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  • Chemistry  (10)
  • potato  (2)
  • Key words Saguaro  (1)
  • PACS. 62.65.+k Acoustical properties of solids  (1)
  • 2000-2004  (2)
  • 1990-1994  (9)
  • 1970-1974  (3)
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Keywords
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Year
  • 1
    Electronic Resource
    Electronic Resource
    Elastic properties of ferromagnetic EuB 6 (2001)
    Springer
    The European physical journal 22 (2001), S. 327-333 
    Details
    ISSN: 1434-6036
    Keywords: PACS. 62.65.+k Acoustical properties of solids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: Results of an ultrasonic investigation of EuB6 at low temperatures are reported. Both longitudinal and transverse acoustic modes exhibit anomalies in the vicinity of the low-temperature phase transitions of EuB6. The ultrasound data serve to establish part of the B-T phase diagram of EuB6. At magnetic fields exceeding 3 T, magneto-acoustic quantum oscillations (MAQO) are observed. The nature of the acoustic anomalies and possible phases in external magnetic fields are discussed. Also a comparison with the elastic properties of other rare-earth (RE) hexaboride compounds is made.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01312802
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  • 2
    Electronic Resource
    Electronic Resource
    Use of saguaro fruit by white-winged doves: isotopic evidence of a tight ecological association (2000)
    Springer
    Oecologia 124 (2000), S. 536-543 
    Details
    ISSN: 1432-1939
    Keywords: Key words Saguaro ; Carnegiea gigantea ; Stable isotope ratios ; Resource use ; Zenaida asiatica mearnsii
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  We report the use of stable isotope and crop content analyses to quantify the use of saguaro (Carnegiea gigantea) nectar and fruit by migratory desert white-winged doves (Zenaida asiatica mearsnii). Saguaro resources had characteristically 13C-enriched CAM values (δ13C=–12.8±0.7‰ SD VPDB and –13.1±0.5‰ SD VPDB for nectar and fruit, respectively) relative to other food plants used by doves (δ13CC3=–24.9±3.3‰ SD VPDB). The water contained in saguaro nectar and fruit was deuterium enriched (δD=19.6±2.0‰ SD VSMOW and 48.4±1.6‰ SD VSMOW for nectar and fruit, respectively) relative to other water sources (ranging from –41 to –19‰ VSMOW). During the fruiting season, there was a positive correlation between δ13C in dove liver tissues and percent of saguaro in crop contents. A two-point mixing model indicated that during the peak of saguaro fruit use, most of the carbon incorporated in dove tissues was from saguaro. Desert white-winged doves appear to be saguaro specialists. Averaged over the period when doves were resident, saguaro comprised about 60% of the total carbon incorporated into dove tissues. Tissue δ13C and δD of body water showed a significant positive correlation, indicating that doves were using saguaro as a source of both nutrients and water. However, at the peak of saguaro utilization, the doves’ body-water δD was more positive (by about 20‰) than saguaro fruit water. We hypothesize that this enrichment is due to fractionated evaporative water losses by doves. Using dove carbon isotope data and a two end-point mixing model we estimate that, on average, doves consume the equivalent of 128 saguaro fruits per season; each fruit contains on average 26.0±14.8 g SD of pulp (wet mass) of which 19.4 g is water. Stable isotopes have been used to produce qualitative re-constructions of animal diets. Our study shows that they can be used to provide quantitative estimates of the flow of nutrients from resources into consumers as well.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004420000406
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  • 3
    Electronic Resource
    Electronic Resource
    Presence of a transposon-like element in the promoter region of an inactive patatin gene in Solanum tuberosum L. (1990)
    Springer
    Plant molecular biology 14 (1990), S. 239-247 
    Details
    ISSN: 1573-5028
    Keywords: patatin ; potato ; transposon ; gene inactivation ; β-glucuronidase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The promoter of the PGT3 patatin gene belonging to the class II subfamily is highly homologous to other class II patatin genes except for a 736 bp insertion in front of the putative transcription start site. The insertion is characterized by structural features resembling a transposable element such as an 11 bp inverted repeat at the termini and an 8 bp duplication flanking the insertion site. Despite the high homology to active patatin genes, fusion of its promoter to the β-glucuronidase reporter gene does not lead to detectable β-glucuronidase (GUS) activity in transgenic potato or tobacco plants, suggesting that the inactivation of this gene might be caused by the insertion of the transposon like element.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00018564
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  • 4
    Electronic Resource
    Electronic Resource
    A detailed study of the regulation and evolution of the two classes of patatin genes in Solanum tuberosum L. (1991)
    Springer
    Plant molecular biology 17 (1991), S. 1139-1154 
    Details
    ISSN: 1573-5028
    Keywords: patatin ; promoter ; β-glucuronidase ; potato
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The class-specific expression of patatin genes was investigated by analysing four new patatin genes. A class I patatin gene from cv. Berolina as well as a class I and two class II patatin genes from the monohaploid cultivar AM 80/5793 were isolated and partially sequenced. Sequence comparison indicates rearrangements as the major source for the generation of diversity between the different members of the classes. The expression of single genes was studied in potato plants transformed with chimaeric genes where the putative patatin promoters were fused to the GUS reporter gene. A detailed histochemical analysis reveals that both class I genes are expressed as the previously described class I patatin gene B33 from cv. Berolina [1], i.e. in the starch-containing cells of potato tubers and in sucrose-induced leaves. The class II gene pgT12 shows the same pattern as the previously described class II gene pgT2 [2], i.e. expression in root tips and in the vascular tissue of tubers, whereas no activity was detectable for pgT4. Thus the expression pattern of both classes of genes seems to be stable at least within or even between different cultivars.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00028731
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  • 5
    Electronic Resource
    Electronic Resource
    Large scale fractionation of polyethylene by means of the continuous polymer fractionation (CPF) methodAffectionately dedicated to Prof. W. Burchard on the occasion of his 60th birthday (1990)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 191 (1990), S. 659-670 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The countercurrent extraction method recently developed for the continuous polymer fractionation (CPF) was applied to linear polyethylene (M̄w = 55 kg/mol; M̄n = 16,7 kg/mol). At temperatures higher than 130°C, moderately concentrated solution of polyethylene were extracted to remove the low-molecular-weight components. Discontinuous fractionation experiments served to detect the best suited solvents. Diphenyl ether was chosen to demonstrate that the present extraction can be performed even with the same single solvent used to prepare the feed. For very high-molecular-weight polymers, mixed solvents are, however, normally better than single ones, since they allow an easier tailoring of thermodynamic conditions, and yield much less viscous solutions. Mixtures of tetralin and triethylene glycol turned out to be best suited for polyethylene. By means of four successive CPF runs with the single solvent, polyethylene fractions with non-uniformities U = (M̄w/M̄n) - 1 of approx. 0,3 to 0,4 were obtained on a 100 g scale. The rule of thumb that U can be halved in each CPF step without extensive optimization of the method was corroborated.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1990.021910321
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  • 6
    Electronic Resource
    Electronic Resource
    Intramolecular interaction of chain molecules: Second osmotic virial coefficients and intrinsic vicosities (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1491-1504 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: In a new theoretical approach the separation of a pair of chain molecules (measured thermodynamically by the second osmotic virial coefficient A2) is treated as a two-step process: In the first step the molecules are detached from each other by the addition of solvent - keeping their dimensions constant - and in the second step the now isolated coils are allowed to relax into their equilibrium dimensions. For the description of the second step, in which only segments belonging to one molecule take part, an intra-molecular interaction parameter is introduced on the basis of the intrinsic viscosity. The present two-parameter approach yields A2 = A2∞ + σ M-(1-a) for the dependence of A2 on the molecular weight M of the polymer; a is the exponent of the Kuhn-Mark-Houwink equation and σ a parameter measuring the effects associated with the second step (becoming zero if the coil dimensions do not depend on polymer concentration). A test of the above relation by means of published material demonstrates its superiority over other two parameter theories: It can describe the actually measured A2(M) well down into the region of oligomers without an additional parameter and it comprises the conceptual advantage of explaining experimental observations concerning ∂A2/∂M 〉 0 or ∂A2/∂M ≈ 0 for high A2 values.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940523
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  • 7
    Electronic Resource
    Electronic Resource
    Pressure dependence of viscometric relaxation times measured with a new apparatus. Williams-Landel-Ferry behaviour of moderately concentrated solutions of poly(butyl methacrylate)s in 2-propanol (1991)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 192 (1991), S. 165-176 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: A new rotational viscometer is presented which can be operated up to 2 000 bar and a maximum shear stress of 420 Pa. It allows, for the first time, to investigate the non-Newtonian flow behaviour of moderately concentrated polymer solutions. Results of measurements with two representatives of the system 2-propanol/poly(butyl methacrylate) with weight-average molecular weights M̄w = 520 000 and M̄w = 2 050 000, and ratios of weight- to number-average molecular weights M̄w/M̄n = 1,08 and M̄w/M̄w = 1,23, resp. in the region of moderate polymer concentrations are reported. For a ca. 7 wt.-% solution of the higher-molecular-weight polymer one obtains viscometric relaxation times τ0 varying from 1 to 100 ms in the region from 1 to 2 000 bar and from 40 to 75°C; at the lower temperature the application of p can raise τ0 by one order of magnitude. The steady-state shear compliance (proportional to τ0/η0, where η0 is the zero-shear viscosity), is independent of pressure of varies only slightly. For the present system, which gels thermoreversibly upon cooling, η0 and τ0 as a function of temperature and pressure can be well represented by the Williams-Landel-Ferry equation.
    Additional Material: 12 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1991.021920115
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  • 8
    Electronic Resource
    Electronic Resource
    True cosolvency. Acetone/diethylether/polystyrene (1973)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 173 (1973), S. 241-245 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1973.021730118
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  • 9
    Electronic Resource
    Electronic Resource
    Pressure and solvent influences on the shear thinning behavior of moderately concentrated solutions of poly(butyl methacrylate) (1993)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 194 (1993), S. 1387-1395 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The viscosities of moderately concentrated solutions of poly(butyl methacrylate) - M̄w = 1820 kg/mol-in the thermodynamically good solvent toluene and in the theta solvent 2-propanol were measured up to pressures of 2000 bar as a function of shear rate \documentclass{article}\pagestyle{empty}\begin{document}$ \dot \gamma $\end{document} in the temperature interval from 40 to 70°C. Both systems obey Graessley's equation so that it is possible to obtain the following rheological parameters in addition to the zero-shear viscosity η0 from the dependences \documentclass{article}\pagestyle{empty}\begin{document}$ \eta (\dot \gamma ) $\end{document}. η can be split into an entanglement part ηent plus a frictional contribution ηfric, and the characteristic viscometric relaxation time τ0 becomes accessible. The present results demonstrate that the application of pressure raises the above parameters much less for good than for bad solvents. In contrast to ηfric (which can react differently to the application of pressure due to special circumstances) η0 and τ0 are always influenced to the same degree as T or p are changed. This result implies that the steady state shear compliance (τ0/η0) is independent of the variables of state irrespective of the thermodynamic quality of the solvent. For the good solvent the effects of temperature can be described by the Arrhenius equation, whereas the WLF equation has to be used for the bad one.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1993.021940513
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  • 10
    Electronic Resource
    Electronic Resource
    Shear influence on the phase separation of oligomer blends (1994)
    Weinheim : Wiley-Blackwell
    Macromolecular Chemistry and Physics 195 (1994), S. 1257-1271 
    Details
    ISSN: 1022-1352
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Shear influences on the phase separation behaviour of four different blends of ethylene glycol/propylene glycol oligomers, exhibiting upper critical solution temperatures, were investigated. Cloud point curves at rest (turbidity measurements) are reported for all systems, spinodal conditions (light scattering) and tie-lines (analysis of the coexisting phases) are given for some examples. Phase diagrams under shear were obtained from rheological data. They demonstrate that the demixing temperatures of systems where both glycols bear OH end-groups are lowered up to ca. 1°C by shear rates of 1000s-1; the critical composition, generalized to the non-equilibrium conditions of flow, is markedly shifted. These observations are explained in terms of the generalized Gibbs energy (containing the mechanical energy the system stores during flow) as a consequence of the strongly interacting end-groups of the glycols. This interpretation is backed by the fact that the shear effects disappear when the glycols are methylated.
    Additional Material: 13 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1994.021950412
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