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  • 1
    Electronic Resource
    Electronic Resource
    s.l. : American Chemical Society
    Journal of agricultural and food chemistry 43 (1995), S. 2702-2706 
    ISSN: 1520-5118
    Source: ACS Legacy Archives
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
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  • 2
    ISSN: 1476-4687
    Source: Nature Archives 1869 - 2009
    Topics: Biology , Chemistry and Pharmacology , Medicine , Natural Sciences in General , Physics
    Notes: [Auszug] The Redfield ratio of 106 carbon:16 nitrogen:1 phosphorus in marine phytoplankton is one of the foundations of ocean biogeochemistry, with applications in algal physiology, palaeoclimatology and global climate change. However, this ratio varies substantially in response to changes in algal ...
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  • 3
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 9 (1997), S. 2032-2044 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: Ignition in the laminar wake that forms at the trailing edge of a thin splitter plate separating two parallel streams of fuel and oxidizer is studied in the limit of large activation energy. The analysis presented covers ignition events ocurring in the Rott–Hakkinen and Goldstein regions, where self-similar solutions for the different frozen flow variables are available. Because of the strong exponential sensitivity of the reaction rate on the temperature, ignition becomes a self-accelerating phenomenon on the temperature increment that leads to a thermal runaway a finite distance downstream from the splitter plate. The dependence of the ignition distance on the values of the velocity and temperature gradients that exist at the trailing edge of the splitter plate is investigated. In particular, it is seen that, for sufficiently large values of the activation energy, the small temperature variations that exist across the wake must be taken into account in calculating the ignition distance. As the transverse gradient of temperature at the trailing edge increases, the reaction zone becomes thinner and migrates towards the hotter side of the mixing layer, where convection becomes the dominant transport mechanism, causing the thermal runaway distance to be determined in the first approximation by a convective-reactive balance across the thin reaction layer. Ignition in the wake when one of the streams is initially stagnant is also addressed. The character of the resulting solution is seen to depend strongly on the Lewis number of the reactant supplied by the colder stream, yielding three distinct ignition regimes that are analyzed separately. © 1997 American Institute of Physics.
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  • 4
    Electronic Resource
    Electronic Resource
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 13 (2001), S. 776-792 
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The dynamics of time-dependent, planar propagation of gaseous detonations is addressed on the basis of a three-step chemistry model that describes branched-chain processes. Relevant nondimensional parameters are the ratio of the heat release to the thermal enthalpy at the Neumann state, the nondimensional activation energies for the initiation and branching steps, the ratio of the branching time to the initiation time and the ratio of the branching time to the recombination time. The limit of strong overdrive is considered, in which pressure remains constant downstream from the leading shock in the first approximation, and the ratio of specific heats γ is taken to be near unity. A two-term expansion in the strong overdrive factor is introduced, and an integral equation is derived describing the nonlinear dynamics and exhibiting a bifurcation parameter, the reciprocal of the product of (γ−1), the nondimensional heat release and the nondimensional branching activation energy, with an acoustic correction. A stability analysis shows that, depending on values of the parameters, either the mode of lowest frequency or a mode of higher frequency may be most unstable. Numerical integrations exhibit different conditions under which oscillations die, low-frequency oscillations prevail, high-frequency oscillations prevail, highly nonlinear oscillations persist, or detonation failure occurs. This type of parametric analysis is feasible because of the relative simplicity of the model, which still is more realistic than a one-step, Arrhenius chemical approximation. In particular, by addressing the limit of slow radical recombination compared with branching, explicit results are derived for the critical value of the bifurcation parameter, involving the ratio of the recombination time to the induction time. The results help to clarify the general nature of one-dimensional detonation instability and provide simplifications that can be employed in efficiently relating gaseous detonation behavior to the true underlying chemistry. © 2001 American Institute of Physics.
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  • 5
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology reviews 23 (1999), S. 0 
    ISSN: 1574-6976
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: The adsorption of the two metal ions Cu and Zn in a single-component system by Cymodocea nodosa, a brown alga, under different pH conditions was investigated. The solution pH significantly affected the exhibited uptake, being maximum at a pH value of 4.5. Multi-component mixture biosorption in aqueous solutions is also reported. A comparison was made between the single-component saturation uptake and the multi-component uptakes. To evaluate the two-metal sorption system performance, simple isotherm curves had to be replaced by three-dimensional sorption isotherm surfaces. In order to describe the isotherm surfaces mathematically, three Langmuir-type models were evaluated. The isotherms indicate a competitive uptake with Cu being preferentially adsorbed. In addition, different tests were carried out to compare the process efficiency working continuously in small columns.
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  • 6
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    Madrid : Periodicals Archive Online (PAO)
    Estudios geográficos. 42:164 (1981:agosto) 257 
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  • 7
    ISSN: 1573-6857
    Keywords: HMG-box ; microbats ; SOX ; SOX30
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract SOX genes are a family of genes that encode for proteins which are characterised by the presence of a HMG-domain related to that of the mammalian sex-determining gene (SRY). By definition, the DNA binding domain of SOX genes is at least 50% identical to the 79 amino acid HMG domain of the SRY gene. We report here two HMG-box sequences from two microbat species (R. ferrumequinum and P. Pipistrellus) which were PCR amplified using a primer pair specific to the mouse Sry HMG-box. The high percentage of identity of this sequences with the human and mouse SOX30 HMG-box suggests that they are the SOX30 HMG-box for these two bat species.
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  • 8
    ISSN: 1573-1561
    Keywords: Synthesis ; antifungal ; Botrytis cinerea ; bioassay ; structure-activity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Analog compounds of the proposed intermediates of the biogenetic pathway to botrydial have been synthesized. These compounds were tested for their potential antifungal activity against the phytopathogenBotrytis cinerea. Our results showed a fungistatic effect of some compounds on mycelium growth. The most significant effect was exerted by 2-α-hydroxy-2,3-dihydro-1-epiprobotrydial, which inhibited growth ofB. cinerea. Some aspects of structure-activity relationships are discussed.
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  • 9
    ISSN: 1573-0840
    Keywords: Tsunami catalog ; precursors ; warning system ; public education ; risk assessment ; Mexico ; Mesoamerican subduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geography , Geosciences
    Notes: Abstract From an inspection of all tide gauge records for the western coast of Mexico over the last 37 years, a data base of all recorded tsunamis was made. Information on relevant historical events dating back two centuries, using newspaper archives, previous catalogs, and local witness interviews, was added to produce a catalog of tsunamis for the western coast of Mexico. A description of the 1932 Cuyutlán tsunami is given. This is considered to be the most destructive local tsunami which has ever occurred in the region for which historical accounts are available. It was preceded by two precursor events, a not uncommon occurrence in that zone. A summary of the generation and coastal effects from the 1985 Michoacán tsunamis is also given. These Michoacán tsunamis are the most recent local events in that zone. This information, and knowledge of local undersea faulting characteristics along the Mexican Pacific coast, leads to a clear differentiation of two zones of potential tsunami hazard: locally generated tsunamis south of the Rivera fracture, in the Cocos plate subsidence region, and remotely generated tsunamis north of this zone. Based on this zonation, two types of tsunami warning systems are proposed: real-time for the southern zone, and delayed-time for the northern. A description is provided of the Baja California Regional Tsunami Warning System that is presently operational in the northern zone. Several major industrial ports and tourist resort areas are located in the southern zone, and are therefore most vulnerable to local destructive tsunamis. Some of these sites represent important socioeconomic resources for Mexico, and have therefore been chosen for a vulnerability assessment and microzonation risk analysis. Land use patterns are identified, risks defined, and recommendations to minimize future tsunami impact are given. One case is illustrated.
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  • 10
    Electronic Resource
    Electronic Resource
    Springer
    Journal of engineering mathematics 31 (1997), S. 119-130 
    ISSN: 1573-2703
    Keywords: chain branching ; mixing layer ; ignition ; WKB
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Technology
    Notes: Abstract The chain-branching process leading to ignition in the hydrogen-air mixing layer is studied by application of a novel WKB-like method with a four-step reduced scheme adopted for the chemistry description. Attention is restricted to initial free-stream temperatures above the crossover temperature corresponding to the second explosion limit of H2-O2 mixtures, thereby causing three-body recombination reactions to be negligible in the ignition process. It is shown that the initiation reactions, responsible for the early radical buildup, cease being important when the radical mass fractions reach values of the order of the ratio of the characteristic branching time to the characteristic initiation time, a very small quantity at temperatures of practical interest. The autocatalytic character of the chain-branching reactions causes the radical concentrations to grow exponentially with downstream distance in the process that follows. It is shown that, because of the effect of radical diffusion, the radical growth rate is uniform across the mixing layer in the first approximation, with an exponent given by that of a premixed branching explosion evaluated at the location where the effective Damköhler number based on the flow velocity is maximum. This exponent, as well as the leading-order representation of the radical profiles, are easily obtained by the imposition of a bounded, nonoscillatory behavior on the solution.
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