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  • 1
    Electronic Resource
    Electronic Resource
    Micro-evolutionary change and population dynamics of a brood parasite and its primary host: the intermittent arms race hypothesis (1998)
    Springer
    Oecologia 117 (1998), S. 381-390 
    Details
    ISSN: 1432-1939
    Keywords: Key words Brood parasitism ; Clamator glandarius ; Coevolution ; Parasite counter-defences ; Pica pica
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A long-term study of the interactions between a brood parasite, the great spotted cuckoo Clamator glandarius, and its primary host the magpie Pica pica, demonstrated local changes in the distribution of both magpies and cuckoos and a rapid increase of rejection of both mimetic and non-mimetic model eggs by the host. In rich areas, magpies improved three of their defensive mechanisms: nest density and breeding synchrony increased dramatically and rejection rate of cuckoo eggs increased more slowly. A stepwise multiple regression analysis showed that parasitism rate decreased as host density increased and cuckoo density decreased. A logistic regression analysis indicated that the probability of changes in magpie nest density in the study plots was significantly affected by the density of magpie nests during the previous year (positively) and the rejection rate of mimetic model eggs (negatively). These results are consistent with a hypothesis (the intermittent arms race hypothesis) of spatially structured cyclic changes in parasitism. During periods of parasitism, host defences continuously improve, and as a consequence, the fitness gains for parasites decrease. When host defences against parasites reach a high level, dispersing parasites have a selective advantage if they are able to emigrate to areas of low resistance. Once parasites have left an area hosts will lose their defensive adaptations due to their cost in the absence of parasitism. The scene is then set for re-colonization by great spotted cuckoos.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050671
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  • 2
    Electronic Resource
    Electronic Resource
    Electroluminescent porous silicon (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 226-228 
    Details
    ISSN: 0935-9648
    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
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19950070228
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  • 3
    Electronic Resource
    Electronic Resource
    Poly(α-butyl β-L-aspartate): A second alkoxycarbonyl nylon-3 derivative in helical conformation (1995)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 196 (1995), S. 253-268 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A structural study was carried out on poly(α-butyl β-L-aspartate), which is a stereoregular nylon-3 derivative with an alkoxycarbonyl group attached to the β-carbon of the main-chain repeating unit. Two crystal forms, namely hexagonal and tetragonal, made of 13/4 and 4/1 helices, respectively, and bearing a structural resemblance to the polypeptide α-helix, were characterized by X-ray diffraction. Though these forms are basically identical to those previously reported for poly(α-isobutyl β-L-aspartate), the crystal transition from hexagonal to tetragonal known to take place in this polymer by effect of heating, was not observed in the present case. Modeling calculations revealed that although similar conformations are favoured for the two polymers in both crystal forms, the relative stability of the 13/4 helix to the 4/1 helix was found to be significantly reduced in the case of the butyl derivative. The presence of helical conformation in solution has been evidenced by both 1H NMR and circular dichroism and the helix-coil transition promoted by acids was investigated by means of these techniques.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1995.021960117
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  • 4
    Electronic Resource
    Electronic Resource
    Polymorphism in an oligo(aryl ether ketone)Dedicated to Prof. Dr. F. J. Baltá Calleja on the occasion of his 60th birthday (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 2089-2099 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: 1,3-Bis(4-phenoxybenzoyl)benzene (1) shows a single melting peak at T1 = 120°C when rapidly crystallized from a methanol/benzene mixture (10:1 v/v) (sample A) and a double melting peak at T1 = 120°C and T2 = 130°C when crystallized slowly (overnight) (sample B). Slow recrystallization of 1 using ethanol instead of methanol induces the formation of large single crystals which only show a single melting peak at T2 = 130°C (sample C). Analysis of powder X-ray diffractograms obtained for A, B and C samples clearly point out the coexistence of two crystalline phases in sample B: phase 1 (observed for sample A) and phase 2 (sample C). From optical microscopy and thermal (DSC) observations, it can be concluded that, upon heating, phase 1 melts at T1 and the molten material converts itself into phase 2 if some crystals of phase 2 are present. Single crystal structure determination of, both, phase 1 and 2 reveal conformational differences of the molecule in both phases which pack in an orthorhombic and a monoclinic unit cell, respectively.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980707
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  • 5
    Electronic Resource
    Electronic Resource
    Branched poly(ethylene glycol) linkers (1997)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 198 (1997), S. 2489-2498 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Novel types of methoxy poly(ethylene glycol) (PEG) linkers (U-PEG linkers) have been synthesized. These PEG linkers are linear polymers that attach to bioactive agents via a functional group, derived from a 2° alcohol, located in the center of the polymer chain versus the traditional terminal attachment site. These new types of linkers can be prepared with different functional groups (e.g. active ester, succinimidyl carbonate, and carbazate) for selected point of attachment, including ethylene oxide oligomers to provide “stems” when steric factors need to be addressed. Conversion of p-nitrophenyl carbonates to the more desirable succinimidyl carbonates has also been accomplished by a novel nucleophilic displacement procedure. Modification of proteins with these reagents is easily accomplished and is illustrated by the conjugation of a U-PEG linker with L-asparaginase.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1997.021980810
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  • 6
    Electronic Resource
    Electronic Resource
    Surface characterization of synthetic vulcanized rubber treated with oxygen plasma (1998)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 26 (1998), S. 385-399 
    Details
    ISSN: 0142-2421
    Keywords: oxygen plasma ; surface treatment ; styrene-butadiene rubber ; adhesion ; T-peel strength ; XPS ; IR-ATR spectroscopy ; contact angle measurements ; SEM ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The surface of a synthetic vulcanized styrene-butadiene rubber (R2) was treated in an oxygen plasma to improve adhesion in joints prepared with a one-component solvent-based polyester-urethane adhesive. The modifications produced on the rubber surface by plasma treatment were assessed using advancing and receding contact angle measurements, x-ray photoelectron spectroscopy, (XPS), infrared-attenuated total reflection spectroscopy and scanning electron microscopy. Adhesion was obtained from T-peel tests of treated R2 rubber/polyurethane adhesive joints. Several experimental variables were considered, such as the radio-frequency power and the length and lifetime of the plasma treatment. The treatment in the oxygen plasma produced a noticeable decrease in contact angle, which can be mainly ascribed to the creation of C—O and C=O moieties on the rubber surface. Advancing and receding contact angles only differed by ∽10°. Depending on the experimental conditions used, some ablation was produced on the surface, which was more noticeable as the length and power of the treatment increased. An adequate performance of adhesive joints was obtained using a power of 50 W and a time for oxygen plasma treatment of 〈10 min. The changes in the rubber surface remained for 2 h after plasma treatment, as indicated by the variation in peel strength and XPS data. Although improved adhesion was obtained by treating the rubber in an oxygen plasma, the T-peel strength values are not sufficient to assure technical use, probably due to the migration of waxes and zinc stearate to the surface once the treatment was carried out. Finally, sulfur oxidation was produced by the plasma treatment, and for severe conditions solid crystals of a sodium salt of an oxidized sulfur compound (sodium sulphate or an organic sulphate) appeared on the treated rubber surface. © 1998 John Wiley & Sons, Ltd.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    Effect of Photoetching on Porous Silicon Morphology (1997)
    Chichester [u.a.] : Wiley-Blackwell
    Surface and Interface Analysis 25 (1997), S. 677-682 
    Details
    ISSN: 0142-2421
    Keywords: silicon ; light irradiation ; surface tension ; transmission electron microscopy ; Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Physics
    Notes: The morphological differences between porous silicon formed in the dark or under illumination have been studied by means of gravimetric measurements, transmission electron microscopy, infrared spectroscopy and cyclic voltammetry. Photoetching has been found to give rise to a complex surface structure, due to the presence of narrower outer silicon fibres, which suffer a more severe cracking process upon drying. © 1997 by John Wiley & Sons, Ltd.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
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  • 8
    Electronic Resource
    Electronic Resource
    Zeolites and Zeotypes as catalystsFinancial support by the Comision Interministerial de Ciencia y Tecnologia of Spain (Project MAT94-0359-C02-01) is gratefully acknowledged. We also wish to thank Dr. V. Fornes and Dr. H. Garcia for their contribution to this work and many helpful discussions. (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 137-144 
    Details
    ISSN: 0935-9648
    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
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19950070206
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  • 9
    Electronic Resource
    Electronic Resource
    Paramagnetic nematic liquid crystals with an iron coreThis work was supported by the CICYT (Spain) under project MAT930104, and the DGICYT (Spain) under project PB92-0040. (1995)
    Weinheim : Wiley-Blackwell
    Advanced Materials 7 (1995), S. 173-176 
    Details
    ISSN: 0935-9648
    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
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/adma.19950070216
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  • 10
    Electronic Resource
    Electronic Resource
    Dielectric relaxation in chlorinated polyethylene-polypropylene copolymersThe authors wish to dedicate this paper to Professor Günter Klar on the occasion of his 60th birthday. (1996)
    New York, NY [u.a.] : Wiley-Blackwell
    Polymer International 41 (1996), S. 337-343 
    Details
    ISSN: 0959-8103
    Keywords: chlorinated polyethylene-polypropylene copolymers ; dynamic dielectric properties ; Fuoss-Kirkwood and Havriliak-Negami empirical equations ; 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: Dielectric relaxation measurements were carried out on eight chlorinated polyethylene-polypropylene (PEPP) copolymers in the range of temperatures covering the main dielectric absorption. Chlorination of PEPP is expected to change the dynamic dielectric properties gradually with increasing amount of chlorine in the polymer chains. Thus, in the present study, increasing degrees of chlorination give a clear shift of the glass transition temperature towards higher values, except in the range between 40 and 51% chlorine, where an anomalous behaviour was observed. The same tendency is also observed in the relaxation strength (Δ∊). The value of Δ∊ has been estimated by using a nonlinear squares regression program (LEVM6) to calculate the parameters of the Havriliak-Negami empirical equation. It appears reasonable to assume that the anomalous behaviour observed can be attributed to a compensation of the dipolar moments of chlorine groups in the macromolecules.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
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