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  • 1
    Electronic Resource
    Electronic Resource
    Fingering phenomena for driven coating films (2000)
    [S.l.] : American Institute of Physics (AIP)
    Physics of Fluids 12 (2000), S. 1278-1295 
    Details
    ISSN: 1089-7666
    Source: AIP Digital Archive
    Topics: Physics
    Notes: A theoretical and numerical model is formulated to describe the instability and the long-time evolution of both gravity-driven and surface-shear-stress-driven thin coating films. A single evolution equation, of higher-order diffusive type, models the flow for either problem. It is derived using the lubrication approximation. For partially wetting systems, the effect of finite contact angle is incorporated in the equation using a particular disjoining pressure model. The base state, in each case, is a two-dimensional steadily propagating capillary front. Slight perturbations of the base state, applied along the front, initiate the fingering instability. Early-time results accurately reproduce the wavelengths of fastest growth and the corresponding eigenmodes as reported in published linear stability analyses. As time proceeds, depending on parameter values, various fingering patterns arise. For conditions of perfect wetting with the substrate downstream of the moving front covered with a thin precursor layer, predicted nonlinear finger evolution agrees well with published experiments. The ultimate pattern, in this case, is a steadily translating pattern of wedge-shaped fingers. Alternatively, for partially wetting systems that exhibit sufficiently large static contact angles, long straight-sided fingers or rivulets are formed. Finally, for larger contact angles, or at relatively low speeds, we predict that the flowing rivulets will become unstable and break up into strings of isolated droplets. © 2000 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.870382
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  • 2
    Electronic Resource
    Electronic Resource
    Reduction in denitrification activity in field soils exposed to long term contamination by 2,4,6-trinitrotoluene (TNT) (2000)
    Oxford, UK : Blackwell Publishing Ltd
    FEMS microbiology ecology 32 (2000), S. 0 
    Details
    ISSN: 1574-6941
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Biology
    Notes: Terrestrial sites contaminated with 2,4,6-trinitrotoluene (TNT) are a widespread and persistent problem and often contain non-vegetated areas with TNT concentrations well in excess of 1000 mg kg−1. In this study, we examined the effect of TNT on denitrification activity in field soils, and compared the sensitivity of denitrifying enzymes to TNT. DNA probes assessed the prevalence of nirS, nirK and nosZ (encoding cd1 or copper nitrite reductase and nitrous oxide reductase, respectively), denitrifying genotypes in the culturable and total microbial community. The nitrate (NaR), nitrite (NiR) and nitrous oxide (N2OR) reductase activities in field soil and in isolates were assessed by gas chromatography. The relative occurrence of the nirK, nirS or nosZ genotypes increased in the cultured community and in total uncultured community DNA as nitroaromatic concentrations increased. However, denitrifying activity decreased in response to increasing TNT concentrations, with an IC50 for NaR+NiR+nitric oxide reductase (NOR) of 400 mg TNT kg−1 soil and for N2OR of 26 mg TNT kg−1 soil. The denitrifying activity of four soil isolates also decreased in response to TNT, with N2OR activity being three times more sensitive to TNT than NaR+NiR+NOR activity. Interestingly, there were 118 times more nirK isolates than nirS isolates in uncontaminated soil but only 1.5 times more in soil containing 17 400 mg kg−1 TNT. The results from this study indicated that TNT reduced denitrification activity in field soils, and N2OR was much more sensitive to TNT than NaR+NiR+NOR.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1574-6941.2000.tb00699.x
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  • 3
    Electronic Resource
    Electronic Resource
    Mechanochemical Synthesis of Complex Zirconium Phosphates (2000)
    Springer
    Journal of materials synthesis and processing 8 (2000), S. 279-286 
    Details
    ISSN: 1573-4870
    Keywords: Framework complex zirconium phosphates ; mechanochemical activation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Cation- and anion-substituted zirconium phosphates of X kZr m (PO4) n−y Y composition, where X = Na+, La3+, NH4 +, Y = F−, WO4 2−, 1/3 〈 k 〈 2, 2 〈 m 〈 4, 3 〈 n 〈 6 were synthesized by the procedure, including mechanical activation of the starting salts mixture followed by annealing at 300–900°C. The interaction between components was studied by XRD, EXAFS, FT–IR, [31P-MAS] NMR. The possibility of synthesizing nonstoichiometric compounds is demonstrated and prospects for application of the mechanochemical method for synthesis of complex zirconium phosphates are outlined.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011334125802
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  • 4
    Electronic Resource
    Electronic Resource
    The microstructure and properties of framework zirconium phosphates based nanocomposites – catalysts of alkane isomerization (2000)
    Springer
    Materials research innovations 3 (2000), S. 276-285 
    Details
    ISSN: 1433-075X
    Keywords: Key words Nanocomposites ; Framework zirconium phosphates ; Supported nanoparticles of WO3 ; MoO3 and Pt ; Catalysis of pentane and hexane isomerization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Nanocomposites based upon framework zirconium phosphates with supported WO3, MoO3 and Pt nanoparticles were synthesized via the incipient wetness impregnation of high-surface-area mesoporous phosphate samples with water solutions of corresponding salts followed by drying and calcination. The structure and surface properties of nanocomposites were studied by using combination of structural and spectral methods. Due to a strong interaction between supports and supported species, the structure of the latter differs considerably from that of the bulk phases. Surface acid centers typical for zirconium phosphates disappear suggesting their participation in bonding nanoparticles of promoters. Instead, new types of strong acid sites associated with tungsten oxide clusters emerge. The effect of these promoters on performance of zirconium phosphates in the reaction of pentane and hexane isomerization is considered.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100190000051
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  • 5
    Electronic Resource
    Electronic Resource
    The perovskite structure – a review of its role in ceramic science and technology (2000)
    Springer
    Materials research innovations 4 (2000), S. 3-26 
    Details
    ISSN: 1433-075X
    Keywords: Keywords Perovskite ; Crystal-chemistry ; Tolerance factor ; Ferroics ; Electro-ceramics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract  Starting with the history of the fundamental science of the relation of structure to composition delineated completely by Goldschmidt, we use the perovskite structure to illustrate the enormous power of crystal chemistry-based intelligent synthesis in creating new materials. The perovskite structure is shown to be the single most versatile ceramic host. By appropriate changes in composition one can modify the most significant electroceramic dielectric (BaTiO3 and its relatives) phase in industry, into metallic conductors, superconductors or the highest pressure phases in the earth. After an historical introduction of the science, detailed treatment of the applications is confined to the most recent research on novel uses in piezoelectric, ferroelectric and related applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100190000062
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  • 6
    Electronic Resource
    Electronic Resource
    The how of doing materials research: interdisciplinarity essential, but still elusive in universities (2000)
    Springer
    Materials research innovations 3 (2000), S. 183-184 
    Details
    ISSN: 1433-075X
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s100190050001
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  • 7
    Electronic Resource
    Electronic Resource
    Arthropod–Frog Connection: Decahydroquinoline and Pyrrolizidine Alkaloids Common to Microsympatric Myrmicine Ants and Dendrobatid Frogs (2000)
    Springer
    Journal of chemical ecology 26 (2000), S. 73-85 
    Details
    ISSN: 1573-1561
    Keywords: Alkaloids ; coccinellines ; decahydroquinolines ; indolizidines ; pyrrolidines ; pyrrolizidines ; dendrobatid frogs ; myrmicine ants ; coccinellid beetles ; millipedes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Neotropical poison frogs (Dendrobatidae) contain a wide variety of lipophilic alkaloids, apparently accumulated unchanged into skin glands from dietary sources. Panamanian poison frogs (Dendrobates auratus) raised in a large, screened, outdoor cage and provided for six months with leaf-litter from the frog's natural habitat, accumulated a variety of alkaloids into the skin. These included two isomers of the ant pyrrolizidine 251K; two isomers of the 3,5-disubstituted indolizidine 195B; an alkaloid known to occur in myrmicine ants; another such indolizidine, 211E; two pyrrolidines, 197B and 223N, the former known to occur in myrmicine ants; two tricyclics, 193C and 219I, the former known to occur as precoccinelline in coccinellid beetles; and three spiropyrrolizidines, 222, 236, and 252A, representatives of an alkaloid class known to occur in millipedes. The alkaloids 211E, 197B, and 223N appear likely to derive in part from ants that entered the screened cage. In addition, the frog skin extracts contained trace amounts of four alkaloids, 205D, 207H, 219H, and 231H, of unknown structures and source. Wild-caught frogs from the leaf-litter site contained nearly 40 alkaloids, including most of the above alkaloids. Pumiliotoxins and histrionicotoxins were major alkaloids in wild-caught frogs, but were absent in captive-raised frogs. Ants microsympatric with the poison frog at the leaf-litter site and at an island site nearby in the Bay of Panamá were examined for alkaloids. The decahydroquinoline (−)-cis-195A and two isomers of the pyrrolizidine 251K were found to be shared by microsympatric myrmicine ants and poison frogs. The proportions of the two isomers of 251K were the same in ant and frog.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1005437427326
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