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  • Chemistry  (47)
  • Surface physics, nanoscale physics, low-dimensional systems  (21)
  • SPACECRAFT PROPULSION AND POWER  (9)
  • Lunar and Planetary Science and Exploration  (8)
  • 1
    ISSN: 0887-624X
    Keywords: unnatural amino acids ; 5,5,5-trifluoroleucine ; azetidine-2-carboxylic acid ; thiazolidine-4-carboxylic acid ; mono-fluorophenylalanine (o,m,p) ; thienylalanine ; cellfree protein synthesis ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The ability to incorporate unnatural amino acids into biologically synthesized proteins will greatly extend the impact of protein engineering on polymer materials science. The present report describes the use of a rapid cell-free assay to assess the incorporation potential of unnatural amino acids in Escherichia coli. The assay features a coupled transcription-translation system (‘Zubay system’) to screen incorporation of amino acid analogs into plasmid-encoded proteins. Activity estimates are based on the ability of an analog to compete with a radiolabeled natural amino acid, and toxicity effects are screened by monitoring incorporation of a second, unrelated amino acid. The assay was established with analogs known to be active in vivo, using a common bacterial expression vector as template DNA. Positive results were obtained with the leucine analog 5,5,5-trifluoroleucine, the proline analogs azetidine-2-carboxylic acid and thiazolidine-4-carboxylic acid, and three isomers of mono-fluorophenylalanine (o,m,p). No activity was observed for the phenylalanine analogs 2-thienylalanine and 3-thienylalanine. The results suggest that the cell-free assay will be a useful predictor of in vivo incorporation and a useful tool in the design and synthesis of genetically engineered materials. © 1995 John Wiley & Sons, Inc.
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  • 2
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 34 (1996), S. 2817-2824 
    ISSN: 0887-624X
    Keywords: visible light photopolymerization ; tetraorganylborates ; fluorone dyes ; acrylic monomers ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Several new tetraorganylborate salts have been synthesized and tested as coinitiators with 2,4-diiodo-6-butoxy-3-fluorone (DIBF) for the photopolymerization of acrylic monomer mixtures. The rate of photopolymerization has been found to be a function of chemical structure of the borates. Stability, solubility, and reactivity of these borates as coinitiators for photopolymerization have been investigated. Diphenyldialkylborates have been found to be the best among the tested coinitiators. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
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  • 3
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 36 (1998), S. 1667-1677 
    ISSN: 0887-624X
    Keywords: photoinitiator ; iodonium borate salts ; photoinduced radical polymerization ; fluorone dye ; visible polymerization ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Iodonium butyltriphenylborate salts (A—I+—Ar′Ph3B-—R), (=Bu) were found to be more efficient than iodonium tetraphenylborate salts (R=Ph) when used as photoinitiators for the polymerization of acrylates. Relative photodecomposition rates were also different. It was found from a study of the photoreaction of iodonium borate salts with a model monomer, methyl methacrylate, that iodonium butyltriphenylborate salts simultaneously produce a butyl radical from the borate anion and an aryl radical from the iodonium cation upon irradiation. Both radicals initiate polymerization. Iodonium tetraphenylborate salts were found to release an aryl radical, but only from the iodonium cation. Iodonium borate salts exhibit strong absorption below 300 nm with a tail absorption above 400 nm. Thus, iodonium butyltriphenyl borate salts are efficient photoinitiators even when used with visible light. When a photosensitizer such as 5,7-diiodo-3-butoxy-6-fluorone is employed, iodonium butyltriphenylborate salts are rendered much more efficient for visible light photopolymerization. © 1998 John Wiley & Sons, Inc. J Polym Sci A: Polym Chem 36: 1667-1677, 1998
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  • 4
    Electronic Resource
    Electronic Resource
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 31 (1993), S. 2747-2750 
    ISSN: 0887-624X
    Keywords: SBR rubber ; crosslinking ; 1,2-bis(benzocyclobutenyl)ethane ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: 1,2-Bis(benzocyclobutenyl)ethane (BBCB) was used as a thermally activated crosslinking agent in styrene-butadiene rubber (SBR), both in the raw and carbon black-filled materials. Diels-Alder crosslinking reactions occurred to a significant degree, despite the lack of substituents of opposing electronic effects. The reaction is free of toxic crosslinking promoters and evolved by-products. Various physical properties such as ultimate elongation, tensile strength, and modulus were measured and compared to those properties of a sulfur-cured sample of SBR. Linear relationships were found between the amount of BBCB present and the modulus of the materials, as well as the amount of BBCB and solvent uptake in swell tests. © 1993 John Wiley & Sons, Inc.
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  • 5
    ISSN: 0899-0042
    Keywords: α-adrenergic ; imidayole analogs ; metetomidine ; enantiomers ; Chemistry ; Organic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently we synthesized a naphthalene analog of medetomidine, 4-[1-(1-naphthyl)ethyl]-1H-imidazole hydrochloride (1), and found it to be highly potent in adrenergic systems. The separation of optical isomers of this naphthalene analog was achieved by using the isomers of tartaric acid. The optical purities of the isomers were determined by HPLC using a chiral column. Using X-ray analysis the (+)-isomer was determined to have the S absolute configuration. It has been reported that the (+)-isomer of medetomidine (2) is the most potent enantiomer on α2-adrenergic receptors. There were both qualitative and quantitative differences in biological activities of the optical isomers of 1 in α1- and α2-adrenergic receptor systems of guinea pig ileum and human platelets. (+)-(S)-1, but not ( - )-(R)-1 was a selective agonist of α2-mediated responses in ileum whereas ( - )-(R)-1 was more potent than (+)-(S)-1 as an inhibitor of α2-mediated platelet aggregation. © 1992 Wiley-Liss, Inc.
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  • 6
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 10 (1993), S. 262-265 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In-process measurement of particle size and concentration distributions provides continuous analysis and quality control of a product stream. Elimination of sample handling and operator manipulation is now possible for most pneumatic flows using optical methods which are properly interfaced with the process stream.The EPCS (Ensemble Particle Concentration & Size) described in the following has been used to obtain detailed size distribution measurements in powder production facilities at two second intervals, and has been successfully used for automatic feedback control.
    Additional Material: 5 Ill.
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  • 7
    ISSN: 0933-5137
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Description / Table of Contents: Materials for Conversion of Solar EnergyMaterials for thermal, electrical and chemical conversion of solar energy are reviewed together with information on the physical basis common to all kinds of conversion. The natural and economical limits of the various techniques are mentioned.
    Notes: Es wird ein Überblick über die Werkstoffe gegeben, die für die thermische, elektrische und chemische Umwandlung der Sonnenstrahlung in Frage kommen, wobei die allen Umwandlungsarten gemeinsamen physikalischen Vorgänge besprochen werden. Die natürlichen und wirtschaftlichen Grenzen der verschiedenen Verfahren kommen zur Sprache.
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  • 8
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Particle and Particle Systems Characterization 12 (1995), S. 309-313 
    ISSN: 0934-0866
    Keywords: Chemistry ; Industrial Chemistry and Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In-process measurement of particle size and concentration distributions provides continuous analysis, quality control, and optimization of product yield. As process production rates continue to improve, the delay between laboratory analysis and process correction of the product stream becomes more significant and costly in many commercial applications. Elimination of sample handling and operator manipulation is now possible for most pneumatic flows using optical methods which are properly interfaced with the process stream. Insitec has developed such an instrument based on ensemble laser-diffraction that has been successfully applied to a wide range of research and industrial process applications.As part of the adaptation of instrumentation to the specific needs of different process applications, we have developed several different interface arrangements, including a direct inline system and an eductor bypass instrument. A specific window purge design has been developed and shown to operate for extended time periods (exceeding one month and more) without maintenance. To address the wide range of operating concentrations that occur in practice, a variable pathlength interface has been developed along with a deconvolution algorithm that corrects multiple scattering effects for light transmissions down to 20%. Distribution update rates are computed and displayed in less than 5 seconds. This methodology is described along with measurements in a non-steady pharmaceutical powder processing application. Results show uniform size measurement for ten-fold concentration variations. Real time measurements allowed diagnosis and correction of non-steady feed rates to a classifier-mill.
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  • 9
    Electronic Resource
    Electronic Resource
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 14 (1991), S. 401-406 
    ISSN: 0935-6304
    Keywords: Supercritical fluid chromatography, SFC ; Supercritical fluid extraction, SFE ; On-line combination ; SFC-MS ; Hamster feces ; Lipids ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Components of hamster feces ranging from low molecular weight fatty acids through the expected range of triglycerides have been eluted in a single SFC run with simultaneous pressure and temperature programming. Temperature programming from 140°C to 240°C was required to provide optimum conditions for separation of the fatty acids and to move the elution region of the sterol esters away from that of the triglycerides. Data from chemical ionization and electron impact mass spectrometry of compounds separated by SFC were used to confirm identities suggested by retention measurements and to provide tentative identities of unknown compounds.SFC with flame ionization detection was used to compare Soxhlet extraction, off-line supercritical fluid extraction (SFE), and on-line SFE of the feces. Although samples obtained by Soxhlet extraction and SFE produced very similar chromatograms, SFE required far less time and consumed much smaller quantities of organic solvent.
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  • 10
    Electronic Resource
    Electronic Resource
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Microcolumn Separations 5 (1993), S. 127-133 
    ISSN: 1040-7685
    Keywords: supercritical fluid chromatography ; retention mechanism ; selectivity tuning ; stationary phase swelling ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: When temperature programming is performed in supercritical fluid chromatography (SFC) under conditions where the solute-mobile phase interactions are approximately fixed, that is, with the use of constant mobile phase density, then positive temperature programs can be used. The results resemble those in temperature-programmed gas chromatography (GC) except that chromatograms are compressed and solutes elute at lower temperatures. For a given temperature-program rat, the extent of this compression effect is controlled by the (fixed) mobile phase density. When a methylsilicone stationary phase is used along with CO2 mobile phase, the compression occurs with little change in selectivity. However, with a biphenyl-substituted polysiloxane stationary phase, selectivity shifts occur for some solutes (vs. hydrocarbons) as the density is varied. The effect is even greater and affects more solutes when a cyanopropyl-substituted polysiloxane stationary phase is used.This selectivity behavior differs from the temperature-dependent selectivity behavior known in GC. In GC only the forces between solutes and the stationary phase are involved. But in SFC, mobile phase interactions with both the solutes and the stationary phase are also important. The large selectivity shifts we observe in SFC most likely arise because of stationary phase swelling by the mobile phase. This is a function of the temperature and mobile phase density (or pressure) and can be tuned without changing the composition of the mobile phase. It is possible to use either temperature or density to adjust or fine-tune selectivity between a pair of solutes while using the other parameter to adjust retention of the pair.These experiments further suggest that GC is not only a special case of SFC (where the solute-mobile phase interactions are essentially zero), but that SFC possesses an additional and extremely powerful selectivity adjustment mechanism not available in GC.
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