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  • 1
    Electronic Resource
    Electronic Resource
    Synthesis and chemo-physical properties of hydrogels (1992)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 196 (1992), S. 49-61 
    Details
    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: Hydrogele wurden aus methylmethacrylat (MMA) and N-Vinyl-2-pyrrolidon (NVP) mit 1,2,2-Trimethylolpropantrimethacrylat (TPTA) als Vernetzungsmittel hergestellt. Die Terplymerisation wurden mittels UV-strahlung (365 nm) initiiert, wobei kleine Mengen an Diethoxycetophenon (DEAP) als Photosensibilisator sowie Triethanolamin(TEA)als Beschleuniger und Verdünner verwendet wurden. Die Hydrogele wurden durch Messung des Wasserrückhaltevermögens, der Sauerstodiffusions- und permitionskoeffizienten, der mechanischen Eigenschaften und der Lichtdurchlässigkeit charakterisiert. Dabei zeigte sich, daß die Hydrogele bis zu 80 Gew.-% Wasser aufnehmen können, wobei mit steigendem Wassergtehalt deren mechanische Festigkeit drastisch sinkt. Der Ssuerstoffdiffusionskoeffizient der gequollenen Hydrogele beträgt 10-6 cm2s-1, der Sauerstoffpermeationskoeffizient 1013 cm2s-1Pa-1, und die Lichtdurchlässigkeit liegt im Bereich von 500 bis 700 nm bei über 90%.
    Notes: Hydrogels are synthesized from methyl methacrylate (MMA) and N-vinyl-2-pyrrolidone (NVP) with 1,1,1-trimethylol propane trimethacrylate (TPTA) as a crosslinking agent. It was polymerized under UV radiation (365nm) with a small amount of photosensitizer, diethoxy acetophenone (DEAP), acclerator and diluent, triethanol amine (TEA). The hydrogels were characterized by measuring the water retention, dissolved oxygen diffusivity and permeability, mechanical strength, and light transparency. The hydrogels can retain water up to 80 wt.-% and the mechanical strenght is weakened as the water content is increased in the gel. The dissolved oxygen diffusivity and permeability in the swelling hydrogels are determined to be 10-6 cm2/sec and 1013 cm2s-1 Pa-1, respectively. The light transparency is over 90% in the wave lenght ranging from 500 to 700 nm.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1992.051960104
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  • 2
    Electronic Resource
    Electronic Resource
    NMR three-dimensional solution structure of the serine protease inhibitor cyclotheonamide A (1997)
    New York : Wiley-Blackwell
    Biopolymers 41 (1997), S. 349-358 
    Details
    ISSN: 0006-3525
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The nmr solution conformation of cyclotheonamide A (CtA) was determined in aqueous media. The data produced 15 distance and 10 torsional constraints which were used to generate conformations using restrained simulated annealing (SA) and distance geometry/simulated annealing (DG/SA) calculations. Two different calculation protocols were performed to ensure proper sampling of conformational space and even though the torsional restraints were input differently, both calculation methods yielded the same conformation of CtA. In the structure calculations, all solutions of the Karplus equation were sampled simultaneously using the restrained SA protocol and large ranges were used for the dihedral restraints in the DG/SA protocol because all solutions to the Karplus equation could not be sampled simultaneously. The solution conformation was also compared to the solid state x-ray conformations of CtA bound to thrombin and trypsin. The conformation of the residues important for active site binding (d-Phe, h-Arg, and Pro) are nearly identical in aqueous solution and solid state with largest differences at the a-Ala and v-Tyr residues. CtA appears to be preordered in structure and does not undergo a significant conformational change upon binding to the enzyme active site. © 1997 John Wiley & Sons, Inc.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    Crystal structure of fibers from a novel rigid-rod aromatic polyamide containing a pyrimidine moiety (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 2993-3004 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Fibers of a novel rigid-rod polyamide containing a 1:1 ratio of phenylene:pyrimidine moieties have been produced and evaluated. The lyotropic liquid-crystalline behavior of the polymer and the spinnability of the nematic dope were established. The as-spun fibers exhibit low degrees of orientation and crystallinity. Heat treatment of the dry fibers resulted in crystallinities as high as 45% in coexistence with an amorphous phase component. Evaluation of the crystal structure by wide-angle X-ray diffraction suggests a pseudo-orthorhombic crystal cell with lattice dimensions (a; b; c) of (7,3 Å; 5,1 Å; 12,8 Å) and containing two repeating units per unit cell.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021921215
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  • 4
    Electronic Resource
    Electronic Resource
    Estimation of parameters in population models for Schizosaccharomyces pombe from chemostat data (1972)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 14 (1972), S. 915-938 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The integro-differential growth model of Eakman, Fredriekson, and Tsuehiya has been employed to fit cell size distribution data for Schizosaccharomyces pombe grown in a chemostat under severe product inhibition by ethanol. The distributions were obtained with a Coulter aperture and an electronic system patterned after that of Harvey and Marr. Four parameters - mean cell division size, cell division size standard deviation, daughter cell size standard deviation, and a growth rate coefficient - were calculated for models where the cell growth rate was inversely proportional to size, constant, and proportional to size. A fourth model, one where sigmoidal growth behavior was simulated by two linear growth segments, was also investigated. Linear and sigmoidal models fit the distribution data best. While the mean cell division size remained relatively constant at all growth rates, standard deviation of division size distribution increased with increasing holding times. Standard deviation of the daughter size distribution remained small at all dilution rates. Unlike previous findings with other organisms, the average cell size of Schizosaccharomyces pobme increased at low growth rates.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260140605
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  • 5
    Electronic Resource
    Electronic Resource
    Cell death in bioreactors: A role for apoptosis (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 720-726 
    Details
    ISSN: 0006-3592
    Keywords: cell death ; apoptosis ; hybridoma cells ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The incidence of apoptotic and necrotic cell death was compared in CHO, SF9 insect cells and murine plasmacytoma (J558L) and hybridoma (TB/C3) cells during in vitro cultivation in batch cultures. Acridine orange staining and fluorescence microscopy enabled the visualization of a classic morphological feature of apoptotic cell, the presence of condensed and/or fragmented chromatin. DNA gel electrophoresis was employed to show an additional characteristic of the process, the endonuclease-mediated fragmentation of DNA into multiples of 180 base pairs. The levels of apoptosis at the end of batch cultures of plasmacytoma and hybridoma cell lines were found to be 60% and 90% of total dead cells, respectively. However, employing the above-mentioned techniques, the biochemical and morphological features of apoptosis were not found in CHO and SF9 insect cells. Some factors affecting the induction of apoptosis during the batch culture of the hybridoma and plasmacytoma cell lines were identified. The most effective inducer was found to be glutamine limitation, followed by (in order of importance) serum limitation, glucose limitation, and ammonia toxicity. Blockage of the cell cycle of the plasmacytoma and hybridoma cells using thymidine resulted in the induction of apoptosis. This has important implications for the development of cell culture processes that minimize cell division and thereby increase specific productivity. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440608
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  • 6
    Electronic Resource
    Electronic Resource
    Mass transfer with chemical reaction in a threehyphen;phase foam-slurry reactor (1990)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 36 (1990), S. 117-125 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Studies on mass transfer coupled with chemical reaction were conducted in a gas-liquid-solid foam bed contactor under a variety of operating conditions in order to establish the controlling parameters for such a contacting system. Analytical equations were derived in order to predict the influence of solids dissolution on the specific rate of absorption in the stable foam stage of a three-phase foam-slurry reactor. Experimental investigations on the absorption of carbon dioxide in the presence of an aqueous foam-slurry containing calcium hydroxide particles were carried out in order to verify the theoretical model. Results indicate that the gas-liquid interfacial area and gas flow rate strongly affected the rate of mass transfer, while solids holdup affected mass transfer rates only moderately over the range of solids holdup studied. A comparison with conventional chemical reactor configurations (e.g., bubble column, CSTR) was made to demonstrate the gas-liquid-solid system, for which this novel reactor might be employed. Foam stability enhancement, due to the presence of solid particles, was not observed.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690360114
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  • 7
    Electronic Resource
    Electronic Resource
    Conformational theory of large molecules: The rotational isomeric state model in macromolecular systems. By Wayne L. Mattice and Ulrich W. Suter, Wiley, New York, 1994, 449 pp. $54.95 (1996)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 42 (1996), S. 1199-1200 
    Details
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690420440
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  • 8
    Electronic Resource
    Electronic Resource
    Coupled solid phase extraction-supercritical fluid extraction-on-line gas chromatography of explosives from water (1993)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 16 (1993), S. 473-478 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction (SFE) ; Solid phase extraction (SPE) ; On-line analysis ; Gas Chromatography ; Explosives ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A method has been developed for the quantitative extraction of nitrotoluenes (2,3-dinitrotoluene, 2,4-dinitrotoluene and trinitrotolugene) from water using a BakerbondTM phenyl sorbent. The average solid phase extraction recoveries for spiked standards ranged from 80 to 95 percent for reagent water and 52 to 95 percent from well and surface water in the low ppb and ppt levels. After the nitrotoluenes had been trapped on the solid sorbent they were quantitatively eluted using SFE. Adding toluene to the extraction cell increased the rate of extraction, but did not improve analyte recovery versus unmodified CO2. The extracts were analyzed off-line with GC-ECD using an internal standard. Extraction losses were due to analyte breakthrough, and not from poor SFE recoveries. This demonstrates that supercritical fluid extraction is a suitable elution technique for analytes trapped on solid phase extraction sorbents.Also, a method for the direct on-line coupling of SPE to GC, using SFE, has been developed and evaluated. Supercritical CO2 is ideal for directly coupling SPE to GC, since carbon dioxide is a gas under ambient conditions. One potential problem of on-line SPE-SFE-GC is the presence of residual water trapped on the active sites of the Bakerbond13 phenyl sorbent. This problem was dealt with by using a split interface previously described by Hawthorne. From the results of this study, the relative standard deviation of the on-line SPE-SFE-GC interface was determined to be between 4 and 10 percent. In addition, there was no significant difference in the precision of the method with or without the use of an internal standard. A calibration curve was also constructed (r2 = 0.995) from spiked controls, demonstrating that the method is quantitative.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240160806
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  • 9
    Electronic Resource
    Electronic Resource
    Characterization of Semtex by supercritical fluid extraction and off-line GC-ECD and GC-MS (1992)
    Weinheim : Wiley-Blackwell
    Journal of High Resolution Chromatography 15 (1992), S. 102-104 
    Details
    ISSN: 0935-6304
    Keywords: Supercritical fluid extraction ; GC-MSD ; GC-ECD ; Semtex ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Researchers using electron capture for the detection of explosive vapors currently claim the ability to detect the presence of RDX in Semtex - a plastic explosive comprising hexahydro-1,3,5-trinitro-1,3,5-triazane (RDX) in a matrix of styrene-butadiene copolymer and hydrocarbon oil. The vapor pressure of RDX at room temperature is 0.006 ppb, and therefore well below the detection limit of electron capture detection (ECD). The positive response generated by ECD is, consequently, not from the presence of RDX, but from some other component.This paper describes the extraction and identification of several compounds in Semtex, along with the determination of which is responsible for the positive response of an ECD-based detector.From the results of supercritical fluid extraction and off-line gas chromatography combined with electron capture and mass spectrometric detection, it has been concluded that ethylene glycol dinitrate is the component responsible for the positive ECD response. This conclusion is based on the requirements necessary for ECD detection, i.e. electronegativity, and a sufficient vapor pressure. The other compounds present were eliminated as possible choices because they either can not be detected by an ECD or do not have sufficient vapor pressure under ambient conditions.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jhrc.1240150210
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  • 10
    Electronic Resource
    Electronic Resource
    Monte Carlo simulations of a liquid crystal copolymer in the solid state (1998)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 36 (1998), S. 727-741 
    Details
    ISSN: 0887-6266
    Keywords: liquid crystal polymer ; aromatic polyester ; molecular modeling ; Monte Carlo ; Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The condensed phase of the alternating copolyester of p-hydroxybenzoic acid (HBA) and 2-hydroxy-6-naphthoic acid (HNA) is investigated by studying the room temperature packing arrangement of the copolymer chains. A molecular modeling methodology is employed with a Monte Carlo sampling of the configurational phase space. Realistic poly(HBA-alt-HNA) polymer chains are represented by an explicit atom representation of the HBA/HNA dimers. States are sampled from the NVT ensemble using a sampling scheme consisting of (1) valence and torsional variations, (2) rigid body rotations of the chain about the chain axis, and (3) rigid body translations of the chain. The effect of chain packing on the conformation of chains, as well as the relative intra- and intermolecular orientations of aromatic rings, is investigated. Correlation of chain positioning along the chain axis is dominated by aromatic rings maintaining a center-to-center plane of registry. These layers of aromatic units pack with a preference for edge-to-face orientations in a herringbone-type pattern and have an intermolecular ring angle between the pairs of aromatic rings in the unit cell that is ca. 68°. The aromatic rings, on average, are rotated 38° out from the b-c plane. The phenylene rings of these copolyesters are less restricted in their relative orientation in comparison to the naphthalene rings. Intramolecular orientational probability density distributions indicate a preference for staggering the successive aromatic rings along the chain, with a staggering angle of ca. 66°. © 1998 John Wiley & Sons, Inc. J Polym Sci B: Polym Phys 36: 727-741, 1998
    Additional Material: 14 Ill.
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