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  • 1
    Electronic Resource
    Electronic Resource
    Multiple paternity in meadow voles (Microtus pennsylvanicus): investigating the role of the female (1999)
    Springer
    Behavioral ecology and sociobiology 45 (1999), S. 283-291 
    Details
    ISSN: 1432-0762
    Keywords: Key words Sexual selection ; Female choice ; Microtus pennsylvanicus ; Multiple paternity ; Meadow vole
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Multiple paternity in single litters conceived in the wild was recently demonstrated in meadow voles (Microtuspennsylvanicus). In this study, we used an experimental approach (males tethered and females allowed to mate freely with one or several males) to investigate the role of female meadow voles in multiple paternity. We found that among 29 (of 39) females that copulated during our experiment, 79.3% chose to mate with more than one male. Female behavior in meadow voles thus clearly promotes multiple paternity and their role is an active one. Some of the hypotheses explaining promiscuity in meadow voles should be reconsidered in light of this result. We do not know the primary determinant of female mate choice, but male body mass played a secondary role in driving female preferences. The partial dependence between male body mass and female choice, coupled with the active role played by females, indicates that intersexual selection has the potential for reinforcing the effects of intrasexual selection (male-male dominance relationships) in this species. Finally, we demonstrate that the time period over which tests are conducted is an important part of the design of experiments aimed at understanding the role of females in multiple paternity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002650050563
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  • 2
    Electronic Resource
    Electronic Resource
    Thermochromic properties of polythiophenes: structural aspects (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 869-877 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Temperature-dependent optical absorption measurements have revealed important thermochromic effects in poly(3-dodecylthiophene) and poly(3-octyloxy-4-methylthiophene) between 25 and 150°C which are related to a planar to non-planar transition of the main polymer chain. This conformational transition is caused by an increase of the repulsive intrachain steric interactions upon heating, which then force the thiophene backbone to adopt a non-planar conformation. On the other hand, as observed with poly(3-octyloxythiophene), if the side chains do not lead to large steric interactions, the polymer can maintain a highly conjugated structure even at high temperatures while, if the steric interactions are too strong (e.g. poly(3,3′-dihexyl-2,2′-bithiophene)), no co-planar conformation can be adopted.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940311
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  • 3
    Electronic Resource
    Electronic Resource
    Monomer reactivity vs. regioregularity in polythiophene derivatives (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 1709-1722 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: It has been recently reported that a simple chemical oxidation of 3-alkoxy-4-methylthiophenes leads to highly regioregular polymers with enhanced electrical and optical properties. A joint experimental and theoretical study on different alkyl-, alkylthio-, and alkoxy-substituted thiophenes and bithiophenes has revealed a strong correlation between the distribution of the unpaired electron π-spin density in the oxidized starting compounds and the regionchemical structure of the resulting polymers. In particular, these calculations have clearly indicated that an asymmetric reactivity of the oxidized monomers or dimers at the 2- and 5-positions can lead to polymers with a high head-to-tail content. This theoretical tool should be useful for the future design of regioregular and nonregioregular polymers from chemical or electrochemical oxidative polymerization reactions.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980602
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  • 4
    Electronic Resource
    Electronic Resource
    Chromic phenomena in neutral polythiophene derivatives (1996)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 197 (1996), S. 2077-2087 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Thermochromic phenomena in various regioregular and non-regioregular polythiophene derivatives have been investigated both in the solid state and in solution. These studies have revealed the existence of two different types of thermochromic phenomena which are correlated to the substitution pattern of the polymers. Formation of delocalized conformational defects (twistons) has been observed in regioregular polythiophene derivatives but did not occur in non-regioregular polythiophenes. For the latter polymers, only localized conformational defects can be created along the polymer backbone leading to a monotonic blue shift of the absorption maximum upon heating. It is suggested that all these optical features are driven by order-disorder transitions of the side-chains, side-chain disordering increasing their steric hindrance and/or disrupting short-range ordered assemblies, which then force the thiophene backbone to adopt a nonplanar conformation. It has been also found that non-covalent interactions between alkali metal ions and regioregular ether-substituted polythiophenes can modify the side-chain organization and can lead to interesting ionochromic effects. It is believed that chromic phenomena can be induced via a large range of external stimuli which should lead to the development of novel affinitychromic and photochromic materials.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1996.021970701
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