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  • 11
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 24 (1986), S. 239-249 
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Previous investigations have given evidence of the existence of specific chemical interactions between poly(bisphenol-A carbonate) (PC) and a number of linear aliphatic polyesters, with the consequent formation of compatible polymer alloys. Here we address the particular kind of specific interaction that takes place in these systems by performing a quantum-mechanical study of the apparently most reasonable types of molecular interactions occurring in model compounds of the above polymers. Complete neglect of diffential overlap, (CNDO), in its CNDMEX version, and perturbative configuration using localized orbitals (PCILO) were the calculation schemes used on diphenyl carbonate (DPC) and dimethyl succinate (DMS), selected as models. It was found that, on a one-to-one basis, the DPC-DMS system is energetically more stable than the individual separate molecules; on examination of the possible interaction sites for the two chemical species, the interaction between the ester group oxygen in one DMS molecule with one of the phenyl rings in DPC appears to be the most favorable type of molecular interrelation, even though hydrogen bond formation is also possible between the oxygen atoms in DPC and the methylene hydrogens in DMS. (The former interaction decreases the total energy of the system by 0.12 kcal/mol, more than the latter.)
    Additional Material: 7 Ill.
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  • 12
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    Journal für Praktische Chemie/Chemiker-Zeitung 324 (1982), S. 735-742 
    ISSN: 0021-8383
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Komplexe der Dipicolinsäure und verwandter Verbindungen zur Oxidation organischer SubstrateDie Oxidation von methylierten Hydrochinonen zu Chinonen und von α,β-ungesättigten Alkoholen zu Aldehyden in Gegenwart verschiedener Oxidationsmittel wurde untersucht.Günstige Ergebnisse wurden bei der Anwendung des MnO2-Dipikolinsäure-Systems für d'e Oxidation von Allyl- und Benzylalkoholen und des AgO-Dipikolinsäure-Systems für die oxidative Demethylierung von methylierten Hydrochinonen erreicht.Der Einfluß der Struktur von 4-substituierten Dipicolinsäuren auf die katalytischen Eigenschaften wurde untersucht.
    Additional Material: 5 Tab.
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  • 13
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 26 (1992), S. 1039-1051 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Because periprosthetic infection remains a vexing problem for patients receiving implanted devices, we evaluated the effect of several materials on neutrophil free radical production. Human peripheral blood neutrophils were incubated with several sterile, lipopolysaccharide (LPS)- free biomaterials used in surgically implantable prosthetic devices: polyurethane, woven dacron, and Velcro. Free radical formation as the superoxide (O2-) anion was evaluated by cytochrome c reduction in neutrophils that were exposed to the materials and then removed and in neutrophils allowed to remain in association with the materials. Neutrophils exposed to polyurethane or woven dacron for 30 or 60 min and then removed consistently exhibited an enhanced release of O2- after simulation via receptor engagement with formyl methionyl-leucyl- phenylalanine. Enhanced reactivity to stimulation via protein kinase C with phorbol myristate acetate, however, was not consistently observed. The cells evalu- ated for O2- release during continuous association with the biomaterials showed enhanced metabolic activity during short periods of association (especially with polyurethane and woven dacron). Although O2- release by neutrophils in association with these materials decreased with longer periods of incubation, it was not obliterated. These studies, therefore, show that several commonly used biomaterials activate neutrophils soon after exposure and that this activated state diminishes with prolonged exposure but nevertheless remains measurable. The diminishing level of activity with prolonged exposure, however, suggests that ultimately a depletion of reactivity may occur and may result in increased susceptibility to periprosthetic infection.
    Additional Material: 1 Ill.
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  • 14
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 28 (1994), S. 189-194 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: The coefficient of thermal expansion of core and veneer porcelains for all ceramic crowns must be compatible to prevent formation of stresses during the firing cycles. The purpose of this study was to use a thermal shock test to evaluate the crazing resistance of six all-ceramic crown systems. The systems tested were: Vita In-Ceream®, Vita Hi-Ceram®, Dicor™ veneered with Vitadur® N, magnesia core veneered with Ceramco® II, magnesia core veneered with Silhouette™, and magnesia core veneered with Vita VMK® 68. A maxillary central incisor was prepared with 1.0 mm axial and 1.5 mm incisal reduction. Refractory dies were prepared and crowns were fabricated using the manufactures recommendations. Six specimens of each system were placed inside a beaker in a furnace at 90°C. After 15 min heat soak, ice water was poured into the beaker through a funnel. The samples were dried in air, reheated, and inspected for crazing using light microscopy. If crazing was observed, this would constitute a failure at a temperature difference (ΔT) of 90°C. If no failure occurred, the test was repeated at increasing temperature increments of 10°C until failure. The crazing resistance of each system, expressed as the mean ΔT, was: 〉 200 (Hi-Ceram®), 152 ± 19 (Dicor™ / Vitadur® N), 143 ± 5 (magnesia core/Vita VMK® 68), 122 ± 21 (magnesia core/Silhouette™), and 118 ± 10 (magnesia core/Ceramco® II) °C. All systems tested resisted crazing due to quenching in ice cold water from 100°C. Systems with lower coefficients of expansion showed significantly greater resistance to thermal shock using ANOVA. © 1994 John Wiley & Sons, Inc.
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  • 15
    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: Eine Reihe synthetischer Polyglukose-carboxylderivate mit verschiedenem Carboxylgehalt wurde zur Hemmung der Ribonuklease-entpolymerisierenden Wirkung an Ribonukleinsäure, die nach der KUNITZ-Probe gemessen wurde, verwandt. Die enzymhemmende Wirkung nahm mit der Ladungsdichte der Polyglukose-carboxylderivate stark zu.Durch diese und ähnliche Experimente ergibt sich, daß COULOMB-Anziehungskräfte beim Zusammenführen von Enzym und Substrat eine wichtige Rolle spielen.
    Notes: A series of synthetic polyglucose carboxyl derivatives with different carboxyl content has been used to inhibit ribonuclease depolymerizing activity on ribonucleic acid as measured by the KUNITZ assay. The enzyme inhibitory activity increased greatly with the charge density of the polyglucose carboxyl derivatives.From this and similar experiments it is concluded, that COULOMBIC attracting forces have an important role in bringing the enzyme and the substrate together.
    Additional Material: 4 Ill.
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  • 16
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A low-molecular-weight disulfide derivative of the antileukemic agent 6-purinethiol (2) was used for coupling with a macromolecular carrier, poly(1-vinyl-2-pyrrolidone-co-maleic acid) via spacer groups. The in vitro hydrolytic stabilities of the polymeric prodrugs were examined at pH 7,2 and 8,8. An enhanced cleavage of the disulfide bridge yielding 6-purinethiol was observed. Enzymatic hydrolysis of the prodrug containing an enzyme-sensitive spacer was also done in the presence of elastase.
    Additional Material: 2 Ill.
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  • 17
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 3-Chloro-2-hydroxypropyl ether of dextran (3a) and succinyldextran (4a) were prepared and used for coupling the anticancer agents 6-purinethiol and 5-fluorouracil. The “in vitro” drug liberation was measured at pH 7,2 and 8,8. The release rate from the dextran conjugates was compared with that of the poly(1-vinyl-2-pyrrolidone-co-maleic acid) derivatives of these drugs. The effect of the macromolecular chain on the hydrolytic behaviour of the polymer-bound drugs was clearly detected.
    Additional Material: 2 Ill.
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  • 18
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 377-385 
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The design of a sliding controller for a continuous fermentation process is presented. The results obtained by simulation have proved the control scheme to be very robust. Regulation of substrate concentration at its optimal value has been achieved even though process parameters change their nominal values. Chattering effects are decreased by introducing a minor modification of the control variable around the sliding surface.
    Additional Material: 14 Ill.
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  • 19
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 65 (1997), S. 767-785 
    ISSN: 0020-7608
    Keywords: Chemistry ; Theoretical, Physical and Computational Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Molecular orbital calculations were carried out for the dimerization step in the polymerization process of vinyl acetate and styrene through free radicals and ionic mechanisms. The calculations were performed for monomers, dimers, their positive and negative ions, and free radicals. The minimum-energy geometry is achieved in all cases, the geometrical and electronic parameters are analyzed, a dimerization reaction pathway is proposed, and the heats of polymerization obtained are in excellent agreement with experimental data.   © 1997 John Wiley & Sons, Inc. Int J Quant Chem 65: 767-785, 1997
    Additional Material: 12 Ill.
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  • 20
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 40 (1998), S. 171-179 
    ISSN: 0021-9304
    Keywords: hydroxyapatite ; titanium ; calvarial cells ; cell-specific alkaline phosphatase activity ; bone-related proteins gene expression ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Rat calvarial cell mitogenic behavior was investigated on various biomaterials coated with Matrigel®, a basement membrane matrix containing growth factors. Low (20-40%) and high (70-90%) crystallinity hydroxyapatite (rHA and cHA), rough titanium (Ti), and tissue culture polystyrene (TP) surfaces were compared. Surface chemistry and calcium resorption of HA coatings, alkaline phosphatase activity (APA), and growth of cells were measured for Matrigel®-coated and uncoated surfaces at 2, 7, and 14 days. Gene expression for four noncollagenous bone-related proteins (osteonectin, osteopontin, alkaline phosphatase, and osteocalcin) was also investigated by reverse transcription and polymerase chain reaction up to 28 days. Ca concentration in incubating solutions increased with time for the two types of HA coatings and was always greater for rHA than cHA. Surface chemistry and coating dissolution rates were not affected by the presence of Matrigel® or cells throughout the study. APA of cells on the two HA-coated surfaces was comparably enhanced in the presence of Matrigel® and was greater than on Ti surfaces. Only HA surfaces showed an increased APA of cells with time in the presence of Matrigel®. Cell growth peaked at 7 days and was greatest for cells on the two HA surfaces and without Matrigel®. At 14 days, cell growth was comparable on the four surfaces. The presence of HA and Matrigel® enhanced cell-specific APA at 14 days. Gene expression for all four proteins investigated showed no differences between surfaces after 7 days. At 2 and 7 days, gene expression was indicative of proliferation for Ti, and of proliferation, differentiation, and mineralization for HA and TP more so without Matrigel®. The addition of this matrix significantly enhanced mitogenicity of calvarial cells on HA only after 14 days. Matrigel® eliminated differences seen between the two HA coatings. Gene expression was not enhanced or inhibited by the presence of Matrigel®. © 1998 John Wiley & Sons, Inc. J Biomed Mater Res, 40, 171-179, 1998.
    Additional Material: 6 Ill.
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