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  • Articles  (20)
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  • Turbulence
  • stability
  • Springer  (20)
  • American Geophysical Union
  • American Institute of Physics (AIP)
  • American Physical Society
  • Blackwell Publishing Ltd
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  • 2000-2004
  • 1995-1999  (20)
  • 1945-1949
  • 1997  (20)
  • Physics  (18)
  • Medicine  (2)
  • 1
    Electronic Resource
    Electronic Resource
    Stability and Geometry of Third-Order Resonances in four-Dimensional Symplectic Mappings (1997)
    Springer
    Celestial mechanics and dynamical astronomy 67 (1997), S. 181-204 
    Details
    ISSN: 1572-9478
    Keywords: Hamiltonian systems ; symplectic mappings ; normal forms ; resonances ; stability ; three degrees of freedom
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We analyze four-dimensional symplectic mappings in the neighbourhood of an elliptic fixed point whose eigenvalues are close to satisfy a third-order resonance. Using the perturbative tools of resonant normal forms, the geometry of the orbits and the existence of elliptic or hyperbolic one-dimensional tori (fixed lines) is worked out. This allows one to give an analytical estimate of the stability domain when the resonance is unstable. A comparison with numerical results for the four-dimensional Hénon mapping is given.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008288826727
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  • 2
    Electronic Resource
    Electronic Resource
    Existence and Stability of L4,5 In The Relativistic Restricted Three-Body Problem (1997)
    Springer
    Celestial mechanics and dynamical astronomy 69 (1997), S. 271-281 
    Details
    ISSN: 1572-9478
    Keywords: restricted three-body problem ; libration points ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The existence and stability of triangular libration points in the relativistic restricted three-body problem has been studied. It is found that L4,5 are unstable in the whole range 0 ≤ µ ≤ 1/2 in contrast to the classical restricted three-body problem where they are stable for 0 〈 µ 〈 µ0, where µ is the mass parameter and µ0 = 0.03852....
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008271021060
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  • 3
    Electronic Resource
    Electronic Resource
    Long Time Stability for the Main Problem of Artificial Satellites (1997)
    Springer
    Celestial mechanics and dynamical astronomy 69 (1997), S. 317-330 
    Details
    ISSN: 1572-9478
    Keywords: artificial satellite ; Nekhoroshev's theory ; normal form ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We investigate the significance of long time stabilty predictions in the light of Nekhoroshev's theory by studying the orbits of artificial satellites. As a simplified model problem we consider the so-called J2problem for an earth's satellite, neglecting luni-solar perturbations and nonconservative effects. We consider a wide range of orbits, excluding those which are too close to the critical inclination. Most of the orbits turn out to be stable for times larger than the estimated age of the solar system, thus proving that, as far as dissipation can be neglected, stability in Nekhoroshev's sense may be effective for physically realistic systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1008277122375
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  • 4
    Electronic Resource
    Electronic Resource
    Stable Quasicrystalline Ground States (1997)
    Springer
    Journal of statistical physics 88 (1997), S. 691-711 
    Details
    ISSN: 1572-9613
    Keywords: Quasicrystals ; nonperiodic tilings ; classical lattice-gas models ; ground states ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We give strong evidence that noncrystalline materials such as quasicrystals or incommensurate solids are not exceptions, but rather are generic in some regions of phase space. We show this by constructing classical lattice-gas models with translation-invariant finite-range interactions and with a unique quasiperiodic ground state which is stable against small perturbations of two-body potentials. More generally, we provide a criterion for stability of nonperiodic ground states.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/B:JOSS.0000015168.25151.22
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  • 5
    Electronic Resource
    Electronic Resource
    Rapid isolation of muscle and heart mitochondria, the lability of oxidative phosphorylation and attempts to stabilize the process in vitro by taurine, carnitine and other compounds (1997)
    Springer
    Molecular and cellular biochemistry 174 (1997), S. 61-66 
    Details
    ISSN: 1573-4919
    Keywords: heart mitochondria ; lability ; muscle mitochondria ; oxidative phosphorylation ; stability ; taurine
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Chemistry and Pharmacology , Medicine
    Notes: Abstract We modified the isolation procedure of muscle and heart mitochondria. In human muscle, this resulted in a 3.4 fold higher yield of better coupled mitochondria in half the isolation time. In a preparation from rat muscle we studied factors that affected the stability of oxidative phosphorylation (oxphos) and found that it decreased by shaking the preparation on a Vortex machine, by exposure to light and by an increase in storage temperature. The decay was found to be different for each substrate tested. The oxidation of ascorbate was most stable and less sensitive to the treatments. When mitochondria were stored in the dark and the cold, the decrease in oxidative phosphorylation followed first order kinetics. In individual preparations of muscle and heart mitochondria, protection of oxidative phosphorylation was found by adding candidate stabilizers, such as desferrioxamine, lazaroids, taurine, carnitine, phosphocreatine, N-acetylcysteine, Trolox-C and ruthenium red, implying a role for reactive oxygen species and calcium-ions in the in vitro damage at low temperature to oxidative phosphorylation. In heart mitochondria oxphos with pyruvate and palmitoylcarnitine was most labile followed by glutamate, succinate and ascorbate.We studied the effect of taurine, hypotaurine, carnitine, and desferrioxamine on the decay of oxphos with these substrates. 1 mM taurine (n = 6) caused a significant protection of oxphos with pyruvate, glutamate and palmitoylcarnitine, but not with the other substrates. 5 mM L-carnitine (n = 6), 1 mM hypotaurine (n = 3) and 0.1 mM desferrioxamine (n = 3) did not protect oxphos with any of the substrates at a significant level. These experiments were undertaken in the hope that the in vitro stabilizers can be used in future treatment of patients with defects in oxidative phosphorylation. (Mol Cell Biochem 174: 61–66, 1997)
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1006803807814
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  • 6
    Electronic Resource
    Electronic Resource
    Optimization of Upstream Profiles in Modelled Flow Over Complex Terrain (1997)
    Springer
    Boundary layer meteorology 83 (1997), S. 285-309 
    Details
    ISSN: 1573-1472
    Keywords: Adjoint ; Data assimilation ; Turbulence ; Complex terrain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract This paper describes an adjoint method for data assimilation intoupstream boundary conditions of numerical modelsusing optimal control theory. Mathematical formalisms are given along with the numerical implementation of the schemein a column model of the atmospheric boundary layer. The optimized mean and turbulence profiles are used as an upstream solutionin a model of turbulent flow in complex terrain. To contrast thiswith other methods, two solutions for flow over an isolatedhill are calculated, one with an optimized upstream solution andone with a simple surface-layer formulation for the upstream solution.These two solutions are compared to observations and analytical theory. The adjoint optimization method is shown to producesolutions of flow in complex terrain that are substantively differentat the two solutions, with the optimized solution giving more accurate results.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000229609412
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  • 7
    Electronic Resource
    Electronic Resource
    Coherent eddies and temperature structure functions for three contrasting surfaces. Part II: Renewal model for sensible heat flux (1997)
    Springer
    Boundary layer meteorology 84 (1997), S. 125-147 
    Details
    ISSN: 1573-1472
    Keywords: Turbulence ; Canopies ; Temperature ramps ; Renewal models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Sensible heat, latent heat, and other scalar fluxes cannot be measuredwithin short dense canopies, e.g., straw mulches, with standard approachessuch as eddy correlation, Bowen ratio-energy balance, aerodynamic, andvariance methods. However, recently developed surface renewal models, thatare based on the fact that most of the turbulent transfer within and abovecanopies is associated with large-scale coherent eddies, which are evidentas ramp patterns in scalar time series, offer a feasible solution. Wepresent a new air renewal model that calculates sensible heat flux atdifferent heights within and above a canopy from the average cubictemperature structure function, sampled at a moderate rate, and measuredaverage friction velocity. The model is calibrated and tested with datameasured above and within a Douglas-fir forest and above a straw mulch andbare soil. We show that the model describes half-hour variations ofsensible heat flux very well, both within the canopy and roughnesssublayers and in the inertial sublayer, for stable and unstable atmosphericconditions. The combined empirical coefficient that appears in the modelhas an apparently universal value of about 0.4 for all surfaces andheights, which makes application of the model particularly simple. Themodel is used to predict daytime and nighttime sensible heat flux profileswithin the straw mulch and within a small bare opening in the mulch.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000342918158
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  • 8
    Electronic Resource
    Electronic Resource
    Trajectory Curvature As A Selection Criterion For valid Lagrangian Stochastic Dispersion Models (1997)
    Springer
    Boundary layer meteorology 84 (1997), S. 411-425 
    Details
    ISSN: 1573-1472
    Keywords: Trajectories ; Turbulence ; Dispersion ; Diffusion ; Numerical models
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Among well-mixed multi-dimensional Lagrangian stochastic (LS) dispersion models, we observe that those in poorest agreement with observations produce ‘spiralling trajectories,’ with an associated reduction in dispersion. We therefore investigate statistics of increments dθ ' to the orientation θ'= arctan(W'/U') of the Lagrangian velocity-fluctuation vector – as a possible means to distinguish the better LS models within the well-mixed class. ‘Zero-spin’ models, having 〈 dθ'〉 = 0, are found to provide best agreement with observations. It is not clear however, whether imposition of the zero-spin property selects (in conjunction with the well-mixed condition) a unique model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000474206967
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  • 9
    Electronic Resource
    Electronic Resource
    Turbulent mixing of reactive gases in the convective boundary layer (1997)
    Springer
    Boundary layer meteorology 85 (1997), S. 197-222 
    Details
    ISSN: 1573-1472
    Keywords: Turbulence ; Chemistry ; Closure ; Convective boundary layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract We study the interactions of chemistry and turbulent mixing of tracersin the convective boundary layer with a second-order closure model,including higher order chemistry terms. In order to limit the number of predictive equations we prescribe the profiles for ¯w¯Θ, ¯w¯θ ¯θ and the lengthscale l. However, for model validation we treat temperature and humidity asinert tracers, and compare the results with profiles observed during theAir Mass Transformation Experiment, and with similarity expressions for thesurface layer. We find good agreement of the mean profiles, but the (co-)variances are slightly underpredicted. Furthermore, the model usesdiagnostic equations expressing third moments of concentration in terms ofsecond moments and their vertical derivatives. They are compared withlarge-eddy model results, showing good agreement and, therefore, thesimplifications are justified. The model is applied to the transport of two gases subject to one bimolecular reaction. The importance of concentration correlations on themean transformation rate is studied. For two gases diffusing in oppositedirections we find for moderate and fast chemistry a 50% and90% decreased transformation rate due to the negatively correlatedconcentrations. These values are similar to large-eddy results of Schumannand Sykes et al. For two bottom-up tracers we find that the covariance ofboth reactive species is either positive or negative, increasing or reducingthe effective transformation rate depending on the Damköhler number (the ratio of the turbulent and the chemistry timescale). A significantdirect influence of chemistry on the flux divergence is found in bothcases. According to the model the effective transport to mid-levels of theboundary layer is increased when two reactive tracers diffuse in oppositedirections, and decreased in the case of two bottom-up tracers.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000414710372
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  • 10
    Electronic Resource
    Electronic Resource
    Periodic vibro-impacts and their stability of a dual component system (1997)
    Springer
    Acta mechanica Sinica 13 (1997), S. 366-376 
    Details
    ISSN: 1614-3116
    Keywords: vibro-impact ; stability ; multiplicity
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The coexisting periodic impacting motions and their multiplicity of a kind of dual component systems under harmonic excitation are analytically derived. The stability condition of a periodic impacting motion is given by analyzing the propagation of small, arbitrary perturbation from that motion. In numerical simulations, the periodic impacting motions are classified according to the system states before and after an impact. The numerical results show that there exist many types of vibro-impacts and the bifurcation of periodic vibro-impacts is not smooth.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02487196
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  • 11
    Electronic Resource
    Electronic Resource
    AN EVALUATION OF SEVERAL TURBULENCE SCHEMES FOR THE PREDICTION OF MEAN AND TURBULENT FIELDS IN COMPLEX TERRAIN (1997)
    Springer
    Boundary layer meteorology 83 (1997), S. 43-73 
    Details
    ISSN: 1573-1472
    Keywords: Model evaluation ; Mesoscale ; Turbulence ; Dispersion ; Convective boundary layer ; Complex terrain
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A prognostic three-dimensional mesoscale model has been developed andused in one- and two-dimensional modes to evaluate ten local turbulenceclosure schemes. The schemes ranged from first-order to the two-equationprognostic schemes. Predictions by the models were compared for aone-dimensional convective boundary layer using mixed layer scaling andmeasurements to interpret the results. Two-dimensional simulations were alsoperformed for a sea-breeze flow and for flow over a hill. The results showedthat for all of the models considered, minor differences were produced in themean meteorological fields and in the vertical scalar fluxes, but majordifferences were apparent in the velocity variances and dissipation rate.Predicted tracer concentrations were very sensitive to the turbulence modelformulation for dispersion from a point source in the convective boundarylayer, particularly for the prediction of maximum concentrations. Predictedtracer concentrations from a surface volume source for the two-dimensionalsimulations were similar for all models, although the degree of mixing in themorning growth period produced some differences. Generally, good results forthe mean meteorological fields can be obtained with first-order schemes, evenif they underpredict the magnitude of turbulence in the convective boundarylayer, and reasonable tracer concentrations can also be obtained with thesemodels provided near-source effects are not important. The two-equationprognostic models performed best for the prediction of turbulence in theconvective boundary layer.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000217722421
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  • 12
    Electronic Resource
    Electronic Resource
    Non-local mixing of momentum in the convective boundary layer (1997)
    Springer
    Boundary layer meteorology 84 (1997), S. 1-22 
    Details
    ISSN: 1573-1472
    Keywords: Large-eddy simulation ; Turbulence ; Non-local closure ; Convective boundary layer
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Recently Frech and Mahrt proposed a closure scheme which includes alarge-scale stress term to represent the effects of non-local momentummixing in the convective boundary layer. Here large-eddy simulation (LES)datasets are used to evaluate the performance of this scheme across a rangeof stabilities between neutral and highly convective conditions, and as afunction of baroclinity. Generally the inclusion of the non-local term inthe closure model leads to results in better agreement with LES, althoughsome modifications to the model formulation are suggested.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000388830859
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  • 13
    Electronic Resource
    Electronic Resource
    A Three-Dimensional Correlation/Spectral Model for Turbulent Velocities in a Convective Boundary Layer (1997)
    Springer
    Boundary layer meteorology 85 (1997), S. 35-52 
    Details
    ISSN: 1573-1472
    Keywords: Turbulence ; Atmospheric convective boundary layer ; Correlation function
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract A three-dimensional model for correlation functions and spectra in theatmospheric, convective boundary layer (CBL) is presented. The modelincludes vertical inhomogeneities introduced by eddy-blocking at the ground.By assuming the disturbance to the turbulent flow resulting from the groundblocking is irrotational, an equation is developed which allows one to writethe inhomogeneous, two-dimensional (2D) cross spectra for the blocked flowin terms of the 2D cross spectra for a homogeneous flow. VonKármán's energy spectrum then is used to determine thehomogeneous, 2D cross spectra. Although there are only two adjustableparameters in the model, the variance and a length scale, the model is shownto agree quite well with a diversity of previous results for the CBL.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000418709945
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  • 14
    Electronic Resource
    Electronic Resource
    Multiresolution Flux Decomposition (1997)
    Springer
    Boundary layer meteorology 83 (1997), S. 117-137 
    Details
    ISSN: 1573-1472
    Keywords: Reynolds averaging ; Turbulence ; Time series ; Cospectra ; Sampling error
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Geophysical variables are orthogonally decomposed by averaging timeseries using different averaging lengths, referred to as a (Haar)multiresolution decomposition. This simple and economic decomposition isassociated with cospectra that formally satisfy Reynolds averaging rules foreach averaging length. The multiresolution decomposition provides a naturalestimate of the random error in estimating a mean turbulent flux. The Fourierand multiresolution decompositions are compared using aircraft data fromBOREAS.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000210427798
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  • 15
    Electronic Resource
    Electronic Resource
    Coherent eddies and temperature structure functions for three contrasting surfaces. Part I: Ramp model with finite microfront time (1997)
    Springer
    Boundary layer meteorology 84 (1997), S. 99-124 
    Details
    ISSN: 1573-1472
    Keywords: Turbulence ; Canopies ; Temperature ramps ; Structure functions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Geosciences , Physics
    Notes: Abstract Air temperature time series within and above canopies reveal ramp patternsassociated with coherent eddies that are responsible for most of thevertical transport of sensible heat. Van Atta used a simple step-changeramp model to analyse the coherent part of air temperature structurefunctions. However, his ocean data, and our own measurements for aDouglas-fir forest, straw mulch, and bare soil, reveal that even withoutlinearization his model cannot account for the observed decrease of thecubic structure function for small time lag. We found that a ramp model inwhich the rapid change at the end of the ramp occurs in a finite microfronttime can describe this decrease very well, and predict at least relativemagnitudes of microfront times between different surfaces. Averagerecurrence time for ramps, determined by analysis of the cubic structurefunction with the new ramp model, agreed well with values determined usingthe Mexican Hat wavelet transform, except at lower levels within theforest. Ramp frequency above the forest and mulch scaled very well withwind speed at the canopy top divided by canopy height. Within the forest,ramp frequency did not vary systematically with height. This is inaccordance with the idea that large-scale canopy turbulence is mostlygenerated by instability of the mean canopy wind profile, similar to aplane mixing layer. The straw mulch and bare soil experiments uniquelyextend measurements of temperature structure functions and ramp frequencyto the smallest scales possible in the field.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1000338817250
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  • 16
    Electronic Resource
    Electronic Resource
    Stability of viscoelastic flow around periodic arrays of cylinders (1997)
    Springer
    Rheologica acta 36 (1997), S. 367-383 
    Details
    ISSN: 1435-1528
    Keywords: Viscoelastic flow ; arrays of cylinders ; stability ; porous media
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Low Reynolds number flow of Newtonian and viscoelastic Boger fluids past periodic square arrays of cylinders with a porosity of 0.45 and 0.86 has been studied. Pressure drop measurements along the flow direction as a function of flow rate as well as flow visualization has been performed to investigate the effect of fluid elasticity on stability of this class of flows. It has been shown that below a critical Weissenberg number (Wec), the flow in both porosity cells is a two-dimensional steady flow, however, pressure fluctuations appear above Wec which is 2.95±0.25 for the 0.45 porosity cell and 0.95±0.08 for the higher porosity cell. Specifically, in the low porosity cell as the Weissenberg number is increased above Wec a transition between a steady two-dimensional to a transient three-dimensional flow occurs. However, in the high porosity cell a transition between a steady two-dimensional to a steady three-dimensional flow consisting of periodic cellular structures along the length of the cylinder in the space between the first and the second cylinder occurs while past the second cylinder another transition to a transient three-dimensional flow occurs giving rise to time- dependent cellular structures of various wavelengths along the length of the cylinder. Overall, the experiments indicate that viscoelastic flow past periodic arrays of cylinders of various porosities is susceptible to purely elastic instabilities. Moreover, the instability observed in lower porosity cells where a vortex is present between the cylinders in the base flow is amplifieds spatially, that is energy from the mean flow is continuously transferred to the disturbance flow along the flow direction. This instability gives rise to a rapid increase in flow resistance. In higher porosity cells where a vortex between the cylinders is not present in the base flow, the energy associated with the disturbance flow is not greatly changed along the flow direction past the second cylinder. In addition, it has been shown that in both flow cells the instability is a sensitive function of the relaxation time of the fluid. Hence, the instability in this class of flows is a strong function of the base flow kinematics (i.e., curvature of streamlines near solid surfaces), We and the relaxation time of the fluid.
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    URL: http://dx.doi.org/10.1007/BF00396324
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  • 17
    Electronic Resource
    Electronic Resource
    Stability of viscoelastic flow around periodic arrays of cylinders (1997)
    Springer
    Rheologica acta 36 (1997), S. 367-383 
    Details
    ISSN: 1435-1528
    Keywords: Key words Viscoelastic flow ; arrays of cylinders ; stability ; porous media
    Source: Springer Online Journal Archives 1860-2000
    Topics: Chemistry and Pharmacology , Physics
    Notes: Abstract Low Reynolds number flow of Newtonian and viscoelastic Boger fluids past periodic square arrays of cylinders with a porosity of 0.45 and 0.86 has been studied. Pressure drop measurements along the flow direction as a function of flow rate as well as flow visualization has been performed to investigate the effect of fluid elasticity on stability of this class of flows. It has been shown that below a critical Weissenberg number (We c ), the flow in both porosity cells is a two-dimensional steady flow, however, pressure fluctuations appear above We c which is 2.95±0.25 for the 0.45 porosity cell and 0.95±0.08 for the higher porosity cell. Specifically, in the low porosity cell as the Weissenberg number is increased above We c a transition between a steady two-dimensional to a transient three-dimensional flow occurs. However, in the high porosity cell a transition between a steady two-dimensional to a steady three-dimensional flow consisting of periodic cellular structures along the length of the cylinder in the space between the first and the second cylinder occurs while past the second cylinder another transition to a transient three-dimensional flow occurs giving rise to time- dependent cellular structures of various wavelengths along the length of the cylinder. Overall, the experiments indicate that viscoelastic flow past periodic arrays of cylinders of various porosities is susceptible to purely elastic instabilities. Moreover, the instability observed in lower porosity cells where a vortex is present between the cylinders in the base flow is amplified spatially, that is energy from the mean flow is continuously transferred to the disturbance flow along the flow direction. This instability gives rise to a rapid increase in flow resistance. In higher porosity cells where a vortex between the cylinders is not present in the base flow, the energy associated with the disturbance flow is not greatly changed along the flow direction past the second cylinder. In addition, it has been shown that in both flow cells the instability is a sensitive function of the relaxation time of the fluid. Hence, the instability in this class of flows is a strong function of the base flow kinematics (i.e., curvature of streamlines near solid surfaces), We and the relaxation time of the fluid.
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  • 18
    Electronic Resource
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    A reaction-diffusion equation for a cyclic system with three components (1997)
    Springer
    Journal of statistical physics 87 (1997), S. 1145-1164 
    Details
    ISSN: 1572-9613
    Keywords: Fisher-Kolmogorov equation ; traveling fronts ; fixed points ; population dynamics ; bifurcations ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The one-dimensional reaction-diffusion equations for the process (D) $$A + B \to 2A,B + C \to 2B,C + A \to 2C$$ are extended to include the counteracting reactions (R) $$A + 2B \to 3B,B + 2C \to 3C,C + 2A \to 3A$$ which have a reaction rate α relative to the direct process (D). This process can be seen as a three-component version of the reaction which is described by the Fisher-Kolmogorov equation. The fixed points of the equations are studied as a function of α. It is shown that the equations admit solutions which consist of a series of traveling fronts. Other solutions exist which are traveling periodic waves. A very remarkable fact is that for these waves exact expressions can be constructed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF02181277
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  • 19
    Electronic Resource
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    Stable, recombinant expression of human insulin-like growth factor binding protein-1 (hIGFBP-1) in Chinese hamster ovary (CHO) cells (1997)
    Springer
    Cytotechnology 24 (1997), S. 193-200 
    Details
    ISSN: 1573-0778
    Keywords: CHO cells ; DHFR ; IGFBP-1 ; stability
    Source: Springer Online Journal Archives 1860-2000
    Topics: Biology , Medicine , Process Engineering, Biotechnology, Nutrition Technology
    Notes: Abstract Stable expression of human insulin-like growth factor of binding protein-1 (hIGFBP-1)at high levels has been achieved in Chinese hamster ovary (CHO) cells by co-transfection and subsequent co-amplification of expression vectors containing the hIGFBP-1 cDNA and a dihydrofolate reductase (DHFR) cDNA gene into DHFR-deficient cells. Stepwise selection of the DHFR+ transformants in increasing concentrations of methotrexate (MTX) generated cells which had high copy numbers of the hIGFBP-1 gene (around 100 copies in cells amplified in medium containing 100 nM MTX). Expression of hIGFBP-1 in mixed clones was found to increase with increasing copy number and an apparent correlation between intra- and extracellular levels of hIGFBP-1 produced by these cells was observed. It was further observed that continuous cultivation over eight months in medium supplemented with 100 nM MTX increased the production of hIGFBP-1 25 times. The productivity did not increase further after five more months cultivation in MTX containing medium. A subcloning of this cell line gave clones with an even higher productivity. Further amplification in 500 nM or 1 uM MTX did not increase the hIGFBP-1 production.
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    URL: http://dx.doi.org/10.1023/A:1007999512662
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  • 20
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    Remarks on the Instability of an Incompressible and Isotropic Hyperelastic, Thick-Walled Cylindrical Tube (1997)
    Springer
    Journal of elasticity 48 (1997), S. 218-239 
    Details
    ISSN: 1573-2681
    Keywords: stability ; nonlinear elasticity ; Mooney-Rivlin material ; incompressible material ; thick-walled tube
    Source: Springer Online Journal Archives 1860-2000
    Topics: Mechanical Engineering, Materials Science, Production Engineering, Mining and Metallurgy, Traffic Engineering, Precision Mechanics , Physics
    Notes: Abstract The problem of instability of a hyperelastic, thick-walled cylindrical tube was first studied by Wilkes [1] in 1955. The solution was formulated within the framework of the theory of small deformations superimposed on large homogeneous deformations for the general class of incompressible, isotropic materials; and results for axially symmetrical buckling were obtained for the neo-Hookean material. The solution involves a certain quadratic equation whose characteristic roots depend on the material response functions. For the neo-Hookean material these roots always are positive. In fact, here we show for the more general Mooney–Rivlin material that these roots always are positive, provided the empirical inequalities hold. In a recent study [2] of this problem for a class of internally constrained compressible materials, it is observed that these characteristic roots may be real-valued, pure imaginary, or complex-valued. The similarity of the analytical structure of the two problems, however, is most striking; and this similarity leads one to question possible complex-valued solutions for the incompressible case. Some remarks on this issue will be presented and some new results will be reported, including additional results for both the neo-Hookean and Mooney–Rivlin materials.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1023/A:1007423306486
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