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  • 1
    Electronic Resource
    Electronic Resource
    Shape optimization of axisymmetric shells using a higher-order shear deformation theory (1995)
    Springer
    Structural and multidisciplinary optimization 9 (1995), S. 117-127 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper structural and sensitivity analysis for the optimization of laminated axisymmetric shells subjected to static constraints and arbitrary loading is presented. The shell thickness, radial coordinate of a nodal point, lamina thickness and the angle of orientation of the fibers are the design variables. The objective of the design optimization is the minimization of the volume of the shell or the strain energy. The model is based on a three-node axisymmetric finite element with 24 degrees of freedom. A higher-order theory is developed for the nonlinear distribution of the meridional displacement component through the thickness of the shell. The sensitivities of the discrete model developed are evaluated analytically using a symbolic manipulator. The efficiency and accuracy of the proposed model is discussed with reference to the applications.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01758828
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  • 2
    Electronic Resource
    Electronic Resource
    Sensitivity analysis and optimization of thin laminated structures with a nonsmooth eigenvalue based criterion (1997)
    Springer
    Structural and multidisciplinary optimization 14 (1997), S. 219-224 
    Details
    ISSN: 1615-1488
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract This paper presents a discrete model for the design sensitivity analysis of thin laminated angle-ply composite structures using a plate shell element based on a Kirchhoff discrete theory for the bending effects. To overcome the nondifferentiability of multiple eigenvalues, which may occur during a structural optimization involving free vibrations or buckling design situations, a nonsmooth eigenvalue based criterion is implemented. Angle-ply design variables and vectorial distances from the laminated midle surface to the upper surface of each layer are considered as design variables. The design sensitivities and the directional derivatives are evaluated analytically. The efficiency and accuracy of the model developed is discussed with two illustrative cases which show the need to compute sensitivities of multiple eigenvalues as directional derivatives for laminated composite structures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01197943
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  • 3
    Electronic Resource
    Electronic Resource
    Effect of cations, pH and sulfate content on the viscosity and emulsifying activity of the Halomonas eurihalina exopolysaccharide (1998)
    Springer
    Journal of industrial microbiology and biotechnology 20 (1998), S. 205-209 
    Details
    ISSN: 1476-5535
    Keywords: Keywords: exopolysaccharide; rheology; emulsifier
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: The effects of monovalent and divalent cations on the rheological behavior of Halomonas eurihalina exopolysaccharide (EPS) were studied. Sodium, potassium, magnesium and calcium were added and the relative abilities to increase viscosity were as follows: KCl 〉 NaCl 〉 MgCl2 〉 CaCl2. The highest viscosity value was measured in acidic 10−4 M KCl, in which a gel formed. A loss of sulfate content seemed to correlate with the increase of viscosity. H. eurihalina produced EPS in all growth media. Addition of hydrophobic substrates to culture media produced changes in chemical composition and emulsifying activity of the EPS. Xylene was the most effectively emulsified substance and the EPS produced on tetradecane and on corn oil the most active emulsifier.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1038/sj.jim.2900513
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  • 4
    Electronic Resource
    Electronic Resource
    Inactivation of the gene coding for the 30.4-kDa subunit of respiratory chain NADH dehydrogenase: is the enzyme essential for Neurospora? (1998)
    Springer
    Molecular genetics and genomics 257 (1998), S. 368-375 
    Details
    ISSN: 1617-4623
    Keywords: Key words Mitochondria ; Complex I ; Gene disruption ; Mutants ; Neurospora crassa
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We have isolated and characterised the nuclear gene that codes for the 30.4-kDa subunit of the peripheral arm of complex I from Neurospora crassa. The single-copy gene was localised on chromosome VI of the fungal genome by restriction fragment length polymorphism mapping. An extra copy of the gene was introduced into a strain of N. crassa by transformation. This strain was crossed with another strain in order to inactivate, by repeat-induced point mutations, both copies of the duplication carried by the parental transformant. Ascospore progeny from the cross were analysed and a mutant strain lacking the 30.4-kDa protein, nuo30.4, was isolated and further characterised. The mutant appears to assemble the membrane arm of complex I, while formation of the peripheral arm is prevented. Nevertheless, the mutant grows reasonably well – indicating that this well conserved protein is not essential for vegetative growth – and is able to mate with other strains both as male or female. Strains with multiple mutations are readily obtained from heterozygous crosses between different complex I mutants of N. crassa. On the other hand, homozygous crosses between several mutants, including nuo30.4, fail to produce ascospores. These results suggest that complex I plays an essential role during the sexual phase of the life cycle of the fungus.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004380050659
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  • 5
    Electronic Resource
    Electronic Resource
    Disruption of the nuclear gene encoding the 20.8-kDa subunit of NADH:ubiquinone reductase ofNeurospora mitochondria (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 177-183 
    Details
    ISSN: 1617-4623
    Keywords: Neurospora crassa ; Mitochondria ; Complex I ; Assembly ; Gene disruption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear gene coding for the 20.8-kDa subunit of the membrane arm of respiratory chain NADH:ubiquinone reductase (Complex I) fromNeurospora crassa, nuo-20.8, was localized on linkage group I of the fungal genome. A genomic DNA fragment containing this gene was cloned and a duplication was created in a strain ofN. crassa by transformation. To generate RIP (repeat-induced point) mutations in the duplicated sequence, the transformant was crossed with another strain carrying an auxotrophic marker on chromosome I. To increase the chance of finding an isolate with a non-functionalnuo-20.8 gene, random progeny from the cross were selected against this auxotrophy since RIP of the target gene will only occur in the nucleus carrying the duplication. Among these, we isolated and characterised a mutant strain that lacks the 20.8 kDa mitochondrial protein, indicating that this cysteine-rich polypeptide is not essential. Nevertheless, the absence of the 20.8-kDa subunit prevents the full assembly of complex I. It appears that the peripheral arm and two intermediates of the membrane arm of the enzyme are still formed in the mutant mitochondria. The NADH:ubiquinone reductase activity of sonicated mitochondria from the mutant is rotenone insensitive. Electron microscopy of mutant mitochondria does not reveal any alteration in the structure or numbers of the organelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02173218
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  • 6
    Electronic Resource
    Electronic Resource
    Disruption of the nuclear gene encoding the 20.8-kDa subunit of NADH:ubiquinone reductase of Neurospora mitochondria (1996)
    Springer
    Molecular genetics and genomics 252 (1996), S. 177-183 
    Details
    ISSN: 1617-4623
    Keywords: Key wordsNeurospora crassa ; Mitochondria ; Complex I ; Assembly ; Gene disruption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The nuclear gene coding for the 20.8k-kDa subunit of the membrane arm of respiratory chain NADH:ubiquinone reductase (Complex I) from Neurospora crassa, nuo-20.8 was localized on linkage group I of the fungal genome. A genomic DNA fragment containing this gene was cloned and a duplication was created in a strain of N. crassa by transformation. To generate RIP (repeat-induced point) mutations in the duplicated sequence, the transformant was crossed with another strain carrying an auxotrophic marker on chromosome I. To increase the chance of finding an isolate with a non-functional nuo-20.8 gene, random progeny from the cross were selected against this auxotrophy since RIP of the target gene will only occur in the nucleus carrying the duplication. Among these, we isolated and characterised a mutant strain that lacks the 20.8 kDa mitochondrial protein, indicating that this cysteine-rich polypeptide is not essential. Nevertheless, the absence of the 20.8-kDa subunit prevents the full assembly of complex I. It appears that the peripheral arm and two intermediates of the membrane arm of the enzyme are still formed in the mutant mitochondria. The NADH:ubiquinone reductase activity of sonicated mitochondria from the mutant is rotenone insensitive. Electron microscopy of mutant mitochondria does not reveal any alteration in the structure or numbers of the organelles.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004389670020
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  • 7
    Electronic Resource
    Electronic Resource
    Classification of Random Image Fields Using Synthetic Discriminant Functions: Spectral Statistical Approach and Its Computer-Optical Realization (1998)
    Springer
    Optical review 5 (1998), S. 219-225 
    Details
    ISSN: 1349-9432
    Keywords: image classification ; random image field ; power spectrum ; synthetic discriminant function ; statistical estimation ; Fourier-optical technique
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The problem of classification of images that have a perfectly random nature is considered. We propose a new approach to solve this problem that is based on the use of the synthetic discriminant functions being synthesized to separate linearly the power spectra of random image fields to be classified. In the stage of both discriminant function synthesis and classification, the statistical technique of power spectrum estimation is employed. The realization of the proposed approach by means of a hybrid computer-optical technique is discussed, and its efficiency is illustrated by two examples of real-world texture classification.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10043-998-0219-1
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  • 8
    Electronic Resource
    Electronic Resource
    Genetic diversity and relationships of cacao (Theobroma cacao L.) in southern Mexico (1998)
    Springer
    Theoretical and applied genetics 96 (1998), S. 621-627 
    Details
    ISSN: 1432-2242
    Keywords: Key words Cacao ; Theobroma cacao ; Genetic diversity ; Crop evolution ; RAPD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Neotropical tree crops are affected by a combination of biological and human factors that complicate the study of genetic diversity and crop evolution. Genetic diversity and relationships among southern Mexican populations and horticultural collections of Theobroma cacao (chocolate, cocoa, cacao) are examined in light of the agricultural practices of the Maya. Collections of cacao were obtained from the extremes of its geographic range including archeological sites in southern Mexico where cacao was first domesticated. Genetic diversity was assayed by 57 informative random amplified polymorphic DNA (RAPD) marker loci. A unique sample of the total diversity found in this study exists in the southern Mexican populations. These populations are significantly different from all other cacao with regards to their profile of RAPD bands, including the ‘criollo’ variety, their morphological and geographical group. A population of cacao found in a sinkhole (cenote) in northern Yucatan with genetic affinities to populations in Chiapas suggests the Maya maintained plants far away from their native habitat. This finding concurs with known agroforestry practices of the Maya. Modern efforts to increase germplasm of tropical tree crops such as cacao should carefully examine archeological sites where genetic diversity, either deliberately or by chance, was collected and maintained by ancient cultures.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s001220050780
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  • 9
    Electronic Resource
    Electronic Resource
    Effect of cellulase adsorption on the surface and interfacial properties of cellulose (1999)
    Springer
    Cellulose 6 (1999), S. 265-282 
    Details
    ISSN: 1572-882X
    Keywords: cellulase ; cellulose ; drainability ; protein adsorption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract The surface properties of several purified cellulose (Sigmacell 101, Sigmacell 20, Avicel pH 101, and Whatman CF 11) were characterised, before and after cellulase adsorption. The following techniques were used: thin-layer wicking (except for the cellulose Whatman), thermogravimetry, and differential scanning calorimetry (for all of the above celluloses). The results obtained from the calorimetric assays were consistent with those obtained from thin-layer wicking – Sigmacell 101, a more amorphous cellulose, was the least hydrophobic of the analysed celluloses, and had the highest specific heat of dehydration. The other celluloses showed less affinity for water molecules, as assessed by the two independent techniques. The adsorption of protein did not affect the amount of water adsorbed by Sigmacell 101. However, this water was more strongly adsorbed, since it had a higher specific heat of dehydration. The more crystalline celluloses adsorbed a greater amount of water, which was also more strongly bound after the treatment with cellulases. This effect was more significant for Whatman CF-11. Also, the more crystalline celluloses became slightly hydrophilic, following protein adsorption, as assessed by thin-layer wicking. However, this technique is not reliable when used with cellulase treated celluloses.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009251722598
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  • 10
    Electronic Resource
    Electronic Resource
    Strong Vortex Pinning in the Low–Temperature Superconducting Phase of (U1−xThx)Be13 (1999)
    Springer
    Journal of low temperature physics 117 (1999), S. 1477-1481 
    Details
    ISSN: 1573-7357
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We have found a sharp transition at T c2 = 350 mK in the vortex creep rate of a single crystal of (U 1−x Th x )Be 13 with T c = 523 mK (x = 0.0275). For T ≪ T c2 , no creep of vortices is observed in a time scale of 105 s, while for T c2 〈 T 〈 T c , vortices creep at very high rates (30% of decay from a metastable configuration in the first 105 s at T = 400 mK). The sharp transition occurs at the same temperature at which the second jump in the specific heat appears in these samples. Similar low levels of creep rates have been reported by us in the low–T superconducting phase of UPt 3.1
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022566322062
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