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  • Chemistry  (64)
  • Structured Biological Modelling  (2)
  • Antisense repression  (1)
  • Carnegiea gigantea  (1)
  • 11
    Electronic Resource
    Electronic Resource
    Über die Tieftemperaturform von K3NO3 (1983)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 502 (1983), S. 153-157 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: On Low-temperature K3NO3Low-temperature Guinier photographs (+20 ← -140°C) indicate a reversible phase-transition at -42°C. From X-ray powder data a structural model based on ordered NO2- groups has been derived (I4cm, a = 726.9(1), c = 1046.3(2) pm).
    Notes: Tieftemperatur-Guinieraufnahmen (+20 ← -140°C) von K3NO3 zeigen eine reversible Phasentransformation bei -42°C an. Aus den Röntgenpulverdaten wird ein Strukturvorschlag abgeleitet (I4cm, a = 726,9(1), c = 1046,3(2) pm), der geordnete NO2--Anionen aufweist.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19835020719
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  • 12
    Electronic Resource
    Electronic Resource
    K3NO3, Darstellung und StrukturuntersuchungenProfessor Harald Schäfer zum 70. Geburtstage am 10. Februar 1983 gewidmet (1983)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 497 (1983), S. 65-69 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Preparation and Structural Investigation of K3NO3Synthesis and crystal growth of K3NO3 is described. At room temperature K3NO3 is cubic (a = 521.4 pm, Pm3m) and crystallizes corresponding to the formula (NO2)OK3 in the perovskite-type of structure (diffractometerdata, R = 5.5%).
    Notes: Es wird die Darstellung und Einkristallzüchtung von K3NO3 beschrieben. Bei Zimmertemperatur ist K3NO3 kubisch (a = 521,4 pm, Pm3m) und besitzt gemäß (NO2)OK3 Perowskitstruktur (Diffraktometerdaten, R = 5,5%).
    Additional Material: 3 Tab.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19834970206
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  • 13
    Electronic Resource
    Electronic Resource
    Sedimentation of dissolved macromolecules in the terrestrial gravitational field near the critical locus (1972)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 161 (1972), S. 277-284 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: Die vorliegende Arbeit zeigt sowohl theoretisch als auch experimentell, daß das Schwerefeld der Erde unter annähernd kritischen Bedingungen ausgeprägte Veränderungen in der Gleichgewichtskonzentration von gelösten Makromolekülen mit der Höhe hervorruft.So wurde für das System Polystyrol/Cyclohexan beobachtet, daß die Gleichgewichtskonzentration unter derartigen Bedingungen am Boden eines Gefäßes etwa das Dreifache beträgt wie in 10 cm Höhe. Im Falle polymolekularer Proben ist die Sedimentation von einer entsprechenden Fraktionierung begleitet.
    Notes: The present paper demonstrates theoretically as well as experimentally, that the gravitational field of the earth produces very pronounced changes in the equilibrium concentration of dissolved macromolecules with height, under near critical conditions.Thus it could be observed for the system polystyrene/cyclohexane that the equilibrium concentration at the bottom of a tube is approximately three times that at a height of 10 cm, under such conditions. In the case of polymolecular samples the sedimentation is associated with a corresponding fractionation.
    Additional Material: 3 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1972.021610120
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  • 14
    Electronic Resource
    Electronic Resource
    Die viskosität von polymerlösungen in der nähe von oberen und unteren entmischungstemperaturen (1977)
    Weinheim : Wiley-Blackwell
    Angewandte Makromolekulare Chemie 57 (1977), S. 15-27 
    Details
    ISSN: 0003-3146
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Description / Table of Contents: The viscosity of liquid mixtures exhibits a characteristic temperature dependence near the consolute point. For polymer solutions this phenomenon is well studied in the case of upper critical solution temperatures, whereas no such measurements exist in the vicinity of lower critical solution temperatures.Viscosity measurements were performed for the system cyclohexane/polystyrene (upper critical solution temperature) and for the system orthotrimethylformiate/diethylether/polystyrene (lower critical solution temperature). For the former system qualitative agreement with. the results of Debye and coworkers was found. The investigations in the vicinity of the lower critical solution temperatures also disclosed that an additional function is superimposed to the normal temperature dependence of the viscosity which leads to an increase in viscosity before demixing sets in. This behaviour can be described by an equation analogous to that used for lower solubility gaps.
    Notes: Die Viskosität flüssiger Mischungen zeigt in der Nähe des kritischen Entmischungspunktes eine charakteristische Temperaturabhängigkeit. für Polymerlösungen ist diese Erscheinung bei der oberen kritischen Entmischungstemperatur gut untersucht, während in der Umgebung der unteren kritischen Entmischungstemperatur keine derartigen Messungen vorliegen.ES wurden Viskositätsmessungen im System Cyclohexan/Polystyrol (obere kritische Entmischungstemperatur) und im System Orthotrimethylformiat/Diäthyläther/Polystyrol (untere kritische Entmischungstemperatur) durchgeführt. Beim ersten System ergab sich qualitative Übereinstimmung mit den Ergebnissen von Debye und Mitarbeitern. Die Untersuchungen in der Umgebung der unteren kritischen Entmischungstemperatur zeigten, daß auch hier dem normalen Viskositäts-Temperaturverlauf eine zusätzliche Funktion überlagert ist, die zu einem Viskositätsanstieg vor Eintritt der Entmischung führt. Dieses Verhalten läßt sich mit einer analogen Gleichung beschreiben, wie sie für untere Mischungslücken verwendet wurde.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/apmc.1977.050570102
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  • 15
    Electronic Resource
    Electronic Resource
    Measured and calculated solubility of polymers in mixed solvents: Co-nonsolvencyDedicated to Professor Dr. J. W. Breitenbach in honor of his 70th birthdayAfter submission of this paper Professor Dr. J. W. Breitenbach deceased on 6. 1. 1978. (1978)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 179 (1978), S. 2265-2277 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The phenomenon of co-nonsolvency, i.e. the formation of nonsolvents by mixing two solvents, was studied for the system N,N-dimethylformamide/cyclohexane/polystyrene (DMF/CH/PS) which is characterized by the fact that the components of the mixed solvent are only incompletely miscible below 48,6°C. A number of quasibinary sections (stepwise addition of the second solvent to given solutions of the polymer in the first solvent) for a sample (M = 110000) of high molecular uniformity yielded a cloud point surface which gives “island curves” (closed solubility gaps) for constant temperatures between the critical temperature of DMF/CH and the top of the cloud point surface (51,3°C). The attainment of equilibrium is facilitated by the addition of DMF to CH or solutions of PS in CH, as compared with the opposite procedure. By means of phase equilibrium experiments tie lines and the critical curve could also be constructed. For a theoretical calculation of the latter from information concerning the binary sub-systems (e.g. light scattering of PS in DMF) the single liquid approximation was applied to DMF/PS instead of - with respect to miscibility - the more dissimilar DMF/CH; the results are in qualitative accord with experimental observations. Orienting measurements concering the chain length dependence of the partition coefficient in co-nonsolvent systems indicate that their aptitude for fractionation is considerably worse than that of normal systems under comparable conditions.
    Additional Material: 11 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1978.021790914
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  • 16
    Electronic Resource
    Electronic Resource
    Oligomer-oligomer incompatibility, 2Part 1: cf. ref.1. Oligo(dimethylsiloxane)/oligo(propylene glycol)Dedicated to Professor G. Meyerhoff on the occasion of his 60th birthday (1979)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 180 (1979), S. 2591-2603 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: The demixing behavior of 20 representatives of the system oligo(dimethylsiloxane)/oligo(propylene glycol) (ODMS/OPG)The prefix “oligo” has been chosen for all products, since the addition or removal of a few monomeric units changes the physical properties considerably (cf. Tab. I), even in the case of the highest molecular weight sample. is investigated at pressures up to 1 500 bar. The degrees of oligomerization range from 2 to 5 for the first and from 1 to 57, 6 for the second component. The experimental results are compared with those for the previously studied system oligoisobutene/oligo(propylene glycol) (OIB/OPG). In both cases the observed upper critical temperatures Tc increase with the number of monomeric units of the less polar component, whereas they run through a minimum when the number of monomeric units of the glycol is raised. For the present system the Tc values are found to be considerably higher than that of OIB/OPG and the optimum compatibility can normally be observed already between 1 and 7 propylene glycol units as against 50 in the case of OIB/OPG. In the low pressure region Tc of ODMS/OPG is decreased by pressure for all representatives of this system, while enhanced incompatibility has been found with OIB/OPG. For ODMS/OPG the special features of the critical lines are determined by the chain length of OPG, for OIB/OPG by that of OIB. For ODMS/OPG the initial reduction of Tc by pressure is most pronounced with the highest molecular weight oligo(propylene glycol), for which it amounts up to 0,3 K/bar; with increasing pressure and decreasing chain length the effects become smaller. For the lowest molecular weight sample of OPG the critical lines show a vertex at 700-1000 bar. In any case the two systems under consideration behave in an increasingly similar manner as the pressure is raised. The theoretical evaluation and discussion of the above results is performed by analogy with that of the first paper in this series.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1979.021801104
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  • 17
    Electronic Resource
    Electronic Resource
    Continuous fractionation and solution properties of PVC, 3Part 1, 2: cf. 1,2. Pressure dependence of the solubility in single solventsIn memoriam of Professor G. Rehage (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 769-776 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: From the break-down in the viscosity and from the increase of the intensity of the scattered light, associated with the entrance into the two-phase region, the pressure dependence of the demixing temperature of solutions of PVC 37 000, PVC 75 000 and PVC 100 000 in phenetole and PVC 75 000 in o-xylene was measured up to 1 000 bar. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) The application of pressure increases the demixing temperatures of PVC in both solvents by about 1 K/100 bar. For a qualitative forecast of the pressure effects, the solubility parameter theory in combination with the corresponding states principle, and an empirical correlation to the relative distance of the critical demixing temperature to the melting point of the pure solvent were used. The results of both concepts are in accord with the experimental findings.
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860409
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  • 18
    Electronic Resource
    Electronic Resource
    Continuous fractionation and solution properties of PVC, 4Part 1-3: cf. Refs.1-3. Pressure dependence of the solubility in a mixed solventDedicated to Professor K. J. Ivin in honour of his 60th birthday (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 777-785 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Using a self-constructed light scattering apparatus, the pressure dependence of the demixing temperature of solutions of PVC 20 000, PVC 37 000 and PVC 70 000 in THE/water was determined up to 1 000 bar for different compositions of the mixed solvent. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) In contrast to the thetasolvents o-xylene and phenetole, the solubility decreases with increasing pressure for all molecular weights and compositions under investigation typically by about 1 K/100 bar. The evaluation of the experimental findings demonstrates that the volume fraction of the nonsolvent in the mixed solvent, ϕ2*, is the variable that governs phase separation: For the present region of p and T, a given polymer solution demixes at a characteristic constant value of ϕ2*, no matter how it is reached. This fact allows the prediction of pressure influences from known pVT data of the pure components and measurements at atmospheric pressure. A qualitative theoretical understanding of the observed influences of p and T can be reached on the basis of the solubility parameter theory.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860410
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  • 19
    Electronic Resource
    Electronic Resource
    Continuous fractionation and solution properties of PVC, 5Part 1-4: cf. Refs.1-4. Pressure dependence of the viscosity  -  influence of solventDedicated to Professor J. Schurz in honour of his 60th birthday (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 787-799 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Viscosity measurements were carried out as a function of pressure and temperature with solutions of 8 wt.-% PVC (Mw ≈ 75 000) in ten thermodynamically good solvents by means of a Searle-type viscometer. A rollingxyhball viscometer was used for the investigation of the pure solvents. In all cases the viscosity increases in a more or less exponential manner when the pressure is raised. The viscosity ratio f1000 = η1000 bar/η1bar can be varied by the choice of the solvent from ca. 2 (tetrahydrofuran) to 3,0 (cyclohexanone) at 40°C. For a constant temperature of 40°C, the volumes of activation for the viscous flow of the solutions, V≠, or f1000 exceed that of the pure solvent, by typically 25%. The dependence of f1000 or V≠ upon temperature is not very pronounced. However, the greater the f1000-values, the more marked are the temperature effects. The theoretical analysis of the data, including earlier measurements with PS, indicates that three terms contribute to f1000: the basic value (f1000)s stemming from the pure solvent, the value (f1000)p which the polymer would contribute under athermal conditions, and finally a thermodynamic term, (f1000)pa, considering the pull-along effect (i.e. the specific forces a given segment exerts on other segments under variable thermodynamic conditions).
    Additional Material: 4 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860411
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  • 20
    Electronic Resource
    Electronic Resource
    Continuous fractionation and solution properties of PVC, 6Parts 1-5: cf. refs. 1-5. Pressure dependence of the viscosity  -  influence of molecular weight and compositionDedicated to Professor O. Fuchs in honour of his 80th birthday (1985)
    New York : Wiley-Blackwell
    Die Makromolekulare Chemie 186 (1985), S. 801-815 
    Details
    ISSN: 0025-116X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Viscosities were measured as a function of pressure and temperature with solutions of PVC 75 000 in cyclohexanone (CHO) and polymer contents ranging from 0,6 to 12 wt.-%, by means of a Searle-type (≥3 wt.-%) and a rolling-ball viscometer (〈3 wt.-%). Furthermore, the influence of molecular weight was determined with solutions of 8 wt.-% of PVC 20 000, PVC 37 000 and PVC 100 000. (The numbers in the codes of the PVC specimens are their approximate molecular weights.) For all concentrations and molecular weights, the viscosity increases in a more or less exponential manner with increasing pressure. The ratio f1000 of the viscosity of the solution at 1 000 and 1 bar can be varied by the change of the polymer content from 2,5 (the value of the pure solvent, index s) to 3,5 (12 wt.-% PVC 75 000) at t = 25°C and from 2,23 to 2,94 at t = 80°C. An increase of the molecular weight of the polymer raises f1000 in a similar manner as the polymer concentration. Using the reduced variables V≠/V≠ (ratio of the volumes of activation of the solution and the pure solvent) and c̃ (product of the polymer concentration and the intrinsic viscosity), all results obtained by variation of T, c and Mw can be represented by a master curve. This means that it is possible to calculate the pressure dependence of a given polymer solution of arbitrary polymer concentration from a mere measurement of the intrinsic viscosity at normal pressure. Criteria are presented which allow a forecast concerning the occurrence of minima in the concentration dependence of the energy of activation of the viscous flow E≠ and V≠.
    Additional Material: 10 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/macp.1985.021860412
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