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Julia Faurie, Mathilde Baudet, Kondo Claude Assi, Dominique Auger, Guillaume Gilbert, Francois Tournoux, Damien Garcia
Recent studies have suggested that intracardiac vortex flow imaging could be of clinical interest to early diagnose the diastolic heart function. Doppler vortography has been intro-duced as a simple color Doppler method to detect and quantify intraventricular vortices. This method is able to locate a vortex core based on the recognition of an antisymmetric pattern in the Doppler velocity field. Because the heart is a fast-moving organ, high frame rates are needed to decipher the whole blood vortex dynamics during diastole...
November 29, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Guanhai Li, Brendan P Clarke, Jin-Kyu So, Kevin F MacDonald, Nikolay I Zheludev
Recent advances in the physics and technology of light generation via free-electron proximity and impact interactions with nanostructures (gratings, photonic crystals, nano-undulators, metamaterials and antenna arrays) have enabled the development of nanoscale-resolution techniques for such applications as mapping plasmons, studying nanoparticle structural transformations and characterizing luminescent materials (including time-resolved measurements). Here, we introduce a universal approach allowing generation of light with prescribed wavelength, direction, divergence and topological charge via point-excitation of holographic plasmonic metasurfaces...
December 2, 2016: Nature Communications
Zichao Li, Hong Li, Cui Tu, Jintong Hu, Wei You, Bing Luo, Mingsheng Tan, Yolbarsop Adil, Yanqi Wu, Biao Shen, Bingjia Xiao, Ping Zhang, Wenzhe Mao, Hai Wang, Xiaohui Wen, Haiyang Zhou, Jinlin Xie, Tao Lan, Adi Liu, Weixing Ding, Chijin Xiao, Wandong Liu
In a reversed field pinch device, the conductive shell is placed as close as possible to the plasma so as to balance the plasma during discharge. Plasma instabilities such as the resistive wall mode and certain tearing modes, which restrain the plasma high parameter operation, respond closely with conditions in the wall, in essence the eddy current present. Also, the effect of eddy currents induced by the external coils cannot be ignored when active control is applied to control instabilities. One diagnostic tool, an eddy current probe array, detects the eddy current in the composite shell...
November 2016: Review of Scientific Instruments
C K Taylor, Stefan G Llewellyn Smith
The surface quasi-geostrophic (SQG) equations are a model for low-Rossby number geophysical flows in which the dynamics are governed by potential temperature dynamics on the boundary. We examine point vortex solutions to this model as well as the chaotic flows induced by three point vortices. The chaotic transport induced by these flows is investigated using techniques of Poincaré maps and the Finite Time Braiding Exponent (FTBE). This chaotic transport is representative of the mixing in the flow, and these terms are used interchangeably in this work...
November 2016: Chaos
Eugene A Ryzhov, Konstantin V Koshel
The paper deals with a dynamical system governing the motion of two point vortices embedded in the bottom layer of a two-layer rotating flow experiencing linear deformation and their influence on fluid particle advection. The linear deformation consists of shear and rotational components. If the deformation is stationary, the vortices can move periodically in a bounded region. The vortex periodic motion induces stirring patterns of passive fluid particles in the both layers. We focus our attention on the upper layer where the bottom-layer singular point vortices induce a regular velocity field with no singularities...
November 2016: Chaos
Maxime Theillard, Roberto Alonso-Matilla, David Saintillan
Recent experimental studies have shown that confinement can profoundly affect self-organization in semi-dilute active suspensions, leading to striking features such as the formation of steady and spontaneous vortices in circular domains and the emergence of unidirectional pumping motions in periodic racetrack geometries. Motivated by these findings, we analyze the two-dimensional dynamics in confined suspensions of active self-propelled swimmers using a mean-field kinetic theory where conservation equations for the particle configurations are coupled to the forced Navier-Stokes equations for the self-generated fluid flow...
December 1, 2016: Soft Matter
Rui-Pin Chen, Khian-Hooi Chew, Guoquan Zhou, Chao-Qing Dai, Sailing He
The collapse dynamics of a structured optical field with a distribution of spatially-variant states of polarization (SoP) and a spiral phase in the field cross section is studied using the two-dimensional coupled nonlinear Schrӧdinger equations. The self-focusing of a structured optical field with an inhomogeneous SoP distribution can give rise to new phenomena of collapse dynamics that is completely different from a scalar field. The collapse patterns are closely related to the topological charges of the vortexas well as the polarization, the initial power, and the SoP distribution in the field cross section...
November 28, 2016: Optics Express
Minglin Yang, Yueqian Wu, Kuan Fang Ren, Xinqing Sheng
Due to special characteristics of nondiffraction and self reconstruction, the Bessel beams have attracted wide attention in optical trapping and appear to be a dramatic alternative to Gaussian beams. We present in this paper an efficient approach based on the surface integral equations (SIE) to compute the radiation pressure force (RPF) exerted on arbitrary shaped homogeneous particles by high-order Bessel vortex beam (HOBVB). The incident beam is described by vector expressions perfectly satisfy Maxwell's equations...
November 28, 2016: Optics Express
He-Xiu Xu, Guang-Ming Wang, Tong Cai, Jun Xiao, Ya-Qiang Zhuang
Pancharatnam-Berry (PB) metasurfaces have intrigued a great deal of interest in recent years for anomalous reflection/refraction, vortex plate, orbital angular momentum, flat lens, photonic spin hall effect (PSHE), holograms and reflect/transmit arrays. However, almost all designs are restricted to fixed electrical performance/functionality once the design is finished. Here, we report for the first time a strategy for PB metasurface with agile working frequency by involving each meta-atom with tunable PIN diodes...
November 28, 2016: Optics Express
Priyanka Lochab, P Senthilkumaran, Kedar Khare
We study the propagation of a charge-1 vortex beam using the angular spectrum method. While vortex beams are commonly assumed to have a helical wavefront, it is well known that the phase of the vortex in the near-core region varies arbitrarily quickly. In order to explain the wavefront behavior in the near-core region, ideas such as evanescent fields or superoscillatory functions have been used before. Our study using the angular spectrum method can inherently take into account the propagating as well as evanescent spatial frequencies and is able to provide the detailed wavefront structure as the vortex wavefront evolves...
December 1, 2016: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Victor V Kotlyar, Alexey A Kovalev, Alexey P Porfirev
We derived exact analytical relationships to describe the complex amplitude of a perfect optical vortex generated by means of three different optical elements, namely, (i) an amplitude-phase element with a transmission function proportional to a Bessel function, (ii) an optimal phase element with a transmission equal to the sign function of a Bessel function, and (iii) a spiral axicon. The doughnut intensity was shown to be highest when using an optimal phase element. The spiral-axicon-aided diffraction ring was found to be twice as wide as when generated using two other elements...
December 1, 2016: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
He-Xiu Xu, Shiwei Tang, Shaojie Ma, Weijie Luo, Tong Cai, Shulin Sun, Qiong He, Lei Zhou
Controlling the phase distributions on metasurfaces leads to fascinating effects such as anomalous light refraction/reflection, flat-lens focusing, and optics-vortex generation. However, metasurfaces realized so far largely reply on passive resonant meta-atoms, whose intrinsic dispersions limit such passive meta-devices' performances at frequencies other than the target one. Here, based on tunable meta-atoms with varactor diodes involved, we establish a scheme to resolve these issues for microwave metasurfaces, in which the dispersive response of each meta-atom is precisely controlled by an external voltage imparted on the diode...
November 30, 2016: Scientific Reports
Richard J Lozowy, David C S Kuhn, Annie A Ducas, April J Boyd
Direct numerical simulations were performed on four patient-specific abdominal aortic aneurysm (AAA) geometries and the resulting pulsatile blood flow dynamics were compared to aneurysm shape and correlated with intraluminal thrombus (ILT) deposition. For three of the cases, turbulent vortex structures impinged/sheared along the anterior wall and along the posterior wall a zone of recirculating blood formed. Within the impingement region the AAA wall was devoid of ILT and remote to this region there was an accumulation of ILT...
November 28, 2016: Cardiovascular Engineering and Technology
Zhaoli Wang, Jun Li, Chengguang Lai, Zhaoyang Zeng, Ruida Zhong, Xiaohong Chen, Xiaowen Zhou, Mingyuan Wang
In recent decades, the occurrence and severity of drought in China has had devastating impact on social and economic development. The increase in drought has been attributed to global warming. We used the high-accuracy self-calibrating Palmer Drought Severity Index (scPDSI) to investigate the variation in drought in China between 1961 and 2009 using the Mann-Kendall (MK), continuous wavelet transform (CWT) and the rotated empirical orthogonal function (REOF) methods. We also analyzed the relationship between the rotated principal component time series (RPCs) and 74 circulation indices...
November 25, 2016: Science of the Total Environment
Charlotte L Marous, Kareem Sioufi, Carol L Shields, Arman Mashayekhi, Jerry A Shields
PURPOSE: To describe two cases of coughing-induced suprachoroidal hemorrhage referred as choroidal melanoma. METHODS: Observational case reports. RESULTS: Two female patients (ages 54 and 60 years) were referred with possible choroidal melanoma. Both gave a history of 1 day of heavy coughing with Valsalva maneuver within 2 weeks before discovery of the tumor. In one case, the patient used anticoagulants for aortic valve replacement and the other patient used antiasthma medications...
November 23, 2016: Retinal Cases & Brief Reports
Kevin Sunderland, Christopher Haferman, Gouthami Chintalapani, Jingfeng Jiang
This study aims to develop an alternative vortex analysis method by measuring structure ofIntracranial aneurysm (IA) flow vortexes across the cardiac cycle, to quantify temporal stability of aneurismal flow. Hemodynamics were modeled in "patient-specific" geometries, using computational fluid dynamics (CFD) simulations. Modified versions of known λ2 and Q-criterion methods identified vortex regions; then regions were segmented out using the classical marching cube algorithm. Temporal stability was measured by the degree of vortex overlap (DVO) at each step of a cardiac cycle against a cycle-averaged vortex and by the change in number of cores over the cycle...
2016: Computational and Mathematical Methods in Medicine
Michael B Raizman, Pedram Hamrah, Edward J Holland, Terry Kim, Francis S Mah, Christopher J Rapuano, Roger G Ulrich
Drugs across many pharmacologic classes induce corneal epithelial changes. Many of these drugs have cationic amphiphilic structures, with a hydrophobic ring and hydrophilic cationic amine side chain that allow them to cross cell membranes. These drugs lead to intracellular phospholipid accumulation, often manifested in the cornea by vortex keratopathy, with no effect on visual acuity and few ocular symptoms. Other drugs, notably antineoplastic agents, produce a fine diffuse corneal haze, sometimes accompanied by decreased vision that can be dose limiting...
November 24, 2016: Survey of Ophthalmology
Mingxin Li, Qian Wang, Jing Zhu, Nana Li, Xiaoli Zou
The glucuronide conjugate of 1-hydroxypyrene (1-OHP-G) is a sensitive and reliable index biomarker for assessing low exposure to polycyclic aromatic hydrocarbons (PAHs). A simple method for determining 1-OHP-G in human urine with ultra performance liquid chromatography-tandem mass spectrometry (UPLC-MS/MS) was established and applied to evaluate the exposure level of PAHs of pregnant women in a large sample size. After the urine sample was extracted with ethyl acetate, 0.2 mL of the aqueous phase was diluted to 1...
November 25, 2016: Analytical and Bioanalytical Chemistry
F Candelier, J Einarsson, B Mehlig
We compute the angular dynamics of a neutrally buoyant nearly spherical particle immersed in an unsteady fluid. We assume that the particle is small, that its translational slip velocity is negligible, and that unsteady and convective inertia are small perturbations. We derive an approximation for the torque on the particle that determines the first inertial corrections to Jeffery's equation. These corrections arise as a consequence of local vortex stretching and can be substantial in turbulence, where local vortex stretching is strong and closely linked to the irreversibility of turbulence...
November 11, 2016: Physical Review Letters
D B Gopman, Y P Kabanov, J Cui, C S Lynch, R D Shull
We report the magnetization reversal behavior of microstructured Ni80Fe20 rings using magneto-optic indicator film imaging and magnetometry. While the reversal behavior of rings with a symmetric (circular) interior hole agrees with micromagnetic simulations of an onion → vortex → onion transition, we experimentally demonstrate that rings possessing an elliptical hole with an aspect ratio of 2 exhibit complex reversal behavior comprising incoherent domain propagation in the rings. Magneto optic images reveal metastable magnetic configurations that illustrate this incoherent behavior...
2016: Applied Physics Letters
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