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  • Wiley-Blackwell  (36)
  • 2000-2004
  • 1995-1999  (36)
  • 1985-1989
  • 1997  (36)
  • 1
    ISSN: 0018-019X
    Keywords: Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The hydroxo complex (Bu4N)2[Ni2(C6F5)4(μ-OH)2]reacts with 2,3,4,5,6-pentafluoro benzenamine (C6F5-NH2), 1,3-diaryltriaz-1-enes (ArNH—N=N—Ar, Ar = Ph, 4-MeC6H4, 4-MeOC6H4), 7-aza-1H-indole (= 1H-pyrrolo[2.3-b]pyridine; Hazind), N-phenylpyridin-2-amine(pyNHPh), and N-phenylpyridine-2-carboxamide (py-CONHPh) at room temperature in acetone to give the binuclear complexes (Bu4N)2[Ni2(C6F5)4(μ-C6F5NH)2] (1) and (Bu4N)2[{Ni(C6F5)2} 2(μ-OH)(μ-azind)] (2) and the mononuclear complexes Bu4N[Ni(C6F5)2(ArN3Ar)] (3-5), Bu4N[Ni(C6F5)2(pyNPh)] (6), and Bu4N[Ni(C6F5)2(pyCONPh)] (7). The hydroxo.complex (Bu4N)2[{Ni(C6F5)2-(μ-OH)}2] promotes the nucleophilic addition of water to pyridine-2-carbonitrile, 2-aminoacetonitrile, and 2-(dimethylamino)acetonitrile, and complexes 8-10 containing pyridine-2-carboxamidato, 2-aminoacetamidato and 2-(dimethylamino)acetamidato ligands are formed. Analytical (C, H, N) and spectroscopic (IR, 1H and 19F-NMR, and FAB-MS) data were used for structural assignments. A single-crystal X-ray diffraction study of (Bu4N)2[{Ni(C6F5)2}2(μ-OH)(μ-azind)] (2) established the binuclear nature of the anion; the two Ni-atoms are bridged by an OH group and a 7-aza-7H-indol-7-yl group, but the central Ni—O—Ni—N—C—N ring is not planar, the dihedral angle between the Ni—O—Ni and Ni—N—C—N—Ni planes being 84.4°.
    Additional Material: 2 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 55 (1997), S. 252-260 
    ISSN: 0006-3592
    Keywords: lipase ; chemical modification ; stability ; esterification ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Semipurified lipase of Candida rugosa (CRSL) was subjected to chemical modification, and the activities of the modified lipase, in hydrolysis and esterification reactions, were examined. The esterification reactions were carried out in the absence and presence of isooctane. When the enzyme was modified with polyethylene glycol (PEG), two methodologies were studied. The activation of PEG with p-NO2-phenylchloroformate gives better biocatalysts than those obtained with cyanuric chloride-PEG. The chemical modification with PEG increases the stability of pure lipases in isooctane at 50°C (extreme conditions). The chemically modified enzymes are useful for biotransformations in organic solvents. In addition the nitration of tyrosines with tetranitromethane was also studied. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 252-260, 1997.
    Additional Material: 5 Ill.
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  • 3
    ISSN: 0006-3592
    Keywords: tubular photobioreactors ; light distribution ; average solar irradiance ; light attenuation ; microalgae mass culture ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A mathematical model to estimate the solar irradiance profile and average light intensity inside a tubular photobioreactor under outdoor conditions is proposed, requiring only geographic, geometric, and solar position parameters. First, the length of the path into the culture traveled by any direct or disperse ray of light was calculated as the function of three variables: day of year, solar hour, and geographic latitude. Then, the phenomenon of light attenuation by biomass was studied considering Lambert-Beer's law (only considering absorption) and the monodimensional model of Cornet et al. (1900) (considering absorption and scattering phenomena). Due to the existence of differential wavelength absorption, none of the literature models are useful for explaining light attenuation by the biomass. Therefore, an empirical hyperbolic expression is proposed. The equations to calculate light path length were substituted in the proposed hyperbolic expression, reproducing light intensity data obtained in the center of the loop tubes. The proposed model was also likely to estimate the irradiance accurately at any point inside the culture. Calculation of the local intensity was thus extended to the full culture volume in order to obtain the average irradiance, showing how the higher biomass productivities in a Phaeodactylum tricornutum UTEX 640 outdoor chemostat culture could be maintained by delaying light limitation. © 1997 John Wiley & Sons, Inc. Biotechnol Bioeng 55: 701-714, 1997.
    Additional Material: 15 Ill.
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  • 4
    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: 6 Ill.
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  • 5
    ISSN: 0948-1907
    Keywords: CVD ; Ion beam ; Thin films ; Oxides ; Nitrides ; 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
    Notes: The ion-beam-induced chemical vapor deposition method for the preparation of thin films consists of the bombardment of a suitable substrate with O2⊕ or N2⊕ ions of relatively high energy while a flow of an organometallic precursor is directed onto its surface. Single and mixed oxides and nitride thin films can be prepared by this procedure. This paper describes the principles of the method, and presents some examples of thin films prepared with it (TiO2, PbTiO3, AlxTiyOz, AlN, and SnO2). Some characterization results of these thin films by different techniques are reported, with special emphasis on physical and electronic methods such as X-ray photoelectron spectroscopy (XPS), electron energy loss spectroscopy (EELS), and X-ray absorption spectroscopy (XAS). Other aspects, such as the preferential removal of C, H, and other impurity atoms from the precursors under the action of oxygen beams, or the possibility of performing lithographic depositions of these dielectric materials, are also considered.
    Additional Material: 9 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 549-559 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new route for the synthesis of high glass transition temperature, thermally stable polymer foams has been developed, using compositionally asymmetric microphase-separated block copolymers where the minor component (poly(propylene oxide)) is thermally labile and the major component (polyimide) is thermally stable. The minor component decomposes to low molecular weight species upon heating, and the decomposition products diffuse out of the film, leaving behind pores embedded in a matrix of the thermally stable component. In this study, the polyimide block was crosslinked with ethynyl functionalities to obtain a stable porous structure. The decomposition of the propylene oxide in the block copolymer was studied by thermogravimetric, dynamic mechanical and thermomechanical analyses. Mild conditions were required to avoid rapid depolymerization of the propylene oxide and plasticization of the polyimide matrix. The foams showed pore sizes with diameters up to a micrometer in size as well as the expected reduction in the mass density.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: This work deals with the coupling of model bioactive carboxylic acids (1-naphthylacetic acid, 2-(6-methoxy-2-naphthyl)propionic acid (naproxen) and nicotinic acid) to dextran by direct reaction with their potassium salts using pyridine/sulfonyl chloride as activating agent. The structure of the resulting polymeric derivatives was determined by means of 1H and 13C NMR spectroscopy. The influence of the pyridine concentration, the type of sulfonyl chloride and the temperature on the reaction of dextran with potassium 1-naphthyl acetate was evaluated. The activation energy was found to be 65,7 kJ/mol. 13C NMR spectra at 75,4 MHz of partially modified dextran with 1-naphthyl acetate groups were studied in order to evaluate the selectivity of the reaction between dextran and potassium 1-naphthyl acetate. Analysis of the spectra of ring carbons in the anhydroglucose units shows that the reactivity of the individual hydroxyl groups decreases in the order C2 〉 C4 〉 C3. The hydrolysis in the heterogeneous phase of some dextran polymers partially modified with 1-naphthyl acetate groups shows that the release of the bioactive compound is dependent on the hydrophilic character of the polymer as well as the pH value of the medium.
    Additional Material: 6 Ill.
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  • 8
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 35 (1997), S. 1127-1133 
    ISSN: 0887-6266
    Keywords: excimer ; fluorescence ; molecular dynamics ; naphthalene ; polyester ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Steady-state fluorescence measurements and molecular dynamics simulations have been used to study the intramolecular formation of excimers in five model compounds for polyesters containing naphthalene groups separated by flexible spacers. The model compounds are derived from 2-hydroxynaphthalene and HOOC—(CH2)n—COOH, n = 2-6. The ratio of the intensity of excimer and monomer emissions, ID/IM, is nearly independent of the viscosity of the medium, η, over the range covered in dilute solution. Although ID/IM is always very small, it shows an odd-even effect for the first four members of the series, with maxima when n is odd. Molecular dynamics simulations provide an explanation for the small values of ID/IM, their weak dependence on η, and the trend of ID/IM with n. The results for the present series of model compounds are compared with previous work, which reported larger values of ID/IM, and a stronger dependence of ID/IM on η, for bichromophoric compounds derived from 2-naphthoic acid and aliphatic glycols, where the direction of the ester groups is reversed. The origin of the difference in the behavior of ID/IM in the two series is identified. © 1997 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 35: 1127-1133, 1997
    Additional Material: 9 Ill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 2237-2247 
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Poly(vinyl alcohol) (PVAL) samples partially functionalized with 4-nitrophenyl carbonate groups were obtained by reaction of PVAL with 4-nitrophenyl chloroformate using pyridine as a catalyst. 2-Amino-2-deoxy-D-glucose (glucosamine) was virtually quantitatively bound to PVAL activated with 4-nitrophenyl carbonate groups. Glucosamine-carrying PVAL (PVAL-G) and Concanavalin A (Con A) in phosphate buffer (pH 7,2) at room temperature were proven to interact with each other.
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  • 10
    ISSN: 1022-1336
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: poly[isobutene-co-(p,m-chloromethylstyrene)]-graft-poly(2-methyl-2-oxazoline) graft copolymers (GP) were prepared by the “grafting from” method throught the cationic polymerization of 2-methyl-2-oxazoline (MeOXA) initiated by a statistical copolymer is isobutene and chloromethylstyrene. The unusual viscosity behavior in chloroform solution of these polymers, the dynamic laser light scattering analysis in aqueous solution, as well as the solubility in polar solvents like water and methanol demonstrate the amphiphilic character of the graft copolymers and indicate the formation of aggregates in solution.
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