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  • 1
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 43 (1994), S. 673-677 
    ISSN: 0006-3592
    Keywords: islet transplantation ; bioartificial pancreas ; immunoisolation ; extravascular devices ; macroencapsulation ; microencapsulation ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Donor scarcity precludes the use of pancreatic transplantation to treat type I diabetes. Xenogeneic islet transplantation offers the possibility of overcoming this problem; however, it entails the use of immunoisolation devices to prevent immune rejection of the transplanted islets. These devices consist of a semipermeable membrane, which surrounds the islets and isolates them from the host's immune system, while allowing the passage of insulin and essential nutrients, including glucose. Problems associated with proposed device designs include diffusion limitations, biocompatibility, device retrieval in the event of failure, and mechanical integrity. Microencapsulation appears to be the most promising system of immunoisolation, however, the design of a device suitable for human clinical use remains a challenge. © 1994 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1040-0397
    Keywords: Chronopotentiometry ; Transition time ; Calibration ; Least median squares regression ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability of the least median squares (LMS) method in detection of several straight segments in experimental continuous curves is tested using chronopotentiometric data. As a common experimental system, the chronopotentiometric reduction of Fe(CN)63- on a Pt electrode is used for this purpose. LMS allows for the correct estimation of transition times and then, for the calibration of the system. LS calibration without outliers detected by LMS assures a better prediction and therefore better calibration quality, because the standard error of estimation is 32.43% less than one obtained with the whole data.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Advanced Materials 8 (1996), S. 251-253 
    ISSN: 0935-9648
    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
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Polymer Science 54 (1961), S. 107-115 
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The reduction of acrylonitrile at mercury electrodes has been studied both polarographically and coulometrically at controlled potential. The half-wave potential is about 1.6 v. versus a mercury pool both for pure acrylonitrile and for acrylonitrile in dimethylformamide, in the presence and absence of water. As long as water is present the diffusion current is directely proportional to the concentration of acrylonitrile, at least up to 0.2 mg./ml. In the absence of water, reduction of acrylonitrile in dimethylformamide at this potential leads to condensation of reactions initiated by the carbanion. The diffusion current is no longer proportional to the concentration. Comparison of electrolytic- and sodium-reduction products of acrylonitrile gives information about the mechanisms of these reductions and the role of water in the polarographic analysis. A new yellow sodium-reduction polymer of acrylonitrile is described, and data on the ultraviolet and infrared spectra are presented.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 172 (1989), S. 25-35 
    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 Werte des Elastizitätsmoduls (E) und der Fließspannung (Y) und die Gestalt der Spannungs-Dehnungskurven wurden mit der Mikrohärte (MH) dieser Materialien verknüpft, unter Beachtung der Rolle, die die kristallinen, amorphen und Phasengrenzbereiche bei der Verformung der kristallinen Polymeren spielen. Es wurden lineare Beziehungen zwischen der Mikrohärte und dem Kristallinitätsgrad (1-λ)d und zwischen den Logarithmen von E und MH gefunden. Die Änderungen der Parameter 100 Y/E und σmin/Y (σmin ist das relative Minimum der Nominalspannung für Dehnungen oberhalb der Streckgrenze) als Funktion von (1-λ)d folgen unterschiedlichen Trends für lineare und verzweigte Polyethylene. Außerdem zeigte sich, daß das Verhältnis MH/Y für diese Materialien kleiner als drei ist, wobei dieser theoretische Wert (Taborgleichung) nur bei den höchsten Kristallinitätsgraden angenähert wird.
    Notes: The values of the elastic modulus (E) and the yield stress (Y) and the shape of the strain-stress curves of different polyethylenes have been related to the microhardness (MH) of these materials, considering the roles that the crystalline, amorphous, and interfacial regions play in the deformation of semicrystalline polymers. Linear relations between microhardness and degree of crystallinity, (1 - λ)d, and between the logarithms of E and MH have been found. The variations of the parameters 100Y/E and σmin/Y (σmin is the relative minimum value of the nominal stress for elongations above the yield point) as a function of (1-λ)d follow different trends for linear and branched polyethylenes. Moreover, it has been found that the ratio MH/Y is smaller than three for these materials, approaching this theoretical value (Tabor relation) only for the highest crystallinity levels.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 175 (1990), S. 141-156 
    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: Bei der Polycondensation von d,l-Asparaginsäure mit Nδ-phthaloyl-L-ornithin in Phosphorsäure bei 185°C entstehen statisticsche Copolymere (Ausbeute 60  -  70%) aus Poly(d,l-succinimid-co-Nδ-phthaloyl-d,l-ornithin), Formel 6, mit inhärenten Viskositäten (DMF) von 5 bis 15 ml g-1. Copolyimide der selben Zusammensetzung 6 und vergleichbarer Kettenlänge werden aus Asparaginsäure und dem Kupferchelat des Phthaloylornithins erhalten. Die Behandlung des Copolymeren 6 mit Hydrazinhydrat fuhrt zur Öffnung der Succinimid-Kettenglieder unter Bildung von Hydrazid-Seitengruppen. Die resultierenden Polyamide sind Poly(α,β-d,l-asparaginsäurehydrazid-co-d,l-ornithin), Formel 7. Kürzere Reaktionszeiten bedingen unvollständige Ringöffnung, und die verbleibenden Succinimid-Gruppen werden bei der folgenden Aufarbeitung hydrolytisch gespalten unter Bildung von Asparaginsaüre-Gruppen; die sogebildeten Polyamide besitzen die Struktur 8. Beide Polymere, 7 und 8, sind in Wasser loslich und zeigen in Wasser inharente Viskositiiten von 5 bis 14 ml g-l. Die Fahigkeit dieser Polyamide zur Arzneimittelverankerung wird durch Ankoppeln von Carbonsau- ren als Modellsubstanzen gezeigt.
    Notes: The polycondensation of d,l-aspartic acid with Nδ-phthaloyl-l-ornithine in phosphoric acid at 185°C gives rise to the formation, in 60  -  75% yield, of random copolymers of the poly(d,l-succinimide-co-Nδ-phthaloyl-D,L-ornithine) type 6 possessing inherent viscosities (DMF) in the range of 5  -  15 ml g-1. Copolyimides of the same compositions 6 and comparable chain lengths are obtained from aspartic acid and the copper chelate of the phthaloylornithine. Treatment of copolymers 6 with hydrazine hydrate in DMF leads to N-deprotection and opening of the intrachain succinimide rings with formation of hydrazide side groups. The resultant polyamides are of the poly(α,β-d,l-asparthydrazide-co-d,l-ornithine) type 7. Shorter reaction periods give incomplete hydrazinolytic ring opening, and the remaining succinimide units are cleaved hydrolytically during the subsequent aqueous workup, thereby transforming into aspartic acid units. The polyamides so formed possess the general poly(α,β-d,l-asparthydrazide-co-α,β-d,l-aspartic acid-co-d,l-ornithine) structure 8 Both types 7 and 8 are soluble in water and, in this medium, give inherent viscosities of 5  -  14 ml g-1. The potential drug-anchoring capabilities of these amine-functionalized polyamides are demonstrated by coupling reactions with model carboxylic acids.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 7
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The treatment of artemisinin (1) and β-artemether (6) with Zn dissolving in AcOH for a few hours results in mono-deoxygenation giving deoxyartemisinin (5) and deoxy-β-artemether (7), respectively, as the sole product. In contrast, submission of 1 to FeCl2 · 4 H2O in MeCN at room temperature for 15 min causes only isomerization, (3aS,4R,6aS,7R,10S,10aR)-octahydro-4,7-dimethyl-8-oxo-2H-10H-furo[3,2-i] benzopyran-10-yl acetate (8) and (3R)-3-hydroxydeoxyartemisinin (9) being produced in 78 and 17% yield, respectively. The action of FeCl2 · 4 H2O in MeCN on 6 is similar. Under the same conditions, 6 gives products analogous to 8 and 9 accompanied by an epimeric mixture of 2-[4-methyl-2-oxo-3-(3-oxobutyl)cyclohexyl]propanaldehyde in yields of 32, 23, and 16%, respectively. No epoxide is formed on repeating the last two experiments in the presence of cyclohexene. The deoxygenation of 1 and 6 by Zn is rationalized in terms of its oxophilic nature. The catalyzed isomerization of 1 and 6 by Fe2+ is attributed to the redox properties of the Fe2+/Fe3+ system.
    Additional Material: 1 Tab.
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  • 8
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 2 (1988), S. 129-141 
    ISSN: 0268-2605
    Keywords: Ferrocenylalkane acids ; ferricenium salts ; oxidation ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: As part of a project to provide hydrophilic ferricenium compounds for biomedical investigations, several ferrocenyl-alkanoic and -alkanedioic acids, including ferrocenylacetic, β-ferrocenylpropionic and γ-ferrocenylbutyric acids, ferrocylmalonic acid, and the two thioether derivatives, S-ferrocyl- β-mercaptopropionic acid and S-ferrocylthiomalic acid, are chemically oxidized to the respective ferricenium salts. While oxidation with the nitromethane/tetrafluoroboroboric acid system affords poorly crystallizing tetrafluoroborate salts, for the most part possessing unsatisfactory solubility characteristics, more hydrophilic salts containing the tetrachloroferrate(III) (FeCl4-) counterion, albeit contaminated with FeCl2, are obtained by treatment of the substrate acids with excess iron(III) chloride. The most promising method of ferricenium generation investigated in this study involves oxidation by means of the p-benzoquinone-HCL-FeCl3 system, which directly provides the respective ferricenium tetrachloroferrate salts. The IR and Mössbauer spectra confirm the expected ferricenium structures. The method appears attractive enough to be utilized in future investigations involving more complex notably polymeric, derivatives of the ferrocene parent compound.
    Additional Material: 2 Tab.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Applied Organometallic Chemistry 12 (1998), S. 793-799 
    ISSN: 0268-2605
    Keywords: anticancer ; antineoplastic ; ferrocene/ferricenium ; biological redox ; free radical ; polyaspartamide ; tumor ; Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ferrocene/ferricenium redox system plays a significant role in biological oxidation, reduction and free-radical reactions. Of particular interest are the findings of earlier investigations which showed certain water-soluble ferricenium salts to possess appreciable antiproliferative activity against various murine tumor lines and a xenografted human colorectal adenocarcinoma. Solubility in water, a prerequisite for efficacious transport and dissipation in central circulation, was then proposed as a principal requirement for the ferrocene complex system to exert antineoplastic activity irrespective of the oxidation state in which it is administered. In order to shed more light on this question, we decided to investigate the antiproliferative properties of polymer-ferrocene conjugates containing the metal complex in the non-oxidized (ferrocene) form while fulfilling the critical requirement of water solubility. To this end, five selected, water-soluble conjugates, synthesized by reversible coupling of 4-ferrocenylbutanoic acid to variously structured polyaspartamides featuring pendant primary amino groups as coupling sites, were tested in vitro against cultured HeLa cells at concentrations up to 50 µg Fe ml-1. Optimal antiproliferative activities, with IC50 in the range of 2-7 µg Fe ml-1, were determined for three compounds possessing tertiary-amine functions susceptible to protonation at physiological pH. Lower activities (IC50 = 45-60 µg Fe ml-1) were demonstrated for two poly(ethylene oxide)-containing conjugates. However, no reasonable structure-performance relationships can be derived at this stage from the small number of compounds tested. Copyright © 1998 John Wiley & Sons, Ltd.
    Additional Material: 2 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Electrophoresis 9 (1988), S. 812-815 
    ISSN: 0173-0835
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Histones from maize embryos and seedlings have been isolated using a fast extraction procedure. Three different electrophoretic systems have been applied for the study of the heterogeneity of maize core histones. Electrophoresis in acetic acid/urea polyacrylamide gels, containing high concentrations of urea, resulted in optimum fractionation of the core histones and especially of histone H4. Sodium dodecyl sulfate- containing polyacrylamide gels were not useful for the fractionation of maize histone classes H2a and H2b, nor for the various subfractions of H3 and H4. Gels containing Triton X-100, used for the dimension in two-dimensional electrophoresis proved to be efficient for the separation of all histone classes, as well as their structural variants and chemical modifications. Maize core histones have been oxidized in an attempt to define which of the Triton X-100 resolved subfractions represent oxidation forms.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
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