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  • DSC  (58)
  • stability  (58)
  • Saccharomyces cerevisiae
  • Springer  (134)
  • American Association for the Advancement of Science
  • American Institute of Physics (AIP)
  • 2000-2004  (134)
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  • 1
    Electronic Resource
    Electronic Resource
    Stabilization of smoothness priors time-varying autoregressive models (2000)
    Springer
    Circuits, systems and signal processing 19 (2000), S. 423-435 
    Details
    ISSN: 1531-5878
    Keywords: Time-varying autoregressive models ; stability ; smoothness priors ; Tihkonov regularization ; constrained optimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract The stability of time-varying autoregressive (AR) models is an important issue in such applications as time-varying spectrum estimation and electroencephalography simulation and estimation. In some cases, such as time-varying spectrum estimation, the models that exhibit roots near unit moduli are difficult to use. Thus a tighter stability condition such as stability with a positive margin is needed. A time-varying AR model is stable with a positive margin if the moduli of the roots of the time-varying characteristic polynomial are somewhat less than unity for every time instant. Recently, a new method for the estimation of the time-varying AR models was introduced. This method is based on the interpretation of the underdetermined time-varying prediction equations as an ill-posed inverse problem that is solved by Tikhonov regularization. The method is referred to as the deterministic regression smoothness priors (DRSP) scheme. In this paper, a stabilization method in which the DRSP scheme is augmented with nonlinear stability constrainst is proposed. The problem is formulated so that stability with a positive margin can also be achieved. The problem is solved iteratively with an exterior point algorithm. The performance of the algorithm is studied with a simulation. It is shown that the proposed approach is well suited to stable modeling of signals containing narrowband transitions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01196156
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  • 2
    Electronic Resource
    Electronic Resource
    Stability of constant coefficient linear singular systems with delay (2000)
    Springer
    Circuits, systems and signal processing 19 (2000), S. 13-25 
    Details
    ISSN: 1531-5878
    Keywords: Singular systems ; delay ; consistency condition ; stability ; instability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract In this paper, the general class of singular systems with delay and linear constant coefficient singular systems with delay are discussed. First, several definitions of stability are presented for singular systems with delay, and general sufficient stability conditions and instability conditions are obtained. Second, stability and instability are analyzed for linear constant coefficient singular systems with delay.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01229989
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  • 3
    Electronic Resource
    Electronic Resource
    The Dynamics of a Fish Stock Exploited in Two Fishing Zones (2000)
    Springer
    Acta biotheoretica 48 (2000), S. 207-218 
    Details
    ISSN: 1572-8358
    Keywords: Dynamical population ; fishing efforts ; metapopulation ; time scales ; aggregation method ; equilibrium ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract This work presents a specific stock-effort dynamical model. The stocks correspond to two populations of fish moving and growing between two fishery zones. They are harvested by two different fleets. The effort represents the number of fishing boats of the two fleets that operate in the two fishing zones. The bioeconomical model is a set of four ODE's governing the fishing efforts and the stocks in the two fishing areas. Furthermore, the migration of the fish between the two patches is assumed to be faster than the growth of the harvested stock. The displacement of the fleets is also faster than the variation in the number of fishing boats resulting from the investment of the fishing income. So, there are two time scales: a fast one corresponding to the migration between the two patches, and a slow time scale corresponding to growth. We use aggregation methods that allow us to reduce the dimension of the model and to obtain an aggregated model for the total fishing effort and fish stock of the two fishing zones. The mathematical analysis of the model is shown. Under some conditions, we obtain a stable equilibrium, which is a desired situation, as it leads to a sustainable harvesting equilibrium, keeping the stock at exploitable densities.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010208910738
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  • 4
    Electronic Resource
    Electronic Resource
    A gene of the major facilitator superfamily encodes a transporter for enterobactin (Enb1p) in Saccharomyces cerevisiae (2000)
    Springer
    BioMetals 13 (2000), S. 65-72 
    Details
    ISSN: 1572-8773
    Keywords: major facilitator superfamily ; iron transport ; siderophores ; enterobactin ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology
    Notes: Abstract While in fungi iron transport via hydroxamate siderophores has been amply proven, iron transport via enterobactin is largely unknown. Enterobactin is a catecholate-type siderophore produced by several enterobacterial genera grown in severe iron deprivation. By using the KanMX disruption module in vector pUG6 in a fet3Δ background of Saccharomyces cerevisiae we were able to disrupt the gene YOL158c Sce of the major facilitator super family (MFS) which has been previously described as a gene encoding a membrane transporter of unknown function. Contrary to the parental strain, the disruptant was unable to utilize ferric enterobactin in growth promotion tests and in transport assays using 55Fe-enterobactin. All other siderophore transport properties remained unaffected. The results are evidence that in S. cerevisiae the YOL158c Sce gene of the major facilitator super family, now designated ENB1, encodes a transporter protein (Enb1p), which specifically recognizes and transports enterobactin.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009250017785
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  • 5
    Electronic Resource
    Electronic Resource
    Performance analysis of a slotted-ALOHA protocol on a capture channel with fading (2000)
    Springer
    Queueing systems 34 (2000), S. 1-35 
    Details
    ISSN: 1572-9443
    Keywords: multiple access ; CDMA ; rates of convergence ; stability ; functional limit theorems ; transient analysis ; Markov-modulated capture channel
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the slotted ALOHA protocol on a channel with a capture effect. There are M 〈 ∞ users each with an infinite buffer. If in a slot, i packets are transmitted, then the probability of a successful reception of a packet is q i. This model contains the CDMA protocols as special cases. We obtain sufficient rate conditions, which are close to necessary for stability of the system, when the arrival streams are stationary ergodic. Under the same rate conditions, for general regenerative arrival streams, we obtain the rates of convergence to stationarity, finiteness of stationary moments and various functional limit theorems. Our arrival streams contain all the traffic models suggested in the recent literature, including the ones which display long range dependence. We also obtain bounds on the stationary moments of waiting times which can be tight under realistic conditions. Finally, we obtain several results on the transient performance of the system, e.g., first time to overflow and the limits of the overflow process. We also extend the above results to the case of a capture channel exhibiting Markov modulated fading. Most of our results and proofs will be shown to hold also for the slotted ALOHA protocol without capture.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019192600091
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  • 6
    Electronic Resource
    Electronic Resource
    Normal Form Invariants Around Spin-orbit Periodic Orbits (2000)
    Springer
    Celestial mechanics and dynamical astronomy 78 (2000), S. 227-241 
    Details
    ISSN: 1572-9478
    Keywords: stability ; normal form ; spin-orbit resonance
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We consider a model of spin-orbit interaction, describing the motion of an oblate satellite rotating about an internal spin-axis and orbiting about a central planet. The resulting second order differential equation depends upon the parameters provided by the equatorial oblateness of the satellite and its orbital eccentricity. Normal form transformations around the main spin-orbit resonances are carried out explicitly. As an outcome, one can compute some invariants; the fact that these quantities are not identically zero is a necessary condition to prove the existence of nearby periodic orbits (Birkhoff fixed point theorem). Moreover, the nonvanishing of the invariants provides also the stability of the spin-orbit resonances, since it guarantees the existence of invariant curves surrounding the periodic orbit.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011161605935
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  • 7
    Electronic Resource
    Electronic Resource
    A New ADI Scheme for Solving Three-Dimensional Parabolic Equations with First-Order Derivatives and Variable Coefficients (2000)
    Springer
    Journal of computational analysis and applications 2 (2000), S. 293-308 
    Details
    ISSN: 1572-9206
    Keywords: parabolic equations ; ADI scheme ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract An ADI scheme for solving three-dimensional parabolic equations withfirst-order derivatives and variable coefficients has been developed basedon our previous papers and the idea of the modified upwind differencescheme. This ADI scheme is second-order accurate and unconditionallystable. Further, a small parameter can be chosen which makes it suitablefor simulating fast-transient phenomena or for computations on fine spatialmeshes. The method is illustrated with numerical examples.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1010108620966
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  • 8
    Electronic Resource
    Electronic Resource
    A Multiclass Feedback Queueing Network with a Regular Skorokhod Problem (2000)
    Springer
    Queueing systems 36 (2000), S. 327-349 
    Details
    ISSN: 1572-9443
    Keywords: multiclass networks ; networks with feedback ; Skorokhod Problem ; Skorokhod Mapping ; Lipschitz continuity ; stability ; load conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider a four-class two-station network with feedback, with fluid inputs and a head-of-the-line generalized processor sharing discipline at each station. We derive the Skorokhod Problem associated with the network and obtain algebraic sufficient conditions for Lipschitz continuity of the associated Skorokhod Map. This provides the first example of a multiclass network with feedback for which the associated Skorokhod Problem has been proved to be regular. As an elementary application, we show that under the conditions which guarantee Lipschitz continuity the network is stable if and only if the usual load conditions apply.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011037419624
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  • 9
    Electronic Resource
    Electronic Resource
    Bifurcation Phenomena from Standing Pulse Solutions in Some Reaction-Diffusion Systems (2000)
    Springer
    Journal of dynamics and differential equations 12 (2000), S. 117-167 
    Details
    ISSN: 1572-9222
    Keywords: singular perturbation ; standing pulses ; stability ; Hopf bifurcation ; reaction-diffusion system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract Bifurcation phenomena from standing pulse solutions of the problem $$\varepsilon \tau u_t = \varepsilon ^2 u_{xx} + f(u,v),{\text{ }}v_t = v_{xx} + g(u,v)$$ is considered. ε(〉0) is a sufficiently small parameter and τ is a positive one. It is shown that there exist two types of destabilization of standing pulse solutions when τ decreases. One is the appearance of travelling pulse solutions via the static bifurcation and the other is that of in-phase breathers via the Hopf bifurcation. Furthermore which type of destabilization occurs first with decreasing τ is discussed for the piecewise linear nonlinearities f and g.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009098719440
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  • 10
    Electronic Resource
    Electronic Resource
    Physical aging of epoxy resin blended with poly(ether sulfone): Effect of poly(ether sulfone) molecular weight (2000)
    Springer
    Journal of polymer research 7 (2000), S. 257-266 
    Details
    ISSN: 1572-8935
    Keywords: Poly(ether sulfone) ; Epoxy resin ; Physical aging ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The physical aging process of 4-4′-diaminodiphenylsulfone (DDS) cured diglycidyl ether bisphenol-A (DGEBA) blended with various molecular weights of poly(ether sulfone) (PES; Mn = 28,600, 10,600, and 6,137) was studied by DSC. For DGEBA/DDS system blended with a low MW PES-3 (Mn = 6,137), no phase separation of the polymer blend and only one enthalpic relaxation process due to physical aging was observed. Since the high MW PES-1 (Mn = 28,600) had a Tg close to that of fully cured DGEBA/DDS, the fully cured DGEBA/DDS/PES-1 blend had a broader glass transition than a neat DGEBA/DDS system. However, the DSC results showed two enthalpic relaxation processes due to the physical aging of PES-rich and cured epoxy-rich phases as the material was aged at 155 °C (30 °C below Tg). Since the Tgs of PES-1-rich and epoxy-rich phases overlapped with each other, the enthalpic relaxation processes corresponding to each phase coupled to each other in the earlier stage of physical aging. The medium MW PES-2 (Mn = 10,600) has a much lower Tg than that of fully cured DGEBA/DDS, two well separated Tgs were observed for the cured DGEBA/DDS/PES-2 blend, indicating the cured epoxy was immiscible with PES. Aging the polymer blend at 155 °C (24 °C below Tg1 of the PES-2-rich phase and 53 °C below Tg2 of the epoxy-rich phase) produced two well separated relaxation processes due to PES-2-rich and epoxy-rich phases. The experimental results suggested that aging the polymer blend at a suitable temperature would improve the phase separation between PES-1-rich and epoxy-rich phases.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s10965-006-0128-6
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  • 11
    Electronic Resource
    Electronic Resource
    Activity and stability of Cu/ZnO/Al2O3 catalyst promoted with B2O3 for methanol synthesis (2000)
    Springer
    Catalysis letters 68 (2000), S. 55-58 
    Details
    ISSN: 1572-879X
    Keywords: promoting effect ; B2O3 ; Cu/ZnO/Al2O3 catalyst ; methanol synthesis ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The addition of B2O3 to a Cu/ZnO/Al2O3 catalyst increased the activity of the catalyst for methanol synthesis after an induction period during the reaction. The stability of the B2O3-containing Cu/ZnO/Al2O3 catalyst was greatly improved by the addition of a small amount of colloidal silica to the catalyst.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019010831562
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  • 12
    Electronic Resource
    Electronic Resource
    Stability and excitation of potassium promoter in iron catalysts – the role of KFeO2 and KAlO2 phases (2000)
    Springer
    Catalysis letters 67 (2000), S. 129-134 
    Details
    ISSN: 1572-879X
    Keywords: potassium desorption ; stability ; excitation ; iron catalyst ; Rydberg atoms
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Well‐characterized catalyst model compounds of KAlO2 and KFeO2 are investigated by thermal desorption of potassium from the material. The desorbing fluxes of ions, atoms and highly excited states (field ionizable Rydberg states) were studied with surface and field ionization detectors in a vacuum apparatus. From the Arrhenius plots the activation energies for desorption of K and K+ were determined. The chemical state of potassium at the surfaces is concluded to be: ionic on KAlO2 (with the K desorption barrier of 1.76 eV) and covalent on KFeO2 (barrier of 2.73 eV). These results agree with the data obtained earlier for industrial catalysts for ammonia and styrene production. They are interpreted in terms of the Schottky cycle, which is completed for KAlO2 and fails for KFeO2. This failure indicates a non‐equilibrium desorption process. K Rydberg states are only found to desorb from KFeO2, in agreement with the suggestion that such states in some way are responsible for the catalytic activity.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019013504729
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  • 13
    Electronic Resource
    Electronic Resource
    Stability of Linear Inequality Systems Measured by the Hausdorff Metric (2000)
    Springer
    Set-valued analysis 8 (2000), S. 253-266 
    Details
    ISSN: 1572-932X
    Keywords: Hausdorff metric ; linear inequality systems ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we propose a Hausdorff metric to measure the “distance” between two linear inequality systems on a real normed space X. For this topology, which comes through a pseudo-metric in the set Σ of linear inequality systems, the closedness of the feasible set mapping is studied, and at the same time a characterization of the stability of the subset Σ c of consistent sytems is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008701026782
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  • 14
    Electronic Resource
    Electronic Resource
    Stability Properties of a Bond Portfolio Management Problem (2000)
    Springer
    Annals of operations research 99 (2000), S. 251-265 
    Details
    ISSN: 1572-9338
    Keywords: stochastic programming ; bond portfolio management ; interest ratescenarios ; stability ; sensitivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Economics
    Notes: Abstract The bond portfolio management problem is formulated as a multiperiod two-stage or multistage stochastic program based on interest rate scenarios. These scenarios depend on the available market data, on the applied estimation and sampling techniques, etc., and are used to evaluate coefficients of the resulting large scale mathematical program. The aim of the contribution is to analyze stability and sensitivity of this program on small changes of the coefficients – the (scenario dependent) values of future interest rates and prices. We shall prove that under sensible assumptions, the scenario subproblems are stable linear programs and that also the optimal first-stage decisions and the optimal value of the considered stochastic program possess acceptable continuity properties.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1019275817688
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  • 15
    Electronic Resource
    Electronic Resource
    Destabilization for quasivariational inequalities of reaction-diffusion type (2000)
    Springer
    Applications of mathematics 45 (2000), S. 161-176 
    Details
    ISSN: 1572-9109
    Keywords: reaction-diffusion system ; unilateral conditions ; quasivariational inequality ; Leray-Schauder degree ; eigenvalue ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We consider a reaction-diffusion system of the activator-inhibitor type with unilateral boundary conditions leading to a quasivariational inequality. We show that there exists a positive eigenvalue of the problem and we obtain an instability of the trivial solution also in some area of parameters where the trivial solution of the same system with Dirichlet and Neumann boundary conditions is stable. Theorems are proved using the method of a jump in the Leray-Schauder degree.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1023033910657
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  • 16
    Electronic Resource
    Electronic Resource
    Diagonally implicit Runge–Kutta methods for 3D shallow water applications (2000)
    Springer
    Advances in computational mathematics 12 (2000), S. 229-250 
    Details
    ISSN: 1572-9044
    Keywords: numerical analysis ; shallow water problems ; DIRK methods ; stability ; 65L06 ; 65L20 ; 65M12 ; 65M20
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract We construct A‐stable and L‐stable diagonally implicit Runge–Kutta methods of which the diagonal vector in the Butcher matrix has a minimal maximum norm. If the implicit Runge–Kutta relations are iteratively solved by means of the approximately factorized Newton process, then such iterated Runge–Kutta methods are suitable methods for integrating shallow water problems in the sense that the stability boundary is relatively large and that the usually quite fine vertical resolution of the discretized spatial domain is not involved in the stability condition.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1018969203026
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  • 17
    Electronic Resource
    Electronic Resource
    On the Robustness of Gaussian Elimination with Partial Pivoting (2000)
    Springer
    BIT 40 (2000), S. 62-73 
    Details
    ISSN: 1572-9125
    Keywords: Gaussian elimination ; stability ; pivoting
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract It has been recently shown that large growth factors might occur in Gaussian Elimination with Partial Pivoting (GEPP) also when solving some plausibly natural systems. In this note we argue that this potential problem could be easily solved, with much smaller risk of failure, by very small (and low cost) modifications of the basic algorithm, thus confirming its inherent robustness. To this end, we first propose an informal model with the goal of providing further support to the comprehension of the stability properties of GEPP. We then report the results of numerical experiments that confirm the viewpoint embedded in the model. Basing on the previous observations, we finally propose a simple scheme that could be turned into (even more) accurate software for the solution of linear systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022314201484
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  • 18
    Electronic Resource
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    Runge-Kutta Methods for the Numerical Solution of Stiff Semilinear Systems (2000)
    Springer
    BIT 40 (2000), S. 611-639 
    Details
    ISSN: 1572-9125
    Keywords: Runge-Kutta methods ; stability ; convergence ; stiff problems
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper studies the stability and convergence properties of general Runge-Kutta methods when they are applied to stiff semilinear systems y′(t) = J(t)y(t) + g(t, y(t)) with the stiffness contained in the variable coefficient linear part. We consider two assumptions on the relative variation of the matrix J(t) and show that for each of them there is a family of implicit Runge-Kutta methods that is suitable for the numerical integration of the corresponding stiff semilinear systems, i.e. the methods of the family are stable, convergent and the stage equations possess a unique solution. The conditions on the coefficients of a method to belong to these families turn out to be essentially weaker than the usual algebraic stability condition which appears in connection with the B-stability and convergence for stiff nonlinear systems. Thus there are important RK methods which are not algebraically stable but, according to our theory, they are suitable for the numerical integration of semilinear problems. This paper also extends previous results of Burrage, Hundsdorfer and Verwer on the optimal convergence of implicit Runge-Kutta methods for stiff semilinear systems with a constant coefficients linear part.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1022332200092
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  • 19
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    Stochastic Methods for Ill-Posed Problems (2000)
    Springer
    BIT 40 (2000), S. 226-240 
    Details
    ISSN: 1572-9125
    Keywords: Stochastic differential equations ; regularisation ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract This paper is devoted to the numerical analysis of ill-posed problems of evolution equations in Banach spaces using certain classes of stochastic one-step methods. The linear stability properties of these methods are studied. Regularisation is given by the choice of the regularisation parameter as α = $$\sqrt {\tau _n }$$ , where τ n is the stepsize and provides the convergence on smooth initial data. The case of the approximation of well-posed problems is also considered.
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    URL: http://dx.doi.org/10.1023/A:1022386822865
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  • 20
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    Hydraulic analysis of free-surface flows with solidification (2000)
    Springer
    Archive of applied mechanics 70 (2000), S. 17-29 
    Details
    ISSN: 1432-0681
    Keywords: Key words free-surface flow ; solidification ; strip casting ; steady state ; nonuniqueness ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Summary The paper is concerned with a one-dimensional analysis of plane open-channel flow with continuous solidification. The process is of relevance for recent developments in the casting of steel and other metals. The bottom of the channel consists of a rotating casting roll and a horizontal cooling table, where the solidified material is withdrawn with given velocity. The study is restricted to the region downstream of the top of the casting roll. Surface tension is neglected. In the main part of the analysis inviscid fluid flow is considered since the Reynolds number is very large in the applications. It is found that the steady-state solutions are nonunique in a certain parameter range. In addition to a continuous solution, there are two solutions including hydraulic jumps, with one hydraulic jump being located on the casting roll, the other one on the cooling table. Regarding the stability of the non unique solutions, the evolution of disturbances is investigated numerically as an initial-value problem. It is concluded that the hydraulic jump on the cooling table is unstable, while the other discontinuous solution as well as the continuous solution are stable for sufficiently small disturbances. Which stable solution is attained in the steady state, depends on the history of the process. Friction at the liquid/solid interface is taken into account in the last part of the analysis. A constant friction coefficient is assumed. It is found that the history of the process determines the steady-state solution if, and only if, the friction coefficient is sufficiently small. For larger values of the friction coefficient, the steady-state solution is unique and independent of the history of the transient process. Furthermore, for sufficiently large friction coefficients, stable hydraulic jumps are found, in contrast to the inviscid case, also on the cooling table.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/s004199900031
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  • 21
    Electronic Resource
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    Concerning a Technique for Increasing Stability of Climbing Robots (2000)
    Springer
    Journal of intelligent and robotic systems 27 (2000), S. 195-209 
    Details
    ISSN: 1573-0409
    Keywords: wall-climbing robot ; electromagnetic grippers ; stability ; additional support element ; sliding and turning over conditions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science , Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract Legged-climbing robot is considered. Each foot of the robot has an electromagnet system for robot"s holding on a metal surface. This surface can be both vertical and inclined, including negative slope. Analytical calculation of robot stability under turn over or sliding conditions has been made. Critical slopes have been determined. One of these slopes corresponds to minimal reserve of robot stability towards sliding and another to minimal reserve of robot stability towards turning-over. As total reserve of stability of a robot is always equal to the minimal one of these reserves. Additional support elements of elastic material with high coefficient of friction, along with electromagnet, allows to increase minimal reserve of robot stability towards sliding. The use of such support elements leads to redistributing force of normal support reaction between electromagnet (which surface has low coefficient of friction) and additional support element (which surface has high coefficient of friction). It is just what leads to increasing the total friction force and as a consequence to increasing of minimal reserve of robot stability towards sliding.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008158332368
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  • 22
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    Perron–Frobenius Theory and Symmetry of Solutions to Nonlinear PDE's (2000)
    Springer
    Letters in mathematical physics 53 (2000), S. 313-320 
    Details
    ISSN: 1573-0530
    Keywords: partial differential equations ; nonlinearities ; symmetries ; stability ; minimization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics , Physics
    Notes: Abstract We suggest a simple but general method of establishing symmetry properties of stable solutions of nonlinear elliptic equations. The method relies on characterization of symmetry breaking with a help of zero modes and on a generalization of the Perron–Frobenius theory.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007622208894
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    Stability of Attractive Bose–Einstein Condensates (2000)
    Springer
    Journal of statistical physics 101 (2000), S. 731-746 
    Details
    ISSN: 1572-9613
    Keywords: attractive Bose–Einstein condensates ; nonlinear Schrödinger equation ; stability ; ground state ; variational arguments
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We propose the critical nonlinear Schrödinger equation with a harmonic potential as a model of attractive Bose–Einstein condensates. By an elaborate mathematical analysis we show that a sharp stability threshold exists with respect to the number of condensate particles. The value of the threshold agrees with the existing experimental data. Moreover with this threshold we prove that a ground state of the condensate exists and is orbital stable. We also evaluate the minimum of the condensate energy.
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    URL: http://dx.doi.org/10.1023/A:1026437923987
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    A screen of yeast respiratory mutants for sensitivity against the mycotoxin citrinin identifies the vacuolar ATPase as an essential factor for the toxicity mechanism (2000)
    Springer
    Current genetics 37 (2000), S. 227-284 
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    ISSN: 1432-0983
    Keywords: Key words Citrinin ; Pet mutants ; Mitochondrial biogenesis ; Vacuolar ATPase ; YKL118W disruption ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In countries with a hot climate the mycotoxin citrinin represents a serious problem in fungal food-poisoning. In humans the renal system is affected the most and the mitochondrial respiratory chain was identified as a possible sensitive target for this toxin. In addition, citrinin has an antifungal activity that also inhibits the growth of the yeast Saccharomyces cerevisiae. So far the precise mode of action and the subcellular targets for citrinin have not been identified. Therefore, we decided to use the model organism yeast for a genetic approach to identify genes that play a role in the sensitivity against this mycotoxin. A large collection of conditional respiratory deficient yeast mutants was screened for sensitivity against citrinin. One special pet-ts mutant was identified that exhibited a higher sensitivity against citrinin. The genetic system of yeast allowed the isolation of the respective wild-type gene. This yeast gene encodes the Vph2p subunit that is essential for the correct assembly of the vacuolar ATPase. Isolation of the mutated gene and gene-disruption experiments of VPH2 and the partially overlapping small YKL118W gene verified this finding. The wild-type VPH2 gene restores all defects of the mutants. In contrast to this, YKL118W gave no complementation and the null mutant showed no phenotype. Thereby the yeast vacuolar ATPase was found to be important for the toxic effect of citrinin in yeast cells. The consequences of this finding for the molecular mechanism of citrinin action and its relation to the mitochondrial respiratory chain are discussed.
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    URL: http://dx.doi.org/10.1007/s002940070001
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    POL32, a subunit of the Saccharomyces cerevisiae DNA polymerase δ, defines a link between DNA replication and the mutagenic bypass repair pathway (2000)
    Springer
    Current genetics 38 (2000), S. 178-187 
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    ISSN: 1432-0983
    Keywords: Key wordsPOL32 ; SRS2 ; DNA repair ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Pol32 is a subunit of Saccharomyces cerevisiae DNA polymerase δ required in DNA replication and repair. To gain insight into the function of Pol32 and to determine in which repair pathway POL32 may be involved, we extended the analysis of the pol32Δ mutant with respect to UV and methylation sensitivity, UV-induced mutagenesis; and we performed an epistasis analysis of UV sensitivity by combining the pol32Δ with mutations in several genes for postreplication repair (RAD6 group), nucleotide excision repair (RAD3 group) and recombinational repair (RAD52 group). These studies showed that pol32Δ is deficient in UV-induced mutagenesis and place POL32 in the error-prone RAD6/REV3 pathway. We also found that the increase in the CAN1 spontaneous forward mutation of different rad mutators relies entirely or partially on a functional POL32 gene. Moreover, in a two-hybrid screen, we observed that Pol32 interacts with Srs2, a DNA helicase required for DNA replication and mutagenesis. Simultaneous deletion of POL32 and SRS2 dramatically decreases cellular viability at 15 °C and greatly increases cellular sensitivity to hydroxyurea at the permissive temperature. Based on these findings, we propose that POL32 defines a link between the DNA polymerase and helicase activities, and plays a role in the mutagenic bypass repair pathway.
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    URL: http://dx.doi.org/10.1007/s002940000149
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    Endopolygalacturonase genes and enzymes from Saccharomyces cerevisiae and Kluyveromyces marxianus (2000)
    Springer
    Current genetics 38 (2000), S. 264-270 
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    ISSN: 1432-0983
    Keywords: Key words Endopolygalacturonase ; Saccharomyces cerevisiae ; Kluyveromyces marxianus ; Pectinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gene encoding endopolygalacturonase (EC 3.2.1.15) has been cloned, sequenced and expressed from three strains of Saccharomyces cerevisiae (including non-secretors) and three strains of Kluyveromyces marxianus. Both control and coding regions showed small differences within each species, one including loss of a potential glycosylation site. Two non-secreting S. cerevisiae strains (FY1679 and var. uvarum) had non-transcribed copies of functional genes. Maximum enzyme activity was achieved with the S. cerevisiae FY1679 gene in an expressing vector, with an enzyme activity of 51 μmol of reducing sugar released from polygalacturonic acid μg protein−1 min−1, the highest so far reported for a yeast.
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    URL: http://dx.doi.org/10.1007/s002940000160
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    Recessive mutations in SUP35 and SUP45 genes coding for translation release factors affect chromosome stability in Saccharomyces cerevisiae (2000)
    Springer
    Current genetics 37 (2000), S. 285-291 
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    ISSN: 1432-0983
    Keywords: Key words Translation release factors ; Chromosome stability ; Microtubules ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Chromosome stability in suppressor mutants for SUP35 and SUP45 genes coding for translation release factors was studied. We obtained spontaneous and UV-induced sup35 or sup45 mutants in a haploid strain disomic for chromosome III and tested the stability of an extra copy of this chromosome. The majority of the mutants showed increased chromosome instability. This phenotype was correlated with an increased sensitivity to the microtubule-poisoning drug benomyl which affects chromosome segregation at anaphase. Our data suggest that termination-translation factors eRF3 and eRF1 control chromosome transmission at mitotic anaphase in Saccharomyces cerevisiae.
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    URL: http://dx.doi.org/10.1007/s002940050529
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    Structure and Morphology of a Polyether/Polyacrylate Semi-interpenetrating Polymer Network (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 83-92 
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    ISSN: 1572-8943
    Keywords: cationic and photoinitiated polymerization ; DSC ; interfacial mixing ; interpenetrating polymer network (IPN) ; glass transition temperature ; NMR ; quantitative thermal analysis of phases ; reactive epoxy and acrylate systems ; Tg broadening
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study NMR and DSC are used to probe the structure, thermal characteristics and morphology of a network formed from a diepoxide/acrylate system. Separate chemistries are employed to polymerize the diepoxide and acrylate components. The cationic polymerization of the diepoxide exhibits excellent selectivity in producing a crosslinked polyether network without affecting the acrylate monomer. Subsequent photoinitiated free-radical polymerization of the acrylate produces a phase separated, semi-interpenetrating polymer network (SIPN).
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    URL: http://dx.doi.org/10.1023/A:1010123610324
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    A DSC Study on Cure Kinetics of HTPB-IPDI Urethane Reaction (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 93-100 
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    ISSN: 1572-8943
    Keywords: catalyst ; cure kinetics ; DSC ; HTPB ; kinetic compensation effect ; urethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The kinetics of theurethane-forming cure reaction of hydroxyl terminated polybutadiene (HTPB) with isophorone diisocyanate (IPDI) in presence of ferric tris (acetyl acetonate) (FeAA) catalyst was investigated using differential scanning calorimetry (DSC). The Arrhenius activation parameters, viz., activation energy E and pre-exponential factor A were evaluated using the non-isothermal integral Coats-Redfern equation. The cure reaction was catalysed by ferric acetyl acetonate (FeAA), as revealed from the decrease in reaction temperatures and the increase in rate constants; however, the computed activation energy did not show any correlation to the catalyst concentration. The values of E and A for the uncatalysed reaction at different heating rates showed interdependence through kinetic compensation (KC) effect. Using KC correction, E values were normalised for the value of A for the uncatalysed reaction under identical conditions. The normalised E values decreased exponentially with increase in concentration of FeAA, showing high propensity of the HTPB-IPDI system for catalysis.
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    The Effect of Side Chain Association on Thermal and Viscoelastic Properties: Cellulose acetate based polycaprolactones (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 157-168 
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    ISSN: 1572-8943
    Keywords: cellulose acetate ; DSC ; glass transition ; melting ; polycaprolactone
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cellulose acetate-based polycaprolactones (CAPCL's) were synthesized by the polymerization of ε-caprolactone which was initiated by non-substituted OH group in cellulose acetate. The CL/OH (mol mol−1) ratios of the CAPCL's were changed from 2 to 20. Thermal and viscoelastic properties of the CAPCL sheets were studied by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Glass transition, cold crystallization and melting were determined by DSC. Dynamic modules (E'), dynamic loss modules (E'') and tanδ were measured in a temperature range from −150 to 50°C by DMA. Apparent activation energy of a dispersion was calculated from the frequency dependency of E'' peak temperature. It was found that the main chain motion of both CA and PCL is observed in a CL/OH ratio from 0 to 10 mol mol−1. However, when CL/OH ratio exceeds 10 mol mol−1, the crystalline region which is rearranged by the PCL chain association is observed and only the main chain motion of PCL can be detected.
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    Structural Development During Thermal Fractionation of Polyethylenes (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 245-255 
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    ISSN: 1572-8943
    Keywords: DSC ; metallocene ; polyethylenes ; SAXS ; synchrotron radiation ; thermal fractionation ; WAXD ; Ziegler-Natta
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this study, the stepwise isothermal crystallization or thermal fractionation of Ziegler—Natta and metallocene based polyethylenes (ZN-PE and m-PE) with two kinds of branch lengths (ethyl and hexyl) and branch compositions were studied using simultaneous synchrotron small-angle X-ray scattering (SAXS)/wide-angle X-ray diffraction (WAXD) and differential scanning calorimetry (DSC). The crystal long period and the invariant were determined by SAXS, and the variations of crystal unit cell parameters and the degree of crystallinity were determined by WAXD. The arithmetic mean length (Ln), the weightedmean length (Lw) and the broadness index (Lw/Ln) of the studied polyethylenes were previously determined by DSC. Results from these studies were interpreted using the model of branch exclusion, which affects the ability of the chain-reentry into the crystal phase. Multiple SAXS peaks and step-change in crystallinity change (WAXD) were seen during heating, which corresponded well with the crystal thickness distribution induced by stepwise crystallization. The effects of the heterogeneity of the 1-olefin branch length and the distribution on the crystal long period and the invariant as well as the degree of crystallinity were discussed.
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    Applications of Successive Self-Nucleation and Annealing (SSA) to Polymer Characterization (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 451-470 
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    ISSN: 1572-8943
    Keywords: annealing ; DSC ; self-nucleation ; SSA ; thermal fractionation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A new technique to thermally fractionate polymers using DSC has been recently developed in our laboratory. The applications of the novel successive self-nucleation and annealing (SSA) technique to characterize polyolefins with very dissimilar molecular structures are presented as well as the optimum conditions to thermally fractionate any suitable polymer sample with SSA. For ethylene/α-olefin copolymers, the SSA technique can give information on the distribution of short chain branching and lamellar thickness. In the case of functionalized polyolefins, detailed examinations of SSA results can help to establish possible insertion sites of grafted molecules. The application of the technique to characterize crosslinked polyethylene and crystallizable blocks within ABC triblock copolymers is also presented.
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    Nucleating Agents in Polypropylene (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 497-508 
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    ISSN: 1572-8943
    Keywords: Avrami equation ; crystallization ; dibenzylidene sorbitol ; DSC ; isothermal kinetics ; nucleating agents ; nucleation ; pine crystal ; polypropylene
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of nucleating agents such as dibenzylidene sorbitol (DBS) (a derivative of sorbitol), pine crystal 1500, sodium and potassium benzoates in commercial grade isotactic polypropylene iPP are studied using differential scanning calorimetry (DSC). Isothermal crystallization kinetics of polypropylene to the alpha phase have been analyzed using Avrami's model. Results indicate that dibenzylidene sorbitol and pine crystal are very effective in increasing the crystallization temperature of the polymer and number of nuclei formed during crystallization.
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    Thermal Analysis Characterization of a Commercial Thermoplastic/Thermoset Adhesive (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 559-570 
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    ISSN: 1572-8943
    Keywords: adhesive ; composition analysis ; curing kinetics ; DMA ; DSC ; TGA ; thermal cure ; thermoplastic/thermoset blend
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC, TGA and DMA thermal analysis techniques are used to characterize a complex adhesive blend. The chemical and thermomechanical property development shown to follow a two-stage process. Beneficial synergy between these analysis tools is demonstrated in this study.
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    Anomalies of Glass Transition: Manifestation in fullerene core polystyrene stars (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 23-31 
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    ISSN: 1572-8943
    Keywords: DSC ; fullerene ; glass transition ; star-like polystyrene ; segmental dynamics
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Segmental dynamics around Tg in the 4- and 6-arm fullerene (C60) core star-like polystyrenes with different preset arm lengths was studied by DSC as compared to that in the linear PS and PS/C60 blend. The ‘anomalies’ in glass transition behavior were found for the stars including both suppression and facilitation of segmental motion, and pronounced dynamic heterogeneity within a transition range. The results are interpreted in terms of breakdown of intermolecular cooperativity of segmental motions and PS-C60 interactions.
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    Yeast Intracellular Water Determination by Thermogravimetry (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 643-648 
    Details
    ISSN: 1572-8943
    Keywords: drying ; intracellular water ; Saccharomyces cerevisiae ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The intracellular water content of a microorganism is an important parameter which is a determinant factor of its physiological properties. It is usually measured by complex and time consuming procedures. Thermogravimetry using infrared balance has been used for this purpose, through the identification of different drying steps occurring during the analysis. This work employs the same method with much smaller samples, using conventional thermogravimetric equipment in a simpler and faster way than other conventional procedures. Commercial yeast (Saccharomyces cerevisiae ) washed samples are analyzed in isothermal procedures which are run in about 30 min. The drying rate curve, when plotted as a function of the residual mass of the cells, allows the identification of the step where the intracellular water is lost and the determination of its content. The obtained values, on extracellular water free basis, are in the range of 65 to 69% and agree with those measured by other techniques.
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    Synthesis And Kinetic Analysis of Poly(2,2'-dymethoxy-4,4'-biphenylenevinylene. A novel conducting polymer (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 675-680 
    Details
    ISSN: 1572-8943
    Keywords: conducting polymer ; DSC ; kinetic analysis ; PPV ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The title polymer was obtained electrochemically by the reduction of 4,4'-bis(dibromomethyl)-2,2'-dimethoxybiphenyl under very smooth conditions. The DSC and TG/DTG curves registered at four different heating rates showed that the polymer is stable in air up to 150°C, where smooth degradation starts. Above 300°C, decomposition is fast and exothermic (ΔH= –323 J g–1) . The activation energy (116±4 kJ mol–1 ) was determined by Ozawa's method.
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    Relaxation Transitions in Thermally Treated Polyaniline Films (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 721-727 
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    ISSN: 1572-8943
    Keywords: ageing ; annealing ; DSC ; polyaniline ; relaxation transition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermally treated films of polyaniline-emeraldine base (PANI-EB) cast from NMP solution were studied by using differential scanning calorimetry. Dependence of the thermodynamic parameters of the relaxation transitions on temperature and annealing period as well as the effect of the thermal history of the samples upon the crosslinking processes were investigated. For the first time DSC analysis of PANI-EB films after prolonged ageing was performed. It was found that relaxation transitions can be registered only for crosslinked PANI-EB. The crosslinking processes proceed both upon short-time heating of the polymer studied over80°C and during long-time storage at room temperature.
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    DSC and FTIR Analyses of The Curing Behavior of Epoxy/dicy/solvent Systems on Hermetic Specimens (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 711-719 
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    ISSN: 1572-8943
    Keywords: cure ; dicyandiamide ; DSC ; epoxy ; hermetic ; solvent
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The curing characteristics of adicyandiamide-cured epoxy system under the influence of solvents in a closed environment were studied by means of isothermal differential scanning calorimetry (DSC) and Fourier transform infrared spectroscopy (FTIR). The DSC analyses revealed that the presence of solvent results in decreases in the curing exotherm, the initial curing rate, the glass transition temperature, the reaction rate and the reaction order of the epoxy resin. The greatest decreases were caused by the solvent with the highest boiling temperature. A change in temperature-dependent curing route due to the heat absorbed during solvent evaporation is responsible for the difference. The FTIR analyses confirmed that the composition of the cured resin is affected by the solvent, the curing temperature and the specimen configuration. As compared with those obtained from open systems, specimens produced in a closed environment have an enhanced curing exotherm, initial curing rate, glass transition temperature, reaction rate and reaction order because of the retention of volatile catalytic by-products.
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    The Effects of γ-Irradiation on the Electrokinetic and Thermal Behaviour of Zirconium Hydroxide (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 837-846 
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    ISSN: 1572-8943
    Keywords: DSC ; γ-irradiation ; laser Raman ; microelectrophoresis ; XRD ; zeta-potential ; zirconium hydroxide ; ZrO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Zirconium hydroxide particles produced by rapid precipitation at pH 10.4, 7 or 2 were subjected toγ-irradiation up to a final dose of 20 MGy. The effects of the γ-irradiation were examined by X-ray powder diffraction, laser Raman spectroscopy, differential scanning calorimetry and microelectrophoretic measurements. It was found that γ-irradiation had no influence on the behaviour of zirconium hydroxide during calcination and subsequent cooling. The results of microelectrophoretic measurements showed that γ-irradiation influences the surface properties of zirconium hydroxide as a function of the precipitation pH. Zirconium hydroxide precipitated at pH 2 proved to be the most susceptible to γ-irradiation, while the sameγ-irradiation had very little (if any) effect on the surface properties of zirconium hydroxide precipitated at pH 10.5. After γ-irradiation, the electrophoretic mobility of zirconium hydroxide precipitated at pH 2 was increased at both low and high pH, thereby indicating an increase in its adsorption capacity. The analogy observed between the pH-dependence of the effects of γ-irradiation on the electrokinetic behaviour of zirconium hydroxide and the influence of ball-milling on the thermal behaviour of zirconium hydroxide [8] suggested that the susceptibility of amorphous zirconium hydroxide increases with decrease of the precipitation pH.
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    Differential Scanning Calorimetric Analysis of Composted Materials From Different Sources (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 607-614 
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    ISSN: 1572-8943
    Keywords: composted materials ; DSC ; thermal characterization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential scanning calorimetry (DSC) was applied to the study of material composted from sawdust, used coffee, farmyard manure and the organic fraction of domestic solid waste. Composting trials were carried out in Morocco and samples were collected after different periods of composting. The results obtained provided evidence that sawdust substrate is not a suitable source for composting due to the high content of lignin; samples from used coffee are characterized by a degree of aromaticity that is lower and a functional group heterogeneity that is higher than those of organic wastes from manure and the organic fraction of domestic wastes. The latter organic waste substrates appear to be easily degraded and humified and to give DSC curves that at the end of composting are vary close to those of native soil humic acids.
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    Thermal Analysis of a Polyethylene Glycol (PEG 4000): T-CR-T Diagram Construction (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 711-718 
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    ISSN: 1572-8943
    Keywords: DSC ; PEG ; T-CR-T
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract A modified isoconversional method is applied to perform the kinetic analysis of non-isothermal processes. The solidification process of a polyethylene glycol with a mean molecular of 4000 (PEG 4000) was here analyzed. It was stated that the Avrami model provides a good description of the solidification process. Temperature-cooling rate-transformation diagrams were constructed and there was a good agreement between experimental data and the calculated T-CR-T curves. Moreover, morphological qualitative analysis has been performed by means of scanning electron microscopy.
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    Thermoanalytical Study of O,O'-Dibenzoyl-(2R,3R)-Tartaric Acid Supramolecular Compounds. Part I. Investigation of compounds with water, achiral alcohols and phenols (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 745-755 
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    ISSN: 1572-8943
    Keywords: chiral complex ; DSC ; hydrate ; optical resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal behaviour of O,O'-dibenzoyl-(2R,3R)-tartaric acid (DBTA), its monohydrate, and its potential supramolecular compounds with achiral alcohols and phenols were investigated with TG, DSC, EGD. The structural differences among the anhydrous DBTA, its monohydrate, and the supramolecular derivatives were investigated with X-ray powder diffraction. The thermal behaviour of DBTA-supramoleculars with isopropyl, tert-butyl, and 5-cyclohexyl alcohols is found to be similar to each other but essentially different from that of both DBTA and its monohydrate. On heating they melt and decompose between 60–180°C while they loose in one or two steps the bound alcohol. The thermal stability of the supramolecular compounds increases with the boiling point of the alcohol component. According to the X-ray powder diffraction patterns each supramolecular substance has different structure, that may also result in the different thermal stability of the compounds. The molar ratio of DBTA:achiral alcohol samples is 1:1.01–1:1.57 estimated from the corresponding mass losses. The XRD patterns of the prepared two DBTA-phenol materials are different from those of DBTA-achiral alcohol samples. The phenol compounds melt with slow mass losses and give an endothermic peak between 73–83°C but the melting point of the anhydrous DBTA cannot be observed. DBTA:phenol molar ratio is estimated to be 1:0.41 and 1:0.65 for phenol and 2-methylphenol, respectively.
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    Thermal Decomposition Characteristics of 1,7-Diazido-2,4,6-trinitrazaheptane and its Application in Propellants (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 771-778 
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    ISSN: 1572-8943
    Keywords: burning rate ; DATH ; DSC ; TG ; thermal decomposition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal decomposition characteristics of1,7-diazido-2,4,6-trinitrazaheptane (DATH) and multi-component systems containing DATH were studied by using DSC, TG and DTG techniques. Three –NO2 groups in the DATH molecule break away first from the main chain when DATH is heated up to 200°C. Following this process, the azido groups and the residual molecule decompose rapidly to release a great deal of heat within a short time. In the multi-component systems, DATH undergoes a strong interaction with the binder of the double-base propellant and a weak interaction with RDX. The burning rates of the two propellants were determined by using a Crawford bomb. The results showed that the burning rate rises by about 19–66% when 23.5%DATH is substituted for RDX in a minimum smoke propellant. Meanwhile, the N2 level in the combustion gases is enhanced, which is valuable for a reduction of the signal level of the solid propellant.
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    Analysis of DSC Data Relating to Proteins Undergoing Irreversible Thermal Denaturation (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 51-62 
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    ISSN: 1572-8943
    Keywords: DSC ; kinetic models ; protein denaturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract New approaches to the analysis of differential scanning calorimetry (DSC) data relating to proteins undergoing irreversible thermal denaturation have been demonstrated. The experimental approaches include obtaining a set of DSC curves at various scanning rates and protein concentrations, and also reheating experiments. The mathematical methods of analysis include construction of a linear anamorphosis and simultaneous fitting of a theoretical expression for the dependence of the excess heat capacity on temperature to a set of experimental DSC curves. Different kinetic models are discussed: the one-step irreversible model, the model including two consecutive irreversible steps, the Lumry and Eyring model with a fast equilibrating first step, and the whole kinetic Lumry and Eyring model.
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    URL: http://dx.doi.org/10.1023/A:1010102525964
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    DSC Studies on Melting and Crystallization of Polyamide 6/Biopol Blends (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 117-121 
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    ISSN: 1572-8943
    Keywords: biopol/polyamide 6 blends ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Blends obtained from Biopol D600G and polyamide 6 reveal in DSC investigations multiphase structure with a distinct crystalline polyamide 6 phase. Due to rapid crystallization of the polyamide 6 the crystallization of the Biopol D600G is retarded. The grade of crystallization of Biopol D600G is lower in the blends than in the pure state, as calculated from the melting enthalpies. Crystallization of polyamide 6 in the blends is faster and results in increasing of the grade of crystallization of polyamide 6 phase comparing to the unblended component.
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    Thermal Decomposition of Triazine Herbicides. I. 1,2-(4-chloro-6-ethylamino-1,3,5-triazin-2-ylamino)-2-methylpropionitrile (cyanazine) (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 103-110 
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    ISSN: 1572-8943
    Keywords: cyanazine ; DSC ; kinetics ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Cyanazine was taken as an example for investigations under the influence of different conditions on thermal decomposition of triazine herbicides. DSC measurements were carried out under atmospheric pressure and hermetically closed, under pressure 1.3 kPa. The influence of the pressure on the constant reaction rate of decomposition of cyanazine was discussed. It was also proved that the predicted reaction constant rates from isothermal and non-isothermal measurements are consistent.
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    Properties of Polyurethanes Based on Mesogenic Diol and 4,4'-methylenebis(cyclohexyl Isocyanate) (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 111-116 
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    ISSN: 1572-8943
    Keywords: DMTA ; DSC ; HMDI ; mesogenic chain extender ; polyurethane
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract New polyurethanes with mesogenic units in the main chain due to the use of a liquid crystalline chain extender were synthesized from 4,4'-methylenebis(cyclohexyl isocyanate) (HMDI)using diisocyanates of different trans, trans isomer content, a low molecular diol4,4'-bis(6-hydroxyhexoxy)biphenyl (BHHBP) and a high molecular poly(hexyleneadipate)diol (PHA). The growth of trans, trans isomer content in HMDI used to syntheses of PU induces monotonic growth of melting point, rectilinear growth of crystallization temperatures and the growth of crystallization enthalpy, both for hard segment polyurethanes and block polyurethanes. The increase of trans, trans isomer content in HMDI increases also glass transition temperatures and dynamic storage modulus of the polyurethanes.
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    Calorimetric and Thermal Investigation of Metal Derivatives of 6-aminopicolinic Acid (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 163-166 
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    ISSN: 1572-8943
    Keywords: comparison ; decomposition ; DSC ; enthalpy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The comparison of thermal and calorimetric properties of metal derivatives of 6-aminopicolinic acid (APH) is presented. The salts and complexes of APH with Cr(III), Cd(II), Cu(II), Ni(II), Pb(II), Co(II)and Ag(I) have been studied by TG-DTA and DSC methods up to 1200°C in a nitrogen atmosphere. Decomposition processes are proposed. The decarboxylation, deamination and carbonation of the organic fragments of molecules take place. The compounds decompose to metal or to metal oxides. The values of the transition enthalpy were determinated.
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    Physical Aging of a Tetrafunctional/phenol Novolac Epoxy Mixture Cured with Diamine. DSC and DMA measurements (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 391-399 
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    ISSN: 1572-8943
    Keywords: DMA ; DSC ; physical aging ; TGDDM epoxy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The physical aging of a system containing tetraglycidyl-4-4′-diaminodiphenylmethane (TGDDM), with a multifunctional novolac glycidyl ether resin hardened by 4,4′-diaminodiphenylsulphone (DDS) has been investigated by differential scanning calorimetry (DSC) and dynamic mechanical analysis (DMA). Samples fully cured were aged at temperatures between 200 and 250°C, during periods of time from 1 to a maximum of 336 h. Furthermore, the dynamic mechanical relaxation behaviour annealed at temperature of 220°C, was studied, aging during 24 and 168 h. The effect of the enthalpy relaxation during DSC heating scan is shown by the presence of an endothermic peak whose position and intensity depends on the aging conditions, both temperature and time. DSC studies suggest that enthalpy relaxation increases gradually with aging time to a limiting value for each temperature where structural equilibrium is reached. DMA results show that the effect of aging is to cause chain stiffening and a decrease in the height of the peak value of the loss factor.
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    Mechanism of Optical Resolutions Via Diastereoisomeric Salt Formation. Part 6 Thermoanalytical investigation of the optical resolution of racemic mandelic acid with S-(+)-2-benzylamino-butanol (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 409-415 
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    ISSN: 1572-8943
    Keywords: 2-benzylamino-butanol ; DSC ; mandelic acid ; melting phase diagram ; optical resolution
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The optical resolution of racemic mandelic acid (I) by S-2-benzylamino-butanol (II) was performed in water, ethyl acetate, and water saturated ethyl acetate. It was found that the efficiency of the resolution is three times higher in water saturated ethyl acetate than in either water or ethyl acetate. The salt mixtures produced during the resolutions and the pure diastereoisomeric salts were analyzed by TG, DSC and X-ray powder diffraction measurements. The R-(-)-I×S-(+)-II salt has the higher melting point and heat of fusion value which indicates that this is the more stable salt. Though the general assumption is that diastereoisomeric salt pairs of successful optical resolutions form eutectic systems, the R-mandelic acid-S-2-benzylamino-butanol and the S-mandelic acid-S-2-benzylamino-butanol system was found to behave in a different way. Melting did not start at or near the estimated eutectic temperature. The difference can be explained either by miscibility in the solid phase (solid solution) or by a blocked interaction between the crystals of the two solid salts. This unusual behaviour of the salt pair should be responsible for the unusual difference in the efficiency of the resolutions performed in different solvents
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    Physico-chemical Studies on Zinc Hexa(formato)ferrate(III) Decahydrate (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 535-539 
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    ISSN: 1572-8943
    Keywords: DSC ; ferrite ; Mössbauer spectra ; TG ; thermal decomposition ; zinc ferriformate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermal analysis of zinc hexa(formato)ferrate(III) decahydrate, Zn3 [Fe(HCOO)6]2 10H2O has been investigated up to 800°C in static air atmosphere employing TG, DSC, XRD, IR, ESR and Mössbauer spectroscopic techniques. After dehydration at 160°C, the anhydrous complex decomposes into α-Fe2 O3 and zinc carbonate in successive stages. Subsequently the cations remix to yield fine particles of zinc ferrite, ZnFe2 O4 , as a result of solid state reaction between α-Fe2 O3 and zinc carbonate at a temperature (600°C) much lower than for ceramic method.
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    Evaluation of Kinetic Data for Crystallization of Tio2 Prepared by Hydrolysis Method (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 595-604 
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    ISSN: 1572-8943
    Keywords: crystal structure ; DSC ; oxides ; X-ray diffraction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The formation of TiO2 prepared by hydrolysis method was presented. Thermodynamics and kinetics of anatase crystallization reaction were investigated. Differential method of kinetic data evaluation in non-isothermal conditions according toKissinger, Ozawa and Kazeev-Yerofeev was applied. Starting, crystallized and thermally treated powders were determined using X-ray powder diffraction analysis. The characteristic parameters (the activation energy, constant rate and formal kinetic order of reaction) of TiO2 formation were calculated using DSC data.
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    Anomalies in Heat Capacity Measurements of RuO2-TiO2 System (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 683-689 
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    ISSN: 1572-8943
    Keywords: DSC ; heat capacity ; mixed oxide TiO2-RuO2 ; RuO2 ; TiO2
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract DSC was used for heat capacity measurements of pure RuO2 in the temperature range from 300 to 1170 K of solid solutions corresponding to the compositions of (Ti1−x Rux )O2 (x ≤0.15 and x ≥0.85) and in the temperature range from 300 to 1550 K of pure TiO2. The analysis of experimental data obtained within ±2% of accuracy has shown that the characteristic temperatures representing the harmonic lattice vibrations do not strongly depend on the chemical composition x . It was demonstrated that non-harmonic heat capacity is strongly correlated to x. The existence of additional excess heat capacity was observed with the mixed oxide solid solution samples of low Ru content and explained by the defect formation model.
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    Temperature Modulated DSC. Theoretical interpretation (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 333-343 
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    ISSN: 1572-8943
    Keywords: base line ; DSC ; kinetics ; modeling ; thermodynamics ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The application of non-linear heating program to a heat-flux DSC apparatus has attracted much attention. From thermodynamics viewpoint, it is shown that the variation of enthalpy of a sample changing with temperature change is due, to both the true heat capacity of the sample and the enthalpy of some transformations occurring in the sample, characterized by its degree of advance. Using the simple assumption that the rate of the transformation is proportional to the distance from the thermodynamic equilibrium, an electrical model of the thermal event is given. Using the coupled cell model of the DSC apparatus, we show how to obtain the rate of transformation of the sample and heat capacity, which is directly related to the base line of the experiment.
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    The DSC Study of PA 6, Polyamides and Copolyamides (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 357-369 
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    ISSN: 1572-8943
    Keywords: blends of polyamides ; copolyamides ; crystallization ; DSC ; melting point ; structure
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The DSC method was used to obtain more information on changes of thermal properties connected with different comonomers bound in the (co)polymer chains. The copolyamides propered were block ones which were less crystalline and compatible with poly-ε-caprolactam. The results have confirmed the crystalline nature of polyamides and copolyamides.
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    A New Software to Show The Behaviour of The PID Controller. Part II. Influence of the setting parameters of DSCs (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 345-355 
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    ISSN: 1572-8943
    Keywords: DSC ; PID controllers ; tuning PID parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some DSC calorimeters, such as the model DSC 111, built by the society Setaram, allow the user to set the temperature programming parameters. Usually default values furnished by the constructor are often used, but it is very interesting to study the thermal behaviour of the regulation of the calorimeter under different conditions and with different kinds of set point temperatures. For this research, we have developed in C language a set of software in order to demonstrate the behaviour of the (proportional integral derivative) PID controller of the DSC. It can help the user to choose correct values for P, I and D parameters according to the kind of experiment conducted. The software allows studies of extra parameters, such as the sampling rate of the computerized PID controller or the determination of filtering of the correction.
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    Kinetic Studies of the Thermal Decomposition of KDNBF, a Primer for Explosives (2000)
    Springer
    Journal of thermal analysis and calorimetry 60 (2000), S. 917-926 
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    ISSN: 1572-8943
    Keywords: ARC ; DSC ; HFC ; KDNBF ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract KDNBF (potassium 4,6-dinitrobenzofuroxan) has been used as a primer explosive in igniters and detonators for many years. Considerable information about the sensitivity of KDNBF to various stimuli, such as impact, friction, shock and electrostatic charge, is known. However, the thermal sensitivity of KDNBF has been relatively unexplored. Hence, there is very little information available concerning the fundamental thermal properties of KDNBF. Therefore, as part of an extensive thermal hazard assessment, DSC, TG, accelerating rate calorimetry (ARC) and heat flux calorimetry (HFC) measurements have been undertaken on KDNBF. The results demonstrate that KDNBF decomposes via a multi-step exothermic process directly from the solid state. The decomposition process does not appear to depend on the nature of the atmosphere, except in the final stage of the TG decomposition in air, where remaining carbonaceous material is converted to CO2. The first stage of the decomposition is sufficiently rapid that ignition occurs if too large a sample is used. Dynamic and isothermal methods were used to obtain the kinetic parameters and a range of activation energies were obtained, depending on the experimental conditions. The kinetic results have been analyzed in terms of various solid state decomposition models.
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    Heat Capacity Measurements Using Temperature-modulated Heat Flux DSC with Close Control of the Heater Temperature (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 75-89 
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    ISSN: 1572-8943
    Keywords: DSC ; Fourier transformation ; heat capacity ; sawtooth-modulation ; TMDSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The determination of heat capacity data with sawtooth-type, temperature-modulated differential scanning calorimetry is analyzed using the Mettler-Toledo 820 ADSC™temperature-modulated differential scanning calorimeter (TMDSC). Heat capacities were calculated via the amplitudes of the first and higher harmonics of the Fourier series of the heat flow and heating rates. At modulation periods lower than about 150 s, the heat capacity deviates increasingly to smaller values and requires a calibration as function of frequency. An earlier derived correction function which was applied to the sample temperature-controlled power compensation calorimeter enables an empirical correction down to modulation periods of about 20 s. The correction function is determined by analysis of the higher harmonics of the Fourier transform from a single measurement of sufficient long modulation period. The correction function reveals that the time constant of the instrument is about 5 s rad−1 when a standard aluminum pan is used. The influence of pan type and sample mass on the time constant is determined, the correction for the asymmetry of the system is described, and the effect of smoothing of the modulated heat flow rate data is discussed.
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    Temperature and Heat Flow Calibration of A DSC-instrument in the Temperature Range Between −100 and 160°C (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 91-98 
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    ISSN: 1572-8943
    Keywords: DSC ; heat flow calibration ; temperature calibration
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Thermoanalytical instruments are extensively used in R&D as well as in industrial quality control. A quantitative analysis of the data of a thermoanalytical measurement requires a careful calibration of the instrument. In differential scanning calorimetry (DSC) the quantities that have to be calibrated are the temperature and the heat flow. These two quantities are usually calibrated by evaluating melting or solid-solid transitions of some reference materials with well known transition enthalpies and temperatures. In this contribution we investigate temperature and heat flow calibration in the temperature range between −100 and 160°C. We included 9 different samples for the analysis and established some general rules for the calibration process. As a result we found that with a well calibrated instrument the heat flow can be measured with 90% confidence to about ± 3% accuracy in this temperature range. With respect to temperature calibration we find that accuracies of ±0.8°C (90% confidence) may be expected. These values represent general accuracy limitations of DSC’s due to varying heat transfer conditions within the samples.
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    Thermodynamic Stability of Ribonuclease B (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 363-368 
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    ISSN: 1572-8943
    Keywords: DSC ; glycosylated ribonuclease ; thermodynamic stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermodynamic stability of pancreatic ribonuclease B (RNase B), which possesses identical protein structure of pancreatic ribonuclease A (RNase A), but differs by the presence of a carbohydrate chain attached to Asn 34, was studied by means of differential scanning calorimetry (DSC) at different pH conditions. The comparison between the two proteins has shown a little but significant stabilization of RNase B with respect to the unglycosylated one at pH values higher than 7.0. The thermodynamic analysis reveals the carbohydrate moiety to have a small stabilization effect of 3 kJ mol–1 at pH 8.0 and 63°C on the protein.
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    DSC and X-ray Diffraction Study of Polymorphism in n-Alkylammonium Chlorides (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 341-350 
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    ISSN: 1572-8943
    Keywords: DSC ; polymorphism ; X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The influence of the hydrocarbon chain length in the formation of interdigitated and non-interdigitated bilayers in n -alkylammonium chlorides has been investigated for chain lengths varying between 8 and 14 carbon atoms. The formation of non-interdigitated bilayers during crystallization from solution is favoured for shorter chains whilst the interdigitated structure is predominant for larger chains. The thermodynamic parameters of the solid to solid phase transitions in the non-interdigitated samples depend on chain length showing the odd-even alternation that characterized homologous series in n -paraffins. The solid to liquid crystal phase transition temperatures and enthalpies show a linear dependence with the chain length.
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    DSC in the Chemical Analysis of Drugs. Determination of diclofenac in pharmaceutical formulations (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 369-376 
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    ISSN: 1572-8943
    Keywords: diclofenac ; DSC
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential scanning calorimetry was applied to the determination of diclofenac in three 'Voltaren' formulas. The pharmaceutical products (soluble tablets, suppositories and vials) were selected in order to show that calorimetric analysis is an easy technique to perform and can be competitive with other conventional methods. In the tablets diclofenac (DH) was determined, without any pre-treatment, from the area of the endothermic peak which occurs at about 180°C in the DSC curve obtained in N2 atmosphere. In the analysis of the suppositories and vials, nitrilotriacetic acid (NTA) was added to transform the diclofenac sodium salt (DS) into the thermally active form (DH). In both cases, it was necessary to eliminate the interference of excipient by cyclohexane extraction (suppositories) or by a multistep program for the DSC run (vials). The accuracy of the results and the simplicity of the procedure justify the important role of DSC in the analysis of these drugs and certainly of several other commercial products.
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    Thermal Methods of Organic Matter Maturation Monitoring During a Composting Process (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 389-396 
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    ISSN: 1572-8943
    Keywords: compost ; DSC ; organic matter ; TG ; thermal stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The possibility to use thermal analysis for a quick characterisation of chemical changes in the organic matter of composted materials was tested. Nine samples were taken at progressive stages of maturation from the same trench of a fully automated composting plant. DSC and TG were simultaneously performed in static air conditions on whole ground composts. Progressive stages in the composting process yielded samples whose DSC traces revealed appreciable modifications in thermal patterns that agreed well with quantitative data obtained from TG measurements. The ratio between the mass losses associated with the two main exothermic reactions (R1) showed a good sensitivity in detecting the changes in the level of stabilisation during the composting process. Thermal methods seem to be a valid comparative method in evaluating the level of bio-transformation of materials during a composting process.
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    Starch Gelatinization Kinetics in Bread Dough. DSC investigations on 'simulated' baking processes (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 411-423 
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    ISSN: 1572-8943
    Keywords: bread baking ; DSC ; starch gelatinization
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Starch gelatinization in wheat flour dough of various moisture contents was quantitatively evaluated by means of DSC. The experimental records were worked out in the form of excess heat capacity vs. T traces which were deconvoluted to single out the contribution of starch gelatinization from that of the decomposition of amylose-lipid complexes. The quantitative procedure used put into evidence that a third endothermic process would take place in the dough with a poor moisture content. DSC runs carried out with sealed pans (i.e., at constant moisture level) and open pans (from which some water was free to evaporate) allow simulation of two extreme conditions of a real baking process, namely that relevant to the central core and to superficial layer of a dough loaf, respectively. The extent of starch gelatinization occurred in these conditions was quantitatively assessed. These data were collected at various heating rates and used to define temperature-time-transformation(TTT) diagrams which are useful tools to predict the progress of baking for any given thermal history of the system.
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    Structural and Mechanical Properties of Crosslinked Drawn Gelatin Films (2000)
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    Journal of thermal analysis and calorimetry 61 (2000), S. 451-459 
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    ISSN: 1572-8943
    Keywords: DSC ; gelatin films ; high angle X-ray
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Differential scanning calorimetry and high angle X-ray diffraction analyses were performed on gelatin films, air dried at different values of constant elongation, crosslinked with glutaraldehyde and examined at constant relative humidity of 75%. Drawing induces a preferential orientation of the chain segments of gelatin parallel to the stretching direction,and a linear increase of the renaturation level, calculated as the ratio between the denaturationenthalpy of gelatin films and that of tendon collagen. The comparison with the results previously obtained on the mechanical properties of the films, puts into evidence the different contributions of orientation and renaturation on the improvement of the mechanical parameters on drawing. The results offer important information on the role of glutaraldehyde (GTA) crosslinking on the stability of collagenous materials.
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    URL: http://dx.doi.org/10.1023/A:1010117401098
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    Surface Treatment of Dimenhydrinate Crystals (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 797-807 
    Details
    ISSN: 1572-8943
    Keywords: dimenhydrinate ; DSC ; film coating ; HPMC ; thermal conductivity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Dimenhydrinate is a heat-sensitive antihistamine with a low melting point. The heat-sensitive feature is of importance if direct compression is used. Direct measurement of the heat originating in the texture of tablets during compression is very difficult. Thermoanalytical methods were used as indirect methods to describe the changes in material properties at high temperature: differential scanning calorimetry, thermomicroscopy and thermogravimetric analysis. Film coating method is widely used in pharmaceutical technology. A fluidized bed apparatus was applied to coat the crystals. The coating film forming agent was hydroxy-propyl-methylcellulose (HPMC), which is a gastric-soluble polymer. Thermoanalytical measurements reveal that dimenhydrinate crystals are sensitive to heat. Film coating method does not alter the shape of the DSC curve of dimenhydrinate, but increases the melting point. The presence of a macromolecular film reduces the thermal conductivity, because it separates the particles.
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    URL: http://dx.doi.org/10.1023/A:1012093929296
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    Study of the Crystallization of an Aromatic Poly-ether-ketone (PK99) by Calorimetric and X-ray Analysis (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 565-578 
    Details
    ISSN: 1572-8943
    Keywords: crystallization ; DSC ; PK99 ; rigid amorphous fraction ; WAXD
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract An analysis of the crystallization behaviour of a new poly(aryl-ether-ether-ketone-ketone), PK99, by differential scanning calorimetry (DSC) and wide-angle X-ray diffraction (WAXD) is presented. Isothermal crystallization TG were obtained in the whole range between the glass transition temperature (T g) and the melting temperature (T m) as a consequence of the slow crystallization kinetics stemming from the closeness of these transitions. The calorimetric results, compared with WAXD data, were applied to determine the theoretical melting temperature and crystallization enthalpy. The DSC and WAXD data were combined in order to calculate the total amount of the crystallizable fraction of the polymer, and a model was proposed to explain the difference between the fractions of crystallinity observed with these techniques. The thermal and X-ray data were also correlated with different lamellar morphologies arising from the crystallization conditions. Finally, DSC experiments on the crystallized sample were used to detect the presence of a rigid amorphous phase which does not relax at T g.
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    URL: http://dx.doi.org/10.1023/A:1010185905642
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    DSC Study on the Interaction Between Bis-2-(Ethylhexyl) Phthalate and Other o-phthalic Acid Esters and Dipalmitoyl Phosphatidylcholine Liposomes (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 731-743 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; phase transition ; phospholipid ; phthalates ; plasticizers
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Phthalic acid esters, and in particular bis-2-(ethylhexyl) phthalate, are common environmental contaminants with long-term toxic and carcinogenic effects that readily dissolve in lipid substances. DSC measurements of hydrated multilamellar dipalmitoyl phosphatidylcholine liposomes in the presence of different amounts of bis-2-(ethylhexyl) phthalate, dioctyl phthalate, dibutyl phthalate (DBP) and diethyl phthalate (DEP) were considered. The effects on the main transition temperature, ΔH, and the shape and width of the transition were studied. A decrease in Tm, without an accompanying decrease in ΔH,and increases in both the asymmetry and the width of the main transition peak were observed. In some cases, the calorimetric curve showed complex peak structures arising from the coexistence of various aggregates of different sizes. This was particularly evident in the liposomes with DEP and DBP contents ranging from 5.0 to 7.5% m/m. For all the considered model systems, the effects were noticeable even in the presence of small amounts of phthalates; in the presence of greater amounts, the overall structure of the bilayer was in some cases strongly modified, with the appearance of new different phases. Since the function of a membrane-associated protein is dependent on the lipid structure, phthalates could modify the function by modifying the membrane structure.
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    Thermal Characterization of Passivated Nanometer Size Aluminium Powders (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 805-818 
    Details
    ISSN: 1572-8943
    Keywords: aluminium ; ARC ; DSC ; kinetics ; nanometric size ; SDT ; TG
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The thermal properties of Alex, a nanosized Al powder, were determined using various techniques, including DSC, TG, simultaneous TG-DTA (SDT) and accelerating rate calorimetry (ARC). The results demonstrate that the specific heat capacities of nano and micron size Al powders are similar between 30 and 400°C. Dynamic and isothermal methods were used to determine the kinetic parameters for the oxidation reaction of Alex, which was detected at an onset temperature of 481°C. The results obtained were in good agreement with each other. From the ARC experiments, exotherms were detected near 340 and 260°C for experiments started at ambient pressure and at 0.72 MPa, respectively.
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    URL: http://dx.doi.org/10.1023/A:1010197115003
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    Phase Diagram of EC–DMC Binary System and Enthalpic Determination of Its Eutectic Composition (2000)
    Springer
    Journal of thermal analysis and calorimetry 62 (2000), S. 177-186 
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    ISSN: 1572-8943
    Keywords: binary phase diagram ; DSC ; enthalpic method ; eutectic composition
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We construct with a differential scanning calorimeter (DSC) a phase diagram for the ethylene carbonate (EC)-dimethyl carbonate (DMC) binary system for its liquid-solid phase equilibria. We determine the eutectic composition of the binary system using an enthalpic method that we devised based on the composition dependence of the enthalpy of solidus melting, with highly consistent results. We also discuss the merits and limitations of this enthalpic method.
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    URL: http://dx.doi.org/10.1023/A:1010175114578
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    A New Software to Show the Behaviour of the PID Controller. Influence of the setting parameters of DSCs. Part I (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 999-1015 
    Details
    ISSN: 1572-8943
    Keywords: DSC ; PID controllers ; tuning PID parameters
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Some DSC calorimeters such as the model Setaram DSC 111 allow the user to set the parameters of temperature programming. Default values furnished by the constructor are often used, but it is very interesting to study the thermal behaviour of the regulation of the calorimeter under different conditions and kinds of set point temperatures. For this research we have developed in C a set of softwares in order to show the behaviour of the proportional integral derivative (PID) controller of the DSC. It can help the user to choose correct values for P, I and D parameters according to the kind of experiment conducted. The software allows studies for extra parameters such as the sampling rate of the computerized PID controller or the determination of filtering of the correction.
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    URL: http://dx.doi.org/10.1023/A:1010151114851
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    Thermal Measurements on Poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] Fibers (2000)
    Springer
    Journal of thermal analysis and calorimetry 59 (2000), S. 1023-1027 
    Details
    ISSN: 1572-8943
    Keywords: DMA ; DSC ; fibers ; polybenzimidazole ; secondary transitions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Fibers drawn form poly[2,2'-(m-phenylene)-5,5'-bibenzimidazole] (PBI) were studied by DSC and DMA. PBI is a high temperature polymer T g is between 387 and450°C depending on the measurement technique used. The as-spun fiber is free of orientation. The oriented fiber exhibits considerable dependence on whether the DSC measurements were carried out in free-to-shrink or fixed-length modes. The β-relaxation is at 290°C, and was associated with loss of water. The γ-transition at 20°C was not identified, while theδ-transition at –90°C seems to correspond to rotation of the m-phenylene ring.
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    URL: http://dx.doi.org/10.1023/A:1010155215759
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    Cure Kinetics of a Tetrafunctional Rubber Modified Epoxy-amine System (2000)
    Springer
    Journal of thermal analysis and calorimetry 61 (2000), S. 579-587 
    Details
    ISSN: 1572-8943
    Keywords: cure kinetics ; DSC ; modified epoxy-amine ; epoxy rubber system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract In this work the curing kinetics behaviour of a rubber modified epoxy amine system is investigated through calorimetric analysis. This study is part of a wider investigation on new epoxy formulations to be used as matrices of composite materials. The aim is to enhance both the processing behaviour and the mechanical properties of the matrix in order to obtain higher performance composites for more demanding applications. The epoxy system is blended with a high molecular mass rubber containing functional groups reactive towards the epoxies. The formation of a rubber/epoxy network can be achieved by means of a 'pre-reaction' between the epoxy monomers and the rubber functional groups, carried out in the presence of a suitable catalyst and before the resin is cured with the amino hardener. In this work the influence of both the rubber and the catalyst on the resin cure kinetics is analysed.
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    URL: http://dx.doi.org/10.1023/A:1010190022480
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    D-xylose Derivative Liquid Crystals (2000)
    Springer
    Journal of thermal analysis and calorimetry 63 (2000), S. 339-344 
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    ISSN: 1572-8943
    Keywords: amphiphile ; DSC ; D-xylose ; derivatives ; lyotropy ; thermotropy
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract We studied the phase transition temperatures of a series of amphiphilic D-xylopyranose and D-xylofuranose derivatives in which the lipophilic part is an alkyl chain R (n-CnH2n+1), regiospecifically linked to D-xylose, at different positions, by Z which is an atom or a functional group (O, S, O–(CH2)3–S). The alkyl chain was moved from the C-1 to the C-5 position in the xylose moiety, thereby allowing us to compare directly the phase transition temperatures of the individual materials. These compounds give thermotropic and/or lyotropic liquid crystals. In some cases, we also observed solid–solid phase transitions.
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    URL: http://dx.doi.org/10.1023/A:1010128106493
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    Some Considerations about the Structure of 3(5)-Methylpyrazole (2000)
    Springer
    Structural chemistry 11 (2000), S. 77-83 
    Details
    ISSN: 1572-9001
    Keywords: Dynamic NMR ; 15N NMR ; 13C NMR ; DSC ; tautomerism ; melting point
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The behavior of neat 3(5)-methylpyrazole has been studied at low temperatures by DSC and by NMR (13C and 15N). The main conclusion is that the supercooled liquid is a mixture of four trimers formed by 3-methyl and 5-methyl tautomers.
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    URL: http://dx.doi.org/10.1023/A:1009276524564
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    On the Stability of Functional Equations and a Problem of Ulam (2000)
    Springer
    Acta applicandae mathematicae 62 (2000), S. 23-130 
    Details
    ISSN: 1572-9036
    Keywords: stability ; functional equations ; Cauchy difference ; semigroup ; inequalities ; approximate
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mathematics
    Notes: Abstract In this paper, we study the stability of functional equations that has its origins with S. M. Ulam, who posed the fundamental problem 60 years ago and with D. H. Hyers, who gave the first significant partial solution in 1941. In particular, during the last two decades, the notion of stability of functional equations has evolved into an area of continuing research from both pure and applied viewpoints. Both classical results and current research are presented in a unified and self-contained fashion. In addition, related problems are investigated. Some of the applications deal with nonlinear equations in Banach spaces and complementarity theory.
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    URL: http://dx.doi.org/10.1023/A:1006499223572
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    Debonding of the interface as 'crack arrestor' (2000)
    Springer
    International journal of fracture 105 (2000), S. 57-79 
    Details
    ISSN: 1573-2673
    Keywords: Interface toughness ; interface debonding ; stability ; adhesive interface ; bimaterial.
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract In this paper, we studied the interface debonding when a crack perpendicularly approaches an interface between two dissimilar elastic materials. An interface toughness law was first defined according to an adhesive model governing the interface fracture. By analysing the interaction between the normally approaching crack and the interface crack and by tacking account of the adhesive forces at ends of the interfacial crack, a model for studying the interface debonding and the debonding stability was established. It is observed that the interface debonding toughness depends strongly on the mixed mode locally produced over the plastic adhesive zone of the interface. Moreover, the interface debonding may be unstable, i.e. the interface debonding length may jump from an initial value to a certain final value under critical remote loading. This jump may be surprisedly important in certain cases. These results agree with the experimental works gathered so far and can be used to explain the mechanism of 'crack arrestor' formed by an interface.
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    URL: http://dx.doi.org/10.1023/A:1007603809972
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    Molecular Modeling of the Complexes between Saccharomyces cerevisiae Phosphoenolpyruvate Carboxykinase and the ATP Analogs Pyridoxal 5′-Diphosphoadenosine and Pyridoxal 5′-Triphosphoadenosine. Specific Labeling of Lysine 290 (2000)
    Springer
    The protein journal 19 (2000), S. 67-73 
    Details
    ISSN: 1573-4943
    Keywords: Homology modeling ; rotational energy barrier ; simulated annealing ; pyridoxal 5′-diphosphoadenosine ; pyridoxal 5′-triphosphoadenosine ; Saccharomyces cerevisiae ; phosphoenolpyruvate carboxykinase
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Molecular mechanics calculations have been employed to obtain models of the complexes between Saccharomyces cerevisiae phosphoenolpyruvate (PEP) kinase and the ATP analogs pyridoxal 5′-diphosphoadenosine (PLP-AMP) and pyridoxal 5′-triphosphoadenosine (PLP-ADP), using the crystalline coordinates of the ATP-pyruvate-Mn2+-Mg2+ complex of Escherichia coli PEP carboxykinase [Tari et al. (1997), Nature Struct. Biol. 4, 990–994]. In these models, the preferred conformation of the pyridoxyl moiety of PLP-ADP and PLP-AMP was established through rotational barrier and simulated annealing procedures. Distances from the carbonyl-C of each analog to ε-N of active-site lysyl residues were calculated for the most stable enzyme-analog complex conformation, and it was found that the closest ε-N is that from Lys290, thus predicting Schiff base formation between the corresponding carbonyl and amino groups. This prediction was experimentally verified through chemical modification of S. cerevisiae PEP carboxykinase with PLP-ADP and PLP-AMP. The results here described demonstrate the use of molecular modeling procedures when planning chemical modification of enzyme-active sites.
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    Effects of Ca2+ on the Activity and Stability of Methanol Dehydrogenase (2000)
    Springer
    The protein journal 19 (2000), S. 469-473 
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    ISSN: 1573-4943
    Keywords: Methanol dehydrogenase ; Ca2+ ; binding ; activity ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract The effects of exogenously added Ca2+ on the enzymatic activity and structural stability of methanol dehydrogenase were studied for various Ca2+ concentrations. Methanol dehydrogenase activity increased significantly with increasing concentration of Ca2+, approaching saturation at 200 mM Ca2+. The effect of Ca2+ on the activation of MDH was time dependent and Ca2+ specific and was due to binding of the metal ions to the enzyme. Addition of increasing concentration of Ca2+ caused a decrease of the intrinsic tryptophan fluorescence intensity in a concentration-dependent manner to a minimum at 200 mM, but with no change in the fluorescence emission maximum wavelength or the CD spectra. The results revealed that the activation of methanol dehydrogenase by Ca2+ occurred concurrently with the conformational change. In addition, exogenously bound Ca2+ destabilized MDH. The potential biological significance of these results is discussed.
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    Differential scanning calorimetry of chromatin at different levels of condensation (2000)
    Springer
    Molecular biology reports 27 (2000), S. 175-180 
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    ISSN: 1573-4978
    Keywords: chromatin ; DNA ; DSC ; thermal denaturation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The thermal denaturation of calf thymus total chromatin and of fractions enriched in heterochromatin or euchromatin, has been investigated by differential scanning calorimetry and compared to that of calf thymus DNA and DNA-histone complexes. In our experimental conditions, chromatin melts in three thermal transitions: the main one, assigned to separation of the DNA double helix, occurs at 83 °C, while the other two occur at 63 °C and 74 °C. The data show that: (a) the transition enthalpy for denaturation of DNA in the total chromatin and in DNA-histone complexes is nearly the same as that of DNA in solution; (b) the transition at 63 °C is present in the thermogram of the heterocromatin enriched fraction, while it is completely absent in that of the euchromatin enriched one. The results suggest that this transition can be attributed to the higher order structures of heterochromatin.
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    Involvement of the Inverted Repeat of the yeast 2-micron plasmid in Flp site-specific and RAD52-dependent homologous recombination (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 81-89 
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    ISSN: 1617-4623
    Keywords: Key words Flp recombinase ; Site-specific recombination ; Homologous recombination ; RAD52 ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Site-specific recombination within the Saccharomyces cerevisiae 2-micron DNA plasmid is catalyzed by the Flp recombinase at specific Flp Recognition Target (FRT) sites, which lie near the center of two precise 599-bp Inverted Repeats (IRs). However, the role of IR DNA sequences other than the FRT itself for the function of the Flp reaction in vivo is not known. In the present work we report that recombination efficiency differs depending on whether the FRT or the entire IR serves as the substrate for Flp. We also provide evidence for the involvement of the IR in RAD52-dependent homologous recombination. In contrast, the catalysis of site-specific recombination between two FRTs does not require the function of RAD52. The efficiency of Flp site-specific recombination between two IRs cloned in the same orientation is about one hundred times higher than that obtained when only the two FRTs are present. Moreover, we demonstrate that a single IR can activate RAD52-dependent homologous recombination between two flanking DNA regions, providing new insights into the role of the IR as a substrate for recombination and a new experimental tool with which to study the molecular mechanism of homologous recombination.
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    Ambient pH signalling in ascomycetous yeasts involves homologues of theAspergillus nidulans genes palF and palH (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 505-513 
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    ISSN: 1617-4623
    Keywords: Key wordsYarrowia lipolytica ; Saccharomyces cerevisiae ; Ambient pH signalling ; Signal transduction ; Transmembrane protein
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In Yarrowia lipolytica, the transcription factor Rim101p mediates both pH regulation and control of mating and sporulation. Like its homologues PacC of Aspergillus nidulans and Rim101p of Saccharomyces cerevisiae, YlRim101p is activated by proteolytic C-terminal processing, which occurs in response to a signal transduced by a pathway involving several PAL gene products. We report here the cloning and sequencing of two of these genes, PAL2 and PAL3. PAL2 encodes a putative 632-residue protein with six possible transmembrane segments, which differs from the transmembrane proteins Rim9p of S. cerevisiae and PalI of A. nidulans, but is homologous to A. nidulans PalH and to the product of the ORF YNL294c, a predicted polypeptide of unknown function in S. cerevisiae. PAL3 encodes an 881-residue polypeptide that is homologous to PalF of A. nidulans and to a newly identified putative polypeptide of S. cerevisiae. Both PAL2 and PAL3 are expressed constitutively, regardless of ambient pH. Mutations in these genes affect growth at alkaline pH and sporulation in both Y. lipolytica and in S. cerevisiae. They affect invasiveness of haploid strains in S. cerevisiae only, and conjugation in Y. lipolytica only. These results highlight the conservation of the Pal pathway initially described in A. nidulans.
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    Multiple copies of MRG19 suppress transcription of the GAL1 promoter in a GAL80 -dependent manner in Saccharomyces cerevisiae (2000)
    Springer
    Molecular genetics and genomics 262 (2000), S. 1113-1122 
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    ISSN: 1617-4623
    Keywords: Key wordsGAL regulon ; Transcription ; Saccharomyces cerevisiae ; Galactose suppression
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract A plasmid clone that suppresses galactose toxicity in a gal7 yeast strain has been isolated from a multicopy genomic DNA library. Molecular analysis revealed that the region responsible for the suppression of galactose toxicity corresponds to the ORF YPR030w, which was named MRG19. A CEN-based plasmid carrying the above ORF was unable to suppress the toxicity. Galactokinase activity was substantially reduced in cell extracts obtained from transformants bearing multiple copies of MRG19. Multiple copies of MRG19 were also able to suppress galactokinase expression driven by the CYC1 promoter but not the TEF1 promoter. Multiple copies of MRG19 could not suppress GAL1-driven galactokinase expression in a gal80 strain. However, MRG19-mediated suppression of CYC1-driven galactokinase expression was independent of GAL80 function. These results imply that multiple copies of MRG19 suppress galactokinase expression probably at the level of transcription. In agreement with this idea, multiple copies of MRG19 also suppress β-galactosidase expression driven by the GAL1 promoter in a GAL80-dependent manner. Disruption of MRG19 leads to an increase in the cell density at stationary phase in synthetic complete medium. MRG19 encodes a previously uncharacterised 124-kDa protein that shows no sequence homology to any known proteins.
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    Bifurcations of a cantilevered pipe conveying steady fluid with a terminal nozzle (2000)
    Springer
    Acta mechanica Sinica 16 (2000), S. 264-272 
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    ISSN: 1614-3116
    Keywords: nonlinear dynamics ; bifurcation ; stability ; fluid-solid interaction
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract This paper studies interactions of pipe and fluid and deals with bifurcations of a cantilevered pipe conveying a steady fluid, clamped at one end and having a nozzle subjected to nonlinear constraints at the free end. Either the nozzle parameter or the flow velocity is taken as a variable parameter. The discrete equations of the system are obtained by the Ritz-Galerkin method. The static stability is studied by the Routh criteria. The method of averaging is employed to examine the analytical results and the chaotic motions. Three critical values are given. The first one makes the system lose the static stability by pitchfork bifurcation. The second one makes the system lose the dynamical stability by Hopf bifurcation. The third one makes the periodic motions of the system lose the stability by doubling-period bifurcation.
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    Long-term monitoring of benthic macroinvertebrate community structure: a perspective from a Colorado river* (2000)
    Springer
    Aquatic ecology 34 (2000), S. 261-278 
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    ISSN: 1573-5125
    Keywords: discharge effects on lotic invertebrates ; disturbance ; persistence ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Temporal and spatial trends were examined in benthic macroinvertebrate and physical-chemical data collected for at least ten years at ten sites along the plains reach of the Cache la Poudre River, Colorado, USA. A distinct longitudinal environment gradient was found as many of the water chemistry parameter levels changed downstream from the reference site. Seasonal Kendall analyses on individual sites indicated that several chemical parameters, including conductivity, un-ionized NH3-N and NO2-N have increased since the beginning of the study within most sites. Levels of some parameters (e.g., dissolved oxygen, un-ionized NH3-N) violated aquatic life standards a few times during the study. Over 175 taxa of macroinvertebrates (primarily insects) were collected in the study reach from 1981–1996. Results from detrended correspondence analyses (DCA) on macroinvertebrate data indicated that this stretch of the river exhibited little longitudinal change beyond the two farthest upstream sites. There was a decline in macroinvertebrate density and total number of taxa within most individual sites during 1983–1984, corresponding with the highest recorded discharge in 75 years (1983) and a prolonged, heavy spring runoff in 1984. Taxa richness and density recovered to pre-1983 levels within a few months to a year following the high flows at most sites. These findings suggested that the macroinvertebrate assemblages had low resistance to disturbance, but high resilience. However, the results from DCAs and Kendall's Coefficient of Concordance (W) on individual sites for the entire study period suggested a similar macroinvertebrate community structure through time. It would appear that the composition and abundance of the lotic macroinvertebrate assemblages in the Poudre River has remained relatively constant over the long-term. This has occurred even with some potentially negative changes in water chemistry and increased urban development.
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    URL: http://dx.doi.org/10.1023/A:1009989510721
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    Numerical solutions for a coupled non-linear oscillator (2000)
    Springer
    Journal of mathematical chemistry 28 (2000), S. 325-340 
    Details
    ISSN: 1572-8897
    Keywords: numerical method ; stability ; Hopf bifurcation ; coupled oscillator
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Mathematics
    Notes: Abstract A second-order accurate numerical method has been proposed for the solution of a coupled non-linear oscillator featuring in chemical kinetics. Although implicit by construction, the method enables the solution of the model initial-value problem (IVP) to be computed explicitly. The second-order method is constructed by taking a linear combination of first-order methods. The stability analysis of the system suggests the existence of a Hopf bifurcation, which is confirmed by the numerical method. Both the critical point of the continuous system and the fixed point of the numerical method will be seen to have the same stability properties. The second-order method is more competitive in terms of numerical stability than some well-known standard methods (such as the Runge–Kutta methods of order two and four).
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011025104111
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    1,3-Dihydrobenzo[c]thienylium (thiophthalylium) salts. (Review) (2000)
    Springer
    Chemistry of heterocyclic compounds 36 (2000), S. 115-133 
    Details
    ISSN: 1573-8353
    Keywords: thiophthalylium salts ; methods of preparation ; structure ; stability ; reactivity ; electrophilic properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology
    Notes: Abstract Methods of preparation, chemical reactions, the structures and reactivity of thiophthalylium ions are reviewed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02283539
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    Solving A $$\underline x $$ = $$\underline b $$ Using a Modified Conjugate Gradient Method Based on Roots of A (2000)
    Springer
    Journal of scientific computing 15 (2000), S. 441-456 
    Details
    ISSN: 1573-7691
    Keywords: modified conjugate gradient method ; conjugate gradient method ; Krylov space ; convergence rate ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract We consider the modified conjugate gradient procedure for solving A $$\underline x $$ = $$\underline b $$ in which the approximation space is based upon the Krylov space associated with A 1/p and $$\underline b $$ , for any integer p. For the square-root MCG (p=2) we establish a sharpened bound for the error at each iteration via Chebyshev polynomials in $$\sqrt A$$ . We discuss the implications of the quickly accumulating effect of an error in $$\sqrt A$$ $$\underline b $$ in the initial stage, and find an error bound even in the presence of such accumulating errors. Although this accumulation of errors may limit the usefulness of this method when $$\sqrt A$$ $$\underline b $$ is unknown, it may still be successfully applied to a variety of small, “almost-SPD” problems, and can be used to jump-start the conjugate gradient method. Finally, we verify these theoretical results with numerical tests.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1011132730828
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    Associative Memories in Infinite Dimensional Spaces (2000)
    Springer
    Neural processing letters 12 (2000), S. 129-144 
    Details
    ISSN: 1573-773X
    Keywords: associative memory ; dynamical systems ; Glauber dynamics ; Hopfield model ; infinite dimensional state space ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Computer Science
    Notes: Abstract A generalization of the Little–Hopfield neural network model for associative memories is presented that considers the case of a continuum of processing units. The state space corresponds to an infinite dimensional euclidean space. A dynamics is proposed that minimizes an energy functional that is a natural extension of the discrete case. The case in which the synaptic weight operator is defined through the autocorrelation rule (Hebb rule) with orthogonal memories is analyzed. We also consider the case of memories that are not orthogonal. Finally, we discuss the generalization of the non deterministic, finite temperature dynamics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1009689025427
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    Partial Compensation for Mismatched Uncertain Discrete Systems (2000)
    Springer
    Dynamics and control 10 (2000), S. 47-61 
    Details
    ISSN: 1573-8450
    Keywords: stability ; robust control ; Lyapunov approach ; discrete system
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Control design of nonlinear discrete-time uncertain systems with (possibly fast) uncertain parameters is considered. We study the effect of only partially compensating the uncertainty. The optimal choice of a design parameter, which indicates the amount of compensation, is recommended.
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    URL: http://dx.doi.org/10.1023/A:1008395928788
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    Optimal Model Reduction with a Frequency Weighted Extension (2000)
    Springer
    Dynamics and control 10 (2000), S. 255-276 
    Details
    ISSN: 1573-8450
    Keywords: continuous-time systems ; frequency weighted model reduction ; gradient flow ; optimization ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Inthis paper, a model reduction technique based on optimizationis presented. The objective function minimized is the impulseenergy of the overall system. An extension of the technique tothe frequency weighted case is also presented, where single-sidedor double-sided weightings can be incorporated in the reductionprocedure. The paper proposes an alternative to find an optimizationsolution by solving ordinary differential equations which aregradient flow associated with the objective function to be minimized.Two examples are presented to illustrate the effectiveness ofthe method.
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    URL: http://dx.doi.org/10.1023/A:1008366812002
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    The Equation of State of Lakes (2000)
    Springer
    Aquatic geochemistry 6 (2000), S. 1-17 
    Details
    ISSN: 1573-1421
    Keywords: lakes ; density ; compressibility ; expansibility ; conductivity ; stability ; pvt properties
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Geosciences
    Notes: Abstract In recent years, a number of workers have studied the stability of deep lakes such as Lake Tanganyika, Lake Baikal and Lake Malawi. In this paper, the methods that can be used to determine the effect that the components of lakes have on the equation of state are examined. The PVT properties of Lakes have been determined by using apparent molal volume data for the major ionic components of the lake. The estimated PVT properties (densities, expansibility and compressibilities) of the lakes are found to be in good agreement with the PVT properties (P) of seawater diluted to the same salinity. This is similar to earlier work that showed that the PVT properties of rivers and estuarine waters could also be estimated from the properties of seawater. The measured densities of Lake Tanganyika were found to be in good agreement (± 2 × 10-6 g cm-3) with the values estimated from partial molal properties and the values of seawater at the same total salinity (ST = 0.568‰). The increase in the densities of Lake Tanganyika waters increased due to changes in the composition of the waters. The measured increase in the measured density (45 × 10-6 g cm-3) is in good agreement (46 × 10-6 g cm-3) with the values calculated for the increase in Na+, HCO3 -, Mg2+, Ca2+ and Si(OH)4. Methods are described that can be used to determine the conductivity salinity of lakes using the equations developed for seawater. By combining these relationships with apparent molal volume data, one can relate the PVT properties of the lake to those of seawater.
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    URL: http://dx.doi.org/10.1023/A:1009626325650
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    Surface Instability of Laminated Coatings upon Inelastic Deformation (2000)
    Springer
    Mechanics of composite materials 36 (2000), S. 475-480 
    Details
    ISSN: 1573-8922
    Keywords: stability ; three-dimensional theory ; tribotechnics ; elastoplastic deformations ; viscoelasticity ; surface ; tracking and dead loads ; laminated coating ; piecewise-homogeneous model ; active loading
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics
    Notes: Abstract The problem of surface instability of laminated coatings with inelastic properties is considered within the framework of a model of piecewise-homogeneous media on the basis of the three-dimensional linearized theory of stability. A general statement of the problem is formulated and the basic characteristic equations are derived. The solutions of particular problems are obtained for elastoplastic and viscoelastic models of solids.
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    URL: http://dx.doi.org/10.1023/A:1006758600457
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    On the Stability of Nonconservative Systems with Estimation of the Attraction Domain (2000)
    Springer
    Journal of dynamical and control systems 6 (2000), S. 503-510 
    Details
    ISSN: 1573-8698
    Keywords: nonconservative mechanical systems ; stability ; Lyapunov functions ; attraction domain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Electrical Engineering, Measurement and Control Technology
    Notes: Abstract Mechanical systems subjected to dissipative, gyroscopic, conservative, and also nonconservative positional forces are considered. The question of the effect of dissipative, gyroscopic, and conservative forces on the motion stability of a mechanical systems is determined by classical Kelvin–Chetaev theorems [1]. The presence of nonconservative positional forces considerably complicates the situation and excludes direct application of these theorems. Applying Lyapunov's functions method the condition of asymptotic stability of a mechanical system under the action of all listed above forces is obtained. Moreover, the estimation of the attraction domain in phase space is found. The precession system which is used in the solution of some problems in the applied theory of the gyroscopic systems is also examined. The connection between the stability of origin and precession systems is detected. Theoretical results are applied to the stabilization problem of stationary motion of the balanced gimbal suspension gyro by means of external moments.
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    URL: http://dx.doi.org/10.1023/A:1009500527061
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    Structure-function relationships in replication origins of the yeast Saccharomyces cerevisiae: higher-order structural organization of DNA in regions flanking the ARS consensus sequence (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 854-866 
    Details
    ISSN: 1617-4623
    Keywords: Key words Autonomously replicating sequence (ARS) ; Anti-bent DNA ; DNA structure ; Replication origin ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract In order to better understand the involvement of the DNA molecule in the replication initiation process we have characterized the structure of the DNA at Autonomously Replicating Sequences (ARSs) in Saccharomyces cerevisiae. Using a new method for anti-bent DNA analysis, which allowed us to take into account the bending contribution of each successive base plate, we have investigated the higher-order structural organization of the DNA in the region which immediately surrounds the ARS consensus sequence (ACS). We have identified left- and right-handed anti-bent DNAs which flank this consensus sequence. The data show that this organization correlates with an active ACS. Analysis of the minimum nucleotide sequence providing ARS function to plasmids reveals an example where the critical nucleotides are restricted to the ACS and the right-handed anti-bent DNA domain, although most of the origins considered contained both left- and right-handed anti-bent DNAs. Moreover, mutational analysis shows that the right-handed form is necessary in order to sustain a specific DNA conformation which is correlated with the level of plasmid maintenance. A model for the role of these individual structural components of the yeast replication origin is presented. We discuss the possible role of the right-handed anti-bent DNA domain, in conjunction with the ACS, in the process of replication initiation, and potentialities offered by the combination of left- and right-handed structural components in origin function.
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    URL: http://dx.doi.org/10.1007/s004380000253
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    Characterization of staurosporine-sensitive mutants of Saccharomyces cerevisiae: vacuolar functions affect staurosporine sensitivity (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 877-888 
    Details
    ISSN: 1617-4623
    Keywords: Key words Staurosporine ; Vacuolar-type proton pumping ATPase ; Vacuolar protein sorting ; ATP-binding cassette transporter ; Saccharomyces cerevisiae
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract Mutations at several loci affect the sensitivity of the yeast Saccharomyces cerevisiae to staurosporine. We report here the characterization of novel staurosporine- and temperature-sensitive mutants (stt). Cloning and integration mapping showed that the genes STT2/STT6, STT5, STT7, STT8 and STT9 are allelic to VPS18, ERG10, GPI1, VPS34 and VPS11, respectively. The products of ERG10 and GPI1, respectively, catalyze mevalonate and glycosyl phosphatidylinositol anchor synthesis, while VPS18 and VPS11 genes belong to the class C VPS (Vacuolar Protein Sorting) genes, and the VPS34 gene is classified as a class D VPS. Therefore, staurosporine sensitivity is affected by ergosterol and glycolipid biosynthesis and by vacuolar functions. We found that other vps mutants belonging to classes C and D exhibit staurosporine sensitivity, and that they show calcium sensitivity and fail to grow on glycerol as the sole carbon source; both of the last two characteristics are shared by vacuolar H+-ATPase mutants (vma). As vma mutants were also found to show staurosporine-sensitive growth, staurosporine sensitivity is likely to be affected by acidification of the vacuole. Moreover, wild type yeast cells are more sensitive to staurosporine in alkaline media than in acidic media, suggesting that staurosporine is exported from the cytosol by H+/drug antiporters. Pleiotropic drug resistance (PDR) genes also provide some resistance to staurosporine, because Δpdr5, Δsnq2 and Δyor1 strains are more sensitive to staurosporine than the wild-type strain. This suggests that staurosporine is also exported by the ATP-binding cassette (ABC) transporters on the plasma membrane. vma mutants and vps mutants of classes C and D vps are sensitive to hygromycin B and vanadate, while ABC transporter-depleted mutants do not show such sensitivity, indicating that two systems differ in their ability to protect the cell against different types of drug.
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    URL: http://dx.doi.org/10.1007/s004380000255
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    MUS81 encodes a novel Helix-hairpin-Helix protein involved in the response to UV- and methylation-induced DNA damage in Saccharomyces cerevisiae (2000)
    Springer
    Molecular genetics and genomics 263 (2000), S. 812-827 
    Details
    ISSN: 1617-4623
    Keywords: Key words DNA repair ; Helix-hairpin-Helix motif ; Methylmethane sulfonate (MMS) ; Saccharomyces cerevisiae ; UV radiation
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The gene MUS81 (Methyl methansulfonate, UV sensitive) was identified as clone 81 in a two-hybrid screen using the Saccharomyces cerevisiae Rad54 protein as a bait. It encodes a novel protein with a predicted molecular mass of 72,316 (632 amino acids) and contains two helix-hairpin-helix motifs, which are found in many proteins involved in DNA metabolism in bacteria, yeast, and mammals. Mus81p also shares homology with motifs found in the XPF endonuclease superfamily. Deletion of MUS81 caused a recessive methyl methansulfonate- and UV-sensitive phenotype. However, mus81Δ cells were not significantly more sensitive than wild-type to γ-radiation or double-strand breaks induced by HO endonuclease. Double mutant analysis suggests that Rad54p and Mus81p act in one pathway for the repair of, or tolerance to, UV-induced DNA damage. A complex containing Mus81p and Rad54p was identified in immunoprecipitation experiments. Deletion of MUS81 virtually eliminated sporulation in one strain background and reduced sporulation and spore viability in another. Potential homologs of Mus81p have been identified in Schizosaccharomyces pombe, Caenorhabditis elegans and Arabidopsis thaliana. We hypothesize that Mus81p plays a role in the recognition and/or processing of certain types of DNA damage (caused by UV and MMS) during repair or tolerance processes involving the recombinational repair pathway.
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    URL: http://dx.doi.org/10.1007/s004380000241
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    Recurrent selection in oat for adaptation to diverse environments (2000)
    Springer
    Euphytica 113 (2000), S. 195-205 
    Details
    ISSN: 1573-5060
    Keywords: Avena ; genetic correlation ; genotype-environmentinteraction ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Agriculture, Forestry, Horticulture, Fishery, Domestic Science, Nutrition
    Notes: Abstract In order to test if selection can improve a population's adaptation to diverse environments simultaneously, three cycles of recurrent selection based on grain yield in Iowa, Idaho, and Norway were practiced in an oat (Avena sativaL.) population developed from North American, Scandinavian, and wild species (A. sterilis L.) germplasm sources. Specific objectives were to determine if selection: increased mean yields across environments and within all environments; changed the genetic correlation of yields in different environments; and changed genetic variation for yield within the population. We evaluated 100 to 210 randomly-chosen families from each cycle of selection at three Iowa locations, in Idaho, and in Norway for two years. Grain yield within each location and mean yields across locations increased significantly over cycles of selection. Mean yields across locations expressed as a percent of the original population mean increased at a rate of 2.6% per year. Several families from the third cycle population exhibited both high mean yields across locations and consistently high yields within all locations. Average genetic correlations of yield in different environments were higher in the second cycle than in the original population. A trend of reduced genetic variation and heritability was observed in Iowa only. These results suggest that we successfully improved mean population yield both within and across locations, and yield stability across environments, and in developing families with outstanding adaptation to diverse environments.
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    URL: http://dx.doi.org/10.1023/A:1003933421378
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    Determination of primary structure of amberjack myosin heavy chain and its relationship with structural stability of various fish myosin rods (2000)
    Springer
    Fish physiology and biochemistry 23 (2000), S. 283-294 
    Details
    ISSN: 1573-5168
    Keywords: amberjack ; myosin heavy chain ; cDNA ; α-helix ; coiled coils ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology
    Notes: Abstract The structural stability of fish myosin depends upon species and temperatures of water in which fish live. Primary, secondary, and quaternary structures of myosin heavy chain (MyHC) from three species of fish living at different temperature ranges have been compared with those of rabbit MyHC in order to investigate the differences in stability. Primary structure of MyHC, although being accessible for warm-water and cold-water fish (carp and walleye pollack), was not available in previous for tropical-water fish literature; so in this study primary structure of MyHC of the tropical-water fish amberjack has been determined by cloning and sequencing its cDNA. The MyHC has 1938 amino acid residues (AA), which are almost as much as as those of carp and walleye pollack. The amberjack MyHC is 91–95% homologous with other fish and rabbit MyHCs. There is a discernible difference between animal species with stable myosin rod (amberjack, carp, and rabbit) and walleye pollack with unstable rod. Stable rod species have a high probability of forming coiled-coil around the COOH-terminal end of the rod, while the pollack has a low coiled-coil formation probability. In addition, the average scores of the coiled-coil for myosin rod were rabbit (1.738) 〉 amberjack (1.691) 〉 carp (1.680) 〉 walleye pollack (1.674) which correlated exactly with the observed stability. The results suggest that coiled-coil forming ability, particularly around the COOH-terminal end, directs structural stability of fish myosin rod.
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    URL: http://dx.doi.org/10.1023/A:1011176105285
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