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F Scarpa, A Ruggeri, F Scarpa, A Ruggeri, A Ruggeri, F Scarpa
Corneal images acquired by in-vivo specular and confocal microscopy provide clinical information on the cornea endothelium health state. Indeed, the normal hexagonal shape of endothelial cells is usually affected by age and pathologies. At present, the analysis is based on manual or semi-automatic methods and the segmentation of a large number of endothelial cells is required for a meaningful estimation of the clinical parameters. We propose an automated method that detects the centers of endothelial cells by convolving the original image with customized two-dimensional kernels, derives a structure made by connected vertices from the recognized centers using the Euclidean distance, and fine-tunes the derived structure through a genetic algorithm, which combines information about the typical regularity of endothelial cells shape with the pixels intensity of the actual image...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Samar M Alsaleh, Angelica I Aviles, Pilar Sobrevilla, Alicia Casals, James K Hahn, Samar M Alsaleh, Angelica I Aviles, Pilar Sobrevilla, Alicia Casals, James K Hahn, Angelica I Aviles, Samar M Alsaleh, Alicia Casals, Pilar Sobrevilla, James K Hahn
Minimally invasive surgical and diagnostic systems rely on endoscopic images of internal organs to assist medical tasks. Specular highlights are common on those images due to the strong reflectivity of the mucus layer on the organs and the relatively high intensity of the light source. This is a significant source of error that can affect the systems' performance. In this paper, we propose a segmentation method of the specular regions based on an automatic color-adaptive threshold and a gradient-based edge detector...
August 2016: Conference Proceedings: Annual International Conference of the IEEE Engineering in Medicine and Biology Society
Florence Sarah Blachon, Frederic F Harb, Bogdan Munteanu, Agnès Piednoir, Remy Fulcrand, Thierry Charitat, Giovanna Fragneto, Olivier Pierre-Louis, Bernard Tinland, Jean-Paul Rieu
In vivo lipid membranes interact with rough supramolecular structures such as protein clusters and fibrils. How these features whose size ranges from a few nanometers to a few tens of nanometers impact lipid and protein mobility is still investigated. Here, we study supported phospholipid bilayers, a unique biomimetic model, deposited on etched surfaces bearing nanometric corrugations. Surface roughness and mean curvature are carefully characterized by AFM imaging using ultrasharp tips. Neutron specular reflectivity supplements this surface characterization, and indicates that the bilayers follow the large scale corrugations of the substrate...
February 20, 2017: Langmuir: the ACS Journal of Surfaces and Colloids
Mohammad Memarian, Xiaoqiang Li, Yasuo Morimoto, Tatsuo Itoh
Blazed gratings can reflect an oblique incident wave back in the path of incidence, unlike mirrors and metal plates that only reflect specular waves. Perfect blazing (and zero specular scattering) is a type of Wood's anomaly that has been observed when a resonance condition occurs in the unit-cell of the blazed grating. Such elusive anomalies have been studied thus far as individual perfect blazing points. In this work, we present reflective blazed surfaces that, by design, have multiple coupled blazing resonances per cell...
February 17, 2017: Scientific Reports
Irina Ginzburg
Impact of the unphysical tangential advective-diffusion constraint of the bounce-back (BB) reflection on the impermeable solid surface is examined for the first four moments of concentration. Despite the number of recent improvements for the Neumann condition in the lattice Boltzmann method-advection-diffusion equation, the BB rule remains the only known local mass-conserving no-flux condition suitable for staircase porous geometry. We examine the closure relation of the BB rule in straight channel and cylindrical capillary analytically, and show that it excites the Knudsen-type boundary layers in the nonequilibrium solution for full-weight equilibrium stencil...
January 2017: Physical Review. E
Irina Ginzburg
The effect of the heterogeneity in the soil structure or the nonuniformity of the velocity field on the modeled resident time distribution (RTD) and breakthrough curves is quantified by their moments. While the first moment provides the effective velocity, the second moment is related to the longitudinal dispersion coefficient (k_{T}) in the developed Taylor regime; the third and fourth moments are characterized by their normalized values skewness (Sk) and kurtosis (Ku), respectively. The purpose of this investigation is to examine the role of the truncation corrections of the numerical scheme in k_{T}, Sk, and Ku because of their interference with the second moment, in the form of the numerical dispersion, and in the higher-order moments, by their definition...
January 2017: Physical Review. E
Jianxun Su, Yao Lu, Hui Zhang, Zengrui Li, Yaoqing Lamar Yang, Yongxing Che, Kainan Qi
In this paper, an ultra-wideband, wide angle and polarization-insensitive metasurface is designed, fabricated, and characterized for suppressing the specular electromagnetic wave reflection or backward radar cross section (RCS). Square ring structure is chosen as the basic meta-atoms. A new physical mechanism based on size adjustment of the basic meta-atoms is proposed for ultra-wideband manipulation of electromagnetic (EM) waves. Based on hybrid array pattern synthesis (APS) and particle swarm optimization (PSO) algorithm, the selection and distribution of the basic meta-atoms are optimized simultaneously to obtain the ultra-wideband diffusion scattering patterns...
February 9, 2017: Scientific Reports
Kai Wang, Jingping Zhu, Hong Liu, Bingzheng Du
An expression of the degree of polarization (DOP) based on the geometrical optics polarimetric bidirectional reflectance distribution function model is presented. In this expression, the DOP is related to the surface roughness and decreases at different reflection angles because diffuse reflection is taken into consideration. A shadowing/masking function introduced into the specular reflection expression makes the DOP values decrease as the angle of incidence or observation approaches grazing. Different kinds of materials were measured to validate the accuracy of this DOP expression...
February 1, 2017: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
Qian-Kun Li, Jia-Ji Cao, Yan-Hao Yu, Lei Wang, Yun-Lu Sun, Qi-Dai Chen, Hong-Bo Sun
Herein, we report a facile approach for the maskless production of subwavelength-structured antireflective surfaces on sapphire with high and broadband transmittance in the mid-IR: femtosecond laser direct writing assist with wet etching. With this method, inverted pyramid and cone arrays with a pitch of about 2 μm and a total height of near 900 nm on the sapphire were produced. The resulting subwavelength structures greatly suppress specular reflection at normal incidence. The transmission measurements between 3 and 5 μm are in agreement with the simulations performed using VirtualLab, and the transmittance reached a maximum value of 92...
February 1, 2017: Optics Letters
Khoa D Tran, Philip K Dye, Kelly Odell, Joshua Galloway, Christopher G Stoeger, Michael D Straiko, Mark A Terry
PURPOSE: To determine graft quality and feasibility of Descemet membrane endothelial keratoplasty (DMEK) grafts that are prestripped and preloaded into injectors by eye bank technicians before shipping to surgeons. METHODS: DMEK grafts (n = 31) were prepared from donor corneas and preloaded into Straiko Modified Jones tubes and set inside viewing chambers filled with 20 mL of Optisol-GS. Preloaded grafts were evaluated using specular microscopy and slit-lamp biomicroscopy...
January 26, 2017: Cornea
Pascal Lecocq, Arthur Dufay, Gael Sourimant, Jean-Eudes Marvie
We introduce analytic approximations for accurate real-time rendering of surfaces lit by non-occluded area light sources. Our solution leverages the Irradiance Tensors developed by Arvo for the shading of Phong surfaces lit by a polygonal light source. Using a reformulation of the 1D boundary edge integral, we develop a general framework for approximating and evaluating the integral in constant time using simple peak shape functions. To overcome the Phong restriction, we propose a low cost edge splitting strategy that accounts for the spherical warp introduced by the half vector parametrization...
January 23, 2017: IEEE Transactions on Visualization and Computer Graphics
Vahid Shahabi, Tobias Baier, Ehsan Roohi, Steffen Hardt
A net gas flow can be induced in the gap between periodically structured surfaces held at fixed but different temperatures when the reflection symmetry along the channel axis is broken. Such a situation arises when one surface features a ratchet structure and can be augmented by altering the boundary conditions on different parts of this surface, with some regions reflecting specularly and others diffusely. In order to investigate the physical mechanisms inducing the flow in this configuration at various Knudsen numbers and geometric configurations, direct simulation Monte Carlo (DSMC) simulations are employed using transient adaptive subcells for collision partner selection...
January 27, 2017: Scientific Reports
Xiaoming Sun, Ye Liu, Xiaoyang Yu, Haibin Wu, Ning Zhang
Due to the strong reflection property of materials with smooth surfaces like ceramic and metal, it will cause saturation and the highlight phenomenon in the image when taking pictures of those materials. In order to solve this problem, a new algorithm which is based on reflection component separation (RCS) and priority region filling theory is designed. Firstly, the specular pixels in the image are found by comparing the pixel parameters. Then, the reflection components are separated and processed. However, for ceramic, metal and other objects with strong specular highlight, RCS theory will change color information of highlight pixels due to larger specular reflection component...
January 23, 2017: Sensors
Elena Koudouna, Naoki Okumura, Yugo Okazaki, Shinichiro Nakano, Ryota Inoue, Nigel J Fullwood, Junko Hori, Shigeru Kinoshita, Noriko Koizumi
Purpose: Corneal endothelial cell density undergoes a progressive decrease for many years after transplantation, eventually threatening patients with late endothelial failure. The purpose of this study was to investigate the possibility of an immunologic response in successfully grafted corneal endothelium. Methods: The corneal endothelium of patients who had undergone corneal transplantation was evaluated by specular microscopy. Rabbit models were subjected to penetrating keratoplasty (PK) with either syngeneic or allogeneic corneal transplants and Descemet's stripping endothelial keratoplasty (DSEK) with allogeneic corneal transplants...
January 1, 2017: Investigative Ophthalmology & Visual Science
Raja Sekhar Bandaru, Anders Sornes, Jeroen Hermans, Eigil Samset, Jan D'hooge
Although interventional devices such as needles, guide wires and catheters are best visualized by X-ray, real-time volumetric echography could offer an attractive alternative as it avoids ionizing radiation; it provides good soft tissue contrast and it is mobile and relatively cheap. Unfortunately, as echography is traditionally used to image soft tissue and blood flow, the appearance of interventional devices in conventional ultrasound images remains relatively poor which is a major obstacle towards ultrasound-guided interventions...
September 27, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Jingtang Liao, Bert Buchholz, Jean-Marc Thiery, Pablo Bauszat, Elmar Eisemann
We propose a novel framework for photometric stereo (PS) under low-light conditions using uncalibrated nearlight illumination. It operates on free-form video sequences captured with a minimalistic and affordable setup. We address issues such as albedo variations, shadowing, perspective projections and camera noise. Our method uses specular spheres detected with a perspective-correcting Hough transform to robustly triangulate light positions in the presence of outliers via a least-squares approach. Furthermore, we propose an iterative reweighting scheme in combination with an `p-norm minimizer to robustly solve the calibrated near-light PS problem...
December 7, 2016: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
Ivan Rosado-Mendez, Lindsey Drehfal, James Zagzebski, Timothy Hall
The estimation of most spectral-based, Quantitative Ultrasound parameters assumes that backscattered echo signals are from a stationary, incoherent scattering process. The accuracy of these assumptions in real tissue can limit the diagnostic value of these parameters and the physical insight about tissue microstructure they can convey. This work presents an empirical decision test to determine the presence of significant coherent contributions to echo signals and whether they are caused by low scatterer number densities or the presence of specular reflectors or scatterers with periodic spacing...
March 25, 2016: IEEE Transactions on Ultrasonics, Ferroelectrics, and Frequency Control
Jaesik Park, Sudipta Sinha, Yasuyuki Matsushita, Yu Wing Tai, In So Kweon
We propose a robust uncalibrated multiview photometric stereo method for high quality 3D shape reconstruction. In our method, a coarse initial 3D mesh obtained using a multiview stereo method is projected onto a 2D planar domain using a planar mesh parameterization technique. We describe methods for surface normal estimation that work in the parameterized 2D space that jointly incorporates all geometric and photometric cues from multiple viewpoints. Using an estimated surface normal map, a refined 3D mesh is then recovered by computing an optimal displacement map in the same 2D planar domain...
September 13, 2016: IEEE Transactions on Pattern Analysis and Machine Intelligence
Jinli Suo, Dongsheng An, Xiangyang Ji, Haoqian Wang, Qionghai Dai
Specular reflection exists widely in photography and causes the recorded color deviating from its true value, thus, fast and high quality highlight removal from a single nature image is of great importance. In spite of the progress in the past decades in highlight removal, achieving wide applicability to the large diversity of nature scenes is quite challenging. To handle this problem, we propose an analytic solution to highlight removal based on an L2 chromaticity definition and corresponding dichromatic model...
August 31, 2016: IEEE Transactions on Image Processing: a Publication of the IEEE Signal Processing Society
K Zaarour, E Slim, J Antoun, N Waked
INTRODUCTION: We herein report a case of bilateral unusually thick non-edematous keratoconic corneas with associated endothelial features of posterior polymorphous corneal dystrophy (PPCD). CASE REPORT: We report the case of a 27-year-old myopic woman who presented for refractive surgery. Slit lamp exam showed bilateral corneal protrusion with diffuse deep stromal and endothelial vesicular opacities and small paracentral bands. Topography showed generalized advanced corneal steepening in both eyes with increased anterior and posterior central corneal elevations in comparison to the best fit sphere...
January 12, 2017: Journal Français D'ophtalmologie
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