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Aditya R Nayak, Malcolm N McFarland, James M Sullivan, Michael S Twardowski
In situ measurements were undertaken to characterize particle fields in undisturbed oceanic environments. Simultaneous, co-located depth profiles of particle fields and flow characteristics were recorded using a submersible holographic imaging system and an acoustic Doppler velocimeter, under different flow conditions and varying particle concentration loads, typical of those found in coastal oceans and lakes. Nearly one million particles with major axis lengths ranging from ∼14 μm to 11.6 mm, representing diverse shapes, sizes, and aspect ratios were characterized as part of this study...
January 2018: Limnology and Oceanography
M Guélin, N A Patel, M Bremer, J Cernicharo, A Castro-Carrizo, J Pety, J P Fonfría, M Agúndez, M Santander-García, G Quintana-Lacaci, L Velilla Prieto, R Blundell, P Thaddeus
During their late pulsating phase, AGB stars expel most of their mass in the form of massive dusty envelopes, an event that largely controls the composition of interstellar matter. The envelopes, however, are distant and opaque to visible and NIR radiation: their structure remains poorly known and the mass-loss process poorly understood. Millimeter-wave interferometry, which combines the advantages of longer wavelength, high angular resolution and very high spectral resolution is the optimal investigative tool for this purpose...
February 2018: Astronomy and Astrophysics
Romain Capoulade, Jonathan G Teoh, Philipp E Bartko, Eliza Teo, Jan-Erik Scholtz, Lionel Tastet, Mylene Shen, Christos G Mihos, Yong H Park, Julio Garcia, Eric Larose, Eric M Isselbacher, Thoralf M Sundt, Thomas E MacGillivray, Serguei Melnitchouk, Brian B Ghoshhajra, Philippe Pibarot, Judy Hung
BACKGROUND: The aim of this study was to examine the association between abnormal morphology of the proximal aorta and aortic stenosis (AS) progression rate. The main hypothesis was that morphologic changes of the proximal aorta, such as effacement of the sinotubular junction (STJ), result in increased biomechanical stresses and contribute to calcification and progression of AS. METHODS: Between 2010 and 2012, 426 patients with mild to moderate AS were included in this study...
February 16, 2018: Journal of the American Society of Echocardiography
Maha Krayem, Véronique Deluchat, Philippe Hourdin, Patrice Fondanèche, Florence Lecavelier Des Etangs, Véronique Kazpard, Christian Moesch, Pascal Labrousse
The aim of this study is to determine the combined effect of copper and hydrodynamic conditions on the response of certain biomarkers of an aquatic macrophyte, namely Myriophyllum alterniflorum. Watermilfoil biomarkers are monitored in a synthetic medium enriched or not with copper (100 μg.L -1 ) for 21 days in aquarium systems (150 L), under three hydrodynamic conditions: laminar, turbulent, and calm. The studied biomarkers are: respiratory and photosynthetic activities; concentrations of chlorophyll a, b and carotenoids; osmotic potential; hydrogen peroxide content; and growth...
February 9, 2018: Chemosphere
Timothy T Clark, Susan Kurien, Robert Rubinstein
A computational tool for the anisotropic time-evolution of the spectral velocity correlation tensor is presented. We operate in the linear, rapid distortion limit of the mean-field-coupled equations. Each term of the equations is written in the form of an expansion to arbitrary order in the basis of irreducible representations of the SO(3) symmetry group. The computational algorithm for this calculation solves a system of coupled equations for the scalar weights of each generated anisotropic mode. The analysis demonstrates that rapid distortion rapidly but systematically generates higher-order anisotropic modes...
January 2018: Physical Review. E
N Andrés, S Galtier, F Sahraoui
We derive an exact law for three-dimensional (3D) homogeneous compressible isothermal Hall magnetohydrodynamic turbulence, without the assumption of isotropy. The Hall current is shown to introduce new flux and source terms that act at the small scales (comparable or smaller than the ion skin depth) to significantly impact the turbulence dynamics. The law provides an accurate means to estimate the energy cascade rate over a broad range of scales covering the magnetohydrodynamic inertial range and the sub-ion dispersive range in 3D numerical simulations and in in situ spacecraft observations of compressible turbulence...
January 2018: Physical Review. E
Brandon E Morgan, Oleg Schilling, Tucker A Hartland
The three-equation k-L-a turbulence model [B. Morgan and M. Wickett, Three-equation model for the self-similar growth of Rayleigh-Taylor and Richtmyer-Meshkov instabilities, Phys. Rev. E 91, 043002 (2015)PLEEE81539-375510.1103/PhysRevE.91.043002] is extended by the addition of a second length scale equation. It is shown that the separation of turbulence transport and turbulence destruction length scales is necessary for simultaneous prediction of the growth parameter and turbulence intensity of a Kelvin-Helmholtz shear layer when model coefficients are constrained by similarity analysis...
January 2018: Physical Review. E
E Kroupp, E Stambulchik, A Starobinets, D Osin, V I Fisher, D Alumot, Y Maron, S Davidovits, N J Fisch, A Fruchtman
The ion kinetic energy in a stagnating plasma was previously determined by Kroupp et al. [Phys. Rev. Lett. 107, 105001 (2011)PRLTAO0031-900710.1103/PhysRevLett.107.105001] from Doppler-dominated line shapes augmented by measurements of plasma properties and assuming a uniform-plasma model. Notably, the energy was found to be dominantly stored in hydrodynamic flow. Here we advance a new description of this stagnation as supersonically turbulent. Such turbulence implies a nonuniform density distribution. We demonstrate how to reanalyze the spectroscopic data consistent with the turbulent picture and show that this leads to better concordance of the overconstrained spectroscopic measurements, while also substantially lowering the inferred mean density...
January 2018: Physical Review. E
Keegan J Moore, Jonathan Bunyan, Sameh Tawfick, Oleg V Gendelman, Shuangbao Li, Michael Leamy, Alexander F Vakakis
In linear time-invariant dynamical and acoustical systems, reciprocity holds by the Onsager-Casimir principle of microscopic reversibility, and this can be broken only by odd external biases, nonlinearities, or time-dependent properties. A concept is proposed in this work for breaking dynamic reciprocity based on irreversible nonlinear energy transfers from large to small scales in a system with nonlinear hierarchical internal structure, asymmetry, and intentional strong stiffness nonlinearity. The resulting nonreciprocal large-to-small scale energy transfers mimic analogous nonlinear energy transfer cascades that occur in nature (e...
January 2018: Physical Review. E
Carlos Granero-Belinchón, Stéphane G Roux, Nicolas B Garnier
For generic systems exhibiting power law behaviors, and hence multiscale dependencies, we propose a simple tool to analyze multifractality and intermittency, after noticing that these concepts are directly related to the deformation of a probability density function from Gaussian at large scales to non-Gaussian at smaller scales. Our framework is based on information theory and uses Shannon entropy and Kullback-Leibler divergence. We provide an extensive application to three-dimensional fully developed turbulence, seen here as a paradigmatic complex system where intermittency was historically defined and the concepts of scale invariance and multifractality were extensively studied and benchmarked...
January 2018: Physical Review. E
Michael M Norton, Arvind Baskaran, Achini Opathalage, Blake Langeslay, Seth Fraden, Aparna Baskaran, Michael F Hagan
Confining a liquid crystal imposes topological constraints on the orientational order, allowing global control of equilibrium systems by manipulation of anchoring boundary conditions. In this article, we investigate whether a similar strategy allows control of active liquid crystals. We study a hydrodynamic model of an extensile active nematic confined in containers, with different anchoring conditions that impose different net topological charges on the nematic director. We show that the dynamics are controlled by a complex interplay between topological defects in the director and their induced vortical flows...
January 2018: Physical Review. E
Martyna Woltanowska, Piotr Woltanowski, Andrzej Wincewicz, Magdalena Woltanowska
Aim: Our purpose was to write a biography of Stanisław Ostrowski that would address in the first place the medical aspect of his professional life, with a comprehensive approach of others fields of his activity. Methods: We essentially grounded the paper on primary resources that were papers authored by Ostrowski including his scientific publications, memories, speeches as well as contemporaneous official documents that referred to Ostrowski. Second resources were also used to double check some data from primary resources and to place the biography of Stanisław Ostrowski in a proper background with special care to social, professional and political context...
2018: Clujul Medical (1957)
T Kobayashi, M Sasaki, T Ido, K Kamiya, Y Miura, Y Nagashima, K Ida, S Inagaki, A Fujisawa, S-I Itoh, K Itoh
We investigate spatial structures of turbulence and turbulent transport modulated by the geodesic acoustic mode (GAM), from which the excitation mechanism of the GAM is discussed. The GAM is found to be predominantly excited through a localized Reynolds stress force, rather than the dynamic shearing force. The evaluated growth rate is larger than the linear damping coefficients and is on the same order of magnitude as the effective growth rate evaluated from time evolution in the GAM kinetic energy.
January 26, 2018: Physical Review Letters
Hechuan Jiang, Xiaojue Zhu, Varghese Mathai, Roberto Verzicco, Detlef Lohse, Chao Sun
In this combined experimental and numerical study on thermally driven turbulence in a rectangular cell, the global heat transport and the coherent flow structures are controlled with an asymmetric ratchetlike roughness on the top and bottom plates. We show that, by means of symmetry breaking due to the presence of the ratchet structures on the conducting plates, the orientation of the large scale circulation roll (LSCR) can be locked to a preferred direction even when the cell is perfectly leveled out. By introducing a small tilt to the system, we show that the LSCR orientation can be tuned and controlled...
January 26, 2018: Physical Review Letters
Martin James, Michael Wilczek
Cellular suspensions such as dense bacterial flows exhibit a turbulence-like phase under certain conditions. We study this phenomenon of "active turbulence" statistically by using numerical tools. Following Wensink et al. (Proc. Natl. Acad. Sci. U.S.A. 109, 14308 (2012)), we model active turbulence by means of a generalized Navier-Stokes equation. Two-point velocity statistics of active turbulence, both in the Eulerian and the Lagrangian frame, is explored. We characterize the scale-dependent features of two-point statistics in this system...
February 14, 2018: European Physical Journal. E, Soft Matter
Rich Pang, Floris van Breugel, Michael Dickinson, Jeffrey A Riffell, Adrienne Fairhall
Natural decision-making often involves extended decision sequences in response to variable stimuli with complex structure. As an example, many animals follow odor plumes to locate food sources or mates, but turbulence breaks up the advected odor signal into intermittent filaments and puffs. This scenario provides an opportunity to ask how animals use sparse, instantaneous, and stochastic signal encounters to generate goal-oriented behavioral sequences. Here we examined the trajectories of flying fruit flies (Drosophila melanogaster) and mosquitoes (Aedes aegypti) navigating in controlled plumes of attractive odorants...
February 12, 2018: PLoS Computational Biology
Natércia Matias, Rita Matos, Filipa Ferreira, Jes Vollertsen, José Saldanha Matos
For engineering purposes it is especially useful to be able to predict and control sewer corrosion rates and odor impacts as well as to design effective measures aiming to reduce effects related to hydrogen sulfide formation and release. Doing so, it is important to use modeling tools that are capable of assessing variations of dissolved oxygen, dissolved sulfide and hydrogen sulfide gas concentrations for a wide range of environmental scenarios. Two such models were assessed: AEROSEPT, an empirical formulation, and WATS, a conceptual and more complex approach...
February 2018: Water Science and Technology: a Journal of the International Association on Water Pollution Research
Nicolas Bian, A Gordon Emslie, Duncan Horne, Eduard P Kontar
Using the "enthalpy-based thermal evolution of loops" (EBTEL) model, we investigate the hydrodynamics of the plasma in a flaring coronal loop in which heat conduction is limited by turbulent scattering of the electrons that transport the thermal heat flux. The EBTEL equations are solved analytically in each of the two (conduction-dominated and radiation-dominated) cooling phases. Comparison of the results with typical observed cooling times in solar flares shows that the turbulent mean free path λT lies in a range corresponding to a regime in which classical (collision-dominated) conduction plays at most a limited role...
January 10, 2018: Astrophysical Journal
Vadim M Uritsky, Merrill A Roberts, C Richard DeVore, Judith T Karpen
Extreme-ultraviolet and X-ray jets occur frequently in magnetically open coronal holes on the Sun, especially at high solar latitudes. Some of these jets are observed by white-light coronagraphs as they propagate through the outer corona toward the inner heliosphere, and it has been proposed that they give rise to microstreams and torsional Alfvén waves detected in situ in the solar wind. To predict and understand the signatures of coronal-hole jets, we have performed a detailed statistical analysis of such a jet simulated with an adaptively refined magnetohydrodynamics model...
March 10, 2017: Astrophysical Journal
Maryam Dehbani, Masoud Rahimi
In the present study, Ultrasonic Falling Film (USFF), as a novel technique has been proposed to increase the evaporation rate of moderate temperature liquid film. It is a proper method for some applications which cannot be performed at high temperature, such as foodstuff industry, due to their sensitivity to high temperatures. Evaporation rate of sodium chloride solution from an USFF on an inclined flat plate compared to that for Falling Film without ultrasonic irradiation (FF) at various temperatures was investigated...
April 2018: Ultrasonics Sonochemistry
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