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  • Polymer and Materials Science  (34)
  • Inorganic Chemistry  (33)
  • General Chemistry  (19)
  • Biochemistry and Biotechnology  (7)
  • genetic engineering  (2)
  • Wiley-Blackwell  (93)
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  • Wiley-Blackwell  (93)
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  • 1
    Electronic Resource
    Electronic Resource
    Microstructural characterisation of nanocrystalline GaN prepared by detonations of gallium azides (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Advanced Materials for Optics and Electronics 8 (1998), S. 135-146 
    Details
    ISSN: 1057-9257
    Keywords: gallium nitride ; nanocrystallites ; detonation ; gallium azide ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: High quality nanoscale, phase-pure hexagonal gallium nitride (GaN) crystallites have been synthesized by the thermal induced detonation of molecular precursors of the type (R3N)Ga(N3)3 (R=CH3, C2H5, etc.). The method allows the control of the particle size regime from 2 to about 1000 nm. X-ray diffraction and Rietveld simulations revealed an anisotropic platelet-like shape of the particles. The obtained GaN material was as well characterized by transmission electron microscopy and electron diffraction, photoluminescence spectroscopy, SEM, IR, RAMAN, thermal gas effusion/mass spectrometry, thermal analysis, elemental analysis. Gas absorption measurements (BET method) showed a specific surface area of about 90 m2 · g-1. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Ionene elastomers from polytetramethylene oxide diamines and reactive dihalides. I. Effect of dihalide structure on polymerization and thermal reversibility (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1535-1547 
    Details
    ISSN: 0021-8995
    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
    Notes: The reaction of α,ω-bis(dimethylamino) polytetramethylene oxide with various dihalides provided a series of elastomeric ionenes. The influence of dihalide structure on the reaction was studied and a number of substituents were found which dramatically increased the rate of polymerization and ultimate molecular weights achieved. These ionene elastomers were thermoplastic and it was shown that in some cases this result was due at least in part to a depolymerization reaction via a dequaternization of the ammonium links. Again, structural features in the dihalide were important not only for the reverse reaction, but for the repolymerization to high molecular weight elastomer as well. An uncharged “analogue” was also prepared to address the feature of microphase separation and compared with the above ionene materials.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070380810
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  • 3
    Electronic Resource
    Electronic Resource
    Structure-property behavior of elastomeric segmented PTMO-ionene polymers. II (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 38 (1989), S. 1549-1565 
    Details
    ISSN: 0021-8995
    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
    Notes: A series of segmented ionene polymers based on the reaction of α,ω-bis(dimethyl amino)polytetramethylene oxide with various dihalide compounds were investigated with respect to their structure-property behavior. The placement of quaternary ammonium ions and halide counterions along the polymer chains was varied by changing the molecular weight of the PTMO soft segment and the structure of the dihalide linking agent. The techniques of dynamic mechanical spectroscopy, thermal analysis, small angle X-ray scattering, and stress-strain behavior analysis were applied. For the case when the PTMO soft segment was amorphous, the ambient temperature properties of these materials displayed low modulus, high strength, and high elongation elastomeric behavior with tensile strength enhanced by the strain-induced crystallization of the PTMO. A high level of phase separation existed between the dihalide component relative to the PTMO soft segment. Due to the Coulombic association of the ionene species, these materials displayed many similarities to the segmented urethane ionomers. In particular, distinct domain structure was noted by SAXS, whose dimensional scale was similar to the segmented urethanes. It was also shown, however, that the driving forces for the microphase separation was caused by favorable electrostatic or Coulombic interactions in contrast to segment-segment incompatibility features as in the segmented urethanes.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1989.070380811
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  • 4
    Electronic Resource
    Electronic Resource
    Metabolic engineering of Serratia marcescens with the bacterial hemoglobin gene: Alterations in fermentation pathways (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 640-646 
    Details
    ISSN: 0006-3592
    Keywords: Vitreoscilla hemoglobin ; metabolic engineering ; fermentation ; acetoin ; 2,3-butanediol ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Serratia marcescens was transformed with plasmid vector pUC8 or pUC8 containing the bacterial (Vitreoscilla) hemoglobin gene (vgb) on either a 2.3-kb fragment (pUC8:15) or 1.4-kb fragment (pUC8:16) of Vitreoscilla DNA. The vgb-bearing strains were compared with the pUC8 transformant and untransformed S. marcescens with respect to growth in Luria-Bertani (LB) broth supplemented with glucose or casein acid hydrolysate. Growth (on a viable cell basis) was similar to that in unsupplemented LB. Total acid excretion (as estimated by medium pH) was similar for all strains in both LB plus 2% casein acid hydrolysate and LB without additions. Acid excretion in LB plus 2% glucose was somewhat greater at up to 10 h in culture for the two vgb-bearing strains; from 10 to 26 h in culture, the pHs of these cultures continued to decrease (to 4.1-4.2), whereas those of the non-vgb-bearing strains returned to near the starting pH (7.4-7.8). Concomitantly, after 26 h of culture in LB plus 2% glucose, the non-vgb-bearing strains had produced about 15 times as much acetoin and about three to four times as much 2,3-butanediol as the vgb-bearing strains. In general, for all strains, much more acetoin and 2,3-butanediol were produced in LB plus 2% glucose than in unsupplemented LB. The exception was acetoin production by the strain bearing vgb on plasmid pUC8:15; after 26 h of culture in LB without supplementation it was between three and four times that of the other strains, and about 50% higher than its level in LB plus 2% glucose. When grown with the 2% casein acid hydrolysate supplement, the strain bearing vgb on plasmid pUC8:15 produced much more acetoin and 2,3-butanediol than the other strains after 26 hours in culture. The results confirm that vgb can significantly alter carbon metabolism and suggest that the use of vgb technology for directed metabolic engineering may be a complicated process, depending in part on medium composition. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:640-646, 1998.
    Additional Material: 4 Ill.
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  • 5
    Electronic Resource
    Electronic Resource
    Synthesis and excretion of α-amylase in vgb+ and vgb- recombinant escherichia coli: A comparative study (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 59 (1998), S. 673-678 
    Details
    ISSN: 0006-3592
    Keywords: microaerobic growth ; oxygen limitation ; oxygen uptake ; recombinant Escherichia coli ; synthesis and excretion/secretion of α-amylase ; two-stage culture ; Vitreoscilla hemoglobin ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Synthesis and excretion of α-amylase is investigated in batch cultures of Escherichia coli JM103[pMK57] (vgb-) and E. coli JM103[pMK79] (vgb+). While total production and excretion of α-amylase were promoted in Luria broth (LB) (excretion being as high as 87%), cell-mass-specific production of the enzyme was promoted in M9 in bioreactor cultures and in LB in shake flask cultures. Low aeration and agitation rates and presence of starch were conducive to α-amylase synthesis in E. coli JM103[pMK79]. Two-stage bioreactor operating strategies that will improve α-amylase production are proposed. The potential of these strategies is demonstrated via two-stage shake flask cultures. © 1998 John Wiley & Sons, Inc. Biotechnol Bioeng 59:673-678, 1998.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Swelling characteristics of gel fractions of formaldehyde-modified cotton cellulosesPresented in part at the Spring Meeting of The Fiber Society at Williamsburg, Va., May 1966. (1966)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 10 (1966), S. 1777-1786 
    Details
    ISSN: 0021-8995
    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
    Notes: A method for assessing extent of swelling of the gel fraction of formaldehyde-modified cottons, employing cupriethylenediamine hydroxide as the swelling agent, is described. Substantial differences in apparent specific volumes of swollen gel fractions are observed for cottons crosslinked by different processes to the same level of agent. The apparent crosslink density measured by the swelling of gel fraction increases with formaldehyde content of the cotton; at 0.20% formaldehyde the order of increasing crosslink density in the various processes of reaction is as follows: nonaqueous system (forms D and D′) 〈 aqueous system (forms W and W′) 〈swelling system (form F) 〈 vapor system (form V) 〈 bake-cure system (form C).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1966.070101115
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  • 7
    Electronic Resource
    Electronic Resource
    Moisture effects during cure of high-performance epoxy matrices (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 1717-1731 
    Details
    ISSN: 0021-8995
    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
    Notes: The effects of absorbed moisture on the cure reactions and subsequent solid-state properties of a high-performance epoxy system were investigated in this study. The resin systems investigated were a model system, TGDDM-Novalac-DDS-BF3:MEA (TNDB), and its commercial analog, Hercules 3501-6. The samples were exposed to three environments: a liquid water environment at 50°C; an 85% relative humidity vapor environment at 50°C; and an evacuated, desiccated atmosphere at 22°C. Differential scanning calorimetry (DSC) thermograms were obtained for the Hercules 3501-6 formulation as well as various compositions of the TNDB system for samples exposed to each of the three environments. Moisture was found to accelerate the cure especially for formulations exposed to the vapor environment. Dynamic mechanical experiments were also performed on cured, thin film samples. The “wet” samples were produced by adding water to the resin mixture prior to B-staging. The moisture was shown to increase the extent of reaction, but produce a slightly lower degree of crosslinking as related to the sample's glass transition. This has been attributed to chain-extension reactions, such as the hydroxyl-epoxide etherification reaction, which are favored in the presence of hydroxyl groups from water.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070300436
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  • 8
    Electronic Resource
    Electronic Resource
    Expression of β-lactamase by recombinant Escherichia coli strains containing plasmids of different sizes - effects of pH, phosphate, and dissolved oxygen (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 309-319 
    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 characteristics of growth and synthesis of plasmid-encoded protein were studied for strains of recombinant E. coli JM103 which carried the β-lactamase gene on plasmids of different sizes. The plasmids used included the vector pUC8 and its recombinant derivatives containing varying-sized inserts of Drosophila DNA (not expressed in E. coli). Luria broth (LB) and a minimal medium (M9) supplemented in some cases with additional inorganic phosphate were used as growth media. There was no evidence of segregational instability in these experiments, where no antibiotic selection pressure was employed. Responses of the recombinant strains to variations in environmental parameters including pH, phosphate concentration in the medium, and aeration rate were examined. While the cell growth rate in LB decreased with pH in the range 7.0-8.0, the bulk β-lactamase activity was maximized at an intermediate pH. The recombinant cell growth rate decreases with increasing plasmid size in the minimal medium, while such decrease is not significant when a rich medium such as LB is used. There is an intermediate plasmid size in the range studied (2.7-8.7 kb), at which β-lactamase activity is maximum. While reduction in aeration rate (which determines the dissolved oxygen level) is detrimental for cell growth, it is beneficial for β-lactamase synthesis. The bulk β-lactamase activity therefore exhibits a maximum with respect to aeration rate. Cell growth and β-lactamase production are affected in a similar manner by phosphate concentration in the minimal medium and therefore both are maximized at the same phosphate concentration. This investigation demonstrates clearly how the production of a recombinant plasmid-encoded protein can be maximized by proper manipulation of culture conditions and how it is affected by plasmid size.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340306
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  • 9
    Electronic Resource
    Electronic Resource
    Covalent immobilization of lipase in organic solvents (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 34 (1989), S. 942-950 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Lipase from Rhizopus sp. has been immobilized covalently on tresyl activated silica. Three different coupling media were evaluated: aqueous buffer, n-hexane, and a microemulsion based on n-hexane, aqueous buffer, and the nonionic surfactant triethylene glycol monododecyl ether. In addition, coupling via a very long, hydrophilic spacer arm, polyethylene glycol 1500 (PEG 1500), was compared with attachment to the silica via a short silane bridge only. The enzyme preparations were tested in hydrolysis and transesterification reactions. In the hydrolysis no marked differences in activity were found between the coupling media used. In the transesterification, on the other hand, the choice of immobilization medium had a very large effect on lipase activity, the preparation from microemulsion being the most active one. The use of the hydrophilic spacer had a large effect on activity in the hydrolysis reaction. Whereas direct coupling gave an activity of immobilized lipase of 26-34% of that of free enzyme, depending on the reaction medium, lipase bound via the spacer exhibited 56-67% activity. The latter values are considerably higher than previously reported in the literature for covalently immobilized lipase. The hydrophilic spacer had no effect on enzyme activity in the transesterification, however, a fact which is attributed to the hydrophobic medium of this reaction. The spacer is incompatible with the reaction medium and will, therefore, adsorb on the particles rather than stretch out into the bulk phase. The stability of the bound lipase was extremely good, no loss in activity being observed after a period of three weeks in aqueous solution of 37°C.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260340709
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  • 10
    Electronic Resource
    Electronic Resource
    Plasmid stability and α-amylase production in batch and continuous cultures of Bacillus subtilis TN106[pAT5] (1989)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 33 (1989), S. 1010-1020 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Cell growth and enzyme (α-amylase) production characteristics of Bacillus subtilis TN106 containing the recombinant plasmid pAT5 are investigated in batch and continuous cultures using a defined medium with glucose as the limiting nutrient. The batch culture studies demonstrate that the recombinant plasmid, reported earlier1 to be stably maintained in the host, suffers from segregational and structural instabilities. The structural instability of this strain occurred during culture storage and can be eliminated in bioreactor experiments by using a modified inoculum preparation procedure. Such elimination allows an unbiased investigation of segregational instability via continuous culture studies. Such studies conducted with this fast growing microorganism, in the absence of antibiotic selection pressure, indicate a very efficient glucose utilization (very low residual glucose concentrations) over a wide range of dilution rates (0.16 h-1 - 0.94 h-1). The nearly time-invariant and low residual glucose concentrations at each such dilution rate enable convenient estimation of growth parameters of the host and recombinant cells and frequency of segregational instability from transients in the resulting mixed cultures. The specific α-amylase activity exhibits an inverse relationship to the specific growth rate of recombinant cells. The growth of recombinant cells is not affected by the presence of antibiotic (kanamycin). The growth advantage of host cells over recombinant cells diminishes with increasing dilution rate.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260330810
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