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  • 1
    ISSN: 0030-4921
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Chemical shifts for the aromatic tritons of toluene decrease in the order meta〉para〉ortho for pure toluene, but in the order meta〉ortho〉para for dilute solutions of toluene in carbon tetrachloride, chloroform, cyclohexane and dimethyl sulphoxide; m-xylene shifts are 5〉4,6〉2 in the pure state and 5〉2〉4,6 in carbon tetrachloride and dimethyl sulphoxide; o-xylene shifts are 4,5〉3,6 in the pure state and reversed in carbon tetrachloride.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The modification of epoxy resins by reactions involving their hydroxyl groups is described. For example, reactions with enol ethers, acrylonitrile, ethyl acetoacetate and certain other carboxylic esters, or triethyl orthoformate, gave products which had reduced reactivities towards various hardeners, and which therefore gave lower peak temperatures on cure and/or longer usable lives. Suitable modification of epoxy resins with various other reagents(certain acid anhydrides, epichlorohydrin, or N-hydroxymethylacrylamide) introduces additional useful functional groups. The uses of a diisocyanate and of α-naphthyl isocyanate to modify epoxy resins or their mixtures prior to GPC analysis are also mentioned.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 21 (1981), S. 325-330 
    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: The physical aging process in styrene-butadiene and carbonate-siloxane block copolymers has been studied by monitoring the time dependent changes in mechanical and thermal properties. Specifically, stress-strain, stress relaxation and differential scanning calorimetry experiments were utilized. For the styrene-butadiene systems, it was found that the rate of physical aging increases with decreasing glassy content between 50 and 100 percent glass. However, the rate must decrease to zero when the percent glass reaches zero. The occurrence of physical aging was also noted in the carbonatesiloxane block copolymer investigated. The data are discussed in light of the practical ramification of utilizing these block copolymers in material applications.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1573-0646
    Keywords: experimental chemotherapy ; ASTA Z 7557 ; cyclophosphamide ; AKR lymphoma ; autochthonous leukemias ; autochthonous mammary carcinomas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary The antineoplastic activities of ASTA Z 7557 and cyclophosphamide (CPA) were compared in advanced transplanted AKR lymphoma by determining the optimal dose using single dose and twofold applications. Autochthonous DMBA-induced leukemias and MNU-induced mammary carcinomas were treated with fractionated doses over 3 and 5 weeks, respectively. In the respective optimal dosages ASTA Z 7557 exhibited an antitumor effect comparable to that of CPA in all three models. The results obtained by treatment of the autochthonous models indicate that Z 7557 seems to have advantages over CPA in the treatment of malignancies with impaired bone marrow function as for instance acute leukemias and in fractionated dose schedules.
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  • 5
    ISSN: 1573-0646
    Keywords: oxazaphosphorines ; chemotherapeutic activity ; myelotoxicity ; DNA-damage
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Medicine
    Notes: Summary This study compares the two oxazaphosphorine compounds ASTA Z 7557 (AZ) and cyclophosphamide (CP) in their therapeutic activity as well as in their myelotoxicity and DNA damage being induced after a single intraperitoneal injection. Therapeutic activity was determined towards methylnitrosourea-induced rat mammary carcinomas in vivo and in vitro, resulting in comparable efficacy of both compounds at their optimal doses, respectively, with the sensitivity of individual tumors being reflected by the degree of inhibition of 3H-thymidine uptake of these cells in vitro. Myelotoxicity was measured as inhibition of pluripotent (CFU-S) and macrophage-granulocyte committed (CFU-C) stem cells together with the extent of single strand breaks and DNA-DNA interstrand crosslinks in murine bone marrow. At equimolar base AZ was found to induce a higher level of DNA damage than CP in the bone marrow of mice 16 hours after a single intraperitoneal injection. Both compounds depressed the pluripotent stem cell compartment of the bone marrow to a similar extent, whereas AZ was significantly less toxic to the granulocyte cell lineage.
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  • 6
    ISSN: 0091-7419
    Keywords: PDGF ; somatomedin ; SV40 ; cell cycle ; Life Sciences ; Molecular Cell Biology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: The platelet-derived growth factor (PDGF), which is found in serum but not in plasma, has been purified to homogeneity; it stimulates replication at a concentration of 10-10M. Brief treatment with PDGF causes densityinhibited Balb/c-3T3 cells to become competent to synthesize DNA; pituitary fibroblast growth factor (FGF) or precipitates of calcium phosphate also induce competence. Continuous treatment with plasma allows competent, but not incompetent, cells to synthesize DNA. A critical component of plasma is somatomedin, a group of hormones with insulin-like activity; multiplication-stimulating activity (MSA) or insulin replace plasma somatomedin in promoting DNA synthesis.We have studied the molecular correlates of competence and the role of SV40 gene A products in regulating DNA synthesis. Treatment of quiescent cells with pure PDGF or FGF causes the preferential synthesis of five cytoplasmic proteins (approximate molecular weight 29,000, 35,000, 45,000, 60,000, and 72,000 detected by SDS-PAGE under reducing conditions). Two of these competence-associated proteins (29,000 and 35,000 daltons) are found within 40 min of PDGF addition; they are not induced by plasma, insulin, or epidermal growth factor (EGF), PDGF, FGF, or calcium phosphate induce an ultrastructure change within the centriole of 3T3 cells; this ultrastructural modification of the centriole is detectable by immunofluorescence within 2 h of PDGF treatment. Plasma, EGF, or MSA do not modify the centriole. SV40 induces replicative DNA synthesis in growth-arrested 3T3 cells but does not cause this alteration in centriole structure.Gene A variants of SV40, including a mutant with temperature-sensitive (ts) T-antigen (ts A209), a deletion in t-antigen (dl 884), and several ts A209 strains containing t-antigen deletions were used to induce DNA synthesis in Balb/c-3T3 cells. Like wild type SV40, all strains induced DNA synthesis equally well under permissive or nonpermissive conditions. Addition of PDGF or plasma had little effect on SV40-induced DNA synthesis. Thus, the viral function that induces replicative DNA synthesis in Balb/c-3T3 cells is not t and is not temperature sensitive. This SV40 gene function overrides the cellular requirement for hormonal growth factors. It does not induce transient centriole deciliation, a hormonally regulated event.
    Additional Material: 7 Ill.
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  • 7
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The thermal reaction of hydrogen-butene-2-cis mixtures has been studied in a static system at low extent of reaction around 500°C. Hydrogen does not affect the thermal reaction itself of the olefin, but gives rise to new stoichiometries of hydrogenolysis and hydrogenation, which are specified: \documentclass{article}\pagestyle{empty}\begin{document}$$ \begin{array}{l} {\rm H}_2 + cis - 2 - {\rm C}_4 {\rm H}_8 = {\rm CH}_4 + {\rm C}_3 {\rm H}_6 \\ {\rm H}_2 + cis - 2 - {\rm C}_4 {\rm H}_8 = {\rm H}_2 + 1 - {\rm C}_4 {\rm H}_8 \\{\rm H}_2 + cis - 2 - {\rm C}_4 {\rm H}_8 = n - {\rm C}_4 {\rm H}_{10} \\ \end{array} $$\end{document} The reaction is described in terms of a molecular and free-radical mechanism. It is shown that the key process for the hydrogenolysis-hydrogenation reaction is and that the rate constant of this process can be determined from either propylene, or methane, or butene-1 formations: \documentclass{article}\pagestyle{empty}\begin{document}$$ {\rm k}_{{\rm 7'}} \simeq {\rm 10}^{{\rm 13}{\rm .1 - 24}{\rm .2/}\theta } \,{\rm cm}^{\rm 3} {\rm /mol} \cdot {\rm s} $$\end{document} with θ = 4.57 × 10-3 T kcal/mol. Other rate constants are estimated and agree with literature data.
    Additional Material: 12 Ill.
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  • 8
    ISSN: 0538-8066
    Keywords: Chemistry ; Physical Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: H2S increases the thermal isomerization of butene-2 cis (Bc) to butene-1 (B1) and butene-2 trans (Bt) around 500°C. This effect is interpreted on the basis of a free radical mechanism in which buten-2-yl and thiyl free radicals are the main chain carriers. B1 formation is essentially explainedby the metathetical steps: whereas the free radical part of Bt formation results from the addition-elimination processes:. It is shown that the initiation step of pure Bc thermal reaction is essentially unimolecular: and that a new initiation step occurs in the presence of H2S:. The rate constant ratio has been evaluated: \documentclass{article}\pagestyle{empty}\begin{document}$$ \frac{{k_2 }}{{k_3 }} \simeq 0.4\exp ^{ - (6500 \pm 1000)/RT} (RT\,in\,cal/mol) $$\end{document} and the best values of k1 and k1', consistent with this work and with thermochemical data, are \documentclass{article}\pagestyle{empty}\begin{document}$$ k_1 \simeq 10^{15.5 - 85,500/2.3RT} \sec ^{ - 1} $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k_{1^\prime } \simeq 10^{13.6 - 53,700/2.3RT} {\rm cm}^3 /{\rm mol}\,{\rm sec} $$\end{document}. From thermochemical data of the literature and an “intrinsic value” of E-3 ⋍ 2 kcal/mol given by Benson, further values of rate constants may be proposed: \documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 \simeq 10^{14 - 9,300/2.3RT} cm^3 /mol\sec $$\end{document} \documentclass{article}\pagestyle{empty}\begin{document}$$ k_3 \simeq 10^{13.6 - 15,800/2.3RT} cm^3 /mol\sec $$\end{document} is shown to be E4 ⋍ 3.5 ± 2 kcal/mol, of the same order as the activation energy of the corresponding metathetical step.
    Additional Material: 8 Ill.
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  • 9
    ISSN: 1520-510X
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
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  • 10
    ISSN: 1432-0800
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Medicine
    Type of Medium: Electronic Resource
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