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  • 1
    Electronic Resource
    Electronic Resource
    Variations in polymer fitness at elevated mutation rates (1991)
    Springer
    Bulletin of mathematical biology 53 (1991), S. 751-768 
    Details
    ISSN: 1522-9602
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Mathematics
    Notes: Abstract Two series expressions were obtained that give the first and second order rates of change in population fitness during competitive replication at elevated mutation rates. At their zeroerror limit, the respective power series reduces to the second (Fisher’s theorem) and third moments of the fitness distribution. The first series maximized the variation in mean polymer fitness, for a given amount of population covariance. From experimental results reported by Spiegelman’s group on evolutionin vitro among Qβ RNA variants, it was demonstrated: (i) terms in the (second) series fall-off at a rate broadly equal to the replicase error (ε≅10−4); (ii) the rate of change in mean RNA fitness (polymer formation rate constant) corresponds to the variance in fitness; and (iii) agreement exists between second order rate changes in fitness and the third moment (skewness) regression line, extending over 20 successive replication reactions. The impact of these findings on the standard model of evolution has been discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02461552
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  • 2
    Electronic Resource
    Electronic Resource
    A computer model for estimating the response of sprinkler links to compartment fires with draft curtains and fusible link-actuated ceiling vents (1991)
    Springer
    Fire technology 27 (1991), S. 113-127 
    Details
    ISSN: 1572-8099
    Keywords: Fire scenario computer program ; fusible links ; ceiling jets ; ceiling vents
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying
    Notes: Abstract A computer program, LAVENT, is now available which computes the heating of fusible links due to the presence of a ceiling jet imbedded in an upper layer. An important new feature in this program is that the two-dimensional structure of the ceiling jet is taken into account such that the location of the link beneath the ceiling plays a role in the response of the link. The links can be used to activate ceiling vents such that the effect of venting the upper layer on the ceiling jet may be studied. Additional applications would include the study of upper layer containment through the use of a combination of draft curtains and ceiling vents. The geometry modeled by the program is that of a large compartment enclosed by a combination of walls and draft curtains.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01470863
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of size, ellipticity and charge separation on the free energy of some aqueous bolaform electrolyte models (1991)
    Springer
    Journal of solution chemistry 20 (1991), S. 551-564 
    Details
    ISSN: 1572-8927
    Keywords: Bolaform ; electrolyte ; aqueous ; free energy ; charge separation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The free energy of some models of aqueous bolaform electrolytes have been calculated at the Debye-Hückel limiting law plus B 2 level of approximation. The repulsive forces are modeled by hard spheres or hard ellipsoids. The charges are placed either at the center of the sphere or at the foci of the ellipsoid. Parameters were chosen to approximate the size and shape of sodium and calcium p-benzenedisufonate and sodium 4,4′-biphenyldisulfonate. The results show that contrary to the standard explanations for the unusual properties of bolaform electrolytes, separating the charges has little effect on the excess free energy. It is also shown that changing from a sphere to an ellipse has little effect on the excess free energy. The most important determinates of the properties of these salts are the sizes of the ions. Agreement of the model calculations with experimental results is reasonable considering the simplicity of the models.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00647065
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  • 4
    Electronic Resource
    Electronic Resource
    Wacker oxidation catalysis in a supported aqueous phase (1991)
    Springer
    Catalysis letters 11 (1991), S. 129-136 
    Details
    ISSN: 1572-879X
    Keywords: Wacker oxidation catalysis ; supported aqueous phase ; (SAP) catalysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Adsorption of palladium (II) and copper (II) salts onto the controlled pore glass CPG-240, in the presence of water, yields a supported aqueous phase Wacker oxidation catalyst. Conversions of 1-heptene to 2-heptanone of up to 24% under batch conditions are observed. The activity and selectivity of the catalysts are sensitive to water content, oxygen pressure and temperature.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764078
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  • 5
    Electronic Resource
    Electronic Resource
    Immobilization of HRh(CO)(P(m-C6H4SO3Na)3)3 on an anion exchange resin for the hydroformylation of higher olefins (1991)
    Springer
    Catalysis letters 8 (1991), S. 209-214 
    Details
    ISSN: 1572-879X
    Keywords: Water soluble rhodium complex ; anion exchange resin catalyst support ; immobilization of rhodium complex
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The anion exchange resin Amberlyst, A-26, forms an efficient matrix for the immobilization of the water soluble complex, HRh(CO)(m-C6H4SO3Na)3)3. Catalysis proceeds in anhydrous alcohol solvents which allows the conversion of water insoluble olefins to aldehydes. Activities and selectivities are similar to both supported aqueous phase catalysts and to the neutral complex, HRh(CO)(PPh3)3 in non-aqueous solvents. The catalyst preparation minimizes the quantity of water in the supported catalyst; the lack of water is thought to be responsible for an increase in catalyst stability toward oxidation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00764118
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  • 6
    Electronic Resource
    Electronic Resource
    The effect of sulfate on the crystal structure of zirconia (1991)
    Springer
    Catalysis letters 9 (1991), S. 1-7 
    Details
    ISSN: 1572-879X
    Keywords: Zirconia catalyst ; sulfated zirconia ; crystal chemistry ; calcination
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zirconia can be prepared to produce either tetragonal phase or predominantly monoclinic phase upon calcination at 500 °C. The precursors for each phase of zirconias was treated with 1N H2SO4 to produce a sulfated material. The results reveal that sulfation causes the tetragonal phase to be formed for both types of zirconia contrary to the data before sulfation, and sulfation increases the crystallization exotherm by 150 °C.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00769074
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  • 7
    Electronic Resource
    Electronic Resource
    Reciprocity of growth functions of Coxeter groups (1991)
    Springer
    Geometriae dedicata 39 (1991), S. 373-378 
    Details
    ISSN: 1572-9168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract The growth series W(t) of a Coxeter system (W, S) is always a rational function. We prove that for a very general class of infinite Coxeter groups, this function satisfies W(t −1)=±W(t).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00150764
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  • 8
    Electronic Resource
    Electronic Resource
    Coxeter groups are almost convex (1991)
    Springer
    Geometriae dedicata 39 (1991), S. 55-57 
    Details
    ISSN: 1572-9168
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In [C] Cannon introduced the notion of ‘almost convexity’ for the Cayley graph of a finitely generated group. In this paper, we observe that standard facts about Coxeter groups imply that the Cayley graph associated to any Coxeter system is almost convex.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00147303
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  • 9
    Electronic Resource
    Electronic Resource
    Kinetics of rapid RNA evolution in vitro (1991)
    Springer
    Journal of molecular evolution 33 (1991), S. 343-356 
    Details
    ISSN: 1432-1432
    Keywords: Qβ RNA variants ; Ethidium resistance ; Heterogeneity ; Kinetics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A rapidly acquired partial resistance to the replicase antagonist, ethidium bromide (EB), seen by Spiegelman and coresearchers in Qβ RNA variants competitively replicating under defined conditions in vitro, reflected existence of a pool of mutant RNA molecules, preadapted to EB, and their cross-propagation from the pre-EB optimum species, MDV-1, and from other kindred variants, some of which remained undetected, according to this quantitative analysis of midivariant RNA replication kinetics. DNAlike features of their evolution, such as the cloning of variants from an MDV-1 subtype and a complicance with the fundamental theorem of natural selection, resulted from the suppression, both real and apparent, of intrinsic RNA heterogeneity through sampling and detection methods, and also by the ascendency of self-propagation over cross-propagation with advancement of a superior variant. The deficit in mean polymer fitness, compared with optimum levels, determines the lower limit of this heterogeneity. Stability conditions for frequency equilibrium and strategies for counteracting viral drug resistance have been considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02102865
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  • 10
    Electronic Resource
    Electronic Resource
    Organic matter and containment of uranium and fissiogenic isotopes at the Oklo natural reactors (1991)
    [s.l.] : Nature Publishing Group
    Nature 354 (1991), S. 472-475 
    Details
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] Small pockets of uranium ore at Oklo went critical 1,95F0± 30 Myr ago6, producing several natural fission reactors. Reactors 1-6 contain virtually no organic matter. Total energy production in these reactors was 16,500 MWyr. Roughly 6 tons of 235U fissioned; the total uranium ...
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/354472a0
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