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  • 1
    Electronic Resource
    Electronic Resource
    Loss of tensile strength in liquids without property discontinuities: A thermodynamic analysis (1987)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 86 (1987), S. 2229-2235 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The thermodynamically consistent behavior of any fluid whose tensile strength exhibits a maximum with respect to temperature (tensile instability) is derived for the case where the isochore corresponding to the fluid density at such a maximum is single branched (i.e., a metastable solution exists only for temperatures higher than the tensile instability temperature). The resulting thermal and volumetric picture is considerably simpler than for the recently derived behavior corresponding to the case where the tensile instability isochore admits metastable solutions both above and below the tensile instability temperature (double-branched limiting isochore). Density extrema are inseparable from tensile strength maxima: a tensile instability is, in fact, the low-pressure intersection of a spinodal curve and a locus of density extrema.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.452121
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  • 2
    Electronic Resource
    Electronic Resource
    Erratum: On the nature of the tensile instability in metastable liquids and its relationship to density anomalies [J. Chem. Phys. 84, 3339 (1986)] (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 1207-1207 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451874
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  • 3
    Electronic Resource
    Electronic Resource
    On the nature of the tensile instability in metastable liquids and its relationship to density anomalies (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 3339-3345 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Tensile instability is a hitherto unexplained phenomenon whereby a metastable liquid loses tensile strength as the temperature is reduced in the vicinity of its triple point. The thermodynamically consistent behavior which must be exhibited by any liquid in the vicinity of a tensile instability displays a variety of unusual phenomena: nonanalytic density maxima, spinodal retracing, and density anomalies (negative thermal expansion coefficient) in the vicinity of the spinodal curve. Loss of tensile strength implies (and is inseparable from) density anomalies in the vicinity of the spinodal curve. This important conclusion is derived here from first principles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450269
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  • 4
    Electronic Resource
    Electronic Resource
    On the entropy changes and fluctuations occurring near a tensile instability (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 4005-4010 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Several liquids exhibit an apparent loss of tensile strength (tensile instability) as their temperature is lowered. Assuming that such substances exhibit a true minimum in the PT projections of their spinodal curves, the thermodynamically consistent behavior that follows from this hypothesis displays a variety of unusual phenomena, of which the PVT aspects have been recently discussed. If, along the tensile instability isochore, the reciprocal compressibility vanishes linearly with respect to temperature (as is the case for a van der Waals fluid near the spinodal) an unusual metastable phase transition with discontinuous entropy and thermal expansion coefficient but continuous volume must occur if this isochore admits a metastable solution below the tensile instability temperature. The form of the specific heat divergence, as well as the equations of phase diagram loci of constant correlation length follow from the nature of the PVT surface in the vicinity of a tensile instability.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450923
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  • 5
    Electronic Resource
    Electronic Resource
    Crystal structure of (E)-5-hydroxypyrrolizidin-3-one and (Z)-5-thioketalpyrrolizidin-3-one (1984)
    Springer
    Journal of chemical crystallography 14 (1984), S. 565-572 
    Details
    ISSN: 1572-8854
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract The crystal structures of (E)-5-hydroxypyrrolizidin-3-one (2) and (Z)-5-thioketalpyrrolizidin-3-one (3) have been determined by single-crystal x-ray diffraction techniques and refined by full-matrix least squares. Molecule2 crystallizes in the monoclinic space groupP21/a(No. 14) witha=7.887(3) Å,b=9.788(5) Å,c=9.316(4) Å,β=100.6(1), andZ=4. Molecule 3 crystallizes in the monoclinic space groupP21/c witha=12.947(14) Å,b=10.553(14) Å,c=9.629(14) Å,β=101.4(1), andZ=4. The calculated density for both molecules is 1.33 g cm−1. FinalR-factors were 5.1% for2 and 8.59% for3. The x-ray results showed that a change in configuration occurred in the reaction going from2 to3.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01182143
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  • 6
    Electronic Resource
    Electronic Resource
    Dopamine regulation of testicular activity in intact and hypophysectomized frogs,Rana esculenta (1993)
    Springer
    Cellular and molecular life sciences 49 (1993), S. 65-67 
    Details
    ISSN: 1420-9071
    Keywords: Testis ; spermiation ; L-dopa ; pimozide ; Amphibia
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract In intact frogs, both GnRHA and L-dopa were able to increase testicular and plasma androgen levels and to induce spermiation. The dopamine antagonist pimozide inhibited both the effects of L-dopa but not those of GnRHa. Hypophysectomy reduced androgen levels, but spermiation was still induced by both GnRHa and L-dopa, suggesting that these agents can directly influence the testis through a route not involving the pars distalis. Again, pimozide antagonised spermiation induced by L-dopa but not that induced by GnRHa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01928792
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  • 7
    Electronic Resource
    Electronic Resource
    Mantle source heterogeneity in the Campanian Region (South Italy) as inferred from geochemical and isotopic features of mafic volcanic rocks with shoshonitic affinity (1999)
    Springer
    Mineralogy and petrology 67 (1999), S. 163-192 
    Details
    ISSN: 1438-1168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Description / Table of Contents: Résumé De nouvelles analyses géochimiques d'éléments majeurs et en traces ainsi que des rapports isotopiques du Sr et du Nd sont été obtenues sur des roches volcaniques mafiques à affinité shoshonitiques provenant des îles de Procida et Ventotene (Région Campanienne, Italie du Sud). Les variations géochimiques et isotopiques observées au sein des séries volcaniques de ces deux îles sont interprétées en terme de processus de différenciation en système ouvert, tenu pour responsable d'un enrichissement d'un certain nombre d'éléments en traces et de leur composition en Sr radiogénique. Cependant, les teneurs en éléments traces et les compositions isotopiques en Sr et Nd des échantillons les moins évolués parmi ceux étudiés reflètent les caractéristiques de leur source, avec une contamination crustale très négligeable des magmas primitifs. Ces données démontrent que des sources distinctes sont à l'origine des magmas primitifs. Pour Ventotene, cette source doit être un manteau asthénosphérique et/ou lithosphérique dont la signature est similaire à celle de basaltes transitionnels de dorsale océanique (T MORB), légèrement enrichie en éléments dérivants d'une croûte plongeant dans une subduction comme des sédiments mameux (pour environ 7%) analogues aux cherts des Appenins de Toscane et comportant un apport en calcaire. Dans le cas de Procida, cette source doit être un manteau asthénosphérique et/ou lithosphérique montrant une signature de type T-MORB légèrement plus enrichie qu' à Ventotene, également modifiée par un apport venant d'une croûte en subduction, probablement une faible quantité (environ 2.5%) de sédiments de nature océanique (principalement terrigène/pélagique). Ces différences sont attestées par des rapports Zr/Nb, Y/Nb, Sc/Nb, V/Nb, LILE/HFSE, LREE/HSFE and87Sr/86Sr plus bas et des rapports Ba/La et143Nd/144Nd plus harts, ainsi que par l'absence d'une anomalie en Eu dans les compositions des roches volcaniques les moins évoluées de Procida par rapport à celles de Ventotene, qui elles, au contraire, montrent une anomalie en Eu significative. Ainsi, une importante hétérogénéité du manteau existe sous la Campanie. Cette hétérogénéité doit être la conséquence de la nature différente des croûtes en subduction et qui sont en contact le long de la ligne tectonique de la plaine de la rivière Volturno: an Nord-Ouest, une croûte continentale, sismiquement inactive, plonge sous le Latium alors qu'au Sud-Est, une croûte océanique, sismiquement active, plonge sous la Calabre et jusque sous la Campanie.
    Notes: Summary Major, trace element and Sr-Nd-isotopic data on mafic volcanic rocks with shoshonitic affinity from the islands of Procida and Ventotene (Campanian Region, South Italy) are reported. Within-suite chemical and isotopic variations are interpreted in terms of open system differentiation processes held responsible for enrichment in a number of trace elements and for radiogenic Sr observed in both Procida and Ventotene volcanic sequences. Conversely, trace element contents and Sr-Nd-isotopic compositions of the least-evolved among the investigated samples are thought to reflect source region characteristics with only negligible crustal contamination of the primary magmas. The data support an origin from distinct source regions for the primary magmas. In the case of Ventotene, the source would have been asthenospheric and/or lithospheric mantle with features similar to transitional mid-ocean ridge basalts (T-MORB), modified by enriching agents made up mainly of subducted slab-released components coming from marly sediments (about 7%) similar to cherts from Tuscan Apennines plus a limestone contribution. In the case of Procida, the source would have been asthenospheric and/or lithospheric mantle with a slightly more enriched T-MORB-like feature with respect to Ventotene, modified by slab-derived enriching agents, likely represented by a small amount of sediments (about 2.5%) of oceanic nature (mostly terrigenous/pelagic). These differences are constrained by lower Zr/Nb, Y/Nb, Sc/Nb, V/Nb, LILE/HFSE, LREE/HFSE and87Sr/86Sr, higher Ba/La and143Nd/144Nd ratios, as well as by the lack of a detectable negative Eu anomaly, in the least-evolved volcanic rocks of Procida, with respect to those of Ventotene, which show conversely a significant negative Eu anomaly. Thus, a sharp heterogeneity exists in the mantle beneath the Campanian Region. It is thought to be the consequence of two different slabs which are in contact along the Volturno River Plain tectonic line: a continental slab, seismically inactive, descending beneath the Latium Region, and an oceanic slab, seismically active, descending beneath the Calabria, up to the Campanian Region.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01161520
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  • 8
    Electronic Resource
    Electronic Resource
    Survival of hurricane-generated coral fragments and a disturbance model of reef calcification/growth rates (1980)
    Springer
    Oecologia 46 (1980), S. 322-329 
    Details
    ISSN: 1432-1939
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Hurricane Gerta, with winds reaching 150 km/h, crossed the Belize barrier reef on September 18, 1978. Breakage and scouring of corals occurred in all zones of the reef to a depth of approximately 25 m. Survivorship of storm-generated coral fragments and detached colonies is strongly size dependent, conforming to the power function Y=4.44X0.66 where Y is the percent of fragments and X is the fragment size. Forty-six percent of detached Acropora palmata branches, which are larger ( $$\bar X$$ =37.6 cm long) than fragments of other species ( $$\bar X$$ =16.7 cm long), survived. Overall, 39% of fragments and detached colonies survived. This high survivorship, which probably increased the total number of colonies present, and redistribution of corals may explain the rapid recovery of reefs from all but the severest hurricanes. Storms appear to prevent coral reefs from reaching a mature state characterized by low calcification and growth rates. Therefore, we suggest that long-term reef calcification and growth rates are highest on reefs periodically distrubed by storms of intermediate intensity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00346259
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  • 9
    Electronic Resource
    Electronic Resource
    Exotic grass invasion alters potential rates of N fixation in Hawaiian woodlands (1998)
    Springer
    Oecologia 113 (1998), S. 179-187 
    Details
    ISSN: 1432-1939
    Keywords: Key words N fixation ; Dry tropical forest ; Grasslands ; Fire ; Hawai'i
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Exotic grass invasion promotes fire which drives the conversion of native woodlands to exotic grasslands in the seasonally dry submontane forests of the island of Hawai'i. We compared potential rates of N fixation in an unburned forest site and a converted grassland site using the acetylene reduction assay. In addition to measuring rates of N fixation on separate and mixed substrates in each site, we tested the effect of abiotic factors on rates of N fixation of specific substrates. We hypothesized that rates of N fixation would be higher in the converted grassland site. N fixation estimates were 4.9 kg N ha−1 year−1 for the unburned forest, and 0.10 kg N ha−1 year−1 for the grassland site, so our hypothesis was rejected. The N fixation in the unburned forest occurs mostly on the leaf litter of native woody species. These substrates are absent from the grassland site, except for wood debris which was not consumed during the fires. No nitrogenase activity was detected in the rhizosphere and litter of grasses, the rhizospheres of shrubs or in soil. Although wood debris is not a significant contributor to the N fixed in the unburned forest, it contributes the majority of N fixed in the grassland. The response of nitrogenase activity to varying conditions of moisture and temperature suggests that microclimatic differences between sites do not control differences in N fixation activity; rather, these differences are due to the abundance of N-fixing substrates. The substantial decrease in N fixation activity after the conversion from woodland to grassland implies that ecosystem-level rates of N accretion are decreased by fire in these sites so much that the N lost during volatilization due to fire is not replenished over the long term by N fixation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420050366
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  • 10
    Electronic Resource
    Electronic Resource
    Invasion of maritime chaparral by the introduced succulentCarpobrotus edulis (1993)
    Springer
    Oecologia 95 (1993), S. 14-21 
    Details
    ISSN: 1432-1939
    Keywords: Fire ; Invasion ; Alien species ; Introduced species ; Herbivory
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Invasion by the alien succulent,Carpobrotus edulis, has become a common occurrence after fire in maritime chaparral in coastal California, USA. We studied post-burnCarpobrotus establishment in chaparral that lackedCarpobrotus plants before the fire and compared seedbank and field populations in adjacent burned and unburned stands.Carpobrotus seeds were abundant in deer scat and in the soil before burning. Burning did not enhance germination: many seeds were apparently killed by fire and seed bank cores taken after fire revealed no germinable seeds. Laboratory tests showed that temperatures over 105°C for five minutes killedCarpobrotus seeds. In a field experiment involving use of herbivore exclosures, we found that herbivory was an important source of mortality for seedlings in both burned and unburned chaparral. All seedlings, however, died outside of the burn regardless of the presence of cages. Establishment there is apparently limited by factors affecting plant physiology. In the burned area, seedlings that escaped herbivory grew very rapidly. Overall, it appears that herbivory limited seedling establishment in both burned and unburned sites but that the post-burn soil environment supportedCarpobrotus growth in excess of herbivore use, thus promoting establishment.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00649501
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