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surface curvature

Hamed Rabiei, Frederic Richard, Olivier Coulon, Julien Lefevre
Gyrification index (GI) is an appropriate measure to quantify the complexity of the cerebral cortex. There is, however, no universal agreement on the notion of surface complexity and there are various methods in literature that evaluate different aspects of cortical folding. In this paper, we give two intuitive interpretations on folding quantification based on the magnitude and variation of the mean curvature of the cortical surface. We then present a local spectral analysis of the mean curvature to introduce two local gyrification indices that satisfy our interpretations...
November 29, 2016: IEEE Transactions on Medical Imaging
X M Pan, Z J Yang, X D Ma, Y L Zhu, N C Luhmann, C W Domier, B W Ruan, G Zhuang
A new 2D Electron Cyclotron Emission Imaging (ECEI) diagnostic is being developed for the J-TEXT tokamak. It will provide the 2D electron temperature information with high spatial, temporal, and temperature resolution. The new ECEI instrument is being designed to support fundamental physics investigations on J-TEXT including MHD, disruption prediction, and energy transport. The diagnostic contains two dual dipole antenna arrays corresponding to F band (90-140 GHz) and W band (75-110 GHz), respectively, and comprises a total of 256 channels...
November 2016: Review of Scientific Instruments
Ilya P Radko, Mads Boll, Niels M Israelsen, Nicole Raatz, Jan Meijer, Fedor Jelezko, Ulrik L Andersen, Alexander Huck
It is generally accepted that nitrogen-vacancy (NV) defects in bulk diamond are bright sources of luminescence. However, the exact value of their internal quantum efficiency (IQE) has not been measured so far. Here we use an implementation of Drexhage's scheme to quantify the IQE of shallow-implanted NV defects in a single-crystal bulk diamond. Using a spherical metallic mirror with a large radius of curvature compared to the optical spot size, we perform calibrated modifications of the local density of states around NV defects and observe the change of their total decay rate, which is further used for IQE quantification...
November 28, 2016: Optics Express
Kaori Kasahara, Naoyuki Maeda, Takashi Fujikado, Makoto Tomita, Muka Moriyama, Mutsumi Fuchihata, Kyoko Ohno-Matsui
PURPOSE: To investigate prospectively the characteristics in the higher-order aberrations and anterior segment tomography in patients with pathologic myopia. METHODS: One hundred and twelve consecutive highly myopic patients (mean age 43.4 ± 9.3 years, spherical equivalent of refractive error ≥8 D and an axial length ≥26.5 mm) were studied. Thirty-seven emmetropic individuals (mean age 37.0 ± 14.5 years, spherical equivalent of refractive error ≤ ±1 D) were analyzed as controls...
November 28, 2016: International Ophthalmology
Ibrahim Seven, Ali Vahdati, Vinicius Silbiger De Stefano, Ronald R Krueger, William J Dupps
Purpose: To assess the predictive accuracy of simulation-based LASIK outcomes. Methods: Preoperative and 3-month post-LASIK tomographic data from 20 eyes of 12 patients who underwent wavefront-optimized LASIK for myopia were obtained retrospectively. Patient-specific finite element models were created and case-specific treatment settings were simulated. Simulated keratometry (SimK) values and the mean tangential curvature of the central 3 mm (Kmean) were obtained from the anterior surfaces of the clinical tomographies, and computational models were compared...
November 1, 2016: Investigative Ophthalmology & Visual Science
Luis G M Basso, Eduardo F Vicente, Edson Crusca, Eduardo M Cilli, Antonio J Costa-Filho
Viral membrane fusion is an orchestrated process triggered by membrane-anchored viral fusion glycoproteins. The S2 subunit of the spike glycoprotein from severe acute respiratory syndrome (SARS) coronavirus (CoV) contains internal domains called fusion peptides (FP) that play essential roles in virus entry. Although membrane fusion has been broadly studied, there are still major gaps in the molecular details of lipid rearrangements in the bilayer during fusion peptide-membrane interactions. Here we employed differential scanning calorimetry (DSC) and electron spin resonance (ESR) to gather information on the membrane fusion mechanism promoted by two putative SARS FPs...
November 28, 2016: Scientific Reports
Jennifer Chung, Kevin Lachapelle, Raymond Cartier, Rosaire Mongrain, Richard L Leask
Biomechanical characterization of the aortic wall may help risk stratify patients with aneurysms. We investigated the degree of anisotropy, the directional dependency of mechanical properties, in control and aneurysmal ascending aortic tissue. We hypothesized that medial degeneration and aortic wall remodeling as found in aneurysmal tissue alter energy loss in both the circumferential and longitudinal directions, thereby reducing anisotropy. Aneurysmal and control ascending aortic tissue excised during surgery was subjected to biaxial tensile testing...
November 15, 2016: Cardiovascular Pathology: the Official Journal of the Society for Cardiovascular Pathology
Shanpeng Li, Jianlin Liu, Jian Hou
Directional motion of droplets or bubbles can often be observed in nature and our daily life, and this phenomenon holds great potential in many engineering areas. The study shows that droplets or bubbles can be driven to migrate perpetually on some special substrates, such as the Archimedean spiral, the logarithmic spiral and a cantilever sheet in large deflection. It is found that a bubble approaches or deviates from the position with highest curvature of the substrate, when it is on the concave or convex side...
November 25, 2016: Scientific Reports
Jiro Suzuki, Atsushi Takano, Yushu Matsushita
Morphology of symmetric ABCD tetrablock quaterpolymers in melt was studied by the Monte Carlo (MC) simulation, where the volume fractions of the block chains, f, kept the relationships of fA=fD and fB=fC, and the volume fraction of the two mid-blocks φ was defined as φ=fB+fC. Previous self-consistent field theory for ABCD reported morphological change including several structures; however, the scope was limited within a two-dimensional system. To the contrary, in this paper, MC simulations were carried out in three dimensions with changing the φ value finely, which resulted in finding a tetracontinuous structure in the range of 0...
November 21, 2016: Journal of Chemical Physics
Carlos Manuel Ortiz-Lima, Alberto Cordero-Dávila, Jorge González-García
Small rigid petal tools, driven by a traditional polishing machine, were used to parabolize 20 mirrors 14 cm in diameter and 192 cm of curvature radius. Small rigid circular tools (SCTs), driven manually, were used to parabolize another 20 identical surfaces. A Ronchi test with a square grid was used to evaluate the performance of both techniques. If small rigid petal tools are used, the surface quality, the reproducibility in the production process, and the time spent required to generate the surfaces are markedly better than using SCTs...
November 20, 2016: Applied Optics
Hefu Li, Weixing Yu, Taisheng Wang, Zhenyu Liu, M P Y Desmulliez
This article reports the numerical study of the one-step faithful replication of micro/nano-scale structures on a fiber surface using the electrohydrodynamic instability patterning (EHDIP) process. By employing a rigorous numerical analysis method, conditions are revealed under which the faithful replication of a pattern can be achieved from a curved master electrode. It is found that the radius of curvature of the fiber plays an important role in determining the final morphology of the pattern when the destabilizing electric field is dominant in both the flat and patterned template cases...
November 14, 2016: Electrophoresis
G A Santamaría-Botello, L E García Muñoz, F Sedlmeir, S Preu, D Segovia-Vargas, K Atia Abdalmalak, S Llorente Romano, A García Lampérez, S Malzer, G H Döhler, H G L Schwefel, H B Weber
In this paper, a detailed description of the optical coupling into a Whispering Gallery Mode (WGM) resonator through a prism via frustrated total internal reflection (FTIR) is presented. The problem is modeled as three media with planar interfaces and closed expressions for FTIR are given. Then, the curvature of the resonator is taken into account and the mode overlap is theoretically studied. A new analytical expression giving the optimal geometry of a disc-shaped or ring-shaped resonator for maximizing the intra-cavity circulating power is presented...
November 14, 2016: Optics Express
Martin Rabe, Christopher Aisenbrey, Kristyna Pluhackova, Vincent de Wert, Aimee L Boyle, Didjay F Bruggeman, Sonja A Kirsch, Rainer A Böckmann, Alexander Kros, Jan Raap, Burkhard Bechinger
A system based on two designed peptides, namely the cationic peptide K, (KIAALKE)3, and its complementary anionic counterpart called peptide E, (EIAALEK)3, has been used as a minimal model for membrane fusion, inspired by SNARE proteins. Although the fact that docking of separate vesicle populations via the formation of a dimeric E/K coiled-coil complex can be rationalized, the reasons for the peptides promoting fusion of vesicles cannot be fully explained. Therefore it is of significant interest to determine how the peptides aid in overcoming energetic barriers during lipid rearrangements leading to fusion...
November 15, 2016: Biophysical Journal
Lucila Peralta Gavensky, Gonzalo Usaj, C A Balseiro
The topological structure of the wavefunctions of particles in periodic potentials is characterized by the Berry curvature Ωkn whose integral on the Brillouin zone is a topological invariant known as the Chern number. The bulk-boundary correspondence states that these numbers define the number of edge or surface topologically protected states. It is then of primary interest to find experimental techniques able to measure the Berry curvature. However, up to now, there are no spectroscopic experiments that proved to be capable to obtain information on Ωkn to distinguish different topological structures of the bulk wavefunctions of semiconducting materials...
November 11, 2016: Scientific Reports
H Ishida
We calculate the decay length in surface normal direction of the surface-state wave functions on a clean Bi(1 1 1) surface as a function of two-dimensional (2D) wave vector [Formula: see text] along the [Formula: see text] line. For this purpose, we perform a first-principles density functional theory (DFT) calculation for semi-infinite Bi(1 1 1) by employing the surface embedded Green's function technique. The decay length of the two surface bands is found to be  ∼24 Bi bilayers at [Formula: see text], while it remains less than 5 Bi bilayers when [Formula: see text] is away from [Formula: see text] and [Formula: see text]...
November 10, 2016: Journal of Physics. Condensed Matter: An Institute of Physics Journal
Weiqian Zhao, Lirong Qiu, Yang Xiao, Jiamiao Yang
Different measurement methods have been used to achieve different parameter measurements of a spherical lens, and multi-parameter measurements of a spherical lens have low measurement accuracy and efficiency. This paper proposes a new, laser differential confocal interference multi-parameter measurement (DCIMPM) method for spherical lens. Based on this proposed DCIMPM, a multi-parameter comprehensive measurement system is developed for spherical lens, which uses the laser differential confocal parameter measurement technique to measure the radius of curvature, thickness, and refractivity of spherical lens, and uses the laser interference measurement technique to measure the surface figure of a spherical lens...
October 3, 2016: Optics Express
Fanyang Dang, Wang Zhang, Shouqian Chen, Hui Wang, Van Nhu Le, Jiaqian Yu, Zhigang Fan
This paper investigated the geometry and aberration characteristics of conicoidal conformal domes. First, on the basis of previous research, we got the expression that was suitable for describing the external surface of the conicoidal conformal dome. Based on the theory of differential geometry, this paper first proved that the Dupin index line of a quadric surface was an ellipsoid and the radius of curvature had extreme values in the meridian plane and sagittal plane. Then the uniform formulas of curvature which were suitable for ellipsoid, paraboloid, and hyperboloid were deduced in the meridian plane and sagittal plane, respectively...
November 1, 2016: Applied Optics
Sabine Akerboom, Marleen Kamperman, Frans A M Leermakers
We use regular solution theory and implement a three-gradient model for a liquid/vapour system in contact with a complex surface topology to study the shape of a liquid drop in advancing and receding wetting scenarios. More specifically, we study droplets on an inverse opal: spherical cavities in a hexagonal pattern. In line with experimental data, we find that the surface may switch from hydrophilic (contact angle on a smooth surface θY < 90°) to hydrophobic (effective advancing contact angle θ > 90°)...
2016: Beilstein Journal of Nanotechnology
Yang Jae Kim, Michael C Knorz, Gerd U Auffarth, Chul Young Choi
PURPOSE: To analyze the change in anterior and posterior corneal curvature after cataract surgery using a Placido-dual rotating Scheimpflug device. METHODS: In a prospective cross-sectional study, corneal curvature was measured using the Galilei G4 device (Ziemer Ophthalmic Systems, Port, Switzerland) preoperatively and 1 week and 1, 3, and 6 months after cataract surgery with a temporal limbal self-sealing 2.2-mm incision. The surgically induced astigmatism (SIA) was determined on the anterior and posterior surfaces...
November 1, 2016: Journal of Refractive Surgery
Thao T T Nguyen, Akshay Kundan, Peter C Wayner, Joel L Plawsky, David F Chao, Ronald J Sicker
Understanding the dynamics of phase change heat and mass transfer in the three-phase contact line region is a critical step toward improving the efficiency of phase change processes. Phase change becomes especially complicated when a fluid mixture is used. In this paper, a wickless heat pipe was operated on the International Space Station (ISS) to study the contact line dynamics of a pentane/isohexane mixture. Different interfacial regions were identified, compared, and studied. Using high resolution (50×), interference images, we calculated the curvature gradient of the liquid-vapor interface at the contact line region along the edges of the heat pipe...
October 28, 2016: Journal of Colloid and Interface Science
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