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  • 1
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    Springer Nature | Springer
    Publication Date: 2024-04-05
    Description: This open access book offers the first comprehensive account of the pan-genome concept and its manifold implications. The realization that the genetic repertoire of a biological species always encompasses more than the genome of each individual is one of the earliest examples of big data in biology that opened biology to the unbounded. The study of genetic variation observed within a species challenges existing views and has profound consequences for our understanding of the fundamental mechanisms underpinning bacterial biology and evolution. The underlying rationale extends well beyond the initial prokaryotic focus to all kingdoms of life and evolves into similar concepts for metagenomes, phenomes and epigenomes. The book’s respective chapters address a range of topics, from the serendipitous emergence of the pan-genome concept and its impacts on the fields of microbiology, vaccinology and antimicrobial resistance, to the study of microbial communities, bioinformatic applications and mathematical models that tie in with complex systems and economic theory. Given its scope, the book will appeal to a broad readership interested in population dynamics, evolutionary biology and genomics.
    Keywords: Microbial Genetics and Genomics ; Evolutionary Biology ; Genetics and Population Dynamics ; Microbial Ecology ; Human Genetics ; Genetics and Genomics ; Comparative genomics ; Metagenomics ; Microbial Population Analysis ; Pangenome Profile ; Supra-Genome Analysis ; Adaptive Evolution ; Computational Tools ; Bioinformatic Genomics ; Core Dispensable Genome ; Selection, Recombination, Composition ; Acquired Resistance ; Bacterial Species Concept ; Genomic Diversity ; Bacterial Ecology, Microevolution ; Open Access ; Pan-metagenomics ; Pan-microbiomics ; Pan-epigenome ; Gene Transfer ; Pan-phenomes ; Microbiology (non-medical) ; Genetics (non-medical) ; Evolution ; Applied mathematics ; Ecological science, the Biosphere ; Medical genetics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSG Microbiology (non-medical) ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAJ Evolution ; thema EDItEUR::P Mathematics and Science::PB Mathematics::PBW Applied mathematics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAF Ecological science, the Biosphere ; thema EDItEUR::M Medicine and Nursing::MF Pre-clinical medicine: basic sciences::MFN Medical genetics ; thema EDItEUR::P Mathematics and Science::PS Biology, life sciences::PSA Life sciences: general issues::PSAK Genetics (non-medical)
    Language: English
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  • 2
    Publication Date: 2020-11-12
    Description: Slope dynamics in volcanic environments comprise a wide spectrum of phenomena, from large lateral collapse to shallow debris remobilization, which may represent a major threat for human communities and infrastructures. Many volcanos built up from the ocean floor and large portions of the volcano edifice are submerged. In these settings, only the edifice’s summit can be investigated by terrestrial remote sensing and in-situ approaches. Growth and destruction, including tectonics and gravitational phenomena, affect entire volcano flanks and are not limited to the physical boundary of the sea level but could comprise their subaqueous parts.
    Description: Published
    Description: 2615–2618
    Description: 6V. Pericolosità vulcanica e contributi alla stima del rischio
    Description: JCR Journal
    Keywords: volcanoes ; flanks ; volcano-tectonics ; structure ; collapse ; stability ; 04.08. Volcanology ; 05.08. Risk
    Repository Name: Istituto Nazionale di Geofisica e Vulcanologia (INGV)
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  • 3
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    Circuits, systems and signal processing 19 (2000), S. 423-435 
    ISSN: 1531-5878
    Keywords: Time-varying autoregressive models ; stability ; smoothness priors ; Tihkonov regularization ; constrained optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The stability of time-varying autoregressive (AR) models is an important issue in such applications as time-varying spectrum estimation and electroencephalography simulation and estimation. In some cases, such as time-varying spectrum estimation, the models that exhibit roots near unit moduli are difficult to use. Thus a tighter stability condition such as stability with a positive margin is needed. A time-varying AR model is stable with a positive margin if the moduli of the roots of the time-varying characteristic polynomial are somewhat less than unity for every time instant. Recently, a new method for the estimation of the time-varying AR models was introduced. This method is based on the interpretation of the underdetermined time-varying prediction equations as an ill-posed inverse problem that is solved by Tikhonov regularization. The method is referred to as the deterministic regression smoothness priors (DRSP) scheme. In this paper, a stabilization method in which the DRSP scheme is augmented with nonlinear stability constrainst is proposed. The problem is formulated so that stability with a positive margin can also be achieved. The problem is solved iteratively with an exterior point algorithm. The performance of the algorithm is studied with a simulation. It is shown that the proposed approach is well suited to stable modeling of signals containing narrowband transitions.
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  • 4
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    Circuits, systems and signal processing 19 (2000), S. 13-25 
    ISSN: 1531-5878
    Keywords: Singular systems ; delay ; consistency condition ; stability ; instability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper, the general class of singular systems with delay and linear constant coefficient singular systems with delay are discussed. First, several definitions of stability are presented for singular systems with delay, and general sufficient stability conditions and instability conditions are obtained. Second, stability and instability are analyzed for linear constant coefficient singular systems with delay.
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  • 5
    ISSN: 1570-7458
    Keywords: butterfly ; Formicidae ; food ; growth ; mutualism ; myrmecophily ; parasitism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Caterpillars of the lycaenid butterfly Maculinea rebeli Hirschke (Lepidoptera: Lycaenidae) live for 11–23 months as social parasites in Myrmica (Hymenoptera: Formicidae) red ant nests, a trait that is believed to have evolved from mutualistic myrmecophilous ancestry. Although Maculinea rebeli caterpillars harm Myrmica larvae, they simultaneously produce copious secretions which the adult worker ants imbibe, perhaps representing a vestige of the ancestral mutualism. We report the results of laboratory experiments designed to test alternative hypotheses: (i) Maculinea rebeli caterpillars provide a beneficial source of sugar in return for being tended by Myrmicaworkers; (ii) Maculinea rebeli harms its host by stressing the workers by competing for available sugar. Comparisons were made of Myrmica worker fitness after 90–450 days under all possible combinations of three experimental treatments: ± M. rebeli caterpillars, ± sucrose and ± ant brood. Caterpillars always reduced the survival of both ant workers and their larvae, even when sugar was not provided, suggesting that M. rebeli is wholly parasitic on all stages in its host colony. The results also confirmed the importance of sucrose in the diet of Myrmica, and showed that M. rebeli caterpillars which eat ant brood to supplement their normal trophallactic feeding by workers develop more quickly - but have the same survival and pupal weights – as caterpillars that are fed solely by worker ants.
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  • 6
    ISSN: 1570-7458
    Keywords: EPG ; stylectomy ; phloem amino acids ; nitrogen ; aphid-plant interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Effects of nitrogen deficiency in hydroponically grown barley seedlings (Hordeum vulgare L.) on the development and reproduction of the aphid Rhopalosiphum padi (L.) (Hemiptera: Aphididae) were investigated. Plant growth was significantly reduced in seedlings grown without nitrogen. Aphid intrinsic rate of increase (r m) was also significantly lower on these plants compared with that on plants grown with 8 mol m−3 nitrogen. Phloem sap was collected from seedling stems by aphid stylectomy and amino acids quantified by HPLC. There was a significant reduction in the concentration of non-essential amino acids as a group, but not of essential amino acids. Electrical penetration graphs (EPG) indicated that aphids reached the phloem more quickly and fed for longer on plants grown with nitrogen. This is the first reported study in which this combination of techniques has been used to understand the interactions of an aphid and plant under different environmental conditions.
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  • 7
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    Acta biotheoretica 48 (2000), S. 207-218 
    ISSN: 1572-8358
    Keywords: Dynamical population ; fishing efforts ; metapopulation ; time scales ; aggregation method ; equilibrium ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities.
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  • 8
    ISSN: 1572-8862
    Keywords: acetylene ion ; complex ; hydrogen ; nitrogen ; argon
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The complexes formed by the positive acetylene ion with the hydrogen molecule, the nitrogen molecule, and the argon atom are investigated with ab initio calculations using the 6-311G** and the 6-31+G(2df,2pd) basis sets. MP2/6-311G** energies and optimum geometries are obtained, as well as single-point MP3, MP4, and QCISD(T) energies with the MP2/6-311G** optimized geometries. Single-point calculations are performed with the 6-31+G(2df,2pd) basis set at MP2/6-311G** optimized geometries.
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  • 9
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    Queueing systems 34 (2000), S. 1-35 
    ISSN: 1572-9443
    Keywords: multiple access ; CDMA ; rates of convergence ; stability ; functional limit theorems ; transient analysis ; Markov-modulated capture channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the slotted ALOHA protocol on a channel with a capture effect. There are M 〈 ∞ users each with an infinite buffer. If in a slot, i packets are transmitted, then the probability of a successful reception of a packet is q i. This model contains the CDMA protocols as special cases. We obtain sufficient rate conditions, which are close to necessary for stability of the system, when the arrival streams are stationary ergodic. Under the same rate conditions, for general regenerative arrival streams, we obtain the rates of convergence to stationarity, finiteness of stationary moments and various functional limit theorems. Our arrival streams contain all the traffic models suggested in the recent literature, including the ones which display long range dependence. We also obtain bounds on the stationary moments of waiting times which can be tight under realistic conditions. Finally, we obtain several results on the transient performance of the system, e.g., first time to overflow and the limits of the overflow process. We also extend the above results to the case of a capture channel exhibiting Markov modulated fading. Most of our results and proofs will be shown to hold also for the slotted ALOHA protocol without capture.
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  • 10
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    Celestial mechanics and dynamical astronomy 78 (2000), S. 227-241 
    ISSN: 1572-9478
    Keywords: stability ; normal form ; spin-orbit resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider a model of spin-orbit interaction, describing the motion of an oblate satellite rotating about an internal spin-axis and orbiting about a central planet. The resulting second order differential equation depends upon the parameters provided by the equatorial oblateness of the satellite and its orbital eccentricity. Normal form transformations around the main spin-orbit resonances are carried out explicitly. As an outcome, one can compute some invariants; the fact that these quantities are not identically zero is a necessary condition to prove the existence of nearby periodic orbits (Birkhoff fixed point theorem). Moreover, the nonvanishing of the invariants provides also the stability of the spin-orbit resonances, since it guarantees the existence of invariant curves surrounding the periodic orbit.
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  • 11
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    Journal of computational analysis and applications 2 (2000), S. 293-308 
    ISSN: 1572-9206
    Keywords: parabolic equations ; ADI scheme ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An ADI scheme for solving three-dimensional parabolic equations withfirst-order derivatives and variable coefficients has been developed basedon our previous papers and the idea of the modified upwind differencescheme. This ADI scheme is second-order accurate and unconditionallystable. Further, a small parameter can be chosen which makes it suitablefor simulating fast-transient phenomena or for computations on fine spatialmeshes. The method is illustrated with numerical examples.
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  • 12
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    Queueing systems 36 (2000), S. 327-349 
    ISSN: 1572-9443
    Keywords: multiclass networks ; networks with feedback ; Skorokhod Problem ; Skorokhod Mapping ; Lipschitz continuity ; stability ; load conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider a four-class two-station network with feedback, with fluid inputs and a head-of-the-line generalized processor sharing discipline at each station. We derive the Skorokhod Problem associated with the network and obtain algebraic sufficient conditions for Lipschitz continuity of the associated Skorokhod Map. This provides the first example of a multiclass network with feedback for which the associated Skorokhod Problem has been proved to be regular. As an elementary application, we show that under the conditions which guarantee Lipschitz continuity the network is stable if and only if the usual load conditions apply.
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  • 13
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    Journal of dynamics and differential equations 12 (2000), S. 117-167 
    ISSN: 1572-9222
    Keywords: singular perturbation ; standing pulses ; stability ; Hopf bifurcation ; reaction-diffusion system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Bifurcation phenomena from standing pulse solutions of the problem $$\varepsilon \tau u_t = \varepsilon ^2 u_{xx} + f(u,v),{\text{ }}v_t = v_{xx} + g(u,v)$$ is considered. ε(〉0) is a sufficiently small parameter and τ is a positive one. It is shown that there exist two types of destabilization of standing pulse solutions when τ decreases. One is the appearance of travelling pulse solutions via the static bifurcation and the other is that of in-phase breathers via the Hopf bifurcation. Furthermore which type of destabilization occurs first with decreasing τ is discussed for the piecewise linear nonlinearities f and g.
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  • 14
    ISSN: 1572-879X
    Keywords: aluminum oxide ; hydroxyl groups ; rhodium ; growth ; scanning tunneling microscopy ; infrared spectroscopy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In order to investigate how the presence of surface hydroxyl groups on oxide surfaces affects the interaction with the supported metal, we have modified a well-ordered alumina film on NiAl(110) by Al deposition and subsequent exposure to water. This procedure yields a hydroxylated alumina surface as revealed by infrared and high-resolution electron energy loss spectroscopy. By means of scanning tunneling microscopy, we have studied the growth of rhodium on the modified film at 300 K. Clear differences in the particle distribution and density are observed in comparison to the clean substrate. While, in the latter case, decoration of domain boundaries as typical defects of the oxide film governs the growth mode, a more isotropic island distribution and a drastically increased particle density is found on the hydroxylated surface. From infrared data, it can be deduced that the growth is connected with the consumption of the hydroxyl groups due to the interaction between the metal deposit and the hydroxylated areas. This finding is in line with photoemission results published earlier.
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  • 15
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    Catalysis letters 68 (2000), S. 55-58 
    ISSN: 1572-879X
    Keywords: promoting effect ; B2O3 ; Cu/ZnO/Al2O3 catalyst ; methanol synthesis ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The addition of B2O3 to a Cu/ZnO/Al2O3 catalyst increased the activity of the catalyst for methanol synthesis after an induction period during the reaction. The stability of the B2O3-containing Cu/ZnO/Al2O3 catalyst was greatly improved by the addition of a small amount of colloidal silica to the catalyst.
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  • 16
    ISSN: 1572-879X
    Keywords: potassium desorption ; stability ; excitation ; iron catalyst ; Rydberg atoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Well‐characterized catalyst model compounds of KAlO2 and KFeO2 are investigated by thermal desorption of potassium from the material. The desorbing fluxes of ions, atoms and highly excited states (field ionizable Rydberg states) were studied with surface and field ionization detectors in a vacuum apparatus. From the Arrhenius plots the activation energies for desorption of K and K+ were determined. The chemical state of potassium at the surfaces is concluded to be: ionic on KAlO2 (with the K desorption barrier of 1.76 eV) and covalent on KFeO2 (barrier of 2.73 eV). These results agree with the data obtained earlier for industrial catalysts for ammonia and styrene production. They are interpreted in terms of the Schottky cycle, which is completed for KAlO2 and fails for KFeO2. This failure indicates a non‐equilibrium desorption process. K Rydberg states are only found to desorb from KFeO2, in agreement with the suggestion that such states in some way are responsible for the catalytic activity.
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  • 17
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    Set-valued analysis 8 (2000), S. 253-266 
    ISSN: 1572-932X
    Keywords: Hausdorff metric ; linear inequality systems ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we propose a Hausdorff metric to measure the “distance” between two linear inequality systems on a real normed space X. For this topology, which comes through a pseudo-metric in the set Σ of linear inequality systems, the closedness of the feasible set mapping is studied, and at the same time a characterization of the stability of the subset Σ c of consistent sytems is given.
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  • 18
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    Annals of operations research 99 (2000), S. 251-265 
    ISSN: 1572-9338
    Keywords: stochastic programming ; bond portfolio management ; interest ratescenarios ; stability ; sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The bond portfolio management problem is formulated as a multiperiod two-stage or multistage stochastic program based on interest rate scenarios. These scenarios depend on the available market data, on the applied estimation and sampling techniques, etc., and are used to evaluate coefficients of the resulting large scale mathematical program. The aim of the contribution is to analyze stability and sensitivity of this program on small changes of the coefficients – the (scenario dependent) values of future interest rates and prices. We shall prove that under sensible assumptions, the scenario subproblems are stable linear programs and that also the optimal first-stage decisions and the optimal value of the considered stochastic program possess acceptable continuity properties.
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  • 19
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    Applications of mathematics 45 (2000), S. 161-176 
    ISSN: 1572-9109
    Keywords: reaction-diffusion system ; unilateral conditions ; quasivariational inequality ; Leray-Schauder degree ; eigenvalue ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We consider a reaction-diffusion system of the activator-inhibitor type with unilateral boundary conditions leading to a quasivariational inequality. We show that there exists a positive eigenvalue of the problem and we obtain an instability of the trivial solution also in some area of parameters where the trivial solution of the same system with Dirichlet and Neumann boundary conditions is stable. Theorems are proved using the method of a jump in the Leray-Schauder degree.
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  • 20
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    Advances in computational mathematics 12 (2000), S. 229-250 
    ISSN: 1572-9044
    Keywords: numerical analysis ; shallow water problems ; DIRK methods ; stability ; 65L06 ; 65L20 ; 65M12 ; 65M20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We construct A‐stable and L‐stable diagonally implicit Runge–Kutta methods of which the diagonal vector in the Butcher matrix has a minimal maximum norm. If the implicit Runge–Kutta relations are iteratively solved by means of the approximately factorized Newton process, then such iterated Runge–Kutta methods are suitable methods for integrating shallow water problems in the sense that the stability boundary is relatively large and that the usually quite fine vertical resolution of the discretized spatial domain is not involved in the stability condition.
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  • 21
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    BIT 40 (2000), S. 62-73 
    ISSN: 1572-9125
    Keywords: Gaussian elimination ; stability ; pivoting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It has been recently shown that large growth factors might occur in Gaussian Elimination with Partial Pivoting (GEPP) also when solving some plausibly natural systems. In this note we argue that this potential problem could be easily solved, with much smaller risk of failure, by very small (and low cost) modifications of the basic algorithm, thus confirming its inherent robustness. To this end, we first propose an informal model with the goal of providing further support to the comprehension of the stability properties of GEPP. We then report the results of numerical experiments that confirm the viewpoint embedded in the model. Basing on the previous observations, we finally propose a simple scheme that could be turned into (even more) accurate software for the solution of linear systems.
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  • 22
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    BIT 40 (2000), S. 611-639 
    ISSN: 1572-9125
    Keywords: Runge-Kutta methods ; stability ; convergence ; stiff problems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper studies the stability and convergence properties of general Runge-Kutta methods when they are applied to stiff semilinear systems y′(t) = J(t)y(t) + g(t, y(t)) with the stiffness contained in the variable coefficient linear part. We consider two assumptions on the relative variation of the matrix J(t) and show that for each of them there is a family of implicit Runge-Kutta methods that is suitable for the numerical integration of the corresponding stiff semilinear systems, i.e. the methods of the family are stable, convergent and the stage equations possess a unique solution. The conditions on the coefficients of a method to belong to these families turn out to be essentially weaker than the usual algebraic stability condition which appears in connection with the B-stability and convergence for stiff nonlinear systems. Thus there are important RK methods which are not algebraically stable but, according to our theory, they are suitable for the numerical integration of semilinear problems. This paper also extends previous results of Burrage, Hundsdorfer and Verwer on the optimal convergence of implicit Runge-Kutta methods for stiff semilinear systems with a constant coefficients linear part.
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    BIT 40 (2000), S. 226-240 
    ISSN: 1572-9125
    Keywords: Stochastic differential equations ; regularisation ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper is devoted to the numerical analysis of ill-posed problems of evolution equations in Banach spaces using certain classes of stochastic one-step methods. The linear stability properties of these methods are studied. Regularisation is given by the choice of the regularisation parameter as α = $$\sqrt {\tau _n }$$ , where τ n is the stepsize and provides the convergence on smooth initial data. The case of the approximation of well-posed problems is also considered.
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  • 24
    ISSN: 1432-1211
    Keywords: Key words Antigen presentation ; Autoimmune disease ; Evolution ; MHC ; Self peptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Comparison of peptides eluted from human class I and class II major histocompatibility complex (MHC) molecules and the proteins from which they are derived (source proteins) revealed that class I MHC bind peptides derived from proteins that are highly conserved, hydrophilic, and universally expressed, while the peptides themselves are hydrophobic and even more conserved than their source proteins. In contrast, source proteins for class II-bound peptides were not significantly more conserved than a random sample of proteins. Class II-bound peptides were generally more conserved than their source proteins but were significantly less conserved than class I-bound peptides. The characteristics of class I-bound peptides can probably be explained by the selectivity of processing and transport of peptides for binding by class I, while the relative lack of selectivity of peptide binding for class II may explain the high incidence of autoimmune diseases associated with alleles of these molecules.
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  • 25
    ISSN: 1432-1211
    Keywords: Key words iNOS ; Fish ; Parasite ; Evolution ; Transcription
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Using an oligonucleotide primer based on a partial goldfish inducible nitric oxide synthase (iNOS) sequence, a complete carp iNOS cDNA was isolated from an activated carp phagocyte cDNA library. Nucleotide and predicted amino acid sequence analysis indicate that carp iNOS encodes a 1127-amino acid protein with 57% sequence identity to human iNOS. Like mammalian NOSs, carp iNOS protein contains putative binding sites for heme, tetrahydrobiopterin, calmodulin, flavine mononucleotide, flavine adenine dinucleotide, and NADPH. Phylogenetic analysis, using neighbor joining, showed that the carp iNOS protein clustered together with the other vertebrate iNOS proteins. Inducibility of carp iNOS was confirmed by reverse transcription-polymerase chain reaction after stimulation of carp phagocytes with lipopolysaccharide or the protozoan blood flagellate Trypanoplasma borreli. These stimulators produced high amounts of nitric oxide that were toxic for T. borreli in vitro. The nuclear transciption factor NF-κB was shown to play a role in the induction of iNOS transcription.
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  • 26
    ISSN: 1432-1211
    Keywords: Key words HLA ; Patr class I molecules ; Evolution ; Polymorphism ; AIDS
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Human immunodefiency virus (HIV) poses a major threat to humankind. And though, like humans, chimpanzees are susceptible to HIV infection, they are considered to be resistant to the development of the acquired immune deficiency syndrome (AIDS). Little is known about major histocompatibility complex (MHC) class I diversity in chimpanzee populations and, moreover, whether qualitative aspects of Patr class I molecules may control resistance to AIDS. To address these questions, we assayed MHC class I diversity in a West African chimpanzee population and in some animals from other subspecies of chimpanzee. Application of different techniques allowed the detection of 17 full-length Patr-A, 19 Patr-B, and 10 Patr-C alleles. All Patr-A alleles cluster only into the HLA-A1/A3/A11 family, which supports the idea that chimpanzees have experienced a reduction in their repertoire of A locus alleles. The Patr-B alleles do not cluster in the same lineages as their human equivalents, due to frequent exchange of polymorphic sequence motifs. Furthermore, polymorphic motifs may have been exchanged between Patr-A and Patr-B loci, resulting in convergence. With regard to evolutionary stability, the Patr-C locus is more similar to the Patr-A locus than it is to the Patr-B locus. Despite the relatively low number of animals analyzed, humans and chimpanzees were ascertained as sharing similar degrees of diversity at the contact residues constituting the B and F pockets in the peptide-binding side of MHC class I molecules. Our results indicate that within a small sample of a West African chimpanzee population, a high degree of Patr class I diversity is encountered. This is in agreement with the fact that chimpanzees display more mitochondrial DNA variation than humans. In addition, population analyses demonstrated that particular Patr-B molecules, with the capacity to bind conserved HIV-1 epitopes, are characterized by high gene frequencies. These findings have important implications for evaluating immune responses in HIV vaccine studies and, more importantly, may help in understanding the relative resistance of chimpanzees to AIDS.
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  • 27
    ISSN: 1432-1211
    Keywords: Key words HLA genes ; IgV genes ; Evolution ; Gene conversion ; Sheep ileal Peyer's patch
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Polymorphic sequence variation in the peptide-binding domains of MHC class I molecules appears to have been driven largely by the constructive action of natural selection on the specificity of the peptide-binding groove. Similar features are displayed by the variable domains of immunoglobulins generated in the sheep ileal Peyer's patch, but in this case there is evidence that the action of a targeted hypermutator acting on a selected substrate rather than antigen-driven selection is responsible for the pattern of variation in the system. Such a hypermutator acting in the germ line would not only mimic the action of natural selection but also, by convergent mutation, generate similar patterns of variation in unrelated alleles that could be interpreted as evidence for short-tract gene conversion. We analyzed human class I MHC alleles in the light of these data, but failed to find evidence of the action of a similar hypermutator. A search for other mutationally driven patterns of variation also failed, even in hypervariable residues from parsimonious phylogenies. Single-nucleotide variation at these residues is also frequent in recent allelic variants, but the data are as consistent with short-tract gene conversion as with base mutation. We conclude that the patterns of allelic variation in MHC molecules are not driven by mutational pressure, but rather by conventional mutational processes, accompanied by short-tract gene conversion and intense natural selection.
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    Immunogenetics 51 (2000), S. 587-590 
    ISSN: 1432-1211
    Keywords: Key words J chain ; Immunoglobulin ; Amphibian ; Evolution ; Comparative immunology
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    Immunogenetics 51 (2000), S. 606-609 
    ISSN: 1432-1211
    Keywords: Key words MHC ; Evolution ; Primate ; Callithrix ; Callicebus
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    Mycorrhiza 10 (2000), S. 145-149 
    ISSN: 1432-1890
    Keywords: Keywords Arbuscular mycorrhiza ; Pteridophyte ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The percentage of arbuscular mycorrhizal pteridophytes among 256 pteridophyte species distributed in Yunnan (southwest China) was found to be lower than that in angiosperms. In the pteridophytes, the occurrence of arbuscular mycorrhizas was low in sporophytes of fern-allies and leptosporangiates, whereas in the eusporangiates it was relatively high. From the standpoint of mycotrophism, the evolutionary trend in the Filicineae may be from constantly mycorrhizal to facultative mycorrhizal and finally to nonmycorrhizal plants.
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    Archive of applied mechanics 70 (2000), S. 17-29 
    ISSN: 1432-0681
    Keywords: Key words free-surface flow ; solidification ; strip casting ; steady state ; nonuniqueness ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The paper is concerned with a one-dimensional analysis of plane open-channel flow with continuous solidification. The process is of relevance for recent developments in the casting of steel and other metals. The bottom of the channel consists of a rotating casting roll and a horizontal cooling table, where the solidified material is withdrawn with given velocity. The study is restricted to the region downstream of the top of the casting roll. Surface tension is neglected. In the main part of the analysis inviscid fluid flow is considered since the Reynolds number is very large in the applications. It is found that the steady-state solutions are nonunique in a certain parameter range. In addition to a continuous solution, there are two solutions including hydraulic jumps, with one hydraulic jump being located on the casting roll, the other one on the cooling table. Regarding the stability of the non unique solutions, the evolution of disturbances is investigated numerically as an initial-value problem. It is concluded that the hydraulic jump on the cooling table is unstable, while the other discontinuous solution as well as the continuous solution are stable for sufficiently small disturbances. Which stable solution is attained in the steady state, depends on the history of the process. Friction at the liquid/solid interface is taken into account in the last part of the analysis. A constant friction coefficient is assumed. It is found that the history of the process determines the steady-state solution if, and only if, the friction coefficient is sufficiently small. For larger values of the friction coefficient, the steady-state solution is unique and independent of the history of the transient process. Furthermore, for sufficiently large friction coefficients, stable hydraulic jumps are found, in contrast to the inviscid case, also on the cooling table.
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    Journal of comparative physiology 186 (2000), S. 105-118 
    ISSN: 1432-1351
    Keywords: Key words Stomatogastric nervous system ; Penaeus ; Motor pattern ; Neural network ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  Motor patterns of the cardiac sac, the gastric and the pyloric network in the stomatogastric nervous system of the shrimp Penaeus japonicus, the most primitive decapod species, were studied. Single neurons can switch from the gastric or the pyloric pattern to the cardiac sac pattern. Some of the pyloric neurons fire with the gastric pattern. All of the gastric neurons fire with the pyloric pattern, unlike those in reptantians. Proctolin activates and modulates the cardiac sac and the pyloric rhythm, and promotes reconfiguration of the networks. Neurons of the three networks have so many interconnections that they construct a multifunctional neural network like those in Cancer. This network may function in different configurations under the appropriate conditions. Several modes of interactions between the networks found in different reptantian species can apply to the penaeidean shrimp. Such interactions are general features of the stomatogastric nervous system in decapods. Phylogenetic differences among the decapod infraorders are seen in the number and orientation of muscles and the innervation pattern of muscles. The multifunctional networks have existed in the most primitive decapod species, and types of configurations of the networks would have evolved to produce a wide range of motor patterns as the foregut structure has become complex.
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    Journal of intelligent and robotic systems 27 (2000), S. 195-209 
    ISSN: 1573-0409
    Keywords: wall-climbing robot ; electromagnetic grippers ; stability ; additional support element ; sliding and turning over conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Legged-climbing robot is considered. Each foot of the robot has an electromagnet system for robot"s holding on a metal surface. This surface can be both vertical and inclined, including negative slope. Analytical calculation of robot stability under turn over or sliding conditions has been made. Critical slopes have been determined. One of these slopes corresponds to minimal reserve of robot stability towards sliding and another to minimal reserve of robot stability towards turning-over. As total reserve of stability of a robot is always equal to the minimal one of these reserves. Additional support elements of elastic material with high coefficient of friction, along with electromagnet, allows to increase minimal reserve of robot stability towards sliding. The use of such support elements leads to redistributing force of normal support reaction between electromagnet (which surface has low coefficient of friction) and additional support element (which surface has high coefficient of friction). It is just what leads to increasing the total friction force and as a consequence to increasing of minimal reserve of robot stability towards sliding.
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    Letters in mathematical physics 53 (2000), S. 313-320 
    ISSN: 1573-0530
    Keywords: partial differential equations ; nonlinearities ; symmetries ; stability ; minimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We suggest a simple but general method of establishing symmetry properties of stable solutions of nonlinear elliptic equations. The method relies on characterization of symmetry breaking with a help of zero modes and on a generalization of the Perron–Frobenius theory.
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    Nutrient cycling in agroecosystems 56 (2000), S. 139-152 
    ISSN: 1573-0867
    Keywords: nitrogen ; N leaching ; liquid manure ; catch crops ; N mineralization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Results are presented from five years (1990–1995) of a field leaching experiment on a sandy soil in south-west Sweden. The aim was to study N leaching, change in soil organic N and N mineralization in cropping systems with continuous use of liquid manure (two application rates) and catch crops. N leaching from drains, N uptake in crops and mineral N in the soil were measured. Simulation models were used to calculate the N budget and N mineralization in the soil and to make predictions of improved fertilization strategies in relation to manure applications and changing the time for incorporation of catch crops. In treatments without catch crops, a normal and a double application of manure increased average N leaching by 15 and 34%, respectively, compared to treatment with commercial fertilizer. Catch crops reduced N leaching by, on average, 60% in treatments with a normal application of manure and commercial fertilizer, but only by 35% in the treatment with double the normal application rate of manure. Incorporation of catch crops in spring increased simulated net N mineralization during the crop vegetation period, and also during early autumn. In conclusion, manured systems resulted in larger N leaching than those receiving commercial fertilizer, mainly due to larger applications of mineral N in spring. More careful adaptation of commercial N fertilization with respect to the amounts of NH4-N applied with manure could, according to the simulations, reduce N leaching. Under-sown ryegrass catch crops effectively reduced N leaching in manured systems. Incorporating catch crop residues in late autumn instead of spring might be preferable with respect to N availability in the soil for the next crop, and would not increase N leaching.
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    Small business economics 14 (2000), S. 195-210 
    ISSN: 1573-0913
    Keywords: growth ; manufacturing ; performance ; product innovation ; small firms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Economics
    Notes: Abstract The paper considers the relative performance [along a number of parameters] of a sample of 228 small manufacturing firms categorised by level of innovation. Whilst innovators appear no more likely to have experienced some form of sales or employment growth, they are significantly more likely to have grown more. In other words, the innovators' growth rate distributions are highly negatively skewed. With regards to export intensities, profitability and productivity levels, the findings are less clear. On the whole, the results reported here are similar to those of other small firm studies, yet vary markedly from large firm equivalents; suggesting that the nature of the returns to innovation may be contingent, at least in part, upon firm size. Moreover, the high levels of variation in firm performance should caution us against proffering innovative imperatives. If we are to counsel firms to "innovate at all costs", we must be clear about, and clearly demonstrate, the nature of the returns they may reasonably expect and the processes through which these may be optimised.
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    Journal of statistical physics 101 (2000), S. 731-746 
    ISSN: 1572-9613
    Keywords: attractive Bose–Einstein condensates ; nonlinear Schrödinger equation ; stability ; ground state ; variational arguments
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    Topics: Physics
    Notes: Abstract We propose the critical nonlinear Schrödinger equation with a harmonic potential as a model of attractive Bose–Einstein condensates. By an elaborate mathematical analysis we show that a sharp stability threshold exists with respect to the number of condensate particles. The value of the threshold agrees with the existing experimental data. Moreover with this threshold we prove that a ground state of the condensate exists and is orbital stable. We also evaluate the minimum of the condensate energy.
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    Landscape ecology 15 (2000), S. 187-199 
    ISSN: 1572-9761
    Keywords: BOD5 ; catchment ; empirical model ; land use change ; land use scenarios ; nitrogen ; phosphorus ; runoff ; SO4
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Due largely to unprecedented land-use changes in the Porijõgi River catchment (southern Estonia) losses of nutrients and organic matter have decreased significantly. During the period 1987–1997 abandoned lands increased from 1.7 to 10.5% and arable lands decreased from 41.8 to 23.9%. At the same time, the runoff of total-N, total-P, SO4 and organic matter (after BOD5) decreased from 25.9 to 5.1, 0.32 to 0.13, 78 to 48, and 7.4 to 3.5 kg ha−1 yr−1, respectively. The most significant decreases occurred in agricultural subcatchments while the changes were insignificant in the forested upper course catchment. A simple empirical model which incorporates land-use pattern, fertilization intensity, soil parameters and water discharge accurately described the variations of total-N and total-P runoff in both the whole catchment and its agricultural subcatchments (R 2 varies from 0.95–0.99 for N to 0.49–0.93 for P). In small agricultural subcatchments the rate of fertilization is found the most important factor for nitrogen runoff, whereas in larger mosaic watersheds land use pattern plays the main role. Seven alternative scenarios compiled on the base of the empirical model allow to forecast potential nitrogen and phosphorus losses from the catchment. This information can be used in further landscape and regional planning of the whole region.
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    Development genes and evolution 210 (2000), S. 644-650 
    ISSN: 1432-041X
    Keywords: Keywords Pax protein ; Paired domain ; Homeobox ; Transposase ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Pax proteins play a diverse role in early animal development and contain the characteristic paired domain, consisting of two conserved helix-turn-helix motifs. In many Pax proteins the paired domain is fused to a second DNA binding domain of the paired-like homeobox family. By amino acid sequence alignments, secondary structure prediction, 3D-structure comparison, and phylogenetic reconstruction, we analyzed the relationship between Pax proteins and members of the Tc1 family of transposases, which possibly share a common ancestor with Pax proteins. We suggest that the DNA binding domain of an ancestral transposase (proto-Pax transposase) was fused to a homeodomain shortly after the emergence of metazoans about one billion years ago. Using the transposase sequences as an outgroup we reexamined the early evolution of the Pax proteins. Our novel evolutionary scenario features a single homeobox capturing event and an early duplication of Pax genes before the divergence of porifera, indicating a more diverse role of Pax proteins in primitive animals than previously expected.
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    Development genes and evolution 210 (2000), S. 82-91 
    ISSN: 1432-041X
    Keywords: Key words T-box genes ; Zebrafish ; Fins ; Evolution ; Gene duplication
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The presence of two sets of paired appendages is one of the defining features of jawed vertebrates. We are interested in identifying genetic systems that could have been responsible for the origin of the first set of such appendages, for their subsequent duplication at a different axial level, and/or for the generation of their distinct identities. It has been hypothesized that four genes of the T-box gene family (Tbx2–Tbx5) played important roles in the course of vertebrate limb evolution. To test this idea, we characterized the orthologs of tetrapod limb-expressed T-box genes from a teleost, Danio rerio. Here we report isolation of three of these genes, tbx2, tbx4, and tbx5. We found that their expression patterns are remarkably similar to those of their tetrapod counterparts. In particular, expression of tbx5 and tbx4 is restricted to pectoral and pelvic fin buds, respectively, while tbx2 can be detected at the anterior and posterior margins of the outgrowing fin buds. This, in combination with conserved expression patterns in other tissues, suggests that the last common ancestor of teleosts and tetrapods possessed all four of these limb-expressed T-box genes (Tbx2–Tbx5), and that these genes had already acquired, and have subsequently maintained, their gene-specific functions. Furthermore, this evidence provides molecular support for the notion that teleost pectoral and pelvic fins and tetrapod fore- and hindlimbs, respectively, are homologous structures, as suggested by comparative morphological analyses.
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    Development genes and evolution 210 (2000), S. 329-336 
    ISSN: 1432-041X
    Keywords: Key words Development ; Evolution ; Notch ; Insect
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Studies of somitogenesis in vertebrates have identified a number of genes that are regulated by a periodic oscillator that patterns the pre-somitic mesoderm. One of these genes, hairy, is homologous to a Drosophila segmentation gene that also shows periodic spatial expression. This, and the periodic expression of a zebrafish homologue of hairy during somitogenesis, has suggested that insect segmentation and vertebrate somitogenesis may use similar molecular mechanisms and possibly share a common origin. In chicks and mice expression of the lunatic fringe gene also oscillates in the presomitic mesoderm. Fringe encodes an extracellular protein that regulates Notch signalling. This, and the finding that mutations in Notch or its ligands disrupt somite patterning, suggests that Notch signalling plays an important role in vertebrate somitogenesis. Although Notch signalling is not known to play a role in the formation of segments in Drosophila, we reasoned that it might do so in other insects such as the grasshopper, where segment boundaries form between cells, not between syncytial nuclei as they do in Drosophila. Here we report the cloning of a single fringe gene from the grasshopper Schistocerca. We show that it is not detectably expressed in the forming trunk segments of the embryo until after segment boundaries have formed. We conclude that fringe is not part of the mechanism that makes segments in Schistocerca. Thereafter it is expressed in a pattern which shows that it is a downstream target of the segmentation machinery and suggests that it may play a role in segment morphogenesis. Like its Drosophila counterpart, Schistocerca fringe is also expressed in the eye, in rings in the legs, and during oogenesis, in follicle cells.
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  • 42
    ISSN: 1432-0819
    Keywords: Stratigraphy ; Evolution ; El Chichón ; México
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences
    Notes: 2 abundance and depletion in MgO, CaO, TiO2, as well as trace and rare earth elements. This suggests segregation of olivine and orthopyroxene from the melt. Since human settlements in southeast Mexico and Central America can be traced as far back as approximately 2500 years BP, most of these events probably affected human activity. In fact, there are reports of pottery shards and other artifacts in deposits from the eruption of 1250 BP. Pottery fragments in deposits of an eruption that took place 2500 BP are also reported in this paper. Thus, the impact of the volcano on human activities has been frequent, with most of the repose intervals lasting between 100 to 600 years. The impact of the eruptions was probably of greater than local extent, because airfall tephra could reach distant sites and possibly even affect weather. The eruptive history of El Chichón also offers clues in the investigation of the Maya civilization. Several researchers have considered the volcano as an important factor in the answer to some intriguing questions such as the extensive use of volcanic ash in Late Classic Maya ceramics or, of greater importance, the causes of the collapse of the Classic Maya civilization.
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  • 43
    ISSN: 1432-1211
    Keywords: Key words KIR ; Multigene family ; Gene duplication ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract. Natural killer (NK) immunoglobulin-like receptors (KIRs) are a family of polymorphic receptors which interact with specific motifs on HLA class I molecules and modulate NK cytolytic activity. In this study, we analyzed a recently sequenced subgenomic region on chromosome 19q13.4 containing eight members of the KIR receptor repertoire. Six members are clustered within a 100-kb continuous sequence. These genes include a previously unpublished member of the KIR gene family 2DS6, as well as 2DL1, 2DL4, 3DL1, 2DS4, 3DL2, from centromere to telomere. Two additional KIR genes, KIRCI and 2DL3, which may be located centromeric of this cluster were also analyzed. We show that the KIR genes have undergone repeated gene duplications. Diversification between the genes has occurred postduplication primarily as a result of retroelement indels and gene truncation. Using pre- and postduplication Alu sequences identified within these genes as evolutionary molecular clocks, the evolution and duplication of this gene cluster is estimated to have occurred 30–45 million years ago, during primate evolution. A proposed model of the duplication history of the KIR gene family leading to their present organization is presented.
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    Immunogenetics 51 (2000), S. 69-74 
    ISSN: 1432-1211
    Keywords: Key words MHC class I ; Pseudogene ; Evolution ; Gorilla ; Chimpanzee
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    ISSN: 1432-1211
    Keywords: Key words Immunoglobulin ; Fugu ; VH family ; Teleosts ; Evolution
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    Topics: Biology , Medicine
    Notes: Abstract. The variable region of the immunoglobulin heavy chain is created by a somatic rearrangement of a limited number of germline genes. This mechanism of gene assembly [V(D)J recombination] has been found to take place only in jawed vertebrates (gnathostomes). To understand how this mechanism evolved and diversified it is necessary to study the genomic organization of the heavy-chain gene in different vertebrate lineages. Since there is scant sequence information on the VH locus in fish, shotgun sequencing of a cosmid clone containing part of the VH genomic region of the Japanese pufferfish, Fugu rubripes, was undertaken. Eight full-length VH genes were isolated and characterized. They have higher homology to trout genes, but show the same structural features as VHs found in other vertebrates. Two VH subgroups have been identified whose members are interspersed. The frequency of synonymous and nonsynonymous substitution for VH comparisons between family members was found to be higher in the complementarity-determining regions than in the framework regions. Finally, there are four other genes interspersed with the VH genes, one of which is the first full-length retrotransposon element characterized in vertebrates.
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    ISSN: 1432-1211
    Keywords: Key words J chain ; Polymeric immunoglobulin ; Ontogeny ; Evolution ; Comparative immunology
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine
    Notes: Abstract  The J chain is a component of polymeric immunoglobulin (Ig) molecules and may play an important role in their polymerization and the transport of polymeric Ig across epithelial cells. In this study, the primary structure of the chicken J chain was determined by sequencing cDNA clones. The cDNA had an open reading frame of 476 nucleotides encoding a putative protein of 158 amino acid residues including the signal sequence. The 3′ untranslated region consisted of 1216 nucleotides and a poly(A) tail. The deduced amino acid sequence of the chicken J chain had a high degree of homology to that of human, cow, rabbit, mouse, frog, and earthworm, with eight conserved Cys residues identical to the mammalian J chains. Northern blot hybridization performed with total RNA from various chicken tissues revealed high levels of J-chain mRNA expression in spleen, intestine, Harderian gland, and bursa of Fabricius, and low levels in the thymus. The J chain was expressed in the bursa as early as day 15 of embryogenesis. These data indicated that the chicken J-chain gene displays a high degree of homology with that of other species, and is expressed at an early stage of development of the chicken immune system.
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    Oecologia 123 (2000), S. 330-341 
    ISSN: 1432-1939
    Keywords: Key words  Arabidopsis thaliana ; Carbon dioxide ; Evolution ; Reproduction ; Selection
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Atmospheric CO2 partial pressure (pCO2) was as low as 18 Pa during the Pleistocene and is projected to increase from 36 to 70 Pa CO2 before the end of the 21st century. High pCO2 often increases the growth and reproduction of C3 annuals, whereas low pCO2 decreases growth and may reduce or prevent reproduction. Previous predictions regarding the effects of high and low pCO2 on C3 plants have rarely considered the effects of evolution. Knowledge of the potential for evolution of C3 plants in response to CO2 is important for predicting the degree to which plants may sequester atmospheric CO2 in the future, and for understanding how plants may have functioned in response to low pCO2 during the Pleistocene. Therefore, three studies using Arabidopsis thaliana as a model system for C3 annuals were conducted: (1) a selection experiment to measure responses to selection for high seed number (a major component of fitness) at Pleistocene (20 Pa) and future (70 Pa) pCO2 and to determine changes in development rate and biomass production during selection, (2) a growth experiment to determine if the effects of selection on final biomass were evident prior to reproduction, and (3) a reciprocal transplant experiment to test if pCO2 was a selective agent on Arabidopsis. Arabidopsis showed significant positive responses to selection for high seed number at both 20 and 70 Pa CO2 during the selection process. Furthermore, plants selected at 20 Pa CO2 performed better than plants selected at 70 Pa CO2 under low CO2 conditions, indicating that low CO2 acted as a selective agent on these annuals. However, plants selected at 70 Pa CO2 did not have significantly higher seed production than plants selected at 20 Pa CO2 when grown at high pCO2. Nevertheless, there was some evidence that high CO2 may also be a selective agent because changes in development rate and biomass production during selection occurred in opposite directions at low and high pCO2. Plants selected at high pCO2 showed no change or reductions in biomass relative to control plants due to a decrease in the length of the life cycle, as indicated by earlier initiation of flowering and senescence. In contrast, selection at low CO2 resulted in an average 35% increase in biomass production, due to an increase in the length of the life cycle that resulted in a longer period for biomass accumulation before senescence. From the Arabidopsis model system we conclude that some C3 annuals may have produced greater biomass in response to low pCO2 during the Pleistocene relative to what has been predicted from studies exposing a single generation of C3 plants to low pCO2. Furthermore, C3 annuals may exhibit evolutionary responses to high pCO2 in the future that may result in developmental changes, but these are unlikely to increase biomass production. This series of studies shows that CO2 may potentially act as a selective agent on C3 annuals, producing changes in development rate and carbon accumulation that could not have been predicted from single-generation studies.
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  • 48
    ISSN: 1432-0983
    Keywords: Key words Arbuscular mycorrhizas ; Evolution ; Glomus mosseae ; Plasma membrane H+-ATPase genes
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  To identify genes that encode plasma membrane H+-ATPases in the arbuscular mycorrhizal fungus Glomus mosseae two sets of degenerate primers matching highly conserved motifs present in all plant and fungal ATPases were designed. Nested PCR-amplification of G. mosseae genomic DNA using the designed degenerate primers was carried out. Sequence analysis of the cloned PCR products identified five different clones (GmHA1, GmHA2, GmHA3, GmHA4 and GmHA5) encoding putative plasma membrane H+-ATPases. Comparison of the deduced amino-acid sequences of GmHA1–GmHA5 indicate that GmHA1, GmHA3 and GmHA4 are highly identical, while GmHA2 and GmHA5 are more divergent. The evolutionary and functional significance of the divergence found among the different members of the H+-ATPase gene family in G. mosseae is discussed.
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    Journal of population economics 13 (2000), S. 403-424 
    ISSN: 1432-1475
    Keywords: JEL classification: O41 ; F22 ; Key words: Altruism ; education ; growth ; convergence ; capital mobility
    Source: Springer Online Journal Archives 1860-2000
    Topics: Sociology , Economics
    Notes: Abstract. The aim of this paper is to discuss the process of regional convergence within the framework of an overlapping generations model in which the engine of growth is the accumulation of human capital. In particular, we consider different education funding systems and compare their performance in terms of growth rates and pace of convergence between two heterogeneous regions. The analysis suggests that the choice of a particular education system incorporates a possible trade-off between long run growth rate and short run convergence. In such choice, the initial capital stock and the extent of regional human capital discrepancy appear as central variables.
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    ISSN: 1432-2242
    Keywords: Key words Cicer species ; Microsatellites ; Zero-allele ; Phylogenetic tree ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The conservation of 90 microsatellite-flanking sequences from chickpea in 39 accessions of eight annual and 1 accession of a perennial species of the genus Cicer was investigated. All of the primer sequences successfully amplified microsatellites in related species, indicating the conservation of microsatellite-flanking sequences in chickpea’s relatives. However, the degree of conservation of the primer sites varied between species depending on their known phylogenetic relationship to chickpea, ranging from 92.2% in C. reticulatum, chickpea’s closest relative and potential ancestor, down to 50% for C. cuneatum. A phylogenetic tree revealed that chickpea and the other members of its crossability group were more closely related to the perennial C. anatolicum than to other annual species of the genus. Considerable variation in size and number of amplification products between and within species was observed. Sequence analysis of highly divergent amplification products proved that variation is either due to large differences in the number of microsatellite repeats or to the amplification of a locus unrelated to the one amplified from chickpea. Sequence information and bootstrapping using PAUP suggested that STMSs derived from chickpea may be efficiently and reliably used for synteny studies in chickpea’s crossability group, including C. anatolicum. However, care should be taken when applying these markers to other species of the genus. Considering the data presented here and the known historical record, the age of section Monocicer, including chickpea, is estimated to be about 100,000 years.
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    Theoretical and applied genetics 100 (2000), S. 1267-1273 
    ISSN: 1432-2242
    Keywords: Keywords Domestication ; Evolution ; QTL ; Map-based cloning ; Lycopersicon esculentum
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The seeds of domesticated plants are normally much larger than those of their wild counterparts. This change in seed weight was most likely in response to the selection pressure for yield, uniform germination and seedling vigor which was exerted by humans during domestication. However, despite the evolutionary and agronomic significance of seed weight, very little is know about the genetic and developmental controls of this trait; and, thus far, none of the genes in this pathway have been isolated from any plant species. QTL mapping experiments conducted in tomato during the past decade have allowed the identification of many seed-weight QTLs and have also revealed that only a few loci are responsible for the majority of the seed-weight changes that accompanied the domestication of tomato. This review presents a consensus map for seed weight QTL identified in previously published reports and in unpublished results from our laboratory. This summary of seed-weight QTL data allows for the identification of the major loci controlling this trait in the genus Lycopersicon. It is hoped that this work will allow the elucidation of this important phenotypic transition that occurred during crop-plant domestication and will also provide the starting point for the cloning of a gene responsible for seed-weight variation.
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    Theoretical and applied genetics 101 (2000), S. 379-387 
    ISSN: 1432-2242
    Keywords: Key words Rice ; Isozyme variation ; Multilocus organization ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Genetic organization of isozyme variation in rice (Oryza sativa L.) was investigated based on 17 polymorphic isozyme loci using a sample of 511 accessions of worldwide origin. The genetic diversity within the species was very high (H=0.36 with 4.82 alleles per locus), as compared with most selfing plant species. Three diversity centers were detected for isozyme variation including South Asia, China and Southeast Asia. The accessions were classified into three well-differentiated cultivar groups corresponding to the indica and japonica subspecies, and a new unnamed group. Variation within the cultivar groups accounted for 80% of the total isozyme variation. Within-country variation accounted for 58% of the total variation while among-region and among-country variation within the cultivar groups accounted for only 14% and 8% of the total variation. Analyses using log-linear models revealed that pronounced non-random associations between and among alleles at many unlinked isozyme loci were organized in a non-hierarchical pattern, and subspecific and macro-geographic differentiation was much more pronounced in multilocus phenotype frequencies than in allelic frequencies at individual loci. These results suggest that selection on multilocus gene complexes was largely responsible for the maintenance of the extensive isozyme variation within the species and the indica-japonica differentiation. Our results further suggest the independent domestication of indica and japonica, the dual origins of the indica rice from China and South Asia (India), and the differentiation of the ecotypes ’javanica’ and the ’temperate japonica’ within the japonica subspecies.
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  • 53
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    Theoretical and applied genetics 101 (2000), S. 1259-1268 
    ISSN: 1432-2242
    Keywords: Key words Enriched-library ; SSR ; Repetitive elements ; Allelic diversity ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  Microsatellites have many desirable marker properties. There has been no report of the development and utilization of microsatellite markers in oat. The objectives of the present study were to construct oat microsatellite-enriched libraries, to isolate microsatellite sequences and evaluate their level of polymorphism in Avena species and oat cultivars. One hundred clones were isolated and sequenced from three oat microsatellite-libraries enriched for either (AC/TG) n , (AG/TC) n or (AAG/TTC) n repeats. Seventy eight clones contained microsatellites. A database search showed that 42% of the microsatellite flanking sequences shared significant homology with various repetitive elements. Alu and retrotransposon sequences were the two largest groups associated with the microsatellites. Forty four primer sets were used to amplify the DNA from 12 Avena species and 20 Avena sativa cultivars. Sixty two percent of the primers revealed polymorphism among the Avena species, but only 36% among the cultivars. In the cultivars, the microsatellites associated with repetitive elements were less polymorphic than those not associated with repetitive elements. Only 25% of the microsatellites associated with repetitive elements were polymorphic, while 46% of the microsatellites not associated with repetitive elements showed polymorphism in the cultivars. An average of four alleles with a polymorphism information content (PIC) of 0.57 per primer set was detected among the Avena species, and 3.8 alleles with a PIC of 0.55 among the cultivars. In addition, 54 barley microsatellite primers were tested in Avena species and 26% of the primers amplified microsatellites from oat. Using microsatellite polymorphisms, dendrograms were constructed showing phylogenetic relationships among Avena species and genetic relationships among oat cultivars.
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    Ecological research 15 (2000), S. 101-106 
    ISSN: 1440-1703
    Keywords: comparative ecology ; growth ; marine fish ; patterns ; reproduction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: A number of strong regularities characterize certain very basic biological parameters in marine fishes. For example, the ovulated eggs of fish usually measure approximately 1 mm in diameter. The small, relatively uniform size of the eggs means that almost all fish larvae experience environmental variability at very similar scales, which itself establishes strong constraints for, and links between reproduction and recruitment. Additional constraints emerge from seawater being a poor medium for respiration, which establishes further linkages between growth and mortality. These constraints have produced strongly convergent features, and thence the patterns in reproduction and growth of marine fishes that are presented.
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    Plasma chemistry and plasma processing 20 (2000), S. 87-110 
    ISSN: 1572-8986
    Keywords: striations ; nitrogen ; spherical discharge ; spatially inhomogeneous Boltzmann equation ; electron velocity distribution function ; dc glow discharge
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Technology
    Notes: Abstract Recent observations of spherical striations in large-volume nitrogen dcdischarges with a central anode have stimulated investigations of thenonlocal electron kinetics in these striations by solving the spatiallyinhomogeneous Boltzmann equation adapted to spherical geometry. Becausethe radial course of the electric potential is largely unknown in thisdischarge, different models concerning its radial course have been developedand used. These models are based on the measured radii of the striationsand the assumption that the potential drop between successive striationsdoes not change. As a consequence, with decreasing distance between thestriations the electric field strongly increases toward the centralanode. It has been found that spherical striations are only obtained ifthe electric field is strongly modulated. In this case, a highly nonlocalbehavior of the velocity distribution function and strongly modulatedradial courses of the macroscopic quantities have been obtained.
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  • 56
    ISSN: 1573-143X
    Keywords: body composition ; catfish (Mystus nemurus) ; feeding rate ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract A 10 week experiment was conducted to determine theeffects of feeding rate on growth, feed utilizationand body composition of the tropical bagrid catfish,Mystus nemurus. Catfish fingerlings with anaverage initial body weight of 12 g were fed apractical diet (36.2% protein, 16.5 kJ/g diet) atrates of 1, 2, 2.5, 3, 3.5, 4 or 5% of their bodyweight (BW) per day in two equal meals. Watertemperature was approximately 29 °C throughoutthe experiment. Percent weight gain increased almostlinearly with increasing feeding rates up to 2.5%BW/day beyond which no significant (P 〉 0.05)improvement in weight gain was observed. The specificgrowth rate of catfish fed rations of 1% BW/day was0.72%/day and this increased significantly to anaverage of 1.39%/day for catfish fed 2.5% BW/day andbeyond. Feed utilization did not differ significantly(P 〉 0.05) between fish fed 1.0 to 2.5%BW/day but decreased when rations were increased to3.0% BW/day and above. Feed efficiency ratio was0.79 for catfish fed 1.0% BW/day compared to a ratioof 0.27 for fish fed at 5% BW/day. Catfish fed 1.0%BW/day had the lowest condition factor, hepato- andviscerosomatic indices, but the highest carcass tobody weight ratio. These fish also had lowerproportions of whole body dry matter, lipid andprotein, carcass dry matter and lipid, and visceraldry matter and lipid than fish in other groups. Therewere no significant differences in either conditionindices or relative body composition of fish fedrations of 2.0 to 5.0% BW/day. Based on the growth,feed efficiency and body composition data obtained, afeeding rate of 2.5% BW per day is recommended forM. nemurus fingerlings raised at 29 °C.
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    Aquaculture international 8 (2000), S. 531-542 
    ISSN: 1573-143X
    Keywords: feed intake ; growth ; protein utilisation ; proximate ; composition ; rainbow trout (Oncorhynchus mykiss)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Rainbow trout Oncorhynchus mykiss grew from 44 to 326 g in 96days when held at ∼12 °C. Fish were fed to satiation twice dailywith either high (L1: 30.8%, L2:31.4%) or lower-lipid feeds (C1: 18.8%,C2: 21.8%). Four feeding treatments were studied.Group C1C2 received feed C1 for 43 days(days 0–43) and C2 thereafter (days 44–96).Groups L1L2, L1C2 andC1L2 were subjected to dietary changes asindicated by the feed designations. After a short period of feedadaptation, fish ingested similar amounts of feed energy i.e., they ateless by weight of the lipid-rich (L) feeds. Feed lipid content did notaffect growth but fish fed L-feed had reduced feed conversion ratio(FCR) compared to fish fed C-feed (0.731 vs. 0.773) during days0–43 (P 〈 0.01). After 96 days,L1L2-fish were lower in body protein(15.8%) than the C1C2-fish (16.8%)(P 〈 0.01). L-feeds also tended to increase percentage lipidand reduce percentage whole body moisture and ash. A higher net proteinutilisation (NPU) was recorded in fish fed L-feeds (43.6%)compared to fish fed C-feeds (38.8%) in days 0–43(P 〈 0.05). This seemed to be the result of a lower proteinintake rather than a protein-sparing effect of feed lipid. Above athreshold value of approximately 6.5 mg protein eaten·g bodywtminus 1·day−1, NPU decreased.
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  • 58
    ISSN: 1573-143X
    Keywords: aggression ; Atlantic salmon (Salmo salar) ; dominance ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Aggression in groups of 0+ Atlantic salmon (Salmo salar) was monitoredat weekly intervals in two tanks containing 100 fish each. Three 1 + salmonparr were added to one of these. After 5 weeks, fish weights were measuredin both tanks and the conditions reversed. At ten weeks, weights of fish inboth tanks were measured again. In both populations, levels of aggressionamong the smaller fish were significantly lower and growth ratessignificantly higher when the large fish were present. Although the largefish attacked the small ones, the rate at which they did so was an order ofmagnitude lower that the rate at which small fish attacked each other in theabsence of larger conspecifics. This raises the possibility that levels ofaggression among farmed salmon might be reduced by the addition of a fewlarge conspecifics.
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    Acta applicandae mathematicae 62 (2000), S. 23-130 
    ISSN: 1572-9036
    Keywords: stability ; functional equations ; Cauchy difference ; semigroup ; inequalities ; approximate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we study the stability of functional equations that has its origins with S. M. Ulam, who posed the fundamental problem 60 years ago and with D. H. Hyers, who gave the first significant partial solution in 1941. In particular, during the last two decades, the notion of stability of functional equations has evolved into an area of continuing research from both pure and applied viewpoints. Both classical results and current research are presented in a unified and self-contained fashion. In addition, related problems are investigated. Some of the applications deal with nonlinear equations in Banach spaces and complementarity theory.
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    Journal of chemical ecology 26 (2000), S. 1749-1763 
    ISSN: 1573-1561
    Keywords: Conversion factor ; free amino acids ; fruits ; Kjeldahl ; nitrogen ; nutrition ; protein ; pulp ; secondary metabolites
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Protein content of plant tissues is usually estimated by multiplying total nitrogen by a conversion factor of 6.25. This technique assumes that all nitrogen originates from protein. When applied to fruit pulp, it overestimates protein content because pulp typically contains free amino acids and many nitrogenous secondary metabolites. At issue is the extent of error and, consequently, what the conversion factor between nitrogen and protein should be. We calculated a conversion factor based on pulp samples from 18 species collected in the southeastern United States. We also report a new and simple method of estimating protein and free amino acids in fruit pulp. Because previous studies have found high variation in protein and secondary metabolite content among fruit species, use of a single conversion factor for all species will generate error. In an attempt to reduce such error, we calculated protein contents and conversion factors separately for two common fruit types: lipid-rich/carbohydrate-poor and lipid-poor/carbohydrate-rich. We found no difference between these types of fruit and hence combined results in calculating an average conversion factor of 5.64. Use of an accurate conversion factor is important in estimating protein consumption by wild animals and in formulating diets of captive animals. It can also reveal whether loss of body mass in captive animals on fruit diets is due to insufficient protein consumption, secondary metabolite toxicity, or an imbalance of amino acids.
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  • 61
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    Journal of chemical ecology 26 (2000), S. 2015-2023 
    ISSN: 1573-1561
    Keywords: Allelopathy ; growth ; phenolics ; Hebeloma ; Hymenoscyphus ; Picea abies ; Vaccinium myrtillus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract Allelopathy due to humus phenolics is a cause of natural regeneration deficiency in subalpine Norway spruce (Picea abies) forests. If inhibition of spruce germination and seedling growth due to allelochemicals is generally accepted, in contrast there is a lack of knowledge about phenolic effects on mycorrhizal fungi. Thus, this work tested effects of a humic solution and its naturally occurring phenolics on the growth and respiration of two mycorrhizal fungi: Hymenoscyphus ericae (symbiont of Vaccinium myrtillus, the main allelochemical-producing plant) and Hebeloma crustuliniforme (symbiont of P. abies, the target plant). Growth and respiration of H. crustuliniforme were inhibited by growth medium with the original humic solution (−6% and −30%), respectively, whereas the same humic solution did not affect growth but decreased respiration of H. ericae (−55%). When naturally occurring phenolics (same chemicals and concentrations in the original humic solution) were added to the growth medium, growth of H. crustuliniforme was not affected, whereas that of H. ericae significantly increased (+10%). We conclude that H. ericae is better adapted to the allelopathic constraints of this forest soil than H. crustuliniforme and that the dominance of V. myrtillus among understory species could be explained in this way.
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    International journal of fracture 105 (2000), S. 57-79 
    ISSN: 1573-2673
    Keywords: Interface toughness ; interface debonding ; stability ; adhesive interface ; bimaterial.
    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, we studied the interface debonding when a crack perpendicularly approaches an interface between two dissimilar elastic materials. An interface toughness law was first defined according to an adhesive model governing the interface fracture. By analysing the interaction between the normally approaching crack and the interface crack and by tacking account of the adhesive forces at ends of the interfacial crack, a model for studying the interface debonding and the debonding stability was established. It is observed that the interface debonding toughness depends strongly on the mixed mode locally produced over the plastic adhesive zone of the interface. Moreover, the interface debonding may be unstable, i.e. the interface debonding length may jump from an initial value to a certain final value under critical remote loading. This jump may be surprisedly important in certain cases. These results agree with the experimental works gathered so far and can be used to explain the mechanism of 'crack arrestor' formed by an interface.
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  • 63
    ISSN: 1573-4943
    Keywords: Methanol dehydrogenase ; Ca2+ ; binding ; activity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of exogenously added Ca2+ on the enzymatic activity and structural stability of methanol dehydrogenase were studied for various Ca2+ concentrations. Methanol dehydrogenase activity increased significantly with increasing concentration of Ca2+, approaching saturation at 200 mM Ca2+. The effect of Ca2+ on the activation of MDH was time dependent and Ca2+ specific and was due to binding of the metal ions to the enzyme. Addition of increasing concentration of Ca2+ caused a decrease of the intrinsic tryptophan fluorescence intensity in a concentration-dependent manner to a minimum at 200 mM, but with no change in the fluorescence emission maximum wavelength or the CD spectra. The results revealed that the activation of methanol dehydrogenase by Ca2+ occurred concurrently with the conformational change. In addition, exogenously bound Ca2+ destabilized MDH. The potential biological significance of these results is discussed.
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  • 64
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    Behavioral ecology and sociobiology 49 (2000), S. 48-56 
    ISSN: 1432-0762
    Keywords: Keywords Antipredator behavior ; Phylogenetic inertia ; Conflicting selection pressures ; Evolution ; Salamanders
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract  The streamside salamander, Ambystoma barbouri, exhibits ineffective antipredator behavior (high emergence rate from refuge, and high activity while out of refuge) and thus suffers heavy predation in stream pools with sunfish. A. barbouri evolved relatively recently from an ancestor that closely resembled a sister species, A. texanum, which breeds in fishless, ephemeral ponds. Sunfish thus represent a relatively new selection pressure for A. barbouri. Phylogenetic inertia predicts that (1) A. texanum should be very poor at coping with fish and (2) because it has only recently been exposed to fish, A. barbouri should still be poor at avoiding fish, but due to its recent exposure to fish, A. barbouri should be better than A. texanum at coping with sunfish. Experimental results provided mixed support for these predictions. As predicted, A. texanum suffered heavy sunfish predation. Compared to A. texanum, A. barbouri showed a greater tendency to initiate alarm moves that enhanced escape success from fish. However, in both the presence and absence of fish, A. barbouri showed higher emergence rates from refuge and higher movement while out of refuge than A. texanum. These behaviors tend to increase exposure to sunfish, i.e., for these key behaviors, A. barbouri apparently evolved in the wrong direction as far as fish predation is concerned. Due to these offsetting effects (increased exposure to fish, increased escape success), A. barbouri is no better at surviving with sunfish than A. texanum. A possible explanation for the high activity of A. barbouri is its use of highly ephemeral habitats (relative to A. texanum) that favor the evolution of higher activity, feeding, and developmental rates for A. barbouri relative to A. texanum.
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  • 65
    ISSN: 1617-4623
    Keywords: Key wordsDrosophila melanogaster ; Ceratitis capitata ; Tephritids ; Evolution ; Dacus
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The alcohol dehydrogenase genes make up one of the best studied gene families in Drosophila, both in terms of expression and evolution. Moreover, alcohol dehydrogenase genes constitute potential versatile markers in insect transformation experiments. However, due to their rapid evolution, these genes cannot be cloned from other insect genera by DNA hybridization or PCR-based strategies. We have therefore explored an alternative strategy: cloning by functional complementation of appropriate yeast mutants. Here we report that two alcohol dehydrogenase genes from the medfly Ceratitis capitata can functionally replace the yeast enzymes, even though the medfly and yeast genes have evolved independently, acquiring their enzymatic function convergently. Using this method, we have cloned an alcohol dehydrogenase gene from the olive pest Bactrocera oleae. We conclude that functional complementation in yeast can be used to clone alcohol dehydrogenase genes that are unrelated in sequence to those of yeast, thus providing a powerful tool for isolation of dominant insect transformation marker genes.
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  • 66
    ISSN: 1617-4623
    Keywords: Key wordsDictyostelium discoideum ; Mitochondrial DNA ; Genome sequencing ; Genetic map ; Evolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract We present an overview of the gene content and organization of the mitochondrial genome of Dictyostelium discoideum. The mitochondria genome consists of 55,564 bp with an A + T content of 72.6%. The identified genes include those for two ribosomal RNAs (rnl and rns), 18 tRNAs, ten subunits of the NADH dehydrogenase complex (nad1, 2, 3, 4, 4L, 5, 6, 7, 9 and 11), apocytochrome b (cytb), three subunits of the cytochrome oxidase (cox1/2 and 3), four subunits of the ATP synthase complex (atp1, 6, 8 and 9), 15 ribosomal proteins, and five other ORFs, excluding intronic ORFs. Notable features of D. discoideum mtDNA include the following. (1) All genes are encoded on the same strand of the DNA and a universal genetic code is used. (2) The cox1 gene has no termination codon and is fused to the downstream cox2 gene. The 13 genes for ribosomal proteins and four ORF genes form a cluster 15.4 kb long with several gene overlaps. (3) The number of tRNAs encoded in the genome is not sufficient to support the synthesis of mitochondrial protein. (4) In total, five group I introns reside in rnl and cox1/2, and three of those in cox1/2 contain four free-standing ORFs. We compare the genome to other sequenced mitochondrial genomes, particularly that of Acanthamoeba castellanii.
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    Artificial life and robotics 4 (2000), S. 109-118 
    ISSN: 1614-7456
    Keywords: Parallel and distributed processing ; Space navigation ; Evolution ; WAVE model ; Cooperative behavior ; Mobile robots
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract This paper modifies the WAVE model for parallel processing in virtual networks to explore and process continuous physical worlds. Expressing distributed activity by cooperative jobs spreading in space and “seeing” each other, rather than as vehicles exchanging messages, the model allows complex missions to be planned in a very flexible manner, with mobile hardware being assigned to the evolving space-conquering programs (waves) dynamically, when required or available. A number of cooperative scenarios in a physical world demonstrate the simplicity and compactness of the wave code. The execution of waves by mobile hardware is discussed, including run-time mapping of waves to vehicles, and supporting multiple distributed jobs in cases of hardware shortages. WAVE can be used efficiently for solving complex problems in space by organized groups of cheap specialized mobile robots, where intelligent behavior is provided by very high level of system organization rather than by the smartness of individual units. In a broader sense, it may also serve as a basic technology for parallel and distributed simulation, and the management of evolution and self-organization of large open systems of different natures.
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    Acta mechanica Sinica 16 (2000), S. 264-272 
    ISSN: 1614-3116
    Keywords: nonlinear dynamics ; bifurcation ; stability ; fluid-solid interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper studies interactions of pipe and fluid and deals with bifurcations of a cantilevered pipe conveying a steady fluid, clamped at one end and having a nozzle subjected to nonlinear constraints at the free end. Either the nozzle parameter or the flow velocity is taken as a variable parameter. The discrete equations of the system are obtained by the Ritz-Galerkin method. The static stability is studied by the Routh criteria. The method of averaging is employed to examine the analytical results and the chaotic motions. Three critical values are given. The first one makes the system lose the static stability by pitchfork bifurcation. The second one makes the system lose the dynamical stability by Hopf bifurcation. The third one makes the periodic motions of the system lose the stability by doubling-period bifurcation.
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  • 69
    ISSN: 1608-3237
    Keywords: poly-β-hydroxybutyric acid ; Yersinia pseudotuberculosis ; Listeria monocytogenes ; temperature ; growth
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A comparative investigation of the intracellular content of poly-β-hydroxybutyric acid showed that Yersinia pseudotuberculosis strains accumulated, on the average, lower amounts of this reserve substance than Listeria monocytogenes strains. The intracellular pool of poly-β-hydroxybutyric acid was responsible for the growth of the bacteria at low temperatures (4–6°C) in the absence of any exogenous carbon and energy source.
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  • 70
    ISSN: 1608-3407
    Keywords: Scenedesmus quadricauda ; growth ; cell size ; photosynthetic activity ; imazalil sulfate ; three-phase dose response
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Three-phase dose responses of biological systems of different levels of organization are often called “paradoxical” because the biological effects are clearly manifested under low- and high-intensity treatments, but are absent during moderate-strength treatments. In this work, we found anomalous changes in the cell number of a green alga Scenedesmus quadricauda (Turp.) Breb. grown in the presence of the fungicide imazalil sulfate. At low imazalil concentrations (2.5 × 10–9–2.5 × 10–6 M), the slow increase in the cell number as compared to an untreated culture was not related to cell death. As seen by the dynamics of the population structure and cell functional characteristics (photosynthesis, thermal stability of photosynthetic membranes, etc.), the decrease in the growth rate at low concentrations of imazalil (2–10 × 10–9 M) was due to a long-term arrest of cell division in a fraction of the cell population rather than to a decrease in the rate of division. The absence of a toxic effect or even a slight stimulation of culture growth at moderate concentrations (0.05–1.25 × 10–6 M) was due to the resumption of cell division after a temporal cessation. At these concentrations, imazalil induced cell stress and adaptive elevation of cell tolerance to the fungicide (acclimation). Cell death was observed only at a high fungicide content in the medium (6.25 × 10–6 and higher). Thus, the three-phase (bimodal) dose response corresponds to two regimes (steady-states) of cell functioning which differ in cell sensitivity to external stimuli. The low-sensitivity state, which is characteristic of cells that have experienced stress, is likely to be the state known as “hormesis.”
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  • 71
    ISSN: 1573-5125
    Keywords: discharge effects on lotic invertebrates ; disturbance ; persistence ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Temporal and spatial trends were examined in benthic macroinvertebrate and physical-chemical data collected for at least ten years at ten sites along the plains reach of the Cache la Poudre River, Colorado, USA. A distinct longitudinal environment gradient was found as many of the water chemistry parameter levels changed downstream from the reference site. Seasonal Kendall analyses on individual sites indicated that several chemical parameters, including conductivity, un-ionized NH3-N and NO2-N have increased since the beginning of the study within most sites. Levels of some parameters (e.g., dissolved oxygen, un-ionized NH3-N) violated aquatic life standards a few times during the study. Over 175 taxa of macroinvertebrates (primarily insects) were collected in the study reach from 1981–1996. Results from detrended correspondence analyses (DCA) on macroinvertebrate data indicated that this stretch of the river exhibited little longitudinal change beyond the two farthest upstream sites. There was a decline in macroinvertebrate density and total number of taxa within most individual sites during 1983–1984, corresponding with the highest recorded discharge in 75 years (1983) and a prolonged, heavy spring runoff in 1984. Taxa richness and density recovered to pre-1983 levels within a few months to a year following the high flows at most sites. These findings suggested that the macroinvertebrate assemblages had low resistance to disturbance, but high resilience. However, the results from DCAs and Kendall's Coefficient of Concordance (W) on individual sites for the entire study period suggested a similar macroinvertebrate community structure through time. It would appear that the composition and abundance of the lotic macroinvertebrate assemblages in the Poudre River has remained relatively constant over the long-term. This has occurred even with some potentially negative changes in water chemistry and increased urban development.
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  • 72
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    Journal of applied phycology 12 (2000), S. 185-189 
    ISSN: 1573-5176
    Keywords: blue-green alga ; cyanobacterium ; carbon dioxide ; culture ; growth ; Nostocflagelliforme ; rehydration, watering
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The terrestrial blue-green alga (cyanobacterium), Nostoc flagelliforme, was cultured in air at variouslevels of CO2, light and watering to see theireffects on its growth. The alga showed the highestrelative growth rate at the conditions of highCO2 (1500 ppm), high light regime (219–414μmol m-2s-1) and twice daily watering,but the lowest rate at the conditions of low light(58–114 μmol m-2s-1) and daily twicewatering. Increased watering had little effect ongrowth rate at 350 ppm CO2, but increased byabout 70% at 1500ppm CO2 under high lightconditions. It was concluded that enriched CO2could enhance the growth of N. flagelliformewhen sufficient light and water was supplied.
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  • 73
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    Journal of applied phycology 12 (2000), S. 331-339 
    ISSN: 1573-5176
    Keywords: algal biomass ; algal uptake ; ammonia stripping ; biological nutrient removal ; high rate algal ponds ; nitrogen ; nutrients ; nitrification ; urban wastewater treatment ; waste stabilisation ponds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Two experimental high rate algal ponds (HRAPs) (1.5m2, 570 L per unit), each with a secondaryclarifier for algal biomass separation (0.025 m2,without recirculation), were fed with urban wastewaterfor a one-year period (June 1993 to July 1994). TheHRAPs were installed on the roof of the Department ofHydraulic, Coastal and Environmental Engineering ofthe Technical University of Catalonia, Barcelona,Spain (lat. 41° 24′ 42″ N; long. 2° 7′42″ E). Nitrogen removal efficiency and changes intotal nitrogen, total organic nitrogen,NH4 +-N, and oxidized nitrogen underdifferent hydraulic retention times (HRTs) werecompared. HRAP A was always operated at a higherHRT than HRAP B. Both HRAPs were subjected to thesame environmental conditions of solar radiation, airtemperature and influent water quality. Grab samplesof influent, effluent of the HRAP (mixed liquor) andfinal effluent from the clarifiers were taken once aweek. The annual average nitrogen removal was 73% forHRAP A, and 57% for HRAP B. Higher removal in HRAP Awas due to a lower inorganic nitrogen concentration inits effluent. Significant differences (p〉 0.05) inthe relative proportions of nitrogen forms between thetwo HRAPs were observed only in autumn and winter.This was mainly because HRAP B did not achieve a highlevel of NH4 +-N removal by stripping andalgal uptake, as observed in HRAP A. NH4 +-Nstripping was the most important mechanism fornitrogen removal (mean efficiency of 47% and 32% inHRAP A and B, respectively) followed by algal uptake,and subsequent algal separation in the clarifiers(mean efficiency of 26% and 25% in HRAP A and Brespectively). The conclusion of this study is thatHRT determines both the nitrogen removal efficiencyand the distribution of nitrogen forms in the effluentof a HRAP. The nitrogen removal level can becontrolled through suitable HRT operating strategies.By operating at a HRT of 4 days in spring and summer,and 10 days in autumn and winter, nitrogenconcentration in the effluent of a HRAP system can bereduced to less than 15 mg L-1 N.
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  • 74
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    Journal of mathematical chemistry 28 (2000), S. 325-340 
    ISSN: 1572-8897
    Keywords: numerical method ; stability ; Hopf bifurcation ; coupled oscillator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract A second-order accurate numerical method has been proposed for the solution of a coupled non-linear oscillator featuring in chemical kinetics. Although implicit by construction, the method enables the solution of the model initial-value problem (IVP) to be computed explicitly. The second-order method is constructed by taking a linear combination of first-order methods. The stability analysis of the system suggests the existence of a Hopf bifurcation, which is confirmed by the numerical method. Both the critical point of the continuous system and the fixed point of the numerical method will be seen to have the same stability properties. The second-order method is more competitive in terms of numerical stability than some well-known standard methods (such as the Runge–Kutta methods of order two and four).
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  • 75
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    Aquatic ecology 34 (2000), S. 19-27 
    ISSN: 1573-5125
    Keywords: adaptation ; fitness ; food quality ; growth ; reproduction ; temporary ponds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Temporary pond Daphnia flourish on relatively poor-quality food, suggesting adaptation to stringent temporary pond conditions. We conducted laboratory life history experiments on populations of Daphnia obtusa from a shaded woodland temporary pond (short hydroperiod, dystrophic) and an open farmland temporary pond (long hydroperiod, eutrophic), and compared a suite of physical/chemical conditions in the ponds to evaluate habitat conditions. We hypothesized that the shaded woodland pond population would be more fit in terms of life history variables for individuals (age and size at first reproduction, mean brood size, mean number of neonates) and populations (generation time, net reproductive rate R 0, and intrinsic reproductive rate r) given a standard, low-quality food (trout chow and yeast). Life history traits of woodland pond animals were mixed, relative to farm pond animals, and consistent with bet-hedging for an unpredictable habitat. Values of life history traits rivaled or exceeded those of other studies using phytoplankton as food, and were influenced by the pond water used for our study. Life histories clearly differ among local and regional temporary pond Daphnia obtusa populations, and should be valuable for examining the relative influences of local selection and metapopulation dynamics on population structure.
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  • 76
    ISSN: 1573-5176
    Keywords: desiccation ; growth ; growth model ; inorganic carbon ; nutrients ; photoperiod ; photosynthesis ; pigments ; Porphyra linearis ; PPF ; respiration ; temperature ; water velocity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The effect of environmental parameters on the growthof Porphyra linearis gametophytes was examinedunder controlled conditions, and related to themultilinear regression growth model recently developedfor this seaweed under coastal conditions in theeastern Mediterranean. Growth chambers, a gradienttable, special culture devices and analytical methodswere combined for this culture study.The major factors significantly controlling thegrowth rate of the P. linearis gametophytein glass dishes were: photoperiod, temperature, agein culture, photosynthetic photon flux (PPF), salinityand water dynamics. Maximal growth occurred underdaylength of 12 h, medium temperature (15–20 °C), low PPF (70–140 μmol photon m-2s-1), ambient salinity (30–40 ppt), 1–3 h ofdaily air exposure, and water velocity of 4 cm s-1.Photosynthesis and respiration rates weredominantly affected by daylength and temperature,while the concentration of pigments was dominantlyaffected by PPF and temperature.These conditions correspond well to the optimalnatural growth environment of this local species andare in agreement with the optimum estimated throughthe recently developed outdoor mathematical growthmodel.
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  • 77
    ISSN: 1573-5125
    Keywords: crayfish ; Procambarus alleni ; growth ; Florida Everglades ; hydroperiod
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Environmental conditions influence crustacean growth by affecting molt intervals and incremental increases in length and weight. In the seasonally-flooded marl prairie wetlands of eastern Everglades National Park, U.S.A., hydropattern exerts considerable influence on aquatic primary productivity, and so may influence the availability of food resources for higher trophic levels. The seasonal hydroperiod has been drastically altered by anthropogenic factors, but the impacts on the aquatic community are not well known. We studied whether differences in growth of crayfish Procambarus alleni could be detected in habitats with different hydroperiods. We first described growth patterns based on incremental increases in length and weight of crayfish on a high protein diet in the laboratory. Regression analyses indicated that growth patterns in males and females were similar. Although the intermolt period increased with age, the proportional increases in length and weight were similar through successive molts. The relationship between length and weight of crayfish was best described by a power equation for allometric growth. We then compared growth curves for crayfish subpopulations from different areas of the marl prairie. In habitats with the longest hydroperiods, crayfish weight-at-size was not significantly different from that in laboratory crayfish on the high protein diet. However, weight gain per unit increase in length in short hydroperiod sites was significantly less than in long hydroperiod sites or in the laboratory. These results indicate that crayfish productivity may be associated with hydroperiod in these stressed wetlands, and this may contribute to observed source-sink population regulation.
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  • 78
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    Chemistry of heterocyclic compounds 36 (2000), S. 115-133 
    ISSN: 1573-8353
    Keywords: thiophthalylium salts ; methods of preparation ; structure ; stability ; reactivity ; electrophilic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methods of preparation, chemical reactions, the structures and reactivity of thiophthalylium ions are reviewed.
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  • 79
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    Journal of scientific computing 15 (2000), S. 441-456 
    ISSN: 1573-7691
    Keywords: modified conjugate gradient method ; conjugate gradient method ; Krylov space ; convergence rate ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the modified conjugate gradient procedure for solving A $$\underline x $$ = $$\underline b $$ in which the approximation space is based upon the Krylov space associated with A 1/p and $$\underline b $$ , for any integer p. For the square-root MCG (p=2) we establish a sharpened bound for the error at each iteration via Chebyshev polynomials in $$\sqrt A$$ . We discuss the implications of the quickly accumulating effect of an error in $$\sqrt A$$ $$\underline b $$ in the initial stage, and find an error bound even in the presence of such accumulating errors. Although this accumulation of errors may limit the usefulness of this method when $$\sqrt A$$ $$\underline b $$ is unknown, it may still be successfully applied to a variety of small, “almost-SPD” problems, and can be used to jump-start the conjugate gradient method. Finally, we verify these theoretical results with numerical tests.
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  • 80
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    Neural processing letters 12 (2000), S. 129-144 
    ISSN: 1573-773X
    Keywords: associative memory ; dynamical systems ; Glauber dynamics ; Hopfield model ; infinite dimensional state space ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A generalization of the Little–Hopfield neural network model for associative memories is presented that considers the case of a continuum of processing units. The state space corresponds to an infinite dimensional euclidean space. A dynamics is proposed that minimizes an energy functional that is a natural extension of the discrete case. The case in which the synaptic weight operator is defined through the autocorrelation rule (Hebb rule) with orthogonal memories is analyzed. We also consider the case of memories that are not orthogonal. Finally, we discuss the generalization of the non deterministic, finite temperature dynamics.
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  • 81
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    Dynamics and control 10 (2000), S. 47-61 
    ISSN: 1573-8450
    Keywords: stability ; robust control ; Lyapunov approach ; discrete system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Control design of nonlinear discrete-time uncertain systems with (possibly fast) uncertain parameters is considered. We study the effect of only partially compensating the uncertainty. The optimal choice of a design parameter, which indicates the amount of compensation, is recommended.
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  • 82
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    Dynamics and control 10 (2000), S. 255-276 
    ISSN: 1573-8450
    Keywords: continuous-time systems ; frequency weighted model reduction ; gradient flow ; optimization ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Inthis paper, a model reduction technique based on optimizationis presented. The objective function minimized is the impulseenergy of the overall system. An extension of the technique tothe frequency weighted case is also presented, where single-sidedor double-sided weightings can be incorporated in the reductionprocedure. The paper proposes an alternative to find an optimizationsolution by solving ordinary differential equations which aregradient flow associated with the objective function to be minimized.Two examples are presented to illustrate the effectiveness ofthe method.
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  • 83
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    Aquaculture international 8 (2000), S. 159-168 
    ISSN: 1573-143X
    Keywords: emersion ; growth ; Pecten maximus ; scallop spat ; survival ; transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Scallop spat production normally requires transfer between growthsystems. Simulated transport experiments were carried out in April, June,December and February to evaluate effects of transport time on greatscallop (Pecten maximus) spat growth and survival. The spat (1.7–1.8 mm in shell-height and 21–25 µg ash free dry weight [AFDW]) wereheld in moist coffee filters at a temperature of 10 °C for up to 24 h,before being replaced into sieves in rearing tanks at 15 °C. The studyshowed that by increasing air emersion time, survival and growthdecreased. No significant difference in the results between 0 and 4 h of airemersion was found, while the effects after 12 and 24 h differed betweenspat groups. Survival and growth rates showed seasonal differences. Meansurvival was 35–71% in April and 77–99% from June to February. In Junemean growth rates attained were 115–128 µm shell-height and 15–18µg AFDW per day compared with 49–69 µm and 3.8–7.0 µgper day for the other spat groups. Great scallop spat may survive atransfer time of 24 h, but transportation for longer than 12 h is notrecommended if subsequent high survival and growth rates are to beensured.
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  • 84
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    Aquaculture international 8 (2000), S. 207-225 
    ISSN: 1573-143X
    Keywords: growth ; mortality ; Pecten maximus ; suspended culture
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Growth and mortality of the king scallop, Pecten maximus, werecompared when grown in cages and by ear hanging in suspended culturein Fuengirola, Malaga, in southern Spain. Seed (juveniles) used in theexperiment was collected in September 1997 that had settled on collectorsin April-June, of that year. Culture in suspended cages began in January1998 when the seed measured 42.7 (3.3) mm shell height and ended inFebruary 1999. Significantly faster growth was found at a minimum culturedensity (16 scallops/cage) than at two other densities (24 and 36scallops/cage). Depth (1, 5 and 10 m from the bottom) influenced growth,poorest growth occurred closest to the bottom. Under optimum growingconditions, 16 scallops/cage suspended 10 m from the bottom, scallops grewto 10 cm shell length (legal size) by February 1999.In ear hanging culture, ropes were moored in April (51.3 (4.5) mm),June (58.2 (4.5) mm) and November 1998 (64.3 (4.9) mm).Initially, rapid shell growth was observed in all three cultures.Subsequently, the shells became covered with barnacles, Balanus sp.,that possibly caused total mortality of the April culture and led to highmortalities in the two other cultures.
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  • 85
    ISSN: 1573-143X
    Keywords: growth ; silver perch (Bidyanus bidyanus) ; size grading ; size variation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study presents two experiments addressing growth and size variation in fingerling silver perch (Bidyanus bidyanus. In the first experiment, fish close to mean population size were raised either in the presence or absence of five larger fish for 60 days. Mean specific growth rate (SGR) and increases in the coefficient of variation and skewness were lower in the presence of larger fish, indicating a negative effect of large fish on the growth of smaller ones. In the second experiment, fingerlings were graded into groups smaller and larger than the median size of the population and raised in size-sorted groups of 60 large or small fish and mixed groups of 30 fish of each size category, for 60 days. There was no difference in mean SGR among groups, nor between the mixed group ad the weighted mean of the small and large groups. Biomass gain was higher in the mixed groups than in the weighted small-and-large groups, probably due to a slightly lower survival in the groups comprised of large fish. The fact that the effect of large fingerlings on the growth of smaller ones was evident in the first, but not the second, experiment may be attributed to higher size disparity between large and small fingerlings in the first experiment.
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  • 86
    ISSN: 1573-143X
    Keywords: 17 β-estradiol ; fish meal ; gonadal development ; growth ; Nile tilapia (Oreochromis niloticus) ; plant proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract This study was conducted to evaluate theeffect of plant protein‐based diets on gonadaldevelopment and plasma 17 β-estradiol (E2) levelin female Nile tilapia Oreochromis niloticus.Fish with a mean body weight of 6.7 (0.1) g were fedfour different diets with the same digestible protein(DP) and digestible energy (DE) containing gradedlevels of a mixture of plant ingredients as partial ortotal replacement of fish meal protein for 20 weeks.The control diet (D0) was based on fish meal, twodiets containing 33% (D33) and 66% (D66) of plantprotein, and one diet containing only plant protein(D100). Fish were sampled at 12 and 20 weeks. Nosignificant differences were found in different stagesof oocyte development and plasma E2 levels betweentilapia fed diets D0 and D100 at 12 weeks. Eight weekslater tilapia fed diet D0 showed a higher (P 〈 0.05)level of E2 than the D100 group. This difference andthe reduced proportion of vitellogenic and matureoocytes demonstrated that diets containing only plantprotein are less efficient in terms of tilapia growthand consequently ovarian development.
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    Aquaculture international 8 (2000), S. 455-461 
    ISSN: 1573-143X
    Keywords: floating cages ; growth ; pink dentex (Dentex gibbosus) ; sparids (Dentex dentex, Sparus aurata, Spondyliosoma cantharus, Diplodus puntazzo)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Aquatic geochemistry 6 (2000), S. 1-17 
    ISSN: 1573-1421
    Keywords: lakes ; density ; compressibility ; expansibility ; conductivity ; stability ; pvt properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In recent years, a number of workers have studied the stability of deep lakes such as Lake Tanganyika, Lake Baikal and Lake Malawi. In this paper, the methods that can be used to determine the effect that the components of lakes have on the equation of state are examined. The PVT properties of Lakes have been determined by using apparent molal volume data for the major ionic components of the lake. The estimated PVT properties (densities, expansibility and compressibilities) of the lakes are found to be in good agreement with the PVT properties (P) of seawater diluted to the same salinity. This is similar to earlier work that showed that the PVT properties of rivers and estuarine waters could also be estimated from the properties of seawater. The measured densities of Lake Tanganyika were found to be in good agreement (± 2 × 10-6 g cm-3) with the values estimated from partial molal properties and the values of seawater at the same total salinity (ST = 0.568‰). The increase in the densities of Lake Tanganyika waters increased due to changes in the composition of the waters. The measured increase in the measured density (45 × 10-6 g cm-3) is in good agreement (46 × 10-6 g cm-3) with the values calculated for the increase in Na+, HCO3 -, Mg2+, Ca2+ and Si(OH)4. Methods are described that can be used to determine the conductivity salinity of lakes using the equations developed for seawater. By combining these relationships with apparent molal volume data, one can relate the PVT properties of the lake to those of seawater.
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  • 89
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    Aquaculture international 7 (2000), S. 369-382 
    ISSN: 1573-143X
    Keywords: growth ; haddock (Melanogrammus aeglefinus) ; larvae ; light intensity ; photperiod ; tank colour
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In two separate experiments, haddock (Melanogrammus aeglefinus) larvae were raised under different photoperiods (24L : 0D or 15L : 9D), or different combinations of tank colour (black or white) and light intensity (1.1 μmol s−1 m−2 or 18 μmol s−1 m−2). Growth (0.8% day−1 in standard length; 2.9% day−1 in body area) and survival (2%) were not significantly different between photoperiod treatments after 35 days. Larval survival was greater in white versus black tanks after 41 days (2% versus l%, respectively). Growth of larvae was impaired in black tanks at low (1.1 μmol s−1 m−2) light intensity (0.8% day−1 in standard length and 2.2% day−1 in body area versus 1.1% day 21 in standard length and 3.1% day−1 in body area, for all other treatments). Transmission and reflection of light was low in black tanks at low incident light, and there was very little upwelling light. The resultant poor prey to background contrast probably resulted in larvae being unable to consume sufficient food to sustain a level of growth comparable to that in other treatments.
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  • 90
    ISSN: 1573-143X
    Keywords: bivalve ; fouling ; growth ; Newfoundland ; nursery ; sea scallop (Placopecten magellanicus) ; spat
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Hatchery-reared sea scallop (Placopecten magellanicus) spat weremonitored for growth and recovery in three experiments to determine themost suitable system for nursery culture. In Experiment I, four size classesof nursery-sized spat held at two depths from October to July exhibiteddeclining growth rates over the winter period and increased growth ratesin the spring. Overall, season, depth and initial size had a significantinfluence on the absolute and specific growth rates of scallops. Recovery,defined as number of scallops remaining after mortality and loss of spatthrough gear mesh, was influenced by season and initial size, but notdepth. Scallops in the 3.0 mm+ size class had higher growth rates andrecovery than those in the 1.4–1.6 mm, 1.7–1.9 mm and 2.0–2.9 mm sizeclasses. In Experiment II, two gear types containing similar size spat werecompared. Growth rates were significantly higher in 3.0 mm pearl nets thanin 3.0 mm collector bags, although recovery was similar between the twoequipment types. Experiment III, two stocking densities of nursery-sizedspat were compared in collector bags. Neither growth rate nor recoverywere significantly different for the two densities (2600 and 5200spat/collector bag) tested. Overall, these studies indicated that importantparameters for optimizing the growth and recovery of scallops in a farm-based nursery system include season, initial spat size, deployment depthand gear type.
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  • 91
    ISSN: 1573-143X
    Keywords: nitrogen ; organic matter ; shrimp culture ; sulphur cycle bacteria ; water quality
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
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    Aquaculture international 8 (2000), S. 381-389 
    ISSN: 1573-143X
    Keywords: Arctic charr (Salvelinus alpinus) ; growth ; low temperature ; stocking density ; time restricted feeding,/kwd〉
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects of time restricted feeding, possibility of bottomfeeding and stocking density on the growth of Arctic charr(Salvelinus alpinus L.) were examined in fish held at lowtemperature (〈2 °C). Fish fed for a restricted time (1 h) hadsignificantly (p 〈 0.05) lower specific growth rate (0.15 vs0.32% per day) than those fed the same ration over an extendedtime period (12 h). Increasing stocking densities had a positive andsignificant effect (p 〈 0.05) on growth with SGR increasing from 0.27to 0.52% per day at 2–30 kg m-3. Fish withaccess to feed on the tank floor had a significantly higher (p 〈0.05) growth rate (0.3 vs 0.13% per day) than those without thepossibility to feed from the bottom. When fish were held underconditions without access to the bottom a doubling of the feed rationdid not result in a significant (p 〉 0.05) increase in growth rate(0.13 vs 0.12%percnt; per day).
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  • 93
    ISSN: 1573-1642
    Keywords: nitrogen ; phosphorus ; macroalgae ; estuary ; anthropogenic
    Source: Springer Online Journal Archives 1860-2000
    Topics: Architecture, Civil Engineering, Surveying , Energy, Environment Protection, Nuclear Power Engineering
    Notes: Abstract Our objective was to begin to investigate sources, sinks, and flux rates of nitrogen (N) and phosphorus (P) in Famosa Slough, a small (12 ha) highly modified urban estuary in San Diego, California, U.S.A. The hydrology of Famosa Slough has been modified by culverts that dampen tidal influence and seasonal runoff from two urban watersheds, each of which has been implicated as a nutrient source that generates nuisance algal blooms. In 1995 and 1996, the ranges of nutrients measured in the water column were extremely wide; upper values exceeded those in other estuaries identified as eutrophic. Average dissolved inorganic nitrogen ranged from 2 to 250 μM, while dissolved inorganic phosphorus ranged from 〈1 to 15 μM. Nutrient content of the water changed rapidly both spatially and temporally depending on the tides and rainfall. While tidal water dominated this system, especially in the dry season, our results indicate that Famosa Slough's small watershed, not the larger watershed of the San Diego River, was the major source of nutrients during rainfall. Sediment nutrients were also high (∼3 mg N g dry wt−1 and 0.600 mg P g dry wt−1). Short-term flux studies suggest that the large accumulations of opportunistic green macroalgae commonly found in this estuary, and possibly the sediments, may act as a large and rapid sink for nutrients during times of high nutrient supply. We suggest that small, shallow estuaries in urban settings may have more complex and rapid nutrient dynamics than those found in larger systems.
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    Mechanics of composite materials 36 (2000), S. 475-480 
    ISSN: 1573-8922
    Keywords: stability ; three-dimensional theory ; tribotechnics ; elastoplastic deformations ; viscoelasticity ; surface ; tracking and dead loads ; laminated coating ; piecewise-homogeneous model ; active loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The problem of surface instability of laminated coatings with inelastic properties is considered within the framework of a model of piecewise-homogeneous media on the basis of the three-dimensional linearized theory of stability. A general statement of the problem is formulated and the basic characteristic equations are derived. The solutions of particular problems are obtained for elastoplastic and viscoelastic models of solids.
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  • 95
    ISSN: 1573-8469
    Keywords: carbon ; cellulose ; cover crop ; damping-off ; discriminant analysis ; lignin ; nitrogen
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Stages of oat–vetch cover crop decomposition were characterized over time in terms of carbon and nitrogen cycling, microbial activity and damping-off pathogen dynamics in organically and conventionally managed soils in a field and a controlled incubation experiment. A measurement of relative growth consisting of radial growth of a fungal colony over non-sterilized soil divided by that over sterilized soil was used as an assay of suppressiveness. No differences in relative growth of Pythium aphanidermatum and Rhizoctonia solani were detected between organic and conventionally managed soils amended with cover crop residue. Significant effects of cover crop decomposition stage on the relative growth of both pathogens were obtained. Relative growth of P. aphanidermatum was highest just after incorporation and decreased 3 weeks after incorporation. Relative growth of R. solani was highest about 20 days after incorporation, and decreased 2 weeks later in the organic system, but continued to increase in the conventional system. In both experiments, the N or C content, C:N ratio or dry weight of retrieved debris were significantly correlated with relative growth of P. aphanidermatum. Relative growth of R. solani was significantly correlated with the C:N ratio of soil or the C or N content of debris. Microbial activity was not consistently associated with relative growth of either pathogen.
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  • 96
    Electronic Resource
    Electronic Resource
    Springer
    Journal of dynamical and control systems 6 (2000), S. 503-510 
    ISSN: 1573-8698
    Keywords: nonconservative mechanical systems ; stability ; Lyapunov functions ; attraction domain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mechanical systems subjected to dissipative, gyroscopic, conservative, and also nonconservative positional forces are considered. The question of the effect of dissipative, gyroscopic, and conservative forces on the motion stability of a mechanical systems is determined by classical Kelvin–Chetaev theorems [1]. The presence of nonconservative positional forces considerably complicates the situation and excludes direct application of these theorems. Applying Lyapunov's functions method the condition of asymptotic stability of a mechanical system under the action of all listed above forces is obtained. Moreover, the estimation of the attraction domain in phase space is found. The precession system which is used in the solution of some problems in the applied theory of the gyroscopic systems is also examined. The connection between the stability of origin and precession systems is detected. Theoretical results are applied to the stabilization problem of stationary motion of the balanced gimbal suspension gyro by means of external moments.
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  • 97
    Electronic Resource
    Electronic Resource
    Springer
    Wetlands ecology and management 8 (2000), S. 197-207 
    ISSN: 1572-9834
    Keywords: benthic invertebrates ; mitigation ; nitrogen ; organic matter ; pedogenesis ; phosphorus ; plant productivity ; restoration and rehabilitation ; salt marsh ; wetland creation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The development of wetland soil characteristics andbenthic invertebrate communities were evaluated increated Spartina alterniflorasalt marshes inNorth Carolina ranging in age from 1 to 25 years-old.A combination of measurements from different-agecreated marshes as well as periodic measurements overtime on two marshes were used to (1) document rates ofwetland pedogenesis, especially soil organic matter,and, (2) explore relationships between soil andbenthic invertebrate community development. Soilmacro-organic matter (MOM, the living and dead rootand rhizome mat), organic C and N increased and bulkdensity decreased during the 25 years following marshestablishment. The most dramatic changes in bulkdensity, MOM, C and N occurred within the upper 10 cmof the soil with lesser changes below this depth.Created marshes were sinks for organic C (90–140g·m-2·yr-1) and N (7–11g·m-2·yr-1) but not for P (0–1g·m-2·yr-1). The density of benthicinvertebrates (〉250 μm) and subsurface-depositfeeding oligochaetes also increased over time oncreated salt marshes. Invertebrate and oligochaetedensity were strongly related to MOM content(r2= 0.83–0.87) and soil organic C(r2= 0.52–0.82) and N (r2= 0.62–0.84). Thesefindings suggest that, in created salt marshes,development of the benthic invertebrate community istied to marsh soil formation, especially accumulationof organic matter as MOM and soil. Field studies thatmanipulate the quantity and quality of soil organicmatter are needed to elucidate the relationshipbetween salt marsh pedogenesis and benthicinvertebrate community development.
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  • 98
    ISSN: 1573-5036
    Keywords: ammonia exchange ; apoplast ; atmosphere ; glutamine synthetase ; nitrogen ; photorespiration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract Plants have a compensation point for NH3 which ranges from 0.1 to 20 nmol mol-1, and may be several-fold higher or lower than naturally occurring atmospheric NH3 concentrations. This implies that NH3 fluxes over vegetated surfaces are bi-directional and that ammonia exchange with the atmosphere in many cases contributes significantly to the nitrogen economy of vegetation. Physiological regulation of plant–atmosphere NH3 fluxes is mediated via processes involved in nitrogen uptake, transport and metabolism. A rapid turnover of NH3 + in plant leaves leads to the establishment of a finite NH3 + concentration in the leaf apoplastic solution. This concentration determines, together with that of H+, the size of the NH3 compensation point. Barley and oilseed rape plants with access to NH3 + in the root medium have higher apoplastic NH3 + concentrations than plants absorbing NO3 -. Furthermore, the apoplastic NH3 + concentration increases with the external NH3 + concentration. Inhibition of GS leads to a rapid and substantial increase in apoplastic NH3 + and barley mutants with reduced GS activity have higher apoplastic NH3 + than wild-type plants. Increasing rates of photorespiration do not affect the steady-state NH3 + or H+ concentration in tissue or apoplast of oilseed rape, indicating that the NH3 + produced is assimilated efficiently. Nevertheless, NH3 emission increases due to a temperature-mediated displacement of the chemical equilibrium between gaseous and aqueous NH3 in the apoplast. Sugarbeet plants grown with NO3 - seem to be temporarily C-limited in the light due to a repression of respiration. As a consequence, the activity of chloroplastic GS declines during the day causing a major part of NH3 + liberated in photorespiration to be assimilated during darkness when 2-oxoglutarate is supplied in high rates by respiration.
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  • 99
    ISSN: 1573-5036
    Keywords: growth ; inflow ; magnesium ; potassium ; (Prunus)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract The effects (and interaction) of two solution concentrations of Mg (50, 500, μM) and two of K (250, 4250 μM) on the growth of micropropagated plants of “F. 12/1” and “Colt” were investigated using a flowing solution culture system. Magnesium inflow and growth of “Colt” and “F. 12/1” were inhibited to a similar extent by an increased concentration of K in the nutrient solution. However, the consequences of this inhibition were different. Reduced inflow of Mg in “F. 12/1” caused Mg deficiency symptoms at high and low concentrations of K, whereas this only occurred with a combination of high K concentration and low Mg concentration in “Colt”. The distribution of dry matter within the plant was significant in determining susceptibility to Mg deficiency. Since “F. 12/1” has a smaller root:shoot ratio than Colt it is unable to sustain the same concentration of Mg in leaves as “Colt” irrespective of external K concentration. The molar ratio of K:Mg in soil solutions should remain 〈8.5:1 in order to ensure maximum growth of “F. 12/1” and “Colt”.
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  • 100
    ISSN: 1573-5036
    Keywords: cereal ; cereal quality ; cereal yields ; natural regeneration ; nitrogen ; nitrogen uptake ; rye-grass ; set-aside ; white clover
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract During the period 1993–1997, at six contrasting sites located throughout England, two successive cereal test crops were grown both with and without nitrogen fertiliser after three or five years of set-aside or after continuous arable cropping. Vegetation during set-aside included natural regeneration and perennial rye-grass (Lolium perenne) with or without white clover (Trifolium repens), managed by mowing on one or more occasions per year. Establishment of the successive cereal test crops after destruction of the set-aside was generally not a problem. Fertile tiller numbers were increased by inclusion of clover in the set-aside cover or application of inorganic nitrogen. The presence of couch grass (Elytrigia repens) or volunteer cereals in the set-aside covers provided alternative hosts for take-all (Gaeumanomyces graminis) and eyespot (Pseudocercosporella herpotrichoides) and take-all caused some yield reductions in following cereal crops. Management during the set-aside period significantly affected grain yields of the subsequent cereal crops in the majority of the site-year combinations. However, these effects were not as large as would be expected after traditional break crops and were frequently masked by the application of nitrogen fertiliser. Mean yields increased by 80% due to the application nitrogen at the optimum rate compared to nil nitrogen. Most of the effects of set-aside treatment on grain yield were shown to be attributable to soil mineral nitrogen content, but at some sites, infections by take-all or eyespot also accounted for some of the variation. There were no effects of pests that could be related to treatment. The presence of sown clover during the set-aside period had the most consistent effect across sites, affecting tiller populations, grain yield and grain quality of cereal crops. At some sites, establishing a sown cover during the set-aside period, or cutting the cover more than once a year, improved grain yield and quality, and reduced the incidence of some specific weeds and disease.
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