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  • 11
    Electronic Resource
    Electronic Resource
    Adsorption and reaction of 2-propen-1-ol in H-ZSM-5 (1990)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 94 (1990), S. 2063-2067 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100368a062
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  • 12
    Electronic Resource
    Electronic Resource
    Variance component estimations and allocation of resources for breeding sweetpotato under East African conditions (2004)
    Oxford, UK : Blackwell Publishing Ltd
    Plant breeding 123 (2004), S. 0 
    Details
    ISSN: 1439-0523
    Source: Blackwell Publishing Journal Backfiles 1879-2005
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: In Africa, average sweetpotato storage root yields are low and breeding is considered to be an important factor in increasing production. The objectives of this study were to obtain variance component estimations for sweetpotato in this region of the world and then use these to determine the efficiency of variety trials and breeding systems. From an incomplete series of variety trials in Kenya and Uganda (comprising 15 genotypes, three locations, two crop durations and three seasons) variance components were estimated - using the REML method - for the following traits: storage root yield, biomass production, harvest index, storage root dry matter and the Elston index which was used to aggregate all four traits. The storage root yield of clones across all 12 environments ranged from 15.2 to 33.0 t/ha. The variance components were significant for all traits, except the genotype by season interactions for storage root dry matter. The efficiency of selection systems was determined for total test capacities of 450 and 900 plots and using not more than five locations. Two-stage selection was 17-81% more efficient than one-stage selection after two seasons of testing. Two-stage selection was optimized under the restriction of using at least two locations at step 1. Trials with two locations and one replication at step 1 and five locations and two replications at step 2 were appropriate both for selecting for storage root yield and for simultaneously selecting for storage root yield, biomass production, harvest index and storage root dry matter content by using the Elston index. There are indications that such an allocation of resources for breeding sweetpotato is also appropriate for other regions in Sub-Saharan Africa.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1111/j.1439-0523.2004.01000.x
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  • 13
    Electronic Resource
    Electronic Resource
    X-ray characteristics of a niobium superconducting tunnel junction with a highly transmissive tunnel barrier (1993)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 73 (1993), S. 5098-5104 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The results of an investigation into the x-ray properties of a superconducting tunnel junction (STJ) are presented. The photoabsorption of an x-ray photon by one of the thin superconducting films of the junction results in the production of quasiparticles, which may subsequently tunnel through the thin oxide barrier into the second superconducting film. The transfer of charge across the barrier is detected, and gives a measure of both the x-ray photon energy and the effective energy gap ε of the superconducting film in which the photoabsorption occurred. A charge output of 55% of the theoretical maximum has been obtained for a niobium-based STJ. Such a charge output indicates a mean energy ε of (approximately-equal-to)4.7 meV is required to create a single charge carrier in the junction such that ε/Δ(approximately-equal-to)3, where 2Δ is the junction energy gap. This is the lowest value of ε/Δ obtained to date for x-ray photoabsorption in STJs. The energy resolution of the device is, however, still poor, with a full width half maximum of (approximately-equal-to)200 eV for 6 keV x rays, compared with the theoretical Fano limited resolution of (approximately-equal-to)4 eV. The principle mechanisms which are believed to degrade the resolution are discussed. These are principally quasiparticle recombination, phonon leakage out of the junction, quasiparticle diffusion into and out of the tunneling region, in addition to possible local variations in the energy gap. A Monte Carlo simulation of the nonequilibrium system has been performed. The results assist in the identification of the major charge loss mechanisms, and indicate various means by which Fano limited resolution may be obtained.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.353782
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  • 14
    Electronic Resource
    Electronic Resource
    Chemistry of colloidal manganese dioxide. 2. Reaction with superoxide anion (O2-) and hydrogen peroxide (pulse radiolysis and stop flow studies) (1985)
    s.l. : American Chemical Society
    The @journal of physical chemistry 〈Washington, DC〉 89 (1985), S. 5779-5783 
    Details
    Source: ACS Legacy Archives
    Topics: Chemistry and Pharmacology , Physics
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1021/j100272a041
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  • 15
    Electronic Resource
    Electronic Resource
    A zoo without bars - by T.A.M. Nash Wayte Binding, Kent, UK, 1984, £9.95
    Amsterdam : Elsevier
    Land Use Policy 3 (1986), S. 366 
    Details
    ISSN: 0264-8377
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0264-8377(86)90042-6
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  • 16
    Electronic Resource
    Electronic Resource
    The properties of niobium superconducting tunneling junctions as X-ray detectors
    Amsterdam : Elsevier
    Nuclear Instruments and Methods in Physics Research Section A: 313 (1992), S. 173-195 
    Details
    ISSN: 0168-9002
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Physics
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0168-9002(92)90095-L
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  • 17
    Electronic Resource
    Electronic Resource
    Application of ion chromatography to the determination of inorganic anions in foodstuffs
    Amsterdam : Elsevier
    Journal of Chromatography A 624 (1992), S. 451-470 
    Details
    ISSN: 0021-9673
    Source: Elsevier Journal Backfiles on ScienceDirect 1907 - 2002
    Topics: Chemistry and Pharmacology
    Type of Medium: Electronic Resource
    URL: http://linkinghub.elsevier.com/retrieve/pii/0021-9673(92)85695-P
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  • 18
    Electronic Resource
    Electronic Resource
    HMDC crosslinking of bovine pericardial tissue: a potential role of the solvent environment in the design of bioprosthetic materials (1995)
    Springer
    Journal of materials science 6 (1995), S. 235-241 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The need for alternative crosslinking techniques in the processing of bioprosthetic materials is widely recognized. While glutaraldehyde remains the most commonly used crosslinking agent in biomaterial applications there is increasing concern as to its biocompatibility-principally due to its association with enhanced calcification, cytotoxicity, and undesirable changes in the mechanical properties of bioprosthetic materials. Hexamethylene diisocyanate (HMDC), like glutaraldehyde, is a bifunctional molecule which covalently bonds with amino groups of lysine residues to form covalent crosslinks. Evidence within the literature indicates HMDC-treated materials are less cytotoxic than glutaraldehyde-treated materials; however, there is limited characterization of the material properties of HMDC-treated tissue. This study uses a multi-disciplined approach to characterize the mechanical, thermal, and biochemical properties of HMDC-treated bovine pericardial tissue. Further, to facilitate stabilization of the HMDC reagent, non-aqueous solvent environments were investigated. HMDC treatment produced changes in mechanical properties, denaturation temperature, and enzymatic resistance consistent with crosslinking similar to that seen in glutaraldehyde treated tissue. The significantly lower extensibility and stiffness observed under low stresses may be attributed to the effect of the 2-propanol solvent environment during crosslinking. While the overall acceptability of HMDC as a crosslinking agent for biomaterial applications remains unclear, it appears to be an interesting alternative to glutaraldehyde with many similar features.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00146862
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  • 19
    Electronic Resource
    Electronic Resource
    Crosslinking of tissue-derived biomaterials in 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) (1996)
    Springer
    Journal of materials science 7 (1996), S. 531-541 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: In contrast to bifunctional reagents such as glutaraldehyde or polyfunctional reagents such as polyepoxides, carbodiimides belong to the class of zero-length crosslinkers which modify amino acid side-groups to permit crosslink formation, but do not remain as part of that linkage. The authors have compared the effects of 1-ethyl-3-(3-dimethylaminopropyl)-carbodiimide (EDC) and glutaraldehyde (the de facto industrial standard crosslinker) on the hydrothermal, biochemical, and uniaxial mechanical properties of bovine pericardium. EDC crosslinking was optimized for maximum increase in collagen denaturation temperature using variables of pH, concentration, and ratio of EDC to N-hydroxysuccinimide (NHS): a reagent for formation of activated esters. EDC and glutaraldehyde crosslinked materials were subjected to hydrothermal denaturation tests, biochemical degradation by enzymes (collagenase, trypsin) and CNBr, amino acid analysis for unreacted lysine, and to high strain rate mechanical tests including: large deformation stress-strain studies (0.1 to 10 Hz), stress relaxation experiments (loading time 0.1 s) and small deformation forced vibration (1 and 10 Hz). A protocol for EDC crosslinking was developed which used 1.15% EDC (2:1 EDC:NHS) at pH 5.5 for 24 h. The increase in denaturation temperature for EDC (from 69.7±1.2°C to 86.0±0.3°C) was equivalent to that produced by glutaraldehyde (85.3±0.4°C). Both treatments equivalently increased resistance to collagenase and CNBr degradation; however, after denaturation, the EDC-treated tissue was slightly more resistant to collagenase, and markedly more resistant to trypsin. EDC-treated materials were more extensible and more elastic than glutaraldehyde-treated materials. Despite the differences in crosslinking mechanism, EDC and glutaraldehyde-treated materials are very similar. Subtle but intriguing differences in biochemical structure remain to be investigated.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00122176
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  • 20
    Electronic Resource
    Electronic Resource
    New starch-based thermoplastic hydrogels for use as bone cements or drug-delivery carriers (1998)
    Springer
    Journal of materials science 9 (1998), S. 825-833 
    Details
    ISSN: 1573-4838
    Source: Springer Online Journal Archives 1860-2000
    Topics: Medicine , Technology
    Notes: Abstract The development of new biodegradable hydrogels, based on corn starch/cellulose acetate blends, produced by free-radical polymerization with methyl methacrylate monomer (MMA) and/or an acrylic acid monomer (AA), is reported. The polymerization was initiated by a redox system consisting of a benzoyl peroxide and 4-dimethlyaminobenzyl alcohol at low temperature. These hydrogels may constitute an alternative to the materials currently used as bone cements or drug-delivery carriers. Swelling studies were carried out, as a function of pH and temperature, in buffered solutions. The xerogels were further characterized by Fourier transform–infrared spectroscopy. Tensile and compression tests, and dynamic mechanical thermal analysis were used to assess the mechanical performance of the developed materials. The fracture surfaces were observed by scanning electron microscopy. The developed materials are sensitive to the pH, showing a clear reversible transition in a relatively narrow interval of pH, which is just in the range of physiological conditions. These properties make the materials developed in this study very promising for biomedical applications. Fickian-type diffusion is the mechanism predominant in these systems, except for the composition with a higher concentration of AA, that corresponds to the most desirable kinetical behavior for controlled release (case II-transport mechanism). Furthermore, the results obtained in the mechanical tests are in the range of those reported for typical PMMA bone cements, showing that it is possible to develop partially degradable cements with an adequate mechanical behavior. © 1998 Kluwer Academic Publishers
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008944127971
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