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  • 1
    Electronic Resource
    Electronic Resource
    The Hamiltonian (p2+m2)1/2−α/r near the critical value αc=2/π (1997)
    College Park, Md. : American Institute of Physics (AIP)
    Journal of Mathematical Physics 38 (1997), S. 3997-4012 
    Details
    ISSN: 1089-7658
    Source: AIP Digital Archive
    Topics: Mathematics , Physics
    Notes: We elucidate the behavior of the operator (p2+m2)1/2−α/r near the critical value α=αc where it ceases to be bounded below, by obtaining a family H(z) of operators which is self-adjoint holomorphic in a domain including all real z〉−αc−αc′, and such that H(αc−α)(α≤αc) is just the operator (p2+m2)1/2−α/r or its Friedrich extension, while H(−αc−α)(αc′〈α〈αc) is another self-adjoint extension. The operators H(z) (z real) are shown to be positive, and to have only discrete spectrum below m. The eigenvalues are then analytic functions of αc−α near α=αc (and become the eigenvalues of a non-self-adjoint operator when α〉αc). We show that these eigenvalues cannot vanish, but that the lowest eigenvalue of H(−αc−α) goes to zero when α→αc′. The L〉0 eigenvalues are analytic in α at α=αc. © 1997 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.532106
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  • 2
    Electronic Resource
    Electronic Resource
    Diagrammatic solutions for hydraulic head moments in 1-D and 2-D bounded domains (1995)
    Springer
    Stochastic environmental research and risk assessment 9 (1995), S. 269-296 
    Details
    ISSN: 1436-3259
    Keywords: Stochastic analysis ; diagrams ; groundwater flow
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract We present a diagrammatic method for solving stochastic 1-D and 2-D steady-state flow equations in bounded domains. The diagrammatic method results in explicit solutions for the moments of the hydraulic head. This avoids certain numerical constraints encountered in realization-based methods. The diagrammatic technique also allows for the consideration of finite domains or large fluctuations, and is not restricted by distributional assumptions. The results of the method for 1-D and 2-D finite domains are compared with those obtained through a realization-based approach. Mean and variance of head are well reproduced for all log-conductivity variances inputted, including those larger than one. The diagrammatic results also compare favorably to hydraulic head moments derived by standard analytic methods requiring a linearized form of the flow equation.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01581729
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  • 3
    Electronic Resource
    Electronic Resource
    The Use of Carbon Substrate Utilization Patterns in Environmental and Ecological Microbiology (1998)
    Springer
    Microbial ecology 35 (1998), S. 103-115 
    Details
    ISSN: 1432-184X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Carbon substrate utilization patterns have found increasing use in environmental and ecological microbiology over the past five years. Ninety six-well microtiter plates containing various carbon substrates permit these patterns to be determined quickly, economically, and effectively. The use of these patterns to characterize and differentiate strains isolated from the environment has been very effective in providing information on the culturable fraction of the microbial community. Another approach involves the direct inoculation of natural samples into these microtiter plates; this approach has several fundamental problems. The inoculation of low cell densities into the wells means that the technique is a culture-based method in which the biases of enrichment culture may render the results unrepresentative of the native microbiota. The physiological state of the inoculated microbes may affect the kinetics and pattern of substrate utilization. As a measure of the functional diversity of microbial communities, this approach suffers because the tested substrates do not accurately represent the types of substrates present in ecosystems, and the metabolic redundancy of species implies that changes in the response may only crudely represent the actual microbial population dynamics. Therefore, although this approach can be used to determine whether environmental samples differ in their response patterns, it is unclear how it can be used to provide fundamental information on questions of microbial diversity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002489900065
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  • 4
    Electronic Resource
    Electronic Resource
    Physiological state of a microbial community in a biomass recycle reactor (1998)
    Springer
    Journal of industrial microbiology and biotechnology 20 (1998), S. 232-237 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: biodegradation; biomass recycle reactor; physiological state; graywater
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The transition in physiological state was investigated between a carbon-limited chemostat population and microbes growing very slowly in a biomass recycle reactor. The mixed microbial population was metabolizing a mixture of biopolymers and linear alkylbenzene sulfonate, formulated to represent the organic load in graywater. Biomass increased 30-fold during the first 14 days after a shift from chemostat to biomass recycle mode. The ratios of ATP and RNA to cell protein decreased over the first days but then remained constant. The specific rate of CO2 production by microbes in the reactor decreased 6-fold within 24 h after the shift, and respiratory potentials declined 2–3 fold during the first 7 days. Whereas chemostat cultures used equal proportions of organic carbon substrate for catabolism and anabolism, the proportion of organic substrate oxidized to CO2 rose from 62 to 82% over the first 8 days in a biomass recycle reactor, and eventually reached 100% as this reactor population exhibited no net growth. Biomass recycle populations removed from the system and subjected to a nutritional shift-up did not immediately initiate exponential growth. The physiological state of cells in the biomass recycle reactor may be distinct from those grown in batch or continuous culture, or from starved cells.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900518
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  • 5
    Electronic Resource
    Electronic Resource
    Microbial biodegradation of organic wastes containing surfactants in a continuous-flow reactor (1997)
    Springer
    Journal of industrial microbiology and biotechnology 18 (1997), S. 235-240 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: biodegradation; chemostat; physiological state; graywater; LAS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: In a continuous flow bioreactor seeded with microbes from municipal activated sludge, complete organic carbon oxidation of simulated graywater (wastewater produced in human residences, excluding toilet wastes) was achieved at dilution rates up to 0.36 h−1 in the presence of 64.1 μ M linear alkylbenzenesulfonate (LAS) L−1. At LAS concentrations of 187 μ M, the system functioned only at dilution rates up to 0.23 h−1, and the biomass yield was two-fold lower. There were physiological changes in the microbial communities under different operating conditions, as measured by specific contents of ATP and extracellular hydrolases as well as the respiratory potential of the biomass. LAS inhibited the activity of LAS-degrading microbes at 〉150  μ M LAS, and the activity of other microbes at 〉75 μ M LAS. Chemical analysis of graywater indicated that samples consisted primarily of biological polymers (proteins and polysaccharides) and lower concentrations of surfactants. Biological remediation of graywater is possible, although treatment efficiency is influenced by the operating conditions and wastestream composition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900375
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  • 6
    Electronic Resource
    Electronic Resource
    Prediction of neotropical tree and liana species richness from soil and climatic data (1995)
    Springer
    Biodiversity and conservation 4 (1995), S. 56-90 
    Details
    ISSN: 1572-9710
    Keywords: tropical forests ; species richness ; diversity ; rain ; soils
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present an analysis of local species richness in neotropical forests, based on a number of 0.1 ha samples of woody plants collected by the late Alwyn Gentry. For each of 69 forests, soils were analysed and climatic data were collated. Using transformed independent variables and interaction terms, multiple regression equations were developed that explained the greatest possible amount of variation in species richness, and the best equations were selected on the basis of regression diagnostics. The best models are presented for (a) all neotropical forests, (b) forests west of the Andes (transandean) and (c) east of the Andes (cisandean), and for various subsets based on elevation and annual rainfall. For the whole dataset, and for most subsets, annual rainfall and rainfall seasonality were the most important variables for explaining species richness. Soil variables were correlated with precipitation — drier forests have more nutrient-rich soils. After the inclusion of rainfall variables, available soil nutrient concentrations contributed little to explaining or accounting for additional variation in species numbers, indicating that tropical forest species richness is surprisingly independent of soil quality. The results are consistent with the hypothesis that plants in mature tropical forests may obtain nutrients through the process of direct cycling, in which mineral nutrients are extracted from litterfall before they enter the soil. The strong relationship between community species richness and rainfall patterns has implications for biodiversity conservation. Wet forests with an ample year-round moisture supply harbour the greatest number of woody plant species and should be a focus of conservation efforts.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00115314
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  • 7
    Electronic Resource
    Electronic Resource
    Determination of the CP violating phase γ by a sum over common decay modes toB s and $$\bar B_s $$ (1995)
    Springer
    The European physical journal 67 (1995), S. 251-260 
    Details
    ISSN: 1434-6052
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract To help the difficult determination of the angle γ of the unitarity triangle, Aleksan, Dunietz and Kayser have proposed the modes of the typeK − D s + , common toB s and $$\bar B_s $$ . We point out that it is possible to gain in statistics by a sum over all modes with ground state mesons in the final state, i.e.K − D s + ,K *− D s + ,K − D s *+ ,K * D s * . The delicate point is the relative phase of these different contributions to the dilution factorD of the time dependent asymmetry. Each contribution toD is proportional to a product $$F^{cb} F^{ub} f_{D_s } f_K $$ whereF denotes form factors andf decay constants. Within a definite phase convention (i.e. for example the one defined by the heavy quark symmetry in the limit of heavy quarks), lattice calculations do not show any change in sign when extrapolating to light quarks the form factors and decay constants. Then, we can show that all modes contribute constructively to the dilution factor, except theP-waveK * D s *+ , which is small. Quark model arguments based on wave function overlaps also confirm this stability in sign. By summing over all these models we find a gain of a factor 6 in statistics relatively toK − D s + . The dilution factor for the sumD tot is remarkably stable for theoretical schemes that are not in very strong conflict with data onB→ψK(K *) or extrapolated from semileptonic charm form factors, givingD tot≥0.6, always close toD(K − D s + ).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01571286
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