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  • Inorganic Chemistry  (8)
  • Biochemistry and Biotechnology  (7)
  • Polymer and Materials Science  (7)
  • 1
    ISSN: 0006-3592
    Keywords: catabolite repression ; protein A ; membrane proteins ; continuous culture ; protein expression ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Although widely used in experimental and industrial situations, genetically engineered plasmids containing the lac promoter from Escherichia coli are subject to catabolite repression when grown in glucose-containing media. Several methods of overcoming this problem have been investigated by studying the expression of the protein A gene from Staphylococcus aureus under the control of the Escherichia coli lac promoter. When glycerol is used as a sole carbon source, the plasmid is unstable and is rapidly lost from the culture. When the bacteria are grown in chemostats under glucose limitation, the plasmid is maintained, even at high dilution rates, and the expression of protein A is similar to that observed when glycerol was used. The balance between metabolic load and protein A expression seems to be maintained by reducing the gene dose to a tolerable level. Depending on the metabolic conditions prevailing in the culture, this is achieved, either by reducing the copy number of the plasmid or in extreme cases by removing the plasmid altogether.
    Additional Material: 10 Ill.
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  • 2
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 49 (1996), S. 601-610 
    ISSN: 0006-3592
    Keywords: aerobic ; anaerobic ; biomass separation ; bioreactor ; bubbleless ; oxygen mass transfer ; extraction of organic pollutants ; membrane ; wastewaters ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Combining membrane technology with biological reactors for the treatment of municipal and industrial wastewaters has led to the development of three generic membrane processes within bioreactors: for separation and recycle of solids; for bubbleless aeration of the bioreactor; and for extraction of priority organic pollutants from hostile industrial wastewaters. Commercial aerobic and anaerobic membrane separation bioreactors already provide a small footprint alternative to conventional biological treatment methods, producing a high-quality effluent at high organic loading rates. Both the bubbleless aeration and extractive membrane bioreactors are in the development stages. The former uses gas-permeable membranes to improve the mass transfer of oxygen to the bioreactor by providing bubbleless oxygen. By using a silicone membrane process, extractive membrane bioreactors transfer organic pollutants from chemically hostile wastewaters to a nutrient medium for subsequent biodegradation. All three membrane bioreactor (MBR) processes are comparatively and critically reviewed. © 1996 John Wiley & Sons, Inc.
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  • 3
    ISSN: 0006-3592
    Keywords: hydrolysis ; esterification ; Humicola lanuginosa ; Rhizomucor miehei ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Humicola lanuginosa lipase (HIL) and Rhizomucor miehei lipase (RrnL), isolated from commercial preparations of Lipolase and Lipozyme, respectively, were solubilized in AOT-stabilized water-in-oil (w/o) microemulsions in n-heptane and aspects of their hydrolysis and condensation activity examined. The temperature dependence of HIL hydrolysis activity in unbuffered R = 10 microemulsions matched very closely that for tributyrin hydrolysis by Lipolase in an aqueous emulsion assay. Apparent activation energies were measured as 13 ± 2 and 15 ± 2 kJ mol / respectively. Condensation activity, however, was essentially independent of temperature over the range 5° to 37°C. The stability of HIL over a 30-day period was very good at all pH levels (6.1, 7.2, 9.3) and R values studied (5, 7.5, 10, 20), except when high pHs and low R values were combined. The excellent stability was reflected by the linearity of the productivity profiles which facilitate system optimization. The temperature dependence of RmL hydrolysis activity toward pNPC4 showed a maximum at 40°C and an apparent Eact = 20 ± 2 kJ mol-1 was calculated based on the linear region of the profile (5° to 40°C). RmL esterification activity showed only a slight dependence on temperature over the studied range (0° to 40°C) and an apparent Eact = 5 ± 1 kJ mol-1 was measured for octyl decanoate synthesis. Both RmL and HIL, therefore, have potential for application in low temperature biotransformations in microemulsion-based media. The stability of RmL over a 30-day period was good in R = 7.5 and R = 10 microemulsions containing pH 6.1 buffer, and this was reflected in the linearity of their respective productivity profiles. RmL stability was markedly poorer at more alkaline pH, however, and proved to be sensitive to relatively small changes in the R value. © 1995 John Wiley & Sons, Inc.
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  • 4
    ISSN: 0006-3592
    Keywords: hydrolysis ; esterification ; Humicola lanuginosa ; Rhizomucor miehei ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lipolase and Lipozyme are produced in large quantities (as a result of genetic engineering and overexpression) for the detergents market and provide a cheap source of highly active biocatalysts. Humicola lanuginosa lipase (HIL) and Rhizomucor miehei lipase (RmL) have been isolated in partially purified form from commercial preparations of Lipolase and Lipozyme, respectively. These lipases were solubilized in Aerosol-OT (AOT)-stabilized water-in-oil (w/o) microemulsions in n-heptane. HIL and RmL activity in these microemulsions was assayed by spectrophotometric measurement of the initial rate of p-nitophenyl butyrate hydrolysis, and by chromatographic determination of the initial rate of octyl decanoate synthesis from 1-octanol and decanoic acid. The hydrolytic activity of HIL in microemulsions measured as a function of buffer pH prior to dispersal, followed a sigmoidal profile with the highest activities observed at alkaline pHs. This broadly matches the pH-activity profile for tributyrin hydrolysis by Lipolase in an aqueous emulsion assay. The hydrolytic activity of RmL in the same microemulsions, measured as a function of pH, gave a bell-shaped profile with a maximum activity at pH 7.5. Again, the observed pH-activity profile was similar to that reported for a purified RmL in a tributyrin-based aqueous emulsion assay. In contrast, the esterification activity exhibited by both HIL and RmL in AOT microemulsions over the available range pH 6.1 to 10.4, decreases as the pH increases, most likely reflecting the effect of substrate ionization. The dependence of the hydrolytic and condensation activity of HIL on R, the mole ratio of water to surfactant, were similar with both profiles exhibiting a maximum at R = 5. The hydrolytic and esterification activities of RmL followed similar R-dependent profiles, but the profiles in this case exhibited a maximum at R = 10. The water activities at these R values were directly measured as 0.78 and 0.9, respectively. Measured water activities were unperturbed by the presence of lipase at the concentrations used in these studies. © 1995 John Wiley & Sons, Inc.
    Additional Material: 14 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 118 (1985), S. 116-123 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Properties of Tetrakis(trifluoromethyl)-1,3-dithietane S-Oxides and Bis(triflouromethyl)sulfineThe corresponding S-oxides 2-6 could be obtained by oxidation of 2,2,4,4-tetrakis(trifluoromethyl)-1,3-dithietane (1). Similar oxidation of 2,2,4,4-tetrakis(trifluoromethyl)thiirane (8) yields the episulfoxide 12, but not the episulfone 14. Pyrolysis of 2, 3, 5, and 6 have been investigated and bis(trifluoromethyl)sulfine (7) could be isolated as the first member of perfluoroalkylsulfines as well as the sulfonylfluoride 13 being the product of isomerization of bis(trifluoromethyl)-sulfene (9). 7 could also be obtained by ring opening from 3 with bases and by oxidation of hexafluorothioacetone (11), respectively. Solvolytic ring opening in 5 and 6 yields the sulfones 16 and 17.
    Notes: Durch Oxidation des 2,2,4,4-Tetrakis(trifluormethyl)-1,3-dithietans (1) erhält man dessen S-Oxide 2-6. Auf gleiche Weise gelingt die Oxidation des 2,2,4,4-Tetrakis(trifluormethyl)thiirans (8) zum Episulfoxid 12, nicht jedoch zum Episulfon 14. Die Pyrolysen von 2, 3, 5 und 6 wurden untersucht, wobei als erster Vertreter der Perfluoralkylsulfine das Bis(trifluormethyl)sulfin (7) sowie das Sulfonylfluorid 13 als Isomerisierungsprodukt des Bis(trifluormethyl)sulfens (9) isoliert wurden. 7 entsteht auch durch Ringöffnung aus 3 mit Basen bzw. bei der Oxidation des Hexafluorthioacetons (11). Die Solvolyse von 5 und 6 liefert unter Ringöffnung die Sulfone 16 und 17.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Berichte der deutschen chemischen Gesellschaft 116 (1983), S. 1623-1630 
    ISSN: 0009-2940
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Synthesis and Properties of New Perhalogenated 1,3-Dithietane S-OxidesNew perchlorinated and perfluorinated 1,3-dithietanes (4, 6, 7, 12, 14, 15), which are partially oxidized at the sulfur atoms, are described. Pyrolysis of the 1,3-dioxides 7 and 15 leads to the sulfoxides 8 and 16, X2C = S = O (X = Cl, F). respectively. Two new oxidizing agents are used: trifluoromethane- and nonafluorobutanepersulfonic acid.
    Notes: Die neuen perchlorierten und perfluorierten, am Schwefel partiell oxidierten 1,3-Dithietane 4, 6, 7, 12, 14 und 15 werden beschrieben. Pyrolysen der 1,3-Dioxide 7 und 15 führen zu den Sulfoxiden 8 bzw. 16, X2C = S = O (X = Cl, F). Zwei neue Oxidationsmittel werden angewendet: Trifluormethan- und Nonafluorbutanpersulfonsäure.
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  • 7
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Ultraviolet irradiation of polyethylen, nylon, Mylar, and Acrilan produces higher scission-to-crosslinking ratios when irradiation is performed in a nitrogen atmosphere than it does when irradiation is in a vacuum. Irradiation of polyethylene in nitrogen causes a sharp decrease in molecular weight while irradiation of Acrilan in vacuum causes an equally notable increase in molecular weight.
    Additional Material: 4 Ill.
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  • 8
    ISSN: 0022-3832
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Volatile decomposition products of ultraviolet-irradiated polyethylene, nylon, Mylar, and Acrilan have been analyzed. The principal decomposition products of polyethylene are hydrogen and methane. Besides hydrogen and methane, carbon monoxide occurs in considerable amounts in the decomposition products of the other polymers. There is a considerable difference in the relative abundances of methane and hydrogen in the decomposition products, depending on whether irradiation was performed in a vacuum or in nitrogen. Decomposition products of ultraviolet-irradiated nylon include all of the primary amines from methyl through hexyl. Mechanisms consistent with the observed results of photolysis are proposed.
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  • 9
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 7 (1983), S. 123-127 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: The apparatus described in DIN 4842 was used to measure the heat transmission of a series of Nomex, polyester-cotton, Proban®-Treated cotton, untreated cotton and wool workwear fabrics subjected to a radiant heat source. Heat transmission was found to be dependent on the incident heat flux, fabric weight and fabric thickness. At the heat flux levels tested, 10 KJ m-2s-1 and 20 KJ m-2s-1, heat transmission was found to be largely independent of the fibre composition of the fabric when single layers of fabric were tested. The level of heat transmission was reduced by the use of multiplayer assemblies or a reflective aluminium coating, but the greatest reduction was obtained when air spaces were interposed between the fabrics. Conbinaitons of fabrics were developed which transmitted less than 205 KJ m-2s-1 during testing at incident heat flux levels of 10 KJ m-2s-1 and 20 KJ m-2s-1.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Fire and Materials 13 (1988), S. 223-229 
    ISSN: 0308-0501
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Architecture, Civil Engineering, Surveying , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Difficulties encountered in bulk transportation of red phosphorus can be overcome by making an intimate blend with alumina trihydrate. The blend is suitable for direct use with more alumina hydrate in a synertistic flame retardant system for epoxy resin mouldings. The degree of observed synergism allows low loadings of the addivities and consequently the electrical and physical properties of the mouldings are only slightly affected.
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