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  • Biochemistry and Biotechnology  (2)
  • pH  (2)
  • sintering  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Drying and Sintering of Bulk Silica Gels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 397-402 
    Details
    ISSN: 1573-4846
    Keywords: silica glass ; monolith ; sub-critical drying ; chlorination ; sintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Over the last few years, the feasibility of fabricating near net shape silica glass components, using a sub-critical drying process for pure alkoxide gels, has been demonstrated in our laboratories. Cracking during drying, due to capillary forces generated in the gel body, was overcome through two particular innovations. The first was the development and optimization of a dual-catalyzed high strength gel. The second was a controlled atmosphere drying process that allowed the gel to dry utilizing a newly observed phenomenology, postulated to be due to cavitation of the pore fluid. Contrary to conventional wisdom, in this drying approach the smallest pore size gels are the easiest to dry. Details of the types of gels and the drying process are reported. Gels of small size were sintered into crack-free glasses, utilizing conventional sintering approaches. However, large size gels always developed visible surface cracks that formed above 800°C. To successfully dry and sinter large monolithic gels then required re-optimization of the entire process. A great number of micron-range defects were initially detected in these sintered bodies. After analyzing the defects, further steps were taken to improve glass quality to the level of optical glass produced by vapor deposition processes. This included mixing and filtering of sols in a clean room, varying the pore size distribution, and optimizing the pre-sintering and sintering processes. Data of relevant glass quality parameters attained so far in the laboratory are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1026436429406
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  • 2
    Electronic Resource
    Electronic Resource
    Drying and sintering of bulk silica gels (1997)
    Springer
    Journal of sol gel science and technology 8 (1997), S. 397-402 
    Details
    ISSN: 1573-4846
    Keywords: silica glass ; monolith ; sub-critical drying ; chlorination ; sintering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Over the last few years, the feasibility of fabricating near net shape silica glass components, using a sub-critical drying process for pure alkoxide gels, has been demonstrated in our laboratories. Cracking during drying, due to capillary forces generated in the gel body, was overcome through two particular innovations. The first was the development and optimization of a dual-catalyzed high strength gel. The second was a controlled atmosphere drying process that allowed the gel to dry utilizing a newly observed phenomenology, postulated to be due to cavitation of the pore fluid. Contrary to conventional wisdom, in this drying approach the smallest pore size gels are the easiest to dry. Details of the types of gels and the drying process are reported. Gels of small size were sintered into crack-free glasses, utilizing conventional sintering approaches. However, large size gels always developed visible surface cracks that formed above 800°C. To successfully dry and sinter large monolithic gels then required re-optimization of the entire process. A great number of micron-range defects were initially detected in these sintered bodies. After analyzing the defects, further steps were taken to improve glass quality to the level of optical glass produced by vapor deposition processes. This included mixing and filtering of sols in a clean room, varying the pore size distribution, and optimizing the pre-sintering and sintering processes. Data of relevant glass quality parameters attained so far in the laboratory are reported.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02436872
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  • 3
    Electronic Resource
    Electronic Resource
    Influence of rhizosphere on the nutrient status of dwarf French beans (1982)
    Springer
    Plant and soil 64 (1982), S. 369-380 
    Details
    ISSN: 1573-5036
    Keywords: French beans ; Nutrient uptake ; pH ; Rhizosphere
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract French bean seedlings grown on choline, ammoniacal and nitrate forms of nitrogen together with equivalent basal application of P as KH2PO4 were tested for nutrient uptake from the rhizosphere. Statistical tests on soil (rhizosphere and non-rhizosphere) and plant (root and shoot) revealed that with the exception of P, levels of all other estimated macro-(Na+, K+, Ca2+, Mg2+) and micro-nutrients (Fe2+, Mn2+, Zn2+) were significantly changed after 42 days growth as compared to 21 days growth period. The higher uptake into shoots of Na+, K+, Fe2+, Mn2+, Zn2+ and H2PO4 − and higher biomass accumulation in the rhizosphere were associated with lower rhizosphere pH. The uptake of Ca2+ and Mg2+ increased with higher rhizosphere pH. While ammoniacal and choline forms decreased rhizosphere pH and increased the P uptake, nitrate form reversed the trend showing significant inverse relationship between shoot phosphate and rhizosphere pH. Calcium and iron were associated with an inhibition of the translocation of P from root to shoot. However, no causal relationships could be established. Both shoot weight and shoot P content were closely associated with a number of rhizosphere soil parameters.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02372520
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  • 4
    Electronic Resource
    Electronic Resource
    A study on short-time sampling of individual rain events at New Delhi during monsoon, 1994 (1995)
    Springer
    Water, air & soil pollution 85 (1995), S. 2143-2148 
    Details
    ISSN: 1573-2932
    Keywords: rain event ; pH ; intensity ; crustal ; antecedent periods
    Source: Springer Online Journal Archives 1860-2000
    Topics: Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Rain water samples of equal volume (50 mL) were collected from two couvective showers at New Delhi on 28 July and 23 August during the monsoon, 1994. The variation of constituents of both the showers showed different trends which might have been due to different antecedent periods. The first shower occurred after an antecedent period of 2–3 hours while the second shower occurred after a 14 day interval. The first shower had acidic pH (〈5.6) and relatively higher concentration of NH4, SO4, NO3, Cl, F and K indicating insignificant below cloud scavenging. The second shower had alkaline pH (〉5.6) and relatively higher concentrations of Ca and Mg. The higher concentration of Ca and Mg in the second shower were due to the loading with particulate matter during the preceding 14 days which made below cloud scavenging significant.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01186151
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  • 5
    Electronic Resource
    Electronic Resource
    Transport of bacteria in porous media: I. An experimental investigation (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 489-497 
    Details
    ISSN: 0006-3592
    Keywords: Bacillus licheniformis ; bacterial transport ; porous media ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The convective transport of concentrated suspension of bacteria in porous media is of interest for several processes such as microbial enhanced oil recovery and in situ bioremediation. The parameters which affect the transport of the bacterium Bacillus licheniformis JF-2, a candidate microorganism for microbial enhanced oil recovery, were investigated experimentally in sandpacks. Bacteria retention and permeability reduction occurred primarily in the first few centimeters upon entering the porous medium. In downstream sections of the sandpack, the permeability reduction was low, even in cases in which high cell concentrations (108 cfu/mL) were detected in the effluent. The effect of (i) addition of a dispersant, (ii) linear velocity of injection, (iii) cell concentration, (iv) salinity (v) temperature, and (vi) the presence of a residual oleic phase were determined experimentally. A lower reduction in permeability and a higher effluent bacterial concentration were obtained in the presence of dispersant, high injection velocities, low salinities, and at a higher temperature. Macroscopic measurements at different linear velocities and in the presence or absence of dispersants suggest that the formation of reversible microaggregates and multiparticle hydrodynamic exclusion may be the primary mechanisms for bacterial retention and permeability reduction. © 1994 John Wiley & Sons, Inc.
    Additional Material: 8 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440412
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  • 6
    Electronic Resource
    Electronic Resource
    Transport of bacteria in porous media: II. A model for convective Transport and growth (1994)
    New York, NY [u.a.] : Wiley-Blackwell
    Biotechnology and Bioengineering 44 (1994), S. 499-508 
    Details
    ISSN: 0006-3592
    Keywords: bacterial transport ; porous media ; Chemistry ; Biochemistry and Biotechnology
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: A model is presented for the coupled processes of bacterial growth and convective transport of bacteria has been modeled using a fractional flow approach. The various mechanisms of bacteria retention can be incorporated into the model through selection of an appropriate shape of the fractional flow curve. Permeability reduction due to pore plugging by bacteria was simulated using the effective medium theory. In porous media, the rates of transport and growth of bacteria, the generation of metabolic products, and the consumption of nutrients are strongly coupled processes. Consequently, the set of governing conservation equations form a set of coupled, nonlinear partial differential equations that were solved numerically. Reasonably good agreement between the model and experimental data has been obtained indicating that the physical processes incorporated in the model are adequate. The model has been used to predict the in situ transport and growth of bacteria, nutrient consumption, and metabolite production. It can be particularly useful in simulating laboratory experiments and in scaling microbial-enhanced oil recovery or bioremediation processes to the field. © 1994 John Wiley & Sons, Inc.
    Additional Material: 7 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/bit.260440413
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