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Tahra L Eissa, Koen Dijkstra, Christoph Brune, Ronald G Emerson, Michel J A M van Putten, Robert R Goodman, Guy M McKhann, Catherine A Schevon, Wim van Drongelen, Stephan A van Gils
Small-scale neuronal networks may impose widespread effects on large network dynamics. To unravel this relationship, we analyzed eight multiscale recordings of spontaneous seizures from four patients with epilepsy. During seizures, multiunit spike activity organizes into a submillimeter-sized wavefront, and this activity correlates significantly with low-frequency rhythms from electrocorticographic recordings across a 10-cm-sized neocortical network. Notably, this correlation effect is specific to the ictal wavefront and is absent interictally or from action potential activity outside the wavefront territory...
September 18, 2017: Proceedings of the National Academy of Sciences of the United States of America
Mohammad Ghoreishi, Mohammad-Ali Abtahi, Iman Seyedzadeh, Hamid Fesharaki, Mohadeseh Mohammadnia, Hamidreza Jahanbani-Ardakani, Seyed-Hossein Abtahi
BACKGROUND: The aim of this study is to evaluate the results of photorefractive keratectomy (PRK) in the management of postoperative hyperopia and astigmatism in patients with history of radial keratotomy (RK). MATERIALS AND METHODS: This prospective nonrandomized noncomparative interventional case series enrolled consecutive eyes treated with PRK after RK. In cases, in which (1) wavefront (WF) scan was undetectable during primary examinations; and/or, (2) WF data were not transferable to the excimer laser device, patients were treated with the tissue-saving (TS) mode...
2017: Journal of Research in Medical Sciences: the Official Journal of Isfahan University of Medical Sciences
Bhupesh Pathik, Jonathan M Kalman, Tomos Walters, Pawel Kuklik, Jichao Zhao, Andrew Madry, Prashanthan Sanders, Peter M Kistler, Geoffrey Lee
BACKGROUND: Current phase mapping systems for atrial fibrillation(AF) create two-dimensional(2D) maps. This process may affect the accurate detection of rotors. We developed a three-dimensional(3D) phase mapping technique that utilizes the 3D locations of basket electrodes to project phase onto patient-specific left atrial(LA) 3D surface anatomy. OBJECTIVES: We sought to determine whether rotors detected in 2D phase maps were present at corresponding time segments and anatomical locations on 3D phase maps...
September 13, 2017: Heart Rhythm: the Official Journal of the Heart Rhythm Society
Naiting Gu, Benxi Yao, Linhai Huang, Changhui Rao
We propose a compact phase-shifting radial shearing interferometer based on a pixelated micro-retarder array (MRA). The MRA is made of a thin birefringence plate, and is composed of identical units that have pixels of four different thicknesses. We demonstrate that pixelated phase delay between two shearing beams can be introduced by applying the fast axis of birefringence plate in the horizontal or vertical orientation. We also present an approach to extract the wavefront under test with random phase shift, which dramatically reduces the machining difficulty of the MRA...
September 15, 2017: Optics Letters
Dong Ju Kim, Chi Yeon Lim, Namyi Gu, Choul Yong Park
PURPOSE: In the present study, the visual discomfort induced by smart mobile devices was assessed in normal and healthy adults. METHODS: Fifty-nine volunteers (age, 38.16 ± 10.23 years; male : female = 19 : 40) were exposed to tablet computer screen stimuli (iPad Air, Apple Inc.) for 1 hour. Participants watched a movie or played a computer game on the tablet computer. Visual fatigue and discomfort were assessed using an asthenopia questionnaire, tear film break-up time, and total ocular wavefront aberration before and after viewing smart mobile devices...
July 18, 2017: Korean Journal of Ophthalmology: KJO
Zina Zhang, Logan William Thomas, Szu-Yen Leu, Steven Carter, Sumit Garg
PURPOSE: To compare the outcomes of intraoperative wavefront aberrometry versus optical biometry alone for intraocular lens (IOL) power calculation in eyes undergoing cataract surgery with monofocal IOL implantation. METHODS: Preoperative data were obtained with the IOLMaster. Intraoperative aphakic measurements and IOL power calculations were obtained in some patients with the optiwave refractive analysis (ORA) system. Analysis was performed to determine the accuracy of monofocal IOL power prediction and postoperative manifest refraction at 1 month of the ORA versus IOLMaster...
September 2017: Indian Journal of Ophthalmology
Gary Tse, Mengqi Gong, Cheuk Wai Wong, Cynthia Chan, Stamatis Georgopoulos, Yat Sun Chan, Bryan P Yan, Guangping Li, Paula Whittaker, Ana Ciobanu, Sadeq Ali-Hasan-Al-Saegh, Sunny H Wong, William K K Wu, George Bazoukis, Konstantinos Lampropoulos, Wing Tak Wong, Lap Ah Tse, Adrian M Baranchuk, Konstantinos P Letsas, Tong Liu
BACKGROUND: The total cosine R-to-T (TCRT), a vectorcardiographic marker reflecting the spatial difference between the depolarization and repolarization wavefronts, has been used to predict ventricular tachycardia/fibrillation (VT/VF) and sudden cardiac death (SCD) in different clinical settings. However, its prognostic value has been controversial. OBJECTIVE: This systematic review and meta-analysis evaluated the significance of TRCT in predicting arrhythmic and/or mortality endpoints...
September 12, 2017: Annals of Noninvasive Electrocardiology
Michael Lasta, Kata Miháltz, Illés Kovács, Pia Veronika Vécsei-Marlovits
PURPOSE: To compare the effect of spherical aberration on optical quality in eyes with two different aspherical intraocular lenses. METHODS: 120 eyes of 60 patients underwent phacoemulsification. In patients' eyes, an aberration-free IOL (Aspira-aA; Human Optics) or an aberration-correcting aspherical IOL (Tecnis ZCB00; Abott Medical Optics) was randomly implanted. After surgery, contrast sensitivity and wavefront measurements as well as tilt and decentration measurements were performed...
2017: Journal of Ophthalmology
Egor Khaidarov, Hanfang Hao, Ramón Paniagua-Domínguez, Ye Feng Yu, Yuan Hsing Fu, Vytautas Valuckas, Sherry Lee Koon Yap, Yeow Teck Toh, Jeff Siu Kit Ng, Arseniy I Kuznetsov
Wavefront manipulation in metasurfaces typically relies on phase mapping with a finite number of elements. In particular, a discretized linear phase profile may be used to obtain a beam bending functionality. However, discretization limits the applicability of this approach for high angle bending due to the drastic efficiency drop when the phase is mapped by a small number of elements. In this work, we discuss a novel concept for energy redistribution in diffraction gratings and its application in the visible spectrum range, which helps overcome the constraints of ultrahigh angle (above 80°) beam bending...
September 18, 2017: Nano Letters
James P Hummel, Alex Baher, Ben Buck, Manuel Fanarjian, Charles L Webber, Joseph G Akar
INTRODUCTION: Spiral wave reentry is a potential mechanism of atrial fibrillation (AF), but is difficult to differentiate clinically from multiple wavelet breakup using standard bipolar recordings. We developed a new methodology using bipolar recordings to estimate the direction of local activation wavefronts during AF by calculating the electrogram conformation (Egm-C). We subsequently used recurrence quantification analysis (RQA) of Egm-C to differentiate regions of spiral wave reentry from wavelet breakup...
September 1, 2017: Computers in Biology and Medicine
Shouvik K Haldar, Karl Magtibay, Andreu Porta-Sanchez, Stéphane Massé, Nicholas Mitsakakis, Patrick F H Lai, Mohammed Ali Azam, John Asta, Marjan Kusha, Paul Dorian, Andrew C T Ha, Vijay Chauhan, D Curtis Deno, Kumaraswamy Nanthakumar
BACKGROUND: Low-voltage-guided substrate modification is an emerging strategy in atrial fibrillation (AF) ablation. A major limitation to contemporary bipolar electrogram (EGM) analysis in AF is the resultant lower peak-to-peak voltage (Vpp) from variations in wavefront direction relative to electrode orientation and from fractionation and collision events. We aim to compare bipole Vpp with novel omnipolar peak-to-peak voltages (Vmax) in sinus rhythm (SR) and AF. METHODS AND RESULTS: A high-density fixed multielectrode plaque was placed on the epicardial surface of the left atrium in dogs...
September 2017: Circulation. Arrhythmia and Electrophysiology
Hilton B de Aguiar, Sylvain Gigan, Sophie Brasselet
The control and use of light polarization in optical sciences and engineering are widespread. Despite remarkable developments in polarization-resolved imaging for life sciences, their transposition to strongly scattering media is currently not possible, because of the inherent depolarization effects arising from multiple scattering. We show an unprecedented phenomenon that opens new possibilities for polarization-resolved microscopy in strongly scattering media: polarization recovery via broadband wavefront shaping...
September 2017: Science Advances
Jun Lan, Yifeng Li, Yue Xu, Xiaozhou Liu
We designed a gradient acoustic metasurface to manipulate acoustic wavefront freely. The broad bandwidth and high efficiency transmission are achieved by the acoustic metasurface which is constructed with a series of unit cells to provide desired discrete acoustic velocity distribution. Each unit cell is composed of a decorated metal plate with four periodically arrayed Helmholtz resonators (HRs) and a single slit. The design employs a gradient velocity to redirect refracted wave and the impedance matching between the metasurface and the background medium can be realized by adjusting the slit width of unit cell...
September 6, 2017: Scientific Reports
Muhammad Waqas Khalid, Rajib Ahmed, Ali K Yetisen, Bader AlQattan, Haider Butt
The optical phase conjugation (OPC) through photonic nanostructures in coherent optics involves the utilization of a nonlinear optical mechanism through real-time processing of electromagnetic fields. Their applications include spectroscopy, optical tomography, wavefront sensing, and imaging. The development of functional and personalized holographic devices in the visible and near-infrared spectrum can be improved by introducing cost-effective, rapid, and high-throughput fabrication techniques and low-cost recording media...
September 6, 2017: Scientific Reports
Pao-Keng Yang
By using a light-emitting diode as the probing light source and a Shack-Hartmann wavefront sensor as the recorder for the wavefront surface to execute a relative measurement, we present a useful method for determining the small wedge angle and optical homogeneity of a nominally planar glass plate from the wavefront measurements. The measured wavefront surface from the light source was first calibrated to be a horizontal plane before the plate under test was inserted. The wedge angle of the plate can be determined from the inclining angle of the regression plane of the measured wavefront surface after the plate was inserted between the light source and the wavefront sensor...
August 2017: Review of Scientific Instruments
Xiangyu Meng, Xianbo Shi, Yong Wang, Ruben Reininger, Lahsen Assoufid, Renzhong Tai
The mutual optical intensity (MOI) model is extended to include the propagation of partially coherent radiation through non-ideal mirrors. The propagation of the MOI from the incident to the exit plane of the mirror is realised by local ray tracing. The effects of figure errors can be expressed as phase shifts obtained by either the phase projection approach or the direct path length method. Using the MOI model, the effects of figure errors are studied for diffraction-limited cases using elliptical cylinder mirrors...
September 1, 2017: Journal of Synchrotron Radiation
Tatsuo Kaneyasu, Yasumasa Hikosaka, Masaki Fujimoto, Hiroshi Iwayama, Masahito Hosaka, Eiji Shigemasa, Masahiro Katoh
The observation of an optical vortex beam at 60 nm wavelength, produced as the second-harmonic radiation from a helical undulator, is reported. The helical wavefront of the optical vortex beam was verified by measuring the interference pattern between the vortex beam from a helical undulator and a normal beam from another undulator. Although the interference patterns were slightly blurred owing to the relatively large electron beam emittance, it was possible to observe the interference features thanks to the helical wavefront of the vortex beam...
September 1, 2017: Journal of Synchrotron Radiation
Ponnuraj Kirthi Priya, M Ramasubba Reddy
BACKGROUND: To understand the ionic mechanism behind the genesis of Torsade de Pointes (TdP) occurring with long QT syndrome 2 (LQTS2) in a remodelled transmural tissue. METHODS: The TP06 model is used to simulate the electrical activity of cells in a 2D transmural ventricular model. LQTS2 is realised by reducing the potassium current (IKr) to 0.5 in each cell. Each cell of the tissue is remodelled by increasing the conductance of calcium current (GCaL). The above two factors make the cells prone to early after depolarizations (EADs) development...
August 24, 2017: Computers in Biology and Medicine
Jing Xu, Xiaolin Tian, Xin Meng, Yan Kong, Shumei Gao, Haoyang Cui, Fei Liu, Liang Xue, Cheng Liu, Shouyu Wang
Massive image acquisition is required along the optical axis in the classical image-analysis-based autofocus method, which significantly decreases autofocus efficiency. A wavefront-sensing-based autofocus technique is proposed to increase the speed of autofocusing and obtain high localization accuracy. Intensities at different planes along the optical axis can be computed numerically after extracting the wavefront at defocus position with the help of the transport-of-intensity equation method. According to the focus criterion, the focal plane can then be determined, and after sample shifting to this plane, the in-focus image can be recorded...
August 2017: Journal of Biomedical Optics
Zihao Xu, Chengliang Yang, Peiguang Zhang, Xingyun Zhang, Zhaoliang Cao, Quanquan Mu, Qiang Sun, Li Xuan
There are more than eight large aperture telescopes (larger than eight meters) equipped with adaptive optics system in the world until now. Due to the limitations such as the difficulties of increasing actuator number of deformable mirror, most of them work in the infrared waveband. A novel two-step high-resolution optical imaging approach is proposed by applying phase diversity (PD) technique to the open-loop liquid crystal adaptive optics system (LC AOS) for visible light high-resolution adaptive imaging...
August 30, 2017: Scientific Reports
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