at 120 and 160°C are shown to increase noticeably when 1% BF3-MEA is added to either TGDDM to TGDDM plus DDS. Fluoroboric acid is shown to increase the cure rates even more than the BF3-MEA. These Results combined with the NMR results in the accompanying article indicate that BF3-MEA is not a catalyst for epoxy resin cure. Instead it is rapidly hydrolyzed to fluoroboric acid which acts as the catalyst.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070291207
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  • 2
    Electronic Resource
    Electronic Resource
    Epoxy resin cure. I. Fluorine-19 NMR of boron trifluoride monoethylamine and fluoroboric acid (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 29 (1984), S. 3697-3711 
    Details
    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: Fluorine-19 NMR is used to examine the role of boron trifluoride monoethylamine (BF3-MEA) in epoxy resin cure. Spectra were first recorded in a variety of solvents suitable for dissolving different epoxy resins. All spectra contained a peak due to fluoroboric acid. Spectra of BF3-MEA in orthodichlorobenzene were then recorded at elevated temperatures. The floroboric acid peak area increased, indicating that the BF3-MEA was being hydrolyzed. Results indicate that, at temperatures above 100°C, BF3-MEA is completely hydrolyzed within 5 min to fluoroboric acid.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1984.070291206
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  • 3
    Electronic Resource
    Electronic Resource
    Stimulation of the hexosemonophosphate-pentose pathway by pyrroline-5-carboxylate in cultured cells (1982)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 110 (1982), S. 255-261 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Δ1-Pyrroline-5-carboxylic acid, an intermediate in the interconversions of proline, ornithine, and glutamate, is a potent stimulator of glucose oxidation through the hexosemonophosphate-pentose pathway. The effect is observed in cultured human fibroblasts, Chinese hamster ovary cells (CHO-K1), and rabbit kidney cells (LLC-RK1). In human fibroblasts, the magnitude of the stimulation of the hexosemonophosphate-pentose pathway is dependent on the concentration of added pyrroline-5-carboxylate and the effect is observed over a wide range of glucose concentrations. The mechanism of the effect is related to the generation of oxidizing potential in the form of NADP+ by pyrroline-5-carboxylate reductase concomitant with the conversion of pyrroline-5-carboxylate to proline. In LLC-RK1 cells, a cell line unique in having proline oxidase activity, proline also stimulated hexosemonophosphate-pentose pathway activity. Although pyrroline-5-carboxylate markedly stimulated the hexosemonophosphate-pentose pathway, it had no effect on glucose metabolism in the Embden-Meyerhof pathway or the tricarboxylic acid cycle. Since the hexosemonophosphate-pentose pathway is a source of ribose-5-phosphate, the precursor of phosphoribosyl pyrophosphate, the effect of pyrroline-5-carboxylate on the hexosemonophosphate-pentose pathway may link amino acid and nucleic acid metabolism.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041100306
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  • 4
    Electronic Resource
    Electronic Resource
    Regulation of glutamine synthetase and glutaminase activities in cultured skeletal muscle cells (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 120 (1984), S. 197-203 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Glutamine is synthesized in skeletal muscle, released to the circulation, and transported to other tissues, where it may provide important substrate for gluconeogenesis, ammoniagenesis, and energy-yielding pathways. With the ultimate goal of delineating the factors that control glutamine production and release by skeletal muscle, we have studied the regulation of two key enzymes, glutamine synthetase and glutaminase, in the L6 line of rat skeletal muscle cells grown in monolayer culture. The cultured myotubes were found to have glutamine synthetase and phosphate-dependent glutaminase activities. Glutamine synthetase activity was increased following incubation (1) in glutamine-free medium (threefold); (2) in medium containing high glutamic acid concentrations (fourfold); and (3) in medium supplemented with dexamethasone (threefold). In each case the increase in glutamine synthetase activity required several hours to reach a maximum and was prevented by cycloheximide, suggesting that the change occurred through increased enzyme biosynthesis. No substances tested were found to affect glutaminase activity. We conclude that glutamine synthetase in cultured skeletal muscle is responsive to substrate, product, and hormonal regulation.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041200213
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  • 5
    Electronic Resource
    Electronic Resource
    Quantitative ultrastructural analysis of receptor-mediated insulin uptake into adipocytes (1983)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 115 (1983), S. 199-207 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Monomeric ferritin-insulin was used as an ultrastructural marker to determine by quantitative electron microscopy the time course and route of insulin uptake in rat adipocytes. To approximate steady state membrane binding conditions prior to any internalization, adipocytes were prefixed with glutaraldehyde and incubated for 30 min with 70 nM monomeric ferritin-insulin. Electron micrographs of these cells showed that the ferritin-insulin particles were predominantly in small groups of receptor sites on the plasma membrane and in pinocytotic-like invaginations of the plasma membrane. Significant amounts of ferritin-insulin were observed in cytoplasmic vesicles of unfixed cells as early as 2 min and in multivesicular bodies and lysosome-like structures within 5 to 10 min after the addition of the ligand. Ferritin-insulin accumulation reached steady state levels in the cytoplasmic vesicles in 5 to 10 min and in the lysosome-like structures in 15 min. Little ferritin-insulin was bound to coated pits, and the relative paucity of coated pits found in adipocytes suggested that these specialized endocytotic structures have a relatively insignificant role in insulin uptake in fat cells. Quantitative analysis of the uptake process suggested that a proportion of the insulin internalized by the cell may not be transported to lysosomes, but may be recycled along with the insulin receptor to the plasma membrane.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041150215
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  • 6
    Electronic Resource
    Electronic Resource
    Mutant cell lines resistant to azetidine-2-carboxylic acid: Alterations in the synthesis of proline from glutamic acid (1984)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Cellular Physiology 119 (1984), S. 137-143 
    Details
    ISSN: 0021-9541
    Keywords: Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Medicine
    Notes: Two mutant Chinese hamster lung fibroblast lines have been isolated that are resistant to the the toxic proline analog L-azetidine-2-carboxylic acid. The line designated AZCA-1 has 30-fold elevated activity of pyrroline-5-carboxylate synthase and a large increase in the rate of proline production and release compared to controls. Pyrroline-5-carboxylate synthase activity is not elevated in the resistant line designated AZCA-4, but the enzyme is less sensitive to inhibition by ornithine and proline than control enzyme. Intracellular proline is elevated in AZCA-4 cells, with no change in the rate of release of proline synthesized from glutamate. Resistance to azetidine carboxylic acid in both mutant lines is attributed to the expanded intracellular proline pool that results from alterations in pyrroline-5-carboxylate synthase. These results indicate that intracellular proline levels are determined at least in part by the regulated activity of pyrroline-5-carboxylate synthase.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jcp.1041190122
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  • 7
    Electronic Resource
    Electronic Resource
    Micellar Solubilization of Biopolymers in Hydrocarbon Solvents III. Empirical Definition of an Acidity Scale in Reverse Micelles (1980)
    New York, NY : Wiley-Blackwell
    Helvetica Chimica Acta 63 (1980), S. 2302-2311 
    Details
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: This paper deals with the problem of defining, and measuring, the pH inside the water pool (which we define as pHwp) of reverse micelles, i.e. micelles formed by surfactants dissolved in apolar solvents in the presence of minimal amounts of water. The conceptual and experimental difficulties are discussed, and it is argued that no absolute determination of pHwp is possible, mostly because water in the water pools of reverse micelles is a new solvent, for which no standardization of acidity is available. The problem can be approached only on the basis of an empirical acidity scale.An empirical acidity scale for water pools in reverse micelles of bis (2-ethyl-hexyl) sodium sulfosuccinate (AOT) in isooctane has been defined by measuring the 31P-chemical shifts of phosphate buffers. The chemical shifts in bulk water were compared to those found in reverse micelles under the assumption that the pK of phosphate ion is the same in the two systems. It was found that in most cases there was little difference (less than 0.4 pH units) between pHwp and the pH of the starting buffer in bulk water (which we define as pHst). However, this difference between pHwp and pHst may become much larger in certain cases.The difference (pHwp-pHst) is measured under a variety of conditions, and this permits the determination of an operational acidity in the micelle water pools as a function of the pHst with which the aqueous micelles are prepared. The significance of such data for interpreting the behaviour of enzymes confined in the micelles water pool is discussed. Based on the pHwp scale, the apparent pKa of phenol-red and 4-nitrophenol were determined in reverse micelles containing different buffers and different water content. The pKa values obtained were rather sensitive to changes of both these factors, which was taken to signify that organic dies have only a very limited applicability to measure the acidity of the water pools of reverse micelles.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/hlca.19800630820
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  • 8
    Electronic Resource
    Electronic Resource
    New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers). III. Synthesis and characterization of poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1539-1546 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The synthesis of a new glassy-rubbery-glassy triblock copolymer poly(α-methylstyrene-b-isobutylene-b-α-methylstyrene) has been demonstrated. The key to the synthesis was the preparation by inifer method of a perfectly bifunctional polyisobutylene which carries tert-chlorine end groups Cl-PIB-Cl. In conjunction with Et2AlCl coinitiator, the telechelic Cl-PIB-Cl molecule initiates the polymerization of α-methylstyrene at both ends of the prepolymer. Triblock composition can be controlled by the judicious selection of synthesis conditions; that is, Cl-PIB-Cl molecular weight, α-methylstyrene concentration, and solvent polarity. Theoretical triblock Mn calculated from Mn of Cl-PIB-Cl and triblock overall composition is in excellent agreement with experimental Mn which indicates negligible homopolymer contamination. Extraction with a series of hydrocarbon solvents reveals broad composition distribution. The stress-strain profile of a triblock is similar to that of a poly(styrene-b-butadiene-b-styrene) thermoplastic elastomer of similar composition.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180510
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  • 9
    Electronic Resource
    Electronic Resource
    New telechelic polymers and sequential copolymers by polyfunctional initiator-transfer agents (inifers). II. Synthesis and characterization of α,ω-di(tert-chloro)polyisobutylenes (1980)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 18 (1980), S. 1523-1537 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Detailed understanding of the mechanism of initiation and chain transfer in BCl3-coinitiated isobutylene polymerization led to the efficient synthesis of symmetric telechelic polyisobutylenes carrying ∼CH2C(CH3)2Cl groups at either end of the molecule Cl-PIB-Cl. The synthesis is based on the use of inifers, i.e., bifunctional initiator-transfer agents that effect controlled initiation and propagation in the absence of chain transfer to a monomer. Specifically, the synthesis of Cl-PIB-Cl was achieved by the p-dicumyl chloride/BCl3/isobutylene/CH2Cl2 system. According to the inifer mechanism each Cl-PIB-Cl contains two terminal tertiary chlorines and one phenyl group at the interior of the chains. The structure of this new symmetric telechelic polymer has been established by detailed characterization studies including a sensitive new gel permeation chromatography (UV plus RI) analysis method, 1H-NMR, kinetic experiments, and chemical derivatization. The Cl-PIB-Cl molecule is a key intermediate for the synthesis of hosts of new materials, e.g., triblock copolymers, α,ω-diolefins, and α,ω-difunctional polymers.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1980.170180509
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  • 10
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    Measurement of a Quadrupole Transition Moment by Interference of Quadrupole and dc-Field-Induced Sum-Frequency Generation (1982)
    American Physical Society
    Details
    Publication Date: 1982-02-08
    Print ISSN: 0031-9007
    Electronic ISSN: 1079-7114
    Topics: Physics
    Published by American Physical Society
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