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  • 1
    Electronic Resource
    Electronic Resource
    The electrical conductivity of cellulose HYPHAN® and its complexes (1993)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 212 (1993), S. 13-18 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die elektrische Leitfähigkeit (σ) von Cellulose-HYPHAN® und seinen Komplexen mit Cr3+, Mn2+, Mo5+ und Hg2+ wurde im Temperaturbereich 25-510°C bestimmt. Die Aktivierungsenergie wurde aus der Abhängigkeit von log σ von der reziproken Temperatur berechnet. Die Ergebnisse zeigen, daß die Leitfähigkeit mit steigender Temperatur zunimmt und dabei zwei Maxima durchläuft. Das erste Maximum läßt sich dem Wassergehalt zuordnen, während das zweite mit dem thermischen Abbau der Cellulose-Kette zusammenhängt. Die Werte der Aktivierungsenergie lassen darauf schlieäen, daß sich beim Erhitzen die Halbleitereigenschaften der Komplexe verbessern.
    Notes: The electrical conductivity, σ, of cellulose HYPHAN® and its complexes with Cr3+, Mn2+, Mo5+ or Hg2+ was measured from room temperature to 510°C. The activation energy, ΔE, of the samples was calculated from log σ against 1/T curves. The results show that the electrical conductivity increases by temperature with two maximum peaks. The first peak is attributed to the moisture content, while the second one is attributed to the thermal degradation of the cellulose chain. The values of the activation energy indicate that the samples change from low semiconductor to high semiconductor property with heating.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1993.052120102
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  • 2
    Electronic Resource
    Electronic Resource
    Modifications of the amide bond and conformational constraints in pseudopeptide analogues (1993)
    New York : Wiley-Blackwell
    Biopolymers 33 (1993), S. 1135-1148 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We have investigated the conformational effects of modifying the amide group in model dipeptides. The N-methyl amide ψ[CO-NMe], N-hydroxy amide ψ[CO-N(OH)], N-amino amide ψ[ CO-N (NH2)], retro amide ψ[ NH-CO], reduced amide in the neutral ψ[CH2-NH] and protonated ψ[CH2-N + H2] state, and hydrazide ψ[CO-NH-NH] have been introduced as surrogates of the amide link in pseudopeptide derivatives of the Pro-Gly or Ala-Gly model dipeptides protected on both termini by an amide group. These compounds have been studied in solution by proton nmr and ir spectroscopy, and in the solid state by x-ray diffraction, giving an extended data set of experimental structural and conformational information on pseudopeptide sequences. The conformational effects depend both on the nature and the position of the modified amide link. Some modifications appear to have no intrinsic conformational induction (N-amino and retro amide), but destabilize any local folded structure by hydrogen-bond breaking. Because of the formation of strong intramolecular interactions, others are capable of stabilizing a β-turn (for example protonated reduced amide), or of inducing a particular local conformation such as a β- or γ-like turn (for example N-hydroxy amide). The particular geometry of the cis N-methyl amide and of the “hydrazino” proline favors the formation of a sharp turn of the main chain. All these structural data are of interest to the design of bioactive peptide mimics. © 1993 John Wiley & Sons, Inc.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bip.360330715
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  • 3
    Electronic Resource
    Electronic Resource
    Fullerene-linked particles as LC chromatographic media and modification of their electron donor/acceptor properties by secondary chemical reactions (1993)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 5 (1993), S. 223-235 
    Details
    ISSN: 1040-7685
    Keywords: fullerene-linked polymer ; fullerene-linked silica ; synthesis ; stationary phases ; microcolumns ; polycyclic aromatics ; polychlorinated biphenyls ; environmental contaminants ; liquid chromatography ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Fullerenes (C60 and C70) linked to small silica or polymer particles provide novel chromatographic stationary phases with electron donor/acceptor surface interactions that may parallel those of aromatic carbons. Separations of fullerenes and aromatic compounds frequently encountered as environmental contaminants were investigated using LC microcolumns containing either particles prepared from BrHC60 linked to amino-silica (Spherisorb-NH2, Phenomenex) or porous polymers containing ca. 12% fullerene by weight. The polystyrene divinylbenzene (PSDVB)-C60/70H column had greater capacity (k') than the Si—NH—C60/70H column. Toluene and polycyclic aromatic hydrocarbons (PAHs), naphthalene, anthracene, pyrene, and perylene, were retained in the order of increasing ring number; nitro-substituents increased retention; and chlorinated-dibenzo-p-dioxins and -dibenzofurans were more strongly retained than their parent compounds. PCB congeners with no chlorine in the ortho, ortho'-positions are co-planar and are strongly retained; for these isomers, retention increased with higher chlorination. We demonstrate that surface-linked fullerenes can also accommodate further chemical modification through the addition of 2-(4-nitrophenyl)ethyl or -NH—CH2CH2NH2 moieties to yield altered electron donor/acceptor affinity. Separations appear to be derived primarily from aromatic electron induced dipole-dipole or electron-pair donor or acceptor interactions (charge transfer complexes). Except for the fullerenes, surface interactions with compounds are largely suppressed with methylene chloride as the mobile phase.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/mcs.1220050307
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  • 4
    Electronic Resource
    Electronic Resource
    Study of the effect of fumed silica on rigid PVC properties (1993)
    Brookfield, Conn. : Wiley-Blackwell
    Journal of Vinyl and Additive Technology 15 (1993), S. 17-21 
    Details
    ISSN: 0193-7197
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: This study seeks to substitute fumed silica for chlorinated polyethylene (CPE) within a rigid PVC formulation intended for profile extrusion such as doors and window frames. The effect of fumed silica on both mechanical (tensile and impact) and thermal (Vicat point, HDT, and linear thermal expansion coefficient) properties were investigated. Five rigid PVC formulations were prepared, including a reference one (F1), then F1 with CPE, F1 with untreated silica, F1 with heat treated silica, and finally F1 with dried silica and a coupling agent. The effect of CPE on mechanical properties was very modest. On the other hand, CPE showed its inefficiency, in that HDT and Vicat point were decreased. Heat treated silica showed the greatest improvement in both mechanical and thermal properties. Untreated silica showed a small effect on both properties. Finally, the incorporation of coupling agent gave considerable improvement in both mechanical and thermal properties.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/vnl.730150106
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  • 5
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    Mutation and protein expression of p53 in acquired immunodeficiency syndrome-related lymphomas (1993)
    American Society of Hematology
    Details
    Publication Date: 1993-08-01
    Description: p53 mutations are found in a variety of neoplasia. B-immunoblastic lymphoma (BIBL) is a rapidly progressive, aggressive lymphoma. As patients with acquired immunodeficiency syndrome (AIDS) live longer, BIBL is becoming an increasing problem. We asked three questions in our study. What is the frequency of p53 mutations in BIBL? Is it more frequent in patients with AIDS? Can immunohistochemical staining of lymph nodes for expression of p53 substitute for mutational analysis of p53 to detect lymphomas with mutated p53? Exons 5, 6, 7, 8 of the p53 gene (hot-spots for mutations) were amplified and examined for mutations by single-strand conformation polymorphism (SSCP) analysis. Altered migration was observed in 7 of 52 BIBL samples. Of these, 4 of 25 were from individuals infected with human immunodeficiency virus (HIV) and 3 of 27 were not infected with HIV. Direct sequencing of amplified material confirmed the presence of mutations in exons 5, 7, 8 of p53. A total of 26 BIBL as well as other lymphoma/leukemia samples, stained strongly by immunohistochemistry with three antibodies directed against human p53. Five of 6 BIBL samples with p53 mutations stained strongly for p53, but 20 lymphoma samples with no detectable p53 mutations also stained strongly for p53. Of note, however, 10 hyperplastic, nonmalignant lymph nodes from individuals either infected or not infected with HIV had negligible staining for p53 protein. In conclusion, p53 mutations occur in about 14% BIBL samples; the frequency of p53 mutations in BIBL in individuals with and without AIDS was similar. Positive p53 immunohistochemistry did not correlate with detectable p53 mutations in the same tissue, but positive immunohistochemical staining for p53 was only found in neoplastic lymph nodes. This latter finding provides a strong warning that p53 immunochemistry with available reagents cannot be used to determine which tumors have mutations of p53.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology
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  • 6
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    Mutation and protein expression of p53 in acquired immunodeficiency syndrome-related lymphomas (1993)
    American Society of Hematology
    Details
    Publication Date: 1993-08-01
    Description: p53 mutations are found in a variety of neoplasia. B-immunoblastic lymphoma (BIBL) is a rapidly progressive, aggressive lymphoma. As patients with acquired immunodeficiency syndrome (AIDS) live longer, BIBL is becoming an increasing problem. We asked three questions in our study. What is the frequency of p53 mutations in BIBL? Is it more frequent in patients with AIDS? Can immunohistochemical staining of lymph nodes for expression of p53 substitute for mutational analysis of p53 to detect lymphomas with mutated p53? Exons 5, 6, 7, 8 of the p53 gene (hot-spots for mutations) were amplified and examined for mutations by single-strand conformation polymorphism (SSCP) analysis. Altered migration was observed in 7 of 52 BIBL samples. Of these, 4 of 25 were from individuals infected with human immunodeficiency virus (HIV) and 3 of 27 were not infected with HIV. Direct sequencing of amplified material confirmed the presence of mutations in exons 5, 7, 8 of p53. A total of 26 BIBL as well as other lymphoma/leukemia samples, stained strongly by immunohistochemistry with three antibodies directed against human p53. Five of 6 BIBL samples with p53 mutations stained strongly for p53, but 20 lymphoma samples with no detectable p53 mutations also stained strongly for p53. Of note, however, 10 hyperplastic, nonmalignant lymph nodes from individuals either infected or not infected with HIV had negligible staining for p53 protein. In conclusion, p53 mutations occur in about 14% BIBL samples; the frequency of p53 mutations in BIBL in individuals with and without AIDS was similar. Positive p53 immunohistochemistry did not correlate with detectable p53 mutations in the same tissue, but positive immunohistochemical staining for p53 was only found in neoplastic lymph nodes. This latter finding provides a strong warning that p53 immunochemistry with available reagents cannot be used to determine which tumors have mutations of p53.
    Print ISSN: 0006-4971
    Electronic ISSN: 1528-0020
    Topics: Biology , Medicine
    Published by American Society of Hematology
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