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  • Chemistry  (35)
  • Biochemistry and Biotechnology  (7)
  • Meteorology and Climatology
  • Spacecraft Design, Testing and Performance
  • 1990-1994  (39)
  • 1
    Electronic Resource
    Electronic Resource
    Rank-order analysis for robust multiresponse, multiblock comparisons: Evaluation of herbicide interactions (1991)
    New York, NY : Wiley-Blackwell
    Journal of Chemometrics 5 (1991), S. 503-521 
    Details
    ISSN: 0886-9383
    Keywords: Antagonism ; Bounded ordinal scale ; Herbicide interaction ; Inter block comparisons ; Non-parametric ; Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Studies of interactions among bioactive compounds are often difficult to interpret unambiguously. A priori assumptions about the nature of such interactions can seriously distort analysis of the data. By applying a rank order analysis appropriate to the naturally ordinal scale of response to xenobiotic insult, several co-herbicides were successfully identified from among numerous candidates in an experiment involving multiple blocks, rates and species. Moreover, underlying herbicide interactions were substantiated and identified which were not apparent by more traditional parametric analysis.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cem.1180050604
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  • 2
    Electronic Resource
    Electronic Resource
    Plasma copolymerization of ethylene and tetrafluoroethylene (1992)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 30 (1992), S. 2683-2692 
    Details
    ISSN: 0887-624X
    Keywords: plasma copolymerization ; ethylene ; tetrafluoroethylene ; infrared spectroscopy ; x-ray photoelectron spectroscopy ; copolymer deposition rates ; mechanism ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The plasma copolymerization of ethylene (ET) and tetrafluoroethylene (TFE) was investigated by means of IR and XPS analyses. The deposition rates for plasma ET/TFE copolymers, when plotted versus mol % TFE in the feed gas, gave a concave-downward curve situated above the straight-line joining the deposition rates for the respective plasma polymers, PPET and PPTFE, with the maximum rate at ∼ 70-80 mol % TFE. This result, coupled with the finding that normalized absorbances of the C=H and C=F IR bands of ET/TFE copolymers had maxima at ∼ 20 and 80 mol % TFE, respectively, indicated a positive interaction between ET and TFE such that each monomer “sensitized” the plasma copolymerization of the other. As analyzed by XPS, CF groups dominated over CF2 and CF3 groups at 5-70 mol % TFE, but at ≥ 80 mol % TFE, these moieties approached the relative proportions in PPTFE (CF2 〉 CF3 〉 CF). The plot of F/C ratio versus mol % TFE was concave-upward and situated below the hypothetical straight-line plot representing noninteracting, independent polymerization of ET and TFE, while the % F in the plasma copolymers was linear with mol % TFE. The F1s mean binding energies of the ET/TFE plasma copolymers, which increased monotonically with % F, were consistently higher than those for several commercial polymers of fluorinated olefins at comparable values of % F. This result suggested clustering of CFn moieties in the plasma copolymers or the presence of F atoms in highly fluorinated environments. © 1992 John Wiley & Sons, Inc.
    Additional Material: 9 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1992.080301303
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  • 3
    Electronic Resource
    Electronic Resource
    Ester derivatives of α-hydroxymethylacrylates: Itaconate isomers giving high molecular weight polymers (1994)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part A: Polymer Chemistry 32 (1994), S. 2937-2945 
    Details
    ISSN: 0887-624X
    Keywords: phase transfer ; α-hydroxymethylacrylates ; substituted acrylates ; methacrylates ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: New ester derivatives of ethyl α-hydroxymethylacrylate were synthesized using acid chlorides (traditional solution reactions), sodium salts of acids (with phase transfer catalysis), and trifluoroacetic anhydride (trifluoroacetate). The interfacial process gave high yields of clean products under very mild conditions. Derivatives obtained include the formate, acetate, hexanoate, stearate, benzoate, trifluoroacetate, and adamantanoate. Bulk polymerizations with 2,2′-azobis (isobutyronitrile) gave high molecular weight polymers with intrinsic viscosities of over 2 dL/g and molecular weights of several million [based on size-exclusion chromatography (SEC) comparison to polystyrene standards]. These high molecular weights were the result of autoacceleration in the bulk as shown by monitoring molecular weight with respect to conversion. Solution polymerization in benzene gave more typical polymer, e.g., the acetate derivative showed an SEC molecular weight of 52,000. Glass transition temperatures for the n-alkyl esters decreased from the formate (77°C) to the hexanoate (15°C); the stearate showed a side-chain melting point of 40°C but no Tg. Glass transitions were observed for the trifluoroacetate, benzoate, and adamantanoate polymers at 69, 130, and 214°C, respectively. Solution 13C-NMR showed evidence of tacticity information for the formate and acetate derivatives with appaent preference for syndiotactic polymer formation similar to that of methyl methacrylate. FTIR and solid-state 13C-NMR analysis gave spectra with functional group peaks and chemical shift values expected based on composition. The stearate monomer and polymer gave solid-state 13C chemical shifts of 34 and 33 ppm, respectively, for the central CH2 units consistent with monoclinic and orthorhombic crystal packing. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pola.1994.080321515
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  • 4
    Electronic Resource
    Electronic Resource
    Quantitative assay for low levels of L-threonine in amino acid fermentation broths (1990)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 35 (1990), S. 1169-1173 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260351115
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  • 5
    Electronic Resource
    Electronic Resource
    Effect of agitational shear on growth and protease production by Thermomonospora fusca (1991)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 37 (1991), S. 371-374 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260370411
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  • 6
    Electronic Resource
    Electronic Resource
    Metabolic characterization of a L-lysine-producing strain by continuous culture (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 39 (1992), S. 565-574 
    Details
    ISSN: 0006-3592
    Keywords: Corynebacterium glutamicum ; continuous L-lysine fermentation ; flux analysis ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Continuous culture experiments with the L-producer, Corynebacterium glutamicum, were carried out to characterize the effect of specific growth rate on fermentation yields, specific rates, productivities, and fluxes through the primary metabolism. The specific productivity of L-lysine exhibited a maximum with respect to specific growth rate, with an initial growth-associated behavior up to specific growth rates of about 0.1 h-1, and a constant specific productivity for specific growth rates in the range of about 0.1 to 0.2 h-1. The productivity dropped at specific growth rates larger than about 0.2 h-1. The yield of L-lysine on glucose increased approximately linearly with decreasing specific growth rate over the entire range studied, as did the respiratory quotient. A direct relationship was established between the culture respiratory quotient and the L-lysine yield. By explicitly accounting for glucose used for biomass synthesis, it was shown that the strain synthesizes L-lysine with an intrinsic yield, or efficiency, of about 0.41 mol L-lysine/mol glucose, compared with the theoretical yield of 0.75 mol/mol. Metabolic flux modeling based on the continuous culture data suggests that the production of ATP is not likely to be a limiting factor in L-lysine production, and that a high TCA cycle activity, coupled with a tightly controlled split of metabolite flow at the PEP node, is likely the cause of the large discrepancy between theoretical and actual yields in L-lysine fermentations.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260390512
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  • 7
    Electronic Resource
    Electronic Resource
    Production of somatic embryos in a helical ribbon impeller bioreactor (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 930-943 
    Details
    ISSN: 0006-3592
    Keywords: Eschscholtzia californica ; embryogenesis ; somatic embryos ; bioreactor ; macronutrients ; kinetics ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Embryogenic cultures of a transformed Eschscholtzia californica cell line were carried out in a 11-L helical ribbon impeller bioreactor operated under various conditions to evaluate the performance of this equipment for somatic embryo (SE) production. All bioreactor cultures produced SE suspensions with maximum concentrations at least comparable to those obtained from flask control cultures (∼8-13 SE · mL-;1). However, an increase of the mixingspeed, from 60 to 100 rpm, and low sparging rate (∼0.05 VVM, kL a ∼ 6.1 h-;1) for dissolved oxygen concentration (DO) control yielded poorer quality embryogenic cultures. The negative effects on SE production were attributed mainly to the low but excessive shear experienced by the embryogenic cells and/or embryoforming aggregates. High DO (∼60% of air saturation) conditions favored undifferentrated biomass production and high nutrient uptake rates at the expense of the slower SE differentiation process in both flask and bioreactor cultures. Too low DO (-5-10%) inhibited biomass and SE production. The best production of SE (∼44 SE · mL-1 or ∼757 SE · g dw-1 · d-1) was achieved by operating the bioreactor at 60 rpm while controlling DO at ∼20%by surface oxygenation only (0.05 VVM, kL a ∼ 1.4 h-;1). This production was found to be a biomass production/growth-associated process and was mainly limited by the availability of extracellular phosphate, magnesium, nitrogen salts, and carbohydrates. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440809
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  • 8
    Electronic Resource
    Electronic Resource
    Effect of polymeric adsorbents on the production of sanguinarine by Papaver somniferum cell cultures (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 971-977 
    Details
    ISSN: 0006-3592
    Keywords: adsorption ; benzophenanthridine alkaloid ; sanguinarine ; plant cells ; suspension culture ; elicitation ; Papaver somniferum ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The suitability of adsorbent polymeric resins, Amberlite XAD-4 and XAD-7 (Rohm and Hass, Inc.), was investigated for the accumulation of sanguinarine from Papaver somniferum cell cultures. The adsorption and desorption of sanguinarine from aqueous solution was most effective with XAD-7. In addition to sanguinarine, the resins were found to absorb growth regulators and vitamins from the culture medium. Growth inhibition was overcome by delaying for ∼4 days resin addition after cell inoculation in fresh medium. Resin addition (5% wt/vol) to actively growing uneclicited cultures led to increases in sanguinarine production and release of 30% to 40% and 60%, respectively. The addition of resins to elicited cultures led to increases in alkaloid production of up to 50% to 85% with similar increases in alkaloid release as observed for nonelicited cells. Overall yield of sanguinarine increased from 21 mg · g biomass dry weight-1 (dw) for elicited cultures to more than 39 mg · gdw-1 when elicitation was combined with resin addition. Higher quantities of resin (10% to 20% wt/vol) increased marginally the release of sanguinarine into the medium, and on the resin, up to 85% of total production. The use of resin appears promesing for the development of a bioprocess for sanguinarine production by cultured plant cells. © 1992 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400813
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  • 9
    Electronic Resource
    Electronic Resource
    Culture instability of auxotrophic amino acid producers (1992)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 40 (1992), S. 75-85 
    Details
    ISSN: 0006-3592
    Keywords: L-lysine fermentation ; auxotrophic reversion ; continuous culture instability ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The long-term dynamic characteristics of the L-lysine producer Corynebcterium glutamicum in continuous culture were studied over a range of specific growth rates. The double-auxotroph parent strain was found to be susceptible to a back mutation, or reversion, which negated the regulatory bypass that allows this strain to accumulate L-lysine in culture but also gives rise to a L-threonine auxotrophic requirement. Consequently, the revertant cells no longer over-produced L-lysine, nor were they limited in their growth by the low levels of L-threonine in the medium. All continuous culture experiments were enventually taken over by these revertants. The instability of the culture was found to be primarily due to the growth rate differential between the two competing populations, the (productive) parent auxotrophs and the (nonproductive) revertants. A deterministic mathematical model of the culture dynamics, incoroporating two limiting-substrate balances, satisfactorily described the takeover profiles. A linear stability analysis of the model equations identified that although long-term culture demise is inevitable, the dimensionless ratio of the two limiting substrates controls the rate of takeover by nonproductive cells. The anslysis further demonstrated the importance of proper medium design in delaying the onset of takeover in cultures of this double-auxotroph strain. The theoretical medium design criterion was then confirmed experimentally by the stabilization of a fed-batch culture against revertant takeover for an extended fermentation time.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260400112
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  • 10
    Electronic Resource
    Electronic Resource
    Relaxation dynamics of carbon dioxide sorbed in poly (dimethyl siloxane) rubber (1990)
    Bognor Regis [u.a.] : Wiley-Blackwell
    Journal of Polymer Science Part B: Polymer Physics 28 (1990), S. 1737-1753 
    Details
    ISSN: 0887-6266
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: We have probed the dynamics of 13CO2 molecules sorbed in poly (dimethyl siloxane) rubber by nuclear magnetic resonance (NMR) relaxation. The spin-lattice and spin-spin relaxation times as well as nuclear Overhauser enhancements were determined as functions of temperature at three magnetic field strengths. The relaxation mechanisms found to be important are intermolecular dipole-dipole relaxation and spin rotation relaxation with a minor contribution from chemical shift anisotropy relaxation. Our analysis shows that the assumption of a single correlation time for each motional mechanism is inconsistent with the NOE data and spin-spin relaxation times. However, if a distribution of correlation times is assumed, one can interpret all of the experimental data in a reasonable manner. We have quantitatively elucidated the spin relaxation mechanisms and determined the parameters which characterize the distribution times for 13CO2 Collisional motions, rotational motions, and translational motions in the silicone rubber. A fractional exponential correlation function of the Williams-Watts type with a fractional exponent of 0.58 is used in our description of the 13CO2 dynamics. This exponent is typical of the distribution of time scales associated with segmental motion in polymeric rubbers. The broad distribution needed to describe the data has implications for the coupling of diffusion to segmental motion and for the relationship between macroscopic permeability and the molecular level character of diffusion.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/polb.1990.090281007
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