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1
Hao, Zhichao, and Yuankun Liu. "Transparent Object Shape Measurement Based on Deflectometry." Proceedings 2, no. 8 (July 9, 2018): 548. http://dx.doi.org/10.3390/icem18-05428.
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This paper proposes a method for obtaining surface normal orientation and 3-D shape of plano-convex lens using refraction stereo. We show that two viewpoints are sufficient to solve this problem under the condition that the refractive index of the object is known. What we need to know is that (1) an accurate function that maps each pixel to the refraction point caused by the refraction of the object. (2) light is refracted only once. In the simulation, the actual measurement process is simplified: light is refracted only once; and the accurate one-to-one correspondence between incident ray and refractive ray is realized by known object points. The deformed grating caused by refraction point is also constructed in the process of simulation. A plano-convex lens with a focal length of 242.8571 mm is used for stereo data acquisition, normal direction acquisition, and the judgment of normal direction consistency. Finally, restoring the three-dimensional information of the plano-convex lens by computer simulation. Simulation results suggest that our method is feasibility. In the actual experiment, considering the case of light is refracted more than once, combining the calibration data acquisition based on phase measurement, phase-shifting and temporal phase-unwrapping techniques to complete (1) calibrating the corresponding position relationship between the monitor and the camera (2) matching incident ray and refractive ray.
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Qiao, Xiaorui, Atsushi Yamashita, and Hajime Asama. "Underwater Structure from Motion for Cameras Under Refractive Surfaces." Journal of Robotics and Mechatronics 31, no. 4 (August 20, 2019): 603–11. http://dx.doi.org/10.20965/jrm.2019.p0603.
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Structure from Motion (SfM), as a three-dimensional (3D) reconstruction technique, can estimate the structure of an object by using a single moving camera. Cameras deployed in underwater environments are generally confined to waterproof housings. Thus, the light rays entering the camera are refracted twice; once at the interface between the water and the camera housing, and again at the interface between the camera housing and air. Images captured from scenes in underwater environments are prone to, and deteriorate, from distortion caused by this refraction. Severe distortions in geometric reconstruction would be caused if the refractive distortion is not properly addressed. Here, we propose a SfM approach to deal with the refraction in a camera system including a refractive surface. The impact of light refraction is precisely modeled in the refractive model. Based on the model, a new calibration and camera pose estimation method is proposed. This proposed method assists in accurate 3D reconstruction using the refractive camera system. Experiments, including simulations and real images, show that the proposed method can achieve accurate reconstruction, and effectively reduce the refractive distortion compared to conventional SfM.
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Zhi Chen, Zhi Chen, Honglan Xie Honglan Xie, Biao Deng Biao Deng, Guohao Du Guohao Du, Huaidong Jiang Huaidong Jiang, and Tiqiao Xiao Tiqiao Xiao. "Toward one nanometer X-ray focusing: a complex refractive lens design." Chinese Optics Letters 12, no. 12 (2014): 123401–4. http://dx.doi.org/10.3788/col201412.123401.
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Ding, Xiaohu, Wei Wang, Jane Scheetz, and Mingguang He. "The Guangzhou Twin Eye Study: 2019 Update." Twin Research and Human Genetics 22, no. 6 (December 2019): 492–98. http://dx.doi.org/10.1017/thg.2019.118.
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AbstractThe primary aim of the Guangzhou Twin Eye Study (GTES) is to explore the impact that genes and environmental influences have on common eye diseases. Since 2006, approximately 1300 pairs of twins, aged 7–15 years, were enrolled at baseline. Progressive phenotypes, such as cycloplegic refraction, axial length, height and weight, have been collected annually. Nonprogressive phenotypes such as parental refraction, corneal thickness, fundus photo, intraocular pressure and DNA were collected once at baseline. We are collaborating with fellow international twin researchers and psychologists to further explore links with general medical conditions. In this article, we review the history, major findings and future research directions for the GTES.
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Liu, Bin, Quan Yong Shen, Jian Mei Ye, Zi Qing Xie, and Min Yan Xu. "Characteristics of the Lateral Shift at the Surface of the Metamaterial." Applied Mechanics and Materials 201-202 (October 2012): 238–41. http://dx.doi.org/10.4028/www.scientific.net/amm.201-202.238.
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In some metamaterial such as the chiral negative refraction medium, the lateral shift is analyzed in theory. When total internal reflection occurs, the lateral shift curves as the incident angle have been figured out for a linearly polarized incident wave. The shift directions of the TM and TE components in the reflected wave are opposite when the incident angle is between the two critical angles of the eigen-waves. Both TM and TE waves will have positive lateral shift once the incident angle is larger than the total internal reflection angle. By contrast with the common medium and normal chiral medium, we have found that the lateral shift character in the chiral negative refraction medium is distinctive.
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Sivak, Jacob G., and Jeremy M. Sivak. "Conserved characteristics of ocular refractive development – Did the eye evolve once?" Experimental Eye Research 183 (June 2019): 84–87. http://dx.doi.org/10.1016/j.exer.2018.05.007.
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Marshall, Robert E., and Katherine L. Horgan. "Multi-wavelength radar target detection in an extreme advection duct event." International Journal of Microwave and Wireless Technologies 3, no. 3 (April 4, 2011): 373–81. http://dx.doi.org/10.1017/s1759078711000225.
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Near sea surface radio frequency (RF) refraction is four dimensional (4D) and can significantly impact the performance of radar systems. The refractivity field is dictated by the vertical thermodynamic structure of the constantly evolving marine atmospheric boundary layer (MABL). Logistical and budgetary restraints on meteorological measurements over water to capture the spatio-temporal structure of refractivity fields influencing radar performance have limited the knowledge of how and why radar performance is azimuth, range, and time dependent. Rapidly increasing computer processing speeds and decreasing memory capacity costs have supported the horizontal and vertical resolution requirements for mesoscale numerical weather prediction (NWP) models to resolve the thermodynamic structure in the MABL. Once modeled, refractivity structure is easily calculated from the thermodynamic structure. Mesoscale NWP models coupled with modern parabolic equation radar performance models can support the prediction of 4D radar performance in challenging non-homogeneous, near surface refractivity fields at the time and location of the modeler's choice. The NWP modeling presented in this paper demonstrates how large-scale offshore flow of warm and dry air over colder seas produces strong near surface RF trapping. Large land-sea temperature differences can produce near shore sea breezes and surface-based ducts. This paper describes modeled radar performance in such a complex ducting structure over the Persian Gulf during large-scale northwest atmospheric flow. The refractivity field was resolved by the Coupled Ocean/ Atmosphere Mesoscale Prediction System (COAMPS® is a registered trademark of the Naval Research Laboratory) and the notional radar performance was modeled by the advanced refractive effects prediction system (AREPS). The results indicate strong spatial and wavelength-dependent enhancements and degradations in radar performance relative to a standard atmosphere.
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Wade, Nicholas J. "Light and Sight since Antiquity." Perception 27, no. 6 (June 1998): 637–70. http://dx.doi.org/10.1068/p270637.
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Light and sight were not distinguished from one another until the dioptrics and the anatomy of the eye had been adequately described in the seventeenth century. A survey of early theories of light is presented, together with descriptions of developing knowledge of ocular anatomy Once the analogy between the eye and a camera had been made, the problem of accommodation was exposed, and corrections for errors of refraction could be given theoretical support. Theories of accommodation in the seventeenth and eighteenth centuries are briefly reviewed, as is the early history of eye glasses.
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Ganapathy, Boopalan, and Subramaniam Chittur Krishnaswamy. "Energy Transfer Using Gradient Index Metamaterial." International Journal of Antennas and Propagation 2018 (2018): 1–6. http://dx.doi.org/10.1155/2018/7946168.
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The gradient refractive index structure in this paper is used to increase the quantum of energy transfer. This is done by improving the directive gain of the pyramidal horn antenna at a frequency of 10 GHz. A three-dimensional array of closed square rings is placed in front of the horn antenna aperture to form a gradient refractive index structure. This structure increases the directive gain by 1.6 dB as compared to that of the conventional horn antenna. The structure nearly doubles the wireless power transfer quantum between the transmitter and the receiver when placed at both ends. The increase in the directivity is achieved by converting the spherical wave emanating from the horn to a plane wave once it passes through the structure. This transformation is realized by the gradient refractive index structure being placed perpendicular to the direction of propagation. The gradient refractive index is constructed by changing the dimensions of a closed square ring placed in the unit cell of the array. The change in the refractive index gives rise to an improvement of the half power beam width and side lobe level compared to that of the normal horn. The design and simulation were done using CST Studio software.
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Mineeva, L. A., L. I. Balashevich, A. A. Kozhukhov, A. A. Baranov, L. B. Shubin, and A. V. Kabanov. "Blood glucose level impact on biometric parameters, refraction and intraocular pressure in patients with subcompensated insulin-requiring type II diabetes." Russian Ophthalmological Journal 12, no. 1 (March 16, 2019): 35–42. http://dx.doi.org/10.21516/2072-0076-2019-12-1-35-42.
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Purpose. To study the relationship of biometric parameters, visual acuity, eye refraction and intraocular pressure (IOP) with blood glucose levels and glycated hemoglobin (HbA1c) in patients with subcompensated insulin-requiring type II diabetes mellitus. Material and methods. Ophthalmic monitoring lasted 3 years, the experience of insulin therapy — 6 years. 32 patients (27 women and 5 men) with insulin-requiring diabetes mellitus and no severe general diabetic complications or concomitant eye pathology were monitored for 3 years. The patients’ average age was 60.4 ± 5.3 years; average weight 94.3 ± 16.5 kg; average height 163.4 cm; average BMI (body mass index) was 29.93 kg/m2, all received insulin treatment for 6 years. Patients determined the level of blood glucose themselves on a daily basis using individual “Accu-Check” and/or “OneTouch select” glucometers, supplemented by endocrinologist checks on scheduled examinations once a month. The level of glycated hemoglobin (HbA1c) was determined once every 3–6 months. The 3-year ophthalmic monitoring involved both eyes and included biomicroscopy, autorefractometry, pneumotonometry, measurement of the anterior-posterior axis, the depth of the anterior chamber and lens thickness; pachymetry of the cornea in the central optical zone, and ophthalmoscopy. Visometry was performed according to ETDRS (Early Treatment Diabetic Retinopathy Study Research Group) requirements. Results. The impact of blood glucose level on visual acuity (Spearman R = 0.18/-0.23, t (N-2) = 1.07/-1.34, p = 0.1) is higher than that of HbA1c (Spearman R = 0.07/-0.15, t (N-2) = 0.4/-0.8, p = 0.65) The higher the glucose level, the lower the depth of the anterior chamber and the shorter the APA. In contrast, the higher the level of HbA1c, the thicker the cornea in the central optical zone. Both the glucose and the HbA1c levels reveal a similar positive correlations with IOP. A refraction shift toward myopia from 42 % to 55 % was shown to correlate to HbA1c, and a corresponding reduction of hyperopia share was revealed. Conclusions. In patients with subcompensated insulin-requiring diabetes mellitus type II, biometric parameters, refraction and intraocular pressure are determined by changes in the level of blood glycemia.
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Umunakwe, Ifeoma Janefrances, Reginald Umunakwe, Victor Adeola Popoola, Uzoma Samuel Nwigwe, and Akinlabi Oyetunji. "Evaluating the Extender Characteristics of Some Local Materials in Akure, Ondo State, Nigeria for Applications in the Paints Industry." MRS Advances 4, no. 43 (2019): 2355–65. http://dx.doi.org/10.1557/adv.2019.258.
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ABSTRACTSoil samples were obtained from three different locations; Ijapo, Ibule and FUTA North Gate in Akure, Ondo State, Nigeria. The materials were dried, crushed and calcined by heating the samples in a muffle furnace to 850 °C, holding for three hours and and then brought out of the furnace to cool in the laboratory so that the organic and volatile matter escaped, and the oxide content increased. The calcined materials were milled with a ball mill and then sieved with 75 µm mesh size British standard sieves. The samples that passed through the sieves were collected for analysis to determine their extender characteristics through x-ray flouresence (XRF) spectroscopy, x-ray diffraction (XRD) analysis, scanning electron microscopy (SEM), specific gravity, oil absorption, pH and refractive index measurements as well as the determination of their resistance to chemicals. XRF results showed that materials are kaolinite in nature. XRD results showed the phase compositions of each sample as materials suitable for applications as extenders in the paints industry. SEM micrographs showed the homogeneity of the samples from Ijapo and FUTA North Gate while the sample from Ibule showed segregation of the phase compositions. The specific gravity, pH, oil absorption and refractive index of each material were within the range of those of commercial extenders used in the paints industry. The calcined materials were found to be resistant to various chemical media. The characterized materials will be suitable as extenders and pigments in the paints industry.
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Biriukov, Dmitry. "Ancient Natural Philosophy in Byzantine Christology: The Issue of Penetration of Fire into Iron." Vestnik Volgogradskogo gosudarstvennogo universiteta. Serija 4. Istorija. Regionovedenie. Mezhdunarodnye otnoshenija, no. 6 (January 2020): 305–15. http://dx.doi.org/10.15688/jvolsu4.2019.6.24.
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Introduction. The author shows how the Stoic principle of total blending of physical bodies finds its refraction in the Byzantine Christological teachings on the example of penetration of fire into iron. According to the Stoics, total blending occurs when one body accepts certain qualities of the other, however, remaining themselves, or both mixed bodies acquire qualities of each other preserving their natures. Analysis. The author asserts that Origen’s use of the example of iron incandesced by fire turned out to be paradigmatic for the subsequent Christian literature, and influenced the formation of two directions of using this example at once: in Christological context, as well as to describe deification of man. Further, the author addresses to Christological problematics and claims that using the incandesced iron example in Byzantium literature in properly Christological context began with Apollinarius of Laodicea. The paper also investigates the specificity of the refraction of this example in Christological perspective in (Ps.-) Basil of Caesarea, Theodoret of Cyrus, Cyril of Alexandria, Severus of Antioch, John of Damascus, and Corpus Leontianum. Results. In this context, the author pays special attention to the discrepancy between John Damascus and Leontius of Jerusalem regarding the issue of the complexity of Christ’s hypostasis. The researcher clarifies prerequisites of this discrepancy.
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Luo, Jian Yi, Yang Yang Zhou, Dong Huang, Qing Guang Zeng, and Yi Wang. "Write-Once Optical Recording Property of Amorphous WO3 Thin Film and its Relative Mechanism." Advanced Materials Research 529 (June 2012): 69–73. http://dx.doi.org/10.4028/www.scientific.net/amr.529.69.
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Write-once optical recording property of the amorphous WO3 (a-WO3) thin film prepared on the glass substrate by thermal evaporation deposition, has been demonstrated by focusing the laser of 514.5 nm with a variable power to a spot with a size of 1-2μm in diameter on the surface of thin film. The mechanisms responsible for the refractive index change of thin film after the laser recording, has also been studied by monitoring the Raman signal change with the increase of the incident laser power, and by characterizing the micro-structures of the pits induced by laser irradiation. As a result, two mechanisms, the laser-induced phase transition and the laser-induced micro-explosion, are proposed to be responsible for the write-once optical recording.
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Meduri, Alessandro, Loredana Bergandi, Pietro Perroni, Francesca Silvagno, and Pasquale Aragona. "Oral l-Cysteine Supplementation Enhances the Long Term-Effect of Topical Basic Fibroblast Growth Factor (bFGF) in Reducing the Corneal Haze after Photorefractive Keratectomy in Myopic Patients." Pharmaceuticals 13, no. 4 (April 15, 2020): 67. http://dx.doi.org/10.3390/ph13040067.
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We aimed at evaluating the long-term effects of l-cysteine oral supplementation to basic fibroblast growth factor (bFGF) eye-drops on corneal re-epithelization and transparency in myopic patients subjected to photorefractive keratectomy (PRK). Forty patients subjected to bilateral PRK for myopia were enrolled and randomly divided into two groups receiving an additional therapy together with the standard postoperative treatment consisting in local tobramycin 0.3%, dexamethasone 0.1%, diclofenac 0.1%, and 0.2% hyaluronate. Group 1 included 20 patients (11 males and 9 females; 34.09 ± 8 years of age) receiving only bFGF eye-drops (10 μg/10 μL) four times a day for 7 days starting from the day of surgery; Group 2 included 20 patients (12 males and 8 females; 37.35 ± 11.5 years of age) who were postoperatively administered with topical basic fibroblast growth factor (bFGF; 10 μg/10 μL) four times a day for 7 days plus oral l-cysteine supplementation (500 mg/capsule) once a day for 15 days, starting 7 days before PRK. Patients were followed-up for 12 months. Clinical ophthalmologic parameters were recorded for all the 80 examined eyes. The corneal transparency was evaluated in vivo by slit lamp and confocal microscopy. The data showed that: (a) the corneal haze occurred in a smaller percentage of the patients who were postoperatively administered with topical bFGF plus oral l-cysteine supplementation (Group 2) compared to patients who received only bFGF (Group 1); (b) at 6 months of follow-up, the stromal mean image brightness of the patients belonging to Group 2 was significantly lower than that of the Group 1 (p < 0.03), and, interestingly, the difference was even more evident at 12 month from the treatment (p < 0.001). Moreover, the final mean of the spherical equivalent refraction was −0.06 ± 0.2 D in Group 1 and −0.08 ± 0.3 D in Group 2, whereas the final uncorrected distance visual acuity (UDVA) was equal or superior to 20/25 in 100% of eyes in both Group 1 and 2. Post refractive patients can benefit from the administration of l-cysteine before the surgery and in association with bFGF in the early postoperative period, showing a faster corneal re-epithelization able to prevent corneal haze in the long-term recovery.
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Del Villar, Ignacio, Abian B. Socorro, Miguel Hernaez, Jesús M. Corres, Carlos R. Zamarreño, Pedro Sanchez, Francisco J. Arregui, and Ignacio R. Matias. "Sensors Based on Thin-Film Coated Cladding Removed Multimode Optical Fiber and Single-Mode Multimode Single-Mode Fiber: A Comparative Study." Journal of Sensors 2015 (2015): 1–7. http://dx.doi.org/10.1155/2015/763762.
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Two simple optical fibre structures that do not require the inscription of a grating, a cladding removed multimode optical fibre (CRMOF) and a single-mode multimode single-mode structure (SMS), are compared in terms of their adequateness for sensing once they are coated with thin-films. The thin-film deposited (TiO2/PSS) permits increasing the sensitivity to surrounding medium refractive index. The results obtained can be extrapolated to other fields such as biological or chemical sensing just by replacing the thin-film by a specific material.
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DAESCHEL, MARK A., JOSEPH MCGUIRE, and HAMOOD AL-MAKHLAFI. "Antimicrobial Activity of Nisin Adsorbed to Hydrophilic and Hydrophobic Silicon Surfaces." Journal of Food Protection 55, no. 9 (September 1, 1992): 731–35. http://dx.doi.org/10.4315/0362-028x-55.9.731.
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The antimicrobial activity of nisin was studied after its adsorption to hydrophilic and hydrophobic silicon surfaces. Adsorption was allowed to occur from buffered nisin solutions under static conditions, and the adsorbed mass of nisin was calculated from the resultant film thickness and refractive index, determined using ellipsometry. Once adsorbed, nisin was observed to be stable to buffer rinsing; the amount of nisin adsorbed onto each type of surface was determined to be of a quantity sufficent for inhibition of susceptible bacteria. Antimicrobial activity was maintained both upon silicon surface contact with microbial media and after nisin desorption induced by surfactant displacement.
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Mejía Barbosa, Yobani. "La prueba de Hartmann en ciencias de la visión." Ciencia & Tecnología para la Salud Visual y Ocular 10, no. 1 (July 12, 2012): 149. http://dx.doi.org/10.19052/sv.104.
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En este artículo se muestran tres aplicaciones de la prueba de Hartmann en Ciencias de la Visión, desarrolladas en el laboratorio de diseño óptico del Departamento de Física de la Universidad Nacional de Colombia: lensómetro para lentes de adición progresiva, topógrafo corneal y aberrómetro tipo Hartmann-Shack. Primero se describe brevemente la prueba clásica de Hartmann para espejos astronómicos y luego se presentan tres variaciones de la prueba de Hartmann para optometría yoftalmología. En cada caso se describe el sistema óptico empleado y la geometría para deducir la aberración de frente de onda a partir de las aberraciones de rayo (patrones de Hartmann). En los tres casos se obtienen relaciones matemáticas similares, por lo que el frente de onda se puede determinar en cada caso empleando el mismo método de integración. Posteriormente, se calculan las cantidades de interés, a saber: en lensometría, los mapas de potencia refractiva cilíndrica y esférica; en topografía, el mapa de curvatura tangencial; y en aberrometría, el mapa de elevación de frente de onda y la psf. Finalmente, se hace un breve comentario sobre la implementación de la prueba de Hartmann por parte de algunas compañías comerciales.
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Nogueira, Pedro Vencovsky, Marcelo Peres Rocha, Welitom Rodrigues Borges, Eduardo Xavier Seimetz, and Márcio Maciel Cavalcanti. "COMPARISON BETWEEN RESULTS OF SEISMIC REFRACTION AND STANDARD PENETRATION TEST (SPT) TO STUDY SHALLOW GEOLOGICAL SUBSURFACE IN AN URBAN AREA OF BRASÍLIA, BRAZIL." Revista Brasileira de Geofísica 32, no. 4 (December 1, 2014): 673. http://dx.doi.org/10.22564/rbgf.v32i4.536.
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ABSTRACT. The most common procedure for an engineering project/construction is the use of direct survey, borehole and Standard Penetration Test (SPT). Thisprovides punctual information of the geology at the site, and many boreholes are necessary along the construction site, representing a significant amount of the budgetfor the construction and to help develop a better geological understand/map of the site. The use of geophysical methods allows to study the subsurface by indirectmeans, with low cost, and enable to cover large areas if compared to direct surveys. Geophysical methods are increasingly being used in engineering works, however, inBrazil the use in engineering projects is still scarce. In this work was used shallow seismic refraction method to study the shallow subsurface in an area along the futuretrack of the subway system of Bras´ılia, Brazil. The refraction results (P-wave) were compared with previous existing data from Standard Penetration Test (SPT), and soilprofile description. The seismic was used to study the subsurface geology, and SPT data were used to compare the seismic results. We observed a good correlationfor the depths obtained through each method, mostly in the north portion of the line, when the SPT was near the line, indicating that its results are influenced by thesame mechanical parameters, related to soil strength. Our results motivate the use of seismic refraction as a tool to optimize the direct investigation methods for bettergeotechnical characterization of the medium.Keywords: shallow seismic refraction, standard penetration test (SPT), geotechnical study. RESUMO. O procedimento inicial mais comum em um projeto de engenharia é o uso de pesquisa direta, por meio de sondagens e Índice de Resistência à Penetração (SPT, em inglês). Estas ferramentas fornecem informações pontuais acerca da geologia local, sendo necessárias diversas sondagens para desenvolver um bom entendimento geológico/geotécnico da região, fazendo com que as sondagens representem uma quantidade significativa do orçamento da obra de engenharia. O usode métodos geofísicos permite estudar a subsuperfície por meio indireto, com baixo custo, e possibilita cobrir grandes áreas, quando comparado ao uso exclusivo desondagens diretas. Métodos geofísicos estão sendo cada vez mais utilizados em obras de engenharia, no entanto, o seu uso em projetos de engenharia no Brasil aindaé escasso. Neste trabalho foi utilizado o método de sísmica de refração rasa para estudar a subsuperfície em uma área ao longo do futuro trecho do sistema de metrô de Brasília, Brasil. Os resultados de refração (onda P) foram comparados com os dados pré-existentes de SPT e descrição do solo. A sísmica foi empregada para estudara geologia da subsuperfície, os dados SPT foram utilizados para comparar com os resultados sísmicos. Observou-se uma boa correlação para as profundezas obtidas através de cada método, principalmente na porção norte da linha, região em que o SPT está mais próximo da linha, indicando que os seus resultados são influenciados pelos mesmos parâmetros mecânicos, relacionados com a resistência do solo. Nossos resultados motivam o uso de refração sísmica como uma ferramenta para aperfeiçoar os métodos de investigação direta, com objetivo de gerar uma melhor caracterização geotécnica do meio.Palavras-chave: sísmica de refração rasa, índice de resistência à penetração, estudo geotécnico.
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Varsamis, Christos-Platon E. "Determination of the Complex Refractive Index of Materials via Infrared Measurements." Applied Spectroscopy 56, no. 8 (August 2002): 1107–13. http://dx.doi.org/10.1366/000370202760249873.
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In this work, methods are presented for obtaining the real, n, and imaginary, k, parts of the complex refractive index of materials considered as semi-infinite and finite from infrared reflectance, R( ν), and/or transmittance, T( ν), spectra. In semi-infinite samples, with negligible T( ν), only R( ν) is measured, and n and k can derive from the Kramers–Kronig (K–K) transformation or the modeling of the dielectric function of the material. In finite samples, the interference fringes due to multiple internal reflections can significantly alter the measured spectra. It was demonstrated that whenever the period of the fringes is on the order of a few cm−1, n and k can be equivalently obtained by the extended K–K analysis for T( ν) spectra, the modeling of the dielectric function, and the inversion of low-resolution R( ν) and T( ν) spectra, as well as the acquisition of a single high-resolution R( ν) or T( ν) spectrum. Otherwise, n and k can be calculated by modeling the dielectric function of the material once the optical effects are carefully removed. These methods were applied in infrared measurements of crystalline Si wafer and of glassy 0.20AgI·0.80[Ag2O·2B2O3].
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Kim, Yong Woo, and Ki Ho Park. "Exogenous influences on intraocular pressure." British Journal of Ophthalmology 103, no. 9 (March 25, 2019): 1209–16. http://dx.doi.org/10.1136/bjophthalmol-2018-313381.
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Intraocular pressure (IOP), the pressure within the eyeball, is a function mainly of the production and elimination of aqueous humour. Balanced IOP helps to maintain the eyeball contour, allowing proper refraction of light in the anterior segment of the eye. Increases in IOP can cause injury to the ocular structure, typically the optic nerve head and retinal ganglion cells. IOP increase, additionally, is a risk factor for glaucoma progression. However, it is not unusual that glaucoma worsens despite well-managed IOP; indeed, glaucoma can develop and progress even within the normal IOP range. IOP measured once during daytime office hours might not provide sufficient information for effective glaucoma management. In fact, IOP is not a fixed value but rather changes over time: it fluctuates with the intrinsic circadian rhythm and can also change in various lifestyle-related situations (eg, with body posture, during exercise, while holding breath and according to dietary habits). It is therefore worth exploring the various factors that can affect IOP and glaucoma risk. In this review, the various exogenous influences on IOP in the literature are investigated.
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Revel, Jean-Paul. "Evolution and Revolution in Microscopy - II." Microscopy Today 1, no. 1 (February 1993): 2–3. http://dx.doi.org/10.1017/s1551929500066359.
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While today a picture of a serious looking person peering into a microscope may suggest “science” to the general public, we noted in our last column that this was not always so. In the early 19th century, for example, the microscope was seen by many as a hobby, interesting yes, but not as worthy of respect as an amateur's telescope.Microscopes improved and soon, through the insight of the likes of Ernst Abbe, reached a state of perfection which was not greatly improved upon until recently. Once aberrations were well corrected for and glasses of high refractive index commonly utilized, further improvements in numerical aperture became increasingly difficult to receive. The only way to improve resolution seemed to be to decrease the wavelength of light used to illuminate the sample.
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Lacarrubba, Francesco, Anna Elisa Verzì, Sebastiano Barresi, and Giuseppe Micali. "Multiple xanthogranulomas in an adult patient: clinical, dermoscopic, reflectance confocal microscopy and histopathological features." BMJ Case Reports 12, no. 7 (July 2019): e229772. http://dx.doi.org/10.1136/bcr-2019-229772.
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A case of multiple xanthogranulomas located bilaterally on arms, armpits, legs, trunk, abdomen, scalp, neck and plantar surfaces in a 25-year-old man is reported. The patient was evaluated by polarised light dermoscopy and reflectance confocal microscopy (RCM) that showed peculiar aspects. In particular, dermoscopy showed a homogeneous orange-yellowish hue that is related to the histopathological presence of foamy histiocytes and Touton giant cells; the last typically appeared at RCM as peculiar giant cells surrounded by highly refractive ring due to the cytoplasm rich of lipids. Laboratory investigations, including routine haematological examination, liver and renal function tests, serum lipid and sugar levels were normal. The patient started isotretinoin 20 mg once daily. After 6 months, some lesions flattened, leading to yellowish or hyperpigmented macules, but new lesions raised up.
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Qin, Zhongya, Congping Chen, Sicong He, Ye Wang, Kam Fai Tam, Nancy Y. Ip, and Jianan Y. Qu. "Adaptive optics two-photon endomicroscopy enables deep-brain imaging at synaptic resolution over large volumes." Science Advances 6, no. 40 (September 2020): eabc6521. http://dx.doi.org/10.1126/sciadv.abc6521.
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Optical deep-brain imaging in vivo at high resolution has remained a great challenge over the decades. Two-photon endomicroscopy provides a minimally invasive approach to image buried brain structures, once it is integrated with a gradient refractive index (GRIN) lens embedded in the brain. However, its imaging resolution and field of view are compromised by the intrinsic aberrations of the GRIN lens. Here, we develop a two-photon endomicroscopy by adding adaptive optics based on direct wavefront sensing, which enables recovery of diffraction-limited resolution in deep-brain imaging. A new precompensation strategy plays a critical role to correct aberrations over large volumes and achieve rapid random-access multiplane imaging. We investigate the neuronal plasticity in the hippocampus, a critical deep brain structure, and reveal the relationship between the somatic and dendritic activity of pyramidal neurons.
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Ross-Pinnock, David, and Glen Mullineux. "Thermal compensation using the hybrid metrology approach compared to traditional scaling." Proceedings of the Institution of Mechanical Engineers, Part B: Journal of Engineering Manufacture 232, no. 13 (October 10, 2017): 2364–74. http://dx.doi.org/10.1177/0954405417733766.
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Control of temperature in large-scale manufacturing environments is not always practical or economical, introducing thermal effects including variation in ambient refractive index and thermal expansion. Thermal expansion is one of the largest contributors to measurement uncertainty; however, temperature distributions are not widely measured. Uncertainties can also be introduced in scaling to standard temperature. For more complex temperature distributions with non-linear temperature gradients, uniform scaling is unrealistic. Deformations have been measured photogrammetrically in two thermally challenging scenarios with localised heating. Extended temperature measurement has been tested with finite element analysis to assess a compensation methodology for coordinate measurement. This has been compared to commonly used uniform scaling and has outperformed this with a highly simplified finite element analysis simulation in scaling a number of coordinates at once. This work highlighted the need for focus on reproducible temperature measurement for dimensional measurement in non-standard environments.
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PIOVELLA, N., R. BACHELARD, and PH W. COURTEILLE. "Fluid description of the cooperative scattering of light by spherical atomic clouds." Journal of Plasma Physics 79, no. 4 (March 14, 2013): 413–19. http://dx.doi.org/10.1017/s0022377813000275.
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AbstractWhen a cold atomic gas is illuminated by a quasi-resonant laser beam, light-induced dipole–dipole correlations make the scattering of light a cooperative process. Once a fluid description is adopted for the atoms, many scattering properties are captured by the definition of a complex refractive index. The solution of the scattering problem is here presented for spherical atomic clouds of arbitrary density profiles, such as parabolic densities characteristic of ultra-cold clouds. A new solution for clouds with infinite boundaries is derived, which is particularly useful for the Gaussian densities of thermal atomic clouds. The presence of Mie resonances, a signature of the cloud acting as a cavity for the light, is discussed. These resonances leave their fingerprint in various observables such as the scattered intensity or in the radiation pressure force, and can be observed by tuning the frequency of the incident laser field or the atom number.
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Izquierdo, Luis, Josefina A. Mejías Smith, Jose R. Lievano, Ramón Sarquis, and Maria A. Henriquez. "Modification of the Intrastromal Ring Position according to Postimplant Visual and Refractive Failure: Report of Two Cases." Case Reports in Ophthalmological Medicine 2019 (June 4, 2019): 1–5. http://dx.doi.org/10.1155/2019/7151849.
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Objective. The following report presents the adaptation of an existing technique of intrastromal corneal ring (ICRS) implantation enabling repositioning of the ring position postoperatively to manage a refractive failure in two patients with keratoconus. Methods. In two cases, KeraRing and Ferrara nomograms had suggested different ring positions. To manage with the differences between the two nomograms, a longer corneal tunnel was created followed by the classic intervention to move the ring through the initial intrastromal corneal tunnel according to the topographic values. Once the first ring position has failed, the ring segment was repositioned along the longer corneal tunnel according to the postoperative outcome. Results. Significant improvement in both cases was observed in the best corrected visual acuity (BCVA), uncorrected visual acuity (UCVA), and root mean square (RMS) measured with Scheimpflug imaging (Pentacam; Oculus GmBH, Wetzlar, Germany). The participants were followed for one year. Conclusion. In patients with keratoconus which exhibit significant differences between KeraRing and Ferrara nomograms, a longer tunnel should be created to enable repositioning of the ring postoperatively if necessary, to avoid extracting the ring or changing it.
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Tomás-Juan, Javier. "Variables y parámetros influyentes en los perfiles de ablación del láser de excímeros." Ciencia & Tecnología para la Salud Visual y Ocular 12, no. 1 (June 1, 2014): 117. http://dx.doi.org/10.19052/sv.2515.
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<p>El láser de excímeros permite corregir los errores refractivos miópicos, astigmáticos e hipermetrópicos mediante la ablación de la superficie corneal. Para conseguir el mejor tratamiento y la mejor corrección visual postoperatoria es necesario un buen mantenimiento y calibración de todos los parámetros del láser y de los factores ambientales de la sala de quirófano. Después de la cirugía en algunas situaciones se produce un incremento de las aberraciones, las cuales afectan en gran medida a la calidad visual del paciente. En la actualidad nuevos dispositivos basados en la ablación guiada por frente de onda y la ablación topográfica se han introducido con el objetivo de disminuir las aberraciones postoperatorias. En el presente trabajo se realiza un análisis de los principales parámetros del láser de excímeros que influyen en la ablación, como los diferentes perfiles de ablaciones corneales, que muestran cómo se relacionan directamente con la calidad visual posquirúrgica.</p><p> </p>
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Shonkoff, Sam Berrin. "Metanomianism and Religious Praxis in Martin Buber’s Hasidic Tales." Religions 9, no. 12 (December 4, 2018): 399. http://dx.doi.org/10.3390/rel9120399.
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It is well known that Martin Buber abandoned Jewish law as a binding code. Scholars have identified him accurately as a religious anarchist, and his perspective is best characterized as metanomian—that is, one that locates the essence of religiosity outside of any fixed system, without necessarily opposing that system as a matter of principle. And yet, such general characterizations offer only a very vague picture of Buber’s stance. This paper demonstrates that it is especially illustrative for us to turn to Buber’s Hasidic tales. First of all, precisely because Buber’s concept of practice was irreducible to any static system or code, the genre of narrative conveys far more than any abstract formulation can. Moreover, inasmuch as Buber’s Hasidic tales were his own hermeneutical refractions of earlier sources, which were in themselves teeming with images of practice, our intertextual investigations reveal at once narrative representations of religious life and Buber’s personal interpretations of those narratives. What emerges from this study, then, is a textured and vivid vision of religious practice, which was not merely a peripheral concern but a life-encompassing core of Buber’s thought.
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Coultrip, Robert L. "High-accuracy wavefront tracing traveltime calculation." GEOPHYSICS 58, no. 2 (February 1, 1993): 284–92. http://dx.doi.org/10.1190/1.58020284.1.
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Conventional ray-tracing algorithms for first-arrival calculation suffer from drawbacks such as (1) no guarantee of finding the globally minimum traveltime path when multiple paths exist, (2) shadow zones, and (3) trouble finding minimum traveltime paths containing refraction and/or diffraction energy. Algorithms that trace wavefronts circumvent these problems. The new wavefront-tracing algorithm presented here is based on an earth model consisting of uniform-velocity triangular cells with nodes placed at vertices and along cell edges. Nodes are places where traces of first arrival wavefronts (propagation directions and arrival times) are stored. The algorithm works by propagating wavefronts (sampled at the nodes) away from the source throughout the entire model. Wavefronts are propagated locally as diffraction, direct arrival, or critically refracted energy that implicitly describe minimum time paths. Once the first arrival wavefront is sampled throughout the model, traveltimes and raypaths from the source to receivers are easily calculated. This algorithm computes the globally minimum time paths from the source to all points in the model regardless of model complexity and the number of locally minimum traveltime paths. Traveltime calculations are highly accurate and computation time is O(n log2 n) for n nodes. Use of triangular cells allows for cell boundaries that follow, say, fault planes and dipping beds, without resorting to stair-step approximations inherent with rectangular cells. This method can be extended to three dimensional (3-D) problems.
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Pechprasarn, Suejit, Phitsini Suvarnaphaet, and Naphat Albutt. "Matching Impedances Fresnel Equations Calculation for Layered Optical Structures." Applied Mechanics and Materials 891 (May 2019): 292–98. http://dx.doi.org/10.4028/www.scientific.net/amm.891.292.
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In this paper, we demonstrate that Fresnel equations simulation for multilayer optical structures can be speeded up using impedance matching together with run once use many times concept as an optical responses database. The Fresnel equations can be solved by calculating reflection coefficient and transmission coefficient for each interface of the simulated structure and propagate the reflected waves and transmitted waves through the incident medium or the exiting medium using either scattering matrix approach or transfer matrix approach. If the structure parameter changes, such as, thickness of a layer in the structure change or the sequence of the layer changes, these require another set of Fresnel equations calculation. Here each of the layers are calculated separately with two semi-infinite layers with a fixed refractive index value sandwiched the two sides of the simulated layer. The reflection coefficient and the transmission coefficient for each layer can be then stored as a layer database. Different databases can be cascaded in any layer order to calculate a reflection or transmission responses of the layered structure.
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Killeen, Amanda L., Kara M. Brock, James F. Dancho, and Jodi L. Walters. "Remote Temperature Monitoring in Patients With Visual Impairment Due to Diabetes Mellitus: A Proposed Improvement to Current Standard of Care for Prevention of Diabetic Foot Ulcers." Journal of Diabetes Science and Technology 14, no. 1 (May 23, 2019): 37–45. http://dx.doi.org/10.1177/1932296819848769.
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Background: Two debilitating sequelae of diabetes are foot ulcerations and vision impairing conditions including retinopathy, open-angle glaucoma, and cataracts. Current standard of care recommends daily visual screening of feet. Despite willingness, many patients are impeded by visual impairment. We investigate whether once-daily remote temperature monitoring can improve self-screening for patients at risk for diabetic foot complications. Methods: We followed four male veterans with diabetes mellitus, peripheral neuropathy, impaired visual acuity, and at least one other diabetes-related visual impairment in a high-risk podiatry clinic. Patients received a telemedicine remote temperature monitoring mat and instructed on proper daily use. Each patient developed a “hotspot,” defined as a 1.75°C localized temperature difference between matched pedal locations, which resulted in telephone triage outreach. Results: In three cases, outreach resulted in a sooner appointment where patients were found to have a relevant outcome at the hotspot. Patients in cases 1-3 had University of Texas (UT) 1A ulcerations. The patient in case 4 had inflammation from trauma. All patients had refractive errors plus another vision impairing condition that potentially delayed identification of lesions. Patients in cases 1 and 2 have cataracts, patients in cases 2 and 3 have retinopathy, and patient in case 4 has glaucoma. Conclusions: As an adjunct to daily preventative diabetic self-care, once-daily remote temperature monitoring technology can augment self-screening to prompt necessary outreach and treatment and potentially prevent costly and debilitating diabetic foot complications. This case series serves as a pilot study for real-world application of thermometry, where further large-scale research is needed.
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Robinson, Jennifer, Manca Tekavčič Pompe, and Christina Gerth-Kahlert. "Challenges in Patients with Trisomy 21: A Review of Current Knowledge and Recommendations." Journal of Ophthalmology 2021 (May 26, 2021): 1–7. http://dx.doi.org/10.1155/2021/8870680.
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Purpose. To summarize and review the common ophthalmic anomalies in children with trisomy 21 (Down syndrome) in order to propose an update to current clinical recommendations. Methods. A retrospective chart review, systemic literature review, and international survey of the frequency of ocular abnormalities, screening schedules, and challenging aspects examining children with trisomy 21. The chart review included patients treated at the Department of Ophthalmology at the University Hospital of Zurich over a two-year period. The international survey was submitted to the members of the Swiss Society of Ophthalmology, Slovenian Ophthalmological Society, and European Pediatric Ophthalmology Society. Results. Analysis of 52 patient records during the study period revealed refractive errors (astigmatism: 54% of patients, hyperopia: 26%, and myopia: 15%) as the most common diagnosis, whereas childhood cataract was reported in 5%. This is in concordance with the extended literature review of 249 publications, although congenital cataracts were reported to be higher than at our institution. The survey participants reported great challenges in taking care of these patients, despite their long professional experience (73% with over 10 years of experience). Conclusion. Care and treatment of children with trisomy 21 continues to be demanding for paediatric ophthalmologists. We recommend the following examination schedule for these patients: first, ophthalmological examination at 6–12 months of age, then once in 3–6 months for children under 2 years of age, once in 6 months for children 2–5 years of age, annually for children 5–10 years of age, and thereafter, to be decided on an individual basis depending on the presenting ocular abnormalities of the patient.
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Giles, N. C., and L. E. Halliburton. "Native Defects in the Ternary Chalcopyrites." MRS Bulletin 23, no. 7 (July 1998): 37–40. http://dx.doi.org/10.1557/s0883769400029079.
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Ternary-chalcopyrite crystals contain a variety of point defects—the most common of which are vacancies, antisite ions, and impurities. Usually these defects are isolated, but they can also appear as complexes involving two or more of the simple defects. Depending on the material, the concentrations of these defects may vary from a few hundred parts per billion to a few hundred parts per million. Many of the point defects in the ternary chalcopyrites have associated optical-absorption bands with significant oscillator strengths. It is these absorption features that become important when the crystals are exposed to intense laser beams during device operation. Even a small amount of absorption will seriously degrade the performance of the device if any of the wavelengths of the various propagating beams happen to overlap an absorption band. This phenomenon can be a problem for both second-harmonic-generator and optical-parametric-oscillator applications. In general the absorption leads to heating of the crystal and results in-thermal lensing (due to temperature dependence of the index of refraction) and dephasing of the beams, and it can ultimately lead to thermal fracturing of the crystal. Thus it is important to develop a fundamental understanding of the defect structure of the ternary-chalcopyrite crystals if they are to serve as the critical component in midinfrared frequency-conversion devices. Once the nature and behavior of the point defects are established, processes can be developed to remove the defects from the crystals either during the growth itself or during post-growth treatments.
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Hanne, Detlef, Nicky White, Andrew Butler, and Stephen Jones. "Phanerozoic vertical motions of Hudson Bay." Canadian Journal of Earth Sciences 41, no. 10 (October 1, 2004): 1181–200. http://dx.doi.org/10.1139/e04-047.
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We analyze the sedimentary record of the Hudson Bay basin, an intracratonic basin which is widely believed to have been formed by convective downwelling within the mantle. This belief largely stems from the coincidence of a long-wavelength negative gravity anomaly and an approximately circular basin which is filled with about 2 km of predominantly Paleozoic sedimentary rocks. Our starting point is a set of wells and seismic reflection profiles which demonstrate that the basin subsided rapidly from Ordovician to Devonian times. One- and two-dimensional subsidence modeling show that water-loaded subsidence occurred in two stages and is too rapid to be accounted for by thermal contraction alone. Instead, we suggest that basin subsidence is consistent with minor phases of lithospheric thinning which occurred during OrdovicianSilurian and EarlyMiddle Devonian times. Stretching factors for these minor extensional episodes vary from 1.05 to 1.2 with vertical strain rates of 210 Ga1. Our interpretation of the subsidence record is corroborated by limited evidence for syn-rift normal faulting and crustal thinning inferred from legacy seismic reflection and refraction data sets. Subsidence modelling also suggests that about 1 km of expected thermal subsidence is missing. This discrepancy suggests that the basin was uplifted and denuded at least once, but possibly several times, between Late Devonian and Middle Cretaceous times (i.e., 360100 Ma) and between Cretaceous and Quaternary times. We conclude that the Hudson Bay basin was not generated by convective downwelling that initiated in Paleozoic times and that remained coupled to the lithospheric plate.
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García-Medina, Gabriel, H. Tuba Özkan-Haller, Peter Ruggiero, and Jeffrey Oskamp. "An Inner-Shelf Wave Forecasting System for the U.S. Pacific Northwest." Weather and Forecasting 28, no. 3 (June 1, 2013): 681–703. http://dx.doi.org/10.1175/waf-d-12-00055.1.
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Abstract An operational inner-shelf wave forecasting system was implemented for the Oregon and southwest Washington coast in the U.S. Pacific Northwest (PNW). High-resolution wave forecasts are useful for navigational planning, identifying wave energy resources, providing information for site-specific coastal flood models, and having an informed recreational beach user group, among other things. This forecasting model is run once a day at 1200 UTC producing 84-h forecasts. A series of nested grids with increasing resolution shoreward are implemented to achieve a 30-arc-second resolution at the shelf level. This resolution is significantly higher than what the current operational models produce, thus improving the ability to quantify the alongshore variations of wave conditions on the PNW coast. Normalized root-mean-squared errors in significant wave height and mean wave period range from 0.13 to 0.24 and from 0.13 to 0.26, respectively. Visualization of the forecasts is made available online and is presently being used by recreational beach users and the scientific community. A series of simulations, taking advantage of having a validated shelf-scale numerical wave model, suggests that neither dissipation due to bottom friction nor wind generation is important in the region at this scale for wave forecasting and hindcasting when considering bulk parameters as opposed to the processes of refraction and shoaling. The Astoria and McArthur Canyons; the Stonewall, Perpetua, and Heceta Banks; and Cape Blanco are significant bathymetric features that are shown to be capable of producing alongshore variability of wave heights on the shelf.
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Centeno-Salas, F. A., D. Carreón-Freyre, W. A. Flores-García, and R. I. Gutiérrez-Calderón. "Application of high resolution geophysical prospecting to assess the risk related to subsurface deformationin Mexico City." Proceedings of the International Association of Hydrological Sciences 372 (November 12, 2015): 267–72. http://dx.doi.org/10.5194/piahs-372-267-2015.
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Abstract. In the eastern sector of Mexico City the sub soil consists of high contrasting sequences (lacustrine and volcanic inter bedded deposits) that favor the development of erratic fracturing in the surface causing damage to the urban infrastructure. The high-resolution geophysical prospecting are useful tools for the assessment of ground deformation and fracturing associated with land subsidence phenomena. The GPR method allowed to evaluate the fracture propagation and deformation of vulcano-sedimentary sequences at different depths, the main electrical parameters are directly related with the gravimetric and volumetric water content and therefore with the plasticity of the near surface prospected sequences. The active seismology prospection consisted in a combination of Seismic Refraction (SR) and Multichannel Analysis of Surface Waves (MASW) for the estimation of the velocity of the mechanical compressive (P) and the shear (S) waves. The integration of both methods allowed to estimate the geomechanical parameters characterizing the studied sequence, the Poisson Ratio and the volumetric compressibility. The obtained mechanical parameters were correlated with laboratory measured parameters such as plasticity index, density, shear strength and compressibility and, GPR and seismic profiles were correlated with the mapped fracture systems in the study area. Once calibrated, the profiles allowed to identify the lithological contact between lacustrine and volcanic sequences, their variations of thicknesses in depth and to assess the deformation area in the surface. An accurate determination of the geometry of fracturing was of the most importance for the assessment of the geological risk in the study area.
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Farooq, Mashhood-uz-Zafar, Shama Mashhood, Sana Adeeba Islam, Raffat Rasool, Mahmood Akhter Rana, Syed Safdar Zamir Rizvi, and Muhammad Faisal Fahim. "Myopia: Efficacy of 1% Atropine in Retarding Progression." Chinese Journal of Medical Research 3, no. 4 (December 25, 2020): 114–18. http://dx.doi.org/10.37515/cjmr.091x.3406.
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Purpose: To determine the efficacy of 1% atropine eye drops in control of myopia progression. Methods: This was a Case control study, conducted at the Mohsin Family Health Clinic, Block-16, Federal B Area, Karachi, during January 2018 to December 2019. A total of 194 (97 cases and 97 controls) cases were included in the study by the calculation of online software openepi.com. The Treatment Group was given 1% atropine eye drops while Control Group received no treatment. The follow-up of all the cases was carried out according to the follow-up schedule for a total period of one year. All the demographic data, clinical findings and the follow-up results were recorded on a proforma designed for the study, and the results were tabulated. Results: A total of 194 children age 6-15 with best corrected visual acuity 6/6 were recruited in this study. Half of the children were included in treatment group who received once a day application of 1% atropine eye drops at bedtime. The other half received no treatment and were taken as control group. Mean spherical equivalent refraction (SER) at baseline was 2.93±0.69 of Treatment Group and 2.98±0.61 of control group with insignificant P-value of 0.461. After 1-year treatment statistically significant difference with P-value 0.001, was observed with SER 3.37±0.91 in Treatment Group and 3.69±0.94 in control group. Conclusion: Atropine 1% eye drops is well tolerated and is found efficacious in controlling myopia progression.
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Ortega Pacific, Ernesto J. "Adaptación de lentes de contacto rígidos esféricos con base en topografía corneal en pacientes con córneas irregulares inducidas por cirugía refractiva." Ciencia & Tecnología para la Salud Visual y Ocular 7, no. 2 (December 1, 2009): 49–56. http://dx.doi.org/10.19052/sv.1058.
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Propósito: desarrollar un método para la determinación del lente de contacto rígido esférico de prueba, con base en la topografía corneal, en pacientes con corneas irregulares poscirugía refractiva tipo Lasik y queratoplastia penetrante. Metodología: Se realizaron adaptaciones de lentes rígidos esféricos en treinta pacientes. Determinando el lente prueba, observando áreas especificas de la topografía corneal y utilizando esa misma curvatura, se realizaron modificaciones con base en el fluorograma en varios controles y se relacionaron los parámetros finales de lentes entregados y la topografía corneal. Resultados: se realizaron treinta adaptaciones en pacientes posquirúrgicos: diecinueve de Lasik y once con queratoplastia penetrante. Se logró exitosa adaptación, con más de ocho horas de uso continuo, en el 94,7% de Lasik y en el 90,9 % de las queratoplastias. Conclusiones: si determinamos, con base en la topografía corneal, la curvatura promedio encontrada a 3 milímetros temporal y nasal y ligeramente superior, podemos seleccionar como lente de prueba uno con igual valor de curvatura de diseño esférico. Este diseño, combinado con zonas ópticas mayores de 8 mm y diámetros totales promedios de 10 mm, con un adecuado análisis del fluorograma, ofrece muy buenos resultados en corneas irregulares posquirúrgicas de láser y queratoplastia.
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Al-Shaiji, Tariq F. "Dual Implantation of Artificial Urinary Sphincter and Inflatable Penile Prostheses for Concurrent Male Urinary Incontinence and Erectile Dysfunction." Advances in Urology 2011 (2011): 1–6. http://dx.doi.org/10.1155/2011/178312.
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Erectile dysfunction and urinary incontinence secondary to sphincter dysfunction are common conditions affecting many men worldwide with a negative effect on quality of life. They are encountered in a number of etiologies most commonly following radical prostatectomy in which they coexist in the same patient. Implantations of an artificial urinary sphincter and inflatable penile prosthesis have proven to be effective in the treatment of both conditions should conservative and minimally invasive measures fail. The recent literature has shown that dual implantation of these devices is feasible and safe with a durable clinical outcome. Once indicated, this can be done in a synchronous or nonsynchronous manner; however, the emerging of the single transverse scrotal incision as well as advancement in the prostheses has made synchronous dual implantation more favourable and appealing option. It provides time and cost savings with an evidence of high patient satisfaction. Synchronous dual implantation should be offered initially when indicated. This paper discusses the surgical techniques of artificial urinary sphincter and inflatable penile prosthesis dual implantation in the management of concurrent moderate-to-severe urinary incontinence and medically refractive erectile dysfunction, in addition to highlighting the existing literature pertaining to this approach.
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Stro¨ll, H., F. Durst, M. Peric´, J. C. F. Pereira, and G. Scheuerer. "Study of Laminar, Unsteady Piston-Cylinder Flows." Journal of Fluids Engineering 115, no. 4 (December 1, 1993): 687–93. http://dx.doi.org/10.1115/1.2910200.
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The present paper concerns numerical investigation of a piston-driven, axisymmetric flow in a pipe assembly containing a sudden expansion. The piston closes the larger of the two pipes. The impulsively starting intake flow is the topic of this investigation. Results of numerical calculations and laser-Doppler measurements are presented to provide an insight into the features of the flow. The calculation procedure employed in this study is based on a finite-volume method with staggered grids and SIMPLE-algorithm for pressure-velocity coupling (Patankar and Spalding, 1972). The convection and diffusion fluxes in the Navier-Stokes equations are discretized with first order upwind and second order central differences, respectively. A fully implicit Euler scheme is used to discretize the temporal derivatives. The Navier-Stokes equations were suitably transformed to allow prediction of the flow within the inlet pipe (fixed grid) and cylinder region (moving grid) simultaneously (once-through procedure). Laser-Doppler measurements of both axial and radial velocity components were performed. Refractive index matching was used to eliminate the wall curvature effects. For each measuring point 20 cycles were measured, showing high repetition rates. Comparison of measured and predicted velocity profiles shows good agreement.
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Rußler, Axel, Antje Potthast, Thomas Rosenau, Thomas Lange, Bodo Saake, Herbert Sixta, and Paul Kosma. "Determination of substituent distribution of viscoses by GPC." Holzforschung 60, no. 5 (August 1, 2006): 467–73. http://dx.doi.org/10.1515/hf.2006.077.
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Abstract Based on previous investigations on the substitution pattern of stabilized and fresh viscose, different viscoses were analyzed by gel permeation chromatography (GPC) with multiple-angle laser light scattering, refractive index (RI), and UV detection. Viscoses derivatized with N-methyl-N-phenyl-iodoacetanilide are stable over a long time and largely improve handling for analytical purposes. In addition, the derivatized xanthogenate groups exhibit UV absorbance that can be used to detect their distribution along the polymer molecule, once the polymer is dissolved. UV assay indicated that in technical viscoses the distribution of substituents is uniform. Enzymatic degradation with endoglucanases was followed by analysis of the degradation pattern by GPC. Even though the degree of substitution (DS) of xanthogenate groups ranged from γ=0.4 to 0.6, endoglucanases were able to slightly degrade the viscose. Ultrasonic degradation resulted in a narrow molecular weight distribution (MWD), notably without cleavage of substituents, and was also used to improve the solubility of the stabilized viscoses for further analysis. The techniques applied provide more insight into the xanthogenate distribution along the MWD. Remarkable differences in the degradation behavior of both viscose samples were observed.
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Fritz, Jason, and V. Chandrasekar. "Implementation and Analysis of Networked Radar Refractivity Retrieval." Journal of Atmospheric and Oceanic Technology 26, no. 10 (October 1, 2009): 2123–35. http://dx.doi.org/10.1175/2009jtecha1182.1.
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Abstract The surface-layer moisture field can be obtained by estimating the refractive index of air, measured in parts per million, and is referred to as refractivity. A technique to estimate the refractivity by using radar has been demonstrated experimentally using the measured change in phase from stationary ground targets. Recently, a new network-based algorithm was proposed within the Center for Collaborative Adaptive Sensing of the Atmosphere (CASA) as an alternative approach, especially when dealing with multiple radars. That work presented the algorithm and applied it to purely simulated data. The research presented here provides more detail and takes the new networked radar approach to the next level by independently validating and demonstrating the output with data collected during a refractivity field experiment in Colorado during the summer of 2006. The practical aspects of implementing the network-based algorithm are presented along with a more complete mathematical representation. The results are then compared with the previously fielded technique starting from the same filtered phase data. From this comparison, the authors conclude that the networked algorithm has potential for providing a good refractivity estimate from a radar network once some of its own shortcomings are addressed.
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Duivenvoorden, Adriaan J., Alexandre E. Adler, Matteo Billi, Nadia Dachlythra, and Jon E. Gudmundsson. "Probing frequency-dependent half-wave plate systematics for CMB experiments with full-sky beam convolution simulations." Monthly Notices of the Royal Astronomical Society 502, no. 3 (February 6, 2021): 4526–39. http://dx.doi.org/10.1093/mnras/stab317.
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ABSTRACT We study systematic effects from half-wave plates (HWPs) for cosmic microwave background (CMB) experiments using full-sky time-domain beam convolution simulations. Using an optical model for a fiducial spaceborne two-lens refractor telescope, we investigate how different HWP configurations optimized for dichroic detectors centred at 95 and 150 GHz impact the reconstruction of primordial B-mode polarization. We pay particular attention to possible biases arising from the interaction of frequency-dependent HWP non-idealities with polarized Galactic dust emission and the interaction between the HWP and the instrumental beam. To produce these simulations, we have extended the capabilities of the publicly available beamconv code. To our knowledge, we produce the first time-domain simulations that include both HWP non-idealities and realistic full-sky beam convolution. Our analysis shows how certain achromatic HWP configurations produce significant systematic polarization angle offsets that vary for sky components with different frequency dependence. Our analysis also demonstrates that once we account for interactions with HWPs, realistic beam models with non-negligible cross-polarization and sidelobes will cause significant B-mode residuals that will have to be extensively modelled in some cases.
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Hu, Hua-Liang, Ji-Wei Peng, and Chun-Ying Lee. "Dynamic Simulation of a Metamaterial Beam Consisting of Tunable Shape Memory Material Absorbers." Vibration 1, no. 1 (July 18, 2018): 81–92. http://dx.doi.org/10.3390/vibration1010007.
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Metamaterials are materials with an artificially tailored internal structure and unusual physical and mechanical properties such as a negative refraction coefficient, negative mass inertia, and negative modulus of elasticity, etc. Due to their unique characteristics, metamaterials possess great potential in engineering applications. This study aims to develop new acoustic metamaterials for applications in semi-active vibration isolation. For the proposed state-of-the-art structural configurations in metamaterials, the geometry and mass distribution of the crafted internal structure is employed to induce the local resonance inside the material. Therefore, a stopband in the dispersion curve can be created because of the energy gap. For conventional metamaterials, the stopband is fixed and unable to be adjusted in real-time once the design is completed. Although the metamaterial with distributed resonance characteristics has been proposed in the literature to extend its working stopband, the efficacy is usually compromised. In order to increase its adaptability to time-varying disturbance, several semi-active metamaterials have been proposed. In this study, the incorporation of a tunable shape memory alloy (SMA) into the configuration of metamaterial is proposed. The repeated resonance unit consisting of SMA beams is designed and its theoretical formulation for determining the dynamic characteristics is established. For more general application, the finite element model of this smart metamaterial is also derived and simulated. The stopband of this metamaterial beam with different configurations in the arrangement of the SMA absorbers was investigated. The result shows that the proposed model is able to predict the unique dynamic characteristics of this smart metamaterial beam. Moreover, the tunable stopband of the metamaterial beam with controlling the state of SMA absorbers was also demonstrated.
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Fatmawati, Riza, and Hammam Hammam. "Penanaman Akidah Melalui Pembiasaan Membaca Kitab Ta’limul Mubtadi’in Aqoid Ad-Diin di SD Negeri Kabupaten Tegal." Attractive : Innovative Education Journal 2, no. 1 (April 22, 2020): 49. http://dx.doi.org/10.51278/aj.v2i1.23.
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The aimed is to determine the strategy, implementation, evaluation as well as supporting and inhibiting factors of the cultivation of creed through the habit of reading the Book Ta'limul Mubtadiin fi Aqoid Ad-in state elementary school in Tegal Regency. This research was a descriptive qualitative research. The data in this study were obtained through interviews, observation and documentation. The results of this study indicate that, first, the strategies used in this habituation were of three kinds, 1) traditional strategies, namely for schools that carry out habituation once a week consisting of elementary school (SDN) Talang 01 and SDN Lawatan 01, 2) free strategy, namely for classroom students low (I, II and III) given the freedom to follow habituation and this applies to all schools, 3) internal trans strategy which was a school that conducts habituation every day, consisting of SDN Rancawiru 02, SDN Kepandean 01, SDN Kepandean 02, and SDN SDN Jenggawur Secondly, the implementation of the planting of faith through the habit of reading the Ta'limul Mubtadiin fi Aqoid Ad-In Book in Tegal Regency Elementary School, there are various who do it every morning in the school yard, there are also those who carry out PAI learning in class. Third, the evaluation includes evaluation of program plans (related to the purpose of planting creed through habituation), process evaluation (evaluation of problems that arise during habituation), and final evaluation (related to the attainment of refraction goals). Fourth, the supporting and inhibiting factors of the cultivation of the creed came from parents, students, teachers, the government of Tegal Regency and the editors of the book
Keywords: Cultivation, Faith, Habituation, Ta'limul Mubtadiin fi Aqoid Ad-In
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McCrann, Saoirse, Ian Flitcroft, Niall C. Strang, Kathryn J. Saunders, Nicola S. Logan, Samantha Szeyee Lee, David A. Mackey, John S. Butler, and James Loughman. "Myopia Outcome Study of Atropine in Children (MOSAIC): an investigator-led, double-masked, placebo-controlled, randomised clinical trial protocol." HRB Open Research 2 (July 23, 2019): 15. http://dx.doi.org/10.12688/hrbopenres.12914.1.
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Background: The Myopia Outcome Study of Atropine in Children (MOSAIC) aims to explore the efficacy, safety, acceptability and mechanisms of action of 0.01% unpreserved atropine for myopia control in a European population. Methods: MOSAIC is an investigator-led, double-masked, placebo-controlled, randomised clinical trial (RCT) investigating the efficacy, safety and mechanisms of action of 0.01% atropine for managing progression of myopia. During Phase 1 of the trial, 250 children aged 6-16 years with progressive myopia instil eye drops once nightly in both eyes from randomisation to month 24. No treatment is given during Phase 2 from month 24 to 36 (washout period) for those participants initially randomised to the intervention arm (n=167), during which any potential rebound effects on cessation of treatment will be monitored. All participants initially assigned to the placebo (n=83) crossover to the intervention arm of the study for Phase 2, and from month 24 to 36, instil 0.01% atropine eye drops in both eyes once nightly. Further treatment and monitoring beyond 36 months is planned (Phase 3) and will be designed dependent on the outcomes of Phase 1. Results: The primary outcome measure is cycloplegic spherical equivalent refractive error progression at 24 months. Secondary outcome measures include axial length change as well as the rebound, safety and acceptability profile of 0.01% atropine. Additional analyses will include the mechanisms of action of 0.01% atropine for myopia control. Conclusions: The generalisability of results from previous clinical trials investigating atropine for myopia control is limited by the predominantly Asian ethnicity of previous study populations. MOSAIC is the first RCT to explore the efficacy, safety and mechanisms of action of unpreserved 0.01% atropine in a predominantly White population. Trial registration: ISRCTN: ISRCTN36732601 (04/10/2017), EudraCTdatabase 2016-003340-37 (03/07/2018).
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McCrann, Saoirse, Ian Flitcroft, Niall C. Strang, Kathryn J. Saunders, Nicola S. Logan, Samantha Szeyee Lee, David A. Mackey, John S. Butler, and James Loughman. "Myopia Outcome Study of Atropine in Children (MOSAIC): an investigator-led, double-masked, placebo-controlled, randomised clinical trial protocol." HRB Open Research 2 (September 25, 2019): 15. http://dx.doi.org/10.12688/hrbopenres.12914.2.
Full textAbstract:
Background: The Myopia Outcome Study of Atropine in Children (MOSAIC) aims to explore the efficacy, safety, acceptability and mechanisms of action of 0.01% unpreserved atropine for myopia control in a European population. Methods: MOSAIC is an investigator-led, double-masked, placebo-controlled, randomised clinical trial (RCT) investigating the efficacy, safety and mechanisms of action of 0.01% atropine for managing progression of myopia. During Phase 1 of the trial, 250 children aged 6-16 years with progressive myopia instil eye drops once nightly in both eyes from randomisation to month 24. From month 24 to 36 participants are re-randomised in Phase 2 of the trial, into continued 0.01% atropine, and washout, at 1:1 ratio for those participants initially randomised to the intervention arm (n=167), during which any potential rebound effects on cessation of treatment will be monitored. All participants initially assigned to the placebo (n=83) crossover to the intervention arm of the study for Phase 2, and from month 24 to 36, instil 0.01% atropine eye drops in both eyes once nightly. Further treatment and monitoring beyond 36 months is planned (Phase 3) and will be designed dependent on the outcomes of Phase 1. Results: The primary outcome measure is cycloplegic spherical equivalent refractive error progression at 24 months. Secondary outcome measures include axial length change as well as the rebound, safety and acceptability profile of 0.01% atropine. Additional analyses will include the mechanisms of action of 0.01% atropine for myopia control. Conclusions: The generalisability of results from previous clinical trials investigating atropine for myopia control is limited by the predominantly Asian ethnicity of previous study populations. MOSAIC is the first RCT to explore the efficacy, safety and mechanisms of action of unpreserved 0.01% atropine in a predominantly White population.
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Abdel-Ghany, A. M., and I. M. Al-Helal. "Modeling Approach for Determining Equivalent Optical Constants of Plastic Shading Nets under Solar Radiation Conditions." Advances in Materials Science and Engineering 2012 (2012): 1–8. http://dx.doi.org/10.1155/2012/158067.
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The radiative properties of several plastic shading nets were measured under natural solar radiation conditions. We found that the plastic nets behave as homogeneous translucent materials (e.g., plastic film, plastic sheets, and glass). Based on this behavior, we suggest that it is possible to treat plastic nets as translucent materials and to characterize them with equivalent optical constants (i.e., equivalent refractive indexes,neq, and equivalent extinction coefficients,σeq). Here a physical model to determineneqandσeqof plastic nets was described in analogy to homogeneous translucent materials. We examined three groups of nets based on their color (black, black-green, and beige). Each group consisted of nets with four or five different porosities. Nets of each group had almost the same texture structure. For each group, we derived an equation forneqas a function of the net porosity and determined an average value forσeq. Once values ofneqandσeqwere determined, the solar radiative properties of a net could then be calculated fromneqandσeqfor any incident angle of solar beam radiation without the need of measurements. The present model was validated by comparing the calculated with the measured radiative properties of three nets at different incident angle of solar beam radiation. The calculated radiative properties reasonably agreed with measured values.
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LeBel, F., É. Ruiz, and F. Trochu. "Experimental study of saturation by visible light transmission in dual-scale fibrous reinforcements during composite manufacturing." Journal of Reinforced Plastics and Composites 36, no. 23 (August 29, 2017): 1693–711. http://dx.doi.org/10.1177/0731684417725187.
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A new in situ monitoring strategy is proposed to study void formation during real-time impregnation of dual-scale fibrous reinforcements in liquid composite molding. Void content data from burn-off tests are used to calibrate a refractive index matching approach based on two optical principles: Beer–Lambert and Fresnel laws. Once calibrated, this approach based on visible light transmission is used to study the impact of key process parameters on the saturation footprint of dual-scale fibrous reinforcements during and after mold filling. The injection parameters investigated are the flow front velocity, the pressure distribution inside the mold cavity, the bleeding flow rate, and the mold packing pressure. The experimental setup is a computer-assisted injection system and a transparent resin transfer molding mold is used to perform unidirectional injections. A vinyl ester resin is injected through E-glass bidirectional non-crimp fabrics under various manufacturing conditions. This investigation not only confirms the decreasing trend in void formation by mechanical entrapment of air with the decrease in impregnation velocity, as it converges toward the optimal impregnation conditions for this fibrous reinforcement reported in previous studies, but it also brings insights on void dissolution and transport in liquid composite molding.
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Cheng, Jih-Fei. ""El tabaco se ha mulato": Globalizing Race, Viruses, and Scientific Observation in the Late Nineteenth Century." Catalyst: Feminism, Theory, Technoscience 1, no. 1 (June 11, 2015): 1–41. http://dx.doi.org/10.28968/cftt.v1i1.28810.
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This article traces the earliest identified recorded descriptor for viral infection: the racialized Spanish expression "el tabaco se ha mulato" ("the tobacco has become mulatto"). The phrase appears in the late nineteenth-century travel writing of French colonial scientist Jules Crevaux, written as he journeyed through post-Spanish Independence Colombia and observed the demise of the once-thriving tobacco industry. I theorize the literary translations and visualizations, or what I call "visual translations," of the phrase across scientific and historical texts that cite Crevaux to track the refraction of racial, gender, and sexual discourses in virology. I argue that the phrase refers to the historically dispossessed Indigenous and Black subjects of the nascent Colombian republic and their resistance to subjection when forced to work the tobacco fields. The article historicizes virus discovery at the juncture between science, nation-building, global industrialization, and the disciplining of race and sex under the long shadow of Euro-American empire. Drawing upon Ed Cohen's concept of "viral paradox," Nayan Shah's notion of "strangerhood," and Mel Y. Chen's framework for thinking about "queer animacies," I deconstruct the visual, conceptual, and etymological roots of the phrase "el tabaco se ha mulato" to argue that the expression renders the virus as both "queer" and "strange" to the nation. The virus signifies the mulato subject as a stubborn challenge to racial hierarchies and to the host-guest-parasite relation, both of which are foundational to the social organization of the nation and polis. This signification insistently refuses the human/non-human binary that undergirds racial regimes and biological conceptions of life. In turn, I expand historical thinking about race, submit that pandemics result from global industrial resource extraction rather than merely poor hygiene, and offer a framework for "queer decolonizing."