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  • 1
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    Journal of industrial microbiology and biotechnology 9 (1992), S. 229-234 
    ISSN: 1476-5535
    Keywords: Heat shock protein (HSP) ; Yeast ; Saccharomyces ; Viability ; Thermotolerance ; Ethanol tolerance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Heat shock and ethanol stress of brewing yeast strains resulted in the induction of a set of proteins referred to as heat shock proteins (HSPs). At least six strongly induced HSPs were identified in a lager brewing strain and four HSPs in an ale brewing strain. Four of these HSPs with molecular masses of approximately 70, 38, 26 and 23 kDa were also identified in two laboratory strains ofSaccharomyces cerevisiae. The appearance of HSPs correlated with increased survival of strains at elevated temperatures and high concentrations of ethanol. These results suggest that HSPs may play a role in the ethanol and thermotolerance of yeasts. The properties of these proteins and membrane fatty acids in relation to heat and ethanol shock are being investigated.
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  • 2
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    Journal of industrial microbiology and biotechnology 7 (1991), S. 191-195 
    ISSN: 1476-5535
    Keywords: Yeast ; Trehalose ; Osmotolerance ; Viability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary A total of 12 yeast strains from various genera were examined for their ability to produce ethanol in the presence of high concentrations of glucose. From these studies, the yeastsTorulaspora delbrueckii andZygosaccharomyces rouxii were observed to the most osmotolerant. These osmotolerant yeast strains were also observed to possess high concentrations of intracellular trehalose. Futhermore, these strains were found to be tolerant to long-term storage at −20°C and to storage at 4°C in beer containing 5% (v/v) ethanol. Cells containing high trehalose levels at the time of freezing or cold storage exhibited the highest cell viabilities. Trehalose concentration was observed to increase during growth on glucose, reaching a maximum after 24–48 h. Increasing the incubation temperature from 21 to 40°C also resulted in an increase in intracellular trehalose content. These results suggest that trehalose plays a role in enhancing yeast survival under environmentally stressful conditions.
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  • 3
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    Journal of industrial microbiology and biotechnology 7 (1991), S. 263-268 
    ISSN: 1476-5535
    Keywords: Yeast ; β-Glucanase ; β-Glucosidase catabolite repression ; Sporulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The activities of three glycosidases, β-glucosidase and β(1,3)- and β(1,6)-glucanases have been monitored during growth and blastospore formation inSaccharomycopsis fibuligera. The assays were carried out on the cell-free culture and in a cell-free extract and a wall autolysate preparation from the growing cells. In complex medium containing 1% glucose an increase in the level of all three enzymes was associated with the transition from mycelium to blastospores. When the level of glucose was increased to 5% blastospore formation was repressed and the level of β-glucanases only increased at the end of the fermentation. The β-glucosidase activity increased during the growth phase. In a defined medium in which slow growth in a wholly yeast-like form was observed, growth was not associated with a high level of β-glucanase activity.
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  • 4
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    Computing 24 (1980), S. 341-347 
    ISSN: 1436-5057
    Keywords: Numerical analysis ; Volterra integral equations of the second kind ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: Zusammenfassung Ziel dieser Arbeit ist es, die Stabilitätseigenschaften einer Klasse Volterrascher Integralgleichungen zweiter Art zu untersuchen. Unsere Behandlung ist der üblichen Stabilitätsanalyse ähnlich, in der die Kernfunktionen zu einer im voraus beschränkten Klasse von Testfunktionen gehören. Wir haben die Klasse der “endlich zerlegbaren” Kerne betrachtet. Stabilitätsbedingungen werden abgeleitet und verglichen mit den Bedingungen für die einfache Testgleichung. Es zeigt sich, daß die neuen Kriteria einschränkender sind als die konventionellen Bedingungen. Der praktische Wert wird getestet durch numerische Experimente mit der Trapezregel.
    Notes: Abstract The purpose of this paper is to analyse the stability properties of a class of multistep methods for second kind Volterra integral equations. Our approach follows the usual analysis in which the kernel function is a priori restricted to a special class of test functions. We consider the class of finitely decomposable kernels. Stability conditions will be derived and compared with those obtained with the simple test equation. It turns out that the new criteria are more severe than the conventional conditions. The practical value is tested by numerical experiments with the trapezoidal rule.
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  • 5
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    Computing 51 (1993), S. 271-292 
    ISSN: 1436-5057
    Keywords: 65N15 ; 65N99 ; 35A40 ; Box method ; boundary value problem ; finite volume method ; variational formulation ; stability ; error bounds
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: 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.
    Notes: 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.
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  • 6
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    European journal of nutrition 29 (1990), S. 219-228 
    ISSN: 1436-6215
    Keywords: Vitamin K ; Menadion ; Menadiol ; Bioverfügbarkeit ; Stabilität ; Geflügel ; vitamin K ; menadione ; menadiol ; bioavailability ; stability ; poultry
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition , Medicine
    Description / Table of Contents: 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.
    Notes: 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.
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  • 7
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    OR spectrum 16 (1994), S. 47-52 
    ISSN: 1436-6304
    Keywords: Vector optimization ; approximately efficient solutions ; stability ; Vektoroptimierung ; Näherungslösungen ; Stabilität
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Description / Table of Contents: 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.
    Notes: 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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  • 8
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    Mathematical programming 47 (1990), S. 117-141 
    ISSN: 1436-4646
    Keywords: Bifurcation ; singularity ; parametric programming ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: 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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  • 9
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    Mathematical programming 54 (1992), S. 57-67 
    ISSN: 1436-4646
    Keywords: Matchings ; stability ; extreme points ; polytope
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: 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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  • 10
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    Mathematical programming 61 (1993), S. 197-214 
    ISSN: 1436-4646
    Keywords: Epi-convergence ; epi-distance ; stability ; convex optimization ; approximate solutions ; subgradients ; level sets
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mathematics
    Notes: 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.
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  • 11
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    Computing 44 (1990), S. 187-196 
    ISSN: 1436-5057
    Keywords: 65M10 ; Spectral method ; stability ; stability threshold
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Description / Table of Contents: 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.
    Notes: 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.
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  • 12
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    Rheologica acta 22 (1983), S. 284-290 
    ISSN: 1435-1528
    Keywords: Viscometric flow ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract This paper examines three-dimensional disturbances of a plane steady shear flow of simple fluids with short memory. Under the assumption of nearly-viscometric flow, constitutive equations are derived and then a general form of the Reynolds-Orr energy equation is obtained. With the aid of this derived energy formula, sufficient conditions are generated for the stability of three-dimensional disturbances of the planar viscometric flow. These conditions are analysed and a comparison is made with the corresponding two-dimensional stability problem. There is a strong indication that the basic flow is less stable against three-dimensional disturbances than against two-dimensional ones.
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  • 13
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    Acta biotheoretica 39 (1991), S. 1-14 
    ISSN: 1572-8358
    Keywords: Hematological diseases ; first order partial differential equations ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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.
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  • 14
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    Journal of intelligent manufacturing 4 (1993), S. 183-198 
    ISSN: 1572-8145
    Keywords: Assembly planning ; subassembly ; liaison graph ; geometric reasoning ; assembly cost ; stability ; partial-order graph
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
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  • 15
    ISSN: 1572-8900
    Keywords: Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene (ABS) ; ABS/polycarbonate blend
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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
    Keywords: Chemiluminescence ; oxidation ; stability ; acrylonitrile-butadiene-styrene (ABS)
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Energy, Environment Protection, Nuclear Power Engineering , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: 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.
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  • 17
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    Journal of inorganic and organometallic polymers and materials 2 (1992), S. 79-85 
    ISSN: 1572-8870
    Keywords: Phthalocyanines ; polymers ; siloxanes ; conductivity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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
    Keywords: Chromium(III) ; β-diketones ; β-diketonates ; chelation ; complexation ; correlation ; stability ; equilibrium
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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
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    Catalysis letters 10 (1991), S. 225-232 
    ISSN: 1572-879X
    Keywords: VPI-5 ; stability ; molecular sieve ; post-synthesis treatments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: 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
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    Journal of dynamics and differential equations 6 (1994), S. 37-51 
    ISSN: 1572-9222
    Keywords: Celestial mechanics ; relative equilibria ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: 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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  • 21
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    Order 9 (1992), S. 163-175 
    ISSN: 1572-9273
    Keywords: Primary 06A07 ; secondary 05C70 ; Partial order ; interval ; stability ; covering ; Sperner property ; symmetric chains ; NP-completeness
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: 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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    Queueing systems 12 (1992), S. 369-389 
    ISSN: 1572-9443
    Keywords: Perturbation analysis ; stability ; stochastic difference equations ; simulation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: 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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    Queueing systems 13 (1993), S. 87-110 
    ISSN: 1572-9443
    Keywords: 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
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: 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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    Queueing systems 15 (1994), S. 279-288 
    ISSN: 1572-9443
    Keywords: Sample-path ; point processes ; workload ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: 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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    Queueing systems 16 (1994), S. 115-137 
    ISSN: 1572-9443
    Keywords: Polling systems ; stability ; stochastic continuity ; general arrival process ; functional limit theorems.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: 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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    Celestial mechanics and dynamical astronomy 56 (1993), S. 45-50 
    ISSN: 1572-9478
    Keywords: Restricted problem ; stability ; planets of double stars
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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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    Celestial mechanics and dynamical astronomy 58 (1994), S. 203-213 
    ISSN: 1572-9478
    Keywords: libration points ; resonances ; stability
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    Topics: Physics
    Notes: 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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    Journal of dynamics and differential equations 5 (1993), S. 625-671 
    ISSN: 1572-9222
    Keywords: Scalar reaction-diffusion equation ; singular perturbation methods ; internal layer ; Neumann layer ; stability ; 35K57 ; 35B25 ; 35B35
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    Topics: Mathematics
    Notes: 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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    Journal of dynamics and differential equations 6 (1994), S. 639-658 
    ISSN: 1572-9222
    Keywords: Symmetry ; parabolic equations ; positive solutions ; stability
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    Topics: Mathematics
    Notes: 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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    Annals of operations research 27 (1990), S. 343-369 
    ISSN: 1572-9338
    Keywords: Bifurcation ; singularities ; continuation ; parametric nonlinear programming ; stability
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    Topics: Mathematics , Economics
    Notes: 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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    Queueing systems 14 (1993), S. 159-175 
    ISSN: 1572-9443
    Keywords: Queueing networks ; nonproduct form networks ; stability ; stochastic continuity ; functional limit theorems
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    Topics: Computer Science
    Notes: 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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    Queueing systems 15 (1994), S. 211-238 
    ISSN: 1572-9443
    Keywords: polling system ; stability ; Markov chain ; stochastic monotonicity ; heavy traffic ; nonpreemptive local priority
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    Topics: Computer Science
    Notes: 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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    Queueing systems 17 (1994), S. 317-345 
    ISSN: 1572-9443
    Keywords: 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
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    Topics: Computer Science
    Notes: 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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    Queueing systems 11 (1992), S. 7-33 
    ISSN: 1572-9443
    Keywords: Token passing rings ; stability ; substability ; ergodicity ; Markov chains ; Loynes' scheme ; stochastically dominant ; Little's formula ; regenerative processes
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    Topics: Computer Science
    Notes: 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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    Celestial mechanics and dynamical astronomy 59 (1994), S. 345-374 
    ISSN: 1572-9478
    Keywords: Lagrangian points ; stability ; oblate primary
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    Topics: Physics
    Notes: 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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    Journal of dynamics and differential equations 5 (1993), S. 189-218 
    ISSN: 1572-9222
    Keywords: Equivariant bifurcation ; symmetry ; singularity ; equivariant jets and transversality ; normal forms ; universal unfolding ; stability ; structural stability ; 58F14 ; 58E07 ; 58C27
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    Topics: Mathematics
    Notes: 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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    Journal of dynamics and differential equations 6 (1994), S. 447-486 
    ISSN: 1572-9222
    Keywords: Free boundary problems ; gasless combustion ; stability ; Hopf bifurcation ; 35R35 ; 35B40 ; 80A25
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    Topics: Mathematics
    Notes: 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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    Set-valued analysis 1 (1993), S. 393-402 
    ISSN: 1572-932X
    Keywords: Primary: 49J40, 65K10, 47A55, 47H05, 65L20 ; Variational inequality ; perturbation ; unbounded and nonsmooth operators ; convex sets ; Hausdorff distance ; regularization ; monotonicity ; convergence ; stability
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    Notes: 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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    Queueing systems 6 (1990), S. 335-351 
    ISSN: 1572-9443
    Keywords: State-dependent service and interarrival times ; Lindley equation ; recursive stochastic equations ; stability ; stochastic comparisons ; normal approximations ; scheduling arrivals
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    Topics: Computer Science
    Notes: 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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    Journal of dynamics and differential equations 4 (1992), S. 161-190 
    ISSN: 1572-9222
    Keywords: Delay differential equations ; equilibrium ; stability ; limiting equations ; population dynamics ; 34K20 ; 34K25 ; 92A15
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    Topics: Mathematics
    Notes: 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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    Journal of dynamics and differential equations 5 (1993), S. 105-128 
    ISSN: 1572-9222
    Keywords: Delay system ; stability ; relative variance ; dynamical disease
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    Topics: Mathematics
    Notes: 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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    Journal of dynamics and differential equations 6 (1994), S. 325-334 
    ISSN: 1572-9222
    Keywords: Nonlinear Schrödinger equations ; anisotropic standing waves ; stability ; concentration compactness principle ; Davey-Stewartson system ; 35Q35 ; 35B35
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    Topics: Mathematics
    Notes: 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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    Journal of dynamics and differential equations 6 (1994), S. 631-637 
    ISSN: 1572-9222
    Keywords: stability ; fixed point index ; periodic solutions
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    Topics: Mathematics
    Notes: 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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    Journal of solution chemistry 22 (1993), S. 1151-1158 
    ISSN: 1572-8927
    Keywords: Molecular complexes ; solvent effect ; stability ; solid CT complexes ; nicotine
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    Topics: Chemistry and Pharmacology
    Notes: 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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    Acta applicandae mathematicae 28 (1992), S. 1-42 
    ISSN: 1572-9036
    Keywords: 35R30 ; Inverse scattering ; stability ; noisy data
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    Topics: Mathematics
    Notes: 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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    Annals of global analysis and geometry 11 (1993), S. 387-395 
    ISSN: 1572-9060
    Keywords: Curvatures of hypersurfaces ; Reilly's inequality ; stability ; 53 A 10 ; 53 C 42
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    Topics: Mathematics
    Notes: 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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    BIT 33 (1993), S. 332-350 
    ISSN: 1572-9125
    Keywords: AMS(MOS): 65L06 ; Multistep collocation method ; continuous solution ; stability
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    Topics: Mathematics
    Notes: 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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    Annals of global analysis and geometry 11 (1993), S. 221-235 
    ISSN: 1572-9060
    Keywords: Second variation formula ; Morse index ; stability ; 53C
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    Topics: Mathematics
    Notes: 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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    BIT 30 (1990), S. 332-346 
    ISSN: 1572-9125
    Keywords: 65D05 ; polynomial interpolaton ; Newton form ; stability ; Leja points ; ordering of interpolation points
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    Topics: Mathematics
    Notes: 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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    BIT 32 (1992), S. 634-649 
    ISSN: 1572-9125
    Keywords: AMS(MOS): 65L20 ; CR: 5.17 ; delay differential equations ; numerical solution ; Runge-Kutta methods ; interpolation procedures ; stability
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    Topics: Mathematics
    Notes: 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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    Celestial mechanics and dynamical astronomy 49 (1990), S. 219-231 
    ISSN: 1572-9478
    Keywords: n-body problem ; stability ; relative equilibrium
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    Topics: Physics
    Description / Table of Contents: 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.
    Notes: 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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    Celestial mechanics and dynamical astronomy 53 (1992), S. 145-150 
    ISSN: 1572-9478
    Keywords: Monodromy matrix ; Gauss hypergeometric equation ; stability
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    Notes: 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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    Celestial mechanics and dynamical astronomy 56 (1993), S. 323-324 
    ISSN: 1572-9478
    Keywords: chaos ; stability ; asteroids
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    Celestial mechanics and dynamical astronomy 57 (1993), S. 59-94 
    ISSN: 1572-9478
    Keywords: asteroids ; libration ; proper elements ; stability ; chaos ; families
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    Topics: Physics
    Notes: 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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    Celestial mechanics and dynamical astronomy 49 (1990), S. 249-264 
    ISSN: 1572-9478
    Keywords: Solar sails ; radiation pressure ; stability
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    Topics: Physics
    Notes: 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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    Celestial mechanics and dynamical astronomy 60 (1994), S. 307-315 
    ISSN: 1572-9478
    Keywords: Asteroid ; libration ; resonance ; stability
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    Topics: Physics
    Notes: 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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    Acta applicandae mathematicae 37 (1994), S. 129-136 
    ISSN: 1572-9036
    Keywords: 35B35 ; 35Q30 ; 76N10 ; stability ; Navier-Stokes equations ; compressible fluids
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: 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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  • 58
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    Celestial mechanics and dynamical astronomy 53 (1992), S. 219-226 
    ISSN: 1572-9478
    Keywords: Artificial satellite ; dissipative forces ; stability
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    Topics: Physics
    Notes: 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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  • 59
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    Celestial mechanics and dynamical astronomy 60 (1994), S. 249-271 
    ISSN: 1572-9478
    Keywords: Chaos ; periodic orbits ; stability ; asymptotic curves ; homoclinic points ; heteroclinic points
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    Topics: Physics
    Notes: 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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  • 60
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    Celestial mechanics and dynamical astronomy 55 (1993), S. 249-259 
    ISSN: 1572-9478
    Keywords: Asteroid ; libration ; resonance ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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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  • 61
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    Celestial mechanics and dynamical astronomy 55 (1993), S. 323-330 
    ISSN: 1572-9478
    Keywords: Periodic orbits ; rigid body dynamics ; stability
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    Topics: Physics
    Notes: 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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  • 62
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    Celestial mechanics and dynamical astronomy 55 (1993), S. 351-367 
    ISSN: 1572-9478
    Keywords: Sitnikov's problem ; invariant rotational curves ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: 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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  • 63
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    Celestial mechanics and dynamical astronomy 60 (1994), S. 99-129 
    ISSN: 1572-9478
    Keywords: Sitnikov motions ; periodic orbits ; stability ; bifurcations
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    Topics: Physics
    Notes: 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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  • 64
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    BIT 33 (1993), S. 74-84 
    ISSN: 1572-9125
    Keywords: 65J10 ; 65M12 ; Analytic semigroup ; Banach space ; rational approximation ; A-acceptable ; A(θ)-acceptable ; stability ; Crank-Nicolson method
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    Topics: Mathematics
    Notes: 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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    BIT 33 (1993), S. 285-303 
    ISSN: 1572-9125
    Keywords: 65L05 ; stiffness ; stability ; pseudospectra
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    Topics: Mathematics
    Notes: 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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  • 66
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    BIT 34 (1994), S. 62-79 
    ISSN: 1572-9125
    Keywords: AMS(MOS) 65D30 ; 65B05 ; adaptive ; cubature ; singularity ; extrapolation ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: 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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    Monatshefte für Chemie 111 (1980), S. 355-363 
    ISSN: 1434-4475
    Keywords: Cerulenin ; Fatty acid donor ; Inositol deficiency ; Phospholipid biosynthesis ; Triacylglycerols ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: Zusammenfassung Der Umsatz der Lipide vonSaccharomyces carlsbergensis ATCC 9080 wurde nach Vormarkierung mit3H-Ölsäure und14C-Palmitinsäure untersucht. Inositversorgte Zellen zeigen eine Verschiebung der Fettsäuren von den Triacylglycerinen in die Phospholipide, im besonderen in Phosphatidylcholin und Phosphatidylinosit. Eine verstärkte Übertragung der Fettsäuren von Triacylglycerinen auf Phospholipide konnte festgestellt werden, wenn vormarkierte Zellen auf ein Nährmedium, welches Cerulenin enthielt, übertragen wurde. Cerulenin inhibiert die Fettsäuresynthese und ruft in wachsenden Zellen Fettsäuremangel hervor. Inositdefiziente Hefezellen, welche einen erhöhten Triacylglycerinspiegel aufweisen, verwenden diese Triacylglycerine unter Fettsäuremangelbedingungen ebenfalls für die Synthese von Phospholipiden, besonders von Phosphatidylcholin, Phosphatidyläthanolamin und Phosphatidylserin. Da aus früheren Arbeiten bekannt ist, daß inSaccharomyces carlsbergensis praktisch keine β-Oxidation existiert, können die Triacylglyerine in diesem Hefestamm als Speicher für Fettsäuren angesehen werden, welche zur Synthese von Phospholipiden dienen.
    Notes: Abstract The turnover of lipids was studied in the yeast,Saccharomyces carlsbergensis ATCC 9080, after prelabeling of the cells with [3H] oleic acid and [14C] palmitic acid. In inositol supplemented cells, a redistribution of fatty acids from triacylglycerols to phospholipids (mainly phosphatidylcholine and phosphatidylinositol) could be demonstrated. An increased transfer of fatty acids from triacylglycerols to phospholipids was observed when prelabeled cells were transferred to a growth medium containing cerulenin, which inhibits fatty acid synthesis and thus induces fatty acid deficiency in the growing cells. Inositol deficient cells contain increased levels of triacylglycerols, which are equally well utilized for phospholipid (mainly phosphatidylcholine, phosphatidylethanolamine and phosphatidylserine) synthesis under conditions of fatty acid deficiency. The present results together with the previous finding that β-oxidation is practically absent inSaccharomyces carlsbergensis suggest that in this yeast triacylglycerols function as storage of fatty acids which can be mobilized for phospholipid biosynthesis.
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    Aquatic sciences 52 (1990), S. 330-344 
    ISSN: 1420-9055
    Keywords: Flood ; phytoplankton succession ; reversion ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: 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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    Cellular and molecular life sciences 48 (1992), S. 172-178 
    ISSN: 1420-9071
    Keywords: Yeast ; protein degradation ; ubiquitin conjugating enzymes ; signals for proteolysis ; stress response
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    Topics: Biology , Medicine
    Notes: Abstract Selective degradation of cellular proteins serves to eliminate abnormal proteins and to mediate the turnover of certain short-lived proteins, many of which have regulatory functions. In eukaryotes a major pathway for selective protein degradation is ATP-dependent and is mediated by the ubiquitin system. This pathway involves substrate recognition by components of a ubiquitin-protein ligase system, covalent attachment of ubiquitin moieties to proteolytic substrates, and subsequent degradation of these conjugates by a multicatalytic protease complex. Recent genetic evidence suggests that the remarkable selectivity of this process is largely controlled at the level of substrate recognition by the ubiquitin ligase system. InSaccharomyces cerevisiae, ubiquitin-conjugating enzymes UBC1, UBC4 and UBC5 have been identified as key components of this highly conserved degradation pathway. Genetic analysis indicates that ubiquitin-dependent proteolysis is essential for cell viability and that UBC4 and UBC5 enzymes are essential components of the eukaryotic stress response.
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    Catalysis letters 28 (1994), S. 25-31 
    ISSN: 1572-879X
    Keywords: vanadia/alumina ; stability ; NO x selective reduction
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    Topics: Chemistry and Pharmacology
    Notes: 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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  • 71
    ISSN: 1476-5535
    Keywords: Lignocellulosic waste ; Yeast ; Ethanol production ; Optimization study
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary Hardwood hemicellulose hydrolysate has been utilized as a substrate for ethanol production. Among the three different yeasts tested, the best performances have been obtained, in decreasing order, usingPachysolen tannophilus, Candida shehatae andPichia stipitis. Several pretreatments of this raw material have been studied to improve ethanol yields; in one such pretreatment a strain ofP. tannophilus produced ethanol with a yield of 0.29 gethanol/gsugars (gP/gS); which is only 15% less than the values observed with synthetic media. Neither aeration nor acetone addition improved the fermentation of this substrate; in fact, only a marked stimulation of biomass growth has been observed at the expense of both ethanol and xylitol production.
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    Journal of industrial microbiology and biotechnology 7 (1991), S. 35-39 
    ISSN: 1476-5535
    Keywords: 2-Deoxy-d-glucose ; Yeast ; Catabolite repression ; Derepression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Summary The non-metabolizable and toxic glucose analogue 2-deoxy-d-glucose (2-DOG) has been widely employed to screen for regulatory mutants which lack catabolite repression. A number of yeast mutants resistant to 2-DOG have recently been isolated in this laboratory. One such mutant, derived from aSaccharomyces cerevisiae haploid strain, was demonstrated to be derepressed for maltose, galactose and sucrose uptake. Furthermore, kinetic analysis of glucose transport suggested that the high affinity glucose transport system was also derepressed in the mutant strain. In addition, the mutant had an increased intracellular concentration of trehalose relative to the parental strain. These results indicate that the 2-DOG resistant mutant is defective in general glucose repression.
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    Archive for rational mechanics and analysis 72 (1980), S. 203-218 
    ISSN: 1432-0673
    Keywords: simple fluid ; viscoelastic ; fading memory ; stability ; Liapunov function ; dynamical system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract The nonlinear equations of motion for an incompressible simple fluid, occupying a fixed bounded container, are formulated on the basis of the “finitelinear” viscoelasticity theory for materials with fading memory; this formal boundary-initial value problem is then viewed as a nonlinear abstract evolution equation on a certain Hilbert space. It is shown that a linearized version of this evolution equation is associated with a linear dynamical system on this Hilbert space, and several results for stability and asymptotic behavior for this linearized problem are proved through the use of Liapunov stability methods. On the assumption that the original nonlinear evolution equation also is associated with some dynamical system on the same space, it is shown that the rest condition of the fluid is stable and all motions are bounded. The Liapunov function employed for this purpose can be interpreted as a mechanical energy function for the fluid.
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    Current genetics 17 (1990), S. 269-273 
    ISSN: 1432-0983
    Keywords: Yeast ; Actin ; Intron ; Antisense RNA
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    Topics: Biology
    Notes: Summary Using Northern blot analysis we have detected an approximately 840 nucleotide-long RNA which is complementary to the 5′ leader sequence and the first ten nucleotides of the coding sequence of the yeast actin (ACT1) messenger RNA. We have determined two transcription start sites for this actin antisense RNA (ASR1), both within the ACT1 intron, at about 80 and 90 nucleotides downstream from the 5′ splice site. Analysis of a cDNA clone showed that this RNA species overlaps the entire trailer sequence and approximately 20 nucleotides of the coding sequence of the nearby yeast YPT1 gene.
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  • 75
    ISSN: 1432-0983
    Keywords: Yeast ; Mutants ; Cytochrome ; Mitochondria ; Oxidative phosphorylation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This paper reports studies of bioenergetic modifications in a TTR1 single-nuclear mutant, isolated as resistant to triethyltin, an inhibitor of mitochondrial ATPase, and effective in cAMP-dependent protein phosphorylation. This mutant appears to have lost the wildtype cell ability to respond to a decrease of oxygen concentration in the growth medium by a decrease of cytochrome concentration in the cell. ATP synthesis rate in mutant cells in both the prestationary and stationary phase of growth appeared increased in comparison to wild-type cells, as too was respiration rate. A comparative study of mitochondria extracted from wild-type and from TTR1 mutant cells showed an increase in respiration rate, an increase in ATP synthesis rate, and an increase in TPP+ uptake in mutant mitochondria. The specific ATPase activity, as well as its sensitivity to TET, appears to be similar for mitochondria extracted from both strains. It was proposed that the modification of mitochondrial biogenesis in the TTR1 mutant may be due to a response of the cell to an increase in ATP hydrolysis caused by the mutation. It is also possible that the modification in cAMP-dependent protein kinase regulation which appeared to occur in this mutant affects protein(s) involved in mitochondrial biogenesis.
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  • 76
    ISSN: 1432-0983
    Keywords: Yeast ; Chromosome mapping ; Acidic ribosomal proteins
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary DNA probes from the genes encoding the acidic ribosomal proteins L44, L44′ and L45, as well as from reporter genes for chromosomes IV, VII, XII and XV, have been hybridised to Southern blots of Saccharomyces cerevisiae DNA resolved by pulsed field gel electrophoresis. The protein L44′ and protein L45 genes have been found to hybridise to chromosome IV, identified by the CAT1 gene probe, while the protein L44 probe hybridises with a band containing chromosomes VII and XV, identified by the ATPase 1 and HIS3 genes respectively.
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    Current genetics 19 (1991), S. 329-332 
    ISSN: 1432-0983
    Keywords: Mismatch repair ; Plasmid integration ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A single base pair mismatch (G:T or A:C) in the CYC1 gene of the integrative plasmid pAB218 stimulates up to a five-fold integration into the yeast chromosome. Analysis of chromosomal sites of plasmid integration suggests that the mismatch-stimulated integration is not targeted as would be expected if crossovers, localised in the region of the mismatch, were a necessary step in mismatch repair. Instead, the observed mismatch-stimulated plasmid integration could be due to potentially recombinogenic structures formed during mismatch repair, such as single-stranded gaps or denatured DNA regions extending around the plasmid molecule.
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  • 78
    ISSN: 1432-0983
    Keywords: PET genes ; Yeast ; Mitochondria ; ATP synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary This study details the characteristics of two temperature-conditional pet mutants of yeast, strains ts1860 and ts379, which at the non-permissive temperature show deficiencies in the formation of three mitochondrially encoded subunits of the ATP synthase complex. By analysis of mitochondrial translation products, and of mitochondrial transcription in temperature shift experiments from the permissive (22°C) to the non-permissive (36°C) temperature, it was concluded that the nuclear mutations in both mutants primarily inhibit synthesis of ATP synthase subunit 9, and that reductions in subunit 8 and 6 synthesis are secondary pleiotropic effects. Following transfer to 36°C, cells of mutant ts379 display a near complete inhibition of subunit 9 synthesis within 1 h, coincident with a marked reduction in the level of the cognate oli1 mRNA. On the other hand, near complete inhibition of subunit 9 synthesis in strain ts1860 occurs after 3 h at 36°C, at which time there is little change in the level of subunit 9 mRNA. In both mutants the mRNA levels for subunits 6 and 8 are not significantly affected at the time of inhibition of subunit 9 synthesis. Provision of an alternative source of subunit 8, translated extra-mitochondrially for import into the organelle, does not overcome the mutant phenotype of either mutant at 36°C, confirming that subunit 8 is not the sole or primary deficiency in each mutant. The mutants indicate that the products of a least two nuclear genes (designated AEP1 and AEP2) are required for the expression of the mitochondrial oli1 gene and the synthesis of subunit 9. The product of the AEP1 gene (defective in mutant ts1860) is required for translation of oli1 mRNA while the AEP2 product (defective in mutant ts379) is essential either for the stability of oli1 mRNA or for the correct processing of precursor transcripts to the mature message.
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    Current genetics 19 (1991), S. 389-393 
    ISSN: 1432-0983
    Keywords: Yeast ; Pichia inositovora ; Linear plasmids ; Killer toxin
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Pichia inositovora, strain NRRL Y-18709, which contains three linear double-stranded DNA plasmids, pPinl-1, pPinl-2 and pPinl-3, was cured of these plasmids both by growing the strain in the presence of 50 μg/ml bisbenzimide, and by exposure to ultraviolet light. Both cured and uncured strains were tested for growth on a variety of carbon sources. No differences in growth response were detected, indicating no discernible involvement of the linear plasmids in the catabolism of these compounds. Culture supernatants of Pichia inositovora were shown to contain a substance larger than 100 kDa that is toxic to Saccharomyces cerevisiae, strain GS 1688. Toxin activity was optimal in YEPD assay plates containing 50 mM citrate buffer with a pH between 3.4 and 4.2. Culture supernatants from P. inositovora were also weakly active against Cephaloascus albidus, strain NRRL Y-18710, and Citeromyces matritensis, strain NRRL Y-18711. Concentrated supernatants from cured P. inositovora strains did not exhibit these activities, consistent with the hypothesis that this toxic activity is linear plasmid-encoded. Unlike the wellknown Kluyveromyces lactis system or the newly identified P. acaciae system, P. inositovora strains cured of their linear plasmids do not become detectably sensitive to toxin produced by the wild-type strain, suggesting a nonplasmid-encoded immunity function.
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  • 80
    ISSN: 1432-0983
    Keywords: Yeast ; Molecular cloning ; Nitrogen mustard hyper-resistance ; Choline transport
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The recessive hnm1 mutant allele is responsible for hyper-resistance to nitrogen mustard in Saccharomyces cerevisiae. Transformation with a single-copy HNM1 wild-type allele of such hyper-resistant mutants will restore wild-type sensitivity to nitrogen mustard. By contrast the presence of multi-copy vectors containing HNM1, in either a hyper-resistant hnm1 mutant or an HNM1 wild-type, will lead to a novel, mustard-sensitive phenotype unrelated to defects in DNA repair genes. Gene disruption of HNM1 revealed that this gene is nonessential for cells prototrophic for choline (CHO1) but lethal for cells with a cho1 genotype. Sensitivity to nitrogen mustard of wild-type HNM1, but not of hnm1 mutants, depends on the choline content of the growth medium, with cells grown in choline-free medium exhibiting the highest sensitivity. Sequencing of a 300 bp DNA fragment of HNM1 revealed the identity of this gene with the CTR locus, which is responsible for choline transport in Saccharomyces cerevisiae.
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  • 81
    ISSN: 1432-0983
    Keywords: Mutagen hyper-resistance ; Yeast ; Base sequence ; Gene disruption
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A multi-copy plasmid containing the SNQ3 gene confers hyper-resistance to 4-nitroquinoline-N-oxide (4NQO), Trenimon, MNNG, cycloheximide, and to sulfometuron methyl in yeast transformants. Restriction analysis, subcloning, and DNA sequencing revealed an open reading frame of 1950 bp on the SNQ3-containing insert DNA. Gene disruption and transplacement into chromosomal DNA yielded 4NQO-sensitive null mutants which were also more sensitive than the wild-type to Trenimon, cycloheximide, sulfometuron methyl, and MNNG. Hydropathic analysis showed that the SNQ3-encoded protein is most likely not membrane-bound, while the codon bias index points to low expression of the gene.
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  • 82
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Intragenic recombination ; Mutant polypeptides
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Recombinational analysis of oxil mutants was performed using a and a mutant strains with the same mitochondrial and nuclear backgrounds, derived from strain 777-3A. In spite of minor inconsistencies the overall map of oxi1 mutations can be constructed on the basis of wild-type recombinant frequencies in the two-point oxi1 − − x oxi1 − crosses. The frequencies of wild-type recombinants varied in a wide range from 0.003% to 16%, reaching the maximal values expected for unlinked mitochondria) markers. No distinct clusters of mutants were observed. The analysis of translation products of oxil mutants showed that all but one of the oxil mutants studied are connected with the conspicuous changes of the polypeptide band corresponding to subunit 11 of cytochrome c oxidase in electrophoresis on polyacrylamide gels. The exceptional G565 mutant showed no conspicuous change in subunit II, but lacked subunit I of cytochrome c oxidase. Various oxi1 mutants seemed to carry premature chain termination mutations. Most of them show a correlation between the length of the putative fragment of subunit II synthesized and the position on the genetic map. The direction of translation is from the V2 to the V60 mutation. The V2 mutation is proximal to cap and V60 proximal to the par locus.
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  • 83
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    Current genetics 2 (1980), S. 61-67 
    ISSN: 1432-0983
    Keywords: Axenomycin ; Ribosome genetics ; Yeast ; Protein synthesis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Axenomycin inhibits protein synthesis in vivo and in vitro in Saccharomyces cerevisiae. The antibiotic acts by binding to ribosomes, most probably to the large ribosomal subunit. Mutant strains resistant to axenomycin appear to contain ribosomes that are not inhibited by the antibiotic. The responsible gene has been mapped on the VII chromosome between the centromere and the leu1 gene.
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  • 84
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    Current genetics 19 (1991), S. 89-94 
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondria ; Intron ; Mobile
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The mitochondrial and nuclear genomes of 21 yeast species belonging to 12 genera have been tested for the presence of sequences similar to seven S. cerevisiae mitochondrial introns (Sc cox1.1,2,3,4,5c, Sc cob.4 and Sc LSU.1) and one K. lactis mitochondrial intron (Kl cox1.2). Some introns, (Sc cox1.4, Sc cob.4, Sc LSU.1 and Kl cox1.2-all group I type), are widely distributed and are found in species with either basidiomycete or ascomycete affinities. This distribution is suggestive of recent sequence transfer between species. The remaining S. cerevisiae introns cross react with an additional species but with no set pattern. Pulsed field gel electrophoretic studies confirm that none of the tested mitochondrial introns cross react with nuclear DNA. These introns are, therefore, mitochondria-specific. Seven strains of K. lactis exhibit striking variability in intron content. In contrast to all mitochondrial introns tested, two introns of nuclear genes (the K. lactis actin gene and the S. cerevisiae RP29B gene) are not detected beyond their source species.
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  • 85
    ISSN: 1432-0983
    Keywords: Yeast ; Pyruvate decarboxylase ; Gene expression ; Codon usage ; Gene fusion
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Three structural genes encode the pyruvate decarboxylase isoenzymes in the yeast Saccharomyces cerevisiae. PDC1 and PDC5 are active during glucose fermentation where PDC1 is expressed about six times more strongly than PDC5. Expression of PDC6 is weak and seems to be induced in ethanol medium. Consequently, pdc1Δ pdc5Δ double mutants do not ferment glucose and do not grow on glucose medium. Spontaneous mutants, derived from such a pdc1 pdc5 strain, were isolated which could again ferment glucose. They showed pyruvate decarboxylase activity due to a duplication of PDC6. The second copy of PDC6 was expressed under the control of the PDC1 promoter, which was still present in the pdc1 strain. However, the resulting PDC1-PDC6 fusion gene could only partially substitute for PDC1: to achieve normal growth and high pyruvate decarboxylase activity strains carrying PDC1-PDC6 required a functional PDC5 gene which is dispensable in a PDC1 wild-type background. Thus, expression of PDC5 depends on the state of the PDC1 locus: low in the PDC1 wild-type background and high in PDC1-PDC6 fusion strains and, as shown previously, in pdc1 mutants. The activation of PDC5 expression in PDC1-PDC6 strains may be due to particular properties of the PDC1-PDC6 fusion protein or simply to the weaker expression of PDC1-PDC6 in comparison to the wild-type PDC1 gene.
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  • 86
    ISSN: 1432-0983
    Keywords: AEP2 ; Yeast ; Mitochondria ; ATP synthase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary The temperature-conditional pet mutant, ts379, of Saccharomyces cerevisiae fails to synthesize mitochondrial ATP synthase subunit 9 at the restrictive temperature due to mutation of a single nuclear locus, AEP2. The inability to synthesize subunit 9 correlates with a lowered accumulation of the cognate oli1 mRNA indicating that the AEP2 product is involved in oli1 transcript maturation or stabilization. The AEP2 gene has been isolated in this study from a wild-type yeast genomic library by genetic complementation of ts379 at the restrictive temperature. A 1740 nucleotide open-reading frame was observed that encodes a basic, hydrophilic protein of 67534 Da which possesses a putative mitochondrial address signal. Disruption of chromosomal DNA within this reading frame produced a non-conditional respiratory mutant unable to synthesize subunit 9, identifying the AEP2 gene. Hybridization analyses indicate that AEP2 is located on chromosome XIII and produces a 2.1 kb poly(A)+ transcript. Two additional open-reading frames were found in close proximity to that of AEP2. The three open-reading frames shared no significant homology with entries in several data bases.
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  • 87
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein gene ; Sequence analysis
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two genes encoding ribosomal protein YL41 were cloned from Saccharomyces cerevisiae chromosomal DNA. Both genes contain an uniterrupted region of only 75 nucleotides coding for a protein of 3.3 kD. Within the coding regions the nucleotide sequences are virtually identical, whereas in both the 5′-and 3′-flanking regions the two genes differ significantly from each other. The deduced protein shows an arginine and lysine content of 68 percent, i.e., 17 out of 25 residues, and the basic residues are evenly distributed over the molecule. When compared to the ribosomal protein sequences currently available no counterpart to YL41 could be found in prokaryotes and it seems likely that YL41 is a eukaryotespecific ribosomal protein.
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  • 88
    ISSN: 1432-0983
    Keywords: Yeast ; Trans-acting Factor ; RAP1
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We show by deletion mutagenesis, followed by in vivo and in vitro analysis, that the binding of a protein factor to the upstream activation sequence (USA) of the Saccharomyces cerevisiae glycolytic gene PYK, encoding pyruvate kinase, is required for efficient transcription of the corresponding coding region. In addition, gel electrophoretic mobility shift and DNase I protection studies, involving yeast gene products expressed in E. coli, suggest that this trans-acting DNA-binding protein is encoding by the RAP1 gene. The identification of RAP1 binding sites located within the UAS element of the yeast PYK, PGK (phosphoglycerate kinase) and ENO1 (enolase) genes, and in the 5′-upstream region of the ADHI (alcohol dehydrogenase) gene, suggests that a mechanism of coordinate gene expression involving several of the glycolytic genes may exist in yeast.
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  • 89
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    Current genetics 18 (1990), S. 485-491 
    ISSN: 1432-0983
    Keywords: Yeast ; Ty elements ; Virus like particles
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Electron microscopic analysis of thin sections of Saccharomyces cerevisiae NCYC74 has revealed the presence of many clumped cytoplasmic particles that morphologically resemble Ty element virus-like particles (VLPs). Accumulation of Ty VLPs has only previously been observed in S. cerevisiae strains that over-express a cloned Ty element. The particles in NCYC74 co-purify with Ty RNA, Ty-specific antigens and a reverse transcriptase activity. Furthermore, they appear to be recognised by antibodies to Ty VLPs during indirect immunofluorescence experiments. These observations provide compelling evidence that the cytoplasmic particle in NCYC74 are indeed Ty VLPs.
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  • 90
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    Current genetics 18 (1990), S. 29-39 
    ISSN: 1432-0983
    Keywords: Recombination ; DNA repair ; UV irradiation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A novel synthetic locus is described that provides a simple assay system for characterizing mitotic recombinants. The locus consists of the TRP1 and HIS3 genes inserted into chromosome III of S. cerevisiae between the CRY1 and MAT loci. Defined trp1 and his3 alleles have been generated that allow the selection of interchromosomal recombinants in this interval. Trp+ or His+ recombinants can be divided into several classes based on coupling of the other alleles in the interval. The tight linkage of the CRY1 and MAT loci, combined with the drug resistance and cell type phenotypes that they respectively control, facilitates the classification of the recombinants without resorting to tetrad dissection. We present the distribution of spontaneous recombinants among the classes defined by this analysis. The data suggest that the recombination intermediate can have regions of symmetric strand exchange and that co-conversion tracts can extend over 1–3 kb. Continuous conversion tracts are favored over discontinuous tracts. The distribution among the classes defined by this analysis is altered in recombinants induced by UV irradiation.
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  • 91
    ISSN: 1432-0983
    Keywords: Yeast ; Mitochondrial RNA splicing ; Nuclear pet - mutant ; Group I introns
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have studied the role of the product of the nuclear gene PET157 in mitochondrial pre-mRNA splicing. Cytoduction experiments show that a mitochondrial genome deleted for the three introns bI3, aI5 and aI6 is able to suppress the pet157-1 mutation: the strain recovers respiratory competency indicating that the product of the PET157 gene is only required for mitochondrial premRNA splicing. Characterization of the high molecular weight pre-mRNAs which accumulate in the pet157 mutant demonstrate that the product of the PET157 gene is required for the excision of two group I introns bI3 and aI6 (corresponding to aI5β) located in the cob-box and coxI genes respectively. Furthermore, the pet157 mutant strain accumulates the bI3 maturase in the form of a polypeptide of 50K (p50) previously observed in mitochondrial mutants defective in the excision of bI3. We have shown by restriction analysis and allelism tests that the pet157-1 mutation is allelic to the nuclear mrs1 mutation, previously described as specifically blocking the excision of bI3. Finally, revertants obtained by the deletion of bI3 or aI6 from the mitochondrial DNA were isolated from the MRS1 disrupted allele, confirming the involvment of the product of the MRS1/PET157 gene in the excision of the two introns bI3 and aI6.
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  • 92
    ISSN: 1432-0983
    Keywords: S. cerevisiae ; Yeast ; Cadmium resistance ; CAD2 gene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A cadmium-resistant strain, X3382-3A, which is able to grow in a medium containing 0.2 mM cadmium sulfate, was picked out from our laboratory stock strains of Saccharomyces cerevisiae. The cadmium resistance of this strain is controlled by a single dominant nuclear gene, denoted as CAD2. The locus of CAD2 was mapped by gene linkage to a site 15.5 centimorgans to the right of the his7 locus on the right arm of chromosome II. The cadmium resistance of the strain carrying CAD2 was evaluated for its properties of cadmium uptake, cadmium distribution and cadmium-metallothionein formation, in comparison with those of some other strains. The results suggest that the novel type of cadmium resistance controlled by CAD2 does not involve production of a cadmiumm-metallothionein.
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  • 93
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    Current genetics 2 (1980), S. 207-210 
    ISSN: 1432-0983
    Keywords: Yeast ; Plasmid ; Repair
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary We have developed a system for assaying pyrimidine dimers in the 2 ⇐m DNA plasmid of Saccharomyces cerevisiae, using Micrococcus luteus UV endonuclease to nick dimer-containing plasmid molecules and measuring percentages of nicked and covalently closed circles on agarose gels. UV-irradiation induced dimers in plasmid DNA, in vivo, at the same rate as in chromosomal DNA. After a dose of 20 Joules·m−2, approximately 86% of plasmid molecules had. at least one dimer. After 3 h incubation under normal growth conditions only 4% still retained dimers in a wild-type strain. In a rad1 (excision-defective) mutant 81% of plasmid molecules still had dimers after 3 h, suggesting that excision repair operates to remove dimers from plasmid DNA in wild-type yeast. Dimers can be removed from 2 ,um DNA in a rad1 mutant by photoreactivation.
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  • 94
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    Current genetics 2 (1980), S. 211-214 
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein dimorphism
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Two-dimensional gel electrophoresis was used in a comparative study of ribosomal proteins from various strains of Saccharomyces cerevisiae. The results demonstrated a case of dimorphism of L8 protein of 60S ribosomal subunit. Of eight strains examined, two strains were one type and six were the other type. The former, which was tentatively designated as altered (A) type, was more acidic than the latter, common (C) type, as shown by mobility difference in pH gradient gel. Heterozygous (A/C) diploid cells contained both types of L8 protein and gave rise to tetrads of 2:2 segregation for A and C types, indicating that the difference of mobility was reflection of the allelic difference of the gene coding for L8 protein.
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  • 95
    ISSN: 1432-0983
    Keywords: Pulsed field gel-electrophoresis ; S1 nuclease sensitive sites ; Repair ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Repair under non-growth conditions of DNA double-strand breaks (DSB) and chromatin sites sensitive to S1 endonuclease (SSS) induced by 60Cobalt-gamma rays were monitored in repair-competent and deficient strains of Saccharomyces cerevisiae by pulsed field gelelectrophoresis. In stationary-phase cells of a repair-competent RAD diploid, and an excision-deficient rad3-2 diploid, SSS are repaired as efficiently as DSB, whereas in a repair-competent RAD haploid, and a rad 50-1 diploid, neither SSS nor DSB are repaired. The rad18-2 diploid repairs DSB well but is defective in SSS repair. Obviously, SSS repair in yeast chromatin, like DSB repair, depends on recombination, but unlike DSB repair depends additionally on RAD18 function.
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  • 96
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    Current genetics 1 (1980), S. 177-183 
    ISSN: 1432-0983
    Keywords: Yeast ; Ribosomal protein alteration ; Cycloheximide
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary A spontaneous high-level cycloheximide-resistant mutant of the yeast Saccharomyces cerevisiae (strain cy32) is found to have an altered protein of the large subunit (60S) of cytoplasmic ribosomes, namely protein L29. The resistance character segregates together with this biochemical defect and is semidominant in heterozygous diploids. Judged from in vitro susceptibility to inhibition by cycloheximide there are at least 50% resistant ribosomes present in such diploid strains. From these results it is concluded that cycloheximide resistance of mutant cy32 is caused by mutation of a single gene and that it is the structural gene for L29 which is affected. Preliminary genetic mapping data are also reported. They indicate a location of cyhx-32 marker on chromosome 7 near met13.
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  • 97
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    Current genetics 17 (1990), S. 179-183 
    ISSN: 1432-0983
    Keywords: Heme ; Cytochromes ; Regulation ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Simultaneous effects of mutations in the transcriptional regulatory genes, HAP1, HAP2 and HAP3, on all respiratory cytochromes of Saccharomyces cerevisiae were determined. Cytochrome behavior in hap mutants and in cyc4 and rhm1 mutants, altered in regulation of 5-aminolevulinate synthase, was compared. Although hap mutants were isolated as trans-acting, transcriptional regulators of the CYC1 (iso-1-cytochrome c) gene, each mutant exhibits partial deficiencies in all cytochrome types. In hap2 and hap3 strains all cytochromes were decreased proportionally to about 40–50% of wild type values. In contrast, hap1 caused a decrease in all cytochromes and an accumulation of a pigment, probably Zn porphyrin. Apparently apocytochrome and heme biosynthesis retain coordination in hap2 and hap3, but not in hap1, mutants. Unlike cyc4 and rhm1 mutants, hap mutants do not exhibit 5-aminolevulinate-dependent restoration of cytochromes. The hap1 mutant grew at nearnormal rates on glycerol, whereas hap2 and hap3 mutants grew very slowly. The frequency of [rho-] was high (16–18%) in hap2 and hap3 strains. Results are consistent with generalized control of mitochondrial replication directed by the HAP1-HAP2 system and heme-directed control of formation of all apocytochromes mediated by HAP1. Neither system exerts all-or-nothing control.
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  • 98
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    Current genetics 17 (1990), S. 275-280 
    ISSN: 1432-0983
    Keywords: Yeast ; DNA replication ; Effect on mutation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Incubation in YPD medium under permissive conditions when DNA replication is going on, strongly stimulates the induction of cdc+ colonies of UV-irradiated cells of yeast strains HB23 (cdc8-1/cdc8-3), HB26 (cdc8-3/cdc8-3) and HB7 (cdc8-1/cdc8-1). Inhibition of DNA replication by hydroxyurea, araCMP, cycloheximide or caffeine or else by incubation in phosphate buffer pH 7.0, abolishes this stimulation. Thus the replication of DNA is strongly correlated with the high induction of cdc+ colonies by UV irradiation. It is postulated that these UV-induced cdc+ colonies arise as the result infidelity in DNA replication.
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  • 99
    ISSN: 1432-0983
    Keywords: Yarrowia lipolytica ; 7SL RNA ; Essential genes ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Cells containing a deletion of either the SCR1 or SCR2 genes, which code for the 7SL RNA component of the signal recognition particle (SRP) homologue, were found to be viable. Two independent approaches demonstrated that cells containing deletions of both genes were inviale. Therefore, Yarrowia lipolytica contains two (and only two) functional 7SL RNA genes.
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  • 100
    ISSN: 1432-0983
    Keywords: Mitotic recombination ; Hyper-recombination ; RAD50 ; Yeast
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Summary Mutations in the RAD50 gene of Saccharomyces cerevisiae have been shown to reduce double strand break repair, meiotic recombination, and radiation-inducible mitotic recombination. Several different point mutations (including ochre and amber alleles) have been previously examined for effects on spontaneous mitotic recombination and did not reduce the frequency of recombination. Instead, the rad50 mutations conferred a moderate hyper-rec phenotype. This paper examines a deletion/interruption allele of RAD50 that removes 998 of 1312 amino acids and adds 1.1 kb of foreign DNA. The results clearly indicate that spontaneous mitotic recombination can occur in the absence of RAD50; in fact, the frequency of recombination is elevated over the wild-type cell. One possible interpretation of these observations is that the initiating lesion in spontaneous recombination events in mitosis might not be a double strand break.
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