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  • 11
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The short-period polymerization method was successfully applied to the synthesis of a novel diblock copolymer, polypropene-block-poly(ethylene-co-propene). The polymerization was carried out for ca. 0,1 s with a MgCl2-supported Ziegler catalyst. The copolymers obtained showed unimodal curves in gel-permeation chromatography without any peak in the low-molecular-weight region. After extraction with heptane, the fraction of poly(ethylene-co-propene) remained unchanged in the copolymer but disappeared in a commercial so-called block-type copolymer. All the results the formation of polypropene-block-poly(ethylene-co-propene), in which poly(ethylene-co-propene) is chemically linked with polypropene.
    Additional Material: 4 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Rapid Communications 17 (1996), S. 25-29 
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A modified-polypropene-supported Ziegler catalyst was prepared using polypropene containing a small amount of poly(7-methyl-1,6-octadiene) as a starting polymer for bromination, lithiation, and reaction with TiCl4. The polymerization of ethene was carried out using the catalyst with Al(C2H5)3 in toluene at 60°C up to 100 h. The polymer yield increased linearly with polymerization time, which indicates that the active sites of the modified-polypropene-supported Ziegler catalyst are practically stable without deactivation even for 100 h and are able to propagate further polymerization of ethene.
    Additional Material: 2 Ill.
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  • 13
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 393-399 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The molecular weight and molecular weight distribution of polyethene prepared with a modified-polypropene-supported Ziegler catalyst were investigated in terms of the variation of the polymerization conditions, such as the kind of co-catalyst, its concentration, and polymerization temperature. Ethene polymerization with the catalyst in the presence of triethylaluminium proceeded in heterogeneous system to give a polyethene with extremely broad molecular weight distribution. The result was completely changed upon replacing the triethylaluminium by other alkylaluminium compounds, such as diethylaluminium chloride. Polyethenes with very broad, narrow, bimodal, and multimodal molecular weight distributions were obtained by simply varying the co-catalyst. The molecular weight distributions of polyethenes obtained were also very sensitive to co-catalyst concentration and polymerization temperature. From the results obtained, it is suggested that the modified-polypropene-supported Ziegler catalyst is feasible as a novel candidate for a catalyst system giving polyethenes with controlled molecular weight distributions in a wide range of molecular weight.
    Additional Material: 10 Ill.
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  • 14
    ISSN: 0730-2312
    Keywords: chemoprevention ; tongue ; liver ; large bowel ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: A number of naturally occurring compounds and several related synthetic agents were confirmed to exert chemopreventive properties against carcinogenesis in the digestive organs. Phenolic compounds, widely distributed as plant constituents, possess chemopreventive activities in tongue, liver, and large bowel of rodents. Of them, a simple phenolic protocatechuic acid seems to be a promising compound. Organosulfur compounds contained in the cruciferous vegetables and known to activate detoxifying enzymes are regarded as a candidate group for cancer preventive agents. We proved a strong protective effect of S-methylmethanethiosulfonate, a constituent in these vegetables, on azoxymethane (AOM)-induced large bowel carcinogenesis. Some oxygenated carotenoids (xanthophylls) are reported to have antitumor effects. Naturally occurring xanthophylls astaxanthin and canthaxanthin have considerable preventive activities on 4-nitroquinoline-1-oxide (4-NQO)-induced tongue carcinogenesis and AOM-induced large bowel carcinogenesis. A novel synthesized retinoidal butenolide, KYN-54, which suppresses large bowel as well as tongue carcinogenesis, could be a useful agent for prevention of digestive organ cancers. Some trace elements are known to have anticarcinogenic effects. Magnesium hydroxide, a protective agent in colorectal carcinogenesis, inhibits c-myc expression and ornithine decarboxylase activity in the mucosal epithelium of the intestine. Our results show that many agents with preventive effects in tongue, liver, and large bowel control carcinogen-induced hyperproliferation of cells in these organs. Carcinogens used to induce large bowel cancers also induce apoptosis in the target sites. Telomerase activity is increased in the tissues of preneoplastic as well as neoplastic lesions in experimental models such as dimethylbenz[a]anthracene-induced oral carcinogenesis in hamsters. These could be useful biomarkers in studies for cancer chemoprevention. J. Cell. Biochem. Suppl. 27:35-41. Published 1998 Wiley-Liss, Inc.
    Additional Material: 3 Ill.
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  • 15
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 199 (1998), S. 1765-1770 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A novel EPDM (ethene-propene-diene monomer)-supported homogeneous Ziegler catalyst was developed for the production of polyethene with narrow molecular weight distribution. Ethene polymerization was investigated in terms of the stability of the active sites on the catalyst and of the variation of the molecular weight distribution arising from a change in co-catalyst. The activity of the catalyst remained constant without deactivation at 60°C for 25 h, regardless of the kind of co-catalyst and the polyolefin support. The molecular weight distribution of polyethene was found to be affected by the co-catalyst. High molecular weight polyethene with M̄w/M̄n = 2.2, was obtained with triethylaluminium as a co-catalyst at appropriate conditions. The extraction experiment of the resulting polymer was performed to elucidate whether the chain growth occurs via ethene insertion into (1) a Ti-carbon bond formed by alkylation of the titanium species during the activation reaction with the co-catalyst, or (2) a bond between the Ti species and the polymer support produced during the catalyst preparation. Route 1 was confirmed by fractionation.
    Additional Material: 6 Ill.
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  • 16
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Both cyclic and acyclic sulfinate esters were labeled with 18O at the sulfinyl oxygen by acid-catalyzed isotope exchange with H218O or alkaline hydrolysis in H218O followed by re-esterification. Long-range 18O isotope effects on the 13C NMR chemical shifts were observed.
    Additional Material: 1 Ill.
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  • 17
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Molecular Reproduction and Development 37 (1994), S. 293-298 
    ISSN: 1040-452X
    Keywords: Sperm antigen ; Acrosome reaction ; Zona solution ; Ionophore A23187 ; Life and Medical Sciences ; Cell & Developmental Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology
    Notes: We have previously prepared an anti-mouse sperm monoclonal antibody (A-1) which inhibited sperm penetration into the egg zona pellucida. By indirect immunofluorescence (IIF), the A-1 antibody was shown to recognize an antigen localized in the acrosomal area of sperm. This antibody bound negligibly to fresh sperm, while binding to methanol-fixed sperm was almost complete. After methanol fixation, no sperm that penetrated into the zona were immunoreactive for this antibody. In the present study we examined the localization and fate of A-1 antigen during the acrosome reaction by IIF and flow cytometry (FCM). Cauda epididymal sperm were treated with either calcium ionophore A23187 or zona solution, immunostained indirectly, and subjected to FCM. Treatment with A23187 reduced the percentage of immunoreactive sperm to 59% from the 80% obtained in the untreated sperm. The treatment also reduced the average fluorescence intensity per fluorescence-positive spermatocyte to 65 channels, while this intensity was 89 channels in the untreated sperm. A similar result was obtained from treatment with zona solution. The proportion of sperm that was immunoreactive with A-1 antibody was reduced to 55% by incubation in zona-containing media from the 80% obtained in zona-free media. On the other hand, neither A23187 nor the zona solution affected the immunoreactivity or the fluorescence intensity of caput epididymal sperm, while the A-1 antigen was present in both the immature sperm from the caput epididymis of adult mice and in the mature sperm from the cauda epididymis of the same mice. These findings suggest that the intramembrane antigen recognized by the A-1 monoclonal antibody is released from sperm as a result of the acrosome reaction. © 1994 Wiley-Liss, Inc.
    Additional Material: 6 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Rapid Communications in Mass Spectrometry 9 (1995), S. 877-882 
    ISSN: 0951-4198
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The application of aqueous matrices to fast-atom bombardment mass spectrometry enables the detection of several organogermanium compounds as specific complexes with matrices. In the positive-ion mode, the organogermanium compounds showed a dominant ion [M+matrix-3 · H2O+H]+ whose dehydration involved atoms attached to the germanium atom. On the other hand, two types of fragmentation were observed in the negative-ion mode The first was a group of compounds, with a carboxy group, that formed a lactone ring and showed a dominant ion at [M+matrix -3 · H2O-H]-. The other group, without carboxy, attached another matrix molecule and showed a dominant fragment ion at [M+2 · matrix-3 · H2O-H]-. The investigation of these complex structures was performed using various matrices and D2O treatment.
    Additional Material: 5 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 26 (1986), S. 1116-1122 
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Radiation-induced reactions of polystyrene derivatives have been studied by the radiolysis of ring-substituted isopropylbenzene derivatives, i. e., 4-amino. 4-hydroxy, 4-methoxy, 4-methyl, 4-chloromethyl, 4-chloro, and 4-acetyl derivatives. Low-temperature ESR analyses measured at 77 K indicate that. In general, the a-position is the most sensitive site to radiation and that thus a-radicals are produced through a-hydrogen removal. However, among these derivatives, the amino, acetyl, chloromethyl, and. chloro derivatives undergo different reactions from the other derivatives. A phCO—CH3 cleavage from the- acetyl derivative and N—H cleavage from the amino derivative occur, and chlorine removal takes place from the chloro-methyl and chloro derivatives. Final products detected by gas chromatography-mass spectrometry indicate not only that radiation-induced free radical recombination occurs. but also that if chlorine is produced by radiation, hydrogen abstraction by radiation-induced chlorine takes place prior to the free radical recombination. The susceptibility of each derivative to hydrogen abstraction by radiation-induced active chlorine increases, as the electron-donation of ring-substituents is increased. Based on the clarified reaction mechanism, the design of polystyrene derivatives as resist materials is discussed and two new types of resist systems are described. One is a new chloromethylstyrene based blend resist, which is formulated from poly(4-meth-oxystyrene) and poly(4-chloromethylstyrene). The other is a new non-swelling alkaline developable negative resist, which is formulated from poly(4-hydroxystyrene) and a chlorine-releasing compound.
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  • 20
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 6 (1962), S. 629-638 
    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 radiation chemical process in polyvinyl chloride has been studied by means of electron spin resonance, optical spectroscopy, and measurement of gas evolution. The chief technique was to irradiate samples at -196°C. and then follow the change or changes with rising temperature. Resonance results showed that, on irradiation, several primary radicals, such as —CH2—ĊH—CH2—, —CHCl—ĊH—CHCl—, etc., were produced. Among them some —CH2—ĊH—CH2— radicals could recombine to form crosslinks during irradiation even at -196°C. A mechanism for the discoloration of PVC, based upon results obtained by these three different methods, has been postulated. Discoloration is caused by the formation of polyenyl radicals or polyene molecules of considerable conjugation lengths, some as long as 9 conjugated double bonds. Polyenyl radicals are produced as a result of a thermally induced secondary reaction of the —CHCl—ĊH—CHCl— radical, above -70°C., thereby accompanied by hydrogen chloride detachment following the so-called “zipper” mechanism. An equation relating the pressure of evolved HCl to the reaction temperature has been derived by a simple kinetic treatment of the zipper reaction. Some effect of heat treatment and increasing dose on discoloration was discussed.
    Additional Material: 16 Ill.
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