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Rotating polygon instability of a swirling free surface flow. PHYSICAL REVIEW LETTERS 2013; 110:194502. [PMID: 23705710 DOI: 10.1103/physrevlett.110.194502] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 09/25/2012] [Indexed: 06/02/2023]
Abstract
We explain the rotating polygon instability on a swirling fluid surface [G. H. Vatistas, J. Fluid Mech. 217, 241 (1990) and Jansson et al., Phys. Rev. Lett. 96, 174502 (2006)] in terms of resonant interactions between gravity waves on the outer part of the surface and centrifugal waves on the inner part. Our model is based on potential flow theory, linearized around a potential vortex flow with a free surface for which we show that unstable resonant states appear. Limiting our attention to the lowest order mode of each type of wave and their interaction, we obtain an analytically soluble model, which, together with estimates of the circulation based on angular momentum balance, reproduces the main features of the experimental phase diagram. The generality of our arguments implies that the instability should not be limited to flows with a rotating bottom (implying singular behavior near the corners), and indeed we show that we can obtain the polygons transiently by violently stirring liquid nitrogen in a hot container.
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THEORETICAL AND EXPERIMENTAL DETERMINATION OF PHLOEM TRANSLOCATION SPEEDS IN GYMNOSPERM AND ANGIOSPERM TREES. ACTA ACUST UNITED AC 2013. [DOI: 10.17660/actahortic.2013.991.5] [Citation(s) in RCA: 8] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/17/2022]
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3
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Optimality of the Münch mechanism for translocation of sugars in plants. J R Soc Interface 2011; 8:1155-65. [PMID: 21245117 PMCID: PMC3119876 DOI: 10.1098/rsif.2010.0578] [Citation(s) in RCA: 72] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/20/2010] [Accepted: 12/21/2010] [Indexed: 11/12/2022] Open
Abstract
Plants require effective vascular systems for the transport of water and dissolved molecules between distal regions. Their survival depends on the ability to transport sugars from the leaves where they are produced to sites of active growth; a flow driven, according to the Münch hypothesis, by osmotic gradients generated by differences in sugar concentration. The length scales over which sugars are produced (Lleaf) and over which they are transported (L(stem)), as well as the radius r of the cylindrical phloem cells through which the transport takes place, vary among species over several orders of magnitude; a major unsettled question is whether the Münch transport mechanism is effective over this wide range of sizes. Optimization of translocation speed predicts a scaling relation between radius r and the characteristic lengths as r∼(Lleaf Lstem)1/3. Direct measurements using novel in vivo techniques and biomimicking microfluidic devices support this scaling relation and provide the first quantitative support for a unified mechanism of sugar translocation in plants spanning several orders of magnitude in size. The existence of a general scaling law for phloem dimensions provides a new framework for investigating the physical principles governing the morphological diversity of plants.
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Pattern formation of underwater sand ripples with a skewed drive. PHYSICAL REVIEW. E, STATISTICAL, NONLINEAR, AND SOFT MATTER PHYSICS 2004; 70:066207. [PMID: 15697484 DOI: 10.1103/physreve.70.066207] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 02/24/2004] [Indexed: 05/24/2023]
Abstract
In this paper we present an experimental study of the dynamics of underwater sand ripples when a regular pattern of ripples is subjected to a skewed oscillatory flow, i.e., one not perpendicular to the direction of the ripple crests. Striking patterns with new, superposed ripples on top of the original ones occur very quickly with a characteristic angle, which is, in general, not perpendicular to the flow. A slower, more complex transition then follows, leading to the final state where the ripples are again perpendicular to the flow. We investigate the variation of the superposed pattern as a function of the direction, amplitude, and frequency of the drive, and as a function of the viscosity (by changing the temperature). We quantify the dynamics of the entire transition process and finally study the grain motion around idealized (solid) skewed ripples. This leads to a characteristic mean path of a single particle. The path has a shape close to a parallelogram, with no apparent connection to the pattern of real, superposed ripples. On the other hand, a thin layer of sand sprinkled on the solid ripples leads to qualitatively similar patterns.
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Abstract
We present experiments and theory for the "bathtub vortex," which forms when a fluid drains out of a rotating cylindrical container through a small drain hole. The fast down-flow is found to be confined to a narrow and rapidly rotating "drainpipe" from the free surface down to the drain hole. Surrounding this drainpipe is a region with slow upward flow generated by the Ekman layer at the bottom of the container. This flow structure leads us to a theoretical model similar to one obtained earlier by Lundgren [J. Fluid Mech. 155, 381 (1985)]], but here including surface tension and Ekman upwelling, comparing favorably with our measurements. At the tip of the needlelike surface depression, we observe a bubble-forming instability at high rotation rates.
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Stability balloon for two-dimensional vortex ripple patterns. PHYSICAL REVIEW LETTERS 2001; 87:204301. [PMID: 11690476 DOI: 10.1103/physrevlett.87.204301] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/22/2001] [Indexed: 05/23/2023]
Abstract
Patterns of vortex ripples form when a sand bed is subjected to an oscillatory fluid flow. Here we describe experiments on the response of regular vortex ripple patterns to sudden changes of the driving amplitude a or frequency f. A sufficient decrease of f leads to a "freezing" of the pattern, while a sufficient increase of f leads to a supercritical secondary "pearling" instability. Sufficient changes in the amplitude a lead to subcritical secondary "doubling" and "bulging" instabilities. Our findings are summarized in a "stability balloon" for vortex ripple pattern formation.
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Breakdown of universality in transitions to spatiotemporal chaos. PHYSICAL REVIEW LETTERS 2001; 86:5482-5485. [PMID: 11415281 DOI: 10.1103/physrevlett.86.5482] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/17/2000] [Indexed: 05/23/2023]
Abstract
We show that the transition from laminar to active behavior in extended chaotic systems can vary from a continuous transition in the universality class of directed percolation with infinitely many absorbing states to what appears as a first-order transition. The latter occurs when finite lifetime nonchaotic structures, called "solitons," dominate the dynamics. We illustrate this scenario in an extension of the deterministic Chaté-Manneville coupled map lattice model and in a soliton including variant of the stochastic Domany-Kinzel cellular automaton.
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Derivation of Green function for disordered chain by integrating over commuting and anticommuting variables. ACTA ACUST UNITED AC 2000. [DOI: 10.1088/0022-3719/15/9/004] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022]
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Sociosomatics and illness in CFS. Psychosom Med 1999; 61:256. [PMID: 10204981 DOI: 10.1097/00006842-199903000-00021] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 11/27/2022]
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Comment on "Stability of a Solitary Pulse against Wave Packet Disturbances in an Active Medium". PHYSICAL REVIEW LETTERS 1996; 77:5441. [PMID: 10062804 DOI: 10.1103/physrevlett.77.5441] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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A long-term follow-up on "post-traumatic fibromyalgia" patients. Am J Phys Med Rehabil 1995; 74:476-7. [PMID: 8534397] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/31/2023]
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Abstract
We give analytic arguments and numerical evidence to show that the presence of conservation laws can produce a singularity in the spectrum of Lyapunov exponents for extended dynamical systems of low spatial dimensionality. This phenomenon can be used, e.g., for finding hidden conservation laws. (c) 1995 American Institute of Physics.
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Growth shapes and turbulent spots in unstable systems. PHYSICAL REVIEW. E, STATISTICAL PHYSICS, PLASMAS, FLUIDS, AND RELATED INTERDISCIPLINARY TOPICS 1995; 51:4485-4502. [PMID: 9963162 DOI: 10.1103/physreve.51.4485] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Death certificates: an efficient source for ascertainment of Creutzfeldt-Jakob disease cases. Neuroepidemiology 1995; 14:1-6. [PMID: 7898601 DOI: 10.1159/000109771] [Citation(s) in RCA: 16] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
Abstract
Case ascertainment for an epidemiologic study of Creutzfeldt-Jakob disease (CJD) can be difficult. This report investigates the efficiency of various sources of case ascertainment for CJD. Cases were identified utilizing neuropathologists, hospitals and death certificates from 11 targeted states. For the period of 1986-1988, 247 death certificates indicating a diagnosis of CJD were obtained. Only 26 potential cases were identified without death certificates. The proportion of neuropathologically confirmed cases identified by death certificates only, i.e., which were not identified through any other source, was 42%. Furthermore, 80% of all the neuropathologically confirmed cases were ascertained utilizing death certificates as a source. Of the remaining 20%, 7% were ascertained through neuropathologists only, 10% through hospitals only, 1.5% through a combination of hospitals and neuropathologists, and 1.5% through another source. The false-positive rate for death certificates with neuropathology (which may have been performed after the death certificate was filled out) was estimated to be 8.3%. The results indicate that death certificates were by far the most efficient source for initial ascertainment of potential CJD cases to be followed by verification of diagnosis.
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Megadose steroids in multiple sclerosis. Neurology 1994; 44:1988. [PMID: 7936272 DOI: 10.1212/wnl.44.10.1988] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/27/2023] Open
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Anomalous diffusion in the Kuramoto-Sivashinsky equation. PHYSICAL REVIEW LETTERS 1993; 70:2892-2895. [PMID: 10053680 DOI: 10.1103/physrevlett.70.2892] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Dynamic scaling and crossover analysis for the Kuramoto-Sivashinsky equation. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1992; 46:R7351-R7354. [PMID: 9908164 DOI: 10.1103/physreva.46.r7351] [Citation(s) in RCA: 55] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Nucleation and transients at the onset of vortex turbulence. PHYSICAL REVIEW LETTERS 1992; 69:2380-2383. [PMID: 10046470 DOI: 10.1103/physrevlett.69.2380] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Chaotic interface dynamics: A model with turbulent behavior. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1992; 46:4791-4796. [PMID: 9908698 DOI: 10.1103/physreva.46.4791] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Recalled to Life: The Story of a Coma. Neurology 1991. [DOI: 10.1212/wnl.41.8.1330-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Cost of neurologic care. Neurology 1991. [DOI: 10.1212/wnl.41.1.158-a] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/15/2022] Open
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Transition to turbulence in a discrete Ginzburg-Landau model. PHYSICAL REVIEW. A, ATOMIC, MOLECULAR, AND OPTICAL PHYSICS 1990; 42:3626-3629. [PMID: 9904448 DOI: 10.1103/physreva.42.3626] [Citation(s) in RCA: 7] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Carpal tunnel syndrome. Mayo Clin Proc 1990; 65:122-4. [PMID: 2296207 DOI: 10.1016/s0025-6196(12)62118-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
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Warfarin and stroke. West J Med 1989; 151:669. [PMID: 2694623 PMCID: PMC1026771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/02/2023]
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Size dependence, coherence, and scaling in turbulent coupled-map lattices. PHYSICAL REVIEW LETTERS 1989; 63:2161-2164. [PMID: 10040816 DOI: 10.1103/physrevlett.63.2161] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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Order parameter, symmetry breaking, and phase transitions in the description of multifractal sets. PHYSICAL REVIEW. A, GENERAL PHYSICS 1987; 36:4904-4915. [PMID: 9898749 DOI: 10.1103/physreva.36.4904] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/22/2023]
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Coherence, chaos, and broken symmetry in classical, many-body dynamical systems. PHYSICAL REVIEW LETTERS 1987; 58:2155-2158. [PMID: 10034666 DOI: 10.1103/physrevlett.58.2155] [Citation(s) in RCA: 21] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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And it wasn't her fault anyway .. JAMA 1986; 255:467. [PMID: 3941529] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [MESH Headings] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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Destruction of invariant tori as an eigenvalue problem. PHYSICAL REVIEW LETTERS 1985; 54:1737-1741. [PMID: 10031127 DOI: 10.1103/physrevlett.54.1737] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/23/2023]
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