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  • 1
    ISSN: 1573-904X
    Keywords: tissue uptake ; extraction efficiency ; blood flow-limited models ; 2,3,7,8-tetrachlorodibenzo-p-dioxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Incorporation of First-Order Uptake Rate Constants from Simple Mammillary Models into Blood-Flow Limited Physiological Pharmacokinetic Models via Extraction Efficiencies. W. L. Roth, L. W. D. Weber, and K. Rozman (1995). Pharm. Res. 263–269. First-order rate constants obtained from classical pharmacokinetic models correspond to mammillary systems in which all of the blood (or plasma) is assumed to be located in a central compartment. In such models the rate at which chemicals are transported out of this pool and into another compartment is the product of the mass of chemical in the central compartment multiplied by a rate constant, which is not limited in magnitude by the blood flow, or the rate at which chemicals from the blood are delivered to the peripheral compartment. Most of the physiologically-based models published to date dispense with some of the information available from mammillary models by assuming that all of the chemical delivered by the flow of blood rapidly equilibrates and can be taken up by the tissue under the control of a “partition coefficient” (Rij = Cj/Ci). We show that the partition coefficient alone does not retain the uptake rate (kji) information available from a classical mammillary model, but that the uptake rate information can be incorporated via unitless extraction efficiency parameters, εj.
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  • 2
    ISSN: 1432-136X
    Keywords: Fish ; Myoglobin ; Oxygen binding affinity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Summary Myoglobins from rat, coho salmon (Oncorhynchus kisutch), buffalo sculpin (Enophrys bison) hearts, and yellowfin tuna (Thunnus albacares) red skeletal muscle were partially purified and their O2 binding affinities determined. Commercially prepared sperm whale myoglobin was employed as an internal standard. Tested at 20°C, myoglobins from salmon and sculpin bound O2 with lower affinity than myoglobins from the rat or sperm whale. Oxygen binding studies at 12°C and 37°C suggest that this difference is adaptive, permitting myoglobins from cold-adapted fish to function at physiologically relevant temperatures. Taken together, purification and O2 binding data obtained in this study reveal a previously unrecognized diversity of myoglobin structure and function.
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  • 3
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The melting and solidification behaviour of various compositions across the system Zn2SiO4- Mg2SiO4 (willemite-forsterite) was studied by means of photoemission electron microscopy, X-ray diffraction and DTA. The results revealed the peritectic type of the phase system instead of the earlier assumed eutectic one. During the formation of willemite solid solutions by rapid solidification of zinc-silicate-rich melts, grain-boundary enrichment of zinc oxide besides magnesium silicate takes place. From melts richer in magnesium silicate, forsterite solid solution forms primarily. The sluggish process of its peritectic decomposition during cooling and the preferred subsolidus formation of zinc silicate give rise to the formation of a ternary non-equilibrium phase assemblage even at slow cooling.
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  • 4
  • 5
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On the Reactivity of Disilylphosphido Complexes of Iron and Ruthenium towards 2,4,6-t-Bu3C6H2AsCl2. Generation and Structures of Arsaphosphenyl Complexes, Diphospha-ariranes, Phosphadiarsiranes, and 1,2-Diphospha-3,4-diarsetanesThe reaction of (η5-C5Me5)(CO)2Fe—P(SiMe3)2 (1a) with 2,4,6-t-Bu3C6H2AsCl2 (= Aryl AsCl2) (6) leads to the formation of the heterocycles [(η5-C5Me5)(CO)2Fe—P]2As-Aryl (7a), (η5-C5Me5)(CO)2Fe—P(As-Aryl)2 (8a), and [(η5-C5Me5)(CO)2Fe—P-As-Aryl]2(9a). The instable arsaphosphenyl complex [(η5-C5Me5)(CO)2Fe—P=As-Aryl] can be intercepted as its Cr(CO)5-adduct 13a. Analogously the ring compounds (η5-C5Me5)(CO)2Ru—P]2(As-Aryl)(7b) and (η5-C5Me5)(CO)2Ru—P(As-Aryl)2 (8b) are obtained by treatment of (η5-C5Me5)(CO)2Ru—P(SiMe3)2 (1b) with 6. Here again the primarily generated arsaphosphene has to be stabilized by coordination to Cr(CO)5 which gave E-(η5-C5Me5)(CO)2Ru—P[Cr(CO)5 = As-Aryl (E-13b) and its Z-isomer (Z-13b). A comparable reaction sequence furnished the phosphaarsenyl complex (η5-C5Me5)(CO)(PPh)3Fe—P[Cr(CO)5] = As-Aryl (13c).The molecular structures of 7a and 9a were elucidated by x-ray diffraction analysis. The most interesting feature of 7a is the AsP2-triangle, in which the As—P(2) bond length (235,0(2) pm) is slightly elongated with respect to the As—P(1) distance (231,6(1) pm). This effect is presumably due to severe steric interactions at the cis-substituted As—P(2) bond. Molecule 9a displays the picture of a bended 1,2-diphospha-3,4-diarsetane (interplanar angle 137.6°) with its substituents in the all trans-orientation. The As—P and P—P separations are normal whereas the As—As bond (249,7(4) pm) is slightly widened with respect to the calculated value for a single bond (ca 244 pm).
    Notes: Bei der Umsetzung von (η5-C5Me5)(CO)2Fe—P(SiMe3)2 (1a) mit 2,4,6-t-Bu3C6H2AsCl2 (= Aryl AsCl2) (6) werden die Heterocyclen [(η5-C5Me5)(CO)2Fe—P]2 As-Aryl (7a), (η5-C5Me5)(CO)2Fe—P(As-Aryl)2 (8a) und [(η5-C5Me5)(CO)2Fe—P]-As-Aryl(2 9a) erhalten. Der nur in Lösung nachweisbare Arsaphosphenylkomplex [(η5-C5Me5)(CO)2Fe—P=As-Aryl] läßt sich als stabiles Cr(CO)5-Addukt 13a abfangen. Analog bilden sich aus (η5-C5Me5)(CO)2Ru—P(SiMe3)2 (1b) und 6 die Ringe [(η5-C5Me5)(CO)2Ru—P]2As-Aryl (7b) und (η5-C5Me5)(CO)2Ru—P(As-Aryl)2 (8b). Auch hier kann ein primär entstandenes Arsaphosphen in Form der Cr(CO)5-Addukte.E-(η5-C5Me5)(CO)2Ru—P[Cr(CO)5] = As-Aryl (E-13b) und dessen Z-Isomer (Z-13b) abgefangen werden. Die gleiche Reaktionssequenz führt zu dem Phosphaarsenylkomplex (η5-C5Me5)(CO)(PPh3Fe)—P[Cr(CO)5] = As-Aryl (13c).Die Strukturen der Ringverbindungen 7a und 9a wurde mittels Röntgenbeugungsanalyse bestimmt. Das Grundgerüst von 7a besteht aus einem AsP2-Dreieck, in dem die As—P(2)-Bindung (235,0(2)pm) mit den Substituenten in cis-Orientierung gegenüber dem As—P(1)-Abstand (231,6(1)pm) geringfügig verlängert ist. Das Molekül 9a zeigt das Bild eines gefalteten 1,2-Diphospha-3,4-diarsetans (Diederwinkel 137,6°) mit den Substituenten in all-trans Orientierung. Der As—As-Abstand (249,7(4) pm) erscheint aufgrund sterischer Spannungen aufgeweitet (dber etwa 244 pm), während die As—P- und P—P-Abstände keine Besonderheiten aufweisen.
    Additional Material: 2 Ill.
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  • 6
    Electronic Resource
    Electronic Resource
    Springer
    Journal of materials science 12 (1977), S. 1981-1987 
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The phase diagram of the system NiO-WO3 was established by means of differential thermal analysis (DTA) supported by photoemission electron microscopy (PhEEM) and X-ray diffraction (XRD). The only compound, NiWO4, melts incongruently (peritectic decomposition) at 1420° C and forms a eutectic with WO3 at 73 mol % WO3 and 1245° C. Primary phase crystallization as well as eutectic and peritectic solidification were studied by the comparison of the DTA measurements and the phase intergrowth morphologies as observed by PhEEM. The experimental liquidus lines are briefly discussed with reference to the calculated values.
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  • 7
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract By means of photo-emission electron microscopy, which is described briefly, X-ray diffraction and electron microprobe analysis the hypo- and hypereutectic solidification in the system Zn2SiO4-SiO2 has been investigated. Faceted (idiomorphic) growth of stableα− and metastableΒ-zinc silicate with some excess SiO2 on the hypoeutectic side of the phase diagram and a metastable region of liquid immiscibility on the SiO2-rich (hypereutectic) side determine the respective phase intergrowth morphologies. Unconstrained eutectic solidification causes a “divorced eutectic” where the zinc silicate constituent grows first from the undercooled liquid, which is simultaneously enriched in SiO2.
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  • 8
    ISSN: 1573-5117
    Keywords: Crustacea ; Majidae ; allozymes ; gene flow ; larval dispersal ; Inachus ; Hyas
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The spider crabs Inachus dorsettensis (Pennant) and Hyas coarctatus Leach are widespread in subtidal areas of muddy sand or gravel around western Europe. Both species have a life cycle with an obligatory planktonic larval phase of several weeks, which might be expected to cause widespread larval dispersal and consequent genetic homogeneity over considerable distances. However, earlier work on both taxa has indicated differences in growth pattern between populations separated by tens of kilometres. This study was undertaken to determine whether these differences were purely environmental or whether, despite the short distances involved, differences may have a genetic basis. A study of gene frequencies, as indicated by allozymes in samples of adults collected off the Isle of Man (northern Irish Sea), indicates significant genetic differentiation between populations over a geographical distance of only about 40 km in both Inachus dorsettensis (θ = 0.086 ± 0.048) and Hyas coarctatus (θ = 0.023 ± 0.017). Variability measures differed between species, showing I. dorsettensis to have a mean number of alleles per locus of 2.5–2.6 and a range of gene diversity of 0.216–0.241, while H. coarctatus showed lower values of mean number of alleles (1.9–2.0) and a range of gene diversity from 0.122 to 0.124. Given the high expected larval mobility of the two species the results are most surprising. Possible explanations are discussed in relation to population discontinuities and patterns of larval drift.
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  • 9
    ISSN: 1573-5117
    Keywords: Portunidae ; population genetics ; gene flow ; allozymes ; estuarine retention
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The population genetic structure of the swimming crab Callinectes danae (Crustacea, Portunidae) was studied by allozyme electrophoresis along the southern coast of Brazil (Santa Catarina and Rio Grande do Sul States). The biology of C. danae is poorly known, but some studies suggest that this species depends on estuaries for reproduction and for completing its life cycle, using them as recruitment sites and nursery grounds. If estuarine retention is an important process acting in favour of the recruitment of local populations, we should expect restriction of gene flow among populations inhabiting different estuaries. Therefore, our aim was to establish whether gene flow between populations of C. danaefrom different estuaries was restricted. Samples were collected in four estuaries: São Francisco do Sul, Laguna (Santa Catarina), Patos Lagoon and Chuí Stream (Rio Grande do Sul). Eleven loci were resolved. Contingency table tests (χ2 and G) showed significant differences (P≤0.05) between pair-wise subpopulation comparisons. The estimated F ST was θ=0.065±0.019, suggesting a moderate structuring of C. danae populations. No relationship was found for the number of migrants between pairs of subpopulations and the geographic distance separating them (P= 0.292; r 2= 0.269). Nevertheless, UPGMA analysis clustered together those estuaries separated by less than 250 km. Low adult migration, the requirement of estuaries as reproductive areas, recruitment sites and nursery grounds for juveniles, together with larval and post-larval retention processes, are discussed in the context of their importance in preventing panmixia among subpopulations inhabiting different estuaries.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Colloid & polymer science 50 (1930), S. 197-199 
    ISSN: 1435-1536
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Zusammenfassung Saugt man in eine Kapillarröhre oberflächenaktive bzw. oberflächeninaktive Stoffe auf und läßt sie nach kurzer Zeit wieder ausfließen, so erhält man durch stalagmometrische oder titrimetrische Messungen Werte für die Dicken der an der Kapillarwand haftengebliebenen Wandschichten, die in der Größenordnung von 10−4 cm liegen. Etwa gleiche Schichtdicken sind von Bartsch bei der Adsorption von Oelsäure an Erzen, von l'rillat bei Schmiermittelfilmen auf Metalloberflächen mittels Röntgenstrahlen, von Hardy an ebensolchen Filmen zwischen einer Platte und einem Zylinder mittels Mikrometer und von Tausz und Dreifuß zwischen Metallplatten durch elektrische Messungen gefunden worden.
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