Articles de revues : « Fast Optical Signal »

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Sheng, Zhiyong, Dandan Qu, Yuan Zhang et Dan Yang. « The Fast Detection and Identification Algorithm of Optical Fiber Intrusion Signals ». Algorithms 11, n^o 9 (23 août 2018) : 129. http://dx.doi.org/10.3390/a11090129.

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With the continuous development of optical fiber sensing technology, the Optical Fiber Pre-Warning System (OFPS) has been widely used in various fields. The OFPS identifies the type of intrusion based on the detected vibration signal to monitor the surrounding environment. Aiming at the real-time requirements of OFPS, this paper presents a fast algorithm to accelerate the detection and recognition processing of optical fiber intrusion signals. The algorithm is implemented in an embedded system that is composed of a digital signal processor (DSP). The processing flow is divided into two parts. First, the dislocation processing method is adopted for the sum processing of original signals, which effectively improves the real-time performance. The filtered signals are divided into two parts and are parallel processed by two DSP boards to save time. Then, the data is input into the identification module for feature extraction and classification. Experiments show that the algorithm can effectively detect and identify the optical fiber intrusion signals. At the same time, it accelerates the processing speed and meets the real-time requirements of OFPS for detection and identification.

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Radhakrishnan, Harsha, Wim Vanduffel, Hong Ping Deng, Leeland Ekstrom, David A. Boas et Maria Angela Franceschini. « Fast optical signal not detected in awake behaving monkeys ». NeuroImage 45, n^o 2 (avril 2009) : 410–19. http://dx.doi.org/10.1016/j.neuroimage.2008.12.014.

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Ziskind-Conhaim, Lea, et Stephen Redman. « Spatiotemporal Patterns of Dorsal Root–Evoked Network Activity in the Neonatal Rat Spinal Cord : Optical and Intracellular Recordings ». Journal of Neurophysiology 94, n^o 3 (septembre 2005) : 1952–61. http://dx.doi.org/10.1152/jn.00209.2005.

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Spatiotemporal patterns of dorsal root–evoked potentials were studied in transverse slices of the rat spinal cord by monitoring optical signals from a voltage-sensitive dye with multiple-photodiode optic camera. Typically, dorsal root stimulation generated two basic waveforms of voltage images: dual-component images consisting of fast, spike-like signal followed by a slow signal in the dorsal horn, and small, slow signals in the ventral horn. To qualitatively relate the optical signals to membrane potentials, whole cell recordings were combined with measurements of light absorption in the area around the soma. The slow optical signals correlated closely with subthreshold postsynaptic potentials in all regions of the cord. The spike-like component was not associated with postsynaptic action potentials, suggesting that the fast signal was generated by presynaptic action potentials. Firing in a single neuron could not be detected optically, implying that local voltage images originated from synchronously activated neuronal ensembles. Blocking glutamatergic synaptic transmission inhibited excitatory postsynaptic potentials (EPSPs) and significantly reduced the slow optical signals, indicating that they were mediated by glutamatergic synapses. Suppressing glycine-mediated inhibition increased the amplitude of both optical signals and EPSPs, while blocking GABAA receptor–mediated synapses, increased the amplitude and time course of EPSPs and prolonged the duration of voltage images in larger areas of the slice. The close correlation between evoked EPSPs and their respective local voltage images shows the advantage of the high temporal resolution optical system in measuring both the spatiotemporal dynamics of segmental network excitation and integrated potentials of neuronal ensembles at identified sites.

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YAO, XIN-CHENG, LEI LIU et YANG-GUO LI. « INTRINSIC OPTICAL SIGNAL IMAGING OF RETINAL ACTIVITY IN FROG EYE ». Journal of Innovative Optical Health Sciences 02, n^o 02 (avril 2009) : 201–8. http://dx.doi.org/10.1142/s1793545809000462.

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Using a near-infrared (NIR) light flood-illumination imager equipped with a high-speed (120 Hz) CCD camera, we demonstrated optical imaging of stimulus-evoked retinal activity in isolated, but intact, frog eye. Both fast and slow transient intrinsic optical signals (IOSs) were observed. Fast optical response occurred immediately after the stimulus onset, could reach peak magnitude within 100 ms, and correlated tightly with ON and OFF edges of the visible light stimulus; while slow optical response lasted a relatively long time (many seconds). High-resolution images revealed both positive (increasing) and negative (decreasing) IOSs, and dynamic optical change at individual CCD pixels could often exceed 10% of the background light intensity. Our experiment on isolated eye suggests that further development of fast, high (sub-cellular) resolution fundus imager will allow robust detection of fast IOSs in vivo, and thus allow noninvasive, three-dimensional evaluation of retinal neural function.

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Yao, Xincheng, et Tae-Hoon Kim. « Fast intrinsic optical signal correlates with activation phase of phototransduction in retinal photoreceptors ». Experimental Biology and Medicine 245, n^o 13 (19 juin 2020) : 1087–95. http://dx.doi.org/10.1177/1535370220935406.

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Quantitative assessment of physiological condition of retinal photoreceptors is desirable for better detection and treatment evaluation of eye diseases that can cause photoreceptor dysfunctions. Functional intrinsic optical signal (IOS) imaging, also termed as optoretinography (ORG) or optophysiology, has been proposed as a high-resolution method for objective assessment of retinal physiology. Fast IOS in retinal photoreceptors shows a time course earlier than that of electroretinography a-wave, promising an objective marker for noninvasive ORG of early phototransduction process in retinal photoreceptors. In this article, recent observations of fast photoreceptor-IOS in animal and human retinas are summarized, and the correlation of fast photoreceptor-IOS to five steps of phototransduction process is discussed. Transient outer segment conformational change, due to inter-disc space shrinkage correlated with activation phase of phototransduction, has been disclosed as a primary source of the fast photoreceptor-IOS. Impact statement As the center of phototransduction, retinal photoreceptors are responsible for capturing and converting photon energy to bioelectric signals for following visual information processing in the retina. This article summarizes experimental observation and discusses biophysical mechanism of fast photoreceptor-intrinsic optical signal (IOS) correlated with early phase of phototransduction. Quantitative imaging of fast photoreceptor-IOS may provide objective optoretinography to advance the study and diagnosis of age-related macular degeneration, retinitis pigmentosa, diabetic retinopathy, and other eye diseases that can cause photoreceptor dysfunctions.

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Sun, Xiaoyong, Shaojing Su, Xiaojun Guo et Junyu Wei. « A Fast and Blind Chromatic Dispersion Estimation Based on Stepwise Optimal Order Search Method in Fractional Domain ». Photonics 9, n^o 4 (28 mars 2022) : 223. http://dx.doi.org/10.3390/photonics9040223.

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A fast and low-complexity blind chromatic dispersion (CD) estimation method is proposed by a stepwise optimal order search of fractional Fourier transform (FrFT) in coherent optical communications. The method can track the cumulative dispersion over time in future dynamic and flexible scenarios. The validity of the FrFT method is verified by analogy to the field of CD estimation from the energy concentration property of the chirp signal, and the estimation equation of the CD value is obtained by parameter transformation. Numerical simulations have been carried out in the CD range of 1600 ps/nm to 32,000 ps/nm for 28 GBaud PM-QPSK and 14 GBaud PM-16QAM signals. The results show that the proposed algorithm achieves a high CD estimation accuracy with an average estimation error of less than 50 ps/nm within the 4096 sampling points and an order search interval of 0.0001. The effects of the polarization mode dispersion, optical signal-to-noise ratio and nonlinearity on CD estimation performance are discussed. In addition, the stepwise optimal order search method can achieve the purpose of greatly reducing the computational complexity under the premise of ensuring the accuracy of CD estimation.

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Sytnik, O. « Optimal nonlinear fi ltering of stochastic processes in rescue radar ». RADIOFIZIKA I ELEKTRONIKA 26, n^o 3 (2021) : 18–23. http://dx.doi.org/10.15407/rej2021.03.018.

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Subject and Purpose. Smoke, fog, avalanches, debris of collapsed structures and other optically opaque obstacles in both natural and man-made disasters make optical sensors useless for detecting victims. Electromagnetic waves of the decimeter range penetrate well almost all obstacles, reflect from the trapped people and return to the radar receiver. Due to the breathing and heartbeat, the human-reflected sounding signals get the Doppler phase modulation, which is an information signal. These information signals and their properties provide the subject matter for the present research with the aim to create optimal methods and algorithms of random event processing for the prompt location of survivors by rescuers. Method and Methodology. The method of stochastic analysis of the fluctuation Doppler spectra of reflected sounding signals shows that the information signals have properties of conditional Markov processes. Results. The problem of optimal nonlinear filtering of conditional Markov processes entering the radar signal processing unit has been examined closely. An optimal adaptive filter has been proposed to reduce the masking effect of interferences caused by non-stationary noises and sounding signal reflections from stationary objects. The optimality criterion is the minimum mean square error function whose current value is evaluated in real time during the filtering process as the statistics is accumulated. The filter coefficients are calculated by the recurrent, steepest descent algorithm. The real-time work is carried out through the use of fast Fourier transform algorithms. Conclusion. The structure of the optimal adaptive filter to be built into the radar signal processing unit has been developed. Real radar signals have shown that the optimal filtering during the signal processing in systems designed for detecting live people by their breathing and heartbeat facilitates the interpretation of the observed signals. Some spectra of real signals generated by human breathing and heartbeat are presented.

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YU, LI-PING, JIAN-CHEN GUO, LI-DEK CHOU, TE-LUN MA, JHENG-SYONG WU, JIANN-DER LEE et CHIEN CHOU. « POLARIZATION-SENSITIVE OPTICAL COHERENCE TOMOGRAPHY USING A MODIFIED BALANCE DETECTOR ». Journal of Innovative Optical Health Sciences 05, n^o 04 (octobre 2012) : 1250024. http://dx.doi.org/10.1142/s1793545812500241.

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In conventional polarization-sensitive optical coherence tomography (PS-OCT), phase retardation is obtained by the amplitude of P and S polarization only, and the fast axis angle is obtained by the phase difference in P and S polarizations via Hilbert transformation. In this paper, we proposed a modified PS-OCT setup in which the phase retardation and fast axis angle are simply expressed as the function of the amplitude of P and S polarization and their differential signal. Due to the common-path feature between the two channels of P and S polarization, the fluctuation in the measurement of phase retardation and fast axis angle caused by excess noise and phase noise from the laser source can be reduced by the differential signal of P and S polarization via a modified balance detector. Thus, the signal of phase retardation and fast angle axis in the deep layer of a porcine sample can be improved.

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Nelson, D. A., et L. C. Katz. « Optical imaging of brain slice preparations using voltage sensitive dyes ». Proceedings, annual meeting, Electron Microscopy Society of America 53 (13 août 1995) : 810–11. http://dx.doi.org/10.1017/s0424820100140427.

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Fast responding, biological membrane-soluble voltage sensitive dyes are probes which make it possible to directly monitor the electrical activity of neuronal tissues with both high temporal and high spatial resolution. High temporal resolution is desirable because of the millisecond time scale on which neuronal events occur. High spatial resolution is desirable to better reveal the complex interactions between different regions of neural circuits.Taking full advantage of the promise of voltage sensitive dyes can be both difficult and expensive. Tissues stained with these dyes undergo very small (often less than one part in a thousand) relative changes in fluorescence in response to changes in transmembrane potential. The signal-to-noise ratio is similarly small for these responses. Finally, the responses are very fast. Most major components of the signal rise to their maximum and then disappear within 15 milliseconds of stimulation (figure 1).Because standard video cameras are inadequate for recording the very small and very fast optical signals transduced by voltage sensitive dyes, specialized detection equipment is required. This entails a high cost per pixel, often limiting the practial number of detector elements to a few hundred or even less.

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Chkalova, D. G. « Fast optical signal filtering by means of amplitude and phase operators ». Journal of Physics : Conference Series 1679 (novembre 2020) : 022092. http://dx.doi.org/10.1088/1742-6596/1679/2/022092.

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Pachnicke, S., J. Reichert, S. Spalter et E. Voges. « Fast analytical assessment of the signal quality in transparent optical networks ». Journal of Lightwave Technology 24, n^o 2 (février 2006) : 815–24. http://dx.doi.org/10.1109/jlt.2005.862472.

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Sekino, Yuko, Kunihiko Obata, Manabu Tanifuji, Makoto Mizuno et Jin Murayama. « Delayed Signal Propagation via CA2 in Rat Hippocampal Slices Revealed by Optical Recording ». Journal of Neurophysiology 78, n^o 3 (1 septembre 1997) : 1662–68. http://dx.doi.org/10.1152/jn.1997.78.3.1662.

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Sekino, Yuko, Kunihiko Obata, Manabu Tanifuji, Makoto Mizuno, and Jin Murayama. Delayed signal propagation via CA2 in rat hippocampal slices revealed by optical recording. J. Neurophysiol. 78: 1662–1668, 1997. Signal propagation from mossy fibers to CA1 neurons was investigated in rat hippocampal slices by a combination of electrical and optical recordings. The slices were prepared by oblique sectioning of the middle part of the hippocampus to preserve fiber connections. The mossy fibers were stimulated to induce population spikes (PSs) and excitatory postsynaptic potentials in the middle part of the CA1 region. Latencies of maximal PSs in CA1 varied widely among slices; they ranged from 7 to 13.5 ms, with two maxima at 9 and 11.5 ms. The fastest PSs probably are evoked by the Schaffer collaterals that connect the CA3 and CA1 regions in the well-known trisynaptic circuit. However, the slower PSs suggest the existence of additional delayed inputs. To determine the source of the delayed input, slices were stained with a voltage-sensitive dye, RH482, and the optical signals relevant to membrane potential changes were detected by a high-resolution optical imaging system. Optical recording of responses to mossy fiber stimulation indicated two distinct types of signal propagation from CA3 to CA1. In preparations evincing the fast type of propagation, signals spread to CA1 within 7.2 ms after the mossy fiber stimulation. During such propagation, activity flowed directly from CA3 to the stratum radiatum of CA1. Other preparations illustrated slow signal propagation, in which optical signals were generated in CA2 before spreading to CA1. During such slow signal transmission, activity persisted in CA2 and its surrounding area for 3 ms before propagating to the strata radiatum and oriens in CA1. In such cases, CA1 activity was detected within 10.8 ms of mossy fiber stimulation. In some slices, a mixture of the fast and slow propagation patterns was observed, indicating that these two transmission modes can coexist. Our data reveal that CA2 neurons can transmit delayed excitatory signals to CA1 neurons. We therefore conclude that consideration of electrical signal propagation through the hippocampus should include flow through the CA2 region in addition to the traditional dentate gyrus–CA3–CA1 trisynaptic circuit.

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Arai, Yoshiyasu, Yoko Momose-Sato, Katsushige Sato et Kohtaro Kamino. « Optical Mapping of Neural Network Activity in Chick Spinal Cord at an Intermediate Stage of Embryonic Development ». Journal of Neurophysiology 81, n^o 4 (1 avril 1999) : 1889–902. http://dx.doi.org/10.1152/jn.1999.81.4.1889.

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Optical mapping of neural network activity in chick spinal cord at an intermediate stage of embryonic development. We have applied multiple-site optical recording of transmembrane potential changes to recording of neuronal pathway/network activity from embryonic chick spinal cord slice preparations. Spinal cord preparations were dissected from 8-day-old chick embryos at Hamburger-Hamilton stage 33, and transverse slice preparations were prepared with the 13th cervical spinal nerve or with the 2nd or 5th lumbosacral spinal nerve intact. The slice preparations were stained with a voltage-sensitive merocyanine-rhodanine dye (NK2761). Transmembrane voltage-related optical (dye-absorbance) changes evoked by spinal nerve stimulation with positive square-current pulses using a suction electrode were recorded simultaneously from many loci in the preparation, using a 128- or 1,020-element photodiode array. Optical responses were detected from dorsal and ventral regions corresponding to the posterior (dorsal) and anterior (ventral) gray horns. The optical signals were composed of two components, fast spike-like and slow signals. In the dorsal region, the fast spike-like signal was identified as the presynaptic action potential in the sensory nerve and the slow signal as the postsynaptic potential. In the ventral region, the fast spike-like signal reflects the antidromic action potential in motoneurons, and the slow signal is related to the postsynaptic potential evoked in the motoneuron. In preparations in which the ventral root was cut microsurgically, the antidromic action potential-related optical signals were eliminated. The areas of the maximal amplitude of the evoked signals in the dorsal and ventral regions were located near the dorsal root entry zone and the ventral root outlet zone, respectively. Quasiconcentric contour-line maps were obtained in the dorsal and ventral regions, suggesting the functional arrangement of the dorsal and ventral synaptic connections. Synaptic fatigue induced by repetitive stimuli in the ventral synapses was more rapid than in the dorsal synapses. The distribution patterns of the signals were essentially similar among C13, LS2, and LS5 preparations, suggesting that there is no difference in the spatiotemporal pattern of the neural responses along the rostrocaudal axis of the spinal cord at this developmental stage. In the ventral root-cut preparations, comparing the delay times between the ventral slow optical signals, we have been able to demonstrate that neural network-related synaptic connections are generated functionally in the embryonic spinal cord at Hamburger-Hamilton stage 33.

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Shan, Ning. « Design and Experiment Research of a Non-Contact Optical Fiber F-P Ultrasound Sensor for Detecting Surface Defects ». Applied Mechanics and Materials 34-35 (octobre 2010) : 322–26. http://dx.doi.org/10.4028/www.scientific.net/amm.34-35.322.

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Laser ultrasound technology has many advantages such as being non-contact, nondestructive, fast, accurate and low cost. Therefore it is usually used as an effective way to detect and characterize small surface or subsurface breaking cracks. The optical fiber F-P sensor is adapted to laser ultrasound detection field because it can detect ultrasound signals non-contact. But the optical fiber F-P sensor deviates from working point easily because of machining error and external factors in practical applications. It leads to output signal attenuation and the decreasing of signal noise ratio. On this problem, an optical fiber F-P sensing system based on two wavelength quadrature-shifted demodulation technique is designed. The mathematical model of sensing system is established. Differential Evolution Algorithm is introduced to establish the optimal model of sensing system for the first time. The structure of sensing system is optimized designed. The non-contact laser ultrasound experimental devices based on optical fiber F-P senor are established for detecting surface defects. The experimental results show this sensor can detect surface defects effectively. It has higher sensitivity and larger signal-to-noise ratio.

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Sato, Katsushige, et Yoko Momose-Sato. « Optical Detection of Developmental Origin of Synaptic Function in the Embryonic Chick Vestibulocochlear Nuclei ». Journal of Neurophysiology 89, n^o 6 (juin 2003) : 3215–24. http://dx.doi.org/10.1152/jn.01169.2002.

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Functional organization of the brain stem vestibulocochlear nuclei during embryogenesis was investigated using a multiple-site optical recording technique with a fast voltage-sensitive dye. Brain stem slices with the cochlear and/or vestibular nerves attached were dissected from 6- to 8-day-old (E6–E8) chick embryos. Electrical responses evoked by cochlear or vestibular nerve stimulation were optically recorded simultaneously from many loci of the preparations. In E7 and E8 preparations, we identified two components of the optical response with cochlear or vestibular nerve stimulation; one was a fast spike-like signal related to the action potential, and the other was a slow signal related to the glutamate-mediated excitatory postsynaptic potential. The location of the cochlear nerve response area was mainly located on the dorsolateral region, while that of the vestibular nerve was deviated ventromedially. At E6, cochlear nerve stimulation evoked only the fast spike-like signals in normal Ringer solution. However, when we removed Mg2+ from the extracellular solution, significant slow signals were elicited in the E6 preparation. The present results demonstrated that in the chick vestibulocochlear nuclei, functional synapses are already generated by the E7 embryonic stage and that postsynaptic activity related to N-methyl-d-aspartate receptors emerges latently, at least in the cochlear nerve-related nucleus, at the E6 embryonic stage. This chronological sequence of the emergence of postsynaptic function is different from that reported previously (E10–E11), suggesting that the developmental origin of sensory information transfer in the auditory pathway is much earlier than has been anticipated.

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Juwiler, Irit, Irina Bronfman et Natan Blaunstein. « Analysis of total signal decay and capacity of information data in wireless atmospheric communication links. Part 2 ». Information and Control Systems, n^o 1 (20 février 2020) : 54–62. http://dx.doi.org/10.31799/1684-8853-2020-1-54-62.

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Introduction: Analysis of total signal decay is based on prognosis of the total path loss occurring in the atmospheric communication links, accounting for effects of gaseous structures attenuation and scattering, hydrometeors (rain, snow and clouds) absorption and attenuation, and turbulent structures fast fading on radio and optical signals passing atmospheric channels with fading. Purpose: To perform a novel methodology of definition and estimation of effects of decay, absorption, scattering, and fading of radio and optical signals propagating in atmospheric channels in various meteorological conditions. Results: Wasanalyzed the impact of gaseous structures, hydrometeors and turbulent structures in total path loss for link budget design and in degradation of data stream parameters, such as capacity, spectral efficiency and bit-error-rate, which lead in loss of information data signals passing such kinds of channels with fast fading and decrease of quality of service. An optimal algorithm was found of the total path loss prediction for various meteorological situations occurring in the real atmosphere at different heights and for various frequencies of radiated signals. A method was proposed of how to evaluate the data stream parameters, capacity, spectralefficiency and bit-error-rate, accounting for the effects of atmospheric turbulence impact on fast fading, which corrupts information passing such kinds of channels. All practical tests were illustrated by the use of the MATLAB utility. A new methodology was proposed on how to evaluate and estimate the capacity, the spectral efficiency, and the loss in energy and in the information data stream for different scenarios of radio and optical signals propagation via atmospheric channels with fading caused by different meteorological conditions. Practical relevance: The results obtained allow to achieve better accuracy of prognosis and increase quality of service in atmospheric communication channels.

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Sato, Katsushige, Hiraku Mochida, Itaru Yazawa, Shinichi Sasaki et Yoko Momose-Sato. « Optical Approaches to Functional Organization of Glossopharyngeal and Vagal Motor Nuclei in the Embryonic Chick Hindbrain ». Journal of Neurophysiology 88, n^o 1 (1 juillet 2002) : 383–93. http://dx.doi.org/10.1152/jn.2002.88.1.383.

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We investigated the functional organization of the glossopharyngeal and vagal motor nuclei during embryogenesis using multiple-site optical recording with a fast voltage-sensitive dye. Intact brain stem preparations with glossopharyngeal and vagus nerves were dissected from 4- to 8-day-old chick embryos. Electrical responses evoked by glossopharyngeal/vagus nerve stimulation were optically recorded from many loci of the stained preparations. In 4- to 6-day-old preparations, action potential-related fast spikelike signals were detected from the nucleus of the glossopharyngeal nerve and the dorsal motor nucleus of the vagus nerve. Contour line maps of the signal amplitude showed multiple-peak patterns, suggesting that the neurons and/or their activity were not uniformly distributed within the nuclei at early developmental stages. As development proceeded from 4 to 6 days, the peaks fused with each other and the number of peaks decreased gradually. In most 7- and 8-day-old preparations, only a single peak was identified in the nuclei, and the distribution of the signal amplitude formed a layered pattern surrounding the peak-signal area. These results suggest that functional organization of the motor nuclei in the embryonic hindbrain changes dynamically with development, resulting in a rearrangement of functional nuclear cores from multiple-peaks to a single peak.

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Grant, Alexander M., et Craig S. Levin. « Optical delay encoding for fast timing and detector signal multiplexing in PET ». Medical Physics 42, n^o 8 (7 juillet 2015) : 4526–35. http://dx.doi.org/10.1118/1.4923176.

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Medvedev, Andrei V., Jana M. Kainerstorfer, Sergey V. Borisov, Amir H. Gandjbakhche et John VanMeter. « “Seeing” electroencephalogram through the skull : imaging prefrontal cortex with fast optical signal ». Journal of Biomedical Optics 15, n^o 6 (2010) : 061702. http://dx.doi.org/10.1117/1.3505007.

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Kyriakopoulos, Constantine A., Petros Nicopolitidis, Georgios I. Papadimitriou et Emmanouel Varvarigos. « Fast Energy-Efficient Design in Elastic Optical Networks Based on Signal Overlap ». IEEE Access 7 (2019) : 113931–41. http://dx.doi.org/10.1109/access.2019.2935328.

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Yin, Jiapeng, Hongliang Gong, Xu An, Zheyuan Chen, Yiliang Lu, Ian M. Andolina, Niall McLoughlin et Wei Wang. « Breaking cover : neural responses to slow and fast camouflage-breaking motion ». Proceedings of the Royal Society B : Biological Sciences 282, n^o 1813 (22 août 2015) : 20151182. http://dx.doi.org/10.1098/rspb.2015.1182.

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Primates need to detect and recognize camouflaged animals in natural environments. Camouflage-breaking movements are often the only visual cue available to accomplish this. Specifically, sudden movements are often detected before full recognition of the camouflaged animal is made, suggesting that initial processing of motion precedes the recognition of motion-defined contours or shapes. What are the neuronal mechanisms underlying this initial processing of camouflaged motion in the primate visual brain? We investigated this question using intrinsic-signal optical imaging of macaque V1, V2 and V4, along with computer simulations of the neural population responses. We found that camouflaged motion at low speed was processed as a direction signal by both direction- and orientation-selective neurons, whereas at high-speed camouflaged motion was encoded as a motion-streak signal primarily by orientation-selective neurons. No population responses were found to be invariant to the camouflage contours. These results suggest that the initial processing of camouflaged motion at low and high speeds is encoded as direction and motion-streak signals in primate early visual cortices. These processes are consistent with a spatio-temporal filter mechanism that provides for fast processing of motion signals, prior to full recognition of camouflage-breaking animals.

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Oluwole Olakunle Green, Gbenga Ayodeji Gbotoso, Samuel Okeolu Omogoye, Olufemi Sobowale Soneye, Iskeel Adekunle Sadiq et Abayomi Olukayode Ajayi. « A model of optical fiber point-to-point communication system ». International Journal of Engineering Research Updates 3, n^o 1 (30 août 2022) : 033–38. http://dx.doi.org/10.53430/ijeru.2022.3.1.0049.

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The waveguide which is considered recently for transmission of radio frequency (RF) signals from one node to another node is the optic fiber technology. The reliance on fast transmission of information can be achieved with the implementation of fiber optic cable as a waveguide in a communication channel. Basically, optic fiber transmits information with the aid of light called laser at majorly two categories of wavelengths which are 1310 nm and 1550 nm. Propagation of signal over a long stretch of fiber is affected by attenuation due to scattering, fiber bend due to impurities and absorption between the core and the cladding when signal travels along the channel, but these loses are minimal between acceptable value. Optical fiber sensors called photodetector are used to detect the information at the receiving end with minimal losses along the fiber channel. Results obtained demonstrate that there are minimal losses in a fiber cable-based signal transmission.

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Adur, Javier, Hernandes F. Carvalho, Carlos L. Cesar et Victor H. Casco. « Nonlinear Optical Microscopy Signal Processing Strategies in Cancer ». Cancer Informatics 13 (janvier 2014) : CIN.S12419. http://dx.doi.org/10.4137/cin.s12419.

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This work reviews the most relevant present-day processing methods used to improve the accuracy of multimodal nonlinear images in the detection of epithelial cancer and the supporting stroma. Special emphasis has been placed on methods of non linear optical (NLO) microscopy image processing such as: second harmonic to autofluorescence ageing index of dermis (SAAID), tumor-associated collagen signatures (TACS), fast Fourier transform (FFT) analysis, and gray level co-occurrence matrix (GLCM)-based methods. These strategies are presented as a set of potential valuable diagnostic tools for early cancer detection. It may be proposed that the combination of NLO microscopy and informatics based image analysis approaches described in this review (all carried out on free software) may represent a powerful tool to investigate collagen organization and remodeling of extracellular matrix in carcinogenesis processes.

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Zhang, Ding Qu, Rui Min Chen, Yong Xiao, Wei Ming Sun, Jia Hu et Feng Pan. « Dielectric Barrier Discharge Detection System Based on PMT ». Applied Mechanics and Materials 220-223 (novembre 2012) : 2057–63. http://dx.doi.org/10.4028/www.scientific.net/amm.220-223.2057.

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This paper puts forward a dielectric barrier discharge detection system using PMT for photoelectric element. According to faint light signal characteristics and testing purpose of dielectric barrier discharge, this system is designed, including three parts: optical fiber transmission, photoelectric conversion and signal processing circuit. This paper introduces design and ideas of the system framework and presents circuit design parameter. Results in atmospheric pressure of dielectric barrier discharge detection experiment show that the system has high sensitivity, fast response, can effectively distinguish discharge and interference signals, gather more signals in different areas.

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Křen, Petr. « Laser frequency counting and frequency modulation width measurement from a fft signal ». Metrology and Measurement Systems 19, n^o 3 (1 octobre 2012) : 565–72. http://dx.doi.org/10.2478/v10178-012-0049-0.

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Abstract A new method of optical frequency beat counting based on fast Fourier transform (FFT) analysis is described. Signals with a worse signal-to-noise ratio can be counted correctly comparing to the conventional counting method of detecting each period separately. The systematic error of FFT counting below 10 Hz is demonstrated and can be decreased. Additionally the modulation width of a frequency-stabilized laser with high frequency modulation index can be simultaneously measured during a carrier frequency measurement against an optical frequency synthesizer or other laser.

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WABNITZ, S. « SIGNAL PROCESSING IN PHOTONIC CRYSTALS AND NANOSTRUCTURES ». Journal of Nonlinear Optical Physics & ; Materials 15, n^o 01 (mars 2006) : 55–76. http://dx.doi.org/10.1142/s0218863506003165.

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Optical devices employing photonic crystals and novel nanostructure materials may exhibit useful properties for applications to all-optical signal processing. In this work we analyze as a first example four-wave mixing of polarized beams in photonic crystal fibers. We show that by properly tuning the pump wavelength and the linear dispersion properties of the fiber one may obtain broadband parametric amplification and frequency conversion. Next we consider the in-line periodic amplification of short optical pulses by means of quantum-dot semiconductor optical amplifiers. We show by numerical simulations that pattern-free amplification of a 40 Gbit/s soliton signal at 1300 nm is possible without any inter-symbol interference or nonlinear pulse distortion caused by the fast gain dynamics.

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Wang Yu, 王宇, 吴腾飞 Wu Tengfei, 周强 Zhou Qiang, 赵晖 Zhao Hui et 邾继贵 Zhu Jigui. « 光频扫描干涉测距信号快速采集与处理方法 ». Laser & ; Optoelectronics Progress 60, n^o 1 (2023) : 0107003. http://dx.doi.org/10.3788/lop212911.

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Kawanishi, Tetsuya. « Precise Optical Modulation and Its Application to Optoelectronic Device Measurement ». Photonics 8, n^o 5 (11 mai 2021) : 160. http://dx.doi.org/10.3390/photonics8050160.

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Optoelectronic devices which play important roles in high-speed optical fiber networks can offer effective measurement methods for optoelectronic devices including optical modulators and photodetectors. Precise optical signal modulation is required for measurement applications. This paper focuses on high-speed and precise optical modulation devices and their application to device measurement. Optical modulators using electro-optic effect offers precise control of lightwaves for wideband signals. As examples, this paper describes frequency response measurement of photodetectors using high-precision amplitude modulation and wavelength domain measurement of optical filters using fast optical frequency sweep. Precise and high-speed modulation can be achieved by active trimming which compensates device structure imbalance due to fabrication error, where preciseness can be described by on-off extinction ratio. A Mach-Zehnder modulator with sub Mach-Zehnder interferometors can offer high extinction-ratio optical intensity modulation, which can be used for precise optoelectronic frequency response measurement. Precise modulation would be also useful for multi-level modulation schemes. To investigate impact of finite extinction ratio on optical modulation, duobinary modulation with small signal operation was demonstrated. For optical frequency domain analysis, single sideband modulation, which shifts optical frequency, can be used for generation of stimulus signals. Rapid measurement of optical filters was performed by using an optical sweeper consisting of an integrated Mach-Zehnder modulator for optical frequency control and an arbitrary waveform generator for generation of a source frequency chirp signal.

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Duan, Qianwen, Qiunong He, Yao Mao, Xi Zhou et Qintao Hu. « Proximate Time-Optimal Servomechanism Based on Transition Process for Electro-Optical Set-Point Tracking Servo System ». Applied Sciences 9, n^o 23 (29 novembre 2019) : 5201. http://dx.doi.org/10.3390/app9235201.

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Set-point tracking servo systems encounter the problem of the trade-off between the swiftness and smoothness in tracking task. To deal with this problem, the proximate time-optimal servomechanism based on transition process (PTSTP) is proposed in this paper. The PTSTP control scheme incorporates a transition process (TP) into the framework of proximate time-optimal servomechanism (PTOS) to eliminate the conservatism of the original PTOS without the controller changing. The target position signal amplitude and the ultimate ability of actuator are utilized to design the time-optimal TP to make the jumping target position signal turns to a smooth signal, which can significantly reduce system overshoot. Therefore, the system swiftness and smoothness performance are guaranteed by PTSTP. Then, the stability of the proposed method is analyzed theoretically. Finally, the experimental results show that the controlled system is able to track the target position signal with different amplitude fast and smoothly in an electro-optical set-point tracking servo system.

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Ma, Peilan. « Photoelectric Vibration Monitoring System Using Optical Fiber Sensing/Mathematical Modeling ». Journal of Nanoelectronics and Optoelectronics 17, n^o 7 (1 juillet 2022) : 1073–80. http://dx.doi.org/10.1166/jno.2022.3275.

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The optical fiber vibration monitoring system is designed, and the optical fiber with strong anti-interference performance, high stability and corrosion resistance is used as the sensor. Mach-Zehnder with high sensitivity is used for interference counting, and embedded technology is introduced. The extracted spectral characteristics of optical fiber signals are used for pattern recognition through a mathematical modeling method. In the hardware design, embedded technology is introduced. Multi-channel AD collects data, and the processed optical fiber data are communicated with the master computer through the high-speed network port to realize the data transmission without breakpoints, and then reduce the development cost. Fast Fourier transform (FFT) is used as the research method of mathematical modeling in optical fiber signal processing and is improved. The new algorithm can analyze the vibration signal from the frequency domain. In the test, one group of intrusion vibration signals and one group of ordinary vibration signals are taken as the test objects. The results show that the improved mathematical modeling method will not have the situation of false intrusion alarm, nor will it have the situation of common false alarm. Using this algorithm in the vibration monitoring system of optical fiber sensors can accurately identify intrusion signals to distinguish the intrusion vibration situation from the ordinary vibration situation.

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Nahaei, Farshad Serat, Ali Rostami et Peyman Mirtaheri. « Quantum Dot Reflective Semiconductor Optical Amplifiers : Optical Pumping Compared with Electrical Pumping ». Nanomaterials 12, n^o 13 (22 juin 2022) : 2143. http://dx.doi.org/10.3390/nano12132143.

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A comprehensive study has been conducted on quantum dot reflective semiconductor optical amplifiers (QD-RSOAs) with optical pumps (OPs). Moreover, few studies have been completed on OP-based QD-RSOAs. A comparison is made between them and QD-RSOAs with electrical pumps (EPs) in this study. It is shown that the dynamical properties of the device can significantly develop in the optical pumping version. The optical properties are studied for both methods. Moreover, by solving the coupled differential rate and signal propagation equations, the operation of the device in the pulse mode is investigated. Finally, it is proven that OP QD-RSOAs can perform significantly better in applications such as fast all-optical signal processing and wavelength division multiplexing in passive optical networks.

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Liu, Yi, Haimiao Long, Ming Chen, Yun Cheng et Taoyun Zhou. « Probabilistically-Shaped DMT for IM-DD Systems with Low-Complexity Fast WHT-Based PDSP ». Photonics 9, n^o 9 (15 septembre 2022) : 655. http://dx.doi.org/10.3390/photonics9090655.

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Transmission capacity and receiver sensitivity of an intensity-modulation direct detection (IM-DD) optical discrete multi-tone (DMT) system can be improved by using the probabilistically shaping (PS) technique. However, different probabilistic distributions will be required owing to the unbalanced signal-to-noise ratio (SNR) among data-carrying subcarriers (SCs) induced by the imperfect frequency response of optical/electrical devices, which can increase the implementation complexity of the PS-DMT transceiver. In this work, different signal pre-processing schemes including pre-equalization, Walsh–Hadamard transform (WHT)-based full data-carrying SCs precoding (FDSP) and fast WHT-based partial data-carrying SCs precoding (PDSP) are investigated for SNR equalization in a short-reach PS-DMT transmission system. After transmission over 50 km single-mode fiber, the experimental results indicated that three pre-processed signals have almost the same generalized mutual information (GMI) performance and receiver sensitivity improvements. The proposed fast WHT-based PDSP scheme may be a good option for the implementation of the PS-DMT transmission systems with a large SC SNR fluctuation regarding computational complexity.

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Chiuri, Andrea, et Federico Angelini. « Fast Gating for Raman Spectroscopy ». Sensors 21, n^o 8 (7 avril 2021) : 2579. http://dx.doi.org/10.3390/s21082579.

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Fast gating in Raman spectroscopy is used to reject the fluorescence contribution from the sample and/or the substrate. Several techniques have been set up in the last few decades aiming either to enhance the Raman signal (CARS, SERS or Resonant Raman scattering) or to cancel out the fluorescence contribution (SERDS), and a number of reviews have already been published on these sub-topics. However, for many reasons it is sometimes necessary to reject fluorescence in traditional Raman spectroscopy, and in the last few decades a variety of papers dealt with this issue, which is still challenging due to the time scales at stake (down to picoseconds). Fast gating (<1 ns) in the time domain allows one to cut off part of the fluorescence signal and retrieve the best Raman signal, depending on the fluorescence lifetime of the sample and laser pulse duration. In particular, three different techniques have been developed to accomplish this task: optical Kerr cells, intensified Charge Coupling Devices and systems based on Single Photon Avalanche Photodiodes. The utility of time domain fast gating will be discussed, and In this work, the utility of time domain fast gating is discussed, as well as the performances of the mentioned techniques as reported in literature.

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Zhang, Hongying, Dengwang Zhou, Benzhang Wang, Chao Pang, Pengbai Xu, Taofei Jiang, Dexin Ba, Hui Li et Yongkang Dong. « Recent Progress in Fast Distributed Brillouin Optical Fiber Sensing ». Applied Sciences 8, n^o 10 (4 octobre 2018) : 1820. http://dx.doi.org/10.3390/app8101820.

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Brillouin-based optical fiber sensing has been regarded as a good distributed measurement tool for the modern large geometrical structure and the industrial facilities because it can demodulate the distributed environment information (e.g., temperature and strain) along the sensing fiber. Brillouin optical time domain analysis (BOTDA), which is an excellent and attractive scheme, has been widely developed thanks to its high performance in a signal-to-noise ratio, a spatial resolution, and sensing distance. However, the sampling rate of the classical BOTDA is severely limited by several factors (especially the serially frequency-sweeping process) so that it cannot be suitable for the quickly distributed measurement. In this work, we summarize some promising breakthroughs about the fast BOTDA, which can be named as an optical frequency comb technique, an optical frequency-agile technique, a slope-assisted technique, and an optical chirp chain technique.

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Vartsky, D., G. Feldman, I. Mor, M. B. Goldberg, D. Bar et V. Dangendorf. « Signal and noise analysis in TRION—Time-Resolved Integrative Optical Fast Neutron detector ». Journal of Instrumentation 4, n^o 02 (16 février 2009) : P02001. http://dx.doi.org/10.1088/1748-0221/4/02/p02001.

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Jin, Yun-Sik, Seok-Gy Jeon, Geun-Ju Kim, Jung-Il Kim et Chae-Hwa Shon. « Fast scanning of a pulsed terahertz signal using an oscillating optical delay line ». Review of Scientific Instruments 78, n^o 2 (février 2007) : 023101. http://dx.doi.org/10.1063/1.2437764.

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Lu, Haidong D., Gang Chen, Junjie Cai et Anna W. Roe. « Intrinsic signal optical imaging of visual brain activity : Tracking of fast cortical dynamics ». NeuroImage 148 (mars 2017) : 160–68. http://dx.doi.org/10.1016/j.neuroimage.2017.01.006.

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Chiarelli, Antonio Maria, Assunta Di Vacri, Gian Luca Romani et Arcangelo Merla. « Fast optical signal in visual cortex : Improving detection by General Linear Convolution Model ». NeuroImage 66 (février 2013) : 194–202. http://dx.doi.org/10.1016/j.neuroimage.2012.10.047.

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Lorenz, E., R. Maier, T. S. Tran et P. Weissbach. « A fast, large dynamic range analog signal transfer system based on optical fibers ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 461, n^o 1-3 (avril 2001) : 517–20. http://dx.doi.org/10.1016/s0168-9002(00)01288-2.

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Rose, Joachim, Isobel Bond, Albrecht Karle, Eckart Lorenz, Si Tran et Peter Weißbach. « Fast analog signal transmission for an air Cherenkov photomultiplier camera using optical fibers ». Nuclear Instruments and Methods in Physics Research Section A : Accelerators, Spectrometers, Detectors and Associated Equipment 442, n^o 1-3 (mars 2000) : 113–16. http://dx.doi.org/10.1016/s0168-9002(99)01207-3.

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Mahmoudzadeh, Mahdi, Mana Manoochehri et Fabrice Wallois. « P366 Multimodal EEG/ECOG and fast optical signal measurements in interictal epileptic spikes ». Clinical Neurophysiology 128, n^o 9 (septembre 2017) : e296-e297. http://dx.doi.org/10.1016/j.clinph.2017.07.374.

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Liu, Jingfeng, Hongwei Song et B. V. K. Vijaya Kumar. « Fast Timing Acquisition for Low Signal-to-Noise Ratio High Density Optical Recording ». Japanese Journal of Applied Physics 41, Part 1, No. 3B (30 mars 2002) : 1772–76. http://dx.doi.org/10.1143/jjap.41.1772.

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Cinelli, A. R., et B. M. Salzberg. « Dendritic origin of late events in optical recordings from salamander olfactory bulb ». Journal of Neurophysiology 68, n^o 3 (1 septembre 1992) : 786–806. http://dx.doi.org/10.1152/jn.1992.68.3.786.

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1. Optical recordings of membrane-potential changes were used to characterize the origin and properties of the electrical signals from the dendritic level in slices of the salamander olfactory bulb. 2. The optical events were correlated with field-potential waves recorded simultaneously. Both responses exhibited patterns similar to those found in other species. 3. Orthodromic stimulation evoked a compound action potential in the olfactory nerve fibers, followed by two additional principal waves (N1 and N2). These field-potential waves reflected excitatory postsynaptic potentials at the primary mitral/tufted and granule cell dendrites, respectively. 4. Extrinsic optical signals from horizontal slices stained with the pyrazo-oxonal dye RH-155 showed a characteristic sequence of depolarizing and hyperpolarizing events. All of the signals exhibited a wavelength dependence expected for this dye and were abolished in the presence of high K+ in the bath. 5. According to their time courses, depolarizing responses under normal recording conditions were divided into two components, fast and slow. Orthodromic stimuli evoked a fast presynaptic response that represents synchronous compound action potentials from olfactory nerve fibers. At subglomerular levels, additional fast responses could often be recorded at the peri/subglomerular level and in the mitral/tufted somata region. These postsynaptic responses partially coincided with the rising phase of a different depolarizing signal, a slow component characterized by its prolonged time course. 6. With orthodromic stimulation, this slow signal attained its largest amplitude in the zone between the glomeruli and the superficial part of the external plexiform layer (EPL). Antidromic stimuli evoked a signal with some similarities to the one evoked orthodromically, but originating in deeper EPL regions. 7. Slow components were characterized by their Ca dependence. Low Ca2+ medium, or calcium channel blockers, suppressed this optical component, whether evoked orthodromically, antidromically, or by direct stimulation. In addition, Ba2+ (2.5–3.6 mM) in the bath did not abolish these responses, suggesting that they do not reflect a glial depolarization in response to elevated extracellular K+ concentration ([K+]o). 8. Locally applied stimuli next to the glomerular layer elicited these signals in 5–10 microM tetrodotoxin (TTX) or in low extracellular Na+ concentration ([Na+]o) medium, but antidromic or orthodromic stimuli failed to evoke the response under these conditions. The sizes of the responses to local stimuli remained constant, but an increase in their duration was observed in either TTX or low [Na+]o. 9. gamma-Aminobutyric acid (GABA) and baclofen reduced the size of the slow components in a dose-dependent manner.(ABSTRACT TRUNCATED AT 400 WORDS)

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Stilgoe, Alexander B., Declan J. Armstrong et Halina Rubinsztein-Dunlop. « Enhanced Signal-to-Noise and Fast Calibration of Optical Tweezers Using Single Trapping Events ». Micromachines 12, n^o 5 (17 mai 2021) : 570. http://dx.doi.org/10.3390/mi12050570.

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The trap stiffness us the key property in using optical tweezers as a force transducer. Force reconstruction via maximum-likelihood-estimator analysis (FORMA) determines the optical trap stiffness based on estimation of the particle velocity from statistical trajectories. Using a modification of this technique, we determine the trap stiffness for a two micron particle within 2 ms to a precision of ∼10% using camera measurements at 10 kfps with the contribution of pixel noise to the signal being larger the level Brownian motion. This is done by observing a particle fall into an optical trap once at a high stiffness. This type of calibration is attractive, as it avoids the use of a nanopositioning stage, which makes it ideal for systems of large numbers of particles, e.g., micro-fluidics or active matter systems.

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Li, Ziwei, Qinrong Zhang, Shih-Wei Chou, Zachary Newman, Raphaël Turcotte, Ryan Natan, Qionghai Dai, Ehud Y. Isacoff et Na Ji. « Fast widefield imaging of neuronal structure and function with optical sectioning in vivo ». Science Advances 6, n^o 19 (mai 2020) : eaaz3870. http://dx.doi.org/10.1126/sciadv.aaz3870.

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Optical microscopy, owing to its noninvasiveness and subcellular resolution, enables in vivo visualization of neuronal structure and function in the physiological context. Optical-sectioning structured illumination microscopy (OS-SIM) is a widefield fluorescence imaging technique that uses structured illumination patterns to encode in-focus structures and optically sections 3D samples. However, its application to in vivo imaging has been limited. In this study, we optimized OS-SIM for in vivo neural imaging. We modified OS-SIM reconstruction algorithms to improve signal-to-noise ratio and correct motion-induced artifacts in live samples. Incorporating an adaptive optics (AO) module to OS-SIM, we found that correcting sample-induced optical aberrations was essential for achieving accurate structural and functional characterizations in vivo. With AO OS-SIM, we demonstrated fast, high-resolution in vivo imaging with optical sectioning for structural imaging of mouse cortical neurons and zebrafish larval motor neurons, and functional imaging of quantal synaptic transmission at Drosophila larval neuromuscular junctions.

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Schmoderer, Timothée, Angelica I. Aviles-Rivero, Veronica Corona, Noémie Debroux et Carola-Bibiane Schönlieb. « Learning optical flow for fast MRI reconstruction ». Inverse Problems 37, n^o 9 (10 août 2021) : 095007. http://dx.doi.org/10.1088/1361-6420/ac164a.

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CHENG, L. J., D. T. H. LIU et K. L. LUKE. « OPTICAL PROCESSING WITH PHOTOREFRACTIVE COMPOUND SEMICONDUCTORS ». Journal of Nonlinear Optical Physics & ; Materials 01, n^o 03 (juillet 1992) : 609–38. http://dx.doi.org/10.1142/s0218199192000303.

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Photorefractive compound semiconductors are attractive for optical processing because of fast material response, compatibility with semiconductor lasers, and availability of cross polarization diffraction for enhancing signal-to-noise ratio. This paper presents a collection of recent experimental results on optical processing using photorefractive GaAs and InP. The results demonstrate the feasibility of using photorefractive compound semiconductors as dynamic holographic interaction media for optical processing applications.

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Srivastava, V., et R. G. Carter. « A fast large-signal model for coupled-cavity TWTs ». IEEE Transactions on Electron Devices 35, n^o 11 (novembre 1988) : 2068–76. http://dx.doi.org/10.1109/16.7429.

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Voronine, Dmitri V., Zhenrong Zhang, Alexei V. Sokolov et Marlan O. Scully. « Surface-enhanced FAST CARS : en route to quantum nano-biophotonics ». Nanophotonics 7, n^o 3 (23 février 2018) : 523–48. http://dx.doi.org/10.1515/nanoph-2017-0066.

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AbstractQuantum nano-biophotonics as the science of nanoscale light-matter interactions in biological systems requires developing new spectroscopic tools for addressing the challenges of detecting and disentangling weak congested optical signals. Nanoscale bio-imaging addresses the challenge of the detection of weak resonant signals from a few target biomolecules in the presence of the nonresonant background from many undesired molecules. In addition, the imaging must be performed rapidly to capture the dynamics of biological processes in living cells and tissues. Label-free non-invasive spectroscopic techniques are required to minimize the external perturbation effects on biological systems. Various approaches were developed to satisfy these requirements by increasing the selectivity and sensitivity of biomolecular detection. Coherent anti-Stokes Raman scattering (CARS) and surface-enhanced Raman scattering (SERS) spectroscopies provide many orders of magnitude enhancement of chemically specific Raman signals. Femtosecond adaptive spectroscopic techniques for CARS (FAST CARS) were developed to suppress the nonresonant background and optimize the efficiency of the coherent optical signals. This perspective focuses on the application of these techniques to nanoscale bio-imaging, discussing their advantages and limitations as well as the promising opportunities and challenges of the combined coherence and surface enhancements in surface-enhanced coherent anti-Stokes Raman scattering (SECARS) and tip-enhanced coherent anti-Stokes Raman scattering (TECARS) and the corresponding surface-enhanced FAST CARS techniques. Laser pulse shaping of near-field excitations plays an important role in achieving these goals and increasing the signal enhancement.

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Heimersheim, Stefan, Nina S. Sartorio, Anastasia Fialkov et Duncan R. Lorimer. « What It Takes to Measure Reionization with Fast Radio Bursts ». Astrophysical Journal 933, n^o 1 (1 juillet 2022) : 57. http://dx.doi.org/10.3847/1538-4357/ac70c9.

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Abstract Fast Radio Bursts (FRBs) are extragalactic radio transients that exhibit a distance-dependent dispersion of their signal, and thus can be used as cosmological probes. In this article we, for the first time, apply a model-independent approach to measure reionization from synthetic FRB data assuming these signals are detected beyond redshift 5. This method allows us to constrain the full shape of the reionization history as well as the CMB optical depth τ while avoiding the problems of commonly used model-based techniques. A total of 100 localized FRBs, originating from redshifts 5–15, could constrain (at 68% confidence level) the CMB optical depth to within 11%, and the midpoint of reionization to 4%, surpassing current state-of-the-art CMB bounds and quasar limits. Owing to the higher numbers of expected FRBs at lower redshifts, the τ constraints are asymmetric (+14%, −7%), providing a much stronger lower limit. Finally, we show that the independent constraints on reionization from FRBs will improve limits on other cosmological parameters, such as the amplitude of the power spectrum of primordial fluctuations.

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