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  • Chemistry  (18)
  • SPACE COMMUNICATIONS, SPACECRAFT COMMUNICATIONS, COMMAND AND TRACKING  (3)
  • Lunar and Planetary Science and Exploration  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Improvement of product yields by temperature-shifting of Escherichia coli cultures containing plasmid pOU140 (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 513-519 
    Details
    ISSN: 0006-3592
    Keywords: Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Temperature shifting was investigated as a means of improving cloned-gene product yields form a recombinant Escherichia coli containing the temperature-sensitive plasmid, pOU 140. In a series of shaker flask fermentations recombinant cells were thermally induced for different time periods. The growth, stability, and plasmid product levels were followed, and the results indicate the existence of an induction time period that maximizes product yield. A sustained thermal induction results in recombinant cell death and instability, while exposure to a runaway temperature for minimal time periods does not give sufficiently high product yields. At intermediate cycling times, however, the recombinant cells remain stable, and the plasmid replication region is activated, resulting in higher product yields.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260290416
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  • 2
    Electronic Resource
    Electronic Resource
    “Tunable” diffusion of D2O in CO2-swollen poly(methyl methacrylate) films (1997)
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 43 (1997), S. 1838-1848 
    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: Opportunities exist to exploit the unique properties of carbon dioxide to process polymers for advanced applications. The diffusion of deuterated water in poly(methyl methacrylate) films swollen by carbon dioxide at 35°C over the pressure range 0 to 90 bar (corresponding density range: 0.0 to 0.66 g/cm3) was measured using in situ FTIR spectroscopy. The mechanism and time scale of the diffusion of deuterated water in PMMA are easily controlled by manipulation of the applied CO2 density. The enhancement of mass transport rate is consistent with the degree of plasticization of the polymer due to the absorption of carbon dioxide.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/aic.690430719
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  • 3
    Electronic Resource
    Electronic Resource
    Growth kinetics of Eschericia coli containing temperature-sensitive plasmid pOU140 (1987)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 29 (1987), S. 1164-1172 
    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 growth dynamics of Escherichia coli with the temperature-sensitive plasmid, pOU140, were examined. Recombinant cells exhibited nearly identical kinetic behavior to host cells at low culture temperatures and low copy numbers. However, at higher temperatures, in which the copy number was significantly increased, the recombinant cells showed decreased stability along with lower growth rates and substrate yields as compared to the host. Furthermore, the production of a constitutive cloned-gene protein was shown to increase with temperature in an Arrhenius fashion when culture temperature was varied between 38 and 42°C. These results suggest that temperature can be used to quantitatively control the production of a desirable plasmid-coded gene product.
    Additional Material: 16 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260290918
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  • 4
    Electronic Resource
    Electronic Resource
    Experimental and theoretical study of the injection molding of thermoplastic materials (1988)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 28 (1988), S. 460-468 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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: Most of the commercially available computation programs for injection molding use restrictive assumptions which lead to simple mechanical and thermal equations. These computations are generally sufficient to predict the flow distribution in the mold but the pressure and temperature distributions are not precise. Our aim was first to model very accurately the filling stage of several molds of elementary geometries. For this purpose, a two-dimensional model has been built which solves at each time step the finite difference forms of the continuity, momentum, and energy equations. A refined grid is used near the mold walls to take into account the great temperature gradients. These models have been validated by comparing the pressure field with experimental measurements. The precision of the model is better than 15 percent for several mold geometries and several injection conditions. In a second step, molds of complex geometries have been analyzed by assembling elementary geometries. The flow distribution at the branching between several geometries has been studied with special attention. These computations have been compared with short shots and pressure measurements in a four rectangular cavities tool and in a box shaped cavity tool. Experimental and theoretical results are in good agreement.
    Additional Material: 19 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760280709
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  • 5
    Electronic Resource
    Electronic Resource
    Injection molding of unsaturated polyester compounds (1992)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 32 (1992), S. 1440-1450 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 bulk-molding compound made of unsaturated polyester resin, glass fiber, calcium carbonate fillers, and low profile additives is studied. The viscosity of the compound in the absence of cure reaction is measured by capillary rheometry. The compound exhibits a shear-thinning behavior. Injection molding in a rectangular plaque equipped with pressure transducers shows that the crosslinking reaction can begin during mold filling for low flow rate or high mold temperature. Fiber orientation in the plaque is complex as the reinforcement appears under two aspects, bundles or filaments. Their lengths and orientations are different. A layered structure throughout the thickness is observed at the mold entrance, whereas the orientation becomes progressively unidirectional in the plaque. Two fiber-free layers near the the mold walls are observed. A numerical simulation of mold filling assuming inelastic non-Newtonian kinetic dependent behavior is presented. The results agree well with pressure measurements. A simplified decoupled fiber motion calculation is finally proposed. A qualitative explanation of the basic phenomena which induce fiber orientation is presented.
    Additional Material: 20 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760321907
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  • 6
    Electronic Resource
    Electronic Resource
    An experimental study of the influence of carbon black on the rheological properties of a polystyrene melt (1979)
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 19 (1979), S. 617-624 
    Details
    ISSN: 0032-3888
    Keywords: Chemistry ; Chemical Engineering
    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 broad range of experiments on carbon black filled polystyrene melts shows the reinforcing effect of the filler. This study represents one of the most extensive investigations of a series of highly filled polymer melts. Stress relaxation and dynamic experiments characterize the small strain behavior while the steady state shear viscosity, normal stresses, and elongational flow experiments describe the large strain deformation rate response. Extrudate swell and unconstrained shrinkage of extrudates are also measured. Highly filled systems exhibit yield values. This is seen in the dynamic experiments and in the shear and elongational viscosities. Viscosity does not level off at finite values with decreasing deformation rate but continues to increase in an approximately inverse manner. This corresponds to yield values of order 5 × 105 dynes/cm2. The storage modulus also does not tend to zero at low frequencies. The small strain dynamic properties and stress relaxation results suggest high memories for small strain experiments. Txtrudate swell values are however small and the systems exhibit minimal delayed recovery. The implications of this are considered. Generally it is argued that at volume loadings between 10 and 20 percent, the system takes on the characteristics of a gel and the response is similar to that of a Schwedoff body.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pen.760190905
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  • 7
    Electronic Resource
    Electronic Resource
    The donor atom-π interaction of sulfur with flavin. A density functional investigation (1998)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 9 (1998), S. 605-606 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Thiols and sulfides interact strongly with electron-deficient aromatic systems such as flavins. Using density functional methodology, we have shown that this interaction is electrostatic in nature, with very little polarization of the sulfur electron cloud. © 1998 John Wiley & Sons, Inc. Heteroatom Chem 9: 605-606, 1998
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Confirmation of drugs of abuse in urine drug screens by direct exposure probe mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 263-265 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: A direct exposure probe (DEP) mass spectometric method was developed to confirm the presence of cocaine (C), phencyclidine (P), benzoyl ecognine (BE) and 11-norcarboxy tetrahydrocannabinol (11-nor-c-THC) in previously screened urine specimens. Essentially, a urine sample is lyophilized overnight and reconstituted in 30 μl of a 3 : 1 mixture of ethyl acetate: methnol. One microliter is placed on a rhenium filament and left to air dry. The specimen was analyzed by negative ion chemical ionization DEP using ammonia as reagent gas at 0.20 Torr with an ion source temperature of 100°C. An electronics setting of 1700 V (EM), 0.30 mA filament current, and 100 eV with scanning at m/z 100-650 (1 sec/SCAN) resulted in simple spectra with easily identifiable molecular ions for C, BE, P and 11-nor-c-THC. The sensitivity of the assay was 1 ng for the drugs of abuse. The method was validated by analyzing 50 urine samples that have been previously screened and confirmed for drugs at the University of Illinois Toxicology Laboratory. The results showed that the DEP method confirmed 87%, 71% 100%, and 85% of the BE, C, P and 11-nor-c-THC. In summary, a rapid and sensitive DEP method for the confirmation of drugs of abuse in urine has been developed which can serve as a useful adjunct to gas chromatographic/mass spectrometric confirmation.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160150
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  • 9
    Electronic Resource
    Electronic Resource
    Model systems for cofactor activity. Biomimetic reduction of vitamin K by 1,3-propanedithiol (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Heteroatom Chemistry 7 (1996), S. 293-294 
    Details
    ISSN: 1042-7163
    Keywords: Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Vitamin K is reduced to vitamin KH2 by lipoate in biological systems. To provide a model system for this reaction, we have studied the in vitro reduction of vitamin K by 1,3- propanedithiol. This reaction occurs rapidly in dimethyl sulfoxide (DMSO) at 23°C, demonstrating the validity of this model system. © 1996 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
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  • 10
    Electronic Resource
    Electronic Resource
    Analysis of retinoids by direct exposure probe mass spectrometry (1988)
    Chichester : Wiley-Blackwell
    Biological Mass Spectrometry 16 (1988), S. 323-325 
    Details
    ISSN: 1052-9306
    Keywords: Chemistry ; Analytical Chemistry and Spectroscopy
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: Recently, our laboratory has investigated the depletion of Vitamin A and its metabolites in experimental animals. High Pressure Liquid Chromatography (HPLC) was used to measure retinal oxidase activity by monitoring the conversion of retinaldehyde (RALD) to retinoic acid (ROIC). In order to obtain more information about these compounds, a Direct Exposure Probe mass spectrometric method was developed to confirm the presence of ROIC and RALD in HPLC peaks. A rapid negative ion chemical ionization (NICI) method using ammonia as reagent gas was developed to detect the presence of ROIC and RALD with picogram sensitivity. The ROIC and RALD peaks were collected from HPLC, extracted with hexane, evaporated under nitrogen and reconstituted in ethanol before placing onto a rhenium filament with current programmed from 0-1.3 A at 50 mA/sec. The instrument employed was a Finnigan 4510 operated in the NICI mode and scanned from m/z 100-650 with a source temperature of 80 C. Other parameters were electron energy 140 eV and filament current at 0.25 mA. Prominent ions were generated at m/z 284 and m/z 300 for RALD and ROIC which were subsequently monitored in the selected ion monitoring mode. In summary, we have developed a rapid retinoid identification method (2.5 minutes) which is more sensitive (pg vs ng) than HPLC and does not require elaborate sample preparation or derivitization. This method can be used as an important adjunct to HPLC enzyme studies.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bms.1200160162
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