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  • Springer  (84)
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  • 1
    Electronic Resource
    Electronic Resource
    Comparing plant life histories using elasticity analysis: the importance of life span and the number of life-cycle stages (1995)
    Springer
    Oecologia 104 (1995), S. 79-84 
    Details
    ISSN: 1432-1939
    Keywords: Transition matrix ; Elasticity analysis ; Plant life history ; Survival ; Life-cycle stages
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Recent studies have used transition matrix elasticity analysis to investigate the relative role of survival (L), growth (G) and fecundity (F) in determining the estimated rate of population increase for perennial plants. The relative importance of these three variables has then been used as a framework for comparing patterns of plant life history in a triangular parameter space. Here we analyse the ways in which the number of life-cycle stages chosen to describe a species (transition matrix dimensionality) might influence the interpretation of such comparisons. Because transition matrix elements describing survival (“stasis”) and growth are not independent, the number of stages used to describe a species influences their relative contribution to the population growth rate. Reduction in the number of stages increases the apparent importance of stasis relative to growth, since each becomes broader and fewer individuals make the transition to the next stage per unit time period. Analysis of a test matrix for a hypothetical tree species divided into 4–32 life-cycle stages confirms this. If the number of stages were defined in relation to species longevity so that mean residence time in each stage were approximately constant, then the elasticity of G would reflect the importance of relative growth rate to λ. An alternative, and simpler, approach to ensure comparability of results between species may be to use the same number of stages regardless of species longevity. Published studies for both herbaceous and woody species have tended to use relatively few stages to describe life cycles (herbs: n=45, $$\bar x = 6.16 \pm 4.63$$ ; woody plants: n=21, $$\bar x = 8.38 \pm 3.57$$ ) and so approximate this approach. By using the same number of stages regardless of longevities, the position of species along the G-L side of the triangular parameter space largely reflects differences in longevity. The extent of variation in elasticity for L, G and F within and between species may also be related to factors such as successional status and habitat. For example, the shade-tolerant woody species, Araucaria cunninghamii, shows greater importance for stasis (L), while the gap-phase congener species, Araucaria hunsteinii, shows higher values for G (although values are likely to vary with the stage of stand development).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00365565
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  • 2
    Electronic Resource
    Electronic Resource
    Synthesis and thermodynamics properties of poly(ethylene oxide) prepared in diphenylzinc-water (1990)
    Springer
    Polymer bulletin 24 (1990), S. 589-596 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract Poly (ethylene oxide) (PEO) samples, obtained using diphenylzinc-water as initiator, have been used to determine some characteristics of this polymer. The unperturbed dimensions of PEO have been obtained by the application of various theoretical treatments to viscometry measurements carried out in a good solvent. The following relationship between intrinsic viscosity and weight average molecular weight has been obtained [ŋ]/dL.g•1 = 3.99x10•4M0.69 W.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00300153
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  • 3
    Electronic Resource
    Electronic Resource
    Thermal decomposition of some imidazole and N-methyl substituted imidazole complexes of palladium(II) (1978)
    Springer
    Journal of thermal analysis and calorimetry 14 (1978), S. 281-290 
    Details
    ISSN: 1572-8943
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Résumé La décomposition thermique dans l'air de plusieurs complexes du chlorure de palladium(II) avec l'imidazole et le méthyl-4-imidazole est décrite. Bien que l'étape finale de la décomposition donne (PdCl2)n qui se décompose ensuite en palladium qui s'oxyde en PdO, des différences intéressantes apparaissent dans les étapes initiales de la décomposition. Les causes de ces différences sont en rapport avec l'effet trans et la présence, dans les complexes avec l'imidazole, de liaisons hydrogÊne qui se rompent vers 220
    Abstract: Zusammenfassung In diesem Beitrag wird die thermische Zersetzung verschiedener Komplexe des Palladium(II)chlorids mit Imidazol und N-Methylimidazol in Luft beschrieben. Obwohl der Endvorgang der Zersetzung (PdCl2)n ergibt, welches dann zu Palladium zersetzt und zu PdO oxidiert wird, bestehen interessante Unterschiede im Anfangsschritt der Zersetzung. Die Ursachen dieser Unterschiede scheinen mit dem Trans-Effekt und der Anwesenheit von Wasserstoffbindungen in den Imidazolkomplexen verbunden zu sein, welche bei Temperaturen um 220
    Notes: Abstract We describe in this paper the thermal decomposition in air of several complexes of palladium(II) chloride with imidazole and N-methylimidazole. Although the final process of the decomposition gives (PdCl2)n which then decomposes to pa ladium which oxidizes to PdO, there are interesting differences in the initial decomposition path. The reasons for these differences appear to be related to the trans-effect and to the presence in the imidazole complexes of hydrogen bonds which break down at temperatures of around 220
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01915166
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  • 4
    Electronic Resource
    Electronic Resource
    Room-temperature oxidation of La2−x Sr x CuO4 (1994)
    Springer
    Journal of superconductivity 7 (1994), S. 913-916 
    Details
    ISSN: 1572-9605
    Keywords: La2−x Sr x CuO4 ; redox process ; transition temperature ; superconductor
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology , Physics
    Notes: Abstract A series of oxidized La2−x Sr x CuO4+y $$(0.05 \preccurlyeq x \preccurlyeq 0.3)$$ compounds has been prepared by treating the starting materials with a solution of Br2 in NaOH at room temperature. The structural modifications due to the oxidation of the materials have been studied by X-ray diffraction. Some of the observed changes are: (i) a large increase in the long parameter of the unit cell for samples with Sr content $$0.05 \preccurlyeq x \preccurlyeq 0.15$$ and (ii) a slight decrease in a along the whole range ofx. Interesting features have been observed regarding the critical temperatures of these materials: transition temperatures are higher for those containing lower Sr amounts (some of them were even nonsuperconducting before the oxidation treatment) in contrast to materials with x≻0.15, whoseT c's do not change very much. The influence of both oxygen and strontium contents on the structural modifications and the superconducting properties of the oxidized materials will be discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00732270
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  • 5
    Electronic Resource
    Electronic Resource
    Protective effect of prior immunization on ocular paracoccidioidomycosis in guinea pigs (1988)
    Springer
    Mycopathologia 103 (1988), S. 35-42 
    Details
    ISSN: 1573-0832
    Keywords: paracoccidioidomycosis ; eye ; guinea pig ; immunization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract The present study reproduced the experimental model of ocular paracoccidioidomycosis in guinea pigs, by the intracardiac inoculation of yeast-forms of P. brasiliensis. Ocular involvement was observed in 80% of the infected animals. The uvea, ciliary body, choroid, iris, lids and the conjunctiva were the structures most commonly affected. To protect the animals against the infection, an immunization protocol was standardized utilizing a P. brasiliensis soluble antigen in Freund's complete adjuvant, administered weekly, during 3 weeks, by the subcutaneous route. Two weeks later, previously immunized guinea pigs were challenged by the intracardiac route with yeast-forms of P. brasiliensis (vaccinated group). When compared with a control group (infection in the absence of prior immunization), the vaccinated animals developed higher levels of anti-P. brasiliensis cellular and humoral immune response and a three times lower frequency of ocular involvement (85.7% vs 28.5%). In addition, the ocular lesions were significantly more localized and contained less fungal cells. The data demonstrated that the subcutaneous immunization was effective in decreasing the frequency and extent of ocular lesions, as well as in blocking fungal multiplication.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00437219
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  • 6
    Electronic Resource
    Electronic Resource
    Propylene oxide polymerization using the diphenylzinc-acetone system in benzene at 60°C (1989)
    Springer
    Polymer bulletin 21 (1989), S. 287-291 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The diphenylzinc-acetone system was used as catalyst for propylene oxide polymerization in benzene solution at 60°C. This system as well as the diphenylzinc-water system is greatly influenced by the molar ratio of acetone to diphenylzinc and the maximum catalyst activity was found for a ratio of unity. GPC results strongly suggest the presence of more than one active species for the system.13CNMR analysis indicates that the resulting poly(propylene oxide) has a head-to-tail arrangement. This system was not an effective catalyst for the styrene oxide polymerization.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00955920
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  • 7
    Electronic Resource
    Electronic Resource
    Epichlorohydrin polymerization using diphenylzinc-cocatalyst systems in benzene solution (1990)
    Springer
    Polymer bulletin 23 (1990), S. 483-489 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Various diphenylzinc-cocatalyst systems were used as initiators of epichlorohydrin polymerization in benzene solution. Water, acetone, butanone, acetophenone and cyclopentanone were employed as cocatalyst but in the most of the cases diphenylzinc alone produced the better conversion to polymer. GPC results suggest the presence of more than one active species for the polymerization initiated by those systems. For diphenylzinc alone as initiator the reaction at 120°C is first order with respect to monomer with kp=1.21x10 -5L mol-1sec-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00419966
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  • 8
    Electronic Resource
    Electronic Resource
    Polymerization of styrene with diphenylzinc-butanone systems (1994)
    Springer
    Polymer bulletin 32 (1994), S. 367-371 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary In the present work we report the results of the polymerization of styrene using diphenylzinc-butanone, Ph2Zn-MeCOEt. Our results indicate that these systems induce the polymerization of styrene reaching a larger conversion when the molar ratio MeCOEt/Ph2Zn=1,0. According to size exclusion chromatography, SEC, studies of the polystyrene obtained using the Ph2Zn-MeCOEt showed unimodal curves and have molecular weight distribution narrower than those obtained using the Ph2Zn-H2O system, suggesting a more simple reaction system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00587876
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  • 9
    Electronic Resource
    Electronic Resource
    Polymerization of styrene with diphenylzinc-cocatalyst systems (1992)
    Springer
    Polymer bulletin 28 (1992), S. 511-516 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary The diphenylzinc-H2O and diphenylzinc-H2O-ButCl systems were used as catalysts for styrene polymerization in solution at various temperatures and solvents. The systems are greatly influenced by the molar ratio H2O/Ph2Zn, and the maximum catalyst activity, in both cases, was found at a molar ratio of 0.75. GPC results strongly suggest the presence of more than one active species. For Ph2Zn-H2O-ButCl system, in dichloromethane at-78°C with the molar ratio of H2O/Ph2Zn=0.75, the reaction is first order with respect to monomer with kp=2.45×10-3 Lmol-1sec-1.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00296040
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  • 10
    Electronic Resource
    Electronic Resource
    Epoxide polymerization (1985)
    Springer
    Polymer bulletin 14 (1985), S. 331-337 
    Details
    ISSN: 1436-2449
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Summary Poly(propylene oxide), PPO, obtained using diphenylzinc, Ph2Zn, and using the diphenylzinc-water system at various molar ratios H2O/Ph2Zn, were studied through 1H NMR and IR spectroscopy establishing that the polymerization initiates by coordition of propylene oxide (PO) to a terminal zinc atom of the active species followed by consecutive insertions of PO units at this zinc atom. The PPO obtained showed Ph-and HO-, HO-and HO-end-groups depending on the molar ratio H2O/Ph2Zn used, and also HO-and PhO-end-groups when oxygen was present in the polymerization system.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00254957
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