Artículos de revistas: "Event Related Optical Signal"

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Maclin, Edward L., Kathy A. Low, Monica Fabiani y Gabriele Gratton. "Improving the signal-to-noise ratio of event-related optical signals". IEEE Engineering in Medicine and Biology Magazine 26, n.º 4 (julio de 2007): 47–51. http://dx.doi.org/10.1109/memb.2007.384095.

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Tse, Chun-Yu y Trevor B. Penney. "Preattentive change detection using the event-related optical signal". IEEE Engineering in Medicine and Biology Magazine 26, n.º 4 (julio de 2007): 52–58. http://dx.doi.org/10.1109/memb.2007.384096.

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3

Gratton, Gabriele y Monica Fabiani. "Shedding light on brain function: the event-related optical signal". Trends in Cognitive Sciences 5, n.º 8 (agosto de 2001): 357–63. http://dx.doi.org/10.1016/s1364-6613(00)01701-0.

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Maclin, Edward L., Kathy A. Low, Jeffrey J. Sable, Monica Fabiani y Gabriele Gratton. "The event-related optical signal to electrical stimulation of the median nerve". NeuroImage 21, n.º 4 (abril de 2004): 1798–804. http://dx.doi.org/10.1016/j.neuroimage.2003.11.019.

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5

Gratton, Gabriele y Monica Fabiani. "The event-related optical signal: a new tool for studying brain function". International Journal of Psychophysiology 42, n.º 2 (octubre de 2001): 109–21. http://dx.doi.org/10.1016/s0167-8760(01)00161-1.

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Tse, C. Y., C. L. Lee, J. Sullivan, S. M. Garnsey, G. S. Dell, M. Fabiani y G. Gratton. "Imaging cortical dynamics of language processing with the event-related optical signal". Proceedings of the National Academy of Sciences 104, n.º 43 (17 de octubre de 2007): 17157–62. http://dx.doi.org/10.1073/pnas.0707901104.

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7

Gratton, Gabriele y Monica Fabiani. "The event-related optical signal (EROS) in visual cortex: Replicability, consistency, localization, and resolution". Psychophysiology 40, n.º 4 (julio de 2003): 561–71. http://dx.doi.org/10.1111/1469-8986.00058.

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8

Proulx, Nicole, Ali-Akbar Samadani y Tom Chau. "Quantifying fast optical signal and event-related potential relationships during a visual oddball task". NeuroImage 178 (septiembre de 2018): 119–28. http://dx.doi.org/10.1016/j.neuroimage.2018.05.031.

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9

GRATTON, GABRIELE, MONICA FABIANI, MARSHA R. GOODMAN-WOOD y M. CATHERINE DESOTO. "Memory-driven processing in human medial occipital cortex: An event-related optical signal (EROS) study". Psychophysiology 35, n.º 3 (mayo de 1998): 348–51. http://dx.doi.org/10.1017/s0048577298001292.

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10

Gratton, Gabriele y Monica Fabiani. "Dynamic brain imaging: Event-related optical signal (EROS) measures of the time course and localization of cognitive-related activity". Psychonomic Bulletin & Review 5, n.º 4 (diciembre de 1998): 535–63. http://dx.doi.org/10.3758/bf03208834.

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11

Arieli, A., D. Shoham, R. Hildesheim y A. Grinvald. "Coherent spatiotemporal patterns of ongoing activity revealed by real-time optical imaging coupled with single-unit recording in the cat visual cortex". Journal of Neurophysiology 73, n.º 5 (1 de mayo de 1995): 2072–93. http://dx.doi.org/10.1152/jn.1995.73.5.2072.

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1. We examined the spatiotemporal organization of ongoing activity in cat visual areas 17 and 18, in relation to the spontaneous activity of individual neurons. To search for coherent activity, voltage-sensitive dye signals were correlated with the activity of single neurons by the use of spike-triggered averaging. In each recording session an area of at least 2 x 2 mm of cortex was imaged, with 124 diodes. In addition, electrical recordings from two isolated units, the local field potential (LFP) from the same microelectrodes, and the surface electroencephalogram (EEG) were recorded simultaneously. 2. The optical signals recorded from the dye were similar to the LFP recorded from the same site. Optical signals recorded from different cortical sites exhibited a different time course. Therefore real-time optical imaging provides information that is equivalent in many ways to multiple-site LFP recordings. 3. The spontaneous firing of single neurons was highly correlated with the optical signals and with the LFP. In 88% of the neurons recorded during spontaneous activity, a significant correlation was found between the occurrence of a spike and the optical signal recorded in a large cortical region surrounding the recording site. This result indicates that spontaneous activity of single neurons is not an independent process but is time locked to the firing or to the synaptic inputs from numerous neurons, all activated in a coherent fashion even without a sensory input. 4. For the cases showing correlation with the optical signal, 27-36% of the optical signal during spike occurrence was directly related to the occurrence of spontaneous spikes in a single neuron, over an area of 2 x 2 mm. In the same cortical area, 43-55% of the activity was directly related to the visual stimulus. 5. Surprisingly, we found that the amplitude of this coherent ongoing activity, recorded optically, was often almost as large as the activity evoked by optimal visual stimulation. The amplitude of the ongoing activity that was directly and reproducibly related to the spontaneous spikes of a single neuron was, on average, as high as 54% of the amplitude of the visually evoked response that was directly related to optimal sensory stimulation, recorded optically. 6. Coherent activity was detected even at distant cortical sites up to 6 mm apart.(ABSTRACT TRUNCATED AT 400 WORDS)

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12

Tabi Fouda, Bernard Marie, Dezhi Han, Bowen An, Xuejia Lu y Qiuting Tian. "Events detection and recognition by the fiber vibration system based on power spectrum estimation". Advances in Mechanical Engineering 10, n.º 11 (noviembre de 2018): 168781401880867. http://dx.doi.org/10.1177/1687814018808679.

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One of the important successes of optical fiber sensor established for the security system is the detection and the recognition of any type of events. The performance parameters (event recognition, event detection position, and time of detection) are unavoidable and describe the validity of any perimeter detection system. An event recognition is any signal detected within the protected area, and it is related to a non-intrusion event and an intrusion event. To achieve the detection and the recognition events at the real time, an effective two-level vibration recognition method and a technique are proposed and presented in this article. The signal characteristics (short-term energy and short-time over-threshold) have been used and compared to the dynamic threshold to judge the type of event. Then the extraction of the power distribution features on the frequency domain through power spectral estimation on the suspected intrusion signal samples is carried out and finally combined with the time-domain characteristics as feature vector through Support Vector Machine to determine the efficiency and effectiveness of the proposed vibration recognition method. The experimental simulation results show that the proposed method is effective and reliable. With collected data, it can detect and recognize the type of event in real time.

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13

Xiao, Xue-Zhen, Yang Wang, Geoffrey Chun-Sung Wong, Kunyang Zhao y Chun-Yu Tse. "Frontotemporal network in automatic / pre-attentive detection of abstract change: An event-related optical signal (EROS) study". Neuropsychologia 164 (enero de 2022): 108093. http://dx.doi.org/10.1016/j.neuropsychologia.2021.108093.

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Mathewson, K., D. Beck, T. Ro, M. Fabiani y G. Gratton. "Illuminating awareness: Investigating the temporal and spatial neural dynamics of metacontrast masking using the event-related optical signal". Journal of Vision 9, n.º 8 (3 de septiembre de 2010): 765. http://dx.doi.org/10.1167/9.8.765.

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15

Medvedev, Andrei V., Jana Kainerstorfer, Sergey V. Borisov, Randall L. Barbour y John VanMeter. "Event-related fast optical signal in a rapid object recognition task: Improving detection by the independent component analysis". Brain Research 1236 (octubre de 2008): 145–58. http://dx.doi.org/10.1016/j.brainres.2008.07.122.

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Hajra, Sujoy Ghosh, Careesa C. Liu, Shaun D. Fickling, Gabriela M. Pawlowski, Xiaowei Song y Ryan C. N. D’Arcy. "Event Related Potential Signal Capture Can Be Enhanced through Dynamic SNR-Weighted Channel Pooling". Sensors 21, n.º 21 (31 de octubre de 2021): 7258. http://dx.doi.org/10.3390/s21217258.

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Background: Electroencephalography (EEG)-derived event-related potentials (ERPs) provide information about a variety of brain functions, but often suffer from low inherent signal-to-noise ratio (SNR). To overcome the low SNR, techniques that pool data from multiple sensors have been applied. However, such pooling implicitly assumes that the SNR among sensors is equal, which is not necessarily valid. This study presents a novel approach for signal pooling that accounts for differential SNR among sensors. Methods: The new technique involves pooling together signals from multiple EEG channels weighted by their respective SNRs relative to the overall SNR of all channels. We compared ERP responses derived using this new technique with those derived using both individual channels as well as traditional averaged-based channel pooling. The outcomes were evaluated in both simulated data and real data from healthy adult volunteers (n = 37). Responses corresponding to a range of ERP components indexing auditory sensation (N100), attention (P300) and language processing (N400) were evaluated. Results: Simulation results demonstrate that, compared to traditional pooling technique, the new SNR-weighted channel pooling technique improved ERP response effect size in cases of unequal noise among channels (p’s < 0.001). Similarly, results from real-world experimental data showed that the new technique resulted in significantly greater ERP effect sizes compared to either traditional pooling or individual channel approach for all three ERP components (p’s < 0.001). Furthermore, the new channel pooling approach also resulted in larger ERP signal amplitudes as well as greater differences among experimental conditions (p’s < 0.001). Conclusion: These results suggest that the new technique improves the capture of ERP responses relative to traditional techniques. As such, SNR-weighted channel pooling can further enable widespread applications of ERP techniques, especially those that require rapid assessments in noisy out-of-laboratory environments.

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Huang, Jian, Suiping Wang, Shiwei Jia, Deyuan Mo y Hsuan-Chih Chen. "Cortical Dynamics of Semantic Processing during Sentence Comprehension: Evidence from Event-Related Optical Signals". PLoS ONE 8, n.º 8 (1 de agosto de 2013): e70671. http://dx.doi.org/10.1371/journal.pone.0070671.

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Yan, Yuling, M. Emma Marriott, Chutima Petchprayoon y Gerard Marriott. "Optical switch probes and optical lock-in detection (OLID) imaging microscopy: high-contrast fluorescence imaging within living systems". Biochemical Journal 433, n.º 3 (14 de enero de 2011): 411–22. http://dx.doi.org/10.1042/bj20100992.

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Few to single molecule imaging of fluorescent probe molecules can provide information on the distribution, dynamics, interactions and activity of specific fluorescently tagged proteins during cellular processes. Unfortunately, these imaging studies are made challenging in living cells because of fluorescence signals from endogenous cofactors. Moreover, related background signals within multi-cell systems and intact tissue are even higher and reduce signal contrast even for ensemble populations of probe molecules. High-contrast optical imaging within high-background environments will therefore require new ideas on the design of fluorescence probes, and the way their fluorescence signals are generated and analysed to form an image. To this end, in the present review we describe recent studies on a new family of fluorescent probe called optical switches, with descriptions of the mechanisms that underlie their ability to undergo rapid and reversible transitions between two distinct states. Optical manipulation of the fluorescent and non-fluorescent states of an optical switch probe generates a modulated fluorescence signal that can be isolated from a larger unmodulated background by using OLID (optical lock-in detection) techniques. The present review concludes with a discussion on select applications of synthetic and genetically encoded optical switch probes and OLID microscopy for high-contrast imaging of specific proteins and membrane structures within living systems.

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Mathewson, Kyle E., Diane M. Beck, Tony Ro, Edward L. Maclin, Kathy A. Low, Monica Fabiani y Gabriele Gratton. "Dynamics of Alpha Control: Preparatory Suppression of Posterior Alpha Oscillations by Frontal Modulators Revealed with Combined EEG and Event-related Optical Signal". Journal of Cognitive Neuroscience 26, n.º 10 (octubre de 2014): 2400–2415. http://dx.doi.org/10.1162/jocn_a_00637.

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We investigated the dynamics of brain processes facilitating conscious experience of external stimuli. Previously, we proposed that alpha (8–12 Hz) oscillations, which fluctuate with both sustained and directed attention, represent a pulsed inhibition of ongoing sensory brain activity. Here we tested the prediction that inhibitory alpha oscillations in visual cortex are modulated by top–down signals from frontoparietal attention networks. We measured modulations in phase-coherent alpha oscillations from superficial frontal, parietal, and occipital cortices using the event-related optical signal (EROS), a measure of neuronal activity affording high spatiotemporal resolution, along with concurrently recorded EEG, while participants performed a visual target detection task. The pretarget alpha oscillations measured with EEG and EROS from posterior areas were larger for subsequently undetected targets, supporting alpha's inhibitory role. Using EROS, we localized brain correlates of these awareness-related alpha oscillations measured at the scalp to the cuneus and precuneus. Crucially, EROS alpha suppression correlated with posterior EEG alpha power across participants. Sorting the EROS data based on EEG alpha power quartiles to investigate alpha modulators revealed that suppression of posterior alpha was preceded by increased activity in regions of the dorsal attention network and decreased activity in regions of the cingulo-opercular network. Cross-correlations revealed the temporal dynamics of activity within these preparatory networks before posterior alpha modulation. The novel combination of EEG and EROS afforded localization of the sources and correlates of alpha oscillations and their temporal relationships, supporting our proposal that top–down control from attention networks modulates both posterior alpha and awareness of visual stimuli.

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Tse, Chun-Yu, Long-Yin Yip, Troby Ka-Yan Lui, Xue-Zhen Xiao, Yang Wang, Winnie Chiu Wing Chu, Nathan Allen Parks, Sandra Sau-Man Chan y Sebastiaan Franciscus Wijnandus Neggers. "Establishing the functional connectivity of the frontotemporal network in pre-attentive change detection with Transcranial Magnetic Stimulation and event-related optical signal". NeuroImage 179 (octubre de 2018): 403–13. http://dx.doi.org/10.1016/j.neuroimage.2018.06.053.

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21

Gratton, Gabriele, Anita Sarno, Ed Maclin, Paul M. Corballis y Monica Fabiani. "Toward Noninvasive 3-D Imaging of the Time Course of Cortical Activity: Investigation of the Depth of the Event-Related Optical Signal". NeuroImage 11, n.º 5 (mayo de 2000): 491–504. http://dx.doi.org/10.1006/nimg.2000.0565.

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Baniqued, Pauline L., Kathy A. Low, Monica Fabiani y Gabriele Gratton. "Frontoparietal Traffic Signals: A Fast Optical Imaging Study of Preparatory Dynamics in Response Mode Switching". Journal of Cognitive Neuroscience 25, n.º 6 (junio de 2013): 887–902. http://dx.doi.org/10.1162/jocn_a_00341.

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Coordination between networks of brain regions is important for optimal cognitive performance, especially in attention demanding tasks. With the event-related optical signal (a measure of changes in optical scattering because of neuronal activity) we can characterize rapidly evolving network processes by examining the millisecond-scale temporal correlation of activity in distinct regions during the preparatory period of a response mode switching task. Participants received a precue indicating whether to respond vocally or manually. They then saw or heard the letter “L” or “R,” indicating a “left” or “right” response to be implemented with the appropriate response modality. We employed lagged cross-correlations to characterize the dynamic connectivity of preparatory processes. Our results confirmed coupling of frontal and parietal cortices and the trial-dependent relationship of the right frontal cortex with response preparation areas. The frontal-to-modality-specific cortex cross-correlations revealed a pattern in which first irrelevant regions were deactivated, and then relevant regions were activated. These results provide a window into the subsecond scale network interactions that flexibly tune to task demands.

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Spurbeck, Justin, Moriba K. Jah, Daniel Kucharski, James C. S. Bennett y James G. Webb. "Near Real Time Satellite Event Detection, Characterization, and Operational Assessment Via the Exploitation of Remote Photoacoustic Signatures". Journal of the Astronautical Sciences 68, n.º 1 (marzo de 2021): 197–224. http://dx.doi.org/10.1007/s40295-021-00252-5.

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AbstractCurrent active satellite maneuver detection techniques can resolve maneuvers as quickly as fifteen minutes post maneuver for large Δv when using angles-only optical tracking. Medium to small magnitude burn detection times range from 6 to 24 h or more. Small magnitude burns may be indistinguishable from natural perturbative effects if passive techniques are employed. Utilizing a photoacoustic signature detection scheme can allow for near real time maneuver detection and spacecraft parameter estimation. We define the acquisition of hypertemporal photometric data as photoacoustic sensing because the data can be played back as an acoustic signal. Studying the operational frequency spectra, profile, and aural perception of an active satellite event such as a thruster ignition or any subsystem operation can provide unique signature identifiers that support resident space object characterization efforts. A thruster ignition induces vibrations in a satellite body which can modulate reflected sunlight. If the reflected photon flux is sampled at a sufficient rate, the change in light intensity due to the propulsive event can be detected. Sensing vibrational mode changes allows for a direct timestamp of thruster ignition and shut-off events and thus makes possible the near real time estimation of spacecraft Δv and maneuver type if coupled with active observations immediately post maneuver. This research also investigates the estimation of other impulse related spacecraft parameters such as mass, specific impulse, exhaust velocity, and mass flow rate using impulse-momentum and work-energy methods. Experimental results to date have not yet demonstrated an operator-correlated detection of a propulsive event; however, the application of photoacoustic sensing has exhibited characteristics unique to hypertemporal photometry that are discussed alongside potential improvements to increase the probability of active satellite event detection. Simulations herein suggest that large, potentially destructive modal displacements are required for optical sensor detection and thus more comprehensive vibration modeling and signal-to-noise ratio improvements should be explored.

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Salzberg, B. M. y A. L. Obaid. "Optical studies of the secretory event at vertebrate nerve terminals". Journal of Experimental Biology 139, n.º 1 (1 de septiembre de 1988): 195–231. http://dx.doi.org/10.1242/jeb.139.1.195.

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Potentiometric probes are small (300–500 Mr) amphipatic molecules that bind to, but do not cross, cell membranes and behave as fast linear transducers of membrane voltage. Their optical properties, particularly absorbance and fluorescence, respond to changes in potential in less than 2 microseconds, and they may be used to follow electrical events in membranes which are inaccessible to microelectrodes. We have used these dyes to study the properties of the action potential in the neurosecretory terminals of vertebrate neurohypophyses and, in particular, to investigate the behaviour of the local population of calcium channels. These channels are sensitive to the peptide toxin omega-conotoxin GVIA, derived from the venom of the marine snail Conus geographicus, but insensitive to dihydropyridine channel modulators. In the neurohypophysis of the mouse, it is possible to demonstrate that the calcium channels that are blocked by omega-conotoxin are those that are required for secretion of peptide hormones. In the terminals of the neurohypophysis, excitation is coupled to secretion, and the secretory event is accompanied by large and rapid changes in light scattering. These intrinsic optical signals provide a millisecond time-resolved monitor of events in the terminal that follow the entry of calcium, and may precede the release of hormones. We will consider how the changes in light scattering can be related to secretion, and how the extrinsic (absorption) and intrinsic optical signals may provide complementary information about excitation-secretion coupling.

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Kajava, Jari J. E., Margherita Giustini, Richard D. Saxton y Giovanni Miniutti. "Rapid late-time X-ray brightening of the tidal disruption event OGLE16aaa". Astronomy & Astrophysics 639 (julio de 2020): A100. http://dx.doi.org/10.1051/0004-6361/202038165.

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Stars that pass too close to a super-massive black hole may be disrupted by strong tidal forces. OGLE16aaa is one such tidal disruption event (TDE) which rapidly brightened and peaked in the optical/UV bands in early 2016 and subsequently decayed over the rest of the year. OGLE16aaa was detected in an XMM-Newton X-ray observation on June 9, 2016 with a flux slightly below the Swift/XRT upper limits obtained during the optical light curve peak. Between June 16–21, 2016, Swift/XRT also detected OGLE16aaa and based on the stacked spectrum, we could infer that the X-ray luminosity had jumped up by more than a factor of ten in just one week. No brightening signal was seen in the simultaneous optical/UV data to cause the X-ray luminosity to exceed the optical/UV one. A further XMM-Newton observation on November 30, 2016 showed that almost a year after the optical/UV peak, the X-ray emission was still at an elevated level, while the optical/UV flux decay had already leveled off to values comparable to those of the host galaxy. In all X-ray observations, the spectra were nicely modeled with a 50–70 eV thermal component with no intrinsic absorption, with a weak X-ray tail seen only in the November 30 XMM-Newton observation. The late-time X-ray behavior of OGLE16aaa strongly resembles the tidal disruption events ASASSN-15oi and AT2019azh. We were able to pinpoint the time delay between the initial optical TDE onset and the X-ray brightening to 182 ± 5 days, which may possibly represent the timescale between the initial circularization of the disrupted star around the super-massive black hole and the subsequent delayed accretion. Alternatively, the delayed X-ray brightening could be related to a rapid clearing of a thick envelope that covers the central X-ray engine during the first six months.

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Ahirwal, Mitul Kumar, Anil Kumar y Girish Kumar Singh. "Sub-band adaptive filtering method for electroencephalography/event related potential signal using nature inspired optimisation techniques". IET Science, Measurement & Technology 9, n.º 8 (1 de noviembre de 2015): 987–97. http://dx.doi.org/10.1049/iet-smt.2015.0048.

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Greenlee, Eric T., Joel S. Warm, Gregory J. Funke, Robert E. Patterson, Adam J. Strang, Victor S. Finomore, Laura E. Barnes y Matthew E. Funke. "Event-related cerebral hemodynamics in 2-D and 3-D Visual Vigilance Tasks". Proceedings of the Human Factors and Ergonomics Society Annual Meeting 60, n.º 1 (septiembre de 2016): 1558–62. http://dx.doi.org/10.1177/1541931213601360.

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Recently, Greenlee et al. (2015) demonstrated that a stereoscopic 3-D display attenuated the vigilance decrement, stabilizing optimal detection performance. Yet, the 3-D display did not halt the decline in global cerebral blood flow velocity (CBFV), an index of cortical resource utilization, which typically accompanies the vigilance decrement. One possible explanation for this enigmatic finding is that global CBFV may not have been sensitive enough to detect the neurological correlates of superior sustained performance in the 3-D condition. Perhaps a more fine-grained measure of CBFV would reveal the underlying neural markers. To explore that possibility, event-related analyses were employed to uncover moment-to-moment changes in CBFV. These analyses revealed that CBFV increased selectively in response to signal detections in the 3-D condition but not in the 2-D. Like performance in the 3-D condition, the detection-related CBFV response in that condition remained stable over time on task. These findings indicate that event-related measurement of detection-specific neural activity can uncover hemodynamic effects that may otherwise be buried by the tides of global CBFV. Implications for future CBFV research are discussed.

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Xiao, Xue‐Zhen, Yu‐Hei Shum, Troby K. ‐Y Lui, Yang Wang, Alexandra T. ‐C Cheung, Winnie C. W. Chu, Sebastiaan F. W. Neggers, Sandra S. ‐M Chan y Chun‐Yu Tse. "Functional connectivity of the frontotemporal network in preattentive detection of abstract changes: Perturbs and observes with transcranial magnetic stimulation and event‐related optical signal". Human Brain Mapping 41, n.º 11 (14 de marzo de 2020): 2883–97. http://dx.doi.org/10.1002/hbm.24984.

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Prommapan, Plengchart, Nermina Brljak, Troy W. Lowry, David Van Winkle y Steven Lenhert. "Aptamer Functionalized Lipid Multilayer Gratings for Label-Free Analyte Detection". Nanomaterials 10, n.º 12 (5 de diciembre de 2020): 2433. http://dx.doi.org/10.3390/nano10122433.

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Lipid multilayer gratings are promising optical biosensor elements that are capable of transducing analyte binding events into changes in an optical signal. Unlike solid state transducers, reagents related to molecular recognition and signal amplification can be incorporated into the lipid grating ink volume prior to fabrication. Here we describe a strategy for functionalizing lipid multilayer gratings with a DNA aptamer for the protein thrombin that allows label-free analyte detection. A double cholesterol-tagged, double-stranded DNA linker was used to attach the aptamer to the lipid gratings. This approach was found to be sufficient for binding fluorescently labeled thrombin to lipid multilayers with micrometer-scale thickness. In order to achieve label-free detection with the sub-100 nm-thick lipid multilayer grating lines, the binding affinity was improved by varying the lipid composition. A colorimetric image analysis of the light diffracted from the gratings using a color camera was then used to identify the grating nanostructures that lead to an optimal signal. Lipid composition and multilayer thickness were found to be critical parameters for the signal transduction from the aptamer functionalized lipid multilayer gratings.

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Ranjandish, Reza y Alexandre Schmid. "A Review of Microelectronic Systems and Circuit Techniques for Electrical Neural Recording Aimed at Closed-Loop Epilepsy Control". Sensors 20, n.º 19 (8 de octubre de 2020): 5716. http://dx.doi.org/10.3390/s20195716.

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Closed-loop implantable electronics offer a new trend in therapeutic systems aimed at controlling some neurological diseases such as epilepsy. Seizures are detected and electrical stimulation applied to the brain or groups of nerves. To this aim, the signal recording chain must be very carefully designed so as to operate in low-power and low-latency, while enhancing the probability of correct event detection. This paper reviews the electrical characteristics of the target brain signals pertaining to epilepsy detection. Commercial systems are presented and discussed. Finally, the major blocks of the signal acquisition chain are presented with a focus on the circuit architecture and a careful attention to solutions to issues related to data acquisition from multi-channel arrays of cortical sensors.

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Antonello, Massimiliano, Massimo Caccia, Romualdo Santoro, Roberto Ferrari, Gabriella Gaudio y Lorenzo Pezzotti. "Present status and perspective of dual-readout calorimetry for future accelerators". International Journal of Modern Physics A 35, n.º 15n16 (6 de junio de 2020): 2041012. http://dx.doi.org/10.1142/s0217751x20410122.

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Dual-readout calorimetry is a calorimetric technique able to overcome the noncompensation limit by simultaneously detecting scintillation and Cherenkov light. Scintillating photons provide a signal related to the energy deposition in the calorimeter by all ionising particles while Cherenkov photons provide a signal almost exclusively related to the electromagnetic component in the hadronic shower. Fluctuations among the electromagnetic and non-electromagnetic component of hadronic induced showers represent the major limit to reach resolutions needed in experiments at future leptonic colliders. In a dual-readout calorimeter, by looking at the two independent signals, it is possible to measure, event by event, the electromagnetic fraction and to correctly reconstruct the primary hadron energy. Applications of the dual-readout method in fiber-sampling calorimetry have been shown to be able to provide single hadron detection with an energy resolution around [Formula: see text], electromagnetic resolution around [Formula: see text], excellent particle identification capability, resulting in one of the most promising option for future leptonic colliders. Status-of-art of the dual-readout calorimetry, as well as, perspective in the developments toward scalable solution for [Formula: see text] detectors are presented in this paper. This includes, study on the material choice, SiPM readout of the fibers, possible segmentation of the fibers to enhance particle ID capability.

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Fabiani, Monica, Kathy A. Low, Emily Wee, Jeffrey J. Sable y Gabriele Gratton. "Reduced Suppression or Labile Memory? Mechanisms of Inefficient Filtering of Irrelevant Information in Older Adults". Journal of Cognitive Neuroscience 18, n.º 4 (1 de abril de 2006): 637–50. http://dx.doi.org/10.1162/jocn.2006.18.4.637.

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Cognitive aging theories emphasize the decrease in efficiency of inhibitory processes and attention control in normal aging, which, in turn, may result in reduction of working memory function. Accordingly, some of these age-related changes may be due to faster sensory memory decay or to inefficient filtering of irrelevant sensory information (sensory gating). Here, event-related brain potentials and the event-related optical signal were recorded in younger and older adults passively listening to tone trains. To determine whether age differentially affects decay of sensory memory templates over short intervals, trains were separated by delays of either 1 or 5 sec. To determine whether age affects the suppression of responses to unattended repeated stimuli, we evaluated the brain activity elicited by successive train stimuli. Some trains started with a shorter-duration stimulus (deviant trains). Results showed that both electrical and optical responses to tones were more persistent with repeated stimulation in older adults than in younger adults, whereas the effects of delay were similar in the two groups. A mismatch negativity (MMN) was elicited by the first stimulus in deviant trains. This MMN was larger for 1- than 5-sec delay, but did not differ across groups. These data suggest that age-related changes in sensory processing are likely due to inefficient filtering of repeated information, rather than to faster sensory memory decay. This inefficient filtering may be due to, or interact with, reduced attention control. Furthermore, it may increase the noise levels in the information processing system and thus contribute to problems with working memory and speed of processing.

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Wang, Chao y Yun Wang. "Robust singular value decomposition filtering for low signal-to-noise ratio seismic data". GEOPHYSICS 86, n.º 3 (21 de abril de 2021): V233—V244. http://dx.doi.org/10.1190/geo2020-0169.1.

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Reduced-rank filtering is a common method for attenuating noise in seismic data. Because conventional reduced-rank filtering distinguishes signals from noises only according to singular values, it performs poorly when the signal-to-noise ratio (S/N) is very low or when data contain high levels of isolate or coherent noise. Therefore, we have developed a novel and robust reduced-rank filtering method based on singular value decomposition in the time-space domain. In this method, noise is recognized and attenuated according to the characteristics of the singular values and the singular vectors. The left and right singular vectors corresponding to large singular values are selected first. Then, the right singular vectors are classified into different categories according to their curve characteristics, such as jump, pulse, and smooth. Each kind of right singular vector is related to a type of noise or seismic event, and it is corrected by using a different filtering technology, such as mean filtering, edge-preserving smoothing, or edge-preserving median filtering. The left singular vectors are also corrected by using the filtering methods based on frequency attributes such as main frequency and frequency bandwidth. To process seismic data containing a variety of events, local data are extracted along the local dip of the event. The optimal local dip is identified according to the singular values and singular vectors of the data matrices that are extracted along different trial directions. This new filtering method has been applied to synthetic and field seismic data, and its performance is compared with that of several conventional filtering methods. The results indicate that the new method is more robust for data with a low S/N, strong isolated noise, or coherent noise. The new method also overcomes the difficulties associated with selecting an optimal rank.

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34

Gao, Zhilin, Xingran Cui, Wang Wan, Zeguang Qin y Zhongze Gu. "Signal Quality Investigation of a New Wearable Frontal Lobe EEG Device". Sensors 22, n.º 5 (28 de febrero de 2022): 1898. http://dx.doi.org/10.3390/s22051898.

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The demand for non-laboratory and long-term EEG acquisition in scientific and clinical applications has put forward new requirements for wearable EEG devices. In this paper, a new wearable frontal EEG device called Mindeep was proposed. A signal quality study was then conducted, which included simulated signal tests and signal quality comparison experiments. Simulated signals with different frequencies and amplitudes were used to test the stability of Mindeep’s circuit, and the high correlation coefficients (>0.9) proved that Mindeep has a stable and reliable hardware circuit. The signal quality comparison experiment, between Mindeep and the gold standard device, Neuroscan, included three tasks: (1) resting; (2) auditory oddball; and (3) attention. In the resting state, the average normalized cross-correlation coefficients between EEG signals recorded by the two devices was around 0.72 ± 0.02, Berger effect was observed (p < 0.01), and the comparison results in the time and frequency domain illustrated the ability of Mindeep to record high-quality EEG signals. The significant differences between high tone and low tone in auditory event-related potential collected by Mindeep was observed in N2 and P2. The attention recognition accuracy of Mindeep achieved 71.12% and 74.76% based on EEG features and the XGBoost model in the two attention tasks, respectively, which were higher than that of Neuroscan (70.19% and 72.80%). The results validated the performance of Mindeep as a prefrontal EEG recording device, which has a wide range of potential applications in audiology, cognitive neuroscience, and daily requirements.

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Mathewson, K. E., D. M. Beck, T. Ro, M. Fabiani y G. Gratton. "Who's controlling the brakes? Pulsed inhibitory alpha EEG is linked to preparatory activity in the fronto-parietal network measured concurrently with the event-related optical signal (EROS)". Journal of Vision 11, n.º 11 (23 de septiembre de 2011): 195. http://dx.doi.org/10.1167/11.11.195.

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Alam, Raquib-ul, Haifeng Zhao, Andrew Goodwin, Omid Kavehei y Alistair McEwan. "Differences in Power Spectral Densities and Phase Quantities Due to Processing of EEG Signals". Sensors 20, n.º 21 (4 de noviembre de 2020): 6285. http://dx.doi.org/10.3390/s20216285.

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There has been a growing interest in computational electroencephalogram (EEG) signal processing in a diverse set of domains, such as cortical excitability analysis, event-related synchronization, or desynchronization analysis. In recent years, several inconsistencies were found across different EEG studies, which authors often attributed to methodological differences. However, the assessment of such discrepancies is deeply underexplored. It is currently unknown if methodological differences can fully explain emerging differences and the nature of these differences. This study aims to contrast widely used methodological approaches in EEG processing and compare their effects on the outcome variables. To this end, two publicly available datasets were collected, each having unique traits so as to validate the results in two different EEG territories. The first dataset included signals with event-related potentials (visual stimulation) from 45 subjects. The second dataset included resting state EEG signals from 16 subjects. Five EEG processing steps, involved in the computation of power and phase quantities of EEG frequency bands, were explored in this study: artifact removal choices (with and without artifact removal), EEG signal transformation choices (raw EEG channels, Hjorth transformed channels, and averaged channels across primary motor cortex), filtering algorithms (Butterworth filter and Blackman–Harris window), EEG time window choices (−750 ms to 0 ms and −250 ms to 0 ms), and power spectral density (PSD) estimation algorithms (Welch’s method, Fast Fourier Transform, and Burg’s method). Powers and phases estimated by carrying out variations of these five methods were analyzed statistically for all subjects. The results indicated that the choices in EEG transformation and time-window can strongly affect the PSD quantities in a variety of ways. Additionally, EEG transformation and filter choices can influence phase quantities significantly. These results raise the need for a consistent and standard EEG processing pipeline for computational EEG studies. Consistency of signal processing methods cannot only help produce comparable results and reproducible research, but also pave the way for federated machine learning methods, e.g., where model parameters rather than data are shared.

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Gratton, Gabriele, Monica Fabiani, Paul M. Corballis, Donald C. Hood, Marsha R. Goodman-Wood, Joy Hirsch, Karl Kim, David Friedman y Enrico Gratton. "Fast and Localized Event-Related Optical Signals (EROS) in the Human Occipital Cortex: Comparisons with the Visual Evoked Potential and fMRI". NeuroImage 6, n.º 3 (octubre de 1997): 168–80. http://dx.doi.org/10.1006/nimg.1997.0298.

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Tu, Ran, Yi Zeng, Jun Fang y Yong-Ming Zhang. "Influence of high altitude on the burning behaviour of typical combustibles and the related responses of smoke detectors in compartments". Royal Society Open Science 5, n.º 4 (abril de 2018): 180188. http://dx.doi.org/10.1098/rsos.180188.

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The effect of altitude on typical combustible burning and related smoke detector response signals was investigated by comparison experiments at altitudes of 40 m and 3650 m based on EN54 standard tests. Point-type light scattering photoelectric smoke detectors and ionization smoke detectors were used for four kinds of EN54 fire tests, including two kinds of smouldering fires with wood (test fire no. 2 in EN54 standard or TF2) and cotton (TF3), and two kinds of flaming fires with polyurethane (TF4) and n -heptane (TF5). First, the influence of altitude or ambient pressure on mass loss for smouldering combustion (TF2 or TF3) was insignificant, while a significant decrease in the mass burning rate was found for flaming tests (TF4 and TF5) as reported in our previous studies. Second, for photoelectric smoke detectors in flaming fire tests, the effect of altitude was similar to that of the burning rate, whereas for the ionization smoke detectors, the response signal at high altitudes was shown to be ‘enhanced’ by the detection principle of the ionization chamber, leading to an even larger value than at normal altitude for smouldering conditions. Third, to provide a reference for smoke detector design in high-altitude areas, the differences between signal speed in rising and peak values at two locations are discussed. Also, relationship between ion chamber signals and smoke optical densities are presented by utilization of an ionization smoke detector and smoke concentration meter. Moreover, a hierarchical diagram is illustrated to provide a better understanding of the effects of altitude on combustible burning behaviour and the mechanisms of detector response.

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Aitken, P. G., G. C. Tombaugh, D. A. Turner y G. G. Somjen. "Similar Propagation of SD and Hypoxic SD-Like Depolarization in Rat Hippocampus Recorded Optically and Electrically". Journal of Neurophysiology 80, n.º 3 (1 de septiembre de 1998): 1514–21. http://dx.doi.org/10.1152/jn.1998.80.3.1514.

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Aitken, P. G., G. C. Tombaugh, D. A. Turner, and G. G. Somjen. Similar propagation of SD and hypoxic SD-like depolarization in rat hippocampus recorded optically and electrically. J. Neurophysiol. 80: 1514–1521, 1998. Neuron membrane changes and ion redistribution during normoxic spreading depression (SD) induced, for example, by potassium injection, closely resemble those that occur during hypoxic SD-like depolarization (HSD) induced by oxygen withdrawal, but the degree to which the two phenomena are related is controversial. We used extracellular electrical recording and imaging of intrinsic optical signals in hippocampal tissue slices to compare 1) initiation and spread of these two phenomena and 2) the effects of putative gap junction blocking agents, heptanol and octanol. Both events arose focally, after which a clear advancing wave front of increased reflectance and DC shift spread along the CA1 stratum radiatum and s. oriens. The rate of spread was similar: conduction velocity of normoxic SD was 8.73 ± 0.92 mm/min (mean ± SE) measured electrically and 5.84 ± 0.63 mm/min measured optically, whereas HSD showed values of 7.22 ± 1.60 mm/min (electrical) and 6.79 ± 0.42 mm/min (optical). When initiated in CA1, normoxic SD consistently failed to enter the CA3 region (7/7 slices) and could not be initiated by direct KCl injection in the CA3 region ( n = 3). Likewise, the hypoxic SD-like optical signal showed onset in the CA1 region and halted at the CA1/CA3 boundary (9/9 slices), but in some (4/9) slices the dentate gyrus region showed a separate onset of signal changes. Microinjection into CA1 stratum radiatum of octanol (1 mM), which when bath applied arrests the spread of normoxic SD, created a small focus that appeared to be protected from hypoxic depolarization. However, bath application of heptanol (3 mM) or octanol (2 mM) did not prevent the spread of HSD, although the onset was delayed. This suggests that, although gap junctions may be essential for the spread of normoxic SD, they may play a less important role in the spread of HSD.

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40

DeSoto, M. Catherine, Monica Fabiani, David C. Geary y Gabriele Gratton. "When in Doubt, Do it Both Ways: Brain Evidence of the Simultaneous Activation of Conflicting Motor Responses in a Spatial Stroop Task". Journal of Cognitive Neuroscience 13, n.º 4 (1 de mayo de 2001): 523–36. http://dx.doi.org/10.1162/08989290152001934.

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Response competition is often considered an important contributor to the delayed reaction to stimuli for which physical and semantic information are in conflict (“Stroop” effect). Response competition implies that brain areas associated with correct and incorrect responses (e.g., left and right motor cortices) should be simultaneously activated in conflict conditions. However, there is at present little direct evidence of this phenomenon, in part because of the paucity of brain imaging techniques that can independently monitor the time course of activation of adjacent brain areas, such as the motor areas. In the present study, we show that the event-related optical signal (EROS) can provide these types of data. The results confirm the prediction that conflict trials elicit simultaneous activation of both motor cortices, whereas nonconflict trials elicit brain activity only in the contralateral motor cortex. These data support a parallel view of the human information processing system.

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Fayuk, Dmitriy, Peter G. Aitken, George G. Somjen y Dennis A. Turner. "Two Different Mechanisms Underlie Reversible, Intrinsic Optical Signals in Rat Hippocampal Slices". Journal of Neurophysiology 87, n.º 4 (1 de abril de 2002): 1924–37. http://dx.doi.org/10.1152/jn.00231.2001.

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Intrinsic optical signals (IOSs) induced by synaptic stimulation and moderate hypotonic swelling in brain tissue slices consist of reduced light scattering and are usually attributed to cell swelling. During spreading depression (SD), however, light-scattering increases even though SD has been shown to cause strong cell swelling. To understand this phenomenon, we recorded extracellular voltage, light transmission (LT), which is inversely related to light scattering, and interstitial volume (ISV) simultaneously from the same site (stratum radiatum of CA1) in both interface and submerged hippocampal slices. As expected, moderate lowering of bath osmolarity caused concentration-dependent shrinkage of ISV and increase in LT, while increased osmolarity induced opposite changes in both variables. During severe hypotonia, however, after an initial increase of LT, the direction of the IOS reversed to a progressive decrease in spite of continuing ISV shrinkage. SD caused by hypotonia, by microinjection of high-K+ solution, or by hypoxia, was associated with a pronounced LT decrease, during which ISV shrinkage indicated maximal cell swelling. If most of the extracellular Cl− was substituted by the impermeant anion methylsulfate and also in strongly hypertonic medium, the SD-related decrease in LT was suppressed and replaced by a monotonic increase. Nevertheless, the degree of ISV shrinkage was similar in low and in normal Cl− conditions. The optical signals and ISV changes were qualitatively identical in interface and submerged slices. We conclude that there are at least two mechanisms that underlie reversible optical responses in hippocampal slices. The first mechanism underlies light-scattering decrease (hence enhancing LT) when ISV shrinks (cell swelling) under synaptic stimulation and mild hypotonia. Similarly, as result of this mechanism, expansion of ISV (cell shrinkage) during mild hypertonia leads to an increased light scattering (and decreased LT). Thus optical signals associated with this first mechanism show expected cell-volume changes and are linked to either cell swelling or shrinkage. A different mechanism causes the light-scattering increase (leading to a LT decrease) during severe hypotonia and various forms of SD but with a severely decreased ISV. This second mechanism may be due to organelle swelling or dendritic beading but not to cell-volume increase. These two mechanisms can summate, indicating that they are independent in origin. Suppression of the SD-related light-scattering increase by lowering [Cl−]o or severe hypertonia unmasks the underlying swelling-related scattering decrease. The simultaneous IOS and ISV measurements clearly distinguish these two mechanisms of optical signal generation.

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42

Li, Peixi, Yannick Benezeth, Richard Macwan, Keisuke Nakamura, Randy Gomez, Chao Li y Fan Yang. "Video-Based Pulse Rate Variability Measurement Using Periodic Variance Maximization and Adaptive Two-Window Peak Detection". Sensors 20, n.º 10 (12 de mayo de 2020): 2752. http://dx.doi.org/10.3390/s20102752.

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Many previous studies have shown that the remote photoplethysmography (rPPG) can measure the Heart Rate (HR) signal with very high accuracy. The remote measurement of the Pulse Rate Variability (PRV) signal is also possible, but this is much more complicated because it is then necessary to detect the peaks on the temporal rPPG signal, which is usually quite noisy and has a lower temporal resolution than PPG signals obtained by contact equipment. Since the PRV signal is vital for various applications such as remote recognition of stress and emotion, the improvement of PRV measurement by rPPG is a critical task. Contact based PRV measurement has already been investigated, but the research on remotely measured PRV is very limited. In this paper, we propose to use the Periodic Variance Maximization (PVM) method to extract the rPPG signal and event-related Two-Window algorithm to improve the peak detection for PRV measurement. We have made several contributions. Firstly, we show that the newly proposed PVM method and Two-Window algorithm can be used for PRV measurement in the non-contact scenario. Secondly, we propose a method to adaptively determine the parameters of the Two-Window method. Thirdly, we compare the algorithm with other attempts for improving the non-contact PRV measurement such as the Slope Sum Function (SSF) method and the Local Maximum method. We calculated several features and compared the accuracy based on the ground truth provided by contact equipment. Our experiments showed that this algorithm performed the best of all the algorithms.

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Tse, Chun-Yu, Kathy A. Low, Monica Fabiani y Gabriele Gratton. "Rules Rule! Brain Activity Dissociates the Representations of Stimulus Contingencies with Varying Levels of Complexity". Journal of Cognitive Neuroscience 24, n.º 9 (septiembre de 2012): 1941–59. http://dx.doi.org/10.1162/jocn_a_00229.

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The significance of stimuli is linked not only to their nature but also to the sequential structure in which they are embedded, which gives rise to contingency rules. Humans have an extraordinary ability to extract and exploit these rules, as exemplified by the role of grammar and syntax in language. To study the brain representations of contingency rules, we recorded ERPs and event-related optical signal (EROS; which uses near-infrared light to measure the optical changes associated with neuronal responses). We used sequences of high- and low-frequency tones varying according to three contingency rules, which were orthogonally manipulated and differed in processing requirements: A Single Repetition rule required only template matching, a Local Probability rule required relating a stimulus to its context, and a Global Probability rule could be derived through template matching or with reference to the global sequence context. ERP activity at 200–300 msec was related to the Single Repetition and Global Probability rules (reflecting access to representations based on template matching), whereas longer-latency activity (300-450 msec) was related to the Local Probability and Global Probability rules (reflecting access to representations incorporating contextual information). EROS responses with corresponding latencies indicated that the earlier activity involved the superior temporal gyrus, whereas later responses involved a fronto-parietal network. This suggests that the brain can simultaneously hold different models of stimulus contingencies at different levels of the information processing system according to their processing requirements, as indicated by the latency and location of the corresponding brain activity.

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44

Liptay, Albert, John L. Barron, Tom Jewett y Ian van Wesenbeeck. "Oscillations in Corn Seedling Growth as Measured by Optical Flow". Journal of the American Society for Horticultural Science 120, n.º 3 (mayo de 1995): 379–85. http://dx.doi.org/10.21273/jashs.120.3.379.

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Growth of corn seedlings during the coleoptile stage was measured using optical flow. The measurement system was comprised of a digital camera, computer, and related software and measured growth in a continuous, noncontact manner. The use of optical flow to measure shoot elongation, i.e., image motion of the elongating seedling, was most easily computed when there were large spatiotemporal variations of the motion of the corn seedling against the background. The sensitivity of the measurement technique was in the micron per second range. Seedling growth did not occur in a smooth even manner, rather, growth was a series of varying bursts or waves of expansion that appeared to be affected by the physical growth or development of the leaves. Spectral analysis techniques were applied to extract the underlying signal from the observed time series of seedling growth rate and angle.

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Nordmeyer, Ulrich, Niels Neumann, Xiaozhou Wang, Dirk Plettemeier, Torsten Thiel y Konstantin Kojucharow. "Evaluation of optical fibre sensors in the electrical domain". Journal of Sensors and Sensor Systems 9, n.º 2 (15 de julio de 2020): 199–208. http://dx.doi.org/10.5194/jsss-9-199-2020.

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Abstract. Optical fibre sensors cover a wide range of applications. They offer versatile advantages including resilience to electromagnetic interference, biocompatibility and chemical resistivity. Even in environments with restricted accessibility, integration difficulties can be overcome by using radio-over-fibre (RoF) technology that allows a wireless read-out. Conventionally, optical fibre sensors are evaluated in the optical domain by analysing the amplitude or spectrum of either the transmitted or the reflected light. A novel approach is to feed a radio frequency-modulated laser into the optical sensor and carry out a full electrical analysis of the resulting radio frequency (RF) signal, which is changed by the sensor's characteristics. This method will be investigated in this paper for fibre Bragg grating-based and chirped fibre Bragg grating-based sensors in reflection and transmission configuration. Their applicability for this new evaluation scheme will be discussed. Subsequent studies may cover additional types of sensors and the testing of the novel evaluation method within an application-related scenario, including packaging.

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Meiser, Arnd y Martin G. Bleichner. "Ear-EEG compares well to cap-EEG in recording auditory ERPs: a quantification of signal loss". Journal of Neural Engineering 19, n.º 2 (1 de abril de 2022): 026042. http://dx.doi.org/10.1088/1741-2552/ac5fcb.

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Abstract Objective. Ear-EEG (electroencephalography) allows to record brain activity using only a few electrodes located close to the ear. Ear-EEG is comfortable and easy to apply, facilitating beyond-the-lab EEG recordings in everyday life. With the unobtrusive setup, a person wearing it can blend in, allowing unhindered EEG recordings in social situations. However, compared to classical cap-EEG, only a small part of the head is covered with electrodes. Most scalp positions that are known from established EEG research are not covered by ear-EEG electrodes, making the comparison between the two approaches difficult and might hinder the transition from cap-based lab studies to ear-based beyond-the-lab studies. Approach. We here provide a reference data-set comparing ear-EEG and cap-EEG directly for four different auditory event-related potentials (ERPs): N100, MMN, P300 and N400. We show how the ERPs are reflected when using only electrodes around the ears. Main results. We find that significant condition differences for all ERP-components could be recorded using only ear-electrodes. The effect sizes were moderate to high on the single subject level. Morphology and temporal evolution of signals recorded from around-the-ear resemble highly those from standard scalp-EEG positions. We found a reduction in effect size (signal loss) for the ear-EEG electrodes compared to cap-EEG of 21%–44%. The amount of signal loss depended on the ERP-component; we observed the lowest percentage signal loss for the N400 and the highest percentage signal loss for the N100. Our analysis further shows that no single channel position around the ear is optimal for recording all ERP-components or all participants, speaking in favor of multi-channel ear-EEG solutions. Significance. Our study provides reference results for future studies employing ear-EEG.

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Diaspro, Alberto, Giuseppe Chirico y Maddalena Collini. "Two-photon fluorescence excitation and related techniques in biological microscopy". Quarterly Reviews of Biophysics 38, n.º 2 (mayo de 2005): 97–166. http://dx.doi.org/10.1017/s0033583505004129.

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1. Introduction 982. Historical background of two-photon effects 992.1 2PE 1002.2 Harmonic generation 1002.3 Fluorescence correlation spectroscopy 1003. Basic principles of two-photon excitation of fluorescent molecules and implications for microscopy and spectroscopy 1013.1 General considerations 1013.2 Fluorescence intensity under the 2PE condition 1033.3 Optical consequences of 2PE 1043.4 Saturation effects in 2PE 1083.5 Fluorescence correlation spectroscopy 1093.5.1 Autocorrelation analysis 1103.5.2 Photon-counting histogram analysis 1124. Two-photon-excited probes 1155. Design considerations for a 2PE fluorescence microscope 1195.1 General aspects 1195.2 Descanned and non-descanned 2PE imaging 1215.3 Lens objectives and pulse broadening 1225.4 Laser sources 1255.5 Example of a practical realization 1276. Applications 1346.1 Biological applications of 2PE 1346.1.1 Brain images 1346.1.2 Applications on the kidney 1396.1.3 Mammalian embryos 1396.1.4 Applications to immuno-response 1416.1.5 Myocytes 1416.1.6 Retina 1426.1.7 DNA imaging 1436.1.8 FISH applications 1446.2 2PE imaging of single molecules 1446.3 FCS applications 1486.4 Signals from nonlinear interactions 1517. Conclusions 1538. Acknowledgements 1549. References 155This review is concerned with two-photon excited fluorescence microscopy (2PE) and related techniques, which are probably the most important advance in optical microscopy of biological specimens since the introduction of confocal imaging. The advent of 2PE on the scene allowed the design and performance of many unimaginable biological studies from the single cell to the tissue level, and even to whole animals, at a resolution ranging from the classical hundreds of nanometres to the single molecule size. Moreover, 2PE enabled long-term imaging of in vivo biological specimens, image generation from deeper tissue depth, and higher signal-to-noise images compared to wide-field and confocal schemes. However, due to the fact that up to this time 2PE can only be considered to be in its infancy, the advantages over other techniques are still being evaluated. Here, after a brief historical introduction, we focus on the basic principles of 2PE including fluorescence correlation spectroscopy. The major advantages and drawbacks of 2PE-based experimental approaches are discussed and compared to the conventional single-photon excitation cases. In particular we deal with the fluorescence brightness of most used dyes and proteins under 2PE conditions, on the optical consequences of 2PE, and the saturation effects in 2PE that mostly limit the fluorescence output. A complete section is devoted to the discussion of 2PE of fluorescent probes. We then offer a description of the central experimental issues, namely: choice of microscope objectives, two-photon excitable dyes and fluorescent proteins, choice of laser sources, and effect of the optics on 2PE sensitivity. An inevitably partial, but vast, overview of the applications and a large and up-to-date bibliography terminate the review. As a conclusive comment, we believe that 2PE and related techniques can be considered as a mainstay of the modern biophysical research milieu and a bright perspective in optical microscopy.

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Beligni, Alessio, Claudio Sbarufatti, Andrea Gilioli, Francesco Cadini y Marco Giglio. "Robust Identification of Strain Waves due to Low-Velocity Impact with Different Impactor Stiffness". Sensors 19, n.º 6 (14 de marzo de 2019): 1283. http://dx.doi.org/10.3390/s19061283.

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Low-velocity impacts represent a major concern for aeronautical structures, sometimes producing barely detectable damage that could severely hamper the aircraft safety, even with regards to metallic structures. For this reason, the development of an automated impact monitoring system is desired. From a passive monitoring perspective, any impact generates a strain wave that can be acquired using sensor networks; signal processing techniques allow for extracting features useful for impact identification, possibly in an automatic way. However, impact wave characteristics are related to the impactor stiffness; this presents a problem for the evaluation of an impact-related feature and for the development of an automatic approach to impact identification. This work discusses the problem of reducing the influence of the impactor stiffness on one of the features typically characterizing the impact event, i.e., the time of arrival (TOA). Two passive sensor networks composed of accelerometers and piezoelectric sensors are installed on two metallic specimens, consisting of an aluminum skin and a sandwich panel, with aluminum skins and NOMEXTM honeycomb core. The effect of different impactor stiffnesses is investigated by resorting to an impact hammer, equipped with different tips. Subsequently, a method for data processing is defined to obtain a feature insensitive to the impactor stiffness, and this method is applied to multiple impact signals for feature uncertainty evaluation.

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Nagal, Rachana, Pradeep Kumar y Poonam Bansal. "AN OPTIMAL APPROACH FOR EEG/ERP NOISE CANCELLATION USING ADAPTIVE FILTER WITH OPPOSITIONAL WHALE OPTIMIZATION ALGORITHM". Biomedical Engineering: Applications, Basis and Communications 31, n.º 05 (9 de septiembre de 2019): 1950035. http://dx.doi.org/10.4015/s1016237219500352.

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In this paper, the Oppositional Whale Optimization Algorithm (OWOA) is applied to Adaptive Noise Canceller (ANC) for the filtering of Electroencephalography/Event-Related Potentials (EEG/ERP) signals. Performance of ANC will be improved by calculating the optimal weight value and proposed OWOA technique is used to update weight value. Adaptive filter’s noise reduction capability has been tested through consideration of White Gaussian Noise (WGN) over contaminated EEG signals at various SNR levels ([Formula: see text]10[Formula: see text]dB, [Formula: see text]15[Formula: see text]dB and [Formula: see text]20[Formula: see text]dB). The performance of the proposed OWOA algorithm is assessed in terms of Signal to Noise Ratio (SNR) in dB, mean value, and the correlation between resultant and input ERP. In this work, ANCs are also implemented by utilizing conventional gradient-based techniques like Recursive Least Square (RLS), Least Mean Square (LMS) and other optimization algorithms such as Genetic Algorithm (GA), Particle Swarm Optimization (PSO) and WOA techniques. In average cases of noisy environment, comparative analysis shows that the proposed OWOA technique provides higher SNR value and significantly lower mean, and correlation as compared to gradient-based and swarm-based techniques. The comparative results show that extracting the desired EEG component is more effective in the proposed OWOA method. So, it has seen that OWOA-based noise reduction technique removing the artifacts and improving the quality of EEG signals significantly for biomedical analysis.

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Piana Agostinetti, Nicola, Alberto Villa y Gilberto Saccorotti. "Distributed acoustic sensing as a tool for subsurface mapping and seismic event monitoring: a proof of concept". Solid Earth 13, n.º 2 (3 de marzo de 2022): 449–68. http://dx.doi.org/10.5194/se-13-449-2022.

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Abstract. We use PoroTomo experimental data to compare the performance of distributed acoustic sensing (DAS) and geophone observations in retrieving data to execute standard subsurface mapping and seismic monitoring activities. The PoroTomo experiment consists of two “seismic systems”: (a) a 8.6 km long optical fibre cable deployed across the Brady geothermal field and covering an area of 1.5 × 0.5 km with 100 m long segments and (b) a co-located array of 238 geophones with an average spacing of 60 m. The PoroTomo experiment recorded continuous seismic data between 10 and 25 March 2016. During this period, a Ml 4.3 regional event occurred in the southeast, about 150 km away from the geothermal field, together with several microseismic local events related to the geothermal activity. The seismic waves generated from such seismic events have been used as input data in this study to tackle similarities and differences between DAS and geophone recordings of such wavefronts. To assess the quality of data for subsurface mapping tasks, we measure the propagation of the P wave generated by the regional event across the geothermal field in both seismic systems in term of relative time delays, for a number of configurations and segments. Additionally, we analyse and compare the amplitude and the signal-to-noise ratio (SNR) of the P wave in the two systems at high resolution. For testing the potential of DAS data in seismic event locations, we first perform an analysis of the geophone data to retrieve a reference location of a microseismic event, based on expert opinion. Then, we a adopt different workflow for the automatic location of the same microseismic event using DAS data. To assess the quality of the data for tasks related to monitoring distant events, we retrieve both the propagation direction and apparent velocity of the wave field generated by the Ml 4.3 regional event, using a standard plane-wave-fitting approach applied to DAS data. Our results indicate that (1) at a local scale, the seismic P-wave propagation (i.e. time delays) and their characteristics (i.e. SNR and amplitude) along a single cable segment are robustly consistent with recordings from co-located geophones (delay times δt∼0.3 over 400 m for both seismic systems); (2) the DAS and nodal arrays are in mutual agreement when it comes to site amplifications, but it is not immediately clear which geological features are responsible for these amplifications. DAS could therefore hold potential for detailed mapping of shallow subsurface heterogeneities, but with the currently available information of the Brady Hot Springs subsurface geology, this potential cannot be quantitatively verified; (3) the interpretation of seismic wave propagation across multiple separated segments is less clear due to the heavy contamination of scattering sources and local velocity heterogeneities; nonetheless, results from the plane-wave-fitting approach still indicate the possibility for a consistent detection and location of the distant event; (4) automatic monitoring of microseismicity can be performed with DAS recordings with results comparable to manual analysis of geophone recordings in the case of events within or close to the DAS system (i.e. maximum horizontal error on event location around 70 m for both geophone and DAS data); and (5) DAS data preconditioning (e.g. temporal subsampling and channel stacking) and dedicated processing techniques are strictly necessary for making seismic monitoring procedures feasible and trustable.

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