Showing papers in "Canadian Journal of Physics in 1990"
TL;DR: In this article, a film of a nonwetting liquid is not stable if it is too thin and is unstable against sparsification and metastability via nucleation and growth of dry spots.
Abstract: (i) A film of a nonwetting liquid is not stable. If it is thick (thickness e ≥ 1000 A) it is metastable and evolves via nucleation and growth of a dry spot. If it is thin, it is unstable against sp...
418 citations
TL;DR: In this paper, a cell dynamical system model for atmospheric flows is developed by consideration of microscopic domain eddy dynamical processes, which enables formulation of a simple closed set of governing equations for the prediction and description of observed atmospheric flow structure characteristics.
Abstract: The complex spatiotemporal patterns of atmospheric flows that result from the cooperative existence of fluctuations ranging in size from millimetres to thousands of kilometres are found to exhibit long-range spatial and temporal correlations. These correlations are manifested as the self-similar fractal geometry of the global cloud cover pattern and the inverse power-law form for the atmospheric eddy energy spectrum. Such long-range spatiotemporal correlations are ubiquitous in extended natural dynamical systems and are signatures of deterministic chaos or self-organized criticality. In this paper, a cell dynamical system model for atmospheric flows is developed by consideration of microscopic domain eddy dynamical processes. This nondeterministic model enables formulation of a simple closed set of governing equations for the prediction and description of observed atmospheric flow structure characteristics as follows. The strange-attractor design of the field of deterministic chaos in atmospheric flows co...
65 citations
TL;DR: The question of the physical basis of selective lipid–protein interaction mechanisms is addressed and the outstanding viscoelastic properties of plasma membranes and their r...
Abstract: The cell plasma is a composite type of material that is made up of a two-dimensional liquid crystal (lipid–protein bilayer) to which a macromolecular network (the cytoskeleton) is loosely coupled. The latter may be approximately two dimensional as in the case of the erythrocytes or may extend throughout the whole cell cytoplasm. Owing to this combination of two states of matter, the membrane combines the dynamics and flexibility of a fluid with the mechanical stability of a solid. Owing to its low dimensionality, the local structure of the bilayer or the global shape of cells may be most effectively controlled and modulated by biochemical signals such as macromolecular adsorption. The present contribution deals with comparative studies of the local and global dynamic properties of biological and artificial membranes. In the first part the question of the physical basis of selective lipid–protein interaction mechanisms is addressed and the outstanding viscoelastic properties of plasma membranes and their r...
57 citations
TL;DR: In this paper, numerical simulations of three distinct models of excitable media (two-variable Oregonator, with both variables diffusing equally; and piecewise linear A and B kinetics, with only the propagator va...
Abstract: Numerical simulations of three distinct models of excitable media (two-variable Oregonator, with both variables diffusing equally; and piecewise linear A and B kinetics, with only the propagator va...
55 citations
TL;DR: In this paper, a multimode continuous-wave dye laser around instabilities is interpreted using the concept of pragmatic information, which contains aspects of synergetics and nonequilibrium thermodynamics.
Abstract: Observations of the behavior of a multimode continuous-wave dye laser around instabilities are interpreted using the concept of pragmatic information. It is demonstrated that this concept contains aspects of two different approaches toward the description of self-organizing system, namely, those of synergetics and of nonequilibrium thermodynamics. Both of them prove to be particularly relevant in the considered example. The key quantities of the two approaches (efficiency and entropy production) are related to a measure of pragmatic information. The significance of this measure for general issues referring to meaning, complexity, and evolution in self-organizing processes is indicated.
48 citations
TL;DR: A recent systematic study of the effects of radiations on cells has revealed that there are unifying features in the observed responses of different cell types to induction of different effects, and by different radiations as mentioned in this paper.
Abstract: Insult from ionizing radiation is in the form of microscopic tracks that are highly structured from the atomic level upwards. The internal composition of mammalian cells, too, is highly structured, from dimensions smaller than the DNA molecule (diameter ~2 nm) up to the entire cell . There is a wide spectrum of initial physical and chemical damage, subsequent biochemical modification, and final cellular response. The vast majority of the physical, chemical, and biochemical damage is apparently of little relevance to final observable cellular effects. This predominance of "irrelevant" damage masks the nature of that which is of prime relevance. Nevertheless, systematic studies of the effects of radiations on cells have revealed that there are unifying features in the observed responses of different cell types to induction of different effects, and by different radiations. This implies that there are dominant mechanisms that are open to kinetic analysis. Relevant processes may be dominated by the non-linear...
47 citations
TL;DR: In this paper, the principal spatial structures characteristic of freezing soils and the underlying processes in the broader context of geomorphic self-organization are discussed. But the authors do not consider the effect of local relief, soil cracks, or segregation of mineral material according to size.
Abstract: Freezing in moist fine-grained soils is a highly nonhomogeneous process. It involves transport of water to freezing sites and growth of distinct ice bodies separated by soil domains free of ice. On a much larger scale, recurrent ice growth and thawing of cold regions produce a rich diversity of patterns in soils; these patterns can be defined by local relief, soil cracks, or segregation of mineral material according to size. This paper reviews the principal spatial structures characteristic of freezing soils and discusses the underlying processes in the broader context of geomorphic self-organization.
43 citations
TL;DR: In this paper, an analytic solution for the problem of plane electromagnetic-wave scattering by an arbitrary configuration of N dielectric spheres is obtained, and the boundary condition is imposed using the translational addition theorem for vector spherical wave functions.
Abstract: An analytic solution is obtained for the problem of plane electromagnetic-wave scattering by an arbitrary configuration of N dielectric spheres. The multipole expansion method is employed, and the boundary condition is imposed using the translational addition theorem for vector spherical wave functions. A system of simultaneous linear equations is given in matrix form for the scattering coefficients. An approximate solution, which has been developed and employed by the authors for the scattering by N conducting spheres, is extended to the dielectric spheres case. Plots for the normalized backscattering, bistatic, and forward-scattering cross sections are presented over wide ranges of permittivity, size, and electrical separations between the neighbouring spheres. The results show a reduction in the normalized backscattering and bistatic cross sections for certain choices of permittivity relative to conducting arrays of spheres of the same dimensions and separations.
39 citations
TL;DR: In this article, a picosecond time-resolved fluorescence spectrophotometer was used to measure the excitation energy relaxation of the dye molecule in the Langmuir-Blodgett monolayers.
Abstract: Fluorescence-decay curves and time-resolved fluorescence spectra of N, N′-dioctadecylrhodamine B in Langmuir–Blodgett monolayers have been measured by means of a picosecond time-resolved fluorescence spectrophotometer. The excitation energy relaxation of the dye molecule in the monolayers was compared at 295 and 80 K in the concentration range from 0.02 to 31 mol%. The relaxation of the dynamic Stokes shift was found to decay logarithmically with time in longer time regions when the concentration of N, N′-dioctadecylrhodamine B < 5 mol%. The fluorescence decays can be analyzed by an equation including a stretched exponential function. The mechanisms of singlet excitation-energy relaxation were interpreted in terms of (i) the energy migration among energetically disordered monomer sites represented by ultrametric space (hierarchical energy distribution) or the Gaussian distribution of the density of excited states and (ii) the energy trapping by two-dimensional aggregates. It was found that the relaxation ...
34 citations
TL;DR: In this article, the stochastic treatment of reaction kinetics in micellar solutions is presented by taking, as a typical example of a reaction, the quenching of an excited probe by a quencher, both solubilized in a micelle.
Abstract: The stochastic treatment of reaction kinetics in micellar solutions is presented by taking, as a typical example of a reaction, the quenching of an excited probe by a quencher, both solubilized in a micelle. Three cases are considered concerning migration of probes and quenchers between micelles, namely, (i) the case where only quenchers migrate, (ii) the case where only probes migrate, and (iii) the case where micelles exchange solubilizates by fusion–fission processes. The decay curves of the excited probes are calculated for the three cases and compared with each other. Whether it is possible to distinguish between the three cases on the basis of the experimentally obtained decay curves is discussed.
29 citations
TL;DR: In this paper, the angular correlation technique of positron annihilation has been used to detect and measure the localized bubble state of positronium (Ps) in liquid Ne, Ar, Kr, H2, and N2 and in liquid and solid He at various pressures and temperatures.
Abstract: The angular-correlation technique of positron annihilation has been used to detect and measure the localized bubble state of positronium (Ps) in liquid Ne, Ar, Kr, H2, and N2 and in liquid and solid He at various pressures and temperatures. No bubble state was seen in liquid O2 or in solid Ne and Ar. The dynamics of bubble formation is not yet understood. In the cases where theoretical calculations, and adequate data, exist, viz. He, Ar, and H2, there is reasonable agreement for the momentum of the photons from the annihilation of positrons with the outer electrons of these atoms. The Ps annihilations from the self-trapped bubble state are reasonably well described in terms of a simple finite potential-well model.
TL;DR: In this paper, rotational analyses of vibrational levels of the B3Πg state, located above the dissociation threshold N(4S) + N( 4S+N(S), were performed from a high-resolution emission spectrum recorded by Fourier transducers.
Abstract: Rotational analyses of vibrational levels of the B3Πg state, located above the dissociation threshold N(4S) + N(4S) were performed from a high-resolution emission spectrum recorded by Fourier trans...
TL;DR: The reaction ordinate Rω as discussed by the authors was used to derive a transform of temperature and time that enables the correlation of extensive kinetic data sets by means of three constants: β, γ, and the mean activation energy Ea.
Abstract: The thermal cracking of heavy oils has been modelled on the basis of combinations of first-order reactions in order to describe the behaviour of pseudocomponents with time and temperature of reaction. An alternative formulation uses the concept of a time-varying rate constant of the formwhere β is the rate constant and γ is an exponent that has values of 0 < γ ≤ 1.0. This was used to derive a transform of temperature and time that we have called the reaction ordinate Rω, which enables the correlation of extensive kinetic data sets by means of three constants: β, γ, and the mean activation energy Ea. We demonstrate this correlation for two sets of published data. The values of γ were less than unity and are interpreted in terms of the Kohlrausch function, leading to the hypothesis of a continuous distribution of activation energies in the system. This form of correlation is similar to that of the continuous-time random-walk relaxation phenomena that has been explained in many ways including fractal time, a...
TL;DR: In this article, the problem of multiple scattering of a plane electromagnetic wave incident on N closely spaced perfectly conducting spheres is solved analytically by expanding the incident and scattering fields i.e.
Abstract: The problem of multiple scattering of a plane electromagnetic wave incident on N closely spaced perfectly conducting spheres is solved analytically by expanding the incident and scattering fields i...
TL;DR: In this paper, the authors focus on large Poincare systems with continuous spectrum of the Liouville operator and show that resonances lead to a dynamics of correlations, which can be analyzed using the theory of subdynamics.
Abstract: Traditionally, self-organization has been studied using macroscopic phenomenological descriptions. Recent computer simulations show that "dissipative structures" may be obtained through dynamical programs without any macroscopic assumptions. Self-organization is rooted in dynamics. This leads to the question, "what type of dynamical laws permit self-organization?" The answer refers to unstable dynamical systems, which were widely studied after the pioneering work of Kolmogorov. We concentrate our work on large Poincare systems with continuous spectrum of the Liouville operator, a generalization of Poincare's nonintegrable systems. Examples are collisions or quantum jumps. We show that resonances lead to a dynamics of correlations, which can be analyzed using our recent theory of subdynamics. We decompose the dynamical evolution into a set of independent processes. As an example, we study radiation processes as well as the transformation of classical dynamics information into order or disorder processes. W...
TL;DR: In this article, the linear stability of a viscoelastic fluid-saturated sparsely packed porous layer heated from below is studied analytically using the Darcy-Brinkman-Jeffreys model with different boundary combinations.
Abstract: The linear stability of a viscoelastic fluid-saturated sparsely packed porous layer heated from below is studied analytically using the Darcy-Brinkman-Jeffreys model with different boundary combinations. The Galerkin technique is employed to determine the criterion for the onset of oscillatory convection. The effects of the viscoelastic parameters, the Prandtl number, and the porous parameter on the critical Rayleigh number, the wave number, and the frequency are analyzed. The results are compared with those obtained for both a Darcy-Jeffrey fluid and a Maxwell fluid. It is shown that under certain conditions for the viscoelastic parameters, the flow is overstable. The possibility of the occurrence of bifurcation is also discussed.
TL;DR: In this paper, the activation energy, vibrational frequency, and surface diffusion jumps of a single adatom on a perfect (111) surface were determined with a conjugate gradient energy-minimization procedure.
Abstract: The activation energy, vibrational frequency, and surface-diffusion jumps of a single adatom on a perfect (111) surface were studied using the embedded-atom method. The activation energy was determined with a conjugate gradient energy-minimization procedure. The surface adatom was moved in steps across the (111) plane through a saddle point. The adatom position was fixed within (parallel to) the (111) plane; but, the Ag adatom was free to relax, normal to the (111) plane. In this way the adatom was free to ride up over the saddle point; so that at each fixed position within the (111) plane the Ag adatom was free to move to its minimum energy. Also all of the atoms within the Ag crystal were free to relax to minimum-energy positions as the Ag adatom was moved across the surface. The minimum activation energy calculated for adatom diffusion was 0.058 eV. The embedded-atom method was also combined with a molecular dynamics simulation to observe the vibrations of the surface atoms and the adatom and to observ...
TL;DR: In this article, the authors investigated the effect of second-ion species on the characteristics of a large-amplitude ion-acoustic double layers (IADL) in a collisionless, unmagnetized plasma consisting of hot and col...
Abstract: We have investigated the effect of second-ion species on the characteristics of a large-amplitude ion-acoustic double layers (IADL) in a collisionless, unmagnetized plasma consisting of hot and col...
TL;DR: In this paper, a particle's random walk is analyzed analytically and with the help of Monte-Carlo simulation techniques, and the results of the simulations allow a further generalization to random walks with a nonconstant mean free path, and also allow the study of the radial distribution f(r) of particles after the walk.
Abstract: We study various characteristics of a particle's random walk both analytically and with the help of Monte-Carlo simulation techniques. With the analytical approach, we derive the expressionwhich relates the mean-square displacement to (i) the number of steps N in the walk, (ii) the mean-square displacement on each of the steps, and (iii) a coefficient of collision anisotropy A defined as the average value of the cosine of the scattering angle θ. This expression is general in the sense that it holds for any value of N and A. It is, however, restricted to cases where the mean free path is constant throughout the random walk. The results of the simulations allow a further generalization to random walks with a nonconstant mean free path. They also allow the study of the radial distribution f(r) of particles after the walk. We find that a set of six functions fi(r) is necessary to give a satisfactory description of the particles' radial distribution for arbitrary values of N and A.
TL;DR: In this paper, chaotic time-series analysis has been applied to either abstract model systems or experimental systems with unknown or poorly understood equations of motion, and the authors present an approach to chaotic time series analysis for both abstract model and experimental systems.
Abstract: Previous applications of chaotic time-series analysis have focussed on either abstract model systems or experimental systems with unknown or poorly understood equations of motion. We present an ana...
TL;DR: In this article, the atmospheric oxygen band due to magnetic dipole transitions was studied by a diode laser absorption spectroscopy combined with a Zeeman modulation technique, and the high-resolution spectrum of the spectrum was obtained.
Abstract: The atmospheric oxygen band due to magnetic dipole transitions was studied by a diode laser absorption spectroscopy combined with a Zeeman modulation technique. The high-resolution spectrum of the ...
TL;DR: In this paper, the authors present a phenomenological description of the fracture propagation process in terms of two ingredients: (i) a threshold stress σc associated with chemical scission or with plastic flow; (ii) a "suction" process with a suction velocity proportional to the local stress, which ends when the volume transfer (per unit area) has reached a certain limit hf.
Abstract: The industrial importance of adhesives is constantly increasing. Yet it is difficult to systematize the vast amount of practical knowledge, which has accumulated, covering chemistry, interfacial physics, and mechanics. This review describes an attempt to bridge the gap between polymer science and fracture mechanics. It focuses on weak mechanical junctions. Examples can be found at glass–rubber interfaces or at glass–plastic interfaces, where the glass has been grafted with polymer chains that promote adhesion. When a fracture propagates along such a junction, the dissipation tends to be localized in the junction region. We present a phenomenological description of this process in terms of two ingredients: (i) a threshold stress σc associated with chemical scission or with plastic flow; (ii) a "suction" process with a suction velocity proportional to the local stress σ, which ends when the volume transfer (per unit area) has reached a certain limit hf. Assuming no cavitation (no crazes), we are led to expe...
TL;DR: In this paper, an exact solution to the problem of scattering of a plane electromagnetic wave by two dielectric prolate spheroids with parallel major axes is obtained by expanding the incident, scattered, and transmitted electric and magnetic fields in terms of an appropriate set of vector spheroidal eigenfunctions.
Abstract: An exact solution to the problem of scattering of a plane electromagnetic wave by two dielectric prolate spheroids with parallel major axes is obtained by expanding the incident, scattered, and transmitted electric and magnetic fields in terms of an appropriate set of vector spheroidal eigenfunctions. The incident wave is considered to be a monochromatic, uniform plane electromagnetic wave of arbitrary polarization and angle of incidence. The boundary conditions are imposed by expressing the electromagnetic field scattered by one spheroid in terms of the spheroidal coordinates attached to the other, using the translational addition theorems for vector spheroidal wave functions. The column matrix of the total transmitted and scattered field-expansion coefficients is equal to the product of a square matrix, which is independent of the direction and polarization of the incident wave, and the column matrix of the known incident field-expansion coefficients. The solution of the associated set of algebraic equa...
TL;DR: In this paper, the first single-crystal Mossbauer study of mica has been carried out and the room-temperature spectra for different orientations (with respect to the -γ-ray flux) of a well-characterized monocrystalli...
Abstract: In this first single-crystal Mossbauer study of mica we have measured the room-temperature spectra for different orientations (with respect to the -γ-ray flux) of a well-characterized monocrystalli...
TL;DR: In this paper, the authors analyze the fluorescence decay kinetics of pyrene covalently attached to the surface of fumed silica particles that are suspended in methanol.
Abstract: The observation of a stretched exponential response in chemical kinetics at solid–liquid interfaces is an indicator of solid surface disorder. In this contribution, we review earlier relaxation kinetics studies of solid surface disorder and the statistical criteria analyzing kinetic data that do not fit single exponential. We draw on these concepts to interpret the fluorescence decay kinetics of pyrene covalently attached to the surface of fumed silica particles that are suspended in methanol. This surface probe exhibits stretched exponential behavior of the form f(t) = exp[−(kt)β] in the decay of its excited-state populations. The addition of iodine quencher increases the average decay rate, but does not alter the nonlinear exponent β. These results, along with the diffusional length of the iodine quencher, the photophysics of the probe, and the chemistry of the interface, indicate that the kinetic inhomogeneity is dominated by dispersion of surface energies, rather than by diffusional excursions of the ...
TL;DR: In this paper, a determination of the two loop renormalization group functions for in four dimensions was made for the quantum field theory in terms of the number of loops in the group.
Abstract: Analytic continuation leads to the finite renormalization of a quantum field theory. This is illustrated in a determination of the two loop renormalization group functions for in four dimensions.
TL;DR: In this paper, the authors presented the spherically symmetric metric tensor in double-null coordinates and computed the field equations, kinematical quantities, and Riemann invariants for a perfect-fluid stress-energy tensor.
Abstract: In this paper we have sought solutions of the nonstatic spherically symmetric field equations that exhibit nonzero shear. The Lorentzian-warped product construction is used to present the spherically symmetric metric tensor in double-null coordinates. The field equations, kinematical quantities, and Riemann invariants are computed for a perfect-fluid stress-energy tensor. For a special observer, one of the field equations reduces to a form that admits wavelike solutions. Assuming a functional relationship between the metric coefficients, the remaining field equation becomes a second-order nonlinear differential equation that may be reduced as well.
TL;DR: In this article, the results of a study on water-hexadecane microemulsions at different water contents were obtained at 20 MHz and 310 K. The results showed that all the systems without free water were characterized by 1H spin-spin and spin-lattice relaxation curves well described by two exponential functions.
Abstract: The purpose of the research was to establish whether the water configurations, detected by previous differential scanning calorimetry (DSC) analysis, could give rise to different or characteristic nuclear magnetic resonance relaxations. We report the results of a study on water–hexadecane microemulsions at different water contents. The 1H spin–spin and spin–lattice relaxation curves were obtained at 20 MHz and 310 K. The trends of all best-fit relaxation parameters versus water concentration were compared with those obtained for D2O microemulsions with the same experimental conditions and fitting procedures. Two different H2O microemulsion "states" were identified: (i) all the systems without "free water" (defined by DSC as water melting at 273 K) were characterized by 1H spin–spin and spin–lattice relaxation curves well described by two exponential functions and (ii) all the systems with free water were characterized by relaxation curves well described by three exponential functions. The identification o...
TL;DR: In this article, the authors reviewed the recent studies on slip failure nucleation, which leads to the mechanical instability that gives rise to a dynamically propagating shear rupture, constitutive behavior during the local breakdown process near the propagating tip of the slipping zone, and physical modeling of the earthquake-source process based on the constitutive relation inferred from laboratory experiments.
Abstract: This paper reviews our recent studies on (i) slip failure nucleation, which leads to the mechanical instability that gives rise to a dynamically propagating shear rupture, (ii) constitutive behavior during the local breakdown process near the propagating tip of the slipping zone, and (iii) the physical modeling of the earthquake-source process based on the constitutive relation inferred from laboratory experiments. Laboratory studies were done using a simulated fault in rock in the brittle regime under a mode II crack-growth condition, to gain a deeper understanding of the earthquake-source process, which is considered to be dynamically propagating shear rupture in the earth. A stable but accelerating phase of nucleation locally precedes an unstable dynamically propagating rupture even in the brittle regime. The appearance of a sizable zone of such nucleation is related to a nonuniform distribution of the crack-growth resistance on the fault. The local shear strength degrades to a residual friction stress...
TL;DR: In this paper, Ab initio configuration interaction (CI) studies were performed on low-lying linear and nonlinear states of methinophosphide (HCP), using large basis sets with polarization and s, p Rydberg functions, and extensive multireference CI wave functions.
Abstract: Ab initio configuration interaction (CI) studies were performed on low-lying linear and nonlinear states of methinophosphide (HCP), using large basis sets with polarization and s, p Rydberg functions, and extensive multireference CI wave functions. Potential curves for linear states of HCP as functions of RCP and RCH and for nonlinear states as functions of αHCP were obtained, from which spectroscopic constants Te, Re, and ωe were evaluated. For the X1Σ+ ground state, the energy of dissociation into H + CP and the dipole moment were also calculated. The assignment of states based on the observed spectrum had to be revised in several instances. The a state remained 13Σ+ (or 13A′), but the state became 13A″, the state, 13Δ, the A and states remained 11A″ and 21A′, respectively, was not seen as a seperate state, and became 13Σ−. In the energy range from 0 to 8 eV, 22 linear and 11 nonlinear stable states were found. Nonlinear states were stabilized for excitations from π(9a′, 2a″) into the in-plane component...