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  • 1
    Electronic Resource
    Electronic Resource
    Bingley : Emerald
    Kybernetes 23 (1994), S. 86-103 
    ISSN: 0368-492X
    Source: Emerald Fulltext Archive Database 1994-2005
    Topics: Computer Science
    Notes: Proposes two tentative projects for ordering the scientific concepts in relation to a systemic theory of knowledge, based on cognitive sciences. It tries to develop some basic ideas of Wiener in the framework of modern physics. The concept of complementarity is extended to ideologies. Cybernetics, it is assumed, could have an important role in the transformation of conflicts into synergetic trends.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    Ground water 35 (1997), S. 0 
    ISSN: 1745-6584
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Energy, Environment Protection, Nuclear Power Engineering , Geosciences
    Notes: Chemical contamination of ground water is typically associated with multicomponent solutions of reactive substances, the mobility of which is affected by their reactivity. In predicting geochemical transport, it is therefore important that the liquid and solid phase reactions be modeled, along with the flow-controlled processes. This demanding task is typically carried out on powerful computers. Frequently, however, field data are available for a limited number of species, or, a small number of species suffices to characterize ground-water quality. In such cases it is desirable to be able to model the transport on a widely available class of inexpensive computers. We report on the development of a 2-D model for the transport of reactive species that runs efficiently on PCs. The model follows a modified one-step procedure that adopts total (aqueous and adsorbed) concentrations and aqueous concentrations of components, and accounts for aqueous complexation and for competitive sorption via isotherms or selectivity coefficients. The use of principal directions of transport coordinates, dimensional splitting, and a specialized algorithm for handling advection-dominated transport render it compact and efficient. Mass conservation is satisfied with high accuracy.
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  • 3
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: We investigated the precipitation of carbonates by Halobacillus trueperi in both solid and liquid media at different salt concentrations and different magnesium/calcium ratios. H. trueperi precipitated at all assayed salt concentrations. When salt concentration increased, the quantity and the size of bioliths decreased and the time required increased. The precipitated minerals (determined by X-ray diffraction) were calcite, magnesium calcite and monohydrocalcite in variable proportions depending on the salinity and the physical state of the medium; the magnesium content of the magnesium calcites also varied with regard to the culture type. According to the saturation indices other minerals could also precipitate. Scanning electron microscopy showed that dominant morphologies of the bioliths were spherulitic with fibrous radiated interiors. We show that H. trueperi plays an active role in the precipitation of carbonates and we hypothesize about this process of biomineralization.
    Type of Medium: Electronic Resource
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  • 4
    Electronic Resource
    Electronic Resource
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 13 (1994), S. 0 
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Abstract Calcium carbonate precipitation by 63 strains of moderately halophilic bacteria (Vibrio spp.) isolated from water of a saltern pond has been studied, taking into account the influence of salinity and temperature on the quantity and type of crystals precipitated. The bacteria formed crystals under all the conditions tested. All the crystals were magnesium calcite, with a variable Mg content, depending upon the medium provided. No aragonite was detected, even in a media with high Mg contents. Whether these microorganisms play an active role in precipitation is discussed, as well as the possibility that they may contribute to CaCO3 precipatation in their natural habitats.
    Type of Medium: Electronic Resource
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  • 5
    Electronic Resource
    Electronic Resource
    Springer
    Environmental monitoring and assessment 32 (1994), S. 161-186 
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract A model is presented for the description of the pump and treat (or flushing) remediation of the saturated zone with non-aqueous phase liquid (NAPL) present as droplets. Sensitivity analysis shows that the most important variables are the NAPL droplet size and the distance through which the dissolved organic compound must diffuse to reach the advecting aqueous phase. The time needed to achieve complete remediation for different initial contaminant concentrations in soil depends more on the NAPL droplet radius and the size of the stagnant boundary layer than on the initial contaminant mass itself. Location of wells and flux rates are of little significance over the time needed for completion as long as all the water that flows through the contaminated region is captured in the recovery well.
    Type of Medium: Electronic Resource
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  • 6
    ISSN: 1573-2959
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Model calculations are used to explore the effects of the kinetics of diffusion of dissolved organic compounds into and out of low-permeability porous materials and of the rate of solution of nonaqueous phase liquid (NAPL) droplets (into the aqueous phase) on the rate of cleanup of contaminated aquifers. Two models are presented: (1) the flushing of organic compounds initially distributed as NAPL droplets in a fracture in a porous rock aquifer, and (2) the removal of organic compounds initially present as NAPL in an aquifer containing low-permeability porous clay lenses. NAPL droplet size is found to be of much less importance than the spacing of the fractures in the porous rock in the first model or the thickness of the clay lenses in the second.
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  • 7
    Electronic Resource
    Electronic Resource
    Springer
    Annals of biomedical engineering 26 (1998), S. 883-891 
    ISSN: 1573-9686
    Keywords: Hearing testing ; Adaptive noise canceling ; Adaptive Wiener filtering ; Otoacoustic emissions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract An innovative acoustic noise canceling method using adaptive Wiener filtering (AWF) was developed for improved acquisition of distortion product otoacoustic emissions (DPOAEs). The system used one microphone placed in the test ear for the primary signal. Noise reference signals were obtained from three different sources: (a) pre-stimulus response from the test ear microphone, (b) post-stimulus response from a microphone placed near the head of the subject and (c) post-stimulus response obtained from a microphone placed in the subject’s nontest ear. In order to improve spectral estimation, block averaging of a different number of single sweep responses was used. DPOAE data were obtained from 11 ears of healthy newborns in a well-baby nursery of a hospital under typical noise conditions. Simultaneously obtained recordings from all three microphones were digitized, stored and processed off-line to evaluate the effects of AWF with respect to DPOAE detection and signal-to-noise ratio (SNR) improvement. Results show that compared to standard DPOAE processing, AWF improved signal detection and improved SNR. © 1998 Biomedical Engineering Society. PAC98: 4364Jb, 4360-c, 8790+y
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  • 8
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. We studied the precipitation of carbonates in 17 strains of moderately halophilic, Gram-positive cocci belonging to two species: Marinococcus halophilus and Marinococcus albus, isolated from the Salar de Atacama (Chile). They were cultivated in solid and liquid laboratory media for 42 days at salt concentrations (wt/vol) of 3%, 7.5%, 15%, and 20%. The bioliths precipitated were studied by X-ray diffraction and scanning electron microscopy. M. halophilus formed crystals at each of the salt concentrations, with a maximum number of strains capable of precipitating carbonates at 7.5% and 15% salt concentrations. M. albus did not precipitate at 20% and showed a maximum at 7.5%. This behavior is similar to that of other Gram-positive bacteria and differs from that found in Gram-negative bacteria. The bioliths precipitated were spherical, generally isolated, with a size of 10–100 μm, varying with salinity. They were of magnesium calcite (CO3 Ca1-x Mgx) with Mg content increasing with increasing salinity and Mg/Ca molar ratio of the culture medium. These results demonstrate the active role played by M. halophilus and M. albus in the precipitation of carbonates.
    Type of Medium: Electronic Resource
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  • 9
    ISSN: 1432-0991
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract Carbonate crystal formation by 48 strains of moderately halophilic microorganisms currently assigned to the genusFlavobacterium andAcinetobacter has been investigated. Strains were grown at different salt concentrations (2.5%, 7.5%, and 20%, wt/vol, total salts) and temperatures (22°C and 32°C). All the strains tested were capable of precipitating calcium carbonate as calcite, but onlyAcinetobacter strains formed aragonite. High temperature and low ionic strength of medium favored crystal formation. The influence of species specificity on the type of crystal precipitated by moderately halophilic microorganisms and their possible role in active precipitation in nature are discussed.
    Type of Medium: Electronic Resource
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  • 10
    Publication Date: 2013-10-29
    Print ISSN: 1550-7998
    Electronic ISSN: 1550-2368
    Topics: Physics
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