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phase coherence

André Luiz Vieira Lockmann, Flavio Afonso Gonçalves Mourão, Márcio Flávio Dutra Moraes
The rat inferior colliculus (IC) is a major midbrain relay for ascending inputs from the auditory brainstem and has been suggested to play a key role in the processing of aversive sounds. Previous studies have demonstrated that auditory fear conditioning (AFC) potentiates transient responses to brief tones in the IC, but it remains unexplored whether AFC modifies responses to sustained periodic acoustic stimulation - a type of response called steady-state evoked potential (SSEP). Here we used an amplitude-modulated tone - 10 kHz tone with a sinusoidal amplitude modulation of 53...
April 26, 2017: Journal of Neurophysiology
George J Manayath, Vanee Sheth Shah, Veerappan R Saravanan, Venkatapathy Narendran
PURPOSE: To study multimodal imaging features of polypoidal choroidal vasculopathy (PCV) associated with central serous chorioretinopathy (CSC) in the same eye. METHODS: A retrospective observational study of cases of suspected PCV which underwent indocyanine green angiography, fundus fluorescein angiography and optical coherence tomography was done, to look for simultaneous typical CSC-like active leak in the same eye. The relevant history, best-corrected visual acuity, optical coherence tomography, fundus fluorescein angiography, and indocyanine green angiography findings were analyzed...
April 25, 2017: Retina
Mahmoud Sabbah, Kazushige Kadota, Azza El-Eraky, Hanan M Kamal, Ahmed-Tageldien Abdellah, Ahmed El Hawary
Optical frequency domain imaging (OFDI) was utilized to compare the prevalence of neoatherosclerosis (NA) and morphological characteristics of the neointimal tissue in second generation drug eluting stent (G2-DES)-treated lesions between early (<1 year, E-ISR) and late (>1 year, L-ISR) in-stent restenotic phases. Data comparing NA and in vivo tissue characteristics between early and late in-stent restenosis (ISR) after implantation of G2-DES is limited. An OFDI analysis was performed in 50 G2-DESs {35 everolimus-eluting stent [22 cobalt-chromium (CoCr), 13 platinum-chromium (PtCr)], and 15 biolimus-eluting stent [BES]} ISR lesions (46 consecutive patients) undergoing target lesion revascularization, classified as E-ISR (n = 22 lesion) and L-ISR (n = 28 lesion)...
April 25, 2017: International Journal of Cardiovascular Imaging
A V Malm, T A Waigh
The flow instabilities of solutions of high molecular weight DNA in the entangled semi-dilute concentration regime were investigated using optical coherence tomography velocimetry, a technique that provides high spatial (probe volumes of 3.4 pL) and temporal resolution (sub μs) information on the flow behaviour of complex fluids in a rheometer. The velocity profiles of the opaque DNA solutions (high and low salt) were measured as a function of the distance across the gap of a parallel plate rheometer, and their evolution over time was measured...
April 26, 2017: Scientific Reports
Tess K Koerner, Yang Zhang, Peggy B Nelson, Boxiang Wang, Hui Zou
This study examined how speech babble noise differentially affected the auditory P3 responses and the associated neural oscillatory activities for consonant and vowel discrimination in relation to segmental- and sentence-level speech perception in noise. The data were collected from 16 normal-hearing participants in a double-oddball paradigm that contained a consonant (/ba/ to /da/) and vowel (/ba/ to /bu/) change in quiet and noise (speech-babble background at a -3 dB signal-to-noise ratio) conditions. Time-frequency analysis was applied to obtain inter-trial phase coherence (ITPC) and event-related spectral perturbation (ERSP) measures in delta, theta, and alpha frequency bands for the P3 response...
April 18, 2017: Hearing Research
Peng Si, Debasish Sen, Rebecca Dutta, Siavash Yousefi, Roopa Dalal, Yonatan Winetraub, Orly Liba, Adam de la Zerda
Optical Coherence Tomography (OCT) imaging of living subjects offers increased depth of penetration while maintaining high spatial resolution when compared to other optical microscopy techniques. However, since most protein biomarkers do not exhibit inherent contrast detectable by OCT, exogenous contrast agents must be employed for imaging specific cellular biomarkers of interest. While a number of OCT contrast agents have been previously studied, demonstrations of molecular targeting with such agents in live animals have been historically challenging and notably limited in success...
April 24, 2017: Scientific Reports
Bo-Jui Chang, Victor Didier Perez Meza, Ernst H K Stelzer
Light-sheet-based fluorescence microscopy (LSFM) features optical sectioning in the excitation process. It minimizes fluorophore bleaching as well as phototoxic effects and provides a true axial resolution. The detection path resembles properties of conventional fluorescence microscopy. Structured illumination microscopy (SIM) is attractive for superresolution because of its moderate excitation intensity, high acquisition speed, and compatibility with all fluorophores. We introduce SIM to LSFM because the combination pushes the lateral resolution to the physical limit of linear SIM...
April 24, 2017: Proceedings of the National Academy of Sciences of the United States of America
Stephen J Pennycook
Over the last three decades the scanning transmission electron microscope (STEM) has gone from a specialized instrument for nanoscale analysis to the microscope of choice for atomic resolution imaging of materials, allowing incoherent high-angle annular dark field (Z-contrast) imaging, coherent phase contrast modes (conventional and annular bright field), electron energy loss and energy dispersive X-ray spectroscopy. All signals are achieving atomic resolution and several are available simultaneously. This would not have been possible without the development of an aberration corrector for the STEM, spearheaded by Ondrej Krivanek in the late 1990s, which finally allowed the benefits of the STEM to translate from "in-principle" to actual daily practice...
March 18, 2017: Ultramicroscopy
Chao Jin, Liang Wang, Yuli Chen, Nan Guo, Wenghong Chung, Hoyin Au, Zhaohui Li, Hwa-Yaw Tam, Chao Lu
A single-measurement sweep-free distributed Brillouin optical time domain analyzer (BOTDA) sensor based on phase detection is proposed and experimentally demonstrated employing digital optical frequency comb (DOFC) probe signal. Brillouin Phase Spectrum (BPS) of DOFC probe induced by Brillouin interaction is measured using coherent detection in a single acquisition, without any frequency scanning and data averaging. Single-measurement BOTDA sensor based on BPS in 10km long fiber is demonstrated with a response time of 100 μs, which is limited only by the fiber length...
April 17, 2017: Optics Express
Bowen Li, Ying Yu, Xiaoming Wei, Yiqing Xu, Kevin K Tsia, Kenneth K Y Wong
Fiber-stretcher based phase-lock loop (PLL) is a mature technique in fiber mode-locked lasers for repetition-rate stabilization. However, undesired side effects may be induced if not properly handled, which is easily overlooked owing to the lack of single-shot spectral analyzers. Thanks to the ultrafast spectral analyzing capability of optical time-stretch, an intriguing spectral dynamics is observed in a repetition-rate-stabilized nonlinear polarization rotation (NPR) mode-locked laser. Under the dynamic state, the optical spectra of pulses undergo dramatic evolution in every round trip while the pulse energy is relatively constant...
April 17, 2017: Optics Express
Di Che, Feng Yuan, William Shieh
Semiconductor lasers are versatile optical transmitters in nature. Through the direct modulation (DM), the intensity modulation is realized by the linear mapping between the injection current and the light power, while various angle modulations are enabled by the frequency chirp. Limited by the direct detection, DM lasers used to be exploited only as 1-D (intensity or angle) transmitters by suppressing or simply ignoring the other modulation. Nevertheless, through the digital coherent detection, simultaneous intensity and angle modulations (namely, 2-D complex DM, CDM) can be realized by a single laser diode...
April 17, 2017: Optics Express
Janaka C Ranasinghesagara, Giuseppe De Vito, Vincenzo Piazza, Eric O Potma, Vasan Venugopalan
We develop a computational framework to examine the factors responsible for scattering-induced distortions of coherent anti-Stokes Raman scattering (CARS) signals in turbid samples. We apply the Huygens-Fresnel wave-based electric field superposition (HF-WEFS) method combined with the radiating dipole approximation to compute the effects of scattering-induced distortions of focal excitation fields on the far-field CARS signal. We analyze the effect of spherical scatterers, placed in the vicinity of the focal volume, on the CARS signal emitted by different objects (2μm diameter solid sphere, 2μm diameter myelin cylinder and 2μm diameter myelin tube)...
April 17, 2017: Optics Express
Makoto Hirose, Kei Shimomura, Nicolas Burdet, Yukio Takahashi
Coherent diffraction imaging (CDI) is a method for reconstructing the complex-valued image of an object from diffraction intensities by using iterative phasing methods. X-ray ptychography is a scanning type of CDI using X-rays, allowing us to visualize the complex transmission function of an extended specimen. We here propose the use of the Kramers-Kronig relation (KKR) as an additional constraint in phase retrieval algorithms for multiple-energy X-ray ptychography using the absorption edge of a specific element...
April 17, 2017: Optics Express
Dong Shuo, Jie Lian, Mark H Jhon, Yinthai Chan, Zhi-Heng Loh
Femtosecond optical pump-probe spectroscopy resolves hitherto unobserved coherent acoustic phonons in colloidal CdSe/CdS core/shell nanoplatelets (NPLs). With increasing pump fluence, the frequency of the in-plane acoustic mode increases from 5.2 to 10.7 cm(-1), whereas the frequency of the out-of-plane mode remains at ~20 cm(-1). Analysis of the oscillation phases suggests that the coherent acoustic phonon generation mechanism transitions from displacive excitation to sub-picosecond Auger hole trapping with increasing pump fluence...
April 24, 2017: Nano Letters
Hao Yang, Ian MacLaren, Lewys Jones, Gerardo T Martinez, Martin Simson, Martin Huth, Henning Ryll, Heike Soltau, Ryusuke Sagawa, Yukihito Kondo, Colin Ophus, Peter Ercius, Lei Jin, András Kovács, Peter D Nellist
Recent development in fast pixelated detector technology has allowed a two dimensional diffraction pattern to be recorded at every probe position of a two dimensional raster scan in a scanning transmission electron microscope (STEM), forming an information-rich four dimensional (4D) dataset. Electron ptychography has been shown to enable efficient coherent phase imaging of weakly scattering objects from a 4D dataset recorded using a focused electron probe, which is optimised for simultaneous incoherent Z-contrast imaging and spectroscopy in STEM...
April 1, 2017: Ultramicroscopy
Che-Chou Shen, Hsiao-Chi Yang
Ultrasound array imaging systems rely on a presumed beamforming sound velocity to calculate the time compensation of each element for receive focusing. The mismatch between the tissue sound velocity and the beamforming sound velocity can degrade the focusing quality due to loss of phase coherence. Since the tissue sound velocity cannot be known in prior, an adaptive optimization of beamforming sound velocity is required to improve the image quality. Differential phase gradient of channel data is proposed to estimate the optimal sound velocity for beamforming...
April 12, 2017: Ultrasonics
C Corsi, I Liontos, M Bellini, S Cavalieri, P Cancio Pastor, M Siciliani de Cumis, R Eramo
We present the results of direct interferometric measurements on the pulse-to-pulse phase jitter of a metrological, fiber-based, infrared (IR) frequency comb. We show that the short-time evolution of such phase fluctuations, which cannot be actively controlled by any feedback system, imposes a stringent limit on the tooth linewidth of extreme ultraviolet (XUV) combs produced by high-order harmonic conversion, thus explaining the difference of 9 orders of magnitude between the coherence times of state-of-the-art IR and XUV frequency combs...
April 7, 2017: Physical Review Letters
Pengfei Wu, Zi Liang, Xing Zhao, Lei Su, Lipei Song
The need to image objects through light-scattering materials is common in a range of applications. Different methods have been investigated to acquire the image of the object when diffusers are presented. In this paper, we demonstrate the object reconstruction with single-shot imaging based on the correlography principle and phase retrieval algorithm with coherent illumination. We prove the possibility of reconstructing positive and negative objects in both transmission and reflection modes with collimated and scattered light...
April 20, 2017: Applied Optics
Simone Falk, Cosima Lanzilotti, Daniele Schön
Musical rhythm positively impacts on subsequent speech processing. However, the neural mechanisms underlying this phenomenon are so far unclear. We investigated whether carryover effects from a preceding musical cue to a speech stimulus result from a continuation of neural phase entrainment to periodicities that are present in both music and speech. Participants listened and memorized French metrical sentences that contained (quasi-)periodic recurrences of accents and syllables. Speech stimuli were preceded by a rhythmically regular or an irregular musical cue...
April 21, 2017: Journal of Cognitive Neuroscience
Hong Liang, Antoine Labbé, Jeannie Le Mouhaër, Céline Plisson, Christophe Baudouin
Purpose: The purpose of this study was to evaluate the efficacy of new viscous cysteamine hydrochloride (CH) eye drops (vCH 0.55%) compared with standard CH 0.10% drops treatment. Methods: This was an open-label, phase III, randomized, two-arm multicenter trial conducted at two centers in France. Cystinosis patients ≥2 years old were randomized 1:1 to receive eye drops, four times per day for 90 days in both eyes. We compared the superiority in reducing corneal cystine crystal density as assessed by in vivo confocal microscopy (IVCM)...
April 1, 2017: Investigative Ophthalmology & Visual Science
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