Author
David S. Cannell
Other affiliations: Memorial University of Newfoundland
Bio: David S. Cannell is an academic researcher from University of California, Santa Barbara. The author has contributed to research in topics: Convection & Light scattering. The author has an hindex of 40, co-authored 128 publications receiving 5921 citations. Previous affiliations of David S. Cannell include Memorial University of Newfoundland.
Papers published on a yearly basis
Papers
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TL;DR: Experimental results obtained in microgravity during the flight of the FOTON M3 satellite find that during a diffusion process a dilute polymer solution exhibits scale-invariant concentration fluctuations with sizes ranging up to millimetres, and relaxation times as large as 1,000 s.
Abstract: Spatial scale invariance represents a remarkable feature of natural phenomena. A ubiquitous example is represented by miscible liquid phases undergoing diffusion. Theory and simulations predict that in the absence of gravity diffusion is characterized by long-ranged algebraic correlations. Experimental evidence of scale invariance generated by diffusion has been limited, because on Earth the development of long-range correlations is suppressed by gravity. Here we report experimental results obtained in microgravity during the flight of the FOTON M3 satellite. We find that during a diffusion process a dilute polymer solution exhibits scale-invariant concentration fluctuations with sizes ranging up to millimetres, and relaxation times as large as 1,000 s. The scale invariance is limited only by the finite size of the sample, in agreement with recent theoretical predictions. The presence of such fluctuations could possibly impact the growth of materials in microgravity.
105 citations
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TL;DR: In this article, a preuve experimentale du fait que, des solutions de polymeres flexibles sont caracterises par une longueur universelle dependant de la concentration qui est aisement mise en loi d'echelle pour etre independante de la masse moleculaire and de la qualite du solvant.
Abstract: Premiere preuve experimentale du fait que, des solutions de polymeres flexibles sont caracterises par une longueur universelle dependant de la concentration qui est aisement mise en loi d'echelle pour etre independante de la masse moleculaire et de la qualite du solvant
92 citations
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TL;DR: In this article, the velocity of a Taylor vortex front propagating into an unstable Couette state in rotating Couette-Taylor flow and of the wavelength selected by this dynamical process were reported.
Abstract: This Letter reports experimental measurements of the velocity $v$ of a Taylor vortex front propagating into an unstable Couette state in rotating Couette-Taylor flow and of the wavelength selected by this dynamical process. The data are consistent with a constant velocity $v\ensuremath{\propto}{\ensuremath{\epsilon}}^{\frac{1}{2}}$, as predicted from an amplitude equation, but are nearly a factor of 2 smaller than that prediction. Recent dynamic experiments on the onset of Taylor vortex flow by Park, Crawford, and Donnelly are explained in terms of vortex-front propagation.
88 citations
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TL;DR: The structure factor of the fluctuating convection rolls is consistent with the expected rotational invariance of the system and the fluctuation intensity is found to be proportional to 1/{radical}{minus}{epsilon}.
Abstract: We report quantitative experimental results for the intensity of noise-induced fluctuations below the critical temperature difference {Delta}{ital T}{sub {ital c}} for Rayleigh-Benard convection. The structure factor of the fluctuating convection rolls is consistent with the expected rotational invariance of the system. In agreement with predictions based on stochastic hydrodynamic equations, the fluctuation intensity is found to be proportional to 1/{radical}{minus}{epsilon}, where {epsilon}{equivalent_to}{Delta}{ital T}/{Delta}{ital T}{sub {ital c}}{minus}1. The noise power necessary to explain the measurements agrees with the prediction for thermal noise.
86 citations
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TL;DR: Experimental and theoretical results for the absolute and convective instability boundaries in Taylor-Couette flow with imposed axial flow as a function of the axial Reynolds number confirm that noise-sustained structures of traveling vortices exist in much of the convective unstable regime.
Abstract: We report experimental and theoretical results for the absolute and convective instability boundaries in Taylor-Couette flow with imposed axial flow as a function of the axial Reynolds number. Experiment and theory agree quantitatively. In the downstream region of a large-aspect-ratio system, noise-sustained structures of traveling vortices exist in much of the convectively unstable regime. These structures have a nearly time-independent amplitude, but a noisy phase. The phase noise ceases abruptly upon crossing the absolute instability boundary.
82 citations
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TL;DR: A comprehensive review of spatiotemporal pattern formation in systems driven away from equilibrium is presented in this article, with emphasis on comparisons between theory and quantitative experiments, and a classification of patterns in terms of the characteristic wave vector q 0 and frequency ω 0 of the instability.
Abstract: A comprehensive review of spatiotemporal pattern formation in systems driven away from equilibrium is presented, with emphasis on comparisons between theory and quantitative experiments. Examples include patterns in hydrodynamic systems such as thermal convection in pure fluids and binary mixtures, Taylor-Couette flow, parametric-wave instabilities, as well as patterns in solidification fronts, nonlinear optics, oscillatory chemical reactions and excitable biological media. The theoretical starting point is usually a set of deterministic equations of motion, typically in the form of nonlinear partial differential equations. These are sometimes supplemented by stochastic terms representing thermal or instrumental noise, but for macroscopic systems and carefully designed experiments the stochastic forces are often negligible. An aim of theory is to describe solutions of the deterministic equations that are likely to be reached starting from typical initial conditions and to persist at long times. A unified description is developed, based on the linear instabilities of a homogeneous state, which leads naturally to a classification of patterns in terms of the characteristic wave vector q0 and frequency ω0 of the instability. Type Is systems (ω0=0, q0≠0) are stationary in time and periodic in space; type IIIo systems (ω0≠0, q0=0) are periodic in time and uniform in space; and type Io systems (ω0≠0, q0≠0) are periodic in both space and time. Near a continuous (or supercritical) instability, the dynamics may be accurately described via "amplitude equations," whose form is universal for each type of instability. The specifics of each system enter only through the nonuniversal coefficients. Far from the instability threshold a different universal description known as the "phase equation" may be derived, but it is restricted to slow distortions of an ideal pattern. For many systems appropriate starting equations are either not known or too complicated to analyze conveniently. It is thus useful to introduce phenomenological order-parameter models, which lead to the correct amplitude equations near threshold, and which may be solved analytically or numerically in the nonlinear regime away from the instability. The above theoretical methods are useful in analyzing "real pattern effects" such as the influence of external boundaries, or the formation and dynamics of defects in ideal structures. An important element in nonequilibrium systems is the appearance of deterministic chaos. A greal deal is known about systems with a small number of degrees of freedom displaying "temporal chaos," where the structure of the phase space can be analyzed in detail. For spatially extended systems with many degrees of freedom, on the other hand, one is dealing with spatiotemporal chaos and appropriate methods of analysis need to be developed. In addition to the general features of nonequilibrium pattern formation discussed above, detailed reviews of theoretical and experimental work on many specific systems are presented. These include Rayleigh-Benard convection in a pure fluid, convection in binary-fluid mixtures, electrohydrodynamic convection in nematic liquid crystals, Taylor-Couette flow between rotating cylinders, parametric surface waves, patterns in certain open flow systems, oscillatory chemical reactions, static and dynamic patterns in biological media, crystallization fronts, and patterns in nonlinear optics. A concluding section summarizes what has and has not been accomplished, and attempts to assess the prospects for the future.
6,145 citations
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TL;DR: An overview about the selection of the ingredients, different ways of SLN production and SLN applications, and the in vivo fate of the carrier are presented.
2,786 citations
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TL;DR: These techniques are described and illustrated with examples highlighting current capabilities and limitations of single-molecule force spectroscopy.
Abstract: Single-molecule force spectroscopy has emerged as a powerful tool to investigate the forces and motions associated with biological molecules and enzymatic activity. The most common force spectroscopy techniques are optical tweezers, magnetic tweezers and atomic force microscopy. Here we describe these techniques and illustrate them with examples highlighting current capabilities and limitations.
2,155 citations
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01 Oct 1948
TL;DR: In this article, it was shown that a metal should be superconductive if a set of corners of a Brillouin zone is lying very near the Fermi surface, considered as a sphere, which limits the region in the momentum space completely filled with electrons.
Abstract: IN two previous notes1, Prof. Max Born and I have shown that one can obtain a theory of superconductivity by taking account of the fact that the interaction of the electrons with the ionic lattice is appreciable only near the boundaries of Brillouin zones, and particularly strong near the corners of these. This leads to the criterion that the metal should be superconductive if a set of corners of a Brillouin zone is lying very near the Fermi surface, considered as a sphere, which limits the region in the momentum space completely filled with electrons.
2,042 citations
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TL;DR: In this article, a review of recent developments in the hydro- dynamic stability theory of spatially developing flows pertaining to absolute/convective and local/global instability concepts is presented.
Abstract: The goal of this survey is to review recent developments in the hydro dynamic stability theory of spatially developing flows pertaining to absolute/convective and local/global instability concepts. We wish to dem onstrate how these notions can be used effectively to obtain a qualitative and quantitative description of the spatio-temporal dynamics of open shear flows, such as mixing layers, jets, wakes, boundary layers, plane Poiseuille flow, etc. In this review, we only consider open flows where fluid particles do not remain within the physical domain of interest but are advected through downstream flow boundaries. Thus, for the most part, flows in "boxes" (Rayleigh-Benard convection in finite-size cells, Taylor-Couette flow between concentric rotating cylinders, etc.) are not discussed. Further more, the implications of local/global and absolute/convective instability concepts for geophysical flows are only alluded to briefly. In many of the flows of interest here, the mean-velocity profile is non-
1,988 citations