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https://www.readbyqxmd.com/read/29348561/performance-analysis-of-an-adaptive-optics-system-for-free-space-optics-communication-through-atmospheric-turbulence
#1
Yukun Wang, Huanyu Xu, Dayu Li, Rui Wang, Chengbin Jin, Xianghui Yin, Shijie Gao, Quanquan Mu, Li Xuan, Zhaoliang Cao
The performance of free-space optics communication (FSOC) is greatly degraded by atmospheric turbulence. Adaptive optics (AO) is an effective method for attenuating the influence. In this paper, the influence of the spatial and temporal characteristics of turbulence on the performance of AO in a FSOC system is investigated. Based on the Greenwood frequency (GF) and the ratio of receiver aperture diameter to atmospheric coherent length (D/r 0 ), the relationship between FSOC performance (CE) and AO parameters (corrected Zernike modes number and bandwidth) is derived for the first time...
January 18, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29343459/differing-structural-properties-of-foods-affect-the-development-of-mandibular-control-and-muscle-coordination-in-infants-and-young-children
#2
Meg Simione, Chrystel Loret, Benjamin Le Révérend, Brian Richburg, Mirna Del Valle, Marc Adler, Mireille Moser, Jordan R Green
The development of chewing is an essential motor skill that is continually refined throughout early childhood. From a motor control perspective, the advancement of textures is dependent upon the fit between a child's oral anatomic and motor system and food properties. The purpose of this exploratory study is to identify age-related changes in chewing motor coordination and control and to determine if these changes are associated with the differing structural properties of solid foods, as well as to explore the role of explanatory variables such as the emergence of teeth and bite force...
January 14, 2018: Physiology & Behavior
https://www.readbyqxmd.com/read/29341698/general-linearized-theory-of-quantum-fluctuations-around-arbitrary-limit-cycles
#3
Carlos Navarrete-Benlloch, Talitha Weiss, Stefan Walter, Germán J de Valcárcel
The theory of Gaussian quantum fluctuations around classical steady states in nonlinear quantum-optical systems (also known as standard linearization) is a cornerstone for the analysis of such systems. Its simplicity, together with its accuracy far from critical points or situations where the nonlinearity reaches the strong coupling regime, has turned it into a widespread technique, being the first method of choice in most works on the subject. However, such a technique finds strong practical and conceptual complications when one tries to apply it to situations in which the classical long-time solution is time dependent, a most prominent example being spontaneous limit-cycle formation...
September 29, 2017: Physical Review Letters
https://www.readbyqxmd.com/read/29341467/optoacoustic-sensing-of-hematocrit-to-improve-the-accuracy-of-hybrid-fluorescence-ultrasound-intravascular-imaging
#4
Dmitry Bozhko, Angelos Karlas, Dimitris Gorpas, Vasilis Ntziachristos
Hybrid intravascular fluorescence-ultrasound imaging is emerging for reading anatomical and biological information in vivo. By operating through blood, intravascular near-infrared fluorescence (NIRF) detection is affected by hemoglobin attenuation. Improved quantification has been demonstrated with methods that correct for the attenuation of the optical signal as it propagates through blood. These methods assume an attenuation coefficient for blood and measure the distance between detector and the vessel wall by observing the intravascular ultrasound (IVUS) images...
January 17, 2018: Journal of Biophotonics
https://www.readbyqxmd.com/read/29338027/distribution-of-cone-density-spacing-and-arrangement-in-adult-healthy-retinas-with-adaptive-optics-flood-illumination
#5
Richard Legras, Alain Gaudric, Kelly Woog
The aim of this article is to analyse cone density, spacing and arrangement using an adaptive optics flood illumination retina camera (rtx1™) on a healthy population. Cone density, cone spacing and packing arrangements were measured on the right retinas of 109 subjects at 2°, 3°, 4°, 5° and 6° of eccentricity along 4 meridians. The effects of eccentricity, meridian, axial length, spherical equivalent, gender and age were evaluated. Cone density decreased on average from 28 884 ± 3 692 cones/mm2, at 2° of eccentricity, to 15 843 ± 1 598 cones/mm2 at 6°...
2018: PloS One
https://www.readbyqxmd.com/read/29336116/the-retina-of-the-collared-peccary-pecari-tajacu-structure-and-function
#6
Raaya Ezra-Elia, Maya Ross, Nili Avni-Magen, Asaf Berkowitz, Ron Ofri
OBJECTIVE: To study retinal morphology and function in the collared peccary, an ungulate species distantly related to the domestic pig. ANIMAL STUDIES: Twenty captive peccaries anesthetized for routine health examinations. Procedures No abnormalities were noted on a complete ophthalmic examination. Fundi were examined ophthalmoscopically and photographed. The eyes of an individual that died of unrelated, nonocular reasons were studied histologically and by immunohistochemistry...
January 16, 2018: Veterinary Ophthalmology
https://www.readbyqxmd.com/read/29330504/unique-roles-of-%C3%AE-arrestin-in-gpcr-trafficking-revealed-by-photoinducible-dimerizers
#7
Osamu Takenouchi, Hideaki Yoshimura, Takeaki Ozawa
Intracellular trafficking of G protein-coupled receptors (GPCRs) controls their localization and degradation, which affects a cell's ability to adapt to extracellular stimuli. Although the perturbation of trafficking induces important diseases, these trafficking mechanisms are poorly understood. Herein, we demonstrate an optogenetic method using an optical dimerizer, cryptochrome (CRY) and its partner protein (CIB), to analyze the trafficking mechanisms of GPCRs and their regulatory proteins. Temporally controlling the interaction between β-arrestin and β2-adrenergic receptor (ADRB2) reveals that the duration of the β-arrestin-ADRB2 interaction determines the trafficking pathway of ADRB2...
January 12, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29329053/long-term-safety-area-tracking-lt-sat-with-online-failure-detection-and-recovery-for-robotic-minimally-invasive-surgery
#8
Veronica Penza, Xiaofei Du, Danail Stoyanov, Antonello Forgione, Leonardo S Mattos, Elena De Momi
Despite the benefits introduced by robotic systems in abdominal Minimally Invasive Surgery (MIS), major complications can still affect the outcome of the procedure, such as intra-operative bleeding. One of the causes is attributed to accidental damages to arteries or veins by the surgical tools, and some of the possible risk factors are related to the lack of sub-surface visibilty. Assistive tools guiding the surgical gestures to prevent these kind of injuries would represent a relevant step towards safer clinical procedures...
December 22, 2017: Medical Image Analysis
https://www.readbyqxmd.com/read/29328980/consequence-of-intraventricular-hemorrhage-on-neurovascular-coupling-evoked-by-speech-syllables-in-preterm-neonates
#9
Mahdi Mahmoudzadeh, Ghislaine Dehaene-Lambertz, Guy Kongolo, Marc Fournier, Sabrina Goudjil, Fabrice Wallois
Intraventricular Hemorrhage (IVH) is the leading cause of neurological and cognitive impairment in preterm neonates with an incidence that increases with increasing prematurity. In the present study, we tested how preterm neonates with IVH react to external stimulation (i.e. speech syllables). We compared their neural responses measured by electroencephalography (EEG), and hemodynamic responses measured by functional near-infrared spectroscopy (fNIRS), with those of healthy preterms. A neural response to syllables was observed in these infants, but did not induce a vascular response in contrast with healthy neonates...
January 5, 2018: Developmental Cognitive Neuroscience
https://www.readbyqxmd.com/read/29328180/modulation-transfer-function-of-a-fish-eye-lens-based-on-the-sixth-order-wave-aberration-theory
#10
Han Jia, Lijun Lu, Yiqing Cao
A calculation program of the modulation transfer function (MTF) of a fish-eye lens is developed with the autocorrelation method, in which the sixth-order wave aberration theory of ultra-wide-angle optical systems is used to simulate the wave aberration distribution at the exit pupil of the optical systems. The autocorrelation integral is processed with the Gauss-Legendre integral, and the magnification chromatic aberration is discussed to calculate polychromatic MTF. The MTF calculation results of a given example are then compared with those previously obtained based on the fourth-order wave aberration theory of plane-symmetrical optical systems and with those from the Zemax program...
January 10, 2018: Applied Optics
https://www.readbyqxmd.com/read/29328165/time-resolved-study-of-optical-properties-and-microscopic-dynamics-during-the-drying-of-tio2-films-by-spectral-diffusing-wave-spectroscopy
#11
Angel A Duran-Ledezma, Damián Jacinto-Méndez, Luis F Rojas-Ochoa
We present a combined experimental, theoretical, and numerical study of photon transport and microscopic dynamics in rigid and drying turbid thin films. Our setup is based in multispeckle diffusing wave spectroscopy and is adapted for frequency sweep of the illuminating source. We apply our approach to simultaneously monitor the changes in optical properties and microscopic dynamics of turbid thin films of rutile TiO2 powder dispersed in ethanol during the full drying process. Accordingly, we introduce an extension of the photon diffusion model for spectral speckle intensity correlations to account for system microscopic dynamics...
January 10, 2018: Applied Optics
https://www.readbyqxmd.com/read/29328132/digital-hologram-transformations-for-rgb-color-holographic-display-with-independent-image-magnification-and-translation-in-3d
#12
Piotr L Makowski, Weronika Zaperty, Tomasz Kozacki
A new framework for in-plane transformations of digital holograms (DHs) is proposed, which provides improved control over basic geometrical features of holographic images reconstructed optically in full color. The method is based on a Fourier hologram equivalent of the adaptive affine transformation technique [Opt. Express18, 8806 (2010)OPEXFF1094-408710.1364/OE.18.008806]. The solution includes four elementary geometrical transformations that can be performed independently on a full-color 3D image reconstructed from an RGB hologram: (i) transverse magnification; (ii) axial translation with minimized distortion; (iii) transverse translation; and (iv) viewing angle rotation...
January 1, 2018: Applied Optics
https://www.readbyqxmd.com/read/29328104/statistical-properties-of-single-mode-fiber-coupling-of-satellite-to-ground-laser-links-partially-corrected-by-adaptive-optics
#13
Lucien Canuet, Nicolas Védrenne, Jean-Marc Conan, Cyril Petit, Geraldine Artaud, Angelique Rissons, Jerome Lacan
In the framework of satellite-to-ground laser downlinks, an analytical model describing the variations of the instantaneous coupled flux into a single-mode fiber after correction of the incoming wavefront by partial adaptive optics (AO) is presented. Expressions for the probability density function and the cumulative distribution function as well as for the average fading duration and fading duration distribution of the corrected coupled flux are given. These results are of prime interest for the computation of metrics related to coded transmissions over correlated channels, and they are confronted by end-to-end wave-optics simulations in the case of a geosynchronous satellite (GEO)-to-ground and a low earth orbit satellite (LEO)-to-ground scenario...
January 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
https://www.readbyqxmd.com/read/29328096/approximate-bayesian-computation-techniques-for-optical-characterization-of-nanoparticle-clusters
#14
Ozan Burak Ericok, Ali Taylan Cemgil, Hakan Erturk
Characterization of nanoparticle aggregates from observed scattered light leads to a highly complex inverse problem. Even the forward model is so complex that it prohibits the use of classical likelihood-based inference methods. In this study, we compare four so-called likelihood-free methods based on approximate Bayesian computation (ABC) that requires only numeric simulation of the forward model without the need of evaluating a likelihood. In particular, rejection, Markov chain Monte Carlo, population Monte Carlo, and adaptive population Monte Carlo (APMC) are compared in terms of accuracy...
January 1, 2018: Journal of the Optical Society of America. A, Optics, Image Science, and Vision
https://www.readbyqxmd.com/read/29324929/our-solution-for-fusion-of-simultaneusly-acquired-whole-body-scintigrams-and-optical-images-as-usesful-tool-in-clinical-practice-in-patients-with-differentiated-thyroid-carcinomas-after-radioiodine-therapy-a-useful-tool-in-clinical-practice
#15
Milovan Matovic, Milica Jankovic, Marko Barjaktarovic, Marija Jeremic
OBJECTIVE: After radioiodine therapy of differentiated thyroid cancer (DTC) patients, whole body scintigraphy (WBS) is standard procedure before releasing the patient from the hospital. A common problem is the precise localization of regions where the iod-avide tissue is located. Sometimes is practically impossible to perform precise topographic localization of such regions. METHOD: In order to face this problem, we have developed a low-cost Vision-Fusion system for web-camera image acquisition simultaneously with routine scintigraphic whole body acquisition including the algorithm for fusion of images given from both cameras...
September 2017: Hellenic Journal of Nuclear Medicine
https://www.readbyqxmd.com/read/29320684/label-free-imaging-and-bending-analysis-of-microtubules-by-rocs-microscopy-and-optical-trapping
#16
Matthias D Koch, Alexander Rohrbach
Mechanical manipulation of single cytoskeleton filaments and their monitoring over long times is difficult because of fluorescence bleaching or phototoxic protein degradation. The integration of label-free microscopy techniques, capable of imaging freely diffusing, weak scatterers such as microtubules (MTs) in real-time, and independent of their orientation, with optical trapping and tracking systems, would allow many new applications. Here, we show that rotating-coherent-scattering microscopy (ROCS) in dark-field mode can also provide strong contrast for structures far from the coverslip such as arrangements of isolated MTs and networks...
January 9, 2018: Biophysical Journal
https://www.readbyqxmd.com/read/29317725/precise-phase-demodulation-of-single-carrier-frequency-interferogram-by-pixel-level-lissajous-figure-and-ellipse-fitting
#17
Fengwei Liu, Yongqian Wu, Fan Wu, Niels König, Robert Schmitt, Yongjian Wan, Yan Xu
Phase demodulation from a single carrier-frequency fringe pattern is becoming increasingly important particularly in areas of optical metrology such as dynamic interferometry, deflectometry and profilometry. The Fourier transform (FT) method and the spatial-carrier phase-shifting technique (SCPS) are two popular and well-established approaches to demodulation. However FT has the drawback of significant edge errors because of the Gibbs effect, whilst detuning errors for the local phase shift occur when SCPS is applied...
January 9, 2018: Scientific Reports
https://www.readbyqxmd.com/read/29313052/a-deep-learning-approach-to-digitally-stain-optical-coherence-tomography-images-of-the-optic-nerve-head
#18
Sripad Krishna Devalla, Khai Sing Chin, Jean-Martial Mari, Tin A Tun, Nicholas G Strouthidis, Tin Aung, Alexandre H Thiéry, Michaël J A Girard
Purpose: To develop a deep learning approach to digitally stain optical coherence tomography (OCT) images of the optic nerve head (ONH). Methods: A horizontal B-scan was acquired through the center of the ONH using OCT (Spectralis) for one eye of each of 100 subjects (40 healthy and 60 glaucoma). All images were enhanced using adaptive compensation. A custom deep learning network was then designed and trained with the compensated images to digitally stain (i.e., highlight) six tissue layers of the ONH...
January 1, 2018: Investigative Ophthalmology & Visual Science
https://www.readbyqxmd.com/read/29310964/early-patterns-of-macular-degeneration-in-abca4-associated-retinopathy
#19
Kamron N Khan, Melissa Kasilian, Omar A R Mahroo, Preena Tanna, Angelos Kalitzeos, Anthony G Robson, Kazushige Tsunoda, Takeshi Iwata, Anthony T Moore, Kaoru Fujinami, Michel Michaelides
PURPOSE: To describe the earliest features of ABCA4-associated retinopathy. DESIGN: Case series. PARTICIPANTS: Children with a clinical and molecular diagnosis of ABCA4-associated retinopathy without evidence of macular atrophy. METHODS: The retinal phenotype was characterized by color fundus photography, OCT, fundus autofluorescence (FAF) imaging, electroretinography, and in 2 patients, adaptive optics scanning laser ophthalmoscopy (AOSLO)...
January 5, 2018: Ophthalmology
https://www.readbyqxmd.com/read/29302786/intraoperative-changes-in-corneal-structure-during-excimer-laser-phototherapeutic-keratectomy-ptk-assessed-by-intraoperative-optical-coherence-tomography
#20
Sebastian Siebelmann, Jens Horstmann, Paula Scholz, Björn Bachmann, Mario Matthaei, Manuel Hermann, Claus Cursiefen
PURPOSE: Excimer laser phototherapeutic keratectomy (PTK) is a safe treatment for superficial corneal opacities, e.g., in corneal dystrophies or degenerations. Nevertheless, no standardized treatment protocols are available and intraoperative monitoring was not possible, so far. Here we evaluate the potential benefits of the intraoperative assessment by microscope-integrated intraoperative optical coherence tomography (MI-OCT) of corneal optical properties during PTK. METHODS: Retrospective study of eight patients (one male, seven females; age range, 43-80 years, mean = 66...
January 4, 2018: Graefe's Archive for Clinical and Experimental Ophthalmology
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