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  • Triticum aestivum  (266)
  • nitrogen  (227)
  • stability  (198)
  • Chemistry
  • ddc:330
  • Springer  (693)
  • Bremen : Bremer Tabak-Collegium  (1)
  • 1990-1994  (694)
  • 1
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    Bremen : Bremer Tabak-Collegium | Wuppertal : Wuppertal Institut für Klima, Umwelt, Energie
    Publikationsdatum: 2014-08-15
    Schlagwort(e): ddc:330
    Repository-Name: Wuppertal Institut für Klima, Umwelt, Energie
    Sprache: Deutsch
    Materialart: bookpart , doc-type:bookPart
    Standort Signatur Erwartet Verfügbarkeit
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  • 2
    Digitale Medien
    Digitale Medien
    Springer
    Computing 51 (1993), S. 271-292 
    ISSN: 1436-5057
    Schlagwort(e): 65N15 ; 65N99 ; 35A40 ; Box method ; boundary value problem ; finite volume method ; variational formulation ; stability ; error bounds
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Box-Methoden (Finite-Volumen-Methoden) sind verbreitete Verfahren zur Lösung physikalischer Erhaltungsgleichungen, insbesondere in der Strömungsmechanik. In dieser Arbeit werden zwei Methoden für elliptische Differentialgleichungen untersucht, die Diagonal-Boxen und die Schwerpunkt-Boxen. Da die Box-Methoden im Sinne von Petrov-Galerkin-Verfahren interpretiert werden können, erhält man vergleichbar zur Finiten-Element-Methode eine variationsrechnerische Stabilitäts- und Fehleranalyse. Damit werdenO(h)- undO(h 2)-Fehlerabschätzungen hergeleitet. Lokale Eigenwertprobleme führen zu Stabilitätsaussagen. Allerdings ergibt sich eine Abhängigkeit von der Anzahl und Art gestörter Vierecke. Insbesondere die Diagonal-Boxen sind anfällig für lokale Störungen.
    Notizen: Abstract Box schemes (finite volume methods) are widely used in fluiddynamics, especially for the solution of conservation laws. In this paper two box-schemes for elliptic equations are analysed with respect to quadrilateral meshes. Using a variational formulation, we gain stability theorems for two different box methods, namely the so-called diagonal boxes and the centre boxes. The analysis is based on an elementwise eigenvalue problem. Stability can only be guaranteed under additional assumptions on the geometry of the quadrilaterals. For the diagonal boxes unsuitable elements can lead to global instabilities. The centre boxes are more robust and differ not so much from the finite element approach. In the stable case, convergence results up to second order are proved with well-known techniques.
    Materialart: Digitale Medien
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  • 3
    Digitale Medien
    Digitale Medien
    Springer
    European journal of nutrition 29 (1990), S. 219-228 
    ISSN: 1436-6215
    Schlagwort(e): Vitamin K ; Menadion ; Menadiol ; Bioverfügbarkeit ; Stabilität ; Geflügel ; vitamin K ; menadione ; menadiol ; bioavailability ; stability ; poultry
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft , Medizin
    Beschreibung / Inhaltsverzeichnis: Summary A bioassay of vitamin K is described, based on the prothrombin clotting time of 3-week-old, vitamin-K-depleted, and cumatetralyl-sensitized male broiler chicks, using a homologous thrombokinase preparation. With this test it could be shown that the diacetate and dibutyrate esters of menadiol are vitamin-K-active. The bioactivity of menadione from these menadiolesters amounted to about 70 % of the standard menadione from a coated menadione sodium bisulfite (Dohyfral). Menadiol seems to be temperature-resistant under such conditions, whereby two uncoated MSB preparations lost about 60 % of their activity.
    Notizen: Zusammenfassung In einem biologischen Testverfahren an Cumatetralyl sensibilisierten Küken konnte in 3 Versuchen anhand des Parameters Thromboplastinzeit mit homologer Thrombokinase gezeigt werden, da\ Menadioldiacetat und Menadioldibutyrat Vitamin-K-wirksam sind. Die biologische Wirksamkeit von Menadion aus diesen Menadiolestern betrug ca. 70 % der Menadionaktivität aus gecoatetem Menadionbisulfit (Dohyfral®). Im Gegensatz zu 2 ungeschützten MSB-Präparationen, welche bei Wärmebelastung ca. 60 % ihrer ursprünglichen Wirkung verloren, waren die Menadiolester temperaturstabil.
    Materialart: Digitale Medien
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  • 4
    Digitale Medien
    Digitale Medien
    Springer
    OR spectrum 16 (1994), S. 47-52 
    ISSN: 1436-6304
    Schlagwort(e): Vector optimization ; approximately efficient solutions ; stability ; Vektoroptimierung ; Näherungslösungen ; Stabilität
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Wirtschaftswissenschaften
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Wir führen ein Konzept für Näherungslösungen in der Vektoroptimierung ein und vergleichen dieses mit einem neuen Konzept aus [8]. Weiterhin untersuchen wir Beziehungen zwischen der Menge der Näherungslösungen eines Vektoroptimierungsproblems und den Näherungslösungen eines entsprechenden parametrischen Ersatzproblems. Schließlich beweisen wir Stabilitätseigenschaften des skalaren Ersatzproblems.
    Notizen: Abstract We introduce a concept for approximately efficient solutions in vector optimization and compare it with another recent concept given in [8]. Further, we study relations between the set of approximately efficient solutions of a vector optimization problem and the approximate solutions of a corresponding parametric surrogate optimization problem. Finally, we prove stability properties for the scalar surrogate problem.
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  • 5
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 47 (1990), S. 117-141 
    ISSN: 1436-4646
    Schlagwort(e): Bifurcation ; singularity ; parametric programming ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract The structure of solutions to the nonlinear parametric programming problem with a one dimensional parameter is analyzed in terms of the bifurcation behavior of the curves of critical points and the persistence of minima along these curves. Changes in the structure of the solution occur at singularities of a nonlinear system of equations motivated by the Fritz John first-order necessary conditions. It has been shown that these singularities may be completely partitioned into seven distinct classes based upon the violation of one or more of the following: a complementarity condition, a constraint qualification, and the nonsingularity of the Hessian of the Lagrangian on a tangent space. To apply classical bifurcation techniques to these singularities, a further subdivision of each case is necessary. The structure of curves of critical points near singularities of lowest (zero) codimension within each case is analyzed, as well as the persistence of minima along curves emanating from these singularities. Bifurcation behavior is also investigated or discussed for many of the subcases giving rise to a codimension one singularity.
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  • 6
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 54 (1992), S. 57-67 
    ISSN: 1436-4646
    Schlagwort(e): Matchings ; stability ; extreme points ; polytope
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract The purpose of this paper is to extend a modified version of a recent result of Vande Vate (1989) which characterizes stable matchings as the extreme points of a certain polytope. Our proofs are simpler and more transparent than those of Vande Vate.
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  • 7
    Digitale Medien
    Digitale Medien
    Springer
    Mathematical programming 61 (1993), S. 197-214 
    ISSN: 1436-4646
    Schlagwort(e): Epi-convergence ; epi-distance ; stability ; convex optimization ; approximate solutions ; subgradients ; level sets
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Mathematik
    Notizen: Abstract We prove that theε-optimal solutions of convex optimization problems are Lipschitz continuous with respect to data perturbations when these are measured in terms of the epi-distance. A similar property is obtained for the distance between the level sets of extended real valued functions. We also show that these properties imply that theε-subgradient mapping is Lipschitz continuous.
    Materialart: Digitale Medien
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  • 8
    Digitale Medien
    Digitale Medien
    Springer
    Computing 44 (1990), S. 187-196 
    ISSN: 1436-5057
    Schlagwort(e): 65M10 ; Spectral method ; stability ; stability threshold
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Zur numerischen Lösung einer nichtlinearen Differentialgleichung dritter Ordnung, herrührend aus einem Strömungsproblem bei Gasteilchen, wird ein zeitdiskreter Pseudo-spektral-Algorithmus vorgeschlagen. Stabilität und Konvergenz des neuen Differenzenverfahrens werden analysiert. Numerische Vergleiche mit bestehenden Differenzenschemata sprechen klar zugunsten des neuen Verfahrens.
    Notizen: Abstract A time-discrete pseudospectral algorithm is suggested for the numerical solution of a nonlinear third order equation arising in fluidization. The nonlinear stability and convergence of the new scheme are analyzed. Numerical comparisons with available finite-difference methods are also reported which clearly indicate the superiority of the new scheme.
    Materialart: Digitale Medien
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  • 9
    Digitale Medien
    Digitale Medien
    Springer
    Acta biotheoretica 39 (1991), S. 1-14 
    ISSN: 1572-8358
    Schlagwort(e): Hematological diseases ; first order partial differential equations ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract To address the possibility that proliferative disorders may originate from interactions between multiple populations of proliferating and maturing cells, we formulate a model for this process as a set of coupled nonlinear first order partial differential equations. Using recent results for the asymptotic behaviour of the solutions to this model, we demonstrate that there exists a region of coupling coefficients, maturation rates, and proliferation rates that will guarantee the stable coexistence of coupled cellular populations. The analysis shows that increases in the coupling between populations may ultimately lead to a loss of stability. Furthermore, the analysis indicates that increases (decreases) in the maturation and/or proliferation rates above (below) critical levels will lead either to instability in the populations or the destruction of one population and the persistence of the other.
    Materialart: Digitale Medien
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  • 10
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 58 (1991), S. 69-74 
    ISSN: 1570-7458
    Schlagwort(e): Rhopalosiphum padi ; antixenosis ; plant resistance ; Triticum aestivum
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Antixenose gegenüberRhopalosiphum padi (L.) in den drei Weizensorten Timmo, Moghan 2 und Ommid, von denen die zwei letzteren Sorten aus dem Iran stammen, wurde unter Verwendung des systemischen Insektizids Pirimicarb gemessen. Jeweils zwei Pflanzen aus verschiedenen Sorten wurden als Paar verwendet (in allen Kombinationen der drei Sorten), pro Paar ein Topf mit Pirimicarb gegossen, und zwanzig Blattlaüse über Blattflächen von beiden Sorten gekäfigt. Ähnliche Versuche wurden auch ohne Insektizid ausgeführt. Beide Methoden zeigten deutliche Antixenose von Moghan 2 und Ommid in Vergleich mit Timmo. Die Insektizidmethode zeigte auch eine Bevorzugung von Moghan 2 gegenüber Ommid, ein Resultat, das mit der schon bekannten relativen Antibiose dieser zwei Sorten übereinstimmte, während sich ohne Insektizid kein solcher Unterschied erwies. Die statistische Analyse solcher Versuche mit einem Insektizid, die eine Modifikation der Berechnung des erwarteten Werts mit dem χ2 Test enthält, ist beschrieben.
    Notizen: Abstract Antixenosis in three wheat varieties (Timmo, Moghan 2 and Ommid) toRhopalosiphum padi (L.) was measured by pairing plants of any two varieties with one plant of each pair treated with a soil drench of the systemic insecticide pirimicarb. Aphids were then allowed access to equivalent leaf areas from the two plants in a leaf cage. The results were compared with similar choice experiments without insecticide. By either technique, the two Iranian varieties (Moghan 2 and Ommid) showed antixenosis in comparison with Timmo. The statistical analysis of the data, using a heterogeneity χ2 test, is described.
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  • 11
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 64 (1992), S. 225-238 
    ISSN: 1570-7458
    Schlagwort(e): Lymantria dispar (L.) ; diet switching ; nitrogen ; specialization ; plant-animal interactions ; insect behavior
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Gypsy moth (Lymantria dispar (L.) (Lepidoptera: Lymantriidae)) larvae were reared from hatch on 1.25% N or 3.5% N artificial diet (previous diet) and switched reciprocally to the other diet (current diet) after molting into the second, third, fourth, or fifth instar. The nitrogen concentration of food consumed during previous instars had a strong residual effect on the growth rate in subsequent instars when a diet switch was made during instars two through four, but did not affect growth rate of fifth-instar larvae despite effects on food consumption and utilization. In early instars, larvae reared on 1.25% N artificial diet and then switched to 3.75% N diet had lower mass-adjusted growth rates than larvae continuously reared on 3.75% N diet. Conversely, larvae reared on 3.75% N diet and switched to 1.25% N had higher mass-adjusted growth rates than larvae reared continuously on 1.25% N diet. Relative to larvae previously reared on 1.25% N diet, fifth-instar male larvae previously reared on 3.75% N diet had slightly lower consumption rates, higher net growth efficiency (ECD), and higher gross growth efficiency (ECI). Larvae previously reared on 3.75% N diet tended to have lower food assimilation efficiency (AD) and lower nitrogen assimilation efficiency (AD(N)). Although both previous and current diet nitrogen concentration strongly affected larval growth and food utilization, the interaction term between these was not significant for any response variables except ECD and ECI. Because the interaction term reflects the effect of switching per se, the results indicate that there was a metabolic cost associated with switching, but no inherent net cost or benefit of diet-switching to growth.
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  • 12
    ISSN: 1570-7458
    Schlagwort(e): LepidopteraEphestia kuehniella ; α-amylase ; Triticum aestivum ; endosperm ; α-amylase inhibitors
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract Crude α-amylase preparations from seven Lepidoptera pests were susceptible to inhibition by salt-soluble proteins of bread wheat (Triticum aestivum L.) endosperm. Protein fractions that corresponded to tetrameric, dimeric, and monomeric wheat α-amylase inhibitors, were decreasingly effective against the insect α-amylase activity. To further confirm these results, purified inhibitors were tested against an α-amylase preparation fromEphestia kuehniella (Zeller). This preparation showed decreased activity when increasing amounts of an heterotetrameric inhibitor (reconstituted from its isolated subunits WTAI-CM2, -CM3 and -CM16) were assayed. Activity was only partially inhibited by homodimeric (WDAI-1, synonym 0.53; WDAI-2, synonym 0.19) and monomeric (WMAI-1, synonym 0.28) inhibitors.
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  • 13
    Digitale Medien
    Digitale Medien
    Springer
    Entomologia experimentalis et applicata 61 (1991), S. 7-16 
    ISSN: 1570-7458
    Schlagwort(e): Plutella xylostella ; Trichoplusia ni ; Hellula phidilealis ; Artogeia rapae ; nitrogen ; population growth ; cabbage
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effects of different nitrogen (N) fertilization rates (0, 45, 90, and 168 kg N/ha), plant nitrogen concentration, and plant biomass on abundance and population growth of diamondback moth, Plutella xylostella (L.), cabbage looper, Trichoplusia ni (Hübner), cabbage budworm, Hellula phidilealis (Walker), imported cabbageworm, Artogeia rapae (L.), and cross-striped cabbageworm, Evergestis rimosalis (Guenée), were investigated in Homestead and Sanford, Florida in 1987. The effects of these factors on the parasitization of P. xylostella were also examined. In Homestead, abundance of most insect pests and parasitized P. xylostella increased with an increase in the level of N applied and with an increase in plant biomass. Similar results were found in Sanford, although results were not consistently significant. Abundance of most insect pests was significantly positively correlated with plant N concentration. Multiple regression analyses indicated that foliar biomass was significantly more important than N fertilization rate and subsequent plant N concentration at predicting abundance of insect pests and parasitized P. xylostella on cabbage.
    Materialart: Digitale Medien
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  • 14
    Digitale Medien
    Digitale Medien
    Springer
    Journal of intelligent manufacturing 4 (1993), S. 183-198 
    ISSN: 1572-8145
    Schlagwort(e): Assembly planning ; subassembly ; liaison graph ; geometric reasoning ; assembly cost ; stability ; partial-order graph
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau
    Notizen: The distribution of assembly workstations enables assembly operations to be done in parallel, while the multiple routing of parts in flexible assembly systems allows the opportunistic scheduling of assembly operations. This paper presents an assembly planning system, called the Assembly Coplanner, which automatically constructs an assembly partial order and generates a set of assembly instructions from a liaison graph representation of an assembly based on the extraction of preferred subassemblies. Assembly planning in Coplanner is carried out by the co-operation of multiple planning agents, such as the geometric reasoner, the physical reasoner, the resource manager and the plan coordinator, under the constraints of finding a cost-effective assembly plan in a flexible assembly system. The Coplanner identifies spatial parallelism in assembly as a means of constructing temporal parallelism among assembly operations. This is achieved in the following way: (1) the selection of a set of tentative subassemblies by decomposing a liaison graph into a set of subgraphs based on feasibility and difficulty of disassembly; (2) the evaluation of each of the tentative subassemblies in terms of assembly cost represented by subassembly selection indices; and (3) the construction of a hierarchical partial order graph (HPOG) as an assembly plan. A case study applying the Coplanner to a mechanical assembly is illustrated in this paper.
    Materialart: Digitale Medien
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  • 15
    Digitale Medien
    Digitale Medien
    Springer
    Journal of polymers and the environment 1 (1993), S. 275-279 
    ISSN: 1572-8900
    Schlagwort(e): Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene (ABS) ; ABS/polycarbonate blend
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik , Maschinenbau
    Notizen: Abstract The thermal oxidative stability of various ABS/PC compounds was studied by means of the chemiluminescence technique. Similarly to pure ABS, Irganox 1076 and Irganox MD 1024 perform as moderate antioxidants in ABS/PC and (ABS/PC + lubricant) blends. Neither Tinuvin 144, Irgaphos 168, nor their mixture affects the durability of the ABS/PC blend. At the same time, (Irgaphos 168 + Tinuvin 144) in combination with Irganoxes was found to provide a noticeable enhancement in durability to the (ABS/PC + lubricant) system. Titanium dioxide pigments by themselves have only a slight influence on the oxidative stability of the ABS/PC blend. Durability of the (ABS/PC + pigment) and (ABS/PC + lubricant) systems was found to be the same and the overall protective effect of Irganox 1076 was similar in both the (ABS/PC + lubricant) and the (ABS/PC + lubricant + pigment) systems. Certain modifiers significantly improve the durability of the ABS/PC compounds, although their function may differ in the systems with and without pigments.
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  • 16
    ISSN: 1572-8900
    Schlagwort(e): Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene (ABS)
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie , Energietechnik , Maschinenbau
    Notizen: Abstract The influence of lubricants, UV stabilizers, antioxidants, and metal deactivators on the resistance of ABS to thermal oxidation was studied by means of the chemiluminescence technique. Neither of the additives seems to affect significantly the induction period of oxidation. At the same time, the influence of various additives on the oxidation rate constant is remarkably different: the introduction of lubricants and UV stabilizers increases its value, while antioxidants and metal deactivators have the opposite effect. For the particular systems studied durability is decreased in samples containing the lubricant and UV stabilizers and increased in samples stabilized with the antioxidant and metal deactivator.
    Materialart: Digitale Medien
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  • 17
    Digitale Medien
    Digitale Medien
    Springer
    Journal of inorganic and organometallic polymers and materials 2 (1992), S. 79-85 
    ISSN: 1572-8870
    Schlagwort(e): Phthalocyanines ; polymers ; siloxanes ; conductivity ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The author's work on the incorporation of phthalocyanines into inorganic polymers is reviewed. The synthesis of poly(siloxane phthalocyanines) and the synthesis and characterization of fluoro(phthalocyanine) Group III compounds and their conducting derivatives are described.
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  • 18
    ISSN: 1572-8927
    Schlagwort(e): Chromium(III) ; β-diketones ; β-diketonates ; chelation ; complexation ; correlation ; stability ; equilibrium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract It has been demonstrated that the logarithm of the stability constant of some monochelated chromium(III) compounds, with structurally similar 1,3-dicarbonylic species, is linearly related to the negative logarithm of the acid ionization constant of the ligand. Graphical and analytical correlations which could be useful in predicting equilibrium constants of chromium(III)-β-diketonates, as well as other first-row transition metal derivatives, have been developed. A quantitative evaluation of the complexes stability has been carried out, providing information about the effects of ligand substituents on the equilibrium constants.
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  • 19
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 10 (1991), S. 225-232 
    ISSN: 1572-879X
    Schlagwort(e): VPI-5 ; stability ; molecular sieve ; post-synthesis treatments
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Thorough washing of a VPI-5 synthesized with n-dipropylamine as template improves greatly its thermal stability while no major change is observed in the template content. A detailed study of the influence of the pretreatment conditions shows that in order to obtain a high thermal stability (up to at least 960 °C) two parameters are of importance. The removal of both the template and the adsorbed water requires either a low heating rate at atmospheric pressure or a low pressure (less than 3 Torr) when the heating rate is 300 ° per hour.
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  • 20
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 13 (1992), S. 45-53 
    ISSN: 1572-879X
    Schlagwort(e): Ammonia ; synthesis ; nitrogen ; rate-determining step ; potassium promotion
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The simple concept of a single rate-determining step, the dissociation of N2(a), in ammonia synthesis is inconsistent with experimental results. It is proposed that three reaction steps, N2(a) → 2N(a) (1) N(a) + H(a)→NH(a) (2) NH3(a)→NH3(g) (3) are dominant in determining the rate of synthesis. Under industrial conditions reactions (2) and (3) are more important than (1). The role of K+ as promoter in these reactions is discussed, especially as an “anchor” for adsorbed oxygen.
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  • 21
    Digitale Medien
    Digitale Medien
    Springer
    Catalysis letters 16 (1992), S. 159-164 
    ISSN: 1572-879X
    Schlagwort(e): Chemisorption ; nitrogen ; carbon dioxide ; platinum ; water gas shift reaction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract The relationship between sites responsible for nitrogen chemisorption and sites responsible for stronger adsorption of carbon dioxide on platinum black is reported. A 2 to 1 ratio has been found between molecules of more strongly adsorbed carbon dioxide and molecules of nitrogen chemisorbed on individual samples. This relationship has allowed us to deduce the structure of chemisorbed carbon dioxide. Carbon dioxide is relatively weakly chemisorbed on platinum. Reasons for the weakness of this chemisorption are discussed.
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  • 22
    Digitale Medien
    Digitale Medien
    Springer
    Journal of dynamics and differential equations 6 (1994), S. 37-51 
    ISSN: 1572-9222
    Schlagwort(e): Celestial mechanics ; relative equilibria ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A criterion for the linear stability of relative equilibria of the Newtoniann-body problem is found in the case whenn−1 of the masses are small. Several stable periodic orbits of the problem are presented as examples.
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  • 23
    Digitale Medien
    Digitale Medien
    Springer
    Order 9 (1992), S. 163-175 
    ISSN: 1572-9273
    Schlagwort(e): Primary 06A07 ; secondary 05C70 ; Partial order ; interval ; stability ; covering ; Sperner property ; symmetric chains ; NP-completeness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Given a finite ranked posetP, let α(P) be the maximum size of a subset ofP such that no two elements of it belong simultaneously to some interval ofP and let ϱ(P) be the minimum number of intervals covering all elements ofP. We say thatP has the strong interval stability property (resp. the strong interval covering property) if for each subposetP′ induced by consecutive levels ofP, i.e.,P′=P (l)∪...∪P (u), one has α(P′)=max{|P (l)|, |P (u)|} (resp. ϱ(P′)=max{|P (l)|, |P (u)|}). We prove these properties for several classes of posets and discuss some general facts concerning the numbers α(P) and ϱ(P), e.g., NP-completeness and min-max relations.
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  • 24
    Digitale Medien
    Digitale Medien
    Springer
    Queueing systems 12 (1992), S. 369-389 
    ISSN: 1572-9443
    Schlagwort(e): Perturbation analysis ; stability ; stochastic difference equations ; simulation
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract We investigate the stability of waiting-time derivatives when inputs to a queueing system-service times and interarrival times-depend on a parameter. We give conditions under which the sequence of waiting-time derivatives admits a stationary distribution, and under which the derivatives converge to the stationary regime from all initial conditions. Further hypotheses ensure that the expectation of a stationary waiting-time derivative is, in fact, the derivative of the expected stationary waiting time. This validates the use of simulation-based infinitesimal perturbation analysis estimates with a variety of queueing processes. We examine waiting-time sequences satisfying recursive equations. Our basic assumption is that the input and its derivatives are stationary and ergodic. Under monotonicity conditions, the method of Loynes establishes the convergence of the derivatives. Even without such conditions, the derivatives obey a linear difference equation with random coefficients, and we exploit this fact to find stability conditions.
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  • 25
    Digitale Medien
    Digitale Medien
    Springer
    Queueing systems 13 (1993), S. 87-110 
    ISSN: 1572-9443
    Schlagwort(e): Manufacturing systems ; semiconductor manufacturing ; thin film lines ; re-entrant lines ; scheduling policies ; queueing networks ; buffer priority policies ; due date policies ; stability ; stochastic control ; mean delay ; variance of delay ; machine failures ; set-up times
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract Traditionally, manufacturing systems have mainly been treated as either job shops or flow shops. In job shops, parts may arrive with random routes, with each route having a low volume. In flow shops, the routes are fixed and acyclic, as in assembly lines. With the advent of semiconductor manufacturing plants, and more recently, thin film lines, this dichotomy needs to be expanded to consider another class of systems, which we call “re-entrant lines”. The distinguishing feature of these manufacturing systems is that parts visit some machines more than once at different stages of processing. Scheduling problems arise because several parts at different stages of processing may be in contention with each other for service at the same machine. There may be uncertainties in the form of random service or set-up times, as well as random machine failures and repairs. The goal of scheduling is to improve performance measures such as mean sojourn time in the system, which is also known as the mean “cycle-time”, or the variance of the cycle-time. In this paper we provide a tutorial account of some recent results in this field. We describe several scheduling policies of interest, and provide some results concerning their stability and performance. Several open problems are suggested.
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  • 26
    Digitale Medien
    Digitale Medien
    Springer
    Queueing systems 15 (1994), S. 279-288 
    ISSN: 1572-9443
    Schlagwort(e): Sample-path ; point processes ; workload ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract In this paper, by exploiting recent results on the pathwise behavior of the workload process in single server, work conserving queues of theG/G/1/∞ type, we show that the workload of multiserver, work conserving queues ofG/G/m/∞ (m〈∞) (andG/G/∞) queues satisfies an o(t) growth condition, provided that the time average of the work brought into the system is less thanm form 〈 ∞ (and finite form=∞).
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  • 27
    Digitale Medien
    Digitale Medien
    Springer
    Queueing systems 16 (1994), S. 115-137 
    ISSN: 1572-9443
    Schlagwort(e): Polling systems ; stability ; stochastic continuity ; general arrival process ; functional limit theorems.
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract The stability of a polling system with exhaustive service and a finite number of users, each with infinite buffers is considered. The arrival process is more general than a Poisson process and the system is not slotted. Stochastic continuity of the stationary distributions, rates of convergence and functional limit theorems for the queue length and waiting time processes have also been proved. The results extend to the gated service discipline.
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  • 28
    Digitale Medien
    Digitale Medien
    Springer
    Celestial mechanics and dynamical astronomy 56 (1993), S. 45-50 
    ISSN: 1572-9478
    Schlagwort(e): Restricted problem ; stability ; planets of double stars
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract Numerical simulations are made within the framework of the plane restricted three-body problem, in order to find out if stable orbits for planets around one of the two components in double stars can exist. For any given set of initial parameters (the mass ratio of the two stars and the eccentricity of their orbit around each other), the phase-space of initial positions and velocities is systematically explored. In previous works, systematic exploration of the circular model as well as studies of more realistic (elliptic) cases such as Sun-Jupiter and the nearby α Centauri and Sirius systems, large stable planetary orbits were found to exist around both components of the binary, up to distances from each star of the order or more than half the binary's periastron separation. The first results presented here for the η Coronae Borealis system confirm the previous studies.
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  • 29
    Digitale Medien
    Digitale Medien
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    Celestial mechanics and dynamical astronomy 58 (1994), S. 203-213 
    ISSN: 1572-9478
    Schlagwort(e): libration points ; resonances ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The stability of the triangular libration points in the case when the first and the second order resonances appear was investigated. It was proved that the first order resonances do not cause instability. The second order resonances may lead to instability. Domains of the instability in the two-dimensional parameter space were determined.
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  • 30
    Digitale Medien
    Digitale Medien
    Springer
    Journal of dynamics and differential equations 5 (1993), S. 625-671 
    ISSN: 1572-9222
    Schlagwort(e): Scalar reaction-diffusion equation ; singular perturbation methods ; internal layer ; Neumann layer ; stability ; 35K57 ; 35B25 ; 35B35
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract The multiple existences and their stability properties of stationary solutions with a single transition layer in some scalar reaction-diffusion equation are shown. Each solution is constructed by using classical singular perturbation methods and its stability property is determined by a simple algebraic quantity, say index, appearing in the construction of a solution.
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  • 31
    Digitale Medien
    Digitale Medien
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    Journal of dynamics and differential equations 6 (1994), S. 639-658 
    ISSN: 1572-9222
    Schlagwort(e): Symmetry ; parabolic equations ; positive solutions ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Symmetry properties of positive solutions of a Dirichlet problem for a strongly nonlinear parabolic partial differential equation in a symmetric domainD ⊂ R n are considered. It is assumed that the domainD and the equation are invariant with respect to a group {Q} of transformations ofD. In examples {Q} consists of reflections or rotations. The main result of the paper is the theorem which states that any compact inC(D) negatively invariant set which consists of positive functions consists ofQ-symmetric functions. Examples of negatively invariant sets are (in autonomous case) equilibrium points, omega-limit sets, alpha-limit sets, unstable sets of invariant sets, and global attractors. Application of the main theorem to equilibrium points gives the Gidas-Ni-Nirenberg theorem. Applying the theorem to omega-limit sets, we obtain the asymptotical symmetrization property. That means that a bounded solutionu(t) asr→∞ approaches subspace of symmetric functions. One more result concerns properties of eigenfunctions of linearizations of the equations at positive equilibrium points. It is proved that all unstable eigenfunctions are symmetric.
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  • 32
    Digitale Medien
    Digitale Medien
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    Annals of operations research 27 (1990), S. 343-369 
    ISSN: 1572-9338
    Schlagwort(e): Bifurcation ; singularities ; continuation ; parametric nonlinear programming ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Wirtschaftswissenschaften
    Notizen: Abstract Bifurcation and continuation techniques are introduced as a class of methods for investigating the parametric nonlinear programming problem. Motivated by the Fritz John first-order necessary conditions, the parametric programming problem is first reformulated as a closed system of nonlinear equations which contains all Karush-Kuhn-Tucker and Fritz John points, both feasible and infeasible solutions, and relative minima, maxima, and saddle points. Since changes in the structure of the solution set and critical point type can occur only at singularities, necessary and sufficient conditions for the existence of a singularity are developed in terms of the loss of a complementarity condition, the linear dependence constraint qualification, and the singularity of the Hessian of the Lagrangian on a tangent space. After a brief introduction to elementary bifurcation theory, some simple singularities in this parametric problem are analyzed for both branching and persistence of local minima. Finally, a brief introduction to numerical continuation and bifurcation procedures is given to indicate how these facts can be used in a numerical investigation of the problem.
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  • 33
    Digitale Medien
    Digitale Medien
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    Queueing systems 14 (1993), S. 159-175 
    ISSN: 1572-9443
    Schlagwort(e): Queueing networks ; nonproduct form networks ; stability ; stochastic continuity ; functional limit theorems
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract A finite number of nodes, each with a single server and infinite buffers, is considered in discrete time. The service may be FIFO and the service times are constant. The external arrivals and the routing decision variables form a general stationary sequence. Stability of the system is proved under these assumptions. Extension to multiple servers at a node and general stationary distributions holds. If the external input is i.i.d. and the routing is Markovian then stochastic ordering, continuity of stationary distributions, rates of convergence, a functional CLT and a functional LIL and various other limit theorems for the queue length process are also proved. Generalizations to multiple servers at nodes, customers with priority, multiple customer classes, general service length and Markov modulated external arrival cases are discussed.
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  • 34
    Digitale Medien
    Digitale Medien
    Springer
    Queueing systems 15 (1994), S. 211-238 
    ISSN: 1572-9443
    Schlagwort(e): polling system ; stability ; Markov chain ; stochastic monotonicity ; heavy traffic ; nonpreemptive local priority
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract This paper deals with the stability of periodic polling models with a mixture of service policies. Customers arrive according to independent Poisson processes. The service times and the switchover times are independent with general distributions. The necessary and sufficient condition for the stability of such polling systems is established. The proof is based on the stochastic monotonicity of the state process at the polling instants. The stability of only a subset of the queues is also analyzed and, in case of heavy traffic, the order of explosion of the queues is given. The results are valid for a model with set-up times, and also when there is a local priority rule at the queues.
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  • 35
    Digitale Medien
    Digitale Medien
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    Queueing systems 17 (1994), S. 317-345 
    ISSN: 1572-9443
    Schlagwort(e): Single-server queue ; spatially distributed arrival points ; travelling server ; Brownian motion ; embedded Markov chain ; stability ; Tweedie's lemma ; regenerative processes ; stochastic decomposition ; equilibrium equations ; mean queue length
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract Consider a queueing system where customers arrive at a circle according to a homogeneous Poisson process. After choosing their positions on the circle, according to a uniform distribution, they wait for a single server who travels on the circle. The server's movement is modelled by a Brownian motion with drift. Whenever the server encounters a customer, he stops and serves this customer. The service times are independent, but arbitrarily distributed. The model generalizes the continuous cyclic polling system (the diffusion coefficient of the Brownian motion is zero in this case) and can be interpreted as a continuous version of a Markov polling system. Using Tweedie's lemma for positive recurrence of Markov chains with general state space, we show that the system is stable if and only if the traffic intensity is less than one. Moreover, we derive a stochastic decomposition result which leads to equilibrium equations for the stationary configuration of customers on the circle. Steady-state performance characteristics are determined, in particular the expected number of customers in the system as seen by a travelling server and at an arbitrary point in time.
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  • 36
    Digitale Medien
    Digitale Medien
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    Queueing systems 11 (1992), S. 7-33 
    ISSN: 1572-9443
    Schlagwort(e): Token passing rings ; stability ; substability ; ergodicity ; Markov chains ; Loynes' scheme ; stochastically dominant ; Little's formula ; regenerative processes
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract A sufficient stability condition for the standard token passing ring has been “known” since the seminal paper by Kuehn in 1979. However, this condition was derived without formal proof, and the proof seems to be of considerable interest to the research community. In fact, Watson observed that in the performance evaluation of token passing rings, “it is convenient to derive stability conditions ... (without proof)”. Our intention is to fill this gap, and to provide a formal proof of thesufficient and necessary stability condition for the token passing ring. In this paper, we present the case when the arrival process to each queue is Poisson but service times and switchover times are generally distributed. We consider in depth a gatedl-limited (l≤ ∞) service discipline for each station. We also indicate that the basic steps of our technique can be used to study the stability of some other multiqueue systems.
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  • 37
    Digitale Medien
    Digitale Medien
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    Celestial mechanics and dynamical astronomy 59 (1994), S. 345-374 
    ISSN: 1572-9478
    Schlagwort(e): Lagrangian points ; stability ; oblate primary
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The non-linear stability of the libration pointL 4 in the restricted problem has been studied when there are perturbations in the potentials between the bodies. It is seen that the pointL 4 is stable for all mass ratios in the range of linear stability except for three mass ratios depending upon the perturbing functions. The theory is applied to the following four cases: (i) There are no perturbations in the potentials (classical problem). (ii) Only the bigger primary is an oblate spheroid whose axis of symmetry is perpendicular to the plane of relative motion (circular) of the primaries. (iii) Both the primaries are oblate spheroids whose axes of symmetry are perpendicular to the plane of relative motion (circular) of the primaries. (iv) The primaries are spherical in shape and the bigger is a source of radiation.
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  • 38
    Digitale Medien
    Digitale Medien
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    Journal of dynamics and differential equations 5 (1993), S. 189-218 
    ISSN: 1572-9222
    Schlagwort(e): Equivariant bifurcation ; symmetry ; singularity ; equivariant jets and transversality ; normal forms ; universal unfolding ; stability ; structural stability ; 58F14 ; 58E07 ; 58C27
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract The theoretical machinery from singularity theory introduced by Golubitsky, Stewart, and Schaeffer, to study equivariant bifurcation problems, is completed and expanded while generalized to the multiple parameter context. In this setting the finite determinacy theorems or normal forms, the stability of equivariant bifurcation problems, and the structural stability of the universal unfolding are discussed.
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  • 39
    Digitale Medien
    Digitale Medien
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    Journal of dynamics and differential equations 6 (1994), S. 447-486 
    ISSN: 1572-9222
    Schlagwort(e): Free boundary problems ; gasless combustion ; stability ; Hopf bifurcation ; 35R35 ; 35B40 ; 80A25
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract In this paper, we analyze a simple free boundary model associated with solid combustion and some phase transition processes. There is strong evidence that this “one-phase” model captures all major features of dynamical behavior of more realistic (and complicated) combustion and phase transition models. The principal results concern the dynamical behavior of the model as a bifurcation parameter (which is related to the activation energy in the case of combustion) varies. We prove that the basic uniform front propagation is asymptotically stable against perturbations for the bifurcation parameter above the instability threshold and that a Hopf bifurcation takes place at the threshold value. Results of numerical simulations are presented which confirm that both supercritical and subcritical Hofp bifurcation may occur for physically reasonable nonlinear kinetic functions.
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  • 40
    Digitale Medien
    Digitale Medien
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    Set-valued analysis 1 (1993), S. 393-402 
    ISSN: 1572-932X
    Schlagwort(e): Primary: 49J40, 65K10, 47A55, 47H05, 65L20 ; Variational inequality ; perturbation ; unbounded and nonsmooth operators ; convex sets ; Hausdorff distance ; regularization ; monotonicity ; convergence ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract The stability and convergence of the solutions of perturbed and regularized variational inequality to the solutions of the primary (unstable a priori) variational inequality with proper monotone operator are investigated. All the objects of inequality: the operatorA, the right-hand partf and the set of constrains Ω are to be perturbed. At the same time no assumptions of boundedness and smoothness of the operatorA are used. The connection between the parameters of perturbations, which guarantees strong convergence of approximate solutions, is established. It is proved that the existence of the solution to the unperturbed variational inequality is necessary and sufficient condition for convergence of the regularized perturbed inequality solutions.
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  • 41
    Digitale Medien
    Digitale Medien
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    Queueing systems 6 (1990), S. 335-351 
    ISSN: 1572-9443
    Schlagwort(e): State-dependent service and interarrival times ; Lindley equation ; recursive stochastic equations ; stability ; stochastic comparisons ; normal approximations ; scheduling arrivals
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik
    Notizen: Abstract We consider a modification of the standardG/G/1 queue with unlimited waiting space and the first-in first-out discipline in which the service times and interarrival times depend linearly and randomly on the waiting times. In this model the waiting times satisfy a modified version of the classical Lindley recursion. We determine when the waiting-time distributions converge to a proper limit and we develop approximations for this steady-state limit, primarily by applying previous results of Vervaat [21] and Brandt [4] for the unrestricted recursionY n+1=C n Y n +X n . Particularly appealing for applications is a normal approximation for the stationary waiting time distribution in the case when the queue only rarely becomes empty. We also consider the problem of scheduling successive interarrival times at arrival epochs, with the objective of achieving nearly maximal throughput with nearly bounded waiting times, while making the interarrival time sequence relatively smooth. We identify policies depending linearly and deterministically upon the work in the system which meet these objectives reasonably well; with these policies the waiting times are approximately contained in a specified interval a specified fraction of time.
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  • 42
    Digitale Medien
    Digitale Medien
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    Journal of dynamics and differential equations 4 (1992), S. 161-190 
    ISSN: 1572-9222
    Schlagwort(e): Delay differential equations ; equilibrium ; stability ; limiting equations ; population dynamics ; 34K20 ; 34K25 ; 92A15
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Applying an analytical method and several limiting equations arguments, some sufficient conditions are provided for the existence of a unique positive equilibriumK for the delay differential equationx=−γx+D(x t ), which is the general form of many population models. The results are concerned with the global attractivity, uniform stability, and uniform asymptotic stability ofK. Application of the results to some known population models, which shows the effectiveness of the methods applied here, is also presented.
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  • 43
    Digitale Medien
    Digitale Medien
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    Journal of dynamics and differential equations 5 (1993), S. 105-128 
    ISSN: 1572-9222
    Schlagwort(e): Delay system ; stability ; relative variance ; dynamical disease
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A new approach to the study of delay systems, applicable to physiological control systems and other systems where little information about the time delays is available, is examined. The method is based on the fact that stability information can be deduced from the statistical properties of the probability distribution that encodes the structure of the time delay. The main statistical variables used are the usual expectation parameter,E, and a modified variance, calledrelative variance and denotedR, that is invariant under time scale changes. Recent work of the author has shown that stability often improves asR increases whileE remains fixed. A four-parameter family of delay models is analysed in this paper, and the (E, R) pair is found to be a reliable indicator of stability over the global parameter domain of the family.
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  • 44
    Digitale Medien
    Digitale Medien
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    Journal of dynamics and differential equations 6 (1994), S. 325-334 
    ISSN: 1572-9222
    Schlagwort(e): Nonlinear Schrödinger equations ; anisotropic standing waves ; stability ; concentration compactness principle ; Davey-Stewartson system ; 35Q35 ; 35B35
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We study the stability of standing waves for a nonlinear Schrödinger equation, which derives from the generalized Davey-Stewartson system in the elliptic-elliptic case. We prove the existence of stable standing waves under certain conditions.
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  • 45
    Digitale Medien
    Digitale Medien
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    Journal of dynamics and differential equations 6 (1994), S. 631-637 
    ISSN: 1572-9222
    Schlagwort(e): stability ; fixed point index ; periodic solutions
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract In this paper, we prove that a stable isolated fixed point of an orientation preserving local homeomorphism onR 2 has fixed point index 1. We also give a number of applications to differential equations. In particular, we deduce that a number of existence methods for producing periodic solutions of differential equations in the plane always produce unstable solutions.
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  • 46
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    Digitale Medien
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    Journal of solution chemistry 22 (1993), S. 1151-1158 
    ISSN: 1572-8927
    Schlagwort(e): Molecular complexes ; solvent effect ; stability ; solid CT complexes ; nicotine
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Interaction of nicotine with tetracyanoethylene and iodine was investigated spectrophotometrically and found to form strong CT complexes (n−π and n-σ*, respectively). The donor site involved in CT interaction is the pyrrolidine nitrogen. The nicotine-I2 complex exists as the ionic structure (nicotine) I+-I 3 − . Formation constants of the CT complexes in various solvents were determined from 10 to 25°C and are discussed in terms of the nature of the electron acceptor and solvent polarity. Solid CT complexes were synthesized and were characterized by microchemical analysis and infrared spectra techniques.
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  • 47
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    Acta applicandae mathematicae 28 (1992), S. 1-42 
    ISSN: 1572-9036
    Schlagwort(e): 35R30 ; Inverse scattering ; stability ; noisy data
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract An algorithm is given for calculating the solution to the 3D inverse scattering problem with noisy discrete fixed energy data. The error estimates for the calculated solution are derived. The methods developed are of a general nature and can be used in many applications: in nondestructive evaluation and remote sensing, in geophysical exploration, medical diagnostics, and technology.
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  • 48
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    Digitale Medien
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    Annals of global analysis and geometry 11 (1993), S. 387-395 
    ISSN: 1572-9060
    Schlagwort(e): Curvatures of hypersurfaces ; Reilly's inequality ; stability ; 53 A 10 ; 53 C 42
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We generalize Reilly's inequality for the first eigenvalue of immersed submanifolds ofIR m +1 and the total (squared) mean curvature, to hypersurfaces ofIR m +1 and the first eigenvalue of the higher order curvatures. We apply this to stability problems. We also consider hypersurfaces in hyperbolic space.
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  • 49
    Digitale Medien
    Digitale Medien
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    BIT 33 (1993), S. 332-350 
    ISSN: 1572-9125
    Schlagwort(e): AMS(MOS): 65L06 ; Multistep collocation method ; continuous solution ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract This paper describes an implementation of multistep collocation methods, which are applicable to stiff differential problems, singular perturbation problems, and D.A.E.s of index 1 and 2. These methods generalize one-step implicit Runge-Kutta methods as well as multistep one-stage BDF methods. We give numerical comparisons of our code with two representative codes for these methods, RADAU5 and LSODE.
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  • 50
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    Digitale Medien
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    Entomologia experimentalis et applicata 59 (1991), S. 79-85 
    ISSN: 1570-7458
    Schlagwort(e): Wheat ; Triticum aestivum ; cereals ; Rhopalosiphum padi ; Aphididae ; barley yellow dwarf virus ; hydroxamic acids ; DIMBOA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract 2,4-Dihydroxy-7-methoxy-1,4-benzoxazin-3-one (DIMBOA), a hydroxamic acid (Hx) occurring in wheat, was shown to deter feeding by the aphid Rhopalosiphum padi (L.), and to reduce BYDV transmission to the plant. Dual choice tests with wheat leaves showed the preferential settlement of aphids on leaves with lower levels of DIMBOA. Electric monitoring of aphid feeding behaviour showed that in seedlings with higher DIMBOA levels fewer aphids reached the phloem and they needed longer times to contact a phloem vessel than in those with lower levels. When aphids carrying BYDV were allowed to feed on wheat cultivars with different DIMBOA levels, fewer plants were infected with BYDV in the higher DIMBOA cultivars than in the lower ones. Preliminary field experiments showed a tendency for wheat cultivars with higher Hx levels to be more tolerant to infection by BYDV than lower Hx level ones.
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  • 51
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    Annals of global analysis and geometry 11 (1993), S. 221-235 
    ISSN: 1572-9060
    Schlagwort(e): Second variation formula ; Morse index ; stability ; 53C
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract Iff is a minimal, isometric immersion of the Riemannian manifoldM of dimensionn in a Riemannian manifold $$\overline M$$ of dimensionm and ifI N is the „differential Jacobi operator” acting on the cross sections of the normal bundleN(M), we obtain some information on the Morse index and on the stability ofM through a detailed geometric analysis of the immersionf obtained when considering the higher fundamental forms off.
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  • 52
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    Digitale Medien
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    BIT 30 (1990), S. 332-346 
    ISSN: 1572-9125
    Schlagwort(e): 65D05 ; polynomial interpolaton ; Newton form ; stability ; Leja points ; ordering of interpolation points
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract The Newton form is a convenient representation for interpolation polynomials. Its sensitivity to perturbations depends on the distribution and ordering of the interpolation points. The present paper bounds the growth of the condition number of the Newton form when the interpolation points are Leja points for fairly general compact sets K in the complex plane. Because the Leja points are defined recursively, they are attractive to use with the Newton form. If K is an interval, then the Leja points are distributed roughly like Chebyshev points. Our investigation of the Newton form defined by interpolation at Leja points suggests an ordering scheme for arbitrary interpolation points.
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  • 53
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    BIT 32 (1992), S. 634-649 
    ISSN: 1572-9125
    Schlagwort(e): AMS(MOS): 65L20 ; CR: 5.17 ; delay differential equations ; numerical solution ; Runge-Kutta methods ; interpolation procedures ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract This paper deals with adapting Runge-Kutta methods to differential equations with a lagging argument. A new interpolation procedure is introduced which leads to numerical processes that satisfy an important asymptotic stability condition related to the class of testproblemsU′(t)=λU(t)+μU(t−τ) with λ, μ ε C, Re(λ)〈−|μ|, and τ〉0. Ifc i denotes theith abscissa of a given Runge-Kutta method, then in thenth stept n−1→t n :=t n−1+h of the numerical process our interpolation procedure computes an approximation toU(t n−1+c i h−τ) from approximations that have already been generated by the process at pointst j−1+c i h(j=1,2,3,...). For two of these new processes and a standard process we shall consider the convergence behaviour in an actual application to a given, stiff problem.
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  • 54
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    Celestial mechanics and dynamical astronomy 49 (1990), S. 219-231 
    ISSN: 1572-9478
    Schlagwort(e): n-body problem ; stability ; relative equilibrium
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Beschreibung / Inhaltsverzeichnis: Abstract We prove in this paper the instability, for all n ⩾ 4, of the configurations of relative equilibrium in the n-body problem where the n bodies submitted to newtonian mutual attractions are at the vertices of a regular polypon with n sides. For this proof we show that the equations of variations projected to the n bodies plan P have at least two conjugate characteristic exponents with a strictly positive real part; while these equations projected to an orthogonal axis to P have some solutions with secular terms.
    Notizen: Resumé On démontre dans cet article l'instabilité, pour tout n ⩾ 4, des configurations d'équilibre relatif dans le problème des n corps, oú les n corps soumises aux attractions newtonniennes mutuelles se trouvent aux sommets d'un polygone régulier de n cotés. La preuve consiste à montrer que les équations aux variations, projetées sur le plan P des n corps, possèdent au moins deux exposants caractéristiques complexes connugués dont la parr'e réelle est strictement positive; alors que ces equations projetées sur un axe orthogonal à P possèdent des solutions ayant des termes séculaires.
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  • 55
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    Celestial mechanics and dynamical astronomy 53 (1992), S. 145-150 
    ISSN: 1572-9478
    Schlagwort(e): Monodromy matrix ; Gauss hypergeometric equation ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract A new class of linear ordinary differential equations with periodic coefficients is found which can be transformed to the Gauss hypergeometric equation, and therefore the monodromy matrices are computable explicitly. These equations appear as the variational equations around a straight-line solution in Hamiltonian systems of the form H = T(p) + V(q), where T(p) and V(q) are homogeneous functions of p and q, respectively.
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  • 56
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    Celestial mechanics and dynamical astronomy 56 (1993), S. 323-324 
    ISSN: 1572-9478
    Schlagwort(e): chaos ; stability ; asteroids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Materialart: Digitale Medien
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  • 57
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    Celestial mechanics and dynamical astronomy 57 (1993), S. 59-94 
    ISSN: 1572-9478
    Schlagwort(e): asteroids ; libration ; proper elements ; stability ; chaos ; families
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract I have computed proper elements for 174 asteroids in the 1 : 1 resonance with Jupiter, that is for all the reliable orbits available (numbered and multi-opposition). The procedure requires numerical integration, under the perturbations by the four major planets, for 1,000,000 years; the output is digitally filtered and compressed into a “synthetic theory” (as defined within theLONGSTOP project). The proper modes of oscillation of the variables related to eccentricity, perihelion, inclination and node define proper elements. A third proper element is defined as the amplitude of the oscillation of the semimajor axis associated with the libration period; because of the strong nonlinearity of the problem, this component cannot be determined by a simple Fourier transform to the frequency domain. I therefore give another definition, which results in very good stability with time. For 87% of the computed orbits, the stability of the proper elements-at least over 1M yr-is within the following bounds: 0.001AU in semimajor axis, 0.0025 in eccentricity and sine of inclination. Half of the cases with degraded stability of the proper elements are found to be chaotic, with e-folding times between 16,000 and 660,000yr; in some other cases, chaotic behaviour does not result in a significantly decreased stability of the proper elements (stable chaos). The accuracy and stability of these proper elements is good enough to allow a search for asteroid families; however, the dynamical structure of the Trojan belt is very different from the one of the main belt, and collisional events among Trojans can result in a distribution of fragments difficult to identify. The occurrence of couples of Trojans with very close proper elements is proven not to be statistically significant in almost all cases. As the only exception, the couple 1583 Antilochus — 3801 Thrasimedes is significant; however, it is not easy to account for it by a conventional collisional theory. The Menelaus group is confirmed as a strong candidate collisional family; Teucer and Sarpedon could be considered as significant clusters. A number of other clumps are detected (by the same automated clustering method used for the main belt by Zappalà et al., 1990, 1992), but the total number of Trojans with reliable orbits is not large enough to detect many significant candidate families.
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  • 58
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    Celestial mechanics and dynamical astronomy 49 (1990), S. 249-264 
    ISSN: 1572-9478
    Schlagwort(e): Solar sails ; radiation pressure ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The form of the solar radiation pressure on a heliocentric orbiting solar sail is obtained for a finite angular sized and limb darkened solar disk by the use of the radiation pressure tensor. It is found that the usual inverse square variation of the solar radiation pressure is modified by the finite angular size, and to a lesser extent by the solar limb darkening. The actual magnitude of the modification is in itself small, except at close heliocentric distances. However, its existence has implications for the dynamical stability of solar sails both in parked and circular orbital configurations and for the accuracy of trajectory calculations, particularly for sails in the inner solar system.
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  • 59
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    Celestial mechanics and dynamical astronomy 60 (1994), S. 307-315 
    ISSN: 1572-9478
    Schlagwort(e): Asteroid ; libration ; resonance ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract It is known that an abridged case of the averaged planar general three-body problem, at first-order resonance, is analytically integrated, using an expansion of the disturbing function linear in the eccentricities. There exist different methods with the help of which the integration can be performed. For the first time Sessin and Ferraz-Mello in the years 1981–88 (Sessin, 1981, 1983; Ferraz-Mello and Sessin, 1984; Ferraz-Mello, 1987, 1988) did an analytic integration for the restricted elliptic three-body problem, in terms of the variablesK andH (K=ΣD j e j cos (ψ1−π j ),H=ΣD j e j sin (ψ1−π j ),D j = const, wheree j and π j are, respectively, the eccentricity and the longitude of the periapsis of thei-th planet, ψ1 is the Delaunay's anomaly), which is inconvenient for the analytical investigation of the evolution of the major semi-axesa j , the eccentricitiese j and the resonance phases ϕ j =ψ1−π j . Later, a different method for the analytical integration of the general three-body problem, in the variablesa j ,e j and ϕ j , was considered by the author (Shinkin, 1993). A disadvantage of both methods is the fact that they use non-canonical changes of variables. But there exists a third very beautiful canonical method of analytical integration of the general planetary problem, which is briefly considered in the present paper and allows us to describe the bifurcations of separatrices (i.e. appearance, disappearance, splitting and confluence of separatrices) separating the domains of libration and circulation of the resonance phase on the phase plane in the averaged planar general three-body problem at first-order resonance. The bifurcation parameter is analytically found and plays an important role in a qualitative description of all kinds of motion in the examined problem.
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  • 60
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    Acta applicandae mathematicae 37 (1994), S. 129-136 
    ISSN: 1572-9036
    Schlagwort(e): 35B35 ; 35Q30 ; 76N10 ; stability ; Navier-Stokes equations ; compressible fluids
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We prove that the uniform stability at permanently acting disturbances of a given solution of the Navier-Stokes equations for viscous compressible isothermic fluid is a consequence of the uniform exponential stability of the zero solution of so-called linearized equations.
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  • 61
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    Celestial mechanics and dynamical astronomy 53 (1992), S. 219-226 
    ISSN: 1572-9478
    Schlagwort(e): Artificial satellite ; dissipative forces ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The effects of small external dissipative and disturbing forces on the non-linear planar oscillation of a cable connected satellites system in the central gravitational field of earth have been studied. Typical non-linear oscillation's phenomena arizing from the aforesaid external forces are shown to take place. The presence of these forces enables the application of asymptotic methods of the theory of non-linear oscillations due to Bogoliubov and Mitropolsky to the equation characterizing the non-linear oscillation of the system.
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  • 62
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    Celestial mechanics and dynamical astronomy 60 (1994), S. 249-271 
    ISSN: 1572-9478
    Schlagwort(e): Chaos ; periodic orbits ; stability ; asymptotic curves ; homoclinic points ; heteroclinic points
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract We study the structure of chaos in a simple Hamiltonian system that does no have an escape energy. This system has 5 main periodic orbits that are represented on the surface of section $$(y,\dot y)$$ by the points (1)O(0,0), (2)C 1,C 2(±y c, 0), (3)B 1,B 2(O,±1) and (4) the boundary $$y^2 + \dot y^2 = 1$$ . The periodic orbits (1) and (4) have infinite transitions from stability (S) to instability (U) and vice-versa; the transition values of ε are given by simple approximate formulae. At every transitionS →U a set of 4 asymptotic curves is formed atO. For larger ε the size and the oscillations of these curves grow until they destroy the closed invariant curves that surroundO, and they intersect the asymptotic curves of the orbitsC 1,C 2 at infinite heteroclinic points. At every transitionU →S these asymptotic curves are duplicated and they start at two unstable invariant points bifurcating fromO. At the transition itself the asymptotic curves fromO are tangent to each other. The areas of the lobes fromO increase with ε; these lobes increase even afterO becomes stable again. The asymptotic curves of the unstable periodic orbits follow certain rules. Whenever there are heteroclinic points the asymptotic curves of one unstable orbit approach the asymptotic curves of another unstable orbit in a definite way. Finally we study the tangencies and the spirals formed by the asymptotic curves of the orbitsB 1,B 2. We find indications that the number of spiral rotations tends to infinity as ε → ∞. Therefore new tangencies between the asymptotic curves appear for arbitrarily large ε. As a consequence there are infinite new families of stable periodic orbits that appear for arbitrarily large ε.
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  • 63
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    Celestial mechanics and dynamical astronomy 55 (1993), S. 249-259 
    ISSN: 1572-9478
    Schlagwort(e): Asteroid ; libration ; resonance ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract This paper investigates the stability of the motion in the averaged planar general three-body problem in the case of first-order resonance. The equations of the averaged motion of bodies near the resonance surface is obtained and is analytically integrated by quadratures. The stability of the averaged motion is analytically investigated in relation to the semi-major axes, the eccentricities and the resonance phases. An autonomous second-order equation is obtained for the deviation of semiaxes from the resonance surface. This equation has an energy integral and is analytically integrated by quadratures. The quasi-periodic dependence on time with two-frequency basis of the averaged motion of bodies is found. The basic frequencies are analytically calculated. With the help of the mean functionals calculated along integral curves of the averaged problem the new analytic first integrals are constructed with coefficients periodic in time. The analytic conditions of librations of resonance phases are obtained.
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  • 64
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    Celestial mechanics and dynamical astronomy 55 (1993), S. 323-330 
    ISSN: 1572-9478
    Schlagwort(e): Periodic orbits ; rigid body dynamics ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The equations of motion of a rigid body about a fixed point in a central Newtonian field is reduced to the equation of plane motion under the action of potential and gyroscopic forces, using the isothermal coordinates on the inertia ellipsoid. The construction of periodic solutions near the equilibrium points, by using the Lipaunov theorem of holomorphic integral, is obtained and the necessary and sufficient conditions for the stability of the system are given.
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  • 65
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    Celestial mechanics and dynamical astronomy 55 (1993), S. 351-367 
    ISSN: 1572-9478
    Schlagwort(e): Sitnikov's problem ; invariant rotational curves ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract The Sitnikov's Problem is a Restricted Three-Body Problem of Celestial Mechanics depending on a parameter, the eccentricity,e. The Hamiltonian,H(z, v, t, e), does not depend ont ife=0 and we have an integrable system; ife is small the KAM Theory proves the existence of invariant rotational curves, IRC. For larger eccentricities, we show that there exist two complementary sequences of intervals of values ofe that accumulate to the maximum admissible value of the eccentricity, 1, and such that, for one of the sequences IRC around a fixed point persist. Moreover, they shrink to the planez=0 ase tends to 1.
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  • 66
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    Celestial mechanics and dynamical astronomy 60 (1994), S. 99-129 
    ISSN: 1572-9478
    Schlagwort(e): Sitnikov motions ; periodic orbits ; stability ; bifurcations
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Physik
    Notizen: Abstract In this paper we deal with the circular Sitnikov problem as a subsystem of the three-dimensional circular restricted three-body problem. It has a first analytical part where by using elliptic functions we give the analytical expressions for the solutions of the circular Sitnikov problem and for the period function of its family of periodic orbits. We also analyze the qualitative and quantitative behavior of the period function. In the second numerical part, we study the linear stability of the family of periodic orbits of the Sitnikov problem, and of the families of periodic orbits of the three-dimensional circular restricted three-body problem which bifurcate from them; and we follow these bifurcated families until they end in families of periodic orbits of the planar circular restricted three-body problem. We compare our results with the previous ones of other authors on this problem. Finally, the characteristic curves of some bifurcated families obtained for the mass parameter close to 1/2 are also described.
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  • 67
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    BIT 33 (1993), S. 74-84 
    ISSN: 1572-9125
    Schlagwort(e): 65J10 ; 65M12 ; Analytic semigroup ; Banach space ; rational approximation ; A-acceptable ; A(θ)-acceptable ; stability ; Crank-Nicolson method
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract It is shown thatA-acceptable and, more generally,A(θ)-arational approximations of bounded analytic semigroups in Banach space are stable. The result applies, in particular, to the Crank-Nicolson method.
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  • 68
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    BIT 33 (1993), S. 285-303 
    ISSN: 1572-9125
    Schlagwort(e): 65L05 ; stiffness ; stability ; pseudospectra
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract It is argued that even for a linear system of ODEs with constant coefficients, stiffness cannot properly be characterized in terms of the eigenvalues of the Jacobian, because stiffness is a transient phenomenon whereas the significance of eigenvalues is asymptotic. Recent theory from the numerical solution of PDEs is adapted to show that a more appropriate characterization can be based upon pseudospectra instead of spectra. Numerical experiments with an adaptive ODE solver illustrate these findings.
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  • 69
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    BIT 34 (1994), S. 62-79 
    ISSN: 1572-9125
    Schlagwort(e): AMS(MOS) 65D30 ; 65B05 ; adaptive ; cubature ; singularity ; extrapolation ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A new approach to the integration of vertex singularities is described. This approach is based on a non-uniform subdivision of the region of integration and the technique fits well to the subdivision strategy used in many adaptive algorithms. A nice feature with this approach is that it can be used in any dimension and on any region of integration which can be subdivided into subregions of the same form. The strategy can be applied both to vertex singularities and internal point singularities. In the latter case this can be done without an initial subdivision of the region in order to put the singular point in a vertex. It turns out that the technique has excellent numerical stability properties.
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  • 70
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    Aquatic sciences 52 (1990), S. 330-344 
    ISSN: 1420-9055
    Schlagwort(e): Flood ; phytoplankton succession ; reversion ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The effect of the August 1987 River Reuss flood event on the phytoplankton biocoenosis in Lake Uri (Urnersee, part of Lake Lucerne, Switzerland) was investigated firstly by comparing biological, chemical and physical data sampled before the event with equivalent data sampled after the event; and secondly by comparing the phytoplankton succession in 1987 with that occurring in the “floodfree” year 1989. As a consequence of the flood, the physical and chemical environment of the phytoplankton was found to have undergone a change which resulted in an alteration in the composition of the phytoplankton community. The phytoplankton community existing previous to the flood event, which had been dominated byTabellaria fenestrata sensu Husted 1930 (K-strategist), was replaced by a biocoenosis characterized mainly by various species of flagellates, which represent a typical spring successional stage (r-strategists). After the externally-imposed perturbation, the return to stable physical and chemical conditions was followed by the re-establishment of the successional stage which had existed before the flood (termed “reversion” by Reynolds, 1980).
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  • 71
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    Aquatic sciences 53 (1991), S. 263-272 
    ISSN: 1420-9055
    Schlagwort(e): Lake ecosystem ; chl-a ; phosphorus ; nitrogen ; river flow ; thermocline ; simulation model ; multiple regression
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract The management variables which primarily affect phytoplankton biomass (as chl-a) in Lake Mjøsa, Norway, are total phosphorus loading (TP) and the timing and volume of water through flow (by active storage reservoirs). The response of the lake to changes in these factors is studied using a simulation model of the lake ecosystem. Chl-a responses from both observed data and the simulated results are extracted by multiple regression. Results show that decreasing TP load decreases chl-a, but less at low TP levels (〈 10 mg TP · m−3). There is also a certain time period for peak river flow which gives the least yield of chl-a per unit TP. This time period occurs in early summer (i.e., around June 10) if the total phosphorus load is low, and later if the load is high. Both observations and simulation results show that a high water flow increases chl-a at low epilimnion depths (〈 15 m), but that the same high water flow decreases chl-a when epilmnion is deep.
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  • 72
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    Catalysis letters 28 (1994), S. 25-31 
    ISSN: 1572-879X
    Schlagwort(e): vanadia/alumina ; stability ; NO x selective reduction
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Changes of the V2O5/Al3O3 catalyst aged for up to 10 years under real conditions of the selective catalytic reduction of NO x by ammonia (SCR) at the tail gases of the nitric acid plant were characterized by51V NMR spectroscopy, porosimetry, temperature programmed reduction (TPR) and catalytic activity measurements. The catalytic activity and the redox properties of the catalyst were found intact. Only small variations of the ratio of the octahedral and tetrahedral vanadia species were documented by51V NMR on aged catalyst.
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  • 73
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    Entomologia experimentalis et applicata 62 (1992), S. 29-36 
    ISSN: 1570-7458
    Schlagwort(e): Alkaloids ; cinnabar moth ; insect genetics ; larval performance ; Lepidoptera ; nutritional ecology ; nitrogen ; sugar ; Tyria jacobaeae
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Abstract In a laboratory experiment using full-sibs, 60% of the variation in pupal weight of the monophage Tyria jacobaeae L. (Lepidoptera, Arctiidae) could be explained by variation in the nitrogen concentration of the food plant, Senecio jacobaea L. and only 4% by variation in sugar concentration. Larval weight and growth rates of young and old larvae were also positively correlated with nitrogen and sugar concentration. Developmental time was negatively correlated with nitrogen concentration. In a second experiment full-sib families differed significantly in larval weight at day 7, mortality, growth rate and developmental time. Pupal weight did not differ significantly among families, but was positively correlated with nitrogen concentration of Senecio. Larval performance was not significantly influenced by concentrations of sugars or alkaloids. We conclude that larval performance of Tyria during most of the larval period is mainly determined by genetic factors, but pupal weights are primarily determined by nitrogen concentration of the food plant.
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  • 74
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    Biology and fertility of soils 9 (1990), S. 281-282 
    ISSN: 1432-0789
    Schlagwort(e): Surface sterilization ; Contaminants ; Sterile plant selection ; Axenic seedlings ; Triticum aestivum ; Trifolium pratense ; Trifolium repens
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie , Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Summary Sterile seedlings are required for the investigation of interactions between microorganisms and plants. The present study was designed to develop a simple and reliable method for the selection of sterile seedlings by the use of liquid nutrient media, avoiding some of the disadvantages of solid media. The method of germinating surface-sterilized seedlings on solid water agar or nutrient media was compared with our method for sterility control in nutrient broth. Sterile plant selection in liquid media was the most sensitive method for detecting bacterial and fungal contaminants. Sterile plants grow with the same vigour as unsterilized plants and can be used for sterile plant experiments.
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  • 75
    ISSN: 1432-0983
    Schlagwort(e): Secale cereale ; Triticum aestivum ; Ribosomal RNA genes ; Mitochondrial DNA
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The mitochondrial 18S and 5S ribosomal RNA (rRNA) genes of rye, plus a total of about 90 kilobase pairs of flanking DNA, have been cloned and maps of restriction enzyme cleavage sites have been constructed. Like their homologs from hexaploid wheat, the rye genes are closely linked and are part of a three-copy family of recombining repeats (the “18S/5S repeat”). The rye repeat probably also contains a mitochondrial tRNAfMet gene, which the wheat repeat is known to carry. However, despite the overall organizational similarity between the wheat and rye 18S/5S repeats in the immediate vicinity of their coding regions, extensive rearrangement of flanking sequences has taken place during evolutionary divergence of the two species. Our data provide additional support for an emerging picture of plant mitochondrial genomes as evolving much more rapidly in structure than in sequence.
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  • 76
    ISSN: 1432-0983
    Schlagwort(e): Light regulation ; psbN ; Triticum aestivum ; Etioplast
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary The nucleotide sequence of a region of wheat chloroplast DNA containing the psbB gene for the 47 kDa chlorophyll a-binding protein of photosystem II has been determined. The gene encodes a polypeptide of 508 amino acid residues which is predicted to contain six hydrophobic membrane-spanning regions. The psbB gene is located 562 bp upstream of the psbH gene for the 10 kDa phosphoprotein of photosystem II. A small open reading frame of 38 codons is located between psbB and psbH, and on the opposite strand the psbN gene, encoding a photosystem II polypeptide of 43 amino acid residues, is located between orf38 and psbH. S1 nuclease mapping indicated that the 5′ ends of transcripts were located 371 and 183 bp upstream of the psbB translation initiation codon. Predominant transcripts of 2.1 kb and 1.8 kb for psbB and 0.4 kb for psbH were present in RNA isolated from etiolated and greening wheat seedlings. Immunodecoration of Western blots indicated that the 47 kDa polypeptide was absent, or present in very low amounts, in dark-grown tissue and accumulated on greening, whereas the 10 kDa polypeptide was present in similar amounts in both dark-grown and greening seedlings. The 10 kDa polypeptide was phosphorylated in vitro by incubating wheat etioplast membranes with [γ3 2P] ATP.
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  • 77
    ISSN: 1432-0983
    Schlagwort(e): Triticum aestivum ; Mitochondrial DNA ; Chloroplast DNA ; ATPase alpha subunit
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie
    Notizen: Summary An internal part of the chloroplast atpA gene has been identified in the mitochondrial DNA of Triticum aestivum. It is located near the 18S-5S ribosomal genes and partially contained within a repeated sequence. Comparison of the transferred sequence with the original ct sequence reveals several nucleotide changes and shows that neither 5′ nor 3′ ends are present in the mt genome. No transcript of this region could be detected by Northern analysis. This sequence is present in mitochondrial genomes of other tetraploid and diploid species of Triticum, also in the vicinity of the 18S-5S ribosomal genes, suggesting a unique transfer event. The date of this event is discussed.
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  • 78
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    OR spectrum 15 (1994), S. 197-203 
    ISSN: 1436-6304
    Schlagwort(e): Inventory ; dynamic programming ; stability ; Lagerhaltung ; Dynamische Optimierung ; Stabilität
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik , Wirtschaftswissenschaften
    Beschreibung / Inhaltsverzeichnis: Zusammenfassung Die Menge der Kostenparameter, für die eine optimale Lösung des dynamischen Losgrößenmodells optimal bleibt wird hier Stabilitätsregion genannt. Die Größe einer solchen Menge kann als Maß der Robustheit einer Lösung angesehen werden. Es ist zu erwarten, daß die Stabilitätsregionen mit wachsendem Zeithorizont schrumpfen und daß sie in diesem Sinne monoton sind. In der vorliegenden Arbeit werden verschiedene hinreichende Bedingungen für diese Monotonie untersucht. Die Bedingungen setzen unter anderem die Existenz von Planungs- und Vorhersage-Horizonten voraus und verallgemeinern so Ergebnisse einer früheren Arbeit, in der Aussagen für gewöhnliche Planungs-Horizonte vorgestellt wurden.
    Notizen: Abstract The set of cost inputs for which an optimal solution of the dynamic lot size model remains valid is called stability region. The size of this region may be viewed as a measure of robustness of a solution. It is an expectation that the stability regions shrink with growing time horizons and that they are monotonous in this sense. In the present paper several sufficient conditions implying monotonicity will be studied. The conditions cover the existence of planning and forecast horizons and generalize the results of a previous paper in wich monotonicity results were presented for the case of ordinary planning horizons.
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  • 79
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    Microchimica acta 104 (1991), S. 467-482 
    ISSN: 1436-5073
    Schlagwort(e): prediction ; stability ; multivariate methods ; graphical analysis
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Chemie und Pharmazie
    Notizen: Abstract Sizeable data bases are now being routinely generated in a variety of contexts in chemical industry. Statistical investigations of such data bases are aimed both at initially uncovering structure and eventually proposing models, in particular for predicting product quality by the mix or characteristics of the chemical compounds. “Online Multivariate Exploratory Graphical Analysis” (OMEGA) stands for a structured exploratory study of the relationships in a multivariate data set, where, rather than testing for one specific property, as many clues as possible for interesting structures are searched for by different dimension reductions and succeeding interactive graphical analyses. The stability of the projections obtained by the different dimension reduction methods is assessed by simulation producing graphical displays particularly supporting the identification of influential points. The variation of the predictions obtained by the different dimension reduction methods is assessed by cross-validation delivering misclassification rates or cross-validated R2 values. The interpretation of the new coordinates corresponding to dimension reduction is supported by loading simplifications and graphical displays for judging its adequacy. The OMEGA strategy has been found to be an effective tool for routine searching for structure.
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  • 80
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    Meccanica 29 (1994), S. 195-210 
    ISSN: 1572-9648
    Schlagwort(e): Chetaev functional ; pendulum ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Maschinenbau , Physik
    Beschreibung / Inhaltsverzeichnis: Sommario Si considera il problema di stabilità di punti di equilibrio di un pendolo fisico con un filo inestensibile appeso ad esso dal punto di vista del teorema di Lagrange sulla stabilità e sulla sua inversione. Difficoltà specifiche relative allo studio di un sistema meccanico di dimensione infinita sono discusse. Si suggerisce un nuovo metodo per lo studio della stabilità rispetto a due metriche. L'influenza di fenomeni di risonanza sul moto del sistema ridotto (linearizzato) è considerata.
    Notizen: Abstract The problem of stability of equilibria of a physical pendulum with a nonstretchable thread attached to it is considered from the standpoint of the Lagrange theorem on stability and its inversion. Specific difficulties which one faces when studying an infinite dimensional mechanical system are discussed. A new approach to the study of stability with respect to two metrics is suggested. The influence of resonant phenomena on the motion of the shortened (linearized) system is considered.
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  • 81
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    Journal of intelligent and robotic systems 3 (1990), S. 259-289 
    ISSN: 1573-0409
    Schlagwort(e): Nonlinear decoupling ; feedback linearization ; functional analysis ; elastic robots ; robustness ; stability ; pole assignment ; nonlinear systems ; robot control
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Maschinenbau
    Notizen: Abstract A robustness analysis and synthesis for incomplete nonlinear decoupling for a class of nonlinear systems is discussed. Rigid and elastic-joint robot models belong to this class. For the elastic case, a transformation facilitates the robustness analysis under a weak assumption. Charts with H 1- and H ∞- norms of closed-loop disturbance transfer functions of the nonlinear-decoupled system are presented for a robust pole assignment.
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  • 82
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    Journal of intelligent and robotic systems 6 (1992), S. 51-63 
    ISSN: 1573-0409
    Schlagwort(e): Scheduling ; flexible manufacturing systems ; stability ; feedback
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Maschinenbau
    Notizen: Abstract A genetic manufacturing environment is considered. The emphasis is on small-lot, discrete, and asynchronous type of manufacturing systems rather than high volume and continuous type. Two classes of scheduling policies are proposed to render the machine stable. The policies are of feedback type. The decision is made in real-time and on-line.
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  • 83
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    Journal of intelligent and robotic systems 6 (1992), S. 219-240 
    ISSN: 1573-0409
    Schlagwort(e): Force control ; slip-stick friction ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Informatik , Maschinenbau
    Notizen: Abstract This paper explores two practical issues related to the force control of manipulators. The first issue examined is how system stability is effected by commonly occurring manipulator nonlinearities, such as sampled-data, control signal saturation and slip-stick friction. It is shown that discretely implemented force control algorithms can drive the feedback force controlled manipulator into a limit cycle, even for a very small sampling period that by far satisfies Shannon's sampling theorem. The bounds of stability are enhanced by the presence of control signal saturation and slip stick friction. The second issue investigated is the inclusion of a high gain inner position loop as a means to minimize the unpredictability in the steady state error due to slip-stick friction. In order to support the theoretical conclusions, experiments were performed with the PUMP 560 industrial robot testbed facility developed at Colorado State University.
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  • 84
    ISSN: 1573-0417
    Schlagwort(e): Great Basin ; climatic variations ; productivity ; organic matter ; nitrogen ; phosphorus ; hardwater lake
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract Sediment cores from the shallow and deep basins of Pyramid Lake, Nevada, revealed variations in composition with depth reflecting changes in lake level, river inflow, and lake productivity. Recent sediments from the period of historical record indicate: (1) CaCO3 and organic content of sediment in the shallow basin decrease at lower lake level, (2) CaCO3 content of deep basin sediments increases when lake level decreases rapidly, and (3) the inorganic P content of sediments increases with decreasing lake volume. Variations in sediment composition also indicate several periods for which productivity in Pyramid Lake may have been elevated over the past 1000 years. Our data provide strong evidence for increased productivity during the first half of the 20th Century, although the typical pattern for cultural eutrophication was not observed. The organic content of sediments also suggests periods of increased productivity in the lake prior to the discovery and development of the region by white settlers. Indeed, a broad peak in organic fractions during the 1800's originates as an increase starting around 1600. However, periods of changing organic content of sediments also correspond to periods when inflow to the lake was probably at extremes (e.g. drought or flood) indicating that fluctuations in river inflow may be an important factor affecting sediment composition in Pyramid Lake.
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  • 85
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    K-Theory 4 (1991), S. 363-397 
    ISSN: 1573-0514
    Schlagwort(e): Nonabelian K 1 ; noncommutative homotopy ; general linear group ; superspecial linear groups ; descending central series ; stability ; relative normal subgroups ; nilpotent sandwich classifications ; quasi-finite algebras
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract A functorial filtration GL n =S−1L n $$ \supseteq$$ S0L n $$ \supseteq$$ ⋯ $$ \supseteq$$ S i L n $$ \supseteq$$ ⋯ $$ \supseteq$$ E n of the general linear group GL n, n ⩾ 3, is defined and it is shown for any algebra A, which is a direct limit of module finite algebras, that S−1 L n (A)/S0L n (A) is abelian, that S0L n (A) $$ \supseteq$$ S1L n (A) $$ \supseteq$$ ⋯ is a descending central series, and that S i L n (A) = E n(A) whenever i ⩾ the Bass-Serre dimension of A. In particular, the K-functors k 1 S i L n =S i L n /E n are nilpotent for all i ⩾ 0 over algebras of finite Bass-Serre dimension. Furthermore, without dimension assumptions, the canonical homomorphism S i L n (A)/S i+1 L n (A)→S i L n+ 1(A)/S i+1 L n + 1 (A) is injective whenever n ⩾ i + 3, so that one has stability results without stability conditions, and if A is commutative then S0L n (A) agrees with the special linear group SL n (A), so that the functor S0L n generalizes the functor SL n to noncommutative rings. Applying the above to subgroups H of GL n (A), which are normalized by E n(A), one obtains that each is contained in a sandwich GL′ n (A, ρ) $$ \supseteq$$ H $$ \supseteq$$ E n(A, ρ) for a unique two-sided ideal ρ of A and there is a descending S0L n (A)-central series GL′ n (A, ρ) $$ \supseteq$$ S0L n (A, ρ) $$ \supseteq$$ S1L n (A, ρ) $$ \supseteq$$ ⋯ $$ \supseteq$$ S i L n (A, ρ) $$ \supseteq$$ ⋯ $$ \supseteq$$ E n(A, ρ) such that S i L n (A, ρ)=E n(A, ρ) whenever i ⩾ Bass-Serre dimension of A.
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  • 86
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    K-Theory 7 (1993), S. 333-367 
    ISSN: 1573-0514
    Schlagwort(e): Locally flat embedding ; pointed Hermitian module ; splitting ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Mathematik
    Notizen: Abstract We prove an existence result for topologically locally flat embeddings of 2-spheres in simply connected 4-manifolds. This topological result is deduced from a splitting theorem for pointed Hermitian modules over a cyclic group ring. A stability result for such modules is also proved. This applies to the isotopy classification of locally flat embeddings.
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  • 87
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    Journal of paleolimnology 4 (1990), S. 1-22 
    ISSN: 1573-0417
    Schlagwort(e): sulfate ; carbon ; nitrogen ; hydrogen ; organic matter ; enrichment factor ; lake sediments ; paleolimnology
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Biologie , Geologie und Paläontologie
    Notizen: Abstract This paper discusses the use of S as a paleolimnological tracer of limnetic sulfate concentration. A positive relationship (p〈0.05) was found between limnetic sulfate and sediment S concentrations for the Great Lakes, English Lakes, and lakes from the Adirondack and Northern New England regions. There is a positive correlation (p〈0.05) between C and S concentration in sediment across all regions studied. The importance of C in affecting S content in sediment was also examined by a series of cores taken at different water depths in Big Moose Lake (Adirondacks). There was a strong relationship between C and S among cores with sediment from deeper water having higher C and S concentrations (r 2=0.99). Sulfur from the shallower cores had greater concentrations of chromium-reducible S (pyrite), while cores from deeper waters had a greater proportion of organic S fractions including C-bonded S and ester sulfates. For assessing historical changes in S accumulation in sediments, enrichment factors were calculated for the PIRLA lakes. Pre-1900 net sediment accumulation rates of S were very similar across all regions. Sulfur enrichment was greatest in Adirondack sediment which had total post-1900 S accumulation of 1.1 to 7.4 times pre-1900 S accumulation. Sediment from Northern New England (NNE) generally had lower S concentration than Adirondack sediments and S enrichment factors ranged from 1.2 to 2.1. Sediment from the Northern Great Lakes States region had similar S concentration and distribution with depth to NNE sediment. In two Northern Florida lakes, sediment showed little variation in S concentration with depth, but in two other lakes from the same region, there was higher S concentration in deeper layers. Lakes which had the greatest enrichment factors also exhibited the most marked changes in C:S ratios. Ratios of C:N showed little variation (10.6 to 26.1) among the PIRLA lakes. A first order model indicated slow decomposition within these organic rich sediments. Elemental concentrations and ratios of sediment from a variety of lakes and reservoirs were complied. Maximum and minimum elemental ratios for all the data were 28 to 8.1 for C:N, 0.81 to 0.11 for C:H, and 675 to 12.5 for C:S, respectively. For the C:S ratios in all regions except the Great Lakes, the maximum ratio was less than 231. Both the maximum and minimum amount of N and H concentration of organic matter is related to biotic processes. The minimum concentration of S is regulated not only by nutrient demands but also by non-assimilatory processes. Sulfur incorporation into sediments is a function of a complex of factors, but limnetic sulfate concentration and organic matter content play a major role in regulating the S content of sediment. Further quantification of S incorporation pathways will aid in the paleolimnological interpretation of sediment S profiles. Such information is also important in assessing how S sediment pools will respond to decreases in limnetic sulfate concentration which may occur with decreases in inputs from acidic deposition.
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  • 88
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    Multidimensional systems and signal processing 3 (1992), S. 421-425 
    ISSN: 1573-0824
    Schlagwort(e): Convex combination ; polynomial ; stability
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Elektrotechnik, Elektronik, Nachrichtentechnik
    Notizen: Abstract A sufficient condition for Hurwitz stability of a convex combination of two stable polynomials is obtained.
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  • 89
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    Nutrient cycling in agroecosystems 38 (1994), S. 53-59 
    ISSN: 1573-0867
    Schlagwort(e): controlled-release fertilizer ; gel ; iron ; manganese ; nitrogen ; polyacrylamide
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Using diverse technological approaches, many types of delivery devices have been used to supply plant nutrients at a controlled rate in the soil. One new approach is the use of hydrophilic polymers as carriers of plant nutrients. These polymers may be generally classified as 1) natural polymers derived from polysaccharides, 2) semi-synthetic polymers (primarily cellulose derivatives), and 3) synthetic polymers. By controlling the reaction conditions when forming the polymers, various degrees of cross-linking, anionic charge, and cationic charge can be added, thereby changing their effectiveness as fertilizer carriers. When fertilizer-containing solutions are mixed with hydrophilic polymers to form a “gel” prior to application in the soil, the release of soluble nutrients can be substantially delayed compared with soluble fertilizer alone. The effectiveness of a specific controlled-release polymeric system is determined in part by its specific chemical and physical properties, its biodegradation rate, and the fertilizer source used. Addition of some polymers with nutrients has been shown to reduce N and K leaching from well-drained soils and to increase the plant recovery of added N, P, Fe, and Mn in some circumstances
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  • 90
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    Nutrient cycling in agroecosystems 27 (1991), S. 189-198 
    ISSN: 1573-0867
    Schlagwort(e): Winter wheat ; nitrogen ; uptake ; simulation ; model ; soil
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Simulation of the nitrogen behavior in the soil and the nitrogen uptake by winter wheat was performed using the model ANIMO. As input for the model ANIMO simulations of the hydrological conditions in the soil crop ecosystem were executed with the model SWATRE. Compared with measured data the simulation of nitrogen uptake by the crop was satisfactory. The simulation of mineral nitrogen in the soil agreed reasonably well with measured data for one of the experiments used for the analysis. The agreement was less for experiments with additional fertilizer applications in May and June.
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  • 91
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    Nutrient cycling in agroecosystems 27 (1991), S. 129-140 
    ISSN: 1573-0867
    Schlagwort(e): Douglas-fir ; nitrogen ; mineral cycling ; growth and yield
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Forest managers in the Pacific Northwest (PNW) use fertilization as a means to increase timber yields in managed stands. Information on the biological basis for nutrient amendments and stand growth responses to fertilization is required to effectively use fertilization as a silvicultural tool, and research programs in mineral cycling and forest nutrition have been underway in the region for about four decades. Most PNW Douglas-fir forest sites are nitrogen deficient. Mineral cycling research has shown high C/N ratios and low nitrification rates for soils in the region. Research and development projects in the Pacific Northwest have produced an information base that is used to select sites and stands for fertilization and to forecast growth after treatment. Much of the basis for operational fertilization programs in western Oregon and Washington comes from cooperative research programs; current activities for these programs are directed toward improving site-specific response information. Forest fertilization in the Pacific Northwest has become a silvicultural practice of major significance over the past two decades. Forest industry and government organizations managing forest lands in western Oregon and Washington apply nitrogen fertilizer to Douglas-fir stands over a range of soil and stand types (operational fertilization of other species is minor). About 50,000 to 55,000 ha are fertilized each year, and future programs will likely be of similar magnitude. Most current plans for management regimes including fertilization call for multiple applications.
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  • 92
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    Nutrient cycling in agroecosystems 40 (1994), S. 165-173 
    ISSN: 1573-0867
    Schlagwort(e): Animal manure ; eutrophication ; ground water ; nitrogen ; phosphorus ; surface runoff
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract With the rapid growth of the poultry industry in Oklahoma, U.S.A., more litter is applied to farm land. Thus, information is required on the impact of applications on regional soil and water resources. The effect of soil and poultry litter management on nitrogen (N) and phosphorus (P) loss in runoff and subsurface flow from four 16 m2 plots (Ruston fine sandy loam, 6 to 8% slope) was investigated under natural rainfall. Plots under Bermudagrass (Cynodon dactylon) received 11 Mg litter ha−1, which amounts to contributions of approximately 410 kg N and 140 kg P ha−1 yr−1. In spring, litter was broadcast on 3 of the plots; the upper half of one and total area of the other two. One of the total-area broadcast plots was tilled to 6 cm, the other remained as no till. The fourth plot served as a control. Relative to the control, litter application increased mean concentrations of total N and total P in runoff during the 16-week study for no-till (15.4 and 5.8 mg L−1) and tilled treatments (16.7 and 6.1 mg L−1). However, values for the half-area application (5.6 and 2.0 mg L−1) were similar to the control (5.7 and 1.3 mg L−1). Interflow (subsurface lateral flow at 70 cm depth) P was not affected by litter application; however, nitrate-N concentrations increased from 0.6 (control) to 2.9 mg L−1 (no till). In all cases, 〈 2 % litter N and P was lost in runoff and interflow, maintaining acceptable water quality concentrations. Although litter increased grass yield (8518 kg ha−1) compared to the control (3501 kg ha−1), yields were not affected by litter management. An 8-fold increase in the plant available P content of surface soil indicates long-term litter management and application rates will be critical to the environmentally sound use of this nutrient resource.
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  • 93
    ISSN: 1573-0867
    Schlagwort(e): Wheat ; nitrogen ; grain protein content ; grain filling ; urea spraying
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract The objective of this work was to determine the effect of foliar urea spraying during or after anthesis, on dry matter and nitrogen accumulation in the wheat grain of two cultivars, differing in grain protein content. The experiment was carried out in the field, and 20 kg N ha−1 as urea (46-0-0) was sprayed at anthesis, 7 or 14 days after anthesis. Dry weight, N content and N percentage of the grain were determined at several stages of its development. Neither the rate nor the duration of dry matter accumulation in the grain was significantly modified by N sprayings at anthesis or later and, consequently, not its final weight. Nitrogen sprayings at anthesis or later increased the grain N content and N percentage at ripeness in both cultivars, but to a greater extent in the low grain protein cultivar. Greater N content in the grain was attributed to a rapid uptake of the N applied and not to a longer duration of the period of N accumulation. The different responses of the cultivars to N sprayings can be related to differences in N demand, and is probably associated, also, to a genetic ability to accumulate N in the grain.
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  • 94
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    Nutrient cycling in agroecosystems 37 (1994), S. 107-113 
    ISSN: 1573-0867
    Schlagwort(e): Ensete ventricosum ; fertilizer response ; nitrogen ; phosphorus ; potassium ; sulphur ; starch
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Ensete (Ensete ventricosum W. Cheesm.) is a root crop which stores starch in the root and in the lower part of the stem. It is grown in the southwest of Ethiopia and due to its drought resistance, it is of outstanding importance for the supply of food to the local population. Until now virtually nothing is known about the response of Ensete to fertilizer application. Field trials carried out on three representative soils in Ethiopia showed that Ensete biomass yields were increased significantly on all three soils by nitrogen and phosphorus application. Potassium had only marginal effect on biomass growth but favourably influenced starch production. Sulfate application had no major impact on growth and starch yield. The yield response was well related to the level of available nutrients in the soil, as determined by electroultrafiltration (EUF). Leaf analysis provided preliminary evidence that optimum levels of N, P, and K may be 3.8%, 0.3%, and 4.8%, respectively.
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  • 95
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    Nutrient cycling in agroecosystems 32 (1992), S. 55-59 
    ISSN: 1573-0867
    Schlagwort(e): 15N ; nitrogen ; rice ; soil N ; N fertilizer
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In the southern U.S. rice belt it is recommended that rice (Oryza sativa L.) grown in the dry-seeded, delayed flood cultural system have the preflood N fertilizer applied and the field flooded at the fourth to fifth leaf stage of plant development. The objective of this field study was to determine if delaying the flood and preflood N application past the fifth leaf stage was detrimental to rice total N and fertilizer15N uptake, total dry matter, and grain yield. This study was conducted on a Crowley silt loam (Typic Albaqualfs) and a Perry clay (Vertic Haplaquepts). The preflood N fertilizer and flood were delayed 0, 7, 14, or 21 d past the fourth to fifth leaf stage, after which time a permanent flood was established and maintained until maturity. All treatments received 20.5 g N m−2 as15N-labeled urea in three topdress applications. All plant and soil samples were taken at maturity. Harvest index increased as the preflood N and flood were delayed past the 4 to 5 leaf stage. Total N in the grain + straw either decreased or showed a decreasing trend as the N and flood were delayed. Similarly, uptake of native soil N decreased as flood was delayed. Conversely, percent recovery of fertilizer N in the rice plant and the plant-soil system increased as the preflood N and flood were delayed. Rice grain yield was not significantly affected by delaying the preflood N and flood up to 21 d.
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  • 96
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    Nutrient cycling in agroecosystems 37 (1994), S. 227-234 
    ISSN: 1573-0867
    Schlagwort(e): catch crop ; mineralization ; nitrogen ; plant species ; residual effects ; soil depletion ; winter hardiness
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Ten widely different plant species were compared for their ability to reduce soil mineral nitrogen levels in the autumn and their ability to improve the nitrogen nutrition of the succeeding crop. The species included monocots and dicots, crops that survived the winter (persistent) or were winter killed (non-persistent) as well as legumes and non legumes. Their ability to reduce soil mineral nitrogen content was dependent on both root depth and persistency of the crops in the autumn. For non-persistent catch crops most of the mineralization of plant nitrogen occurred during the winter, and for some of these so early as to allow leaching of some mineralized nitrogen. For persistent crops most of the mineralization occurred shortly after incorporation in the spring. The effect of the catch crops on nitrogen uptake by the succeeding barley crop varied from 13 to 66 kg N ha−1 and the differences between the crops could not be related to any single character, but to a combination of root depth, persistency, plant nitrate accumulation, and depletion of the soil mineral nitrogen pool in spring.
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  • 97
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    Nutrient cycling in agroecosystems 40 (1994), S. 207-214 
    ISSN: 1573-0867
    Schlagwort(e): available P ; citrate insoluble P ; phosphorus sources ; triple superphosphate ; Triticum aestivum ; water soluble P ; wheat
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A greenhouse study was conducted to determine if soil pH affects the requirement for water-soluble P and the tolerance of water-insoluble impurities in TSP fertilizers. Two commercial TSP fertilizers were selected to represent a range in phosphate rock sources and impurities. Phosphate fertilizer impurities were isolated as the water-washed fraction by washing whole fertilizers with deionized water. TSP fertilizers with various quantities of water-soluble P (1.2 to 99% water-soluble P) were simulated by mixing the water-washed fertilizer fractions or dicalcium phosphate (DCP) with reagent-grade monocalcium phosphate (MCP). The fertilizers were applied to supply 40 mg AOAC available P kg−1 to a Mountview silt loam (fine-silty, siliceous, thermic Typic Paleudults). Wheat (Triticum aestivum (L.)) was harvested at 49 and 84 days after planting. Soil pH values at the final forage harvest were 5.4±0.16 and 6.4±0.15. At a soil pH of 5.4, the TSP fertilizers required only 37% water-soluble P to reach maximum yields while at pH 6.4 the fertilizers required 63% water-soluble P. Results of this study show that higher levels of water -insoluble P can be tolerated in TSP fertilizers when applied to acid soils. Phosphorus uptake was not affected by soil pH, but for the mixtures containing the fertilizer residues the source having the lowest level of Fe and Al had a higher relative agronomic effectiveness.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 98
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 35 (1993), S. 217-226 
    ISSN: 1573-0867
    Schlagwort(e): calcium ; dry matter distribution ; fertilizer ; harvest index ; magnesium ; manure ; millet ; nitrogen ; nutrient uptake ; phosphorus ; potassium ; Senegal
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract In a fertilizer and manure experiment, millet was grown under four treatments (no fertilizer or manure, farmyard manure, chemical fertilizer, and both). Grain yield and total aboveground biomass production of the unfertilized plot were relatively high. The observed differences in total dry matter production must be attributed to differences in nutrient availability, as amount of rainfall and its distribution were favourable. Results show only small differences in distribution of dry matter among the various plant organs between the best and the non-fertilized treatments. Nutrient supply from natural sources, defined as crop content of N, P, and K at maturity without fertilizer application, amounted to 104, 16 and 103 kg ha−1, respectively, which are very high values. Total uptake of calcium and magnesium is related to that of potassium, as the combined content of these three elements is linearly related to total aboveground biomass production. Minimum removal of nitrogen and phosphorus per ton grain dry matter amounts to 29 and 4kg, respectively, and 9 kg potassium per ton total aboveground dry matter. A possible double function of phosphorus as element of structural biomass and for maintenance of electro-neutrality is discussed.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 99
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 21 (1990), S. 167-170 
    ISSN: 1573-0867
    Schlagwort(e): Mo ; interaction ; soybean ; deficiency ; nitrogen
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract Recent on-farm liming experiments showed that Mo deficiency in soybean [Glycine max (L.) Merr.] is widespread in northern Alabama. In contrast, a long-term, fertility-rotation experiment in the same area showed no response to Mo during 33 yr when Mo was added bienially to corn [Zea mays L.] in the rotation; however, soybean foliage had the chlorotic appearance of Mo deficiency. The objective of this study was to determine if Mo deficiency was being missed by comparing only two fertilizer treatments. Each rotation-fertilizer treatment plot was split into two, with one-half receiving MO at a 100 g ha−1 foliar rate after seedling emergence, while the other half received none. Yields were increased by Mo in 13 to 16 fertilizer treatments in 1985 and 15 out of 16 in 1986. Leaf-N concentrations and seed weight had comparable increased amounts by the Mo supplement. Without the Mo supplement, there was a response to lime but not to P, K, or a Mo-containing micronutrient mixture; with the Mo supplement, there was no response to liming, but a definite response to P and K (in addition to Mo). The lack of response to Mo when applied to corn in a 2-yr rotation over 33 yr led to the erroneous conclusion that these soils were not Mo deficient for soybean.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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  • 100
    Digitale Medien
    Digitale Medien
    Springer
    Nutrient cycling in agroecosystems 22 (1990), S. 71-78 
    ISSN: 1573-0867
    Schlagwort(e): Boron ; critical level ; grain ; nitrogen ; nodulation ; nutrition ; toxicity
    Quelle: Springer Online Journal Archives 1860-2000
    Thema: Land- und Forstwirtschaft, Gartenbau, Fischereiwirtschaft, Hauswirtschaft
    Notizen: Abstract A two year field study on the effect of nitrogen N and boron B fertilization on the nodulation, mineral nutrition and grain yield of cowpea was carried out in the Nigerian savanna where fairly widespread B deficiency has been reported. Treatments consisted of four levels of N (0, 15, 30 and 60 kg/ha in 1986 and 0, 15, 30 and 45 kg/ha in 1987) and three levels of B (0, 1.5 and 3.0 kg/ha). Cowpea responded positively though nonsignificantly to N fertilization up to 30 kg N/ha. However, N had no effect on the N, P, K and B content of index leaves. Boron application consistently reduced grain yield. Like N, applied B had no effect on the N, P, K concentration of index leaves but increased B concentration highly significantly (P 〈 0.001). The critical level of B toxicity in index leaves was approximated to be 21pm under field condition. Application of N and B depressed nodulation.
    Materialart: Digitale Medien
    Standort Signatur Erwartet Verfügbarkeit
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