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  • 1
    ISSN: 1432-0738
    Keywords: 2,4-D ; Biotransformation ; Urinary excretion ; Agent Orange
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine
    Notes: Abstract The metabolic fate of 2,4-dichlorophenoxyacetic acid (2,4-D)-n-butyl ester in rats has not been extensively studied. Upon subcutaneous administration of a 100 mg/kg dose of 2,4-D butyl ester to four male Wistar rats, urine samples were analyzed by three analytical techniques for the presence of the butyl ester and metabolites. Thin layer chromatography (TLC), gas chromatography using an electron capture detector (GC-ECD), and gas chromatography-mass spectroscopy (GC-MS) were the techniques employed. 2,4-D butyl ester was rapidly hydrolyzed in the body to form 2,4-D acid. Ninety-five percent of the administered dose was excreted into the urine as the free acid within 48 h of injection, while only a small fraction (5%) was excreted over an additional 48 h. No amino acid conjugates or the parent 2,4-D butyl ester could be detected in the urine of treated rats. A minor metabolite (≤2% of dose) was detected by GC-MS analysis of urine samples. This compound appears to be a side chain metabolite of the 2,4-D butyl ester. Some chemical properties of the metabolite were characterized, and a 2,4-D hydroxyethyl ester structure proposed. The mechanism of this minor metabolic formation remains unknown.
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1077-3118
    Source: AIP Digital Archive
    Topics: Physics
    Notes: In this work the role of extended defects on the electrical performance of epitaxial silicon on substrates containing an insulating SiO2 layer has been examined. The buried SiO2 layers in the substrates were obtained by two techniques: implantation of oxygen and zone melt recrystallization. In order to make a thorough structural and electrical evaluation of silicon on the insulator substrates, 5-μm-thick epitaxial capping layers have been simultaneously deposited via chemical vapor deposition on representative insulating substrates and reference wafers. The average minority-carrier lifetime was found to vary from 2.5 to 242 μs depending on the density and distribution of dislocations emerging from the capping epitaxial layer.
    Type of Medium: Electronic Resource
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  • 3
    ISSN: 1749-6632
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Natural Sciences in General
    Type of Medium: Electronic Resource
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  • 4
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 5
    ISSN: 1365-2133
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Medicine
    Notes: A small, but clinically significant proportion of acne patients fail to respond adequately to antibiotic therapy. All non-responding acne patients attending the Leeds General Infirmary between September 1985 and April 1986 (49 out of a total of 610 patients; 8%) were investigated with respect to changes in their acne grade, microbial flora and sebum excretion rate. They were compared with 22 age and sex matched untreated control subjects. It was found that in 65% of non-responding patients there was no microbiological abnormality, in 16% there was evidence of Gram-negative folliculitis and 20% carried predominantly antibiotic resistant propionibac teria compared with only 5% of untreated controls. There was a significant association between erythromycin therapy and the isolation of erythromycin resistant propionibacteria (P 〈 0·001). A causal link, however, has yet to be established between carriage of antibiotic resistant propionibacteria and failure to respond to antibiotic therapy. Our results show that for most patients with recalcitrant acne a non-microbiological explanation must be sought for the lack of therapeutic success. The mean sebum excretion rate (SER) of the non-responding patients was significantly higher than that of matched untreated acne patients (P 〈 0·001). A majority of non responders (69%) had an SER above the upper 95% confidence limit of the control mean. The SER may affect treatment efficacy by influencing the antibiotic concentration within the pilosebaceous ducts.
    Type of Medium: Electronic Resource
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  • 6
    Electronic Resource
    Electronic Resource
    Hoboken, NJ : Wiley-Blackwell
    AIChE Journal 33 (1987), S. 1168-1177 
    ISSN: 0001-1541
    Keywords: Chemistry ; Chemical Engineering
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Moldability criteria and process optimization for both reactive and thermoplastic injection molding hinge on the mold-filling step. The fluid mechanics of the filling step is typically described in terms of a one-dimensional main flow and a complex two-dimensional flow near the advancing front, often termed the “fountain flow.” A unique apparatus which permits direct observation of the fountain flow in a rectangular cavity is described. The motion of tracer lines as well as the pathlines have been photographed for both Newtonian and shear-thinning liquids. The data show clearly the main flow, the transition to the front flow, and the deceleration and acceleration zones in the fountain flow, which lead to a “mushrooming” of the tracer line.In addition, Galerkin finite-element analysis is used to predict the isothermal free-surface flow of a Newtonian liquid near the advancing front between parallel plates. The most interesting visualization of the calculated flow is obtained by tracking lines of material, thus producing numerical tracer experiments. The calculations show the widely varying residence times and the complex shear and extensional deformation histories of fluid elements as they move through the fountain flow region. The calculations are in agreement with the experiments and clarify previous results, both theoretical and experimental, that did not capture the details of the entire flow field.
    Additional Material: 17 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Stamford, Conn. [u.a.] : Wiley-Blackwell
    Polymer Engineering and Science 27 (1987), S. 1229-1235 
    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: The residence time of a fluid particle in mold filling is total time spent in the mold. Displaying curves of constant residence time in the mold gives the space-time distribution during the filling process. A simple method to calculate space-time distributions is presented. Applications to mold filling in reaction injection molding (RIM) are illustrated.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Springer
    Genetica 69 (1986), S. 3-17 
    ISSN: 1573-6857
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Studies of chromosomal variation were undertaken in Anolis grahami. Multiple fission events and extensive variation involving heterochromatic sequences were observed. Distribution of the chromosomal variants did not coincide with subspecies borders. Chromosome numbers ranging from 30 to 37 were observed in both morphological subspecies; different rearrangements were involved in each. C-banding studies revealed cryptic variation in a large macrochromosome of some populations of A. g. grahami, and the presence of an additional heterochromatic arm in A. g. aquarum. Patterns of distribution of various forms, including widespread polymorphism, suggest significant dispersal of Anolis grahami, and little selection against chromosomal heterozygotes.
    Type of Medium: Electronic Resource
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  • 9
    Electronic Resource
    Electronic Resource
    Palo Alto, Calif. : Annual Reviews
    Annual Review of Fluid Mechanics 19 (1987), S. 99-123 
    ISSN: 0066-4189
    Source: Annual Reviews Electronic Back Volume Collection 1932-2001ff
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Type of Medium: Electronic Resource
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  • 10
    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: Adiabatic reactive rheometry involves the simultaneous measurement of viscosity and temperature changes during adiabatic polymerization. Using the adiabatic reactor method to relate temperature to fractional conversion results in a useful rheokinetic tool ideally suited for fastreacting reaction injection molding (RIM) systems for which the mold-filling step is nearly adiabatic. In this work, a small laboratory RIM machine is used to mix the reactants and deliver them to a constant stress rheometer retrofitted with a wide-gap Couette geometry and two thermocouples. Measurements on two polyurethane systems are reported. A simple cross-linking system is used to verify the adiabatic rheokinetic method through comparison to a known gel conversion. Subsequent measurements on a phase-separating RIM system show that increases in catalyst level, hard segment content, and initial reactant temperature result in a decreased gel time and an increased gel conversion. The viscosity rise profiles aid our understanding of the onset and development of phase separation. They are also essential for mold-filling models and establishing moldability criteria for these RIM systems.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
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