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  • 1
    Electronic Resource
    Electronic Resource
    Reproductive behavior and the maintenance of all-female Poecilia (1985)
    Springer
    Environmental biology of fishes 12 (1985), S. 251-263 
    Details
    ISSN: 1573-5133
    Keywords: Unisexual ; Gynogenesis ; Amazon molly ; Triploidy ; Dominance hierarchy ; Mating frenzy ; Social interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis There are four members involved in the breeding complexes of poeciliid fishes found in the freshwaters of northeastern Mexico: males and females of a bisexual species, and diploid and triploid unisexuals. Both unisexuals reproduce by gynogenesis, i.e., an asexual type of reproduction where the sperm triggers egg development but the male genome is excluded to produce clonal offspring. The three types of females are closely related, which suggests that they are potential competitors since all three require the service of the same males. The potential for competition is compounded by a highly skewed sex ratio in favor of females. On the average the unisexuals comprise about 30% of the Poecilia females. This high frequency coupled with a close genetic relatedness to their bisexual hosts, raises the question of how the unisexuals are maintained in nature. Other investigators who work with bisexual/unisexual complexes in the related genus, Poeciliopsis, have postulated that male dominance hierarchies are responsible for restricting the access of subordinate males to their conspecific females. Consequently, these subordinate males mate with unisexual females. The current report tests whether or not this hypothesis applies to bisexual/unisexual complexes of Poecilia. We have found that linear dominance hierarchies appear to function in the defense of home ranges and do not restrict access of males to females. Dominant males exhibit less mating activity than subordinate males towards females. Previous reports showed that males are reproductively competent throughout the year, whereas females show striking asynchrony in their reproductive readiness. Such asynchrony limits the proportion of receptive females at any one time. Consequently, there are more males ready to mate than there are females receptive to their mating attempts. This may lead to mating frenzies. We postulate that these indiscriminate matings maintain the fertility of both unisexuals. When the relative reproductive outputs of adult females are compared, both unisexuals appear as fit as their bisexual congeners.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00005456
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  • 2
    Electronic Resource
    Electronic Resource
    Reduction of competition between bisexual and unisexual females ofPoecilia in northeastern Mexico (1981)
    Springer
    Environmental biology of fishes 6 (1981), S. 39-48 
    Details
    ISSN: 1573-5133
    Keywords: All-female ; Gynogenesis ; Habitat preference ; Mate preference ; Niche dimensions ; Resource allocation ; Social interaction ; sympatric coexistence ; Superfetation ; Triploidy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Synopsis Breeding compexes of poeciliid fishes with a bisexual and two unisexual species were studied for mechanisms permitting Sympatric coexistence. The unisexuals are gynogenetic and thereby sexually dependent on the males of the bisexual species for sperm to initiate development, but inheritance is entirely maternal. Bisexual females are more abundant in headwater localities; unisexuals increase in downstream localities. Males were 10 – 18% of the total poeciliid population, regardless of the relative proportions of bisexual to unisexual females. Downstream localities were typified by greater habitat diversity, including a variety of backwater pools. The unisexuals showed a marked preference for such pools. Both field and laboratory studies showed that all three types of females as well as males preferred shaded areas with a gravel substrate. Although the four types of fish were found together, nearest neighbour data indicated that each type of female preferred its own kind. Males courted throughout the year and were indiscriminate in their choice of mates. Despite the skewed sex ratio, males were not in short supply because only a few females were sexually receptive at a given time. No significant differences existed between bisexuals and unisexuals in their relative reproductive outputs, but they were asynchronous.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00001798
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  • 3
    Electronic Resource
    Electronic Resource
    Technische Fortschrittsberichte, Fortschritte der chem. Technologie, herausgegeb. von B. Rassow; Bd. 6: Optische Messungen des Chemikers und Mediziners, von F. Löwe. 6. neubearbeitete Auflage. (Dresden: 1954, Th. Steinkopff), XX, 362 S., 133 Abb., 4 Spektraltafeln, geb. DM 12,40 (1955)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 6 (1955), S. 163-163 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19550060319
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  • 4
    Electronic Resource
    Electronic Resource
    Magnesium - Fabricating and Casting. OEEC, Paris, 1956, 78 S., 19 Abb. DM 5,- (1957)
    Weinheim [u.a.] : Wiley-Blackwell
    Materials and Corrosion/Werkstoffe und Korrosion 8 (1957), S. 114-114 
    Details
    ISSN: 0947-5117
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/maco.19570080215
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  • 5
    Electronic Resource
    Electronic Resource
    Methan-Gewinnung aus Abfällen (1977)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 49 (1977), S. 25-30 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Sowohl bei der biologischen als auch bei der thermischen Zersetzung von organischen Abfällen entsteht Methan. Die Methan-Bildung verläuft in der Deponie unkontrolliert. Die Gewinnung von Methan ist dabei unvollständig. Bei der biologischen Zersetzung wasserreicher organischer Abfälle in geschlossenen beheizten Behältern läßt sich gezielt Methan gewinnen. Thermische Prozesse zur Methan-Gewinnung (Ent- und Vergasung) befinden sich noch in Entwicklung. Voraussichtlich werden sie nur in Sonderfällen von Interesse sein. Für die großindustrielle Gaserzeugung aus Abfällen sind die Müllmengen in wirtschaftlich erträglichen Einzugsgebieten zu klein.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330490106
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  • 6
    Electronic Resource
    Electronic Resource
    Dampf-Wasserwärmer (1987)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 59 (1987), S. 871-875 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330591114
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  • 7
    Electronic Resource
    Electronic Resource
    Versammlungsberichte (1976)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 48 (1976), S. 82-86 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.330480126
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  • 8
    Electronic Resource
    Electronic Resource
    MO-Berechnungen zur Struktur des Polyvinylchlorids (1980)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 31 (1980), S. 248-251 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The electronic structure and conformation of PVC-oligomer models is investigated, using the EHMO (extended Hückel) approximation. Calculated geometries of conformers are near those with idealized torsional angles. Syndiotactic PVC sequences are by 6 kJ mol-1 more stable than the isotactic helical structure. For changing the conformation of 2,4-dichloropentane a coupled internal rotation of neighbouring C—C bonds is important.
    Notes: Die Elektronenstruktur und Konformation von PVC-Oligomer-Modellen wird mit Hilfe der semiempirischen EHMO (erweiterter Hückel)-Methode untersucht. Berechnete Konformergeometrien liegen in der Nähe der idealisierten Torsionswinkel. Syndiotaktische PVC-Sequenzen sind ca. 6 kJ mol-1 stabiler als eine isotaktische Helix. Für den Konformationswechsel im 2,4-Dichlorpentan ist die gekoppelte innere Rotation um benachbarte C—C-Bindungen wesentlich.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1980.010310407
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  • 9
    Electronic Resource
    Electronic Resource
    Bandstrukturberechnungen an organischen Polymeren - Einfacher methodischer Ansatz und erzielbare Ergebnisse (1987)
    Weinheim : Wiley-Blackwell
    Acta Polymerica 38 (1987), S. 329-334 
    Details
    ISSN: 0323-7648
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: A simple quantum-chemical approach in π-approximation for the estimation of the band characteristics of organic polymers is derived. The results received for some compounds with conjugative bound structure units are presented as example.
    Notes: Ein einfacher quantenchemischer Ansatz zur Bandstrukturberechung in π-Näherung für organische Polymere wird vorgestellt. Die mit ihm erzielbaren Ergebnisse für Verbindungen mit konjugativ verknüpften Struktureinheiten werden in exemplarischer Weise angegeben.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/actp.1987.010380605
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