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  • 1985-1989  (8)
  • 1965-1969
  • Polymer and Materials Science  (5)
  • Productivity  (3)
  • 1
    Electronic Resource
    Electronic Resource
    Unique qualities and special problems of the African Great Lakes (1986)
    Springer
    Environmental biology of fishes 17 (1986), S. 161-183 
    Details
    ISSN: 1573-5133
    Keywords: Meromictic ; Evolution ; Diversity ; Cichlidae ; Productivity ; Aquatic reserves ; Flushing ; Pollution ; Fish introductions ; Lake development ; Limnology ; Fishery management ; Conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The African Great Lakes consist of large, deep rift valley lakes (e.g. Malawi & Tanganyika) and shallower lakes between the Eastern and Western Rifts (e.g. Victoria). They are a group comparable in size to the North American Great Lakes, but are old. Most are seasonally thermally stratified, and wind is the decisive factor that determines the annual cycle of cooling and mixing. Lakes Tanganyika, Malawi and Kivu are meromictic, with deep relict hypolimnia. Large magnitudes and time scales of periodic internal motion, where these have been measured, appear unique among lakes. These lakes harbour the world's richest lacustrine fish faunas, and the family Cichlidae provides the supreme example of geographically circumscribed vertebrate evolution. The lakes provide a unique comparative series of natural laboratories for evolutionary studies. Primary production is generally high, but in the deeper lakes standing stocks of plankton and of small fish species are low. These pelagic populations are characterised by very high P:B ratios. The fisheries are productive and of socio-economic importance. Large-scale mechanised fishing is not compatible with the survival of the diverse fish communities. Cichlids appear especially vulnerable to unselective fishing. Aquatic reserves might offer a means of survival for at least some communities. Various pollution threats exist. Because water retention times are long, extremely long for some deep lakes, and flushing rates are low, the lakes are vulnerable to pollution which would be long-lasting. Introductions of alien fishes have mostly had undesirable or disastrous results. While the faunas are one of the significant natural heritages of mankind, their conservation must realistically be linked to the legitimate development of the lakes for the well-being of the people who live there. Scientific value alone will not protect the lakes. Just as survival of African terrestrial wildlife in extensive reserves depends heavily upon tourism, so also might the cichlid flocks in underwater reserves. Greater interest from the international scientific community is needed to further rational development and conservation of these great lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002094
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    Paper (German National Licenses)
    Fulltext
  • 2
    Electronic Resource
    Electronic Resource
    Unique qualities and special problems of the African Great Lakes (1986)
    Springer
    Environmental biology of fishes 17 (1986), S. 161-183 
    Details
    ISSN: 1573-5133
    Keywords: Meromictic ; Evolution ; Diversity ; Cichlidae ; Productivity ; Aquatic reserves ; Flushing ; Pollution ; Fish introductions ; Lake development ; Limnology ; Fishery management ; Conservation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis The African Great Lakes consist of large, deep rift valley lakes (e.g. Malawi & Tanganyika) and shallower lakes between the Eastern and Western Rifts (e.g. Victoria). They are a group comparable in size to the North American Great Lakes, but are old. Most are seasonally thermally stratified, and wind is the decisive factor that determines the annual cycle of cooling and mixing. Lakes Tanganyika, Malawi and Kivu are meromictic, with deep relict hypolimnia. Large magnitudes and time scales of periodic internal motion, where these have been measured, appear unique among lakes. These lakes harbour the world's richest lacustrine fish faunas, and the family Cichlidae provides the supreme example of geographically circumscribed vertebrate evolution. The lakes provide a unique comparative series of natural laboratories for evolutionary studies. Primary production is generally high, but in the deeper lakes standing stocks of plankton and of small fish species are low. These pelagic populations are characterised by very high P:B ratios. The fisheries are productive and of socio-economic importance. Large-scale mechanised fishing is not compatible with the survival of the diverse fish communities. Cichlids appear especially vulnerable to unselective fishing. Aquatic reserves might offer a means of survival for at least some communities. Various pollution threats exist. Because water retention times are long, extremely long for some deep lakes, and flushing rates are low, the lakes are vulnerable to pollution which would be long-lasting. Introductions of alien fishes have mostly had undesirable or disastrous results. While the faunas are one of the significant natural heritages of mankind, their conservation must realistically be linked to the legitimate development of the lakes for the well-being of the people who live there. Scientific value alone will not protect the lakes. Just as survival of African terrestrial wildlife in extensive reserves depends heavily upon tourism, so also might the cichlid flocks in underwater reserves. Greater interest from the international scientific community is needed to further rational development and conservation of these great lakes.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00698196
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    Paper (German National Licenses)
    Fulltext
  • 3
    Electronic Resource
    Electronic Resource
    African lakes and their fishes: conservation scenarios and suggestions (1987)
    Springer
    Environmental biology of fishes 19 (1987), S. 3-26 
    Details
    ISSN: 1573-5133
    Keywords: Captive propagation ; Extinction ; Genetic variability ; Evolution ; Speciation ; Lates niloticus ; Nile perch ; Haplochromines ; Tilapia ; Clupeids ; Oil pollution ; Productivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Man has been associated with a variety of lakes throughout his evolutionary history in Africa. Lakeside dwellers have a close association with and understanding of these lakes. In the past four decades, however, overexploitation, introductions of alien fishes and the possibility of oil pollution present frightening prospects of irreversible losses and massive extinction. The development of scientific understanding of the life support processes, the ecosystems and the rich communities of these lakes has been so outpaced by exploitation and manipulations that accurate predictions regarding the future are impossible. Shallow lakes are more sensitive to physico-chemical changes caused by climatic as well as agricultural and industrial development than deep lakes, but their biotae are endowed with a resilience which facilitates recovery from major depletions to population size. In contrast, the speciose endemic cichlid faunae of deep lakes are sensitive to fishing pressure, are awkward to manage and should be regarded as representing a much smaller resource than initially imagined. The clupeids of Lake Tanganyika can sustain intensive fishing, but their introduction into other natural lakes is not recommended. Enormous changes to native faunae followed the introduction of Lates niloticus to lakes Kyoga and Victoria with dramatic consequences for the fisheries, for the socio-economic status of the region and for the maintenance of biotic diversity. Extinction of almost 300 fish species is a possible further consequence of L. niloticus predation. Intensive selective fishing for L. niloticus is being initiated, but is unlikely to resolve the problem. In the time necessary to substantially reduce L. niloticus, numerous endemic fishes may suffer extinction. A viable alternative to extinction of these species is captive propagation. Conservation of fishes by captive propagation is not a common or well documented practice. To encourage the acceptance of this conservation option a theoretical scenario in which the concepts and protocols are applied to the fishes of Lake Victoria is given. The possibility of returning rescued populations to the lake at a later date, assuming L. niloticus populations have been reduced, is also discussed. It is recommended that captive propagation should be practised to conserve species and to retain the option of returning rescued taxa. Scientists are urged to seek the funding to study tropical ecosystems so that conservation and rational development may acquire a sound foundation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00002733
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    Paper (German National Licenses)
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  • 4
    Electronic Resource
    Electronic Resource
    Mechanism of accelerated photofading of thioether anthraquinone dyes in styrene butadiene resinsPresented, in part, at the IUPAC Photochemistry Symposium at Interlaken, Switzerland, July 1984. (1988)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 36 (1988), S. 1205-1219 
    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: Many anthraquinone dyes fade in visible light up to 100 times faster in styrene butadiene copolymers than in polyester resins or polystyrene. A mechanistic investigation of the photofading of 1,5-dihydroxy-2,6-diisobutyl-4-thiophenylanthraquinone has established that the dye sensitizes formation of singlet oxygen, a very reactive species, which attacks the double bonds in the styrene butadiene, resulting in extensive chain cleavage and peroxide formation. The major process is the oxidation of the polymer, and the dye fading is a minor process whereby the dye is apparently attacked by polymeric peroxides. The mechanism appears to be general for anthraquinone dyes, especially those with thioether, amino, hydroxy, or double-bond functionality. Unfortunately the fading is unaffected by most anticxidant stabilizers: the best result achieved was a doubling of half-life with 1 wt% Spinuvex A-36. This is still insufficient to give colored styrene butadiene copolymer resins the intrinsic dye stability available in other polymers, rendering styrene butadiene unsuitable for applications requiring high photostability of anthraquinone dyes.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1988.070360520
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    Paper (German National Licenses)
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  • 5
    Electronic Resource
    Electronic Resource
    Acrylonitrile-based copolymers: Synthesis, characterization, and formation of ultrafiltration membranes utilized for the immobilization of proteinsFinal author approval January 15, 1985. (1985)
    New York, NY [u.a.] : Wiley-Blackwell
    Journal of Applied Polymer Science 30 (1985), S. 1113-1132 
    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: Various high molecular weight copolymers of acrylonitrile and a vinyl comonomer containing an aryl amine, a pyridine, or an aliphatic hydroxyl group were synthesized via slurry polymerization techniques so as to contain from 1 to 15 mol % functional comonomer. The comonomer content was quantitated by ultraviolet absorbance, base titration of acid polymer salts, and/or relative chemical reactivity with trichloro-s-triazine. Thin films were cast from copolymer solutions, coagulated into unsupported ultrafiltration membrances, and characterized with respect to both water permeability and pore size distribution. Analysis by size exclusion chromatography of the membrane permeate of a pool of dextran fractions yielded a continuous distribution curve for membrane pore size over the range 1.5 to 70 nm. The ultrafiltration membranes were used for protein immobilization after appropriate chemical activation. The three distinct types of functional copolymers gave comparable results for α-chymotrypsin, with protein weight loadings of 6-12% and 40-65% retention of enzymatic specific activity.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/app.1985.070300318
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    Paper (German National Licenses)
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  • 6
    Electronic Resource
    Electronic Resource
    Rat peritoneal macrophage adhesion to hydroxyethyl methacrylate-ethyl methacrylate copolymers and hydroxystyrene-styrene copolymers (1985)
    Hoboken, NJ : Wiley-Blackwell
    Journal of Biomedical Materials Research 19 (1985), S. 1101-1115 
    Details
    ISSN: 0021-9304
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Medicine , Technology
    Notes: Macrophage adhesion to a wide variety of substrates has been measured, but no systematic study of the influence of specific substrate chemical properties on adhesion is available. These studies were conducted using two series of materials, copolymers of hydroxyethyl methacrylate (HEMA) and ethyl methacrylate (EMA) and copolymers of hydroxystyrene and styrene, to determine the effect of a single chemical property, polar character, on adhesion. Rat periotoneal macrophages were allowed to contact polymer substrates for periods ranging from 1 to 240 min before being subjected to a shear stress of 60-120 dynes/cm2 in a thin-channel flow cell. Percentage adhesion was calculated from the number of cells that remained adherent to the substrate after 30 s of applied shear stress. Macrophages remained adherent to 100% EMA and all hydroxystyrene-styrene copolymer surfaces after only 1 min of contact. In copolymers of the HEMA-EMA series, the time required to attain peak adhesion levels increased with increasing substrate hydrophilicity (increasing HEMA content). Cells did not attach to the 20% EMA/80% HEMA copolymer and the 100% HEMA polymer. The results demonstrate that there is a time delay between contact and adhesion of the cells to surfaces of increasing hydrophilicity within the HEMA-EMA series and no time delay with the hydroxystyrene-styrene series. The time delay is thought to be a function of the excluded volume provided by polymers that are able to undergo significant chain rotation and or swelling in the solvent, water. Small excluded volumes present in copolymers of high EMA content and all hydroxystyrene-styrene copolymers offer little or no resistance to formation of adhesive bonds by macrophages, whereas copolymers with large excluded volumes (high HEMA content) prevent contact and/or adhesion. A mechanism based on the net excluded volumes of both the cell and substrate surface macromolecule is proposed to explain this phenomenon.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/jbm.820190919
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  • 7
    Electronic Resource
    Electronic Resource
    Dehydrofluorination of poly(vinylidene fluoride) in dimethylformamide solution: Synthesis of an operationally soluble semiconducting polymer (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Chemistry Edition 23 (1985), S. 1057-1061 
    Details
    ISSN: 0360-6376
    Keywords: Physics ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The reaction of poly(vinylidene fluoride) with several different bases in dimethylformamide solution yields dehydrofluorinated products with conjugated polyene structures. The extent of elimination can be controlled by varying the amount of added base. The structural properties of dehydrofluorinated materials depend on the base used. Polymer films cast from DMF solution exhibit electronic conductivity upon iodine doping; the conductivity is also a function of the base used.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.170230410
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  • 8
    Electronic Resource
    Electronic Resource
    Gravimetric analysis of polymer surface chemistry: A sensitive technique for monitoring reactions at polymer surfaces (1985)
    New York : Wiley-Blackwell
    Journal of Polymer Science: Polymer Letters Edition 23 (1985), S. 33-36 
    Details
    ISSN: 0360-6384
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/pol.1985.130230107
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