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  • 1
    Electronic Resource
    Electronic Resource
    Genetic Evidence for Gonochoristic Reproduction in Gynogenetic Silver Crucian Carp (Carassius auratus gibelio Bloch) as Revealed by RAPD Assays (2000)
    Springer
    Journal of molecular evolution 51 (2000), S. 498-506 
    Details
    ISSN: 1432-1432
    Keywords: Key words: Silver crucian carp — Gynogenesis — Gonochoristic reproduction — Sex evolution — Genetic recombination — RAPD markers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract. Sex evolution has been a debating focus in evolutionary genetics. In lower vertebrates of reptiles, amphibians, and fish, a species or a bioform reproduces either sexually or asexually but never both. A few species were found to consist of all females in fish. These all-female species can propagate by asexual reproduction modes, such as gynogenesis and hybridogenesis. However, the coexistence of sexuality and asexuality in a single species was recently noted only in a cyprinid fish silver crucian carp, Carassius auratus gibelio. This fish had been demonstrated to be capable of gynogenesis stimulated by sperm from other related species. Surprisingly, natural populations of this fish consist of a minor but significant portion (approx. 20%) of males. As different clones with specific phenotypic and genetic characteristics have been found, and RAPD markers specific to each clone have recently been identified, this fish offers many advantages for analyzing whether or not genetic recombination occurs between different clones. In this study, artificial propagation was performed in clone F and clone D. Ovulated eggs from clone F were divided into two parts and respectively inseminated with sperm from a clone D male and from a red common carp (Cyprinus carpio) male. The control clone D individuals were selected from gynogenetic offspring of clone D activated by sperm of red common carp. The phenotype and sex ratio in the experimental groups were also observed. Using RAPD molecular markers, which allow for reliable discrimination and genetic analysis of different clones, we have revealed direct molecular evidence for gonochoristic reproduction in the gynogenetic silver crucian carp and confirmed a previous hypothesis that the silver crucian carp might reproduce both gynogenetically and gonochoristically. Therefore, we conclude that the silver crucian carp possesses two reproductive modes, i.e., gynogenetic and gonochoristic reproduction. The response mechanism of two reproductive development modes may be the first discovery in vertebrates. Additionally, we discuss the evolutionary implication between gynogenetic and gonochoristic reproduction modes and the contribution of the minor proportion of males to genetic flexibility in the gynogenetic silver crucian carp.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s002390010113
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  • 2
    Electronic Resource
    Electronic Resource
    The criterion of critical void growth ratio and its applications (1988)
    Springer
    Acta mechanica solida Sinica 1 (1988), S. 149-158 
    Details
    ISSN: 0894-9166
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract In the present paper, the new material parameter of ductile fracturev gc with an obvious microscopic physical meaning is emphasized, which can be determined by macroscopic method. The theoretical and experimental background for the criterion of critical void growth ratio is expounded from both macroscopic and microscopic points of view. The relationship between the macroform parameterv gc and microform oneR c /R go of critical void growth ratio is investigated. The engineering experimental procedure for determining the value ofv gc of materials has been recommended. The values ofv gc for some materials with different heat treatments have been estimated. It is found that the parameterv gc can be effectively used for selecting materials and their heat treatments. A modified ASPEF criterion accounting for stress states has been proposed. Related expression of modified ASPEF andv gc has been derived.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02208138
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  • 3
    Electronic Resource
    Electronic Resource
    On the single fibre pullout and pushout problem: Effect of fibre anisotropy (1993)
    Springer
    Zeitschrift für angewandte Mathematik und Physik 44 (1993), S. 769-775 
    Details
    ISSN: 1420-9039
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract Based on our recent theoretical model of the interfacial debonding and fibre pullout/pushout stresses, an improved analysis including the effect of fibre anisotropy has been performed for single fibre pullout and pushout. During fibre-matrix debonding the debonded region is considered as an interfacial crack and its extension is dependent on a fracture energy criterion being satisfied. The elastic properties of the fibre are taken to be transversely isotropic about the fibre axis and the matrix is assumed to be isotropic. The results show that the maximum debond stress for fibre pullout and the initial frictional pullout stress increase as the ratio of the Young's moduli of the fibre between the axial and radial directionsE f /E f r increases, and this is particularly so at large embedded fibre lengths. However, in the case of fibre pushout these debond and pushout stresses decrease asE f /E f r increases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00948488
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  • 4
    Electronic Resource
    Electronic Resource
    A new algorithm for the quasi-assignment problem (1990)
    Springer
    Annals of operations research 24 (1990), S. 205-223 
    Details
    ISSN: 1572-9338
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The quasi-assignment problem can be used to solve the bus scheduling problem, the tourist guide problem, and the minimum number of chains in a partially ordered set. A successive shortest path algorithm for the assignment problem is extended to the quasiassignment problem. The algorithm is a variation of the primal-dual algorithm, and its computational complexity isO(n 3).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02216824
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  • 5
    Electronic Resource
    Electronic Resource
    Interfacial debonding and fibre pull-out stresses (1994)
    Springer
    Journal of materials science 29 (1994), S. 5541-5550 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Based on a theoretical model developed previously by the authors in Part II of this series for a single fibre pull-out test, a methodology for the evaluation of interfacial properties of fibre-matrix composites is presented to determine the interfacial fracture toughness G c, the friction coefficient μ, the radial residual clamping stress q o and the critical bonded fibre length z max. An important parameter, the stress drop Δσ, which is defined as the difference between the maximum debond stress σ d * and the initial frictional pull-out stress σfr, is introduced to characterize the interfacial debonding and fibre pull-out behaviour. The maximum logarithmic stress drop, In(Δσ), is obtained when the embedded fibre length L is equal to the critical bonded fibre length z max. The slope of the In(Δσ)-L curve for L bigger than z max is found to be a constant that is related to the interfacial friction coefficient μ. The effect of fibre anisotropy on fibre debonding and fibre pull-out is also included in this analysis. Published experimental data for several fibre-matrix composites are chosen to evaluate their interfacial properties by using the present methodology.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00349945
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  • 6
    Electronic Resource
    Electronic Resource
    Interfacial debonding and fibre pull-out stresses (1993)
    Springer
    Journal of materials science 28 (1993), S. 3923-3930 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Following the development of an improved theoretical analysis of fibre pull-out on the basis of the concept of fracture mechanics in Part II of this paper, the theory has been successfully used to characterize the debonding and frictional pull-out behaviour in cement mortar matrix composites reinforced with steel and glass fibres. It is shown from the plots of partial debond stress, σ d p , versus debond length, ℓ, that these composites are typical of mechanical bonds at the interface. For the steel fibre-cement matrix composites, the theory overestimates the post-debond frictional pull-out stress, σfr, particularly for long embedded fibre length, L, otherwise the prediction agrees well with the experiments for the maximum debond stress, σ d * . This seems to be a direct result of decay of frictional bonds at the interface region after debonding due mainly to compaction of the porous cement mortar surrounding the fibre, effectively reducing the residual clamping stress, q 0, arising from shrinkage of the cement matrix. Therefore, a correct theoretical prediction is made for σfr using a lower value of q 0 while other parameters are kept constant, which gives good agreement with experimental results. For glass fibre-cement matrix composites, an accelerated cure condition promotes rapid hydration of cement and densification of the matrix. This effectively improves the chemical as well as mechanical bonds at the fibre-matrix interface through the formation of CH crystals and large fibre-solid matrix contact area of the interface, and consequently ameliorating the interfacial properties, interfacial fracture toughness, G ic and q o in particular. Predictions of σ d * and σfr taking into account these changes due to cure condition, results in good agreement with experimental results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF00353200
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  • 7
    Electronic Resource
    Electronic Resource
    Interfacial debonding and fibre pull-out stresses (1992)
    Springer
    Journal of materials science 27 (1992), S. 3155-3166 
    Details
    ISSN: 1573-4803
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract An improved analysis has been developed for the interfacial debond stress in a fibre pull-out model based on the concept of fracture mechanics where the debonded region is considered as an interfacial crack and its extension is dependent on a fracture energy criterion being satisfied. By evaluating the partial debond stress, σ d p against debond lengthl, during progressive debonding, instability conditions are derived where the maximum debond stress, σ d * , is determined for different embedded fibre length,L. Comparisons between theory and experimental fibre pullout results on several composite systems show that the present model gives excellent prediction of the maximum debond stress, σ d * , for the whole range ofL including even the very shortL, whereas the previous Gao-Mai-Cotterell model, also developed on the basis of a fracture mechanics approach, always overestimates σ d * for shortL and gives a finite value forL=0. The initial frictional pull-out stress, σfr, after complete debonding predicted by the present model is basically the same as the Gao-Mai-Cotterell model and agrees well with experiments. The implications of stress distributions in the constituents for different composite systems are discussed on the basis of the proposed debond criterion.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01116005
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  • 8
    Electronic Resource
    Electronic Resource
    The flexible termini of conantokin G define its interactions with NMDA receptors (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 85-93 
    Details
    ISSN: 1573-3904
    Keywords: Conformation ; Inhibition ; Peptide ligand ; Polyamine binding site
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Summary Converging lines of evidence suggest that theN-methyl-d-aspartic acid (NMDA) antagonist properties of conantokin G (ConG) are mediated through a novel polyamine-associated site. Moreover, structural modification of the heptadecapeptide yields peptides that can either mimic the NMDA antagonist properties of the parent peptide or produce polyamine-like actions at NMDA receptors. We synthesized a panel of ConG fragments and evaluated their effects using a neurochemical assay that predicts pharmacological actions at NMDA receptors. While the C-terminal tetrapeptide elicited a polyamine-like activation of [3H]MK-801 binding with a potency comparable to spermine, the N-terminal pentapeptide produced a marginal inhibition of spermine-enhanced [3H]MK-801 binding. These observations suggest that the parent peptide interacts with two distinct sites on NMDA receptors. In contrast, amino acid replacements in the middle region of ConG resulted in analogues that were of comparable or greater potency than the parent peptide. The Ala7, Tyr10 derivative is of particular interest since it is a potent inhibitor (IC50≈80 nM) of spermine-enhanced [3H]MK-801 binding, and may thus serve as a precursor for studies designed to125I-label putative ConG binding sites. Our observations are also consistent with the hypothesis that the termini of ConG are essential for an interaction with NMDA receptors, while the middle region of this peptide serves as a spacer unit. This hypothesis is consonant with spectroscopic evidence that ConG possesses a central rigid helical backbone with flexible N- and C-terminal regions. Nonetheless, ConG variants in which the termini were connected with conformationally stabilized α-or 310-helical spacers grew progressively less potent as NMDA antagonists as the structural stability of these peptides increased. Thus, the middle region of ConG appears to possess functions other than providing conformational stability. These newly synthesized ConG derivatives may serve as a basis for the design of novel peptide or peptidomimetic agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02443519
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  • 9
    Electronic Resource
    Electronic Resource
    The flexible termini of conantokin G define its interactions with NMDA receptors (1997)
    Springer
    International journal of peptide research and therapeutics 4 (1997), S. 85-93 
    Details
    ISSN: 1573-3904
    Keywords: Conformation ; Inhibition ; Peptide ligand ; Polyamine binding site
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Converging lines of evidence suggest that the N-methyl-D-aspartic acid (NMDA) antagonistproperties of conantokin G (ConG) are mediated through a novel polyamine-associated site.Moreover, structural modification of the heptadecapeptide yields peptides that can eithermimic the NMDA antagonist properties of the parent peptide or produce polyamine-likeactions at NMDA receptors. We synthesized a panel of ConG fragments and evaluated theireffects using a neurochemical assay that predicts pharmacological actions at NMDA receptors.While the C-terminal tetrapeptide elicited a polyamine-like activation of [3H]MK-801 bindingwith a potency comparable to spermine, the N-terminal pentapeptide produced a marginalinhibition of spermine-enhanced [3H]MK-801 binding. These observations suggest that theparent peptide interacts with two distinct sites on NMDA receptors. In contrast, amino acidreplacements in the middle region of ConG resulted in analogues that were of comparable orgreater potency than the parent peptide. The Ala7,Tyr10 derivative is of particular interestsince it is a potent inhibitor (IC50 ∼ 80 nM) of spermine-enhanced [3H]MK-801 binding, andmay thus serve as a precursor for studies designed to 125I-label putative ConG binding sites.Our observations are also consistent with the hypothesis that the termini of ConG are essentialfor an interaction with NMDA receptors, while the middle region of this peptide serves as aspacer unit. This hypothesis is consonant with spectroscopic evidence that ConG possessesa central rigid helical backbone with flexible N- and C-terminal regions. Nonetheless, ConGvariants in which the termini were connected with conformationally stabilizedα- or 310-helical spacers grew progressively less potent as NMDA antagonists as the structural stabilityof these peptides increased. Thus, the middle region of ConG appears to possess functionsother than providing conformational stability. These newly synthesized ConG derivatives mayserve as a basis for the design of novel peptidic or peptidomimetic agents.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008830104111
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  • 10
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    Access to Microloans for Households with Forest Property Collateral in China (2016)
    Springer
    Details
    Publication Date: 2016-02-20
    Print ISSN: 1873-7617
    Electronic ISSN: 1873-7854
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Published by Springer
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