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  • Polymer and Materials Science  (38)
  • General Chemistry  (20)
  • Life and Medical Sciences  (5)
  • 1995-1999  (63)
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  • 1
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 29 (1995), S. 893-899 
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: There is much discussion about the toxic effect of vanadium and aluminum contained in Ti—6Al—4V alloy for prosthetic implants. The goal of the present investigation was to develop new titanium alloys with sufficient mechanical properties using more biocompatible alloying elements: zirconium, tin, niobium, tantalum, and palladium. The relative growth rates of L929 and MC3T3-E1 cells were significantly higher when cultured with the extraction of Ti—10Zr—8Nb—2Ta—0.2Pd or Ti—15Zr—4Nb—2Ta—0.2Pd alloys than when cultured with the extraction of Ti—6Al—4V ELI alloy. The tensile strength, elongation, and reduction of area for Ti—15Sn—4Nb—2Ta—0.2Pd alloy were 989 MPa, 14.4%, and 49.3%, respectively, surpassing Ti—6Al—4V ELI alloy (ASTM F138—84); those for Ti—15Zr—4Nb—2Ta—0.2Pd alloy were 725 MPa, 23.6% and 54.9%, respectively. More than 15% addition of tin as well as zirconium deteriorated the tensile properties. Titanium release into a 5% hydrochloric acid solution from the new titanium alloys was 20-50 μg/cm2 per day, though that from Ti—6Al—4V ELI alloy was 1300 μg/cm2 per day. The optimum alloy compositions are Ti—15Zr—4Nb—2Ta—0.2Pd and Ti—15Sn—4Nb—2Ta—0.2Pd, judging from cytocompatibility, corrosion resistance, and mechanical properties. The former is characterized by its high level cytocompatibility and corrosion resistance, while the latter is characterized by mechanical properties. © 1995 John Wiley & Sons, Inc.
    Additional Material: 6 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York : Wiley-Blackwell
    Biopolymers 38 (1996), S. 557-566 
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The molecular and crystal structure of curdlan triacetate, acetylated (1 → 3)β-D-glucan, was analyzed by means of an x-ray diffraction technique with the help of the linked-atom least-squares method. Unit cell dimensions are a = b = 11.00(1), c(fiber axis) = 22.91 (9) Å, and γ = 120°. The space group is P61. The unit cell contains six chemical repeating units related by 6/I-helical symmetry, which is essentially the same as the backbone conformation of one of the modifications (form I) of curdlan. During the refinement calculation, the terminal methyl in every acetyl moiety was elastically restrained to the trans conformation commonly observed in related oligosaccharide structures. The difference Fourier map, the observed and calculated densities, and the thermogravimetric measurement indicated one water molecule per glucose residue. The water oxygen is linked to two carbonyl oxygens in adjacent molecules by hydrogen bonds. The conformation of the primary acetyl moiety is a (skew, -gauche, trans). So far, no skew conformation was observed for the primary acetyl and hydroxyl moieties except in α, β-panose. In both cases, the unusual eclipsed orientation of the primary group is attributed to the hydrogen bond and this conformation is quite different from that of pachyman triacetate. © 1996 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 248 (1997), S. 85-94 
    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: In der vorliegenden Studie wurde die Permeation und Separation von Kohlendioxid durch eine wassergequollene Chitosanmembran untersucht. Die Chitosanmembran wurde durch in einem Trägergas enthaltenen Wasserdampf gequollen und zeigte nach dieser Behandlung eine hohe Gaspermeabilität. Bei Raumtemperatur durchdrang vorzugsweise Kohlendioxid die gequollene Chitosanmembran mit einer Permeabilität von 2,5·10-8 cm3 (STP) cm(s cm2 cmHg)-1 und einem CO2/N2 Trennfaktor von 70.Diese Trennleistung für Kohlendioxid wird durch die basischen Eigenschaften der Aminogruppen den Chitosanmolekülen hervorgerufen.Die Membranherstellungsbedingungen, wie zum Beispiel die Essigsäurekonzentration der Gießlösung, beeinflußten die Permeationsgeschwindigkeit. Der Einfluß der Arbeitstemperatur wurde ebenfalls untersucht. Um die Trennleistung der Membran zu erhöhen, wurden verschiedene Methoden der Membranbehandlung und Arbeitsbedingungen untersucht.
    Notes: The permeation and separation of carbon dioxide through a water-swollen chitosan membrane was studied. A chitosan membrane was swollen by water vapor contained in a feed gas and, thus treated, exhibited a large gas permeability. Carbon dioxide preferentially permeated through the swollen chitosan membrane with a permeability of 2.5·10-8 cm3 (STP) cm(s cm2 cmHg)-1 and a CO2/N2 separation factor of 70 at room temperature. This separation performance for CO2 resulted from the basic properties of the chitosan amino groups. The membrane preparation conditions, such as acetic acid concentration of the casting solution, affected the membrane permeation rate. The effect of the operation temperature was also measured. To increase the separation performance of the membrane, several methods of membrane treatment and operation were evaluated.
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 33 (1995), S. 1059-1067 
    ISSN: 0887-624X
    Keywords: radical polymerization ; methyl trans-β-vinylacrylate ; kinetics propagation radical ; monomer reactivity ratios ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Methyl trans-β-vinylacrylate (MVA) undergoes radical polymerization with α,α′-azobis(isobutyronitrile) (AIBN) in bulk and solution. The polymer obtained consists of 85% trans-1,4 and 15% trans-3,4 units. Poly(MVA) (PMVA) is readily soluble in common organic solvents, but insoluble in n-hexane and petroleum ether. PMVA exhibits a glass transition at 60°C, and loses no weight up to 300°C in nitrogen. The kinetics of MVA homopolymerization with AIBN was investigated in benzene. The rate of polymerization (Rp) can be expressed by Rp = k[AIBN]0.5[MVA]1.0, and the overall activation energy has been calculated to be 94 kJ/mol. The propagation radical of MVA at 80°C was detected by ESR spectroscopy, which indicated that the unpaired electron of the propagating radical was completely delocalized over the three allyl carbons. Furthermore, the steady-state concentration of the propagating radical of MVA at 60°C was determined by ESR spectroscopy, and the propagation rate constant (kp) was calculated to be 1.25 X 102 L/mol ·s. Monomer reactivity ratios in copolymerization of MVA (M2) with styrene (M1) are r1 = 0.16 and r2 = 4.9, from which Q and e values of MVA are calculated as 4.2 and -0.32, respectively. © 1995 John Wiley & Sons, Inc.
    Additional Material: 12 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2181-2187 
    ISSN: 0887-624X
    Keywords: acyl oxime ; polarity alteration ; main-chain scission ; energy transfer ; photoresist ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Photochemical reactions of copolymers of O-acryloyl acetophenone oxime (AAPO) and phenyl vinyl ketone (PVK) in the solid phase were investigated. The decrease of molecular weight of these copolymers in the photolysis was limited compared to that of PVK homopolymer. Results of IR and elemental analyses showed that pendant acyloxyimino (AOI) groups were phototransformed into the pendant amino groups. This behavior suggests that PVK units in this copolymer worked as a sensitizer for the photolysis of AOI groups. The energy transfer from PVK units to AOI groups was confirmed to proceed via an excited triplet state by the quenching study of phosphorescence of a PVK homopolymer by a model compound, O-cyclohexanecarbonyl acetophenone oxime. Dissolution alteration of AAPO copolymers before and after irradiation was also investigated. © 1996 John Wiley & Sons, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2533-2542 
    ISSN: 0887-624X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A direct method of simultaneously polymerizing and forming acetylene monomer to produce uniformly thin films of polyacetylene was investigated in terms of catalyst system, catalyst concentration, and polymerization temperature. The best catalyst was a Ti(OC4H9)4,-AI(C2H5)3 system (Al/Ti = 3-4) and the critical concentration was 3 mmole/l. of Ti(OC4H9)4. Below the critical concentration, only a solid or a powder was obtained. The configuration of the polymers obtained depends strongly upon the polymerization temperature. Thus an all-cis polymer was obtained at temperatures lower than -78°C, whereas an all-trans polymer resulted at temperatures higher than 150°C. Observations either in an electron microscope by direct transmission or in a scanning electron microscope showed that the film is composed of an accumulation of fibrils about 200-300 Å in width and of indefinite length.
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  • 7
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2925-2929 
    ISSN: 0887-624X
    Keywords: substituted polyacetylene ; poly(diphenylacetylene) ; germanium-containing polymer ; metathesis polymerization ; tantalum catalyst ; thermal stability ; gas permeability ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1-Phenyl-2-[m-(trimethylgermyl)phenyl]acetylene (m-Me3GeDPA) and 1-phenyl-2-[p-(trimethylgermyl)phenyl]acetylene (p-Me3GeDPA) polymerized with TaCl5-cocatalyst systems to provide in high yields new polymers having weight-average molecular weights over 1 × 106. Poly(m-Me3GeDPA) was a yellow solid, which completely dissolved in toluene, chloroform, etc., to form a tough film by solution casting. Poly(p-Me3GeDPA) was also a yellow solid and partly insoluble in any solvents. The onset temperatures of weight loss for these polymers in the thermogravimetric analysis in air were as high as ca. 400°C. The oxygen permeability coefficient of poly(m-Me3GeDPA) was 1100 barrers (25°C), which is about twice that of poly(dimethylsiloxane). © 1996 John Wiley & Sons, Inc.
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 2873-2880 
    ISSN: 0887-624X
    Keywords: polyaddition ; bis(oxetane) ; aromatic dithiol ; catalyst ; quaternary onium salt ; crown ether complex ; new reactive polymer ; pendant primary hydroxyl group ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Addition reaction of (3-methyl-3-oxetanyl)methyl acetate (MOMA) with bis(4-mercaptophenyl) sulfide (BMPS) was examined in certain organic solvents. When the reaction of MOMA with BMPS was performed without any catalyst in hexamethylphosphoric triamide (HMPA) and N-methyl-2-pyrrolidone (NMP) at 130°C for 24 h, conversions of the corresponding adduct were 96 and 36%, respectively, which was confirmed by 1H-NMR spectra. On the other hand, when the reaction was carried out using tetraphenylphosphonium bromide (TPPB) as a catalyst under the same conditions, conversions of the adduct were 96 and 81% in HMPA and NMP, respectively. This result shows that although the addition reaction of oxetane compound with aromatic dithiol proceeds without any catalyst in HMPA, the reaction was strongly enhanced by adding TPPB in NMP. On the basis of the above results, polyadditions of bis((3-methyl-3-oxetanyl)methyl) terephthalate (BMOT) and bis((3-ethyl-3-oxetanyl)methyl) terephthalate with BMPS were performed using TPPB as the catalyst in NMP at 130°C for 24 h. As a result, the corresponding high molecular weight polymers 1 (Mn = 22,400) and 2 (Mn = 12,800) with pendant primary hydroxyl groups were obtained in 83 and 89% yields without any gel products, respectively. Furthermore, a low molecular weight oligomer was obtained from the polyaddition of BMOT with aliphatic dithiol, bis(mercaptomethyl)benzene, under the same reaction conditions. The catalytic activity on the polyaddition of BMOT with BMPS was also examined, and it was found that thermally stable TPPB and crown ether complexes at the reaction temperature (130°C) have higher catalytic activity than tetrabutylammonium bromide and tetrabutylphosphonium bromide to produce polymer 1 with high molecular weight. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 2873-2880, 1998
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  • 9
    ISSN: 1434-193X
    Keywords: Carbohydrates ; Glycals, nitro ; Michael additions ; Glycosylations ; Glycosides, galactosamine ; Reduction, nitro group ; Glycopeptides ; Chemistry ; General Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: -Michael addition of serine and threonine derivatives 4a-4c to 3,4,6-tri-O-benzyl-2-nitro-D-galactal (1) afforded the corresponding 2-deoxy-2-nitro-α-D-galactopyranosides 5a-5c in good yield and stereoselectivity. 2-deoxy-2-nitroglycosides 5a and 5b were reduced to the 2-acetamido compounds by platinized Raney nickel T4. Manipulation of the protecting groups afforded known N-Fmoc-O-(2-acetamido-3,4,6-tri-O-acetyl-2-deoxy-α-D-galactopyranosyl)-L-serine (8a) and -threonine (8b), valuable building blocks for O-glycopeptide synthesis.
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  • 10
    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: 2 Ill.
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