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Sample records for intrinsic optical signal

  1. Cellular origin of intrinsic optical signals in the rabbit retina.

    PubMed

    Naderian, A; Bussières, L; Thomas, S; Lesage, F; Casanova, C

    2017-08-01

    Optical imaging of retinal intrinsic signals is a relatively new method that provides spatiotemporal patterns of retinal activity through activity-dependent changes in light reflectance of the retina. The exact physiological mechanisms at the origin of retinal intrinsic signals are poorly understood and there are significant inter-species differences in their characteristics and cellular origins. In this study, we re-examined this issue through pharmacological dissection of retinal intrinsic signals in the rabbit with simultaneous ERG recordings. Retinal intrinsic signals faithfully reflected retinal activity as their amplitude was strongly associated with stimulation intensity (r(2)=0.85). Further, a strong linear relation was found using linear regression (r(2)=0.98) between retinal intrinsic signal amplitude and the ERG b wave, which suggests common cellular origins. Intravitreal injections of pharmacological agents were performed to isolate the activity of the retina's major cell types. Retinal intrinsic signals were abolished when the photoreceptors' activity was isolated with aspartate, indicative that they are not at the origin of this signal. A small but significant decrease in intrinsic response (20%) was observed when ganglion and amacrine cells' activity was inhibited by TTX injections. The remaining intrinsic responses were abolished in a dose-dependent manner through the inhibition of ON-bipolar cells by APB. Our results indicate that, in rabbits, retinal intrinsic signals reflect stimulation intensity and originate from the inner retina with a major contribution of bipolar cells and a minor one from ganglion or amacrine cells. Copyright © 2017 Elsevier Ltd. All rights reserved.

  2. [Enhancement of image used in optical imaging of intrinsic signal].

    PubMed

    Yin, Yu; Xia, Yang

    2012-02-01

    Optical imaging of intrinsic signals is a secondary image of the cerebral cortex. The weak optical signal is decided by anatomical structure of brain. The spatial filter is a powerful technology for de-noising and image enhancement. We used different linear and nonlinear filters to deal with optical imaging. Furthermore, we compared the degree of noise suppression and discussed the image details. Our result showed that nonlinear median filter can keep more image details with effective noise reduction. It is useful for image enhancement of optical imaging.

  3. Intrinsic optical signal imaging of retinal physiology: a review.

    PubMed

    Yao, Xincheng; Wang, Benquan

    2015-09-01

    Intrinsic optical signal (IOS) imaging promises to be a noninvasive method for high-resolution examination of retinal physiology, which can advance the study and diagnosis of eye diseases. While specialized optical instruments are desirable for functional IOS imaging of retinal physiology, in depth understanding of multiple IOS sources in the complex retinal neural network is essential for optimizing instrument designs. We provide a brief overview of IOS studies and relationships in rod outer segment suspensions, isolated retinas, and intact eyes. Recent developments of line-scan confocal and functional optical coherence tomography (OCT) instruments have allowed in vivo IOS mapping of photoreceptor physiology. Further improvements of the line-scan confocal and functional OCT systems may provide a feasible solution to pursue functional IOS mapping of human photoreceptors. Some interesting IOSs have already been detected in inner retinal layers, but better development of the IOS instruments and software algorithms is required to achieve optimal physiological assessment of inner retinal neurons.

  4. Intrinsic optical signal imaging of retinal physiology: a review

    NASA Astrophysics Data System (ADS)

    Yao, Xincheng; Wang, Benquan

    2015-09-01

    Intrinsic optical signal (IOS) imaging promises to be a noninvasive method for high-resolution examination of retinal physiology, which can advance the study and diagnosis of eye diseases. While specialized optical instruments are desirable for functional IOS imaging of retinal physiology, in depth understanding of multiple IOS sources in the complex retinal neural network is essential for optimizing instrument designs. We provide a brief overview of IOS studies and relationships in rod outer segment suspensions, isolated retinas, and intact eyes. Recent developments of line-scan confocal and functional optical coherence tomography (OCT) instruments have allowed in vivo IOS mapping of photoreceptor physiology. Further improvements of the line-scan confocal and functional OCT systems may provide a feasible solution to pursue functional IOS mapping of human photoreceptors. Some interesting IOSs have already been detected in inner retinal layers, but better development of the IOS instruments and software algorithms is required to achieve optimal physiological assessment of inner retinal neurons.

  5. Intrinsic optical signal imaging of retinal physiology: a review

    PubMed Central

    Yao, Xincheng; Wang, Benquan

    2015-01-01

    Abstract. Intrinsic optical signal (IOS) imaging promises to be a noninvasive method for high-resolution examination of retinal physiology, which can advance the study and diagnosis of eye diseases. While specialized optical instruments are desirable for functional IOS imaging of retinal physiology, in depth understanding of multiple IOS sources in the complex retinal neural network is essential for optimizing instrument designs. We provide a brief overview of IOS studies and relationships in rod outer segment suspensions, isolated retinas, and intact eyes. Recent developments of line-scan confocal and functional optical coherence tomography (OCT) instruments have allowed in vivo IOS mapping of photoreceptor physiology. Further improvements of the line-scan confocal and functional OCT systems may provide a feasible solution to pursue functional IOS mapping of human photoreceptors. Some interesting IOSs have already been detected in inner retinal layers, but better development of the IOS instruments and software algorithms is required to achieve optimal physiological assessment of inner retinal neurons. PMID:26405819

  6. In vivo intrinsic optical signal imaging of mouse retinas.

    PubMed

    Wang, Benquan; Yao, Xincheng

    2016-02-13

    Intrinsic optical signal (IOS) imaging is a promising noninvasive method for advanced study and diagnosis of eye diseases. Before pursuing clinical applications, more IOS studies employing animal models are necessary to establish the relationship between IOS distortions and eye diseases. Ample mouse models are available for investigating the relationship between IOS distortions and eye diseases. However, in vivo IOS imaging of mouse retinas is challenging due to the small ocular lens (compared to frog eyes) and inevitable eye movements. We report here in vivo IOS imaging of mouse retinas using a custom-designed functional OCT. The OCT system provided high resolution (3 μm) and high speed (up to 500 frames/s) imaging of mouse retinas. An animal holder equipped with a custom designed ear bar and bite bar was used to minimize eye movement due to breathing and heartbeats. Residual eye movement in OCT images was further compensated by accurate image registration. Dynamic OCT imaging revealed rapid IOSs from photoreceptor outer segments immediately (<10 ms) after the stimulation delivery, and unambiguous IOS changes were also observed from inner retinal layers with delayed time courses compared to that of photoreceptor IOSs.

  7. In vivo intrinsic optical signal imaging of mouse retinas

    NASA Astrophysics Data System (ADS)

    Wang, Benquan; Yao, Xincheng

    2016-03-01

    Intrinsic optical signal (IOS) imaging is a promising noninvasive method for advanced study and diagnosis of eye diseases. Before pursuing clinical applications, more IOS studies employing animal models are necessary to establish the relationship between IOS distortions and eye diseases. Ample mouse models are available for investigating the relationship between IOS distortions and eye diseases. However, in vivo IOS imaging of mouse retinas is challenging due to the small ocular lens (compared to frog eyes) and inevitable eye movements. We report here in vivo IOS imaging of mouse retinas using a custom-designed functional OCT. The OCT system provided high resolution (3 μm) and high speed (up to 500 frames/s) imaging of mouse retinas. An animal holder equipped with a custom designed ear bar and bite bar was used to minimize eye movement due to breathing and heartbeats. Residual eye movement in OCT images was further compensated by accurate image registration. Dynamic OCT imaging revealed rapid IOSs from photoreceptor outer segments immediately (<10 ms) after the stimulation delivery, and unambiguous IOS changes were also observed from inner retinal layers with delayed time courses compared to that of photoreceptor IOSs.

  8. A comparison of signal processing techniques for Intrinsic Optical Signal imaging in mice.

    PubMed

    Turley, Jordan A; Nilsson, Michael; Walker, Frederick Rohan; Johnson, Sarah J

    2015-01-01

    Intrinsic Optical Signal imaging is a technique which allows the visualisation and mapping of activity related changes within the brain with excellent spatial and temporal resolution. We analysed a variety of signal and image processing techniques applied to real mouse imaging data. The results were compared in an attempt to overcome the unique issues faced when performing the technique on mice and improve the understanding of post processing options available.

  9. Retinal intrinsic optical signals in a cat model of primary congenital glaucoma.

    PubMed

    Schallek, Jesse B; McLellan, Gillian J; Viswanathan, Suresh; Ts'o, Daniel Y

    2012-04-18

    To examine the impact of reduced inner retinal function and breed on intrinsic optical signals in cats. Retinal intrinsic optical signals were recorded from anesthetized cats with a modified fundus camera. Near infrared light (NIR, 700-900 nm) was used to illuminate the retina while a charge-coupled device (CCD) camera captured the NIR reflectance of the retina. Visible stimuli (540 nm) evoked patterned changes in NIR retinal reflectance. NIR intrinsic signals were compared across three subject groups: two Siamese cats with primary congenital glaucoma (PCG), a control Siamese cat without glaucoma, and a control group of seven normally pigmented cats. Intraocular pressure (IOP), pattern electroretinogram, and optical coherence tomography measurements were evaluated to confirm the inner retinal deficit in PCG cats. Stimulus-evoked, NIR retinal reflectance signals were observed in PCG cats despite severe degeneration of the nerve fiber layer and inner retinal function. The time course, spectral dependence, and spatial profile of signals imaged in PCG cats were similar to signals measured from normal and Siamese control cats. Despite increased IOP, reduced nerve fiber layer thickness and ganglion cell function, intrinsic optical signals persist in cats affected with PCG. The mechanisms giving rise to intrinsic signals remain despite inner retinal damage. Signal strength was reduced in all Siamese cats compared to controls, suggesting that reduced intrinsic signals in PCG cats represent a difference between breeds rather than loss of ganglion cells. These results corroborated previous findings that retinal ganglion cells are not the dominant source of intrinsic optical signals of the retina.

  10. Retinal Intrinsic Optical Signals in a Cat Model of Primary Congenital Glaucoma

    PubMed Central

    Schallek, Jesse B.; McLellan, Gillian J.; Viswanathan, Suresh; Ts'o, Daniel Y.

    2012-01-01

    Purpose. To examine the impact of reduced inner retinal function and breed on intrinsic optical signals in cats. Methods. Retinal intrinsic optical signals were recorded from anesthetized cats with a modified fundus camera. Near infrared light (NIR, 700–900 nm) was used to illuminate the retina while a charge-coupled device (CCD) camera captured the NIR reflectance of the retina. Visible stimuli (540 nm) evoked patterned changes in NIR retinal reflectance. NIR intrinsic signals were compared across three subject groups: two Siamese cats with primary congenital glaucoma (PCG), a control Siamese cat without glaucoma, and a control group of seven normally pigmented cats. Intraocular pressure (IOP), pattern electroretinogram, and optical coherence tomography measurements were evaluated to confirm the inner retinal deficit in PCG cats. Results. Stimulus-evoked, NIR retinal reflectance signals were observed in PCG cats despite severe degeneration of the nerve fiber layer and inner retinal function. The time course, spectral dependence, and spatial profile of signals imaged in PCG cats were similar to signals measured from normal and Siamese control cats. Conclusions. Despite increased IOP, reduced nerve fiber layer thickness and ganglion cell function, intrinsic optical signals persist in cats affected with PCG. The mechanisms giving rise to intrinsic signals remain despite inner retinal damage. Signal strength was reduced in all Siamese cats compared to controls, suggesting that reduced intrinsic signals in PCG cats represent a difference between breeds rather than loss of ganglion cells. These results corroborated previous findings that retinal ganglion cells are not the dominant source of intrinsic optical signals of the retina. PMID:22395886

  11. Hyperspectral optical tomography of intrinsic signals in the rat cortex

    PubMed Central

    Konecky, Soren D.; Wilson, Robert H.; Hagen, Nathan; Mazhar, Amaan; Tkaczyk, Tomasz S.; Frostig, Ron D.; Tromberg, Bruce J.

    2015-01-01

    Abstract. We introduce a tomographic approach for three-dimensional imaging of evoked hemodynamic activity, using broadband illumination and diffuse optical tomography (DOT) image reconstruction. Changes in diffuse reflectance in the rat somatosensory cortex due to stimulation of a single whisker were imaged at a frame rate of 5 Hz using a hyperspectral image mapping spectrometer. In each frame, images in 38 wavelength bands from 484 to 652 nm were acquired simultaneously. For data analysis, we developed a hyperspectral DOT algorithm that used the Rytov approximation to quantify changes in tissue concentration of oxyhemoglobin (ctHbO2) and deoxyhemoglobin (ctHb) in three dimensions. Using this algorithm, the maximum changes in ctHbO2 and ctHb were found to occur at 0.29±0.02 and 0.66±0.04  mm beneath the surface of the cortex, respectively. Rytov tomographic reconstructions revealed maximal spatially localized increases and decreases in ctHbO2 and ctHb of 321±53 and 555±96  nM, respectively, with these maximum changes occurring at 4±0.2  s poststimulus. The localized optical signals from the Rytov approximation were greater than those from modified Beer–Lambert, likely due in part to the inability of planar reflectance to account for partial volume effects. PMID:26835483

  12. In vivo optical coherence tomography of stimulus-evoked intrinsic optical signals in mouse retinas.

    PubMed

    Wang, Benquan; Lu, Yiming; Yao, Xincheng

    2016-09-01

    Intrinsic optical signal (IOS) imaging promises a noninvasive method for advanced study and diagnosis of eye diseases. Before pursuing clinical applications, it is essential to understand anatomic and physiological sources of retinal IOSs and to establish the relationship between IOS distortions and eye diseases. The purpose of this study was designed to demonstrate the feasibility of optical coherence tomography (SD-OCT) was employed for depth-resolved retinal imaging. A custom-designed animal holder equipped with ear bar and bite bar was used to minimize eye movements. Dynamic OCT imaging revealed rapid IOS from the photoreceptor’s outer segment immediately after the stimulation delivery, and slow IOS changes were observed from inner retinal layers. Comparative photoreceptor IOS and electroretinography recordings suggested that the fast photoreceptor IOS may be attributed to the early stage of phototransduction before the hyperpolarization of retinal photoreceptor.

  13. In vivo optical coherence tomography of stimulus-evoked intrinsic optical signals in mouse retinas

    NASA Astrophysics Data System (ADS)

    Wang, Benquan; Lu, Yiming; Yao, Xincheng

    2016-09-01

    Intrinsic optical signal (IOS) imaging promises a noninvasive method for advanced study and diagnosis of eye diseases. Before pursuing clinical applications, it is essential to understand anatomic and physiological sources of retinal IOSs and to establish the relationship between IOS distortions and eye diseases. The purpose of this study was designed to demonstrate the feasibility of in vivo IOS imaging of mouse models. A high spatiotemporal resolution spectral domain optical coherence tomography (SD-OCT) was employed for depth-resolved retinal imaging. A custom-designed animal holder equipped with ear bar and bite bar was used to minimize eye movements. Dynamic OCT imaging revealed rapid IOS from the photoreceptor's outer segment immediately after the stimulation delivery, and slow IOS changes were observed from inner retinal layers. Comparative photoreceptor IOS and electroretinography recordings suggested that the fast photoreceptor IOS may be attributed to the early stage of phototransduction before the hyperpolarization of retinal photoreceptor.

  14. Circular polarization intrinsic optical signal recording of stimulus-evoked neural activity

    PubMed Central

    Lu, Rong-Wen; Zhang, Qiu-Xiang; Yao, Xin-Cheng

    2011-01-01

    Linear polarization intrinsic optical signal (LP-IOS) measurement can provide sensitive detection of neural activities in stimulus-activated neural tissues. However, the LP-IOS magnitude and signal-to-noise ratio (SNR) are highly correlated with the nerve orientation relative to the polarization plane of the incident light. Because of the complexity of orientation dependency, LP-IOS optimization and outcome interpretation are time consuming and complicated. In this study, we demonstrate the feasibility of circular polarization intrinsic optical signal (CP-IOS) measurement. Our theoretical modeling and experimental investigation indicate that CP-IOS magnitude and SNR are independent from the nerve orientation. Therefore, CP-IOS promises a practical method for polarization IOS imaging of complex neural systems. PMID:21593917

  15. Intrinsic optical signals of brains in rats during loss of tissue viability: effect of brain temperature

    NASA Astrophysics Data System (ADS)

    Kawauchi, Satoko; Sato, Shunichi; Ooigawa, Hidetoshi; Nawashiro, Hiroshi; Kikuchi, Makoto

    2007-07-01

    Noninvasive, real-time monitoring of brain tissue viability is crucial for the patients with stroke, traumatic brain injury, etc. For this purpose, measurement of intrinsic optical signal (IOS) is attractive because it can provide direct information about the viability of brain tissue noninvasively. We performed simultaneous measurements of IOSs that are related to morphological characteristics, i.e., light scattering, and energy metabolism for rat brains during saline infusion as a model with temporal loss of brain tissue viability. The results showed that the scattering signal was steady in an initial phase but showed a drastic, triphasic change in a certain range of infusion time, during which the reduction of CuA in cytochrome c oxidase started and proceeded rapidly. The start time of triphasic scattering change was delayed for about 100 s by lowering brain temperature from 29°C to 24°C, demonstrating the optical detection of cerebroprotection effect by brain cooling. Electron microscopic observation showed morphological changes of dendrite and mitochondria in the cortical surface tissue after the triphasic scattering change, which was thought to be associated with the change in light scattering we observed. These findings suggest that the simultaneous measurement of the intrinsic optical signals related to morphological characteristics and energy metabolism is useful for monitoring tissue viability in brain.

  16. An evaluation of data analysis methods for optical intrinsic signal imaging

    NASA Astrophysics Data System (ADS)

    Li, Pengcheng; Luo, Weihua; Luo, Qingming; Cheng, Shangbin

    2003-12-01

    The optical intrinsic signal imaging is an indirect mapping of neuronal activity. The change in light intensity due to neuronal activity are often very small, no more than 0.1-6% of the total intensity of the reflected light in optimal cases, and the noise, which arise from either the biological noise associated with the respiration, circulation and irrelevant physiological activity or the instrumentation noise such as digitization noise, illumination noise, movement artifacts, etc. are usually large. In previous studies, a couple of analysis methods such as Standard Difference, Principal Component Analysis (PCA), Independent Component Analysis (ICA), Truncated Differences were used to suppress these large background noises and extract the small signal of interest from the noisy raw data. The performance of these methods for improving the determination of spatial pattern and time course of the response signal were examined and compared in this paper. The evaluations were employed to both simulated data and experimental optical intrinsic signal imaging data from rat somatosensory cortex during the electrical stimulation at contralateral sciatic nerve.

  17. Long-term optical imaging of intrinsic signals in anesthetized and awake monkeys

    NASA Astrophysics Data System (ADS)

    Roe, Anna W.

    2007-04-01

    Some exciting new efforts to use intrinsic signal optical imaging methods for long-term studies in anesthetized and awake monkeys are reviewed. The development of such methodologies opens the door for studying behavioral states such as attention, motivation, memory, emotion, and other higher-order cognitive functions. Long-term imaging is also ideal for studying changes in the brain that accompany development, plasticity, and learning. Although intrinsic imaging lacks the temporal resolution offered by dyes, it is a high spatial resolution imaging method that does not require application of any external agents to the brain. The bulk of procedures described here have been developed in the monkey but can be applied to the study of surface structures in any in vivo preparation.

  18. Functional imaging of glucose-evoked rat islet activities using transient intrinsic optical signals

    NASA Astrophysics Data System (ADS)

    Yao, Xin-Cheng; Cui, Wan-Xing; Li, Yi-Chao; Zhang, Wei; Lu, Rong-Wen; Thompson, Anthony; Amthor, Franklin; Wang, Xu-Jing

    2012-05-01

    We demonstrate intrinsic optical signal (IOS) imaging of intact rat islet, which consists of many endocrine cells working together. A near-infrared digital microscope was employed for optical monitoring of islet activities evoked by glucose stimulation. Dynamic NIR images revealed transient IOS responses in the islet activated by low-dose (2.75 mM) and high-dose (5.5 mM) glucose stimuli. Comparative experiments and quantitative analysis indicated that both glucose metabolism and calcium/insulin dynamics might contribute to the observed IOS responses. Further investigation of the IOS imaging technology may provide a high resolution method for ex vivo functional examination of the islet, which is important for advanced study of diabetes associated islet dysfunctions and for improved quality control of donor islets for transplantation.

  19. Simultaneous imaging of intrinsic optical signals and cerebral vessel responses during cortical spreading depression in rats

    NASA Astrophysics Data System (ADS)

    Li, Pengcheng; Chen, Shangbin; Luo, Weihua; Luo, Qingming

    2003-12-01

    Cortical spreading depression (CSD) is an important disease model for migraine and cerebral ischemia. We investigated the spatio-temporal characteristics of the intrinsic optical signals (IOS) at 570 nm and the cerebral blood vessel responses during CSD simultaneously by optical reflectance imaging in vivo. The CSD were induced by pinprick in 10 α-chloralose/urethane anesthetized Sprague-Dawley rats. A four-phasic IOS response was observed at pial arteries and parenchymal sites in all experimental animals and an initial slight pial arteries dilation (21.5%+/-13.6%) and constriction (-4.2%+/-3.5%) precedes the dramatic dilation (69.2%+/-26.1%) of pial arterioles was recorded. Our experimental results show a high correlation (r = 0.89+/-0.025) between the IOS response and the diameter changes of the cerebral blood vessels during CSD in rats.

  20. Quantitative optical biomarkers of lung cancer based intrinsic two-photon excited fluorescence signal

    NASA Astrophysics Data System (ADS)

    Li, Jingwen; Zhan, Zhenlin; Lin, Hongxin; Zuo, Ning; Zhu, Xiaoqin; Xie, Shusen; Chen, Jianxin; Zhuo, Shuangmu

    2016-10-01

    Alterations in the elastic fibers have been implicated in lung cancer. However, the label-free, microscopic imaging of elastic fibers in situ remains a major challenge. Here, we present the use of intrinsic two-photon excited fluorescence (TPEF) signal as a novel means for quantification of the elastic fibers in intact fresh human lung tissues. We obtained the TPEF images of elastic fibers from ex vivo the human lung tissues. We found that three features, including the elastic fibers area, the elastic fibers orientation, the elastic fibers structure, provide the quantitative identification of lung cancer and the direct visual cues for cancer versus non-cancer areas. These results suggest that the TPEF signal can be used as the label-free optical biomarkers for rapid clinical lung diagnosis and instant image-guided surgery.

  1. Detection of low-amplitude in vivo intrinsic signals from an optical imager of retinal function

    NASA Astrophysics Data System (ADS)

    Barriga, Eduardo S.; T'so, Dan; Pattichis, Marios; Kwon, Young; Kardon, Randy; Abramoff, Michael; Soliz, Peter

    2006-02-01

    In the early stages of some retinal diseases, such as glaucoma, loss of retinal activity may be difficult to detect with today's clinical instruments. Many of today's instruments focus on detecting changes in anatomical structures, such as the nerve fiber layer. Our device, which is based on a modified fundus camera, seeks to detect changes in optical signals that reflect functional changes in the retina. The functional imager uses a patterned stimulus at wavelength of 535nm. An intrinsic functional signal is collected at a near infrared wavelength. Measured changes in reflectance in response to the visual stimulus are on the order of 0.1% to 1% of the total reflected intensity level, which makes the functional signal difficult to detect by standard methods because it is masked by other physiological signals and by imaging system noise. In this paper, we analyze the video sequences from a set of 60 experiments with different patterned stimuli from cats. Using a set of statistical techniques known as Independent Component Analysis (ICA), we estimate the signals present in the videos. Through controlled simulation experiments, we quantify the limits of signal strength in order to detect the physiological signal of interest. The results of the analysis show that, in principle, signal levels of 0.1% (-30dB) can be detected. The study found that in 86% of the animal experiments the patterned stimuli effects on the retina can be detected and extracted. The analysis of the different responses extracted from the videos can give an insight of the functional processes present during the stimulation of the retina.

  2. Optical imaging of the intrinsic signal as a measure of cortical plasticity in the mouse.

    PubMed

    Cang, Jianhua; Kalatsky, Valery A; Löwel, Siegrid; Stryker, Michael P

    2005-01-01

    The responses of cells in the visual cortex to stimulation of the two eyes changes dramatically following a period of monocular visual deprivation (MD) during a critical period in early life. This phenomenon, referred to as ocular dominance (OD) plasticity, is a widespread model for understanding cortical plasticity. In this study, we designed stimulus patterns and quantification methods to analyze OD in the mouse visual cortex using optical imaging of intrinsic signals. Using periodically drifting bars restricted to the binocular portion of the visual field, we obtained cortical maps for both contralateral (C) and ipsilateral (I) eyes and computed OD maps as (C - I)/(C + I). We defined the OD index (ODI) for individual animals as the mean of the OD map. The ODI obtained from an imaging session of less than 30 min gives reliable measures of OD for both normal and monocularly deprived mice under Nembutal anesthesia. Surprisingly, urethane anesthesia, which yields excellent topographic maps, did not produce consistent OD findings. Normal Nembutal-anesthetized mice have positive ODI (0.22 +/- 0.01), confirming a contralateral bias in the binocular zone. For mice monocularly deprived during the critical period, the ODI of the cortex contralateral to the deprived eye shifted negatively towards the nondeprived, ipsilateral eye (ODI after 2-day MD: 0.12 +/- 0.02, 4-day: 0.03 +/- 0.03, and 6- to 7-day MD: -0.01 +/- 0.04). The ODI shift induced by 4-day MD appeared to be near maximal, consistent with previous findings using single-unit recordings. We have thus established optical imaging of intrinsic signals as a fast and reliable screening method to study OD plasticity in the mouse.

  3. Intrinsic signal optical imaging of brain function using short stimulus delivery intervals.

    PubMed

    Chen-Bee, Cynthia H; Agoncillo, Teodora; Lay, Christopher C; Frostig, Ron D

    2010-03-30

    Intrinsic signal optical imaging (ISOI) can be used to map cortical function and organization. Because its detected signal lasts 10+s consisting of three phases, trials are typically collected using a long (tens of seconds) stimulus delivery interval (SDI) at the expense of efficiency, even when interested in mapping only the first signal phase (e.g., ISOI initial dip). It is unclear how the activity profile can change when stimuli are delivered at shorter intervals, and whether a short SDI can be implemented to improve efficiency. The goals of the present study are twofold: characterize the ISOI activity profile when multiple stimuli are delivered at 4s intervals, and determine whether successful mapping can be attained from trials collected using an SDI of 4s (offering >10x increase in efficiency). Our results indicate that four stimuli delivered 4s apart evoke an activity profile different from the triphasic signal, consisting of signal dips in a series at the same frequency as the stimuli despite a strong rise in signal prior to the 2nd to 4th stimuli. Visualization of such signal dips is dependent on using a baseline immediately prior to every stimulus. Use of the 4-s SDI is confirmed to successfully map activity with a similar location in peak activity and increased areal extent and peak magnitude compared to using a long SDI. Additional experiments were performed to begin addressing issues such as SDI temporal jittering, response magnitude as a function of SDI duration, and application for successful mapping of cortical function topography.

  4. An analysis of signal processing algorithm performance for cortical intrinsic optical signal imaging and strategies for algorithm selection.

    PubMed

    Turley, J A; Zalewska, K; Nilsson, M; Walker, F R; Johnson, S J

    2017-08-03

    Intrinsic Optical Signal (IOS) imaging has been used extensively to examine activity-related changes within the cerebral cortex. A significant technical challenge with IOS imaging is the presence of large noise, artefact components and periodic interference. Signal processing is therefore important in obtaining quality IOS imaging results. Several signal processing techniques have been deployed, however, the performance of these approaches for IOS imaging has never been directly compared. The current study aims to compare signal processing techniques that can be used when quantifying stimuli-response IOS imaging data. Data were gathered from the somatosensory cortex of mice following piezoelectric stimulation of the hindlimb. The effectiveness of each technique to remove noise and extract the IOS signal was compared for both spatial and temporal responses. Careful analysis of the advantages and disadvantages of each method were carried out to inform the choice of signal processing for IOS imaging. We conclude that spatial Gaussian filtering is the most effective choices for improving the spatial IOS response, whilst temporal low pass and bandpass filtering produce the best results for producing temporal responses when periodic stimuli are an option. Global signal regression and truncated difference also work well and do not require periodic stimuli.

  5. Comparative intrinsic optical signal imaging of wild-type and mutant mouse retinas.

    PubMed

    Zhang, Qiu-Xiang; Zhang, Youwen; Lu, Rong-Wen; Li, Yi-Chao; Pittler, Steven J; Kraft, Timothy W; Yao, Xin-Cheng

    2012-03-26

    Functional measurement is important for retinal study and disease diagnosis. Transient intrinsic optical signal (IOS) response, tightly correlated with functional stimulation, has been previously detected in normal retinas. In this paper, comparative IOS imaging of wild-type (WT) and rod-degenerated mutant mouse retinas is reported. Both 2-month and 1-year-old mice were measured. In 2-month-old mutant mice, time course and peak value of the stimulus-evoked IOS were significantly delayed (relative to stimulus onset) and reduced, respectively, compared to age matched WT mice. In 1-year-old mutant mice, stimulus-evoked IOS was totally absent. However, enhanced spontaneous IOS responses, which might reflect inner neural remodeling in diseased retina, were observed in both 2-month and 1-year-old mutant retinas. Our experiments demonstrate the potential of using IOS imaging for noninvasive and high resolution identification of disease-associated retinal dysfunctions. Moreover, high spatiotemporal resolution IOS imaging may also lead to advanced understanding of disease-associated neural remodeling in the retina.

  6. Comparative intrinsic optical signal imaging of wild-type and mutant mouse retinas

    PubMed Central

    Zhang, Qiu-Xiang; Zhang, Youwen; Lu, Rong-Wen; Li, Yi-Chao; Pittler, Steven J.; Kraft, Timothy W.; Yao, Xin-Cheng

    2012-01-01

    Functional measurement is important for retinal study and disease diagnosis. Transient intrinsic optical signal (IOS) response, tightly correlated with functional stimulation, has been previously detected in normal retinas. In this paper, comparative IOS imaging of wild-type (WT) and rod-degenerated mutant mouse retinas is reported. Both 2-month and 1-year-old mice were measured. In 2-month-old mutant mice, time course and peak value of the stimulus-evoked IOS were significantly delayed (relative to stimulus onset) and reduced, respectively, compared to age matched WT mice. In 1-year-old mutant mice, stimulus-evoked IOS was totally absent. However, enhanced spontaneous IOS responses, which might reflect inner neural remodeling in diseased retina, were observed in both 2-month and 1-year-old mutant retinas. Our experiments demonstrate the potential of using IOS imaging for noninvasive and high resolution identification of disease-associated retinal dysfunctions. Moreover, high spatiotemporal resolution IOS imaging may also lead to advanced understanding of disease-associated neural remodeling in the retina. PMID:22453443

  7. In Vivo Confocal Intrinsic Optical Signal Identification of Localized Retinal Dysfunction

    PubMed Central

    Zhang, Qiu-Xiang; Lu, Rong-Wen; Curcio, Christine A.; Yao, Xin-Cheng

    2012-01-01

    Purpose. The purposes of this study were to investigate the physiological mechanism of stimulus-evoked fast intrinsic optical signals (IOSs) recorded in dynamic confocal imaging of the retina, and to demonstrate the feasibility of in vivo confocal IOS mapping of localized retinal dysfunctions. Methods. A rapid line-scan confocal ophthalmoscope was constructed to achieve in vivo confocal IOS imaging of frog (Rana pipiens) retinas at cellular resolution. In order to investigate the physiological mechanism of confocal IOS, comparative IOS and electroretinography (ERG) measurements were made using normal frog eyes activated by variable-intensity stimuli. A dynamic spatiotemporal filtering algorithm was developed to reject the contamination of hemodynamic changes on fast IOS recording. Laser-injured frog eyes were employed to test the potential of confocal IOS mapping of localized retinal dysfunctions. Results. Comparative IOS and ERG experiments revealed a close correlation between the confocal IOS and retinal ERG, particularly the ERG a-wave, which has been widely used to evaluate photoreceptor function. IOS imaging of laser-injured frog eyes indicated that the confocal IOS could unambiguously detect localized (30 μm) functional lesions in the retina before a morphological abnormality is detectable. Conclusions. The confocal IOS predominantly results from retinal photoreceptors, and can be used to map localized photoreceptor lesion in laser-injured frog eyes. We anticipate that confocal IOS imaging can provide applications in early detection of age-related macular degeneration, retinitis pigmentosa, and other retinal diseases that can cause pathological changes in the photoreceptors. PMID:23150616

  8. In vivo confocal intrinsic optical signal identification of localized retinal dysfunction.

    PubMed

    Zhang, Qiu-Xiang; Lu, Rong-Wen; Curcio, Christine A; Yao, Xin-Cheng

    2012-12-13

    The purposes of this study were to investigate the physiological mechanism of stimulus-evoked fast intrinsic optical signals (IOSs) recorded in dynamic confocal imaging of the retina, and to demonstrate the feasibility of in vivo confocal IOS mapping of localized retinal dysfunctions. A rapid line-scan confocal ophthalmoscope was constructed to achieve in vivo confocal IOS imaging of frog (Rana pipiens) retinas at cellular resolution. In order to investigate the physiological mechanism of confocal IOS, comparative IOS and electroretinography (ERG) measurements were made using normal frog eyes activated by variable-intensity stimuli. A dynamic spatiotemporal filtering algorithm was developed to reject the contamination of hemodynamic changes on fast IOS recording. Laser-injured frog eyes were employed to test the potential of confocal IOS mapping of localized retinal dysfunctions. Comparative IOS and ERG experiments revealed a close correlation between the confocal IOS and retinal ERG, particularly the ERG a-wave, which has been widely used to evaluate photoreceptor function. IOS imaging of laser-injured frog eyes indicated that the confocal IOS could unambiguously detect localized (30 μm) functional lesions in the retina before a morphological abnormality is detectable. The confocal IOS predominantly results from retinal photoreceptors, and can be used to map localized photoreceptor lesion in laser-injured frog eyes. We anticipate that confocal IOS imaging can provide applications in early detection of age-related macular degeneration, retinitis pigmentosa, and other retinal diseases that can cause pathological changes in the photoreceptors.

  9. Neuronal and Astroglial Correlates Underlying Spatiotemporal Intrinsic Optical Signal in the Rat Hippocampal Slice

    PubMed Central

    Pál, Ildikó; Nyitrai, Gabriella; Kardos, Julianna; Héja, László

    2013-01-01

    Widely used for mapping afferent activated brain areas in vivo, the label-free intrinsic optical signal (IOS) is mainly ascribed to blood volume changes subsequent to glial glutamate uptake. By contrast, IOS imaged in vitro is generally attributed to neuronal and glial cell swelling, however the relative contribution of different cell types and molecular players remained largely unknown. We characterized IOS to Schaffer collateral stimulation in the rat hippocampal slice using a 464-element photodiode-array device that enables IOS monitoring at 0.6 ms time-resolution in combination with simultaneous field potential recordings. We used brief half-maximal stimuli by applying a medium intensity 50 Volt-stimulus train within 50 ms (20 Hz). IOS was primarily observed in the str. pyramidale and proximal region of the str. radiatum of the hippocampus. It was eliminated by tetrodotoxin blockade of voltage-gated Na+ channels and was significantly enhanced by suppressing inhibitory signaling with gamma-aminobutyric acid(A) receptor antagonist picrotoxin. We found that IOS was predominantly initiated by postsynaptic Glu receptor activation and progressed by the activation of astroglial Glu transporters and Mg2+-independent astroglial N-methyl-D-aspartate receptors. Under control conditions, role for neuronal K+/Cl− cotransporter KCC2, but not for glial Na+/K+/Cl− cotransporter NKCC1 was observed. Slight enhancement and inhibition of IOS through non-specific Cl− and volume-regulated anion channels, respectively, were also depicted. High-frequency IOS imaging, evoked by brief afferent stimulation in brain slices provide a new paradigm for studying mechanisms underlying IOS genesis. Major players disclosed this way imply that spatiotemporal IOS reflects glutamatergic neuronal activation and astroglial response, as observed within the hippocampus. Our model may help to better interpret in vivo IOS and support diagnosis in the future. PMID:23469218

  10. Neuronal and astroglial correlates underlying spatiotemporal intrinsic optical signal in the rat hippocampal slice.

    PubMed

    Pál, Ildikó; Nyitrai, Gabriella; Kardos, Julianna; Héja, László

    2013-01-01

    Widely used for mapping afferent activated brain areas in vivo, the label-free intrinsic optical signal (IOS) is mainly ascribed to blood volume changes subsequent to glial glutamate uptake. By contrast, IOS imaged in vitro is generally attributed to neuronal and glial cell swelling, however the relative contribution of different cell types and molecular players remained largely unknown. We characterized IOS to Schaffer collateral stimulation in the rat hippocampal slice using a 464-element photodiode-array device that enables IOS monitoring at 0.6 ms time-resolution in combination with simultaneous field potential recordings. We used brief half-maximal stimuli by applying a medium intensity 50 Volt-stimulus train within 50 ms (20 Hz). IOS was primarily observed in the str. pyramidale and proximal region of the str. radiatum of the hippocampus. It was eliminated by tetrodotoxin blockade of voltage-gated Na(+) channels and was significantly enhanced by suppressing inhibitory signaling with gamma-aminobutyric acid(A) receptor antagonist picrotoxin. We found that IOS was predominantly initiated by postsynaptic Glu receptor activation and progressed by the activation of astroglial Glu transporters and Mg(2+)-independent astroglial N-methyl-D-aspartate receptors. Under control conditions, role for neuronal K(+)/Cl(-) cotransporter KCC2, but not for glial Na(+)/K(+)/Cl(-) cotransporter NKCC1 was observed. Slight enhancement and inhibition of IOS through non-specific Cl(-) and volume-regulated anion channels, respectively, were also depicted. High-frequency IOS imaging, evoked by brief afferent stimulation in brain slices provide a new paradigm for studying mechanisms underlying IOS genesis. Major players disclosed this way imply that spatiotemporal IOS reflects glutamatergic neuronal activation and astroglial response, as observed within the hippocampus. Our model may help to better interpret in vivo IOS and support diagnosis in the future.

  11. Elicitation interval dependent spatiotemporal evolution of cortical spreading depression waves revealed by optical intrinsic signal imaging

    NASA Astrophysics Data System (ADS)

    Chen, Shangbin; Gong, Hui; Zeng, Shaoqun; Luo, Qingming; Li, Pengcheng

    2007-02-01

    This study aimed to investigate the variation of propagation patterns of successive cortical spreading depression (CSD) waves induced by K + or pinprick in rat cortex. In the K + induction group, 18 Sprague-Dawley rats under Î+/--chloralose/urethane anesthesia were used to elicit CSD by 1 M KCl solution in the frontal cortex. Optical intrinsic signal imaging (OISI) at an isosbestic point of hemoglobin (550 nm) was applied to examine regional cerebral blood volume (CBV) changes in the parieto-occipital cortex. In 6 of the 18 rats, OISI was performed in conjunction with DC potential recording of the cortex. The results of this group were reported previously. In the pinprick group, 6 rats were used to induce CSD by pinprick with 8 min interval, and the other 6 rats were pricked with 4 min. CBV changes during CSD appeared as repetitive propagation of wave-like hyperemia at a speed of 3.7+/-0.4 mm/min, which was characterized by a significant negative peak (-14.3+/-3.2%) in the reflectance signal. Except for the first CSD wave, the following waves don't spread fully in the observed cortex all the time and they might abort in the medial area. Independent on the stimulation of pinprick or K+, a short interval of the current CSD to the last CSD no more than 4 min would induce the current CSD be partially propagated. For the first time, the data reveals the time-varying propagation patterns of CSD waves might be affected by the interval between CSD waves. The results suggest that the propagation patterns of a series of CSD waves are time-varying in different regions of rat cortex, and the variation is related to the interval between CSD waves.

  12. Impact of motion-associated noise on intrinsic optical signal imaging in humans with optical coherence tomography

    PubMed Central

    Teussink, Michel M.; Cense, Barry; van Grinsven, Mark J.J.P.; Klevering, B. Jeroen; Hoyng, Carel B.; Theelen, Thomas

    2015-01-01

    A growing body of evidence suggests that phototransduction can be studied in the human eye in vivo by imaging of fast intrinsic optical signals (IOS). There is consensus concerning the limiting influence of motion-associated imaging noise on the reproducibility of IOS-measurements, especially in those employing spectral-domain optical coherence tomography (SD-OCT). However, no study to date has conducted a comprehensive analysis of this noise in the context of IOS-imaging. In this study, we discuss biophysical correlates of IOS, and we address motion-associated imaging noise by providing correctional post-processing methods. In order to avoid cross-talk of adjacent IOS of opposite signal polarity, cellular resolution and stability of imaging to the level of individual cones is likely needed. The optical Stiles-Crawford effect can be a source of significant IOS-imaging noise if alignment with the peak of the Stiles-Crawford function cannot be maintained. Therefore, complete head stabilization by implementation of a bite-bar may be critical to maintain a constant pupil entry position of the OCT beam. Due to depth-dependent sensitivity fall-off, heartbeat and breathing associated axial movements can cause tissue reflectivity to vary by 29% over time, although known methods can be implemented to null these effects. Substantial variations in reflectivity can be caused by variable illumination due to changes in the beam pupil entry position and angle, which can be reduced by an adaptive algorithm based on slope-fitting of optical attenuation in the choriocapillary lamina. PMID:26137369

  13. Intrinsic Signal Optical Imaging Evidence for Dorsal V3 in the Prosimian Galago (Otolemur garnettii)

    PubMed Central

    Fan, Reuben H.; Baldwin, Mary K.L.; Jermakowicz, Walter J.; Casagrande, Vivien A.; Kaas, Jon H.; Roe, Anna W.

    2013-01-01

    Currently, we lack consensus regarding the organization along the anterior border of dorsomedial V2 in primates. Previous studies suggest that this region could be either the dorsomedial area, characterized by both an upper and a lower visual field representation, or the dorsal aspect of area V3, which only contains a lower visual field representation. We examined these proposals by using optical imaging of intrinsic signals to investigate this region in the prosimian galago (Otole-mur garnettii). Galagos represent the prosimian radiation of surviving primates; cortical areas that bear strong resemblances across members of primates provide a strong argument for their early origin and conserved existence. Based on our mapping of horizontal and vertical meridian representations, visuotopy, and orientation preference, we find a clear lower field representation anterior to dorsal V2 but no evidence of any upper field representation. We also show statistical differences in orientation preference patches between V2 and V3. We additionally supplement our imaging results with electrode array data that reveal differences in the average spatial frequency preference, average temporal frequency preference, and sizes of the receptive fields between V1, V2, and V3. The lack of upper visual field representation along with the differences between the neighboring visual areas clearly distinguish the region anterior to dorsal V2 from earlier visual areas and argue against a DM that lies along the dorsomedial border of V2. We submit that the region of the cortex in question is the dorsal aspect of V3, thus strengthening the possibility that V3 is conserved among primates. PMID:22628051

  14. Imaging Single Photons and Intrinsic Optical Signals for Studies of Vesicular and Non-Vesicular ATP Release from Axons

    PubMed Central

    Fields, R. Douglas

    2011-01-01

    The temporal and spatial dynamics of neurotransmitter release are fundamental to understanding activity-dependent signaling between axons and other cells, including neurons, glia, and vascular cells. A microscopic imaging technique is described that enables studying release of the neurotransmitter ATP from axons in response to action potentials. The method combines imaging single-photons, intrinsic optical signal imaging, and high magnification time-lapse microcopy to enable investigations of action potential-induced ATP release together with cell morphology and activity-dependent axon swelling. ATP released from axons catalyzes a chemiluminescent reaction between luciferin and luciferase that generates single photons that can be imaged individually. In addition to vesicular release, ATP release through membrane channels activated by axon swelling was monitored simultaneously with intrinsic optical signals. Repeated emissions of photons were observed from localized 15 μm regions of axons, with a frequency distribution that differed from a normal distribution and from the frequency of emissions outside these localized regions. PMID:21852965

  15. High speed line-scan confocal imaging of stimulus-evoked intrinsic optical signals in the retina

    PubMed Central

    Li, Yang-Guo; Liu, Lei; Amthor, Franklin; Yao, Xin-Cheng

    2010-01-01

    A rapid line-scan confocal imager was developed for functional imaging of the retina. In this imager, an acousto-optic deflector (AOD) was employed to produce mechanical vibration- and inertia-free light scanning, and a high-speed (68,000 Hz) linear CCD camera was used to achieve sub-cellular and sub-millisecond spatiotemporal resolution imaging. Two imaging modalities, i.e., frame-by-frame and line-by-line recording, were validated for reflected light detection of intrinsic optical signals (IOSs) in visible light stimulus activated frog retinas. Experimental results indicated that fast IOSs were tightly correlated with retinal stimuli, and could track visible light flicker stimulus frequency up to at least 2 Hz. PMID:20125743

  16. Plastic Change along the Intact Crossed Pathway in Acute Phase of Cerebral Ischemia Revealed by Optical Intrinsic Signal Imaging

    PubMed Central

    Guo, Xiaoli; He, Yongzhi; Lu, Hongyang; Li, Yao; Su, Xin; Jiang, Ying; Tong, Shanbao

    2016-01-01

    The intact crossed pathway via which the contralesional hemisphere responds to the ipsilesional somatosensory input has shown to be affected by unilateral stroke. The aim of this study was to investigate the plasticity of the intact crossed pathway in response to different intensities of stimulation in a rodent photothrombotic stroke model. Using optical intrinsic signal imaging, an overall increase of the contralesional cortical response was observed in the acute phase (≤48 hours) after stroke. In particular, the contralesional hyperactivation is more prominent under weak stimulations, while a strong stimulation would even elicit a depressed response. The results suggest a distinct stimulation-response pattern along the intact crossed pathway after stroke. We speculate that the contralesional hyperactivation under weak stimulations was due to the reorganization for compensatory response to the weak ipsilateral somatosensory input. PMID:27144032

  17. Intrinsic optical modulation mechanism in electro-optic crystals

    NASA Astrophysics Data System (ADS)

    Garzarella, A.; Hinton, R. J.; Qadri, S. B.; Wu, Dong Ho

    2008-06-01

    An intrinsic mechanism of optical intensity modulation occurring in electro-optic devices such as field sensors and modulators under applied fields is described. The optical modulation results from interactions between internally generated Fizeau interference patterns and electro-optic effects within the nonlinear crystal. Our results indicate that when phase matched with the conventional polarimetric signal, the intrinsic modulation mechanism can nearly double device sensitivity.

  18. Imaging nanomaterials in vitro and in vivo by exploring their intrinsic nonlinear optical signals

    NASA Astrophysics Data System (ADS)

    Tong, Ling

    The extension of nanotechnology to biomedical system creates a new and fast developing field, nanomedicine. A wide range of nanoparticles has been developed as imaging agents or drug carriers. However, the translation of nanomedicines to a clinical setting has been slowed down due to a limited fundamental understanding of the nano-bio interaction. My thesis work describes the efforts in imaging the behavior of nanomaterials in live cells and animals by exploring the nonlinear optical properties. The first part of my thesis focuses on study of metallic and semiconducting nanoparticles in biological environment using their nonlinear optical signals. In chapter 2, systemic circulation of PEGylated gold nanorods (GNRs) is visualized by intravital two-photon luminescence (TPL) imaging. A biphasic clearance is demonstrated with branched PEG showing longer circulation. Following clearance, cellular biodistribution of GNRs in organs is mapped by TPL imaging. GNRs accumulate in macrophages in liver and spleen (Langmuir, 2009, 25, 12454-12459). In chapter 3, a bright three-photon luminescence is discovered from Au-Ag alloyed nanostructure by excitation with a femtosecond laser at 1290 nm, which enables bio-imaging with negligible photothermal toxicity and tissue autofluorescence (Angew Chemie, 2010, 49, 3485-3488, inside cover story). In chapter 4, a new contrast is invented for label-free, real-time imaging of single-walled carbon nanotubes (SWNTs) by pump-probe microscopy. At pump/probe wavelength of 707 and 885 nm, semiconducting and metallic SWNTs (S-SWNTs and M-SWNTs) exhibit intense stimulated emission and absorption signals, which allow us to monitor the intracellular trafficking, distribution in tissues, and systemic circulation in vivo with single-nanotube sensitivity and sub-micron resolution. The second part presents label-free imaging of nanomedicines in live cells by coherent anti-Stokes Raman scattering (CARS) and stimulated Raman scattering (SRS) microscopy

  19. Simple and cost-effective hardware and software for functional brain mapping using intrinsic optical signal imaging.

    PubMed

    Harrison, Thomas C; Sigler, Albrecht; Murphy, Timothy H

    2009-09-15

    We describe a simple and low-cost system for intrinsic optical signal (IOS) imaging using stable LED light sources, basic microscopes, and commonly available CCD cameras. IOS imaging measures activity-dependent changes in the light reflectance of brain tissue, and can be performed with a minimum of specialized equipment. Our system uses LED ring lights that can be mounted on standard microscope objectives or video lenses to provide a homogeneous and stable light source, with less than 0.003% fluctuation across images averaged from 40 trials. We describe the equipment and surgical techniques necessary for both acute and chronic mouse preparations, and provide software that can create maps of sensory representations from images captured by inexpensive 8-bit cameras or by 12-bit cameras. The IOS imaging system can be adapted to commercial upright microscopes or custom macroscopes, eliminating the need for dedicated equipment or complex optical paths. This method can be combined with parallel high resolution imaging techniques such as two-photon microscopy.

  20. High-Resolution fMRI Maps of Cortical Activation in Nonhuman Primates: Correlation with Intrinsic Signal Optical Images

    PubMed Central

    Roe, Anna W.; Chen, Li Min

    2009-01-01

    One of the most widely used functional brain mapping tools is blood oxygen level–dependent (BOLD) functional magnetic resonance imaging (fMRI). This method has contributed to new understandings of the functional roles of different areas in the human brain. However, its ability to map cerebral cortex at high spatial (submillimeter) resolution is still unknown. Other methods such as single- and multiunit electrophysiology and intrinsic signal optical imaging have revealed submillimeter resolution of sensory topography and cortical columnar activations. However, they are limited either by spatial scale (electrophysiology characterizes only local groups of neurons) or by the inability to monitor deep structures in the brain (i.e., cortical regions buried in sulci or subcortical structures). A method that could monitor all regions of the brain at high spatial resolution would be ideal. This capacity would open the doors to investigating, for example, how networks of cerebral cortical columns relate to or produce behavior. In this article we demonstrate that, without benefit of contrast agents, at a magnetic field strength of 9.4 tesla, BOLD fMRI can reveal millimeter-sized topographic maps of digit representation in the somatosensory cortex of the anesthetized squirrel monkey. Furthermore, by mapping the “funneling illusion,” it is possible to detect even submillimeter shifts in activation in the cortex. Our data suggest that at high magnetic field strength, the positive BOLD signal can be used to reveal high spatial resolution maps of brain activity, a finding that weakens previous notions about the ultimate spatial specificity of the positive BOLD signal. PMID:18172338

  1. Temporo-Spectral Imaging of Intrinsic Optical Signals during Hypoxia-Induced Spreading Depression-Like Depolarization

    PubMed Central

    Mané, Maria; Müller, Michael

    2012-01-01

    Spreading depression (SD) is characterized by a sustained near-complete depolarization of neurons, a massive depolarization of glia, and a negative deflection of the extracellular DC potential. These electrophysiological signs are accompanied by an intrinsic optical signal (IOS) which arises from changes in light scattering and absorption. Even though the underlying mechanisms are unclear, the IOS serves as non-invasive tool to define the spatiotemporal dynamics of SD in brain slices. Usually the tissue is illuminated by white light, and light reflectance or transmittance is monitored. Using a polychromatic, fast-switchable light source we now performed temporo-spectral recordings of the IOS associated with hypoxia-induced SD-like depolarization (HSD) in rat hippocampal slices kept in an interface recording chamber. Recording full illumination spectra (320–680 nm) yielded distinct reflectance profiles for the different phases of HSD. Early during hypoxia tissue reflectance decreased within almost the entire spectrum due to cell swelling. HSD was accompanied by a reversible reflectance increase being most pronounced at 400 nm and 460 nm. At 440 nm massive porphyrin absorption (Soret band) was detected. Hypotonic solutions, Ca2+-withdrawal and glial poisoning intensified the reflectance increase during HSD, whereas hypertonic solutions dampened it. Replacement of Cl- inverted the reflectance increase. Inducing HSD by cyanide distorted the IOS and reflectance at 340–400 nm increased irreversibly. The pronounced changes at short wavelengths (380 nm, 460 nm) and their cyanide sensitivity suggest that block of mitochondrial metabolism contributes to the IOS during HSD. For stable and reliable IOS recordings during HSD wavelengths of 460–560 nm are recommended. PMID:22952835

  2. Independent component analysis for the detection of in vivo intrinsic signals from an optical imager of retinal function

    NASA Astrophysics Data System (ADS)

    Barriga, Eduardo S.; Pattichis, Marios; Abramoff, Michael; T'so, Dan; Kwon, Young; Kardon, Randy; Soliz, Peter

    2007-02-01

    To overcome the difficulty in detection of loss of retinal activity, a functional-Retinal Imaging Device (f-RID) was developed. The device, which is based on a modified fundus camera, seeks to detect changes in optical signals that reflect functional changes in the retina. Measured changes in reflectance in response to the visual stimulus are on the order of 0.1% to 1% of the total reflected intensity level, which makes the functional signal difficult to detect by standard methods because it is masked by other physiological signals and by noise. In this paper, we present a new Independent Component Analysis (ICA) algorithm used to analyze the video sequences from a set of experiments with different patterned stimuli from cats and humans. The ICA algorithm with priors (ICA-P) uses information about the stimulation paradigms to increase the signal detection thresholds when compared to traditional ICA algorithms. The results of the analysis show that we can detect signal levels as low as 0.01% of the total reflected intensity. Also, improvement of up to 30dB in signal detection over traditional ICA algorithms is achieved. The study found that in more than 80% of the in-vivo experiments the patterned stimuli effects on the retina can be detected and extracted.

  3. Intrinsic determinants of optic nerve regeneration.

    PubMed

    Zhu, Rui-lin; Cho, Kin-sang; Guo, Chen-ying; Chew, Justin; Chen, Dong-feng; Yang, Liu

    2013-07-01

    To review the functions of these intracellular signals in their regulation of retinal ganglion cell (RGC) axon regeneration. Relevant articles published in English or Chinese from 1970 to present were selected from PubMed. Searches were made using the terms "intrinsic determinants, axon regeneration, RGC, optic nerve regeneration, and central nervous system axon regeneration." Articles studying the mechanisms controlling RGC and central nervous system (CNS) axon regeneration were reviewed. Articles focusing on the intrinsic determinants of axon regeneration were selected. Like other CNS neurons of mammals, RGCs undergo a developmental loss in their ability to grow axons as they mature, which is a critical contributing factor to the failure of nerve regeneration and repair after injury. This growth failure can be attributed, at least in part, by the induction of molecular programs preventing cellular overgrowth and termination of axonal growth upon maturation. Key intracellular signals and transcription factors, including B cell lymphoma/leukemia 2, cyclic adenine monophosphate, mammalian target of rapamycin, and Krüppel-like transcription factors, have been identified to play central roles in this process. Intense effort and substantial progress have been made to identify the various intrinsic growth pathways that regulate RGC axon regeneration. More work is needed to elucidate the mechanisms of and the interrelationship between the actions of these factors and to successfully achieve regeneration and repair of the severed RGC axons.

  4. Differences in O2 availability resolve the apparent discrepancies in metabolic intrinsic optical signals in vivo and in vitro

    PubMed Central

    Turner, Dennis A.; Foster, Kelley A.; Galeffi, Francesca; Somjen, George G.

    2012-01-01

    Monitoring changes in the fluorescence of metabolic chromophores, reduced nicotinamide adenine dinucleotide and flavin adenine dinucleotide, and the absorption of cytochromes, is useful to study neuronal activation and mitochondrial metabolism in the brain. However, these optical signals evokedby stimulation, seizures and spreading depression in intact brain differ from those observed in vitro. The responses in vivo consist of a persistent oxidized state during neuronal activity followed by mild reduction during recovery. In vitro, however, brief oxidation is followed by prolonged and heightened reduction, even during persistent neuronal activation. In normally perfused, oxygenated and activated brain tissue in vivo, partial pressure of oxygen (PO2) levels often undergo a brief ‘dip’ that is always followed by an overshoot above baseline, due to increased blood flow (neuronal–vascular coupling). By contrast, in the absence of blood circulation, tissue PO2 in vitro decreases more markedly and recovers slowly to baseline without overshooting. Although oxygen is abundant in vivo, it is diffusion-limited in vitro. The disparities in mitochondrial and tissue oxygen availability account for the different redox responses. PMID:17590447

  5. Large field-of-view movement-compensated intrinsic optical signal imaging for the characterization of the haemodynamic response to spreading depolarizations in large gyrencephalic brains.

    PubMed

    Schöll, Michael Johannes; Santos, Edgar; Sanchez-Porras, Renan; Kentar, Modar; Gramer, Markus; Silos, Humberto; Zheng, Zelong; Gang, Yuan; Strong, Anthony John; Graf, Rudolf; Unterberg, Andreas; Sakowitz, Oliver W; Dickhaus, Hartmut

    2017-05-01

    Haemodynamic responses to spreading depolarizations (SDs) have an important role during the development of secondary brain damage. Characterization of the haemodynamic responses in larger brains, however, is difficult due to movement artefacts. Intrinsic optical signal (IOS) imaging, laser speckle flowmetry (LSF) and electrocorticography were performed in different configurations in three groups of in total 18 swine. SDs were elicited by topical application of KCl or occurred spontaneously after middle cerebral artery occlusion. Movement artefacts in IOS were compensated by an elastic registration algorithm during post-processing. Using movement-compensated IOS, we were able to differentiate between four components of optical changes, corresponding closely with haemodynamic variations measured by LSF. Compared with ECoG and LSF, our setup provides higher spatial and temporal resolution, as well as a better signal-to-noise ratio. Using IOS alone, we could identify the different zones of infarction in a large gyrencephalic middle cerebral artery occlusion pig model. We strongly suggest movement-compensated IOS for the investigation of the role of haemodynamic responses to SDs during the development of secondary brain damage and in particular to examine the effect of potential therapeutic interventions in gyrencephalic brains.

  6. Optical coherence tractography using intrinsic contrast

    PubMed Central

    Goergen, Craig J.; Radhakrishnan, Harsha; Sakadžić, Sava; Mandeville, Emiri T.; Lo, Eng H.; Sosnovik, David E.; Srinivasan, Vivek J.

    2013-01-01

    Organs such as the heart and brain possess intricate fiber structures that are best characterized with threedimensional imaging. For instance, diffusion-based, magnetic resonance tractography (MRT) enables studies of connectivity and remodeling during development and disease macroscopically on the millimeter scale. Here we present complementary, high-resolution microscopic optical coherence imaging and analysis methods that, when used in conjunction with clearing techniques, can characterize fiber architecture in intact organs at tissue depths exceeding 1 mm. We anticipate that these techniques can be used to study fiber architecture in situ at microscopic scales not currently accessible to diffusion magentic resonance (MR), and thus, to validate and complement macroscopic structural imaging techniques. Moreover, as these techniques use intrinsic signals and do not require tissue slicing and staining, they can be used for high-throughput, nondestructive evaluation of fiber architecture across large tissue volumes. PMID:23041891

  7. Characterization of dermal structural assembly in normal and pathological connective tissues by intrinsic signal multiphoton optical microscopy

    NASA Astrophysics Data System (ADS)

    Lyubovitsky, Julia G.; Xu, Xiaoman; Sun, Chung-ho; Andersen, Bogi; Krasieva, Tatiana B.; Tromberg, Bruce J.

    2008-02-01

    Employing a reflectance multi-photon microscopy (MPM) technique, we developed novel method to quantitatively study the three-dimensional assembly of structural proteins within bulk of dermal ECMs. Using a structurally simplified model of skin with enzymatically dissected epidermis, we find that low resolution MPM clearly discriminates between normal and pathological dermis. High-resolution images revealed that the backscattered MPM signals are affected by the assembly of collagen fibrils and fibers within this system. Exposure of tissues to high concentrations of potentially denaturing chemicals also resulted in the reduction of SHG signals from structural proteins which coincided with the appearance of aggregated fluorescent structures.

  8. Optical intrinsic signals in rat primary somatosensory cortex during non-noxious and noxious elecrical stimulation of the sciatic nerve

    NASA Astrophysics Data System (ADS)

    Luo, Weihua; Li, Pengcheng; Chen, Shangbin; Luo, Qingming

    2003-12-01

    Optical imaging method was applied into observing the temporal-spatial characteristic of rat primary somatosensory cortex during graded electrical stimulation of the sciatic nerve (5hz,duration of 2s,0.5ms puls,1x,10x and 20x muscle twitch threshold). We found that the temporal and spatial properties of hindlimb somatosensory cortex were modulated by graded intensity electrical stimulation of the sciatic nerve. The magnitude and time course were larger and longer with the intensity raising. And the spatial extent was wider at 20x stimulus than the other two kinds of stimulus. Therefore, our optical imaging was based on 570nm, which only reflect the changes of blood volume. Then our future study will reveal more information of pain modulation in primary somatosensory cortex.

  9. Control of anoxic depolarization in rat brain by near-infrared laser irradiation and its monitoring by intrinsic optical signal imaging

    NASA Astrophysics Data System (ADS)

    Kawauchi, Satoko; Sato, Shunichi; Uozumi, Yoichi; Nawashiro, Hiroshi; Ishihara, Miya; Ashida, Hiroshi

    2012-03-01

    In brain anoxia or ischemia, spreading depolarization is a key event that deterimines brain tissue survival. After onset of anoxia/ischemia, impairment of energy metabolism causes anoxic/ischemic depolarization (AD), which considerably consumes energy, leading to acute neuronal death in the brain. Our previous intrinsic-optical-signal imaging for the rat brains showed that about 2 min after starting hypoxia, AD-related light-scattering waves were focally generated in the bilateral outermost regions in the cortex and spread toward the midline, indicating that AD can be monitored by lightscattering signal. The behaviors of the scattering waves were found to be correlated with the survival of the rats. In the present study, we used the scattering signal-based monitoring method for AD and examined whether near-infrared laser irradiation can control AD in the rat brains. The left hemisphere was irradiated with 808-nm laser transcranially at 7.5 mW/cm2 before (30 min) and during hypoxia. The onset time of the scattering wave (AD) was significantly delayed in the irradiated hemisphere when compared with that in the non-irradiated hemisphere (3.4 s, n=8). The area of AD spreading in the irradiated hemisphere was significantly smaller than that in the non-irradiated hemisphere (27-90% reduction at 10-50 s after AD onset). These results suggest that near-infrared light can delay and reduce anoxic depolarization in the brain, which is probably due to increase in the cerebral ATP by near-infrared laser irradiation.

  10. Optical diagnosis of cervical cancer by intrinsic mode functions

    NASA Astrophysics Data System (ADS)

    Mukhopadhyay, Sabyasachi; Pratiher, Sawon; Pratiher, Souvik; Pradhan, Asima; Ghosh, Nirmalya; Panigrahi, Prasanta K.

    2017-03-01

    In this paper, we make use of the empirical mode decomposition (EMD) to discriminate the cervical cancer tissues from normal ones based on elastic scattering spectroscopy. The phase space has been reconstructed through decomposing the optical signal into a finite set of bandlimited signals known as intrinsic mode functions (IMFs). It has been shown that the area measure of the analytic IMFs provides a good discrimination performance. Simulation results validate the efficacy of the IMFs followed by SVM based classification.

  11. Optical signal processing

    NASA Technical Reports Server (NTRS)

    Casasent, D.

    1978-01-01

    The article discusses several optical configurations used for signal processing. Electronic-to-optical transducers are outlined, noting fixed window transducers and moving window acousto-optic transducers. Folded spectrum techniques are considered, with reference to wideband RF signal analysis, fetal electroencephalogram analysis, engine vibration analysis, signal buried in noise, and spatial filtering. Various methods for radar signal processing are described, such as phased-array antennas, the optical processing of phased-array data, pulsed Doppler and FM radar systems, a multichannel one-dimensional optical correlator, correlations with long coded waveforms, and Doppler signal processing. Means for noncoherent optical signal processing are noted, including an optical correlator for speech recognition and a noncoherent optical correlator.

  12. Spectroscopic analysis of skin intrinsic signals for multiphoton microscopy

    NASA Astrophysics Data System (ADS)

    Pena, Ana-Maria; Strupler, Mathias; Boulesteix, Thierry; Senni, Karim; Godeau, Gaston; Beaurepaire, Emmanuel; Schanne-Klein, Marie-Claire

    2006-02-01

    We recorded multiphoton images of human skin biopsies using endogenous sources of nonlinear optical signals. We detected simultaneously two-photon excited fluorescence (2PEF) from intrinsic fluorophores and second harmonic generation (SHG) from collagen. We observed SHG from fibrillar collagens in the dermis, whereas no SHG was detectable from the non fibrillar type IV collagen in the basal laminae. We compared these distinct behaviours of collagens I and IV in SHG microscopy to polarization-resolved surface SHG experiments on thin films of collagens I and IV molecules. We observed similar signals for both types of molecular films, except for the chiroptical contributions which are present only for collagen I and enhance the signal typically by a factor of 2. We concluded that SHG microscopy is a sensitive probe of the micrometer-scale structural organization of collagen in biological tissues. In order to elucidate the origin of the endogenous fluorescence signals, we recorded 2PEF spectra at various positions in the skin biopsies, and compared these data to in vitro spectroscopic analysis. In particular, we studied the keratin fluorescence and determined its 2PEF action cross section. We observed a good agreement between 2PEF spectra recorded in the keratinized upper layers of the epidermis and in a solution of purified keratin. Finally, to illustrate the capabilities of this technique, we recorded 2PEF/SHG images of skin biopsies obtained from patients of various ages.

  13. Optical signal computing

    NASA Astrophysics Data System (ADS)

    Cathey, Wade Thomas; Schmidt, Rodney A.; Moddel, Garret

    1989-12-01

    Architectures for optical symbolic computing were designed, devices were designed and built that were specifically for the architectures, and test circuits for some of the logic elements were designed, constructed, and operated. The research elements were designed, constructed, and operated. The research led to novel architectures for optical symbolic computing. Devices were developed that are suitable for optical 2-D memory and logic. These devices are pixilated photo-addressed spatial light modulators (SLMs) with a three terminal arrangement so that the threshold can be adjusted. Spinoff non-pixilated devices are useful as high frame rate, high resolution SLMs that can be used for many optical signal processing applications.

  14. Optical Signal Processing.

    DTIC Science & Technology

    1986-10-31

    8217 \\..\\ We let k be the ratio of the time base of the reference\\ \\ . signal to that of the received signal. PAU~ ~; II .~** We could analyze this case for an...decreases. The central to the approximation usually stated in optics texts. lobe of the pattern just covers the region II :s I when k We claimed...Reference Waveforms for Heterodyne Spectrum Analyzers K We previously developed the use of a distributed local oscillator, generated by a reference wavefront

  15. Effects of Optical Blur Reduction on Equivalent Intrinsic Blur

    PubMed Central

    Valeshabad, Ali Kord; Wanek, Justin; McAnany, J. Jason; Shahidi, Mahnaz

    2015-01-01

    Purpose To determine the effect of optical blur reduction on equivalent intrinsic blur, an estimate of the blur within the visual system, by comparing optical and equivalent intrinsic blur before and after adaptive optics (AO) correction of wavefront error. Methods Twelve visually normal individuals (age; 31 ± 12 years) participated in this study. Equivalent intrinsic blur (σint) was derived using a previously described model. Optical blur (σopt) due to high-order aberrations was quantified by Shack-Hartmann aberrometry and minimized using AO correction of wavefront error. Results σopt and σint were significantly reduced and visual acuity (VA) was significantly improved after AO correction (P ≤ 0.004). Reductions in σopt and σint were linearly dependent on the values before AO correction (r ≥ 0.94, P ≤ 0.002). The reduction in σint was greater than the reduction in σopt, although it was marginally significant (P = 0.05). σint after AO correlated significantly with σint before AO (r = 0.92, P < 0.001) and the two parameters were related linearly with a slope of 0.46. Conclusions Reduction in equivalent intrinsic blur was greater than the reduction in optical blur due to AO correction of wavefront error. This finding implies that VA in subjects with high equivalent intrinsic blur can be improved beyond that expected from the reduction in optical blur alone. PMID:25785538

  16. Optical signal processing

    NASA Astrophysics Data System (ADS)

    Dorey, J.

    The theoretical principles, design, and application of optical signal-processing devices are examined in a general review and illustrated with diagrams, with an emphasis on their use in radar, sonar, and lidar systems. Topics discussed include Fourier and Fresnel transforms, coherent-light computer techniques (film, electrooptical acoustooptical, and hybrid recording methods; processing of SLAR data; the convolution theorem in coherent optics; and the use of spatial or temporal integration in acoustooptic components), and incoherent-light techniques (the Mertz setup, mask correlation, elimination of spurious components, localization and imaging of EM or IR sources by a mobile-mask technique, and processing of vectors and matrices). The need to compress the output data of high-speed optical processors by detection, thresholding, or (possibly nonlinear) block-recognition functions related to extraction and decision-making processes is stressed, since otherwise digital processing of the output causes a bottleneck effect which negates the speed advantages of optical systems over all-digital solutions.

  17. Intrinsic Fluctuations, Robustness and Tunability in Signaling Cycles.

    NASA Astrophysics Data System (ADS)

    Levine, Joseph; Kueh, Hao Yuan; Mirny, Leonid

    2006-03-01

    Covalent modification cycles (e.g. phosphorylation) underlie most cellular signaling. Low molecular copy number, arising from compartmental segregation and slow diffusion between compartments, potentially renders these cycles vulnerable to intrinsic chemical fluctuations. How can a cell operate reliably in the presence of this inherent stochasticity? How do changes in extrinsic parameters lead to variability of response? Can cells exploit these parameters to tune cycles to different ranges of stimuli? We study the dynamics of an isolated phosphorylation cycle. Our model shows that the cycle transmits information reliably if it is tuned to an optimal parameter range, in spite of intrinsic fluctuations and even for small input signal amplitudes. At the same time, the cycle is sensitive to changes in the concentration and activity of kinases and phosphatases. This sensitivity can lead to significant cell-to-cell response variability Our results show that signaling cycles possess a surprising combination of robustness and tunability. This combination makes them ubiquitous in eukaryotic signaling, optimizing signaling in the presence of fluctuations using their inherent flexibility. On the other hand, cycles tuned to suppress intrinsic fluctuations can be fragile to changes in the number and activity of kinases and phosphatases. Such trade-offs in robustness to fluctuations can influence the evolution of signaling cascades, making them the weakest links in cellular circuits.

  18. Fiber optic crossbar switch for automatically patching optical signals

    NASA Technical Reports Server (NTRS)

    Bell, C. H. (Inventor)

    1983-01-01

    A system for automatically optically switching fiber optic data signals between a plurality of input optical fibers and selective ones of a plurality of output fibers is described. The system includes optical detectors which are connected to each of the input fibers for converting the optic data signals appearing at the respective input fibers to an RF signal. A plurality of RF to optical signal converters are arranged in rows and columns. The output of each of the optical detectors are each applied to a respective row of optical signal converted for being converters back to an optical signal when the particular optical signal converter is selectively activated by a dc voltage.

  19. Optical Signal Processing

    DTIC Science & Technology

    1990-02-28

    compatible with the laser cation in the on-line inspection of products such as source. Thus, if the laser wavelength is z850 nm, hypodermic needles ...content for cw signals, short pulse signals, and evolving pulse signals - - the most difficult ones to analyze. We performed an extensive analysis on a...agreer.nt with the theory , and support our claims concerning the high performance level of our acousto-optir. architecture. We recognized the opportunity to

  20. Optical Computing and Nonlinear Optical Signal Processing

    NASA Astrophysics Data System (ADS)

    Peyghambarian, N.

    1987-01-01

    Employment of optical techniques in signal processing and communication and computing systems has become a major research and development effort at many industrial, government, and university laboratories across the nation and in Europe and Japan. implementation of optical computing concepts and the use of bistable etalons and non-linear logic devices in computing have gained a lot of support and enthusiasm from the optics community in recent years. The significance Iof this field and its potential importance in future technologies is evidenced by the large number of conferences, workshops, and special issues on the subject.

  1. Molecular signaling involving intrinsically disordered proteins in prostate cancer

    PubMed Central

    Russo, Anna; Manna, Sara La; Novellino, Ettore; Malfitano, Anna Maria; Marasco, Daniela

    2016-01-01

    Investigations on cellular protein interaction networks (PINs) reveal that proteins that constitute hubs in a PIN are notably enriched in Intrinsically Disordered Proteins (IDPs) compared to proteins that constitute edges, highlighting the role of IDPs in signaling pathways. Most IDPs rapidly undergo disorder-to-order transitions upon binding to their biological targets to perform their function. Conformational dynamics enables IDPs to be versatile and to interact with a broad range of interactors under normal physiological conditions where their expression is tightly modulated. IDPs are involved in many cellular processes such as cellular signaling, transcriptional regulation, and splicing; thus, their high-specificity/low-affinity interactions play crucial roles in many human diseases including cancer. Prostate cancer (PCa) is one of the leading causes of cancer-related mortality in men worldwide. Therefore, identifying molecular mechanisms of the oncogenic signaling pathways that are involved in prostate carcinogenesis is crucial. In this review, we focus on the aspects of cellular pathways leading to PCa in which IDPs exert a primary role. PMID:27212129

  2. Intrinsic disorder mediates cooperative signal transduction in STIM1.

    PubMed

    Furukawa, Yukio; Teraguchi, Shunsuke; Ikegami, Takahisa; Dagliyan, Onur; Jin, Lin; Hall, Damien; Dokholyan, Nikolay V; Namba, Keiichi; Akira, Shizuo; Kurosaki, Tomohiro; Baba, Yoshihiro; Standley, Daron M

    2014-05-15

    Intrinsically disordered domains have been reported to play important roles in signal transduction networks by introducing cooperativity into protein-protein interactions. Unlike intrinsically disordered domains that become ordered upon binding, the EF-SAM domain in the stromal interaction molecule (STIM) 1 is distinct in that it is ordered in the monomeric state and partially unfolded in its oligomeric state, with the population of the two states depending on the local Ca(2+) concentration. The oligomerization of STIM1, which triggers extracellular Ca(2+) influx, exhibits cooperativity with respect to the local endoplasmic reticulum Ca(2+) concentration. Although the physiological importance of the oligomerization reaction is well established, the mechanism of the observed cooperativity is not known. Here, we examine the response of the STIM1 EF-SAM domain to changes in Ca(2+) concentration using mathematical modeling based on in vitro experiments. We find that the EF-SAM domain partially unfolds and dimerizes cooperatively with respect to Ca(2+) concentration, with Hill coefficients and half-maximal activation concentrations very close to the values observed in vivo for STIM1 redistribution and extracellular Ca(2+) influx. Our mathematical model of the dimerization reaction agrees quantitatively with our analytical ultracentrifugation-based measurements and previously published free energies of unfolding. A simple interpretation of these results is that Ca(2+) loss effectively acts as a denaturant, enabling cooperative dimerization and robust signal transduction. We present a structural model of the Ca(2+)-unbound EF-SAM domain that is consistent with a wide range of evidence, including resistance to proteolytic cleavage of the putative dimerization portion.

  3. Intrinsic Fabry-Perot optical fiber sensors and their multiplexing

    DOEpatents

    Wang, Anbo

    2007-12-11

    An intrinsic Fabry-Perot optical sensor includes a thin film sandwiched between two fiber ends. When light is launched into the fiber, two reflections are generated at the two fiber/thin film interfaces due to a difference in refractive indices between the fibers and the film, giving rise to the sensor output. In another embodiment, a portion of the cladding of a fiber is removed, creating two parallel surfaces. Part of the evanescent fields of light propagating in the fiber is reflected at each of the surfaces, giving rise to the sensor output. In a third embodiment, the refractive index of a small portion of a fiber is changed through exposure to a laser beam or other radiation. Interference between reflections at the ends of the small portion give rise to the sensor output. Multiple sensors along a single fiber are multiplexed using an optical time domain reflectometry method.

  4. Optical Signal Processing.

    DTIC Science & Technology

    1983-11-30

    This pressure wave, in turn, causes an index of refraction change that modulates the light in space and time. The acoustic wave, as it propagates away...used to convert an electrical waveform f(t to an tion on FrW.t) and the inherent dynamic range lini- optical waveform that is a function of both space ...34 21) If we have R photodetectors per resolvable frequency. 2 I.i.Pp) 2dp 2.mi.4’LC, v13) the center spacing is /RT. and, if the duty cycle is O

  5. Optical Signal Processing

    DTIC Science & Technology

    1993-07-30

    publication by Applied Optics. I I i i I I I I I 3 Detection of Short Pulses by Fresnel Preprocessing by i Michael J . Wardlaw NSWCIDL, Code F44 Dahlgren, Va...is included in Appendix J . M. J . Wardlaw performed experimental work on the detection of short pulses by Fresnel3 preprocessing. In the experimental...Fourier transformations," Appl. Opt., Vol 32, p. 3761-3771 (1993) 3 12. M. J . Wardlaw , "Detection of short pulses by Fresnel preprocessing," Accepted for

  6. Intrinsic optical bistability in a strongly driven Rydberg ensemble

    NASA Astrophysics Data System (ADS)

    de Melo, Natalia R.; Wade, Christopher G.; Šibalić, Nikola; Kondo, Jorge M.; Adams, Charles S.; Weatherill, Kevin J.

    2016-06-01

    We observe and characterize intrinsic optical bistability in a dilute Rydberg vapor. The bistability is characterized by sharp jumps between states of low and high Rydberg occupancy with jump-up and -down positions displaying hysteresis depending on the direction in which the control parameter is changed. We find that the shift in frequency of the jump point scales with the fourth power of the principal quantum number. Also, the width of the hysteresis window increases with increasing principal quantum number, before reaching a peak and then closing again. The experimental results are consistent with predictions from a simple theoretical model based on semiclassical Maxwell-Bloch equations including the effects of interaction-induced broadening and level shifts. These results provide insight into the dynamics of driven dissipative systems.

  7. Fiber-optic intrinsic distributed acoustic emission sensor for large structure health monitoring.

    PubMed

    Liang, Sheng; Zhang, Chunxi; Lin, Wentai; Li, Lijing; Li, Chen; Feng, Xiujuan; Lin, Bo

    2009-06-15

    A fiber-optic intrinsic distributed acoustic emission (AE) sensor is proposed. By measuring the time delay of two signals from two Mach-Zehnder interferometers, the location of AE can be deduced, and the corresponding sensor is experimentally verified to be feasible with a 206 m average location error in a 20 km sensing range, which shows that this proposed sensor is applicable for distributed AE sensing for large structure health monitoring, with the unique advantages of low cost, simple configuration, and long sensing range. The limitations of the proposed sensor are also discussed, and the future work is presented.

  8. Exogenous modulation of intrinsic optic nerve neuroprotective activity

    PubMed Central

    Lazic, Tatjana; Kuehn, Markus H.; Harper, Matthew M.; Kardon, Randy H.; Kwon, Young H.; Lavik, Erin B.; Sakaguchi, Donald S.

    2013-01-01

    Background To characterize the molecular and functional status of the rat retina and optic nerve after acute elevation of intraocular pressure (IOP). Methods Retinal ischemia was induced in rats by increasing the IOP (110 mmHg/60 minutes). Microarray analysis, quantitative RT-PCR (qRT-PCR) and immunohistochemistry were used to characterize retinal tissue. PLGA microspheres containing neurotrophic factors (BDNF, GDNF, or CNTF) or empty microspheres were injected into the vitreous of operated animals 1 day after elevation of IOP. Pupil light reflex (PLR) parameters and electroretinograms (ERG) were monitored at multiple time points during the 60-day postoperative recovery period. Results Molecular analysis showed a significant intrinsic up-regulation of CNTF at 10 and 25 days after induction of the acute ocular hypertension (p=0.0067). Molecular tissue analysis of GDNF and its receptors (GDNFR1, GDNFR2), and BDNF and its receptor (trkB) showed no change in expression. Animals that received CNTF microspheres had no significant functional recovery compared to animals which received blank microspheres (p>0.05). Animals that received GDNF or BDNF microspheres showed significant PLR recovery (p<0.05 and p<0.001 respectively) compared to non-treated animals. Conclusions Continuous release of neurotrophic growth factors (NGFs) significantly protects optic nerve function in the experimental model of retinal ischemia observed by PLR analysis. PMID:20229104

  9. Intrinsic Localized Modes in Optical Photonic Lattices and Arrays

    NASA Astrophysics Data System (ADS)

    Christodoulides, Demetrios

    -locking and pulse compression. A strong signature of discrete X-wave formation was also demonstrated in such structures. In the last few years, Anderson localization was unequivocally observed in array systems where the transition from ballistic transport to diffusive, and the cross-over to Anderson localization was studied as a function of disorder and nonlinearity. In recent studies synthetic lattices exhibiting parity-time (PT) symmetry were also considered. The interplay of gain and loss in this latter family of structures leads to counterintuitive characteristics and behavior such as non-reciprocal propagation and power oscillations. The realization of discrete array systems at su-bwavelenth scales is another important direction that is nowadays intensively pursued. References 1. D. N. Christodoulides, F. Lederer, and Y. Silberberg, Nature 424, 817- 823 (2003). 2. F. Lederer, G. I. Stegeman, D. N. Christodoulides, G. Assanto, M. Segev and Y. Silberberg, Phys. Reports 463, 1-126 (2008). 3. M Wimmer, A Regensburger, MA Miri, C. Bersch, D.N Christodoulides, and U. Peschel, ''Observation of optical solitons in PT-symmetric lattices'' Nature Communications 6, 7782 (2015). Intrinsic Localized Modes in Optical Photonic Lattices and Arrays.

  10. Measurement of intrinsic optical backscattering characteristics of cells using fiber-guided near infrared light

    PubMed Central

    2010-01-01

    Background Intrinsic optical signals (IOS), which reflect changes in transmittance and scattering light, have been applied to characterize the physiological conditions of target biological tissues. Backscattering approaches allow mounting of the source and detector on the same side of a sample which creates a more compact physical layout of device. This study presents a compact backscattering design using fiber-optic guided near-infrared (NIR) light to measure the amplitude and phase changes of IOS under different osmotic challenges. Methods High-frequency intensity-modulated light was guided via optic fiber, which was controlled by micromanipulator to closely aim at a minimum cluster of cortical neurons. Several factors including the probe design, wavelength selection, optimal measuring distance between the fiber-optical probe and cells were considered. Our experimental setup was tested in cultured cells to observe the relationship between the changes in backscattered NIR light and cellular IOS, which is believed mainly caused by cell volume changes in hypo/hyperosmotic solutions (± 20, ± 40 and ± 60 mOsm). Results The critical parameters of the current setup including the optimal measuring distance from fiber-optical probe to target tissue and the linear relationship between backscattering intensity and cell volume were determined. The backscattering intensity was found to be inversely proportional to osmotic changes. However, the phase shift exhibited a nonlinear feature and reached a plateau at hyperosmotic solution. Conclusions Our study indicated that the backscattering NIR light guided by fiber-optical probe makes it a potential alternative for continuous observation of intrinsic optical properties of cell culture under varied physical or chemical challenges. PMID:20184751

  11. Optical signal splitting and chirping device modeling

    NASA Astrophysics Data System (ADS)

    Vinogradova, Irina L.; Andrianova, Anna V.; Meshkov, Ivan K.; Sultanov, Albert Kh.; Abdrakhmanova, Guzel I.; Grakhova, Elizaveta P.; Ishmyarov, Arsen A.; Yantilina, Liliya Z.; Kutlieva, Gulnaz R.

    2017-04-01

    This article examines the devices for optical signal splitting and chirping device modeling. Models with splitting and switching functions are taken into consideration. The described device for optical signal splitting and chirping represents interferential splitter with profiled mixer which provides allocation of correspondent spectral component from ultra wide band frequency diapason, and signal phase shift for aerial array (AA) directive diagram control. This paper proposes modeling for two types of devices for optical signal splitting and chirping: the interference-type optical signal splitting and chirping device and the long-distance-type optical signal splitting and chirping device.

  12. Intrinsic fiber optic Sagnac ultrasound sensor for process monitoring in composite structures

    NASA Astrophysics Data System (ADS)

    Fomitchov, Pavel A.; Krishnaswamy, Sridhar; Achenbach, Jan D.

    1999-02-01

    In this paper, we report the development of an intrinsic fiber-optic Sagnac-type ultrasound sensor for cure monitoring. The Sagnac ultrasonic sensor consists of a Sagnac demodulation unit and a sensing segment which can be embedded in a composite structure. The Sagnac optical demodulator is common-path and hence self-stabilized and much simpler than the alternate Fabry-Perot or Michelson type sensors which require external stabilization. Any phase variations that the sampling beams experience due to ultrasound impinging on the sensing segment are demodulated by the Sagnac sensor to produce a signal proportional to ultrasonic signal. The sensing fiber segment of the Sagnac is placed within the composite at the time of manufacture. As the composite is cured, this sensor detects ultrasound that is generated by a laser source or a pzt-transducer. The wavespeed and attenuation of the ultrasound are measured as the cure process proceeds, and these provide information on the state of cure of the composite. We discuss the details of the above intrinsic Sagnac sensor, as well as report on its characteristics including frequency response, sensitivity, and directionality. Results of a cure monitoring are also presented.

  13. Optical investigations of physiology: a study of intrinsic and extrinsic biomedical contrast.

    PubMed Central

    Chance, B; Luo, Q; Nioka, S; Alsop, D C; Detre, J A

    1997-01-01

    The utility and performance of optical studies of tissue depends upon the contrast and the changes of contrast in health and disease and in functional activity. The contrast is determined both by the optical properties of extrinsic chromophores and scatterers but especially upon the changes evoked by physiological activity and pathological states. Here, we have focused upon absorption changes of the intrinsic probe, blood absorbance changes due to cortical hypoxia and to haematomas, giving, for particular conditions, absorbance changes of 0.15 and over 0.4 delta OD, respectively. Functional activity may give changes of blood volume of over 0.05 delta OD with some variability due to individual responses that is best expressed as histogram displays of the distribution of response among a significant population. Responses have been observed in prefrontal parietal and occipital functions (242 tests). Extrinsic probes afford signals dependent upon the dose tolerance of the subject and can readily equal or exceed the blood volume and oxygenation signals, and currently afford vascular volume and flow indications. However, contrast agents for the functional activity of cellular function are ultimately to be expected. Finally, light-scattering changes afford osmolyte-related responses and are here shown to indicate a larger signal attributed to cortical depolarization and K+ release in hypoxia/ischaemia. Thus, the optical method affords imaging of manifold contrasts that greatly enhance its specificity and sensitivity for diagnostic procedures. PMID:9232859

  14. Optical stereo video signal processor

    NASA Technical Reports Server (NTRS)

    Craig, G. D. (Inventor)

    1985-01-01

    An otpical video signal processor is described which produces a two-dimensional cross-correlation in real time of images received by a stereo camera system. The optical image of each camera is projected on respective liquid crystal light valves. The images on the liquid crystal valves modulate light produced by an extended light source. This modulated light output becomes the two-dimensional cross-correlation when focused onto a video detector and is a function of the range of a target with respect to the stereo camera. Alternate embodiments utilize the two-dimensional cross-correlation to determine target movement and target identification.

  15. Waveguide Studies for Fiber Optics and Optical Signal Processing Applications.

    DTIC Science & Technology

    1980-04-01

    beam expander is shown in Fig. 2 -i. The beam, which is expanded to approximately 100 Wm, can be deflected acousto - optically to make a spectrum analyzer...3 2 . DBR Lasers for Fiber Optics and Optical Signal Processing Sources ......... ................. 4 4. Studies of LiNbO 3...6 Chapter 1. Wave Beam Expansion ....... ............. 9 Chapter 2 . DBR Lasers for Fiber Optics and Optical Signal Processing Sources

  16. Intrinsic spin dynamics in optically excited nanoscale magnetic tunnel junction arrays restored by dielectric coating

    NASA Astrophysics Data System (ADS)

    Jaris, M.; Yahagi, Y.; Mahato, B. K.; Dhuey, S.; Cabrini, S.; Nikitin, V.; Stout, J.; Hawkins, A. R.; Schmidt, H.

    2016-11-01

    We report the all-optical observation of intrinsic spin dynamics and extraction of magnetic material parameters from arrays of sub-100 nm spin-transfer torque magnetic random access memory (STT-MRAM) devices with a CoFeB/MgO interface. To this end, the interference of surface acoustic waves with time-resolved magneto-optic signals via magneto-elastic coupling was suppressed using a dielectric coating. The efficacy of this method is demonstrated experimentally and via modeling on a nickel nanomagnet array. The magnetization dynamics for both coated nickel and STT-MRAM arrays shows a restored field-dependent Kittel mode from which the effective damping can be extracted. We observe an increased low-field damping due to extrinsic contributions from magnetic inhomogeneities and variations in the nanomagnet shape, while the intrinsic Gilbert damping remains unaffected by patterning. The data are in excellent agreement with a local resonance model and have direct implications for the design of STT-MRAM devices as well as other nanoscale spintronic technologies.

  17. All-optical signal processing technique for secure optical communication

    NASA Astrophysics Data System (ADS)

    Qian, Feng-chen; Su, Bing; Ye, Ya-lin; Zhang, Qian; Lin, Shao-feng; Duan, Tao; Duan, Jie

    2015-10-01

    Secure optical communication technologies are important means to solve the physical layer security for optical network. We present a scheme of secure optical communication system by all-optical signal processing technique. The scheme consists of three parts, as all-optical signal processing unit, optical key sequence generator, and synchronous control unit. In the paper, all-optical signal processing method is key technology using all-optical exclusive disjunction (XOR) gate based on optical cross-gain modulation effect, has advantages of wide dynamic range of input optical signal, simple structure and so on. All-optical XOR gate composed of two semiconductor optical amplifiers (SOA) is a symmetrical structure. By controlling injection current, input signal power, delay and filter bandwidth, the extinction ratio of XOR can be greater than 8dB. Finally, some performance parameters are calculated and the results are analyzed. The simulation and experimental results show that the proposed method can be achieved over 10Gbps optical signal encryption and decryption, which is simple, easy to implement, and error-free diffusion.

  18. Putamen Activation Represents an Intrinsic Positive Prediction Error Signal for Visual Search in Repeated Configurations

    PubMed Central

    Sommer, Susanne; Pollmann, Stefan

    2016-01-01

    We investigated fMRI responses to visual search targets appearing at locations that were predicted by the search context. Based on previous work in visual category learning we expected an intrinsic reward prediction error signal in the putamen whenever the target appeared at a location that was predicted with some degree of uncertainty. Comparing target appearance at locations predicted with 50% probability to either locations predicted with 100% probability or unpredicted locations, increased activation was observed in left posterior putamen and adjacent left posterior insula. Thus, our hypothesis of an intrinsic prediction error-like signal was confirmed. This extends the observation of intrinsic prediction error-like signals, driven by intrinsic rather than extrinsic reward, to memory-driven visual search. PMID:27867436

  19. Putamen Activation Represents an Intrinsic Positive Prediction Error Signal for Visual Search in Repeated Configurations.

    PubMed

    Sommer, Susanne; Pollmann, Stefan

    2016-01-01

    We investigated fMRI responses to visual search targets appearing at locations that were predicted by the search context. Based on previous work in visual category learning we expected an intrinsic reward prediction error signal in the putamen whenever the target appeared at a location that was predicted with some degree of uncertainty. Comparing target appearance at locations predicted with 50% probability to either locations predicted with 100% probability or unpredicted locations, increased activation was observed in left posterior putamen and adjacent left posterior insula. Thus, our hypothesis of an intrinsic prediction error-like signal was confirmed. This extends the observation of intrinsic prediction error-like signals, driven by intrinsic rather than extrinsic reward, to memory-driven visual search.

  20. Intrinsic noise induced resonance in presence of sub-threshold signal in Brusselator

    NASA Astrophysics Data System (ADS)

    Dey, Supravat; Das, Dibyendu; Parmananda, P.

    2011-09-01

    In a system of non-linear chemical reactions called the Brusselator, we show that intrinsic noise can be regulated to drive it to exhibit resonance in the presence of a sub-threshold signal. The phenomena of periodic stochastic resonance and aperiodic stochastic resonance, hitherto studied mostly with extrinsic noise, is demonstrated here to occur with inherent systemic noise using exact stochastic simulation algorithm due to Gillespie. The role of intrinsic noise in a couple of other phenomena is also discussed.

  1. Electron quantum optics as quantum signal processing

    NASA Astrophysics Data System (ADS)

    Roussel, B.; Cabart, C.; Fève, G.; Thibierge, E.; Degiovanni, P.

    2017-03-01

    The recent developments of electron quantum optics in quantum Hall edge channels have given us new ways to probe the behavior of electrons in quantum conductors. It has brought new quantities called electronic coherences under the spotlight. In this paper, we explore the relations between electron quantum optics and signal processing through a global review of the various methods for accessing single- and two-electron coherences in electron quantum optics. We interpret electron quantum optics interference experiments as analog signal processing converting quantum signals into experimentally observable quantities such as current averages and correlations. This point of view also gives us a procedure to obtain quantum information quantities from electron quantum optics coherences. We illustrate these ideas by discussing two mode entanglement in electron quantum optics. We also sketch how signal processing ideas may open new perspectives for representing electronic coherences in quantum conductors and understand the properties of the underlying many-body electronic state.

  2. Optical Architectures for Signal Processing - Part A

    DTIC Science & Technology

    2003-04-01

    Input: F; 7 1 Ouput Microwave signal •icrowave signal Optical sourcd Passive optical I Photodetector . device P𔃻 ’ P2 b) Optical source Input: Microwave...integrated illumination with optical power of 2 mW. It can be concluded from Fig. 7 that the same switching performances can be observed whatever the way...1 2 3 4 5 6 7 8 9 10 Frequency (GHz) Figure 7 : Comparison of switching performances under 2mW of optical power for the full integrated structure

  3. SPECIAL ISSUE ON OPTICAL PROCESSING OF INFORMATION: Optical signal-processing systems based on anisotropic media

    NASA Astrophysics Data System (ADS)

    Kiyashko, B. V.

    1995-10-01

    Partially coherent optical systems for signal processing are considered. The transfer functions are formed in these systems by interference of polarised light transmitted by an anisotropic medium. It is shown that such systems can perform various integral transformations of both optical and electric signals, in particular, two-dimensional Fourier and Fresnel transformations, as well as spectral analysis of weak light sources. It is demonstrated that such systems have the highest luminosity and vibration immunity among the systems with interference formation of transfer functions. An experimental investigation is reported of the application of these systems in the processing of signals from a linear hydroacoustic antenna array, and in measurements of the optical spectrum and of the intrinsic noise.

  4. Effect of reference spectra in spectral fitting to discriminate enzyme-activatable photoacoustic probe from intrinsic optical absorbers

    NASA Astrophysics Data System (ADS)

    Hirasawa, Takeshi; Okawa, Shinpei; Iwatate, Ryu J.; Kamiya, Mako; Urano, Yasuteru; Ishihara, Miya

    2016-03-01

    Multispectral photoacoustic (MS-PA) imaging has been researched to image molecular probes in the presence of strong background signals produced from intrinsic optical absorbers. Spectral fitting method (SFM) discriminates probe signals from background signals by fitting the PA spectra that are calculated from MS-PA images to reference spectra of the probe and background, respectively. Because hemoglobin is a dominant optical absorber in visible to near-infrared wavelength range, absorption spectra of hemoglobin have been widely used as reference background spectra. However, the spectra of background signals produced from heterogeneous biological tissue differ from the reference background spectra due to presence of other intrinsic optical absorbers and effect of optical scattering. Due to the difference, the background signals partly remain in the probe images. To image the probe injected in subcutaneous tumors of mice clearly, we added the melanosome absorption spectrum to the reference background spectra because skin contains nonnegligible concentration of melanosome and the spectrum is very similar to the scattering spectrum of biological tissue. The probe injected in the subcutaneous tumor of mice was an enzyme-activatable probe which show their original colors only in the presence of γ-glutamyltranspeptidase, an enzyme associated with cancer. The probes have been successfully used for rapid fluorescence imaging of cancer. As a result of MS-PA imaging, by considering the melanosome absorption spectrum, the background signals were successfully suppressed and then clearer probe image was obtained. Our MS-PA imaging method afforded successful imaging of tumors in mice injected with activatable PA probes.

  5. Quantitative biomarkers of colonic dysplasia based on intrinsic second-harmonic generation signal

    NASA Astrophysics Data System (ADS)

    Zhuo, Shuangmu; Zhu, Xiaoqin; Wu, Guizhu; Chen, Jianxin; Xie, Shusen

    2011-12-01

    Most colorectal cancers arise from dysplastic lesions, such as adenomatous polyps, and these lesions are difficult to be detected by the current endoscopic screening approaches. Here, we present the use of an intrinsic second-harmonic generation (SHG) signal as a novel means to differentiate between normal and dysplastic human colonic tissues. We find that the SHG signal can quantitatively identify collagen change associated with colonic dysplasia that is indiscernible by conventional pathologic techniques. By comparing normal with dysplastic mucosa, there were significant differences in collagen density and collagen fiber direction, providing substantial potential to become quantitative intrinsic biomarkers for in vivo clinical diagnosis of colonic dysplasia.

  6. Optically isolated signal coupler with linear response

    DOEpatents

    Kronberg, James W.

    1994-01-01

    An optocoupler for isolating electrical signals that translates an electrical input signal linearly to an electrical output signal. The optocoupler comprises a light emitter, a light receiver, and a light transmitting medium. The light emitter, preferably a blue, silicon carbide LED, is of the type that provides linear, electro-optical conversion of electrical signals within a narrow wavelength range. Correspondingly, the light receiver, which converts light signals to electrical signals and is preferably a cadmium sulfide photoconductor, is linearly responsive to light signals within substantially the same wavelength range as the blue LED.

  7. Intrinsic Signal Imaging of Deprivation-Induced Contraction of Whisker Representations in Rat Somatosensory Cortex

    PubMed Central

    Drew, Patrick J.

    2009-01-01

    In classical sensory cortical map plasticity, the representation of deprived or underused inputs contracts within cortical sensory maps, whereas spared inputs expand. Expansion of spared inputs occurs preferentially into nearby cortical columns representing temporally correlated spared inputs, suggesting that expansion involves correlation-based learning rules at cross-columnar synapses. It is unknown whether deprived representations contract in a similar anisotropic manner, which would implicate similar learning rules and sites of plasticity. We briefly deprived D-row whiskers in 20-day-old rats, so that each deprived whisker had deprived (D-row) and spared (C- and E-row) neighbors. Intrinsic signal optical imaging revealed that D-row deprivation weakened and contracted the functional representation of deprived D-row whiskers in L2/3 of somatosensory (S1) cortex. Spared whisker representations did not strengthen or expand, indicating that D-row deprivation selectively engages the depression component of map plasticity. Contraction of deprived whisker representations was spatially uniform, with equal withdrawal from spared and deprived neighbors. Single-unit electrophysiological recordings confirmed these results, and showed substantial weakening of responses to deprived whiskers in layer 2/3 of S1, and modest weakening in L4. The observed isotropic contraction of deprived whisker representations during D-row deprivation is consistent with plasticity at intracolumnar, rather than cross-columnar, synapses. PMID:18515797

  8. Time Integrating Optical Signal Processing

    DTIC Science & Technology

    1981-07-01

    diode source modulation, and (b) acousto - lit X)= l,(t)l(t - x / v). ( 2 ) optic deflector modulation for SSS example. F,,r double sideband modulation 1... 2 -1 2.1.2 Acousto - Optic Time-Integrating Correlator . ...... .. 2 -3 2.1.3 Noncoherent Space Integrating Correlator ......... . . 2 -6 2.1.4...device limitation. Acousto - optic devices ] are available with time-bandwidth product much greater than the number of resolvable image samples. 1- 2 I i

  9. A surface intrinsic feature based method (SIFBM) for the characterization of optical microstructure

    NASA Astrophysics Data System (ADS)

    Cheung, C. F.; Kong, L. B.; Lee, W. B.; To, S.

    2008-12-01

    Optical microstructures are small scale topologies which are generally classified as grooves, pyramids, microlens arrays, lenticulations, echells, etc. They are widely used in advanced optics applications. Currently, there is lack of methods for the characterization of surface quality for optical microstructures with sub-micromenter form accuracy and surface finish in the nanometer range. This paper presents a Surface Intrinsic Feature Based Method (SIFBM) which makes use of surface intrinsic properties such as curvatures, normal vectors, torsion, intrinsic frames, etc. They are mapped as special images and image processing techniques are then employed to conduct image registration or correspondences searching by some algorithms such as correlation functions. The surface matching is optimized by corresponding vectors deviations. In the present study, a prototype surface characterization system has been built based on the SIFBM. Primary experimental work has been conducted to validate the proposed method. The results demonstrate that the SIFBM has potential advantages over existing methods.

  10. Blood Contrast Agents Enhance Intrinsic Signals in the Retina: Evidence for an Underlying Blood Volume Component

    PubMed Central

    Ts'o, Daniel

    2011-01-01

    Purpose. To examine the extent to which neurovascular coupling contributes to stimulus-evoked intrinsic signals in the retina. Methods. The retinas of five adult cats were examined in vivo. Animals were anesthetized and paralyzed for imaging stability. The retinas were imaged through a modified fundus camera capable of presenting patterned visual stimuli simultaneous with a diffuse near infrared (NIR). Results. Injections of nigrosin increased signal strength by as much as 36.3%, and indocyanine green (ICG) increased signal magnitudes by as much as 38.1%. In both cases, intrinsic signals maintained a colocalized pattern of activation corresponding to the visual stimulus presented. The time course of the evoked signals remained unaltered. The spectral dependency of signal enhancement mirrored the absorption spectra of the injected dyes. Conclusions. The data are consistent with a neurovascular coupling effect in the retina. Patterned visual stimuli evoke colocalized NIR reflectance changes. The patterned decrease in reflectance was enhanced after nigrosin or ICG was injected into the systemic circulation. These findings suggest stimulus-evoked changes in blood volume underlie a component of the retinal intrinsic signals. PMID:21051719

  11. Enhancement Of Optical Registration Signals Through Digital Signal Processing Techniques

    NASA Astrophysics Data System (ADS)

    Cote, Daniel R.; Lazo-Wasem, Jeanne

    1988-01-01

    Alignment and setup of lighography processes has largely been conducted on special test wafers. Actual product level optimization has been limited to manual techniques such as optical verniers. This is especially time consuming and prone to inconsistencies when the registration characteristics of lithographic systems are being measured. One key factor obstructing the use of automated metrology equipment on product level wafers is the inability to discern reliably, metrology features from the background noise and variations in optical registration signals. This is often the case for metal levels such as aluminum and tungsten. This paper discusses methods for enhancement of typical registration signals obtained from difficult semiconductor process levels. Brightfield and darkfield registration signals are obtained using a microscope and a 1024 element linear photodiode array. These signals are then digitized and stored on the hard disk of a computer. The techniques utilized include amplitude selective and adaptive and non-adaptive frequency domain filtering techniques. The effect of each of these techniques upon calculated registration values is analyzed by determining the positional variation of the center location of a two line registration feature. Plots of raw and processed signals obtained are presented as are plots of the power spectral density of ideal metrology feature signal and noise patterns. It is concluded that the proper application of digital signal processing (DSP) techniques to problematic optical registration signals greatly enhances the applicability of automated optical registration measurement techniques to difficult semiconductor process levels.

  12. New Optical Methods for Signal Processing

    NASA Astrophysics Data System (ADS)

    Zhang, Yan

    This doctoral thesis studies the optical implementations of various new algorithms and methods for large bandwidth signal and image processing. Among the schemes to be studied are the long data stream convolution/correlation, the Gabor and the wavelet transforms, and their applications to system failure prediction, dense target signal processing and image coding. Based on the Chinese remainder theorem, optically implementable algorithms are described, which convert the convolution/correlation of long data streams to relatively small scale linear operations such as a group of short -term vector-matrix multiplications or short-term convolutions/correlations. The proposed algorithms can be realized by using the existing optical analog data processors. Simulations were performed to prove their validity. Technical problems and fundamental limitations of the above schemes are studied. Following the consideration of the above time domain operations, signal's representations in joint time -frequency (scale) domain are then considered. An opto -electronic Gabor coefficient processor is designed to perform the Gabor transform on short one-dimensional (1-D) signals in real-time. Some experimental results are presented to confirm the operational principle of the system. As an application of this processor, Gabor transform based transient signal detection is studied. Other schemes for implementing Gabor transform of long 1-D signals based on the long data stream convolver, and 2-D signals are also investigated. Following the study of the Gabor transform, the newly suggested wavelet transform is considered for its optical implementation. Using commercially available opto-electronic components, an optical wavelet processor is designed and built to perform the wavelet transforms on short 1-D signals in real-time. As an extension, architectures for 2-D optical wavelet transform are also described and computer simulated with the consideration of their technical problems of optical

  13. Cooperative Effects and Intrinsic Optical Bistability in Collections of Atoms

    DTIC Science & Technology

    1989-11-01

    Sov . Phys . JETP 38, 1100 (1974). 17. Il.J. Carmichael and D.F. Walls, J. Phys . B: Atom. Molec. Phys ...268 ( 1985 ). 8. D.A.B. Miller, A.G. Gossard and W. Wiegmann, Optics Lett . 9. 162 (1984). 9. F. Hennenberger and fl. Rossmann, Phys . Stat. Solidi B121...Hollberg, 3. Yurke, J.C. Mertz and J.F. Valey, Phys . Rev. Lett . 55, 2409 ( 1985 ). 28. L.A. Wu, H.J. Kimble, J.L. Hall and H. Wu, Phys . Rev. Lett .

  14. Optical tracking of nerve activity using intrinsic changes in birefringence

    NASA Astrophysics Data System (ADS)

    Badreddine, Ali H.

    Changes in birefringence (or dynamic birefringence) provide an arguably cleaner method of measuring IOS as compared to scattering methods. Other imaging methods have substantial limitations. Nerves inherently exhibit a static (rest condition) birefringence that is associated with the structural anisotropies of axonal protein filaments, membrane phospholipids and proteins, as well as surrounding tissues, which include Schwann cells and axon sheaths. The dynamic birefringence, or "crossed-polarized signal" (XPS), in neurons arises from activity in axons and occurs with a rapid momentary change, typically a decrease, in the birefringence when action potentials (APs) propagate along them. We improved the signal-to-noise to make detecting this signal an easier task, and present the XPS as a viable candidate for detecting AP activity in anisotropic nervous tissue. Our data collectively serves as a strong indication that there is a capacitive-charging-like effect directly inducing a gradual recovery (long tail) of the XPS to baseline, and also causing a smoothing of the XPS trace. A setup was constructed that successfully demonstrated the feasibility of tracking propagating compound APs in a peripheral nerve using the XPS. We made significant progress in the attempt to investigate birefringence of myelination. For the first time, the XPS in a myelinated tissue was detected, and it appears to be bipolar in nature. Further work in investigating the nature of this signal is needed, and is currently underway. Since changes in birefringence in neurons are associated instantaneously with electrophysiological phenomena, they are well-suited for fast imaging of propagating action potentials in neuronal tissue. In summary, imaging based on polarization sensing of changes in birefringence offers promise for an improved noninvasive method of detecting and tracking AP activity in myelinated and unmyelinated nerves and could be designed for pre-clinical and surgical applications.

  15. Radio Science from an Optical Communications Signal

    NASA Technical Reports Server (NTRS)

    Moision, Bruce; Asmar, Sami; Oudrhiri, Kamal

    2013-01-01

    NASA is currently developing the capability to deploy deep space optical communications links. This creates the opportunity to utilize the optical link to obtain range, doppler, and signal intensity estimates. These may, in turn, be used to complement or extend the capabilities of current radio science. In this paper we illustrate the achievable precision in estimating range, doppler, and received signal intensity of an non-coherent optical link (the current state-of-the-art for a deep-space link). We provide a joint estimation algorithm with performance close to the bound. We draw comparisons to estimates based on a coherent radio frequency signal, illustrating that large gains in either precision or observation time are possible with an optical link.

  16. Radio Science from an Optical Communications Signal

    NASA Technical Reports Server (NTRS)

    Moision, Bruce; Asmar, Sami; Oudrhiri, Kamal

    2013-01-01

    NASA is currently developing the capability to deploy deep space optical communications links. This creates the opportunity to utilize the optical link to obtain range, doppler, and signal intensity estimates. These may, in turn, be used to complement or extend the capabilities of current radio science. In this paper we illustrate the achievable precision in estimating range, doppler, and received signal intensity of an non-coherent optical link (the current state-of-the-art for a deep-space link). We provide a joint estimation algorithm with performance close to the bound. We draw comparisons to estimates based on a coherent radio frequency signal, illustrating that large gains in either precision or observation time are possible with an optical link.

  17. Optical Wavelet Signals Processing and Multiplexing

    NASA Astrophysics Data System (ADS)

    Cincotti, Gabriella; Moreolo, Michela Svaluto; Neri, Alessandro

    2005-12-01

    We present compact integrable architectures to perform the discrete wavelet transform (DWT) and the wavelet packet (WP) decomposition of an optical digital signal, and we show that the combined use of planar lightwave circuits (PLC) technology and multiresolution analysis (MRA) can add flexibility to current multiple access optical networks. We furnish the design guidelines to synthesize wavelet filters as two-port lattice-form planar devices, and we give some examples of optical signal denoising and compression/decompression techniques in the wavelet domain. Finally, we present a fully optical wavelet packet division multiplexing (WPDM) scheme where data signals are waveform-coded onto wavelet atom functions for transmission, and numerically evaluate its performances.

  18. Optical extinction due to intrinsic structural variations of photonic crystals

    NASA Astrophysics Data System (ADS)

    Koenderink, A. Femius; Lagendijk, Ad; Vos, Willem L.

    2005-10-01

    Unavoidable variations in size and position of the building blocks of photonic crystals cause light scattering and extinction of coherent beams. We present a model for both two- and three-dimensional photonic crystals that relates the extinction length to the magnitude of the variations. The predicted lengths agree well with our experiments on high-quality opals and inverse opals, and with literature data analyzed by us. As a result, control over photons is limited to distances up to 50 lattice parameters (˜15 μm) in state-of-the-art structures, thereby impeding applications that require large photonic crystals, such as proposed optical integrated circuits. Conversely, scattering in photonic crystals may lead to different physics such as Anderson localization and nonclassical diffusion.

  19. Optical Profilometers Using Adaptive Signal Processing

    NASA Technical Reports Server (NTRS)

    Hall, Gregory A.; Youngquist, Robert; Mikhael, Wasfy

    2006-01-01

    A method of adaptive signal processing has been proposed as the basis of a new generation of interferometric optical profilometers for measuring surfaces. The proposed profilometers would be portable, hand-held units. Sizes could be thus reduced because the adaptive-signal-processing method would make it possible to substitute lower-power coherent light sources (e.g., laser diodes) for white light sources and would eliminate the need for most of the optical components of current white-light profilometers. The adaptive-signal-processing method would make it possible to attain scanning ranges of the order of decimeters in the proposed profilometers.

  20. Optical signal processing for wireless transmission

    NASA Astrophysics Data System (ADS)

    Kawanishi, Tetsuya

    2012-01-01

    Millimeter-wave bands are attracting attention because of the availability of wideband for high-speed transmission. However, due to the limitation of the performance of electric signal processing, it is rather difficult to modulate and demodulate millimeter-wave signals with high-speed baseband modulation. In this paper, we describe optical signal processing for high-speed modulation of millimeter-wave, based on high-speed and precise lightwave control. In optical fiber communication systems, various types of modulation formats, such as quadrature-amplitude-modulation, are reported to achieve high-speed transmission. Optical two-tone signals can be converted into millimeter-wave signals by using high-speed photodetectors. This technique can be used for distribution of stable reference signals in large-scale antenna arrays for radio astronomy. By using the millimeter-wave signal generation technique and the optical advanced modulation formats, we can achieve high-speed modulation of millimeter-waves, where the carrier frequency and bit rate can be over 90GHz and 40Gb/s, respectively.

  1. Optical Signal Processing for Surveillance.

    DTIC Science & Technology

    1984-04-25

    unsuitable _ for interferolltric uses. (9) mDNOLITIC DIODE LASER ARRAYS.5 6, 7 The advantages are: (i) each element of the array has high output power (> bdd ...MODULATOR 10,11 The optical arrangement of the multichannel light modulator is shown in Figure 6. The various channels correspond to the electrode finger...applied to the electrodes ). The disadvantages are: (i) low light diffraction efficiency (ii) a cross-talk of about -20dB between adjacent channels, and

  2. Vesicular Glutamate Transporter 1 Is Required for Photoreceptor Synaptic Signaling But Not For Intrinsic Visual Functions

    PubMed Central

    Johnson, Juliette; Fremeau, Robert T.; Duncan, Jacque L.; Rentería, René C.; Yang, Haidong; Hua, Zhaolin; Liu, Xiaorong; LaVail, Matthew M.; Edwards, Robert H.; Copenhagen, David R.

    2008-01-01

    Glutamatergic neurotransmission requires vesicular glutamate transporters (VGLUTs) to sequester glutamate into synaptic vesicles. Generally, VGLUT1 and VGLUT2 isoforms show complementary expression in the CNS and retina. However, little is known about whether isoform-specific expression serves distinct pathways and physiological functions. Here, by examining visual functions in VGLUT1-null mice, we demonstrate that visual signaling from photoreceptors to retinal output neurons requires VGLUT1. However, photoentrainment and pupillary light responses are preserved. We provide evidence that melanopsin-containing, intrinsically photosensitive retinal ganglion cells (RGCs), signaling via VGLUT2 pathways, support these non-image-forming functions. We conclude that VGLUT1 is essential for transmitting visual signals from photoreceptors to second- and third-order neurons, but VGLUT1 is not necessary for intrinsic visual functions. Furthermore, melanopsin and VGLUT2 expression in a subset of RGCs immediately after birth strongly supports the idea that intrinsic vision can function well before rod- and cone-mediated signaling has matured. PMID:17611277

  3. The role of intrinsic apoptotic signaling in hemorrhagic shock-induced microvascular endothelial cell barrier dysfunction.

    PubMed

    Sawant, Devendra A; Tharakan, Binu; Hunter, Felicia A; Childs, Ed W

    2014-11-01

    Hemorrhagic shock leads to endothelial cell barrier dysfunction resulting in microvascular hyperpermeability. Hemorrhagic shock-induced microvascular hyperpermeability is associated with worse clinical outcomes in patients with traumatic injuries. The results from our laboratory have illustrated a possible pathophysiological mechanism showing involvement of mitochondria-mediated "intrinsic" apoptotic signaling in regulating hemorrhagic shock-induced microvascular hyperpermeability. Hemorrhagic shock results in overexpression of Bcl-2 family of pro-apoptotic protein, BAK, in the microvascular endothelial cells. The increase in BAK initiates "intrinsic" apoptotic signaling cascade with the release of mitochondrial cytochrome c in the cytoplasm and activation of downstream effector caspase-3, leading to loss of endothelial cell barrier integrity. Thus, this review article offers a brief overview of important findings from our past and present research work along with new leads for future research. The summary of our research work will provide information leading to different avenues in developing novel strategies against microvascular hyperpermeability following hemorrhagic shock.

  4. Intrinsic signal imaging of brain function using a small implantable CMOS imaging device

    NASA Astrophysics Data System (ADS)

    Haruta, Makito; Sunaga, Yoshinori; Yamaguchi, Takahiro; Takehara, Hironari; Noda, Toshihiko; Sasagawa, Kiyotaka; Tokuda, Takashi; Ohta, Jun

    2015-04-01

    A brain functional imaging technique over a long period is important to understand brain functions related to animal behavior. We have developed a small implantable CMOS imaging device for measuring brain activity in freely moving animals. This device is composed of a CMOS image sensor chip and LEDs for illumination. In this study, we demonstrated intrinsic signal imaging of blood flow using the device with a green LED light source at a peak wavelength of 535 nm, which corresponds to one of the absorption spectral peaks of blood cells. Brain activity increases regional blood flow. The device light weight of about 0.02 g makes it possible to stably measure brain activity through blood flow over a long period. The device has successfully measured the intrinsic signal related to sensory stimulation on the primary somatosensory cortex.

  5. Modulation and detection of optical signals

    NASA Technical Reports Server (NTRS)

    Goodwin, F. E.

    1972-01-01

    A summary of information is presented which is related to the modulation and detection of information on optical carriers. It emphasizes the treatment of information transfer through an entire system. The most common configurations are considered: intensity modulation, amplitude modulation, frequency or phase modulation, and both direct and coherent detection. In assessing these configurations information capacity and message signal-to-noise ratio are used as a basis of comparison. The physical and geometric treatment of optical heterodyne (or coherent) detection is given.

  6. Which is the best intrinsic motivation signal for learning multiple skills?

    PubMed Central

    Santucci, Vieri G.; Baldassarre, Gianluca; Mirolli, Marco

    2013-01-01

    Humans and other biological agents are able to autonomously learn and cache different skills in the absence of any biological pressure or any assigned task. In this respect, Intrinsic Motivations (i.e., motivations not connected to reward-related stimuli) play a cardinal role in animal learning, and can be considered as a fundamental tool for developing more autonomous and more adaptive artificial agents. In this work, we provide an exhaustive analysis of a scarcely investigated problem: which kind of IM reinforcement signal is the most suitable for driving the acquisition of multiple skills in the shortest time? To this purpose we implemented an artificial agent with a hierarchical architecture that allows to learn and cache different skills. We tested the system in a setup with continuous states and actions, in particular, with a kinematic robotic arm that has to learn different reaching tasks. We compare the results of different versions of the system driven by several different intrinsic motivation signals. The results show (a) that intrinsic reinforcements purely based on the knowledge of the system are not appropriate to guide the acquisition of multiple skills, and (b) that the stronger the link between the IM signal and the competence of the system, the better the performance. PMID:24273511

  7. Optical Fiber Delay Line Signal Processing.

    NASA Astrophysics Data System (ADS)

    Newton, Steven Arthur

    The delay line transversal filter is a basic component in analog signal processing systems. Unfortunately, conventional delay line devices, such as those that use surface acoustic waves, are largely limited to operation at frequencies of several hundred megahertz and below. In this work, single-mode optical fiber has been used as a delay medium to make transversal filters that extend this kind of signal processing to frequencies of one gigahertz and above. Single-mode optical fiber is an excellent delay medium because it exhibits extremely low loss and dispersion. By efficiently collecting, weighting, and combining signals extracted from a fiber delay line, single-mode fiber can be used, not only to transmit broadband signals, but to process them as well. The goals of the work have been to study efficient tapping mechanisms, and to construct fiber transversal filters capable of performing some basic signal processing functions. Several different tapped and recirculating delay line prototypes have been fabricated using a variety of tapping techniques, including macrobending and evanescent field coupling. These devices have been used to demonstrate basic signal processing functions, such as code generation, convolution, correlation, and frequency filtering, at frequencies that exceed those possible using conventional delay line technologies. Fiber recirculating delay line loops have also been demonstrated as transient memories for the temporary storage of signals and as a means of time division multiplexing via data rate transformation. These devices are the building blocks that are necessary to make systems capable of performing complex signal processing functions. With the recent development of high speed optical sources and detectors to interface with fiber systems of this kind, the real time processing of signals having bandwidths of tens of gigahertz is envisioned.

  8. Optical signal processing of phased array radar

    NASA Astrophysics Data System (ADS)

    Weverka, Robert T.

    This thesis develops optical processors that scale to very high processing speed. Optical signal processing is often promoted on the basis of smaller size, lower weight and lower power consumption as well as higher signal processing speed. While each of these requirements has applications, it is the ones that require processing speed beyond that available in electronics that are most compelling. Thirty years ago, optical processing was the only method fast enough to process Synthetic Aperture Radar (SAR), one of the more demanding signal processing tasks at this time. Since that time electronic processing speed has improved sufficiently to tackle that problem. We have sought out the problems that require significantly higher processing speed and developed optical processors that tackle these more difficult problems. The components that contribute to high signal processing speed are high input signal bandwidth, a large number of parallel input channels each with this high bandwidth, and a large number of parallel operations required on each input channel. Adaptive signal processing for phased array radar has all of these factors. The processors developed for this task scale well in three dimensions, which allows them to maximize parallelism for high speed. This thesis explores an example of a negative feedback adaptive phased array processor and an example of a positive feedback phased array processor. The negative feedback processor uses and array of inputs in up to two dimensions together with the time history of the signal in the third dimension to adapt the array pattern to null out incoming jammer signals. The positive feedback processor uses the incoming signals and assumptions about the radar scene to correct for position errors in a phased array. Discovery and analysis of these new processors are facilitated by an original volume holographic analysis technique developed in the thesis. The thesis includes a new acoustooptic Bragg cell geometry developed with

  9. Integrated optical signal processing with magnetostatic waves

    NASA Technical Reports Server (NTRS)

    Fisher, A. D.; Lee, J. N.

    1984-01-01

    Magneto-optical devices based on Bragg diffraction of light by magnetostatic waves (MSW's) offer the potential of large time-bandwidth optical signal processing at microwave frequencies of 1 to 20 GHz and higher. A thin-film integrated-optical configuration, with the interacting MSW and guided-optical wave both propagating in a common ferrite layer, is necessary to avoid shape-factor demagnetization effects. The underlying theory of the MSW-optical interaction is outlined, including the development of expressions for optical diffraction efficiency as a function of MSW power and other relevant parameters. Bradd diffraction of guided-optical waves by transversely-propagating magnetostatic waves and collinear TE/TM mode conversion included by MSW's have been demonstrated in yttrium iron garnet (YIG) thin films. Diffraction levels as large as 4% (7 mm interaction length) and a modulation dynamic range of approx 30 dB have been observed. Advantages of these MSW-based devices over the analogous acousto-optical devices include: much greater operating frequencies, tunability of the MSW dispersion relation by varying either the RF frequency or the applied bias magnetic field, simple broad-band MSW transducer structures (e.g., a single stripline), and the potential for very high diffraction efficiencies.

  10. [Determination of intrinsic alliin dissolution rates with fiber-optic sensing process analysis].

    PubMed

    Geng, Jing; Zhang, Zi-Cheng; Zhang, Hai-Bo; Li, Xin-Xia; Chen, Jian

    2014-10-01

    The apparatus for intrinsic dissolution test recorded in United States Pharmacopeia (USP) integrating with fiber-optic drug dissolution test system (FODT) were used to real-time monitor intrinsic dissolution processes of alliin in four media which were water, solution of HCl with pH 1.2, buffer solution of acetate with pH 4.5, and buffer solution of phosphate with pH 6.8. The intrinsic dissolution rate (IDR) and the similarity factor (f2) of two intrinsic dissolution curves with two apparatuses were calculated. The IDR values of alliin with rotating disk system were 28.1.3, 33.55, 28.38 and 30.95 mg x cm(-2) x min(-1) in four media, respectively. And the IDR values of alliin with stationary disk system were 44.16, 47.07, 45.11 and 51.34 mg x cm(-2) x min(-1), respectively. The similarity factors were 56.42, 50.75, 40.30 and 40.64, respectively. The results showed that the intrinsic alliin dissolution rates were much greater than 1 mg x cm(-2) x min(-1). It inferred that alliin dissolution would not be the rate limiting step to absorption.

  11. Passive intrinsic-linewidth narrowing of ultraviolet extended-cavity diode laser by weak optical feedback.

    PubMed

    Samutpraphoot, Polnop; Weber, Sophie; Lin, Qian; Gangloff, Dorian; Bylinskii, Alexei; Braverman, Boris; Kawasaki, Akio; Raab, Christoph; Kaenders, Wilhelm; Vuletić, Vladan

    2014-05-19

    We present a simple method for narrowing the intrinsic Lorentzian linewidth of a commercial ultraviolet grating extended-cavity diode laser (TOPTICA DL Pro) using weak optical feedback from a long external cavity. We achieve a suppression in frequency noise spectral density of 20 dB measured at frequencies around 1 MHz, corresponding to the narrowing of the intrinsic Lorentzian linewidth from 200 kHz to 2 kHz. Provided additional active low-frequency noise suppression and long-term drift compensation, the system is suitable for experiments requiring a tunable ultraviolet laser with narrow linewidth and low high-frequency noise, such as precision spectroscopy, optical clocks, and quantum information science experiments.

  12. Guanine nucleotide exchange factor RABGEF1 regulates keratinocyte-intrinsic signaling to maintain skin homeostasis

    PubMed Central

    Marichal, Thomas; El Abbas, Sophie; Sibilano, Riccardo; Zurek, Oliwia; Reber, Laurent L.; Pirottin, Dimitri; Kim, Jinah; Chambon, Pierre; Roers, Axel; Antoine, Nadine; Kawakami, Yuko; Bureau, Fabrice; Tam, See-Ying; Tsai, Mindy

    2016-01-01

    Epidermal keratinocytes form a structural and immune barrier that is essential for skin homeostasis. However, the mechanisms that regulate epidermal barrier function are incompletely understood. Here we have found that keratinocyte-specific deletion of the gene encoding RAB guanine nucleotide exchange factor 1 (RABGEF1, also known as RABEX-5) severely impairs epidermal barrier function in mice and induces an allergic cutaneous and systemic phenotype. RABGEF1-deficient keratinocytes exhibited aberrant activation of the intrinsic IL-1R/MYD88/NF-κB signaling pathway and MYD88-dependent abnormalities in expression of structural proteins that contribute to skin barrier function. Moreover, ablation of MYD88 signaling in RABGEF1-deficient keratinocytes or deletion of Il1r1 restored skin homeostasis and prevented development of skin inflammation. We further demonstrated that epidermal RABGEF1 expression is reduced in skin lesions of humans diagnosed with either atopic dermatitis or allergic contact dermatitis as well as in an inducible mouse model of allergic dermatitis. Our findings reveal a key role for RABGEF1 in dampening keratinocyte-intrinsic MYD88 signaling and sustaining epidermal barrier function in mice, and suggest that dysregulation of RABGEF1 expression may contribute to epidermal barrier dysfunction in allergic skin disorders in mice and humans. Thus, RABGEF1-mediated regulation of IL-1R/MYD88 signaling might represent a potential therapeutic target. PMID:27820702

  13. Intrinsic Disorder in Transmembrane Proteins: Roles in Signaling and Topology Prediction

    PubMed Central

    Bürgi, Jérôme; Xue, Bin; Uversky, Vladimir N.

    2016-01-01

    Intrinsically disordered regions (IDRs) are peculiar stretches of amino acids that lack stable conformations in solution. Intrinsic Disorder containing Proteins (IDP) are defined by the presence of at least one large IDR and have been linked to multiple cellular processes including cell signaling, DNA binding and cancer. Here we used computational analyses and publicly available databases to deepen insight into the prevalence and function of IDRs specifically in transmembrane proteins, which are somewhat neglected in most studies. We found that 50% of transmembrane proteins have at least one IDR of 30 amino acids or more. Interestingly, these domains preferentially localize to the cytoplasmic side especially of multi-pass transmembrane proteins, suggesting that disorder prediction could increase the confidence of topology prediction algorithms. This was supported by the successful prediction of the topology of the uncharacterized multi-pass transmembrane protein TMEM117, as confirmed experimentally. Pathway analysis indicated that IDPs are enriched in cell projection and axons and appear to play an important role in cell adhesion, signaling and ion binding. In addition, we found that IDP are enriched in phosphorylation sites, a crucial post translational modification in signal transduction, when compared to fully ordered proteins and to be implicated in more protein-protein interaction events. Accordingly, IDPs were highly enriched in short protein binding regions called Molecular Recognition Features (MoRFs). Altogether our analyses strongly support the notion that the transmembrane IDPs act as hubs in cellular signal events. PMID:27391701

  14. Intrinsic Disorder in Transmembrane Proteins: Roles in Signaling and Topology Prediction.

    PubMed

    Bürgi, Jérôme; Xue, Bin; Uversky, Vladimir N; van der Goot, F Gisou

    2016-01-01

    Intrinsically disordered regions (IDRs) are peculiar stretches of amino acids that lack stable conformations in solution. Intrinsic Disorder containing Proteins (IDP) are defined by the presence of at least one large IDR and have been linked to multiple cellular processes including cell signaling, DNA binding and cancer. Here we used computational analyses and publicly available databases to deepen insight into the prevalence and function of IDRs specifically in transmembrane proteins, which are somewhat neglected in most studies. We found that 50% of transmembrane proteins have at least one IDR of 30 amino acids or more. Interestingly, these domains preferentially localize to the cytoplasmic side especially of multi-pass transmembrane proteins, suggesting that disorder prediction could increase the confidence of topology prediction algorithms. This was supported by the successful prediction of the topology of the uncharacterized multi-pass transmembrane protein TMEM117, as confirmed experimentally. Pathway analysis indicated that IDPs are enriched in cell projection and axons and appear to play an important role in cell adhesion, signaling and ion binding. In addition, we found that IDP are enriched in phosphorylation sites, a crucial post translational modification in signal transduction, when compared to fully ordered proteins and to be implicated in more protein-protein interaction events. Accordingly, IDPs were highly enriched in short protein binding regions called Molecular Recognition Features (MoRFs). Altogether our analyses strongly support the notion that the transmembrane IDPs act as hubs in cellular signal events.

  15. Fiber optic intrinsic Fabry-Perot temperature sensor fabricated by femtosecond lasers

    NASA Astrophysics Data System (ADS)

    Wang, Wenyuan; Pang, Fufei; Chen, Na; Zhang, Xiaobei; Lan, Lugang; Ding, Ding; Wang, Tingyun

    2010-12-01

    A fiber-optic intrinsic Fabry-Perot (F-P) interferometric sensor was inscribed in a standard single mode fiber by inducing refractive index change in the core. It was written directly by using a femtosecond laser. The reflection spectrum of the fiber-optic F-P interferometric sensor was measured and was investigated as a temperature sensor. The sensitivity of the sensor is 9.2 pm/°C in the temperature range of -20~80°C.

  16. Intraoperative intrinsic optical imaging of human somatosensory cortex during neurosurgical operations.

    PubMed

    Sato, Katsushige; Nariai, Tadashi; Momose-Sato, Yoko; Kamino, Kohtaro

    2017-07-01

    Intrinsic optical imaging as developed by Grinvald et al. is a powerful technique for monitoring neural function in the in vivo central nervous system. The advent of this dye-free imaging has also enabled us to monitor human brain function during neurosurgical operations. We briefly describe our own experience in functional mapping of the human somatosensory cortex, carried out using intraoperative optical imaging. The maps obtained demonstrate new additional evidence of a hierarchy for sensory response patterns in the human primary somatosensory cortex.

  17. Polymer optical fiber Bragg grating acting as an intrinsic biochemical concentration sensor.

    PubMed

    Zhang, Wei; Webb, David; Peng, Gangding

    2012-04-15

    We demonstrate an intrinsic biochemical concentration sensor based on a polymer optical fiber Bragg grating. The water content absorbed by the polymer fiber from a surrounding solution depends on the concentration of the solution because of the osmotic effect. The variation of water content in the fiber causes a change in the fiber dimensions and a variation in refractive index and, therefore, a shift in the Bragg wavelength. Saline solutions with concentration from 0% to 22% were used to demonstrate the sensing principle, resulting in a total wavelength shift of 0.9 nm, allowing high-resolution concentration measurements to be realized. © 2012 Optical Society of America

  18. Effects of pre-strain on the intrinsic pressure sensitivity of polymer optical fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Pedersen, Jens Kristian Mølgaard; Woyessa, Getinet; Nielsen, Kristian; Bang, Ole

    2017-04-01

    We experimentally demonstrate a scheme for improving the intrinsic pressure sensitivity of fiber Bragg-gratings (FBGs) inscribed in polymer optical fibers by applying pre-strain in order to suppress the pressure induced mechanical contraction of the fiber. This contraction would otherwise contribute to a blueshift of the Brag-wavelength, counteracting the dominant redshift caused by the stress-optic effect, which effectively reduces the pressure sensitivity of the FBG. By applying this technique we are able to improve the sensitivity of the FBG from 2.8 pm/bar to 7.3 pm/bar.

  19. Intrinsic parameterization of a computational optical system for long-distance displacement structural monitoring

    NASA Astrophysics Data System (ADS)

    Martins, Luís F. Lages; Rebordão, José Manuel N. V.; Ribeiro, Álvaro Silva

    2015-01-01

    We aim at the intrinsic parameterization of a computational optical system applied in long-distance displacement measurement of large-scale structures. In this structural-monitoring scenario, the observation distance established between the digital camera and reference targets, which is composed of the computational optical system, can range from 100 up to 1000 m, requiring the use of long-focal length lenses in order to obtain a suitable sensitivity for the three-dimensional displacement measurement of the observed structure which can be of reduced magnitude. Intrinsic parameterization of long-focal length cameras is an emergent issue since conventional approaches applied for reduced focal length cameras are not suitable mainly due to ill-conditioned matrices in least squares estimation procedures. We describe the intrinsic parameterization of a long-focal length camera (600 mm) by the diffractive optical element method and present the obtained estimates and measurement uncertainties, discussing their contribution for the system's validation by calibration field test and displacement measurement campaigns in a long-span suspension bridge.

  20. Intrinsic temperature-dependent evolutions in the electron-boson spectral density obtained from optical data.

    PubMed

    Hwang, Jungseek

    2016-03-31

    We investigate temperature smearing effects on the electron-boson spectral density function (I(2)χ(ω)) obtained from optical data using a maximum entropy inversion method. We start with two simple model input I(2)χ(ω), calculate the optical scattering rates at selected temperatures using the model input spectral density functions and a generalized Allen's formula, then extract back I(2)χ(ω) at each temperature from the calculated optical scattering rate using the maximum entropy method (MEM) which has been used for analysis of optical data of high-temperature superconductors including cuprates, and finally compare the resulting I(2)χ(ω) with the input ones. From this approach we find that the inversion process can recover the input I(2)χ(ω) almost perfectly when the quality of fits is good enough and also temperature smearing (or thermal broadening) effects appear in the I(2)χ(ω) when the quality of fits is not good enough. We found that the coupling constant and the logarithmically averaged frequency are robust to the temperature smearing effects and/or the quality of fits. We use these robust properties of the two quantities as criterions to check whether experimental data have intrinsic temperature-dependent evolutions or not. We carefully apply the MEM to two material systems (one optimally doped and the other underdoped cuprates) and conclude that the I(2)χ(ω) extracted from the optical data contain intrinsic temperature-dependent evolutions.

  1. Epileptic seizure classification in EEG signals using second-order difference plot of intrinsic mode functions.

    PubMed

    Pachori, Ram Bilas; Patidar, Shivnarayan

    2014-02-01

    Epilepsy is a neurological disorder which is characterized by transient and unexpected electrical disturbance of the brain. The electroencephalogram (EEG) is a commonly used signal for detection of epileptic seizures. This paper presents a new method for classification of ictal and seizure-free EEG signals. The proposed method is based on the empirical mode decomposition (EMD) and the second-order difference plot (SODP). The EMD method decomposes an EEG signal into a set of symmetric and band-limited signals termed as intrinsic mode functions (IMFs). The SODP of IMFs provides elliptical structure. The 95% confidence ellipse area measured from the SODP of IMFs has been used as a feature in order to discriminate seizure-free EEG signals from the epileptic seizure EEG signals. The feature space obtained from the ellipse area parameters of two IMFs has been used for classification of ictal and seizure-free EEG signals using the artificial neural network (ANN) classifier. It has been shown that the feature space formed using ellipse area parameters of first and second IMFs has given good classification performance. Experimental results on EEG database available by the University of Bonn, Germany, are included to illustrate the effectiveness of the proposed method. Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.

  2. Chromosome- and spindle-pole-derived signals generate an intrinsic code for spindle position and orientation.

    PubMed

    Kiyomitsu, Tomomi; Cheeseman, Iain M

    2012-02-12

    Mitotic spindle positioning by cortical pulling forces defines the cell division axis and location, which is critical for proper cell division and development. Although recent work has identified developmental and extrinsic cues that regulate spindle orientation, the contribution of intrinsic signals to spindle positioning and orientation remains unclear. Here, we demonstrate that cortical force generation in human cells is controlled by distinct spindle-pole- and chromosome-derived signals that regulate cytoplasmic dynein localization. First, dynein exhibits a dynamic asymmetric cortical localization that is negatively regulated by spindle-pole proximity, resulting in spindle oscillations to centre the spindle within the cell. We find that this signal comprises the spindle-pole-localized polo-like kinase (Plk1), which regulates dynein localization by controlling the interaction between dynein-dynactin and its upstream cortical targeting factors NuMA and LGN. Second, a chromosome-derived RanGTP gradient restricts the localization of NuMA-LGN to the lateral cell cortex to define and maintain the spindle orientation axis. RanGTP acts in part through the nuclear localization sequence of NuMA to locally alter the ability of NuMA-LGN to associate with the cell cortex in the vicinity of chromosomes. We propose that these chromosome- and spindle-pole-derived gradients generate an intrinsic code to control spindle position and orientation.

  3. Signal transduction pathways, intrinsic regulators, and the control of cell fate choice

    PubMed Central

    Fossett, Nancy

    2012-01-01

    Background Information regarding changes in organismal status is transmitted to the stem cell regulatory machinery by a limited number of signal transduction pathways. Consequently, these pathways derive their functional specificity through interactions with stem cell intrinsic master regulators, notably transcription factors. Identifying the molecular underpinnings of these interactions is critical to understanding stem cell function. Scope of review This review focuses on studies in Drosophila that identify the gene regulatory basis for interactions between three different signal transduction pathways and an intrinsic master transcriptional regulator in the context of hematopoietic stem-like cell fate choice. Specifically, the interface between the GATA:FOG regulatory complex and the JAK/STAT, BMP, and Hedgehog pathways is examined. Major conclusions The GATA:FOG complex coordinates information transmitted by at least three different signal transduction pathways as a means to control stem-like cell fate choice. This illustrates emerging principles concerning regulation of stem cell function and describes a gene regulatory link between changes in organismal status and stem cell response. General significance The Drosophila model system offers a powerful approach to identify the molecular basis of how stem cells receive, interpret, and then respond to changes in organismal status. PMID:22705942

  4. A VHDL Core for Intrinsic Evolution of Discrete Time Filters with Signal Feedback

    NASA Technical Reports Server (NTRS)

    Gwaltney, David A.; Dutton, Kenneth

    2005-01-01

    The design of an Evolvable Machine VHDL Core is presented, representing a discrete-time processing structure capable of supporting control system applications. This VHDL Core is implemented in an FPGA and is interfaced with an evolutionary algorithm implemented in firmware on a Digital Signal Processor (DSP) to create an evolvable system platform. The salient features of this architecture are presented. The capability to implement IIR filter structures is presented along with the results of the intrinsic evolution of a filter. The robustness of the evolved filter design is tested and its unique characteristics are described.

  5. Fiber optics transmission of LV signal

    NASA Technical Reports Server (NTRS)

    Young, A. D.; Gunter, W. D., Jr.

    1981-01-01

    The first use of a long optical fiber for transmitting megahertz frequencies in a laser velocimeter (LV) receiver system is reported. The fiber comprises a 600-micron diameter fused silica core, a silicon polymer cladding and a plastic jacket. The fiber numerical aperture is 0.22, corresponding to a maximum entrance half-angle of 0.22 rad. The 10-m length used results in a 5.6% attenuation loss. The fiber is found to transmit an 80-MHz signal with excellent resolution. It is established that an LV receiver using fiber optics sends a clean signal in electronically noisy and high-pressure environments and allows velocity measurements in places too small for a photomultiplier tube.

  6. Efficient optical communications using multibit differential signaling

    NASA Astrophysics Data System (ADS)

    Chiarulli, Donald M.; Levitan, Steven P.; Dickerson, Samuel J.; Bakos, Jason D.; Martin, Joel

    2006-02-01

    We present an alternative signaling method for multi-channel fiber ribbon based optical links. The method is based on a hybrid of differential signaling and single-ended channels. Channels are grouped into code blocks of n-bits. Each code word transmitted in the block is restricted to conform to an n choose m rule. Electrical drivers steer current between m active VCSELS with no dummy loads. A virtual reference is synthesized from the received signals and used for differential discrimination. This signaling method approaches the signal-to-noise characteristics of fully differential signaling but can be implemented with significantly lower channel overhead, giving as much as a 33% reduction in fiber count and a 44% reduction in power. Further, code utilization rates on these links can be as low as 51%, leaving substantial code space available for ECC or channel management functions. In this paper, we describe the signaling method and present a prototype transceiver chip. The transceiver is implemented in 0.25um UTSi Silicon-on-Sapphire technology with flip-chip bonded VCSEL and photodetector arrays. The design demonstrates a pin-compatible alternative to the POP4-MSA transceiver standard with 125% greater data throughput and 25% better power efficiency.

  7. Nonlinear Real-Time Optical Signal Processing.

    DTIC Science & Technology

    1984-10-01

    DTIC ELECTE I B IIMAGE PROCESSING INSTITUTE 84 11 26 107 UNCLASSIFIED SECURITY CLASSIFICATION OF THIS PAGE (When Dota Entered), REPORT DOCUMENTATION...30, 1984 N NONLINEAR REAL-TIME OPTICAL SIGNAL PROCESSING i E~ A.A. Sawchuk, Principal Investigator T.C. Strand and A.R. Tanguay. Jr. October 1, 1984...RDepartment of Electrical Engineering Image Processing institute University of Southern California University Park-MC 0272 Los Angeles, California

  8. Development and study the performance of PBA cladding modified fiber optic intrinsic biosensor for urea detection

    NASA Astrophysics Data System (ADS)

    Botewad, S. N.; Pahurkar, V. G.; Muley, G. G.

    2016-05-01

    The fabrication and study of a cladding modified fiber optic intrinsic urea biosensor based on evanescent wave absorbance has been presented. The sensor was prepared using cladding modification technique by removing a small portion of cladding of an optical fiber and modifying with an active cladding of porous polyaniline-boric acid (PBA) matrix to immobilize enzyme-urease through cross-linking via glutaraldehyde. The nature of as-synthesized and deposited PBA film on fiber optic sensing element was studied by ultraviolet-visible (UV-vis) spectroscopy and X-ray diffraction (XRD) analysis. The performance of the developed sensor was studied for different urea concentrations in solutions prepared in phosphate buffer.

  9. Development and study the performance of PBA cladding modified fiber optic intrinsic biosensor for urea detection

    SciTech Connect

    Botewad, S. N.; Pahurkar, V. G.; Muley, G. G.

    2016-05-06

    The fabrication and study of a cladding modified fiber optic intrinsic urea biosensor based on evanescent wave absorbance has been presented. The sensor was prepared using cladding modification technique by removing a small portion of cladding of an optical fiber and modifying with an active cladding of porous polyaniline-boric acid (PBA) matrix to immobilize enzyme-urease through cross-linking via glutaraldehyde. The nature of as-synthesized and deposited PBA film on fiber optic sensing element was studied by ultraviolet-visible (UV-vis) spectroscopy and X-ray diffraction (XRD) analysis. The performance of the developed sensor was studied for different urea concentrations in solutions prepared in phosphate buffer.

  10. Fabrication of polyaniline-HCl cladding modified fiber optic intrinsic biosensor for glucose detection

    NASA Astrophysics Data System (ADS)

    Pahurkar, Vikas; Tamgadge, Yuoraj; Muley, Gajanan

    2016-05-01

    In the present study, we have fabricated and studied response of cladding modified fiber optic intrinsic glucose biosensor (FOIGB). The optical fiber was used as a light transforming waveguide and sensing element fabricated over it by applying a thin layer of polymer. The cladding of the sensor was modified with the polyaniline-hydrochloric acid (PANI-HCl) polymer matrix. The PANI-HCl matrix provides an amorphous morphology useful to immobilize glucose oxidase (GOx) biomolecules through cross-linking technique via glutaraldehyde. The present sensor was used to detect the glucose analyte in the solution. In the sensing response study of FOIGB toward glucose, novel modal power distribution (MPD) technique was used. The reaction between GOx and glucose changes the optical properties of prepared FOIGB and hence modify MPD at output as a function of glucose concentration. The nature and surface morphology of PANI-HCl matrix has been studied.

  11. Application of intrinsic time-scale decomposition (ITD) to EEG signals for automated seizure prediction.

    PubMed

    Martis, Roshan Joy; Acharya, U Rajendra; Tan, Jen Hong; Petznick, Andrea; Tong, Louis; Chua, Chua Kuang; Ng, Eddie Yin Kwee

    2013-10-01

    Intrinsic time-scale decomposition (ITD) is a new nonlinear method of time-frequency representation which can decipher the minute changes in the nonlinear EEG signals. In this work, we have automatically classified normal, interictal and ictal EEG signals using the features derived from the ITD representation. The energy, fractal dimension and sample entropy features computed on ITD representation coupled with decision tree classifier has yielded an average classification accuracy of 95.67%, sensitivity and specificity of 99% and 99.5%, respectively using 10-fold cross validation scheme. With application of the nonlinear ITD representation, along with conceptual advancement and improvement of the accuracy, the developed system is clinically ready for mass screening in resource constrained and emerging economy scenarios.

  12. Impact of the p53 status of tumor cells on extrinsic and intrinsic apoptosis signaling

    PubMed Central

    2013-01-01

    Background The p53 protein is the best studied target in human cancer. For decades, p53 has been believed to act mainly as a tumor suppressor and by transcriptional regulation. Only recently, the complex and diverse function of p53 has attracted more attention. Using several molecular approaches, we studied the impact of different p53 variants on extrinsic and intrinsic apoptosis signaling. Results We reproduced the previously published results within intrinsic apoptosis induction: while wild-type p53 promoted cell death, different p53 mutations reduced apoptosis sensitivity. The prediction of the impact of the p53 status on the extrinsic cell death induction was much more complex. The presence of p53 in tumor cell lines and primary xenograft tumor cells resulted in either augmented, unchanged or reduced cell death. The substitution of wild-type p53 by mutant p53 did not affect the extrinsic apoptosis inducing capacity. Conclusions In summary, we have identified a non-expected impact of p53 on extrinsic cell death induction. We suggest that the impact of the p53 status of tumor cells on extrinsic apoptosis signaling should be studied in detail especially in the context of therapeutic approaches that aim to restore p53 function to facilitate cell death via the extrinsic apoptosis pathway. PMID:23594441

  13. The Role of Intrinsic Flexibility in Signal Transduction Mediated by the Cell Cycle Regulator, p27Kip1

    SciTech Connect

    Galea, Charles A.; Nourse, Amanda; Wang, Yuefeng; Sivakolundu, Sivashankar G.; Heller, William T; Kriwacki, Richard W

    2008-02-01

    p27{sup Kip1} (p27), which controls eukaryotic cell division through interactions with cyclin-dependent kinases (Cdks), integrates and transduces promitogenic signals from various nonreceptor tyrosine kinases by orchestrating its own phosphorylation, ubiquitination and degradation. Intrinsic flexibility allows p27 to act as a 'conduit' for sequential signaling mediated by tyrosine and threonine phosphorylation and ubiquitination. While the structural features of the Cdk/cyclin-binding domain of p27 are understood, how the C-terminal regulatory domain coordinates multistep signaling leading to p27 degradation is poorly understood. We show that the 100-residue p27 C-terminal domain is extended and flexible when p27 is bound to Cdk2/cyclin A. We propose that the intrinsic flexibility of p27 provides a molecular basis for the sequential signal transduction conduit that regulates p27 degradation and cell division. Other intrinsically unstructured proteins possessing multiple sites of posttranslational modification may participate in similar signaling conduits.

  14. Cell Signaling Experiments Driven by Optical Manipulation

    PubMed Central

    Difato, Francesco; Pinato, Giulietta; Cojoc, Dan

    2013-01-01

    Cell signaling involves complex transduction mechanisms in which information released by nearby cells or extracellular cues are transmitted to the cell, regulating fundamental cellular activities. Understanding such mechanisms requires cell stimulation with precise control of low numbers of active molecules at high spatial and temporal resolution under physiological conditions. Optical manipulation techniques, such as optical tweezing, mechanical stress probing or nano-ablation, allow handling of probes and sub-cellular elements with nanometric and millisecond resolution. PicoNewton forces, such as those involved in cell motility or intracellular activity, can be measured with femtoNewton sensitivity while controlling the biochemical environment. Recent technical achievements in optical manipulation have new potentials, such as exploring the actions of individual molecules within living cells. Here, we review the progress in optical manipulation techniques for single-cell experiments, with a focus on force probing, cell mechanical stimulation and the local delivery of active molecules using optically manipulated micro-vectors and laser dissection. PMID:23698758

  15. Fine-scale organization of SI (area 3b) in the squirrel monkey revealed with intrinsic optical imaging.

    PubMed

    Chen, L M; Friedman, R M; Ramsden, B M; LaMotte, R H; Roe, A W

    2001-12-01

    Optical imaging of intrinsic cortical activity was used to study the somatotopic map and the representation of pressure, flutter, and vibration in area 3b of the squirrel monkey (Saimiri sciureus) cortex under pentothal or isoflurane anesthesia. The representation of the fingerpads in primary somatosensory cortex was investigated by stimulating the glabrous skin of distal fingerpads (D1-D5) with Teflon probes (3-mm diam) attached through an armature to force feedback-controlled torque motors. Under pentothal anesthesia, intrinsic signal maps in area 3b obtained in response to stimulation (trapezoidal indentation) of individual fingerpads showed focal activations. These activations (ranging from 0.5 to 1.0 mm) were discrete and exhibited minimal overlap between adjacent fingerpad representations. Consistent with previously published maps, a somatotopic representation of the fingerpads was observed with an orderly medial to lateral progression from the D5 to D1 fingerpads. Under isoflurane anesthesia, general topography was still maintained, but the representation of fingerpads on adjacent fingers had higher degrees of overlap than with pentothal anesthesia. Multi- and single-unit recordings in the activation zones confirmed the somatotopic maps. To examine preferential inputs from slowly adapting type I (SA) and rapidly adapting type I (RA) and type II (PC) mechanoreceptors, we applied stimuli consisting of sinusoidal indentations that produce sensations of pressure (1 Hz), flutter (30 Hz), and vibration (200 Hz). Under pentothal anesthesia, activation patterns to these different stimuli were focal and coincided on the cortex. Under isoflurane, activation zones from pressure, flutter, and vibratory stimuli differed in size and shape and often contained multiple foci, although overall topography was maintained. Subtraction and vector maps revealed cortical areas (approximate 250-microm diam) that were preferentially activated by the sensations of pressure, flutter

  16. Intrinsic optical fiber sensor for sensing organophosphate nerve agent using the modified cladding approach

    NASA Astrophysics Data System (ADS)

    Bansal, Lalitkumar; El-Sherif, Mahmoud

    2004-03-01

    The concept of modified cladding based sensors represents the largest class of intrinsic fiber optic chemical sensors. In this design, the passive cladding of the optical fiber is replaced by an active coating, called modified cladding. The analyte in this case diffuses into the coating and induces changes in the absorbance, fluorescence, or some other spectroscopic property of the modified cladding, the coating acts as a chemo-chromic transducer and sensing takes place by intensity modulation. This design i.e. of the coating based sensors, has found enormous applicability in the realm of chemical and biochemical sensing which also includes environmental monitoring and detection of chemical warfare agents. In this paper, the development of an intrinsic fiber optic sensor for detection of organophosphate dimethyl-methyl phoshopnate (DMMP) is presented. DMMP is a chemical precursor to the nerve agent sarin. The chemo-chromic transducer material used as a modified coating on the fiber core is NDSA (Naphthalene disulphonic acid) doped polypyrrole. This coating material shows conductivity and absorbance change when exposed to DMMP. The fabrication of the sensor device is a three step process which involves (a) etching a small section of the optical fiber to expose the core, (b) coating the etched section of the optical fiber with the polymer, (c) integration of sensor components and testing. Thin film characterization is done using the UV-Vis spectrophotometer on in-situ coated films of polypyrrole on a glass substrate to check for absorbance change upon exposure to DMMP. The development procedure is presented next and encouraging results are discussed.

  17. Intraoperative optical biopsy for brain tumors using spectro-lifetime properties of intrinsic fluorophores

    NASA Astrophysics Data System (ADS)

    Vasefi, Fartash; Kittle, David S.; Nie, Zhaojun; Falcone, Christina; Patil, Chirag G.; Chu, Ray M.; Mamelak, Adam N.; Black, Keith L.; Butte, Pramod V.

    2016-04-01

    We have developed and tested a system for real-time intra-operative optical identification and classification of brain tissues using time-resolved fluorescence spectroscopy (TRFS). A supervised learning algorithm using linear discriminant analysis (LDA) employing selected intrinsic fluorescence decay temporal points in 6 spectral bands was employed to maximize statistical significance difference between training groups. The linear discriminant analysis on in vivo human tissues obtained by TRFS measurements (N = 35) were validated by histopathologic analysis and neuronavigation correlation to pre-operative MRI images. These results demonstrate that TRFS can differentiate between normal cortex, white matter and glioma.

  18. Statistical analysis of intrinsic and extrinsic coupling losses for step-index polymer optical fibers.

    PubMed

    Werzinger, Stefan; Bunge, Christian-Alexander

    2015-08-24

    The intrinsic and extrinsic coupling losses of step-index polymer optical fibers are statistically examined by Monte Carlo simulations. In contrast to most existing models that linearly scale individual losses, a comprehensive analytic coupling loss model is used that also considers the interdependencies between mismatches in numerical aperture and core diameter, as well as radial and longitudinal offsets. As a typical example, the coupling losses of A4a.2 step-index multimode fibers are analyzed for an equilibrium mode distribution. The results show considerably less conservative coupling loss estimations than with traditional models, improving link power budgeting.

  19. New concept to break the intrinsic properties of organic semiconductors for optical sensing applications

    NASA Astrophysics Data System (ADS)

    Choy, Wallace C. H.

    2015-09-01

    As the intrinsic electrostatic limit, space charge limit (SCL) for photocurrent is a universal phenomenon which is fundamental important for organic semiconductors. We will demonstrate SCL breaking by a new plasmonic-electrical concept. As a proof-ofconcept, organic solar cells (OSCs) comprising metallic planar and grating electrodes are studied. Interestingly, although strong plasmonic resonances induce abnormally dense photocarriers around a grating anode, the grating incorporated inverted OSC is exempt from space charge accumulation (limit) and degradation of electrical properties. The plasmonic-electrical concept will open up a new way to manipulate both optical and electrical properties of semiconductor devices simultaneously.

  20. Acousto-optic filtering of lidar signals

    NASA Astrophysics Data System (ADS)

    Kolarov, G.; Deleva, A.; Mitsev, Ts.

    1992-07-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  1. Acousto-optic filtering of lidar signals

    NASA Technical Reports Server (NTRS)

    Kolarov, G.; Deleva, A.; Mitsev, TS.

    1992-01-01

    The predominant part of the noise in lidar receivers is created by the background radiation; therefore, one of the most important elements of the receiving optics is a spectrally selecting filter placed in front of the photodetector. Interference filters are usually used to transmit a given wavelength. Specific properties of the interference filters, such as simple design, reliability, small size, and large aperture, combined with high transmission coefficient and narrow spectral band, make them the preferred spectral device in many cases. However, problems arise in applications such as the Differential Absorption Lidar (DIAL) technique, where fast tuning within a wide spectral region is necessary. Tunable acousto-optical filters (TAOF), used recently in astrophysical observations to suppress the background radiation, can be employed with success in lidar sounding. They are attractive due to the possibility for fast spectral scanning with a narrow transmission band. The TAOF's advantages are fully evident in DIAL lidars where one must simultaneously receive signals at two laser frequencies.

  2. Spectroscopic Analysis of Various Phases of Water with an Intrinsic Near-Infrared Optical Sensor System

    NASA Astrophysics Data System (ADS)

    Igbinosun, Osazonamen J.

    Results and analysis are reported for near-infrared spectra obtained using an intrinsic optical sensor system. An experimental facility was designed to integrate fiber optic cables with an FTIR spectrometer. Wavelength-dependent spectral signatures were observed for the solid, liquid, and adsorbed phases of water at 1.94 and 1.45 micrometers. The data obtained can be used to characterize the water abundance of a medium on very small scales and can aid our understanding of the behavior of water and thermal properties of planetary surfaces by observing, for example, ice formation in void spaces between mineral grains. This system will be further developed for use in an environmental simulation facility to analyze Mars analog soils. The implications of this work could impact future space missions in regard to the availability of critical resources for human missions and the search for non-terrestrial life.

  3. Interrogating cyclic AMP signaling using optical approaches.

    PubMed

    Jiang, Jason Y; Falcone, Jeffrey L; Curci, Silvana; Hofer, Aldebaran M

    2017-03-01

    Optical reporters for cAMP represent a fundamental advancement in our ability to investigate the dynamics of cAMP signaling. These fluorescent sensors can measure changes in cAMP in single cells or in microdomains within cells as opposed to whole populations of cells required for other methods of measuring cAMP. The first optical cAMP reporters were FRET-based sensors utilizing dissociation of purified regulatory and catalytic subunits of PKA, introduced by Roger Tsien in the early 1990s. The utility of these sensors was vastly improved by creating genetically encoded versions that could be introduced into cells with transfection, the first of which was published in the year 2000. Subsequently, improved sensors have been developed using different cAMP binding platforms, optimized fluorescent proteins, and targeting motifs that localize to specific microdomains. The most common sensors in use today are FRET-based sensors designed around an Epac backbone. These rely on the significant conformational changes in Epac when it binds cAMP, altering the signal between FRET pairs flanking Epac. Several other strategies for optically interrogating cAMP have been developed, including fluorescent translocation reporters, dimerization-dependent FP based biosensors, BRET (bioluminescence resonance energy transfer)-based sensors, non-FRET single wavelength reporters, and sensors based on bacterial cAMP-binding domains. Other newly described mammalian cAMP-binding proteins such as Popdc and CRIS may someday be exploited in sensor design. With the proliferation of engineered fluorescent proteins and the abundance of cAMP binding targets in nature, the field of optical reporters for cAMP should continue to see rapid refinement in the coming years.

  4. Glutathione depletion regulates both extrinsic and intrinsic apoptotic signaling cascades independent from multidrug resistance protein 1

    PubMed Central

    Franco, Rodrigo; Bortner, Carl; Schmitz, Ingo; Cidlowski, John A.

    2014-01-01

    Glutathione (GSH) depletion is an important hallmark of apoptosis. We previously demonstrated that GSH depletion, by its efflux, regulates apoptosis by modulation of executioner caspase activity. However, both the molecular identity of the GSH transporter(s) involved and the signaling cascades regulating GSH loss remain obscure. We sought to determine the role of multidrug resistance protein 1 (MRP1) in GSH depletion and its regulatory role on extrinsic and intrinsic pathways of apoptosis. In human lymphoma cells, GSH depletion was stimulated rather than inhibited by pharmacological blockage of MRP1 with MK571. GSH loss was dependent on initiator caspases 8 and 9 activity. Genetic knock-down (>60%) of MRP1 by stable transfection with short-hairpin small interfering RNA significantly reduced MRP1 protein levels, which correlated directly with the loss of MRP1-mediated anion transport. However, GSH depletion and apoptosis induced by both extrinsic and intrinsic pathways were not affected by MRP1 knock-down. Interestingly, stimulation of GSH loss by MK571 also enhanced the initiator phase of apoptosis by stimulating initiator caspase 8 and 9 activity and pro-apoptotic BID cleavage. Our results clearly show that caspase-dependent GSH loss and apoptosis are not mediated by MRP1 proteins and that GSH depletion stimulates the initiation phase of apoptosis in lymphoid cells. PMID:24146141

  5. High-definition optical coherence tomography intrinsic skin ageing assessment in women: a pilot study.

    PubMed

    Boone, M A L M; Suppa, M; Marneffe, A; Miyamoto, M; Jemec, G B E; Del Marmol, V

    2015-10-01

    Several non-invasive two-dimensional techniques with different lateral resolution and measurable depth range have proved to be useful in assessing and quantifying morphological changes in skin ageing. Among these, only in vivo microscopy techniques permit histometric measurements in vivo. Qualitative and quantitative assessment of chronological (intrinsic) age-related (IAR) morphological changes of epidermis, dermo-epidermal junction (DEJ), papillary dermis (PD), papillary-reticular dermis junction and reticular dermis (RD) have been performed by high-definition optical coherence tomography in real time 3-D. HD-OCT images were taken at the internal site of the right upper arm. Qualitative HD-OCT IAR descriptors were reported at skin surface, at epidermal layer, DEJ, PD and upper RD. Quantitative evaluation of age-related compaction and backscattered intensity or brightness of different skin layers was performed by using the plugin plot z-axis profile of ImageJ(®) software permitting intensity assessment of HD-OCT (DICOM) images (3-D images). Analysis was in blind from all clinical information. Sixty, fair-skinned (Fitzpatrick types I-III) healthy females were analysed retrospectively in this study. The subjects belonged to three age groups: twenty in group I aged 20-39, twenty in group II aged 40-59 and twenty in group III aged 60-79. Only intrinsic ageing in women has been studied. Significant age-related qualitative and quantitative differences could be noticed. IAR changes in dermal matrix fibers morphology/organisation and in microvasculature were observed. The brightness and compaction of the different skin layers increased significantly with intrinsic skin ageing. The depth of visibility of fibers in RD increased significantly in the older age group. In conclusion, HD-OCT allows 3-D in vivo and real time qualitative and quantitative assessment of chronological (intrinsic) age-related morphological skin changes at high resolution from skin surface to a depth

  6. The PIR domain of Grb14 is an intrinsically unstructured protein: implication in insulin signaling.

    PubMed

    Moncoq, Karine; Broutin, Isabelle; Larue, Valéry; Perdereau, Dominique; Cailliau, Katia; Browaeys-Poly, Edith; Burnol, Anne-Françoise; Ducruix, Arnaud

    2003-11-20

    Grb14 belongs to the Grb7 family of adapter proteins and was identified as a negative regulator of insulin signal transduction. Its inhibitory effect on the insulin receptor kinase activity is controlled by a newly discovered domain called PIR. To investigate the biochemical and biophysical characteristics of this new domain, we cloned and purified recombinant PIR-SH2, PIR, and SH2 domains. The isolated PIR and PIR-SH2 domains were physiologically active and inhibited insulin-induced reinitiation of meiosis in the Xenopus oocytes system. However, NMR experiments on (15)N-labelled PIR revealed that it did not present secondary structure. These results suggest that the PIR domain belongs to the growing family of intrinsically unstructured proteins.

  7. Extrinsic and intrinsic signals converge on the Runx1/CBFβ transcription factor for nonpeptidergic nociceptor maturation

    PubMed Central

    Huang, Siyi; O'Donovan, Kevin J; Turner, Eric E; Zhong, Jian; Ginty, David D

    2015-01-01

    The generation of diverse neuronal subtypes involves specification of neural progenitors and, subsequently, postmitotic neuronal differentiation, a relatively poorly understood process. Here, we describe a mechanism whereby the neurotrophic factor NGF and the transcription factor Runx1 coordinate postmitotic differentiation of nonpeptidergic nociceptors, a major nociceptor subtype. We show that the integrity of a Runx1/CBFβ holocomplex is crucial for NGF-dependent nonpeptidergic nociceptor maturation. NGF signals through the ERK/MAPK pathway to promote expression of Cbfb but not Runx1 prior to maturation of nonpeptidergic nociceptors. In contrast, transcriptional initiation of Runx1 in nonpeptidergic nociceptor precursors is dependent on the homeodomain transcription factor Islet1, which is largely dispensable for Cbfb expression. Thus, an NGF/TrkA-MAPK-CBFβ pathway converges with Islet1-Runx1 signaling to promote Runx1/CBFβ holocomplex formation and nonpeptidergic nociceptor maturation. Convergence of extrinsic and intrinsic signals to control heterodimeric transcription factor complex formation provides a robust mechanism for postmitotic neuronal subtype specification. DOI: http://dx.doi.org/10.7554/eLife.10874.001 PMID:26418744

  8. Intrinsic excitability state of local neuronal population modulates signal propagation in feed-forward neural networks

    NASA Astrophysics Data System (ADS)

    Han, Ruixue; Wang, Jiang; Yu, Haitao; Deng, Bin; Wei, Xilei; Qin, Yingmei; Wang, Haixu

    2015-04-01

    Reliable signal propagation across distributed brain areas is an essential requirement for cognitive function, and it has been investigated extensively in computational studies where feed-forward network (FFN) is taken as a generic model. But it is still unclear how distinct local network states, which are intrinsically generated by synaptic interactions within each layer, would affect the ability of FFN to transmit information. Here we investigate the impact of such network states on propagating transient synchrony (synfire) and firing rate by a combination of numerical simulations and analytical approach. Specifically, local network dynamics is attributed to the competition between excitatory and inhibitory neurons within each layer. Our results show that concomitant with different local network states, the performance of signal propagation differs dramatically. For both synfire propagation and firing rate propagation, there exists an optimal local excitability state, respectively, that optimizes the performance of signal propagation. Furthermore, we find that long-range connections strongly change the dependence of spiking activity propagation on local network state and propose that these two factors work jointly to determine information transmission across distributed networks. Finally, a simple mean field approach that bridges response properties of long-range connectivity and local subnetworks is utilized to reveal the underlying mechanism.

  9. Effect of intrinsic organic carbon on the optical properties of fresh diesel soot

    PubMed Central

    Adler, Gabriella; Riziq, Ali Abo; Erlick, Carynelisa; Rudich, Yinon

    2010-01-01

    This study focuses on the retrieval of the normalized mass absorption cross section (MAC) of soot using theoretical calculations that incorporate new measurements of the optical properties of organic carbon (OC) intrinsic to fresh diesel soot. Intrinsic OC was extracted by water and an organic solvent, and the complex refractive index of the extracted OC was derived at 532 and 355-nm wavelengths using cavity ring-down aerosol spectrometry. The extracted OC was found to absorb weakly in the visible wavelengths and moderately at blue wavelengths. The mass ratio of OC and elemental carbon (EC) in the collected particles was evaluated using a thermo-optical method. The measured EC/OC ratio in the soot exhibited substantial variability from measurement to measurement, ranging between 2 and 5. To test the sensitivity of the MAC to this variability, three different EC/OC ratios (2∶1, 1∶1, and 1∶2) were chosen as representative. Particle size and spherule morphology were estimated using scanning electron microscopy, and the soot was found to be primarily in the form of aggregates with a dominant aggregate diameter mode in the range 200–250 nm. The measured refractive index of the extracted OC was used with a variety of theoretical models to calculate the MAC of internally mixed diesel soot at 532 and 355 nm. We conclude that Rayleigh–Debye–Gans theory on clusters of coated spherules and T-matrix of a solid EC spheroid coated by intrinsic OC are both consistent with previous measurements; however, Rayleigh–Debye–Gans theory provides a more realistic physical model for the calculation PMID:20018649

  10. Effect of intrinsic organic carbon on the optical properties of fresh diesel soot.

    PubMed

    Adler, Gabriella; Riziq, Ali Abo; Erlick, Carynelisa; Rudich, Yinon

    2010-04-13

    This study focuses on the retrieval of the normalized mass absorption cross section (MAC) of soot using theoretical calculations that incorporate new measurements of the optical properties of organic carbon (OC) intrinsic to fresh diesel soot. Intrinsic OC was extracted by water and an organic solvent, and the complex refractive index of the extracted OC was derived at 532 and 355-nm wavelengths using cavity ring-down aerosol spectrometry. The extracted OC was found to absorb weakly in the visible wavelengths and moderately at blue wavelengths. The mass ratio of OC and elemental carbon (EC) in the collected particles was evaluated using a thermo-optical method. The measured EC/OC ratio in the soot exhibited substantial variability from measurement to measurement, ranging between 2 and 5. To test the sensitivity of the MAC to this variability, three different EC/OC ratios (21, 11, and 12) were chosen as representative. Particle size and spherule morphology were estimated using scanning electron microscopy, and the soot was found to be primarily in the form of aggregates with a dominant aggregate diameter mode in the range 200-250 nm. The measured refractive index of the extracted OC was used with a variety of theoretical models to calculate the MAC of internally mixed diesel soot at 532 and 355 nm. We conclude that Rayleigh-Debye-Gans theory on clusters of coated spherules and T-matrix of a solid EC spheroid coated by intrinsic OC are both consistent with previous measurements; however, Rayleigh-Debye-Gans theory provides a more realistic physical model for the calculation.

  11. B cell-intrinsic TLR7 signaling is essential for the development of spontaneous germinal centers.

    PubMed

    Soni, Chetna; Wong, Eric B; Domeier, Phillip P; Khan, Tahsin N; Satoh, Takashi; Akira, Shizuo; Rahman, Ziaur S M

    2014-11-01

    Spontaneous germinal center (Spt-GC) B cells and follicular helper T cells generate high-affinity autoantibodies that are involved in the development of systemic lupus erythematosus. TLRs play a pivotal role in systemic lupus erythematosus pathogenesis. Although previous studies focused on the B cell-intrinsic role of TLR-MyD88 signaling on immune activation, autoantibody repertoire, and systemic inflammation, the mechanisms by which TLRs control the formation of Spt-GCs remain unclear. Using nonautoimmune C57BL/6 (B6) mice deficient in MyD88, TLR2, TLR3, TLR4, TLR7, or TLR9, we identified B cell-intrinsic TLR7 signaling as a prerequisite to Spt-GC formation without the confounding effects of autoimmune susceptibility genes and the overexpression of TLRs. TLR7 deficiency also rendered autoimmune B6.Sle1b mice unable to form Spt-GCs, leading to markedly decreased autoantibodies. Conversely, B6.yaa and B6.Sle1b.yaa mice expressing an extra copy of TLR7 and B6.Sle1b mice treated with a TLR7 agonist had increased Spt-GCs and follicular helper T cells. Further, TLR7/MyD88 deficiency led to compromised B cell proliferation and survival after B cell stimulation both in vitro and in vivo. In contrast, TLR9 inhibited Spt-GC development. Our findings demonstrate an absolute requirement for TLR7 and a negative regulatory function for TLR9 in Spt-GC formation under nonautoimmune and autoimmune conditions. Our data suggest that, under nonautoimmune conditions, Spt-GCs initiated by TLR7 produce protective Abs. However, in the presence of autoimmune susceptibility genes, TLR7-dependent Spt-GCs produce pathogenic autoantibodies. Thus, a single copy of TLR7 in B cells is the minimal requirement for breaking the GC-tolerance checkpoint.

  12. B cell-intrinsic TLR7 signaling is essential for the development of spontaneous germinal centers

    PubMed Central

    Soni, Chetna; Wong, Eric B.; Domeier, Phillip P.; Khan, Tahsin N.; Satoh, Takashi; Akira, Shizuo; Rahman, Ziaur S.M.

    2014-01-01

    Spontaneous germinal center (Spt-GC) B cells and follicular helper T cells (Tfh) generate high affinity autoantibodies involved in the development of systemic lupus erythematosus (SLE). Toll like receptors (TLRs) play a pivotal role in SLE pathogenesis. While previous studies have focused on the B cell intrinsic role of TLR-MyD88 signaling on immune activation, autoantibody repertoire and systemic inflammation, a thorough investigation of the mechanisms by which TLRs control the formation of Spt-GCs remains unclear. Using non-autoimmune C57BL/6 (B6) mice deficient in MyD88, TLR2, 3, 4, 7 or 9, we identified B cell-intrinsic TLR7 signaling as a prerequisite to Spt-GC formation without the confounding effects of autoimmune susceptibility genes and the overexpression of TLRs. TLR7 deficiency also rendered autoimmune B6.Sle1b mice unable to form Spt-GCs, leading to markedly decreased autoantibodies. Conversely, B6.yaa and B6.Sle1b.yaa mice expressing an extra copy of TLR7 and B6.Sle1b mice treated with a TLR7 agonist had increased Spt-GCs and Tfh. Further, TLR7/ MyD88 deficiency led to compromised B cell proliferation and survival after B cell stimulation both in vitro and in vivo. In contrast, TLR9 inhibited Spt-GC development. Our findings demonstrate an absolute requirement of TLR7 and a negative regulatory function for TLR9 in Spt-GC formation under non-autoimmune and autoimmune conditions. Our data suggest that, under non-autoimmune conditions, Spt-GCs initiated by TLR7 produce protective antibodies. However, in the presence of autoimmune susceptibility genes, TLR7 dependent Spt-GCs produce pathogenic autoantibodies. Thus, a single copy of TLR7 in B cells is the minimal requirement for breaking the GC-tolerance checkpoint. PMID:25252960

  13. Optical coherence microscopy for deep tissue imaging of the cerebral cortex with intrinsic contrast

    PubMed Central

    Srinivasan, Vivek J.; Radhakrishnan, Harsha; Jiang, James Y.; Barry, Scott; Cable, Alex E.

    2012-01-01

    In vivo optical microscopic imaging techniques have recently emerged as important tools for the study of neurobiological development and pathophysiology. In particular, two-photon microscopy has proved to be a robust and highly flexible method for in vivo imaging in highly scattering tissue. However, two-photon imaging typically requires extrinsic dyes or contrast agents, and imaging depths are limited to a few hundred microns. Here we demonstrate Optical Coherence Microscopy (OCM) for in vivo imaging of neuronal cell bodies and cortical myelination up to depths of ~1.3 mm in the rat neocortex. Imaging does not require the administration of exogenous dyes or contrast agents, and is achieved through intrinsic scattering contrast and image processing alone. Furthermore, using OCM we demonstrate in vivo, quantitative measurements of optical properties (index of refraction and attenuation coefficient) in the cortex, and correlate these properties with laminar cellular architecture determined from the images. Lastly, we show that OCM enables direct visualization of cellular changes during cell depolarization and may therefore provide novel optical markers of cell viability. PMID:22330462

  14. Specialized optical fiber sensor for nondestructive intrinsic quality measurement of Averrhoa Carambola

    NASA Astrophysics Data System (ADS)

    Omar, Ahmad Fairuz; Matjafri, Mohd Zubir

    2013-09-01

    This paper presents an innovative and low-cost approach for nondestructive fruit quality analysis. The specialized optical fiber sensor developed and presented in this paper used a monochromatic wavelength, rather than a broad spectrum, to measure the intact carambola (star fruit) intrinsic quality, namely pH and firmness. The main objective of this research was to investigate the two optical fiber sensors used in this work, namely, the optical fiber red system (OF-RS) that operated with the peak sensitivity at 635 nm and the optical fiber near the infrared spectroscopy system (OF-NIRS) that operated with the peak sensitivity at 880 nm. Both systems showed good accuracy in the pH and firmness measurement of the intact carambola with the correlation coefficient R over 0.75, and the measurement results were comparable with those of the commercial spectrometer. The best measurement results were obtained using OF-RS (pH: R = 0.876; the root mean square error ( RMSE) = 0.211 pH; firmness: R = 0.872; RMSE = 0.909 kgf).

  15. Intrinsic Toll-like receptor signalling drives regulatory function in B cells.

    PubMed

    Shen, Ping; Lampropoulou, Vicky; Stervbo, Ulrik; Hilgenberg, Ellen; Ries, Stefanie; Mecqinion, Aurelie; Fillatreau, Simon

    2013-01-01

    B cells can contribute to immunity through production of antibodies, presentation of antigen to T cells, and secretion of cytokines. B cell activation can result in various outcomes for the host. In general B cell responses are beneficial during infections, and deleterious during autoimmune diseases. However, B cells can also limit host defence against pathogens, and protect from autoimmune pathologies. B cells can therefore act both as drivers and as regulators of immunity. Understanding how these opposite functions are mediated shall stimulate the elaboration of novel approaches for manipulating the immune system. B cells might acquire distinct functional properties depending on their mode of activation. Antigen-specific B cell responses require triggering of B cell receptor (BCR) by antigen, and provision of helper signals by T cells. B cells also express various innate immune receptors, and can directly respond to microbial products. Here, we discuss how intrinsic signalling via Toll-like receptors contributes to the suppressive functions of B cells during autoimmune and infectious diseases.

  16. Coherent signal processing in optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Kulkarni, Manish Dinkarrao

    1999-09-01

    Optical coherence tomography (OCT) is a novel method for non-invasive sub-surface imaging of biological tissue micro-structures. OCT achieves high spatial resolution ( ~ 15 m m in three dimensions) using a fiber-optically integrated system which is suitable for application in minimally invasive diagnostics, including endoscopy. OCT uses an optical heterodyne detection technique based on white light interferometry. Therefore extremely faint reflections ( ~ 10 fW) are routinely detected with high spatial localization. The goal of this thesis is twofold. The first is to present a theoretical model for describing image formation in OCT, and attempt to enhance the current level of understanding of this new modality. The second objective is to present signal processing methods for improving OCT image quality. We present deconvolution algorithms to obtain improved longitudinal resolution in OCT. This technique may be implemented without increasing system complexity as compared to current clinical OCT systems. Since the spectrum of the light backscattered from bio-scatterers is closely associated with ultrastructural variations in tissue, we propose a new technique for measuring spectra as a function of depth. This advance may assist OCT in differentiating various tissue types and detecting abnormalities within a tissue. In addition to depth resolved spectroscopy, Doppler processing of OCT signals can also improve OCT image contrast. We present a new technique, termed color Doppler OCT (CDOCT). It is an innovative extension of OCT for performing spatially localized optical Doppler velocimetry. Micron-resolution imaging of blood flow in sub-surface vessels in living tissue using CDOCT is demonstrated. The fundamental issues regarding the trade- off between the velocity estimation precision and image acquisition rate are presented. We also present novel algorithms for high accuracy velocity estimation. In many blood vessels velocities tend to be on the order of a few cm

  17. Optical signal monitoring in phase modulated optical fiber transmission systems

    NASA Astrophysics Data System (ADS)

    Zhao, Jian

    Optical performance monitoring (OPM) is one of the essential functions for future high speed optical networks. Among the parameters to be monitored, chromatic dispersion (CD) is especially important since it has a significant impact on overall system performance. In this thesis effective CD monitoring approaches for phase-shift keying (PSK) based optical transmission systems are investigated. A number of monitoring schemes based on radio frequency (RF) spectrum analysis and delay-tap sampling are proposed and their performance evaluated. A method for dispersion monitoring of differential phase-shift keying (DPSK) signals based on RF power detection is studied. The RF power spectrum is found to increase with the increase of CD and decrease with polarization mode dispersion (PMD). The spectral power density dependence on CD is studied theoretically and then verified through simulations and experiments. The monitoring sensitivity for nonreturn-to-zero differential phase-shift keying (NRZ-DPSK) and return-to-zero differential phase-shift keying (RZ-DPSK) based systems can reach 80ps/nm/dB and 34ps/nm/dB respectively. The scheme enables the monitoring of differential group delay (DGD) and CD simultaneously. The monitoring sensitivity of CD and DGD can reach 56.7ps/nm/dB and 3.1ps/dB using a bandpass filter. The effects of optical signal-to-noise ratio (OSNR), DGD, fiber nonlinearity and chirp on the monitoring results are investigated. Two RF pilot tones are employed for CD monitoring of DPSK signals. Specially selected pilot tone frequencies enable good monitoring sensitivity with minimum influence on the received signals. The dynamic range exceeding 35dB and monitoring sensitivity up to 9.5ps/nm/dB are achieved. Asynchronous sampling technique is employed for CD monitoring. A signed CD monitoring method for 10Gb/s NRZ-DPSK and RZ-DPSK systems using asynchronous delay-tap sampling technique is studied. The demodulated signals suffer asymmetric waveform distortion if

  18. High-speed and reconfigurable all-optical signal processing for phase and amplitude modulated signals

    NASA Astrophysics Data System (ADS)

    Khaleghi, Salman

    Technology has empowered people in all walks of life to generate, store, and communicate enormous amounts of data. Recent technological advances in high-speed backbone data networks, together with the growing trend toward bandwidth-demanding applications such as data and video sharing, cloud computing, and data collection systems, have created a need for higher capacities in signal transmission and signal processing. Optical communication systems have long benefited from the large bandwidth of optical signals (beyond tera-hertz) to transmit information. Through the use of optical signal processing techniques, this Ph.D. dissertation explores the potential of very-high-speed optics to assist electronics in processing huge amounts of data at high speeds. Optical signal processing brings together various fields of optics and signal processing---nonlinear devices and processes, analog and digital signals, and advanced data modulation formats---to achieve high-speed signal processing functions that can potentially operate at the line rate of fiber optic communications. Information can be encoded in amplitude, phase, wavelength, polarization, and spatial features of an optical wave to achieve high-capacity transmission. Many advances in the key enabling technologies have led to recent research in optical signal processing for digital signals that are encoded in one or more of these dimensions. Optical Kerr nonlinearities have femto-second response times that have been exploited for fast processing of optical signals. Various optical nonlinearities and chromatic dispersions have enabled key sub-system applications such as wavelength conversion, multicasting, multiplexing, demultiplexing, and tunable optical delays. In this Ph.D. dissertation, we employ these recent advances in the enabling technologies for high-speed optical signal processing to demonstrate various techniques that can process phase- and amplitude-encoded optical signals at the line rate of optics. We use

  19. Intrinsic Fiber Optic Chemical Sensors for Subsurface Detection of CO2

    SciTech Connect

    Alonso, Jesus

    2016-01-01

    Intelligent Optical Systems, Inc. has developed distributed intrinsic fiber optic sensors to directly quantify the concentration of dissolved or gas-phase CO2 for leak detection or plume migration in carbon capture and sequestration (CCS). The capability of the sensor for highly sensitive detection of CO2 in the pressure and temperature range of 15 to 2,000 psi and 25°C to 175°C was demonstrated, as was the capability of operating in highly corrosive and contaminated environments such as those often found in CO2 injection sites. The novel sensor system was for the first time demonstrated deployed in a deep well, detecting multiple CO2 releases, in real time, at varying depths. Early CO2 release detection, by means of a sensor cable integrating multiple sensor segments, was demonstrated, as was the capability of quantifying the leak. The novel fiber optic sensor system exhibits capabilities not achieved by any other monitoring technology. This project represents a breakthrough in monitoring capabilities for CCS applications.

  20. A New Type Of Fiber Optic Biosensor Based On The Intrinsic Fluorescence Of Immobilized Flavoproteins

    NASA Astrophysics Data System (ADS)

    Wolfbeis, Otto S.; Trettnak, Wolfgang

    1990-02-01

    We describe a new biosensor for monitoring the concentration of enzyme glucose, lactate, and other substrates that are metabolized by an oxidation process. The method is based on the finding that enzymes having FAD as a prosthetic group change their fluorescence during interaction with a substrate. Typical enzymes that have been studied include glucose oxidase (GOD), lactate mono-oxygenase (LMO), and cholesterol oxidase (ChOD). Their fluorescence is monitored via fiber optic light guides at wavelengths above 500 nm, following fluorescence excitation at around 410 - 450 nm. The relative fluorescence intensities of the enzymes vary to a large extent, being highest for LMO, and rather low for ChOD. Typical detection limits are in the 0.5 mM range for lactate and 1.5 mM for glucose at ambient oxygen pressure. A characteristic feature of this sensor is the narrow dynamic range which usually does not exceed 3 mM. This can be explained in terms of enzyme kinetics and diffusional processes. Unlike optical biosensors based on measurement of the intrinsic fluorescence of NADH, this sensor type has the advantages of full reversibility (because reduced FAD-based enzymes accept oxygen as a second substrate) and analytical wavelengths that are compatible with plastic or glass fiber optics. It is fairly simple in construction because the enzyme acts as both the recognition and transduction element. The method also has been applied successfully in an flow injection analysis-like type of arrangement.

  1. Integrated Optics for Planar imaging and Optical Signal Processing

    NASA Astrophysics Data System (ADS)

    Song, Qi

    Silicon photonics is a subject of growing interest with the potential of delivering planar electro-optical devices with chip scale integration. Silicon-on-insulator (SOI) technology has provided a marvelous platform for photonics industry because of its advantages in integration capability in CMOS circuit and countless nonlinearity applications in optical signal processing. This thesis is focused on the investigation of planar imaging techniques on SOI platform and potential applications in ultra-fast optical signal processing. In the first part, a general review and background introduction about integrated photonics circuit and planar imaging technique are provided. In chapter 2, planar imaging platform is realized by a silicon photodiode on SOI chip. Silicon photodiode on waveguide provides a high numerical aperture for an imaging transceiver pixel. An erbium doped Y2O3 particle is excited by 1550nm Laser and the fluorescent image is obtained with assistance of the scanning system. Fluorescence image is reconstructed by using image de-convolution technique. Under photovoltaic mode, we use an on-chip photodiode and an external PIN photodiode to realize similar resolution as 5μm. In chapter 3, a time stretching technique is developed to a spatial domain to realize a 2D imaging system as an ultrafast imaging tool. The system is evaluated based on theoretical calculation. The experimental results are shown for a verification of system capability to imaging a micron size particle or a finger print. Meanwhile, dynamic information for a moving object is also achieved by correlation algorithm. In chapter 4, the optical leaky wave antenna based on SOI waveguide has been utilized for imaging applications and extensive numerical studied has been conducted. and the theoretical explanation is supported by leaky wave theory. The highly directive radiation has been obtained from the broadside with 15.7 dB directivity and a 3dB beam width of ΔØ 3dB ≈ 1.65° in free space

  2. Signal processing for fiber optic gyroscope (FOG)

    NASA Astrophysics Data System (ADS)

    Tanaka, Ryuichi; Kurokawa, Akihiro; Sato, Yoshiyuki; Magome, Tsutomu; Hayakawa, Yoshiaki; Nakatani, Ichiro; Kawaguchi, Junichiro

    1994-11-01

    A fiber-optic gyroscope (FOG) is expected to be the next generation gyroscope for guidance and control, because of various advantages. We have been developing the FOG-Inertial Navigation and Guidance (ING) for M-V satellite launching rocket of the Institute of Space and Astronautical Science (ISAS) since 1990. The FOG-ING consists of an Inertial Measurement Unit (IMU) and an Central Processing Unit Assembly. At current status, the proto-flight model FOG-IMU is being actively developed. And the flight test of the FOG-ING was performed on February 20, 1993, aboard M-3SII-7 satellite launching rocket at the ISAS test facilities in Uchinoura, Japan. This paper presents the signal processing technologies of our FOG which are used for the above FOG-ING.

  3. Epitaxial Growth of Atomically Smooth Aluminum on Silicon and Its Intrinsic Optical Properties.

    PubMed

    Cheng, Fei; Su, Ping-Hsiang; Choi, Junho; Gwo, Shangjr; Li, Xiaoqin; Shih, Chih-Kang

    2016-11-22

    Aluminum (Al) provides an excellent material platform for plasmonic applications in the ultraviolet (UV) regime due to its low loss coefficient at UV wavelengths. To fully realize the potential of this material, it is imperative to create nanostructures with minimal defects in order to prevent light scattering and better support plasmonic resonances. In this work, we report the successful development of atomically smooth epitaxial Al films on silicon. These epitaxial Al thin films facilitate the creation of fine plasmonic nanostructures and demonstrate considerable loss reduction in the UV frequency range, in comparison to the polycrystalline Al films based on spectroscopic ellipsometry measurements. Remarkably, our measurements on the epitaxial Al film grown using the two-step method suggest that the intrinsic loss in Al is significantly lower, by up to a factor of 2 in the UV range, with respect to current widely quoted Palik's values extracted from polycrystalline films. These high-quality epitaxial Al films provide an ideal platform for UV plasmonics. In addition, the availability of intrinsic optical constants will enable more accurate theoretical predictions to guide the device design.

  4. Label-free imaging of amyloids using their intrinsic linear and nonlinear optical properties

    PubMed Central

    Johansson, Patrik K.; Koelsch, Patrick

    2017-01-01

    The optical properties of amyloid fibers are often distinct from those of the source protein in its non-fibrillar form. These differences can be utilized for label-free imaging or characterization of such structures, which is particularly important for understanding amyloid fiber related diseases such as Alzheimer’s and Parkinson’s disease. We demonstrate that two amyloid forming proteins, insulin and β-lactoglobulin (β-LG), show intrinsic fluorescence with emission spectra that are dependent on the excitation wavelength. Additionally, a new fluorescence peak at about 430 nm emerges for β-LG in its amyloid state. The shift in emission wavelength is related to the red edge excitation shift (REES), whereas the additional fluorescence peak is likely associated with charge delocalization along the fiber backbone. Furthermore, the spherulitic amyloid plaque-like superstructures formed from the respective proteins were imaged label-free with confocal fluorescence, multiphoton excitation fluorescence (MPEF), and second-harmonic generation (SHG) microscopy. The latter two techniques in particular yield images with a high contrast between the amyloid fiber regions and the core of amorphously structured protein. Strong multiphoton absorption (MPA) for the amyloid fibers is a likely contributor to the observed contrast in the MPEF images. The crystalline fibrillar region provides even higher contrast in the SHG images, due to the inherently ordered non-centrosymmetric structure of the fibers together with their non-isotropic arrangement. Finally, we show that MPEF from the insulin spherulites exhibits a spectral dependence on the excitation wavelength. This behavior is consistent with the REES phenomenon, which we hypothesize is the origin of this observation. The presented results suggest that amyloid deposits can be identified and structurally characterized based on their intrinsic optical properties, which is important for probe-less and label-free identification

  5. Parametric signal amplification to create a stiff optical bar

    NASA Astrophysics Data System (ADS)

    Somiya, K.; Kataoka, Y.; Kato, J.; Saito, N.; Yano, K.

    2016-02-01

    An optical cavity consisting of optically trapped mirrors makes a resonant bar that can be stiffer than diamond. A limitation of the stiffness arises in the length of the optical bar as a consequence of the finite light speed. High laser power and light mass mirrors are essential for realization of a long and stiff optical bar that can be useful for example in the gravitational-wave detector aiming at the observation of a signal from neutron-star collisions, supernovae, etc. In this letter, we introduce a parametric signal amplification scheme that realizes the long and stiff optical bar with a non-linear crystal inside the signal-recycling cavity.

  6. System and methods for determining masking signals for applying empirical mode decomposition (EMD) and for demodulating intrinsic mode functions obtained from application of EMD

    DOEpatents

    Senroy, Nilanjan [New Delhi, IN; Suryanarayanan, Siddharth [Littleton, CO

    2011-03-15

    A computer-implemented method of signal processing is provided. The method includes generating one or more masking signals based upon a computed Fourier transform of a received signal. The method further includes determining one or more intrinsic mode functions (IMFs) of the received signal by performing a masking-signal-based empirical mode decomposition (EMD) using the at least one masking signal.

  7. B cell IFN-γ receptor signaling promotes autoimmune germinal centers via cell-intrinsic induction of BCL-6

    PubMed Central

    Jackson, Shaun W.; Jacobs, Holly M.; Arkatkar, Tanvi; Dam, Elizabeth M.; Scharping, Nicole E.; Kolhatkar, Nikita S.; Hou, Baidong; Buckner, Jane H.

    2016-01-01

    Dysregulated germinal center (GC) responses are implicated in the pathogenesis of human autoimmune diseases, including systemic lupus erythematosus (SLE). Although both type 1 and type 2 interferons (IFNs) are involved in lupus pathogenesis, their respective impacts on the establishment of autoimmune GCs has not been addressed. In this study, using a chimeric model of B cell-driven autoimmunity, we demonstrate that B cell type 1 IFN receptor signals accelerate, but are not required for, lupus development. In contrast, B cells functioning as antigen-presenting cells initiate CD4+ T cell activation and IFN-γ production, and strikingly, B cell–intrinsic deletion of the IFN-γ receptor (IFN-γR) abrogates autoimmune GCs, class-switched autoantibodies (auto-Abs), and systemic autoimmunity. Mechanistically, although IFN-γR signals increase B cell T-bet expression, B cell–intrinsic deletion of T-bet exerts an isolated impact on class-switch recombination to pathogenic auto-Ab subclasses without impacting GC development. Rather, in both mouse and human B cells, IFN-γ synergized with B cell receptor, toll-like receptor, and/or CD40 activation signals to promote cell-intrinsic expression of the GC master transcription factor, B cell lymphoma 6 protein. Our combined findings identify a novel B cell–intrinsic mechanism whereby IFN signals promote lupus pathogenesis, implicating this pathway as a potential therapeutic target in SLE. PMID:27069113

  8. Deficient FGF signaling causes optic nerve dysgenesis and ocular coloboma.

    PubMed

    Cai, Zhigang; Tao, Chenqi; Li, Hongge; Ladher, Raj; Gotoh, Noriko; Feng, Gen-Sheng; Wang, Fen; Zhang, Xin

    2013-07-01

    FGF signaling plays a pivotal role in eye development. Previous studies using in vitro chick models and systemic zebrafish mutants have suggested that FGF signaling is required for the patterning and specification of the optic vesicle, but due to a lack of genetic models, its role in mammalian retinal development remains elusive. In this study, we show that specific deletion of Fgfr1 and Fgfr2 in the optic vesicle disrupts ERK signaling, which results in optic disc and nerve dysgenesis and, ultimately, ocular coloboma. Defective FGF signaling does not abrogate Shh or BMP signaling, nor does it affect axial patterning of the optic vesicle. Instead, FGF signaling regulates Mitf and Pax2 in coordinating the closure of the optic fissure and optic disc specification, which is necessary for the outgrowth of the optic nerve. Genetic evidence further supports that the formation of an Frs2α-Shp2 complex and its recruitment to FGF receptors are crucial for downstream ERK signaling in this process, whereas constitutively active Ras signaling can rescue ocular coloboma in the FGF signaling mutants. Our results thus reveal a previously unappreciated role of FGF-Frs2α-Shp2-Ras-ERK signaling axis in preventing ocular coloboma. These findings suggest that components of FGF signaling pathway may be novel targets in the diagnosis of and the therapeutic interventions for congenital ocular anomalies.

  9. Intrinsic protein flexibility in regulation of cell proliferation: advantages for signaling and opportunities for novel therapeutics.

    PubMed

    Follis, Ariele Viacava; Galea, Charles A; Kriwacki, Richard W

    2012-01-01

    It is now widely recognized that intrinsically disordered (or unstructured) proteins (IDPs, or IUPs) are found in organisms from all kingdoms of life. In eukaryotes, IDPs are highly abundant and perform a wide range of biological functions, including regulation and signaling. Despite increased interest in understanding the structural biology of IDPs, questions remain regarding the mechanisms through which disordered proteins perform their biological function(s). In other words, what are the relationships between disorder and function for IDPs? Several excellent reviews have recently been published that discuss the structural properties of IDPs.1-3 Here, we discuss two IDP systems which illustrate features of dynamic complexes. In the first section, we discuss two IDPs, p21 and p27, which regulate the mammalian cell division cycle by inhibiting cyclin-dependent kinases (Cdks). In the second section, we discuss recent results from Follis, Hammoudeh, Metallo and coworkers demonstrating that the IDP Myc can be bound and inhibited by small molecules through formation of dynamic complexes. Previous studies have shown that polypeptide segments of p21 and p27 are partially folded in isolation and fold further upon binding their biological targets. Interestingly, some portions of p27 which bind to and inhibit Cdk2/cyclin A remain flexible in the bound complex. This residual flexibility allows otherwise buried tyrosine residues within p27 to be phosphorylated by nonreceptor tyrosine kinases (NRTKs). Tyrosine phosphorylation relieves kinase inhibition, triggering Cdk2-mediated phosphorylation of a threonine residue within the flexible C-terminus of p27. This, in turn, marks p27 for ubiquitination and proteasomal degradation, unleashing full Cdk2 activity which drives cell cycle progression. p27, thus, constitutes a conduit for transmission of proliferative signals via posttranslational modifications. Importantly, activation of the p27 signaling conduit by oncogenic NRTKs

  10. Optimizing the Intrinsic Signal-to-Noise Ratio of MRI Strip Detectors

    PubMed Central

    Kumar, Ananda; Bottomley, Paul A.

    2007-01-01

    An MRI detector is formed from a conducting strip separated by a dielectric substrate from a ground plane, and tuned to a quarter-wavelength. By distributing discrete tuning elements along the strip, the geometric design may be adjusted to optimize the signal-to-noise ratio (SNR) for a given application. Here a numerical electromagnetic (EM) method of moments (MoM) is applied to determine the length, width, substrate thickness, dielectric constant, and number of tuning elements that yield the best intrinsic SNR (ISNR) of the strip detector at 1.5 Tesla. The central question of how strip performance compares with that of a conventional optimized loop coil is also addressed. The numerical method is validated against the known ISNR performance of loop coils, and its ability to predict the tuning capacitances and performance of seven experimental strip detectors of varying length, width, substrate thickness, and dielectric constant. We find that strip detectors with low-dielectric constant, moderately thin-substrate, and length about 1.3 (±0.2) times the depth of interest perform best. The ISNR of strips is comparable to that of loops (i.e., higher close to the detector but lower at depth). The SNR improves with two inherently-decoupled strips, whose sensitivity profile is well-suited to parallel MRI. The findings are summarized as design “rules of thumb.” PMID:16724302

  11. A Hierarchy of Cell Intrinsic and Target-Derived Homeostatic Signaling

    PubMed Central

    Bergquist, Sharon; Dickman, Dion K.; Davis, Graeme W.

    2010-01-01

    Homeostatic control of neural function can be mediated by the regulation of ion channel expression, neurotransmitter receptor abundance, or modulation of presynaptic release. These processes can be implemented through cell autonomous or intercellular signaling. It remains unknown whether different forms of homeostatic regulation can be coordinated to achieve constant neural function. One way to approach this question is to confront a simple neural system with conflicting perturbations and determine whether the outcome reflects a coordinated, homeostatic response. Here we demonstrate that two A-type potassium channel genes, shal and shaker, are reciprocally, transcriptionally coupled to maintain A-type channel expression. We then demonstrate that this homeostatic control of A-type channel expression prevents target-dependent, homeostatic modulation of synaptic transmission. Thus, we uncover a novel homeostatic mechanism that reciprocally regulates A-type potassium channels and we define a hierarchical relationship between cell-intrinsic control of ion channel expression and target-derived homeostatic control of synaptic transmission. PMID:20434999

  12. Using DNA mechanics to predict intrinsic and extrinsic nucleosome positioning signals

    NASA Astrophysics Data System (ADS)

    Morozov, Alexandre

    2008-03-01

    In eukaryotic genomes, nucleosomes function to compact DNA and to regulate access to it both by simple physical occlusion and by providing the substrate for numerous covalent epigenetic tags. While nucleosome positions in vitro are determined by sequence alone, in vivo competition with other DNA-binding factors and action of chromatin remodeling enzymes play a role that needs to be quantified. We developed a biophysical, DNA mechanics-based model for the sequence dependence of DNA bending energies, and validated it against a collection of in vitro free energies of nucleosome formation and a nucleosome crystal structure; we also successfully designed both strong and poor histone binding sequences ab initio. For in vivo data from S.cerevisiae, the strongest positioning signal came from the competition with other factors rather than intrinsic nucleosome sequence preferences. Based on sequence alone, our model predicts that functional transcription factor binding sites tend to be covered by nucleosomes, yet are uncovered in vivo because functional sites cluster within a single nucleosome footprint and thus make transcription factors bind cooperatively. Similarly a weak enhancement of nucleosome binding in the TATA region becomes a strong depletion when the TATA-binding protein is included, in quantitative agreement with experiment. Our model distinguishes multiple ways in which genomic sequence influences nucleosome positions, and thus provides alternative explanations for several genome-wide experimental findings. In the future our approach will be used to rationally alter gene expression levels in model systems through redesign of nucleosome occupancy profiles.

  13. The sorting of proglucagon to secretory granules is mediated by carboxypeptidase E and intrinsic sorting signals.

    PubMed

    McGirr, Rebecca; Guizzetti, Leonardo; Dhanvantari, Savita

    2013-05-01

    Proglucagon is expressed in pancreatic alpha cells, intestinal L cells and brainstem neurons. Tissue-specific processing of proglucagon yields the peptide hormones glucagon in the alpha cell and glucagon-like peptide (GLP)-1 and GLP-2 in L cells. Both glucagon and GLP-1 are secreted in response to nutritional status and are critical for regulating glycaemia. The sorting of proglucagon to the dense-core secretory granules of the regulated secretory pathway is essential for the appropriate secretion of glucagon and GLP-1. We examined the roles of carboxypeptidase E (CPE), a prohormone sorting receptor, the processing enzymes PC1/3 and PC2 and putative intrinsic sorting signals in proglucagon sorting. In Neuro 2a cells that lacked CPE, PC1/3 and PC2, proglucagon co-localised with the Golgi marker p115 as determined by quantitative immunofluorescence microscopy. Expression of CPE, but not of PC1/3 or PC2, enhanced proglucagon sorting to granules. siRNA-mediated knockdown of CPE disrupted regulated secretion of glucagon from pancreatic-derived alphaTC1-6 cells, but not of GLP-1 from intestinal cell-derived GLUTag cells. Mutation of the PC cleavage site K70R71, the dibasic R17R18 site within glucagon or the alpha-helix of glucagon, all significantly affected the sub-cellular localisation of proglucagon. Protein modelling revealed that alpha helices corresponding to glucagon, GLP-1 and GLP-2, are arranged within a disordered structure, suggesting some flexibility in the sorting mechanism. We conclude that there are multiple mechanisms for sorting proglucagon to the regulated secretory pathway, including a role for CPE in pancreatic alpha cells, initial cleavage at K70R71 and multiple sorting signals.

  14. Optical Signal Processing: Poisson Image Restoration and Shearing Interferometry

    NASA Technical Reports Server (NTRS)

    Hong, Yie-Ming

    1973-01-01

    Optical signal processing can be performed in either digital or analog systems. Digital computers and coherent optical systems are discussed as they are used in optical signal processing. Topics include: image restoration; phase-object visualization; image contrast reversal; optical computation; image multiplexing; and fabrication of spatial filters. Digital optical data processing deals with restoration of images degraded by signal-dependent noise. When the input data of an image restoration system are the numbers of photoelectrons received from various areas of a photosensitive surface, the data are Poisson distributed with mean values proportional to the illuminance of the incoherently radiating object and background light. Optical signal processing using coherent optical systems is also discussed. Following a brief review of the pertinent details of Ronchi's diffraction grating interferometer, moire effect, carrier-frequency photography, and achromatic holography, two new shearing interferometers based on them are presented. Both interferometers can produce variable shear.

  15. Reconfigurable Optical Signal Processing Based on a Distributed Feedback Semiconductor Optical Amplifier.

    PubMed

    Li, Ming; Deng, Ye; Tang, Jian; Sun, Shuqian; Yao, Jianping; Azaña, José; Zhu, Ninghua

    2016-01-27

    All-optical signal processing has been considered a solution to overcome the bandwidth and speed limitations imposed by conventional electronic-based systems. Over the last few years, an impressive range of all-optical signal processors have been proposed, but few of them come with reconfigurability, a feature highly needed for practical signal processing applications. Here we propose and experimentally demonstrate an analog optical signal processor based on a phase-shifted distributed feedback semiconductor optical amplifier (DFB-SOA) and an optical filter. The proposed analog optical signal processor can be reconfigured to perform signal processing functions including ordinary differential equation solving and temporal intensity differentiation. The reconfigurability is achieved by controlling the injection currents. Our demonstration provitdes a simple and effective solution for all-optical signal processing and computing.

  16. Reconfigurable Optical Signal Processing Based on a Distributed Feedback Semiconductor Optical Amplifier

    PubMed Central

    Li, Ming; Deng, Ye; Tang, Jian; Sun, Shuqian; Yao, Jianping; Azaña, José; Zhu, Ninghua

    2016-01-01

    All-optical signal processing has been considered a solution to overcome the bandwidth and speed limitations imposed by conventional electronic-based systems. Over the last few years, an impressive range of all-optical signal processors have been proposed, but few of them come with reconfigurability, a feature highly needed for practical signal processing applications. Here we propose and experimentally demonstrate an analog optical signal processor based on a phase-shifted distributed feedback semiconductor optical amplifier (DFB-SOA) and an optical filter. The proposed analog optical signal processor can be reconfigured to perform signal processing functions including ordinary differential equation solving and temporal intensity differentiation. The reconfigurability is achieved by controlling the injection currents. Our demonstration provitdes a simple and effective solution for all-optical signal processing and computing. PMID:26813252

  17. Intrinsic magnetic field sensitivities of sensor head housing for all-fiber optic current sensors

    NASA Astrophysics Data System (ADS)

    Zhang, Xuedian; Chang, Min; Mao, Chenfei; Lu, Dunke; Kamagara, Abel

    2014-10-01

    Full-fiber optical current sensors utilize the effects of magnetic-field imposed on the change of polarization azimuth of light in the fibers. Due to the sensitivities to external perturbations, the sensing fiber head in practical applications is usually packed in a fixed metallic housing majorly for protection purposes. However, the housing material itself tends to influence the magnetic field distributions of the current carrying wire in question. In this paper, the intrinsic effect and influence of fiber sensor head housing made of different magnetic materials on the magnetic field distributions around the current-carrying wire have been investigated. Simulation and virtual experimentation was carried out in the COMSOL environment. From the results, the housings made of single magnetic material are found to have magnetic disturbances on the magnetic field distribution around the wire. Housing made of some alloy materials has no influence on the magnetic distributions outside the wire. After experimenting with several materials, the former materials inclusive, steel is preferred as the protective housing and/or casing of fiber sensor head in optical fiber current sensors. This is on the basis of both technical and non-technical consideration of low cost of material though biased toward technical aspect of little or no influence on magnetic distribution around the wire.

  18. Optical visualization of Alzheimer’s pathology via multiphoton-excited intrinsic fluorescence and second harmonic generation

    PubMed Central

    Kwan, Alex C.; Duff, Karen; Gouras, Gunnar K.; Webb, Watt W.

    2010-01-01

    Intrinsic optical emissions, such as autofluorescence and second harmonic generation (SHG), are potentially useful for functional fluorescence imaging and biomedical disease diagnosis for neurodegenerative diseases such as Alzheimer’s disease (AD). Here, using multiphoton and SHG microscopy, we identified sources of intrinsic emissions in ex vivo, acute brain slices from AD transgenic mouse models. We observed autofluorescence and SHG at senile plaques as well as characterized their emission spectra. The utility of intrinsic emissions was demonstrated by imaging senile plaque autofluorescence in conjunction with SHG from microtubule arrays to assess the polarity of microtubules near pathological lesions. Our results suggest that tissues from AD transgenic models contain distinct intrinsic emissions, which can provide valuable information about the disease mechanisms. PMID:19259208

  19. Research on small signal detection of optical voltage/current transformer

    NASA Astrophysics Data System (ADS)

    Li, Hongbo; Zhang, Guoqing; Cai, Xingguo; Guo, Zhizhong; Yu, Wenbin; Huo, Guangyu

    2013-08-01

    This paper researches the signal conditioning program of optical voltage/current transformer and the imbalance during the transmission of dual optical path, gives a brief introduction to the basic principle of optical voltage transformer based on electro-optic Pockels effect and optical current transformer based on Faraday Magnetic-optical Effect, and induces a general expression form of output light intensities This paper research on the signal modulation methods for the system: AC and DC modulations. What is more, the advantages and disadvantages of both modulations in the system will be analyzed. Considering the characteristics that the systematic noise and signal have the spectrum overlapping and that when there is any fault, the fact that in the small signal detection system the output SNR of AC modulation is better than that of DC modulation will be proved. For the parameter changes caused by the environment factors, the feedback control linked by the DSP is imported, it automatically adjusts the balance of the two branch parameters, acquires the measured component in the condition of the two branch unbalance parameters. Furthermore, this paper researches on the influence of imbalance of the dual optical path on the signal detection system. It analyzes the error characteristics due to different kinds of losses and to component matching disorders and other intrinsic factors and then put forward the method to calculate balancing factors by means of the RMS of 50Hz signal. The result proves that using this method can improve the output SNR of optical voltage/current transformer to some extent.

  20. Evaluation of intrinsic respiratory signal determination methods for 4D CBCT adapted for mice

    SciTech Connect

    Martin, Rachael; Pan, Tinsu; Rubinstein, Ashley; Court, Laurence; Ahmad, Moiz

    2015-01-15

    Purpose: 4D CT imaging in mice is important in a variety of areas including studies of lung function and tumor motion. A necessary step in 4D imaging is obtaining a respiratory signal, which can be done through an external system or intrinsically through the projection images. A number of methods have been developed that can successfully determine the respiratory signal from cone-beam projection images of humans, however only a few have been utilized in a preclinical setting and most of these rely on step-and-shoot style imaging. The purpose of this work is to assess and make adaptions of several successful methods developed for humans for an image-guided preclinical radiation therapy system. Methods: Respiratory signals were determined from the projection images of free-breathing mice scanned on the X-RAD system using four methods: the so-called Amsterdam shroud method, a method based on the phase of the Fourier transform, a pixel intensity method, and a center of mass method. The Amsterdam shroud method was modified so the sharp inspiration peaks associated with anesthetized mouse breathing could be detected. Respiratory signals were used to sort projections into phase bins and 4D images were reconstructed. Error and standard deviation in the assignment of phase bins for the four methods compared to a manual method considered to be ground truth were calculated for a range of region of interest (ROI) sizes. Qualitative comparisons were additionally made between the 4D images obtained using each of the methods and the manual method. Results: 4D images were successfully created for all mice with each of the respiratory signal extraction methods. Only minimal qualitative differences were noted between each of the methods and the manual method. The average error (and standard deviation) in phase bin assignment was 0.24 ± 0.08 (0.49 ± 0.11) phase bins for the Fourier transform method, 0.09 ± 0.03 (0.31 ± 0.08) phase bins for the modified Amsterdam shroud method, 0

  1. Role of Intrinsic Flexibility in Signal Transduction Mediated by the Cell Cycle Regulator, p27Kip1

    PubMed Central

    Galea, Charles A.; Nourse, Amanda; Wang, Yuefeng; Sivakolundu, Sivashankar G.; Heller, William T.; Kriwacki, Richard W.

    2008-01-01

    Summary p27Kip1 (p27), which controls eukaryotic cell division through interactions with cyclin-dependent kinases (Cdks), integrates and transduces pro-mitogenic signals from various non-receptor tyrosine kinases (NRTKs) by orchestrating its own phosphorylation, ubiquitination and degradation. Intrinsic flexibility allows p27 to act as a “conduit” for sequential signaling mediated by tyrosine and threonine phosphorylation and ubiquitination. While the structural features of the Cdk/cyclin-binding domain of p27 are understood, how the C-terminal regulatory domain coordinates multi-step signaling leading to p27 degradation is poorly understood. We show that the 100-residue p27 C-terminal domain is extended and flexible when p27 is bound to Cdk2/cyclin A. We propose that the intrinsic flexibility of p27 provides a molecular basis for the sequential signal transduction conduit that regulates p27 degradation and cell division. Other intrinsically unstructured proteins possessing multiple sites of post-translational modification may participate in similar signaling conduits. PMID:18177895

  2. Neuromorphic opto-electronic integrated circuits for optical signal processing

    NASA Astrophysics Data System (ADS)

    Romeira, B.; Javaloyes, J.; Balle, S.; Piro, O.; Avó, R.; Figueiredo, J. M. L.

    2014-08-01

    The ability to produce narrow optical pulses has been extensively investigated in laser systems with promising applications in photonics such as clock recovery, pulse reshaping, and recently in photonics artificial neural networks using spiking signal processing. Here, we investigate a neuromorphic opto-electronic integrated circuit (NOEIC) comprising a semiconductor laser driven by a resonant tunneling diode (RTD) photo-detector operating at telecommunication (1550 nm) wavelengths capable of excitable spiking signal generation in response to optical and electrical control signals. The RTD-NOEIC mimics biologically inspired neuronal phenomena and possesses high-speed response and potential for monolithic integration for optical signal processing applications.

  3. Discrimination of acoustic communication signals by grasshoppers (Chorthippus biguttulus): temporal resolution, temporal integration, and the impact of intrinsic noise.

    PubMed

    Ronacher, Bernhard; Wohlgemuth, Sandra; Vogel, Astrid; Krahe, Rüdiger

    2008-08-01

    A characteristic feature of hearing systems is their ability to resolve both fast and subtle amplitude modulations of acoustic signals. This applies also to grasshoppers, which for mate identification rely mainly on the characteristic temporal patterns of their communication signals. Usually the signals arriving at a receiver are contaminated by various kinds of noise. In addition to extrinsic noise, intrinsic noise caused by stochastic processes within the nervous system contributes to making signal recognition a difficult task. The authors asked to what degree intrinsic noise affects temporal resolution and, particularly, the discrimination of similar acoustic signals. This study aims at exploring the neuronal basis for sexual selection, which depends on exploiting subtle differences between basically similar signals. Applying a metric, by which the similarities of spike trains can be assessed, the authors investigated how well the communication signals of different individuals of the same species could be discriminated and correctly classified based on the responses of auditory neurons. This spike train metric yields clues to the optimal temporal resolution with which spike trains should be evaluated.

  4. Femtosecond all-optical devices for ultrafast communication and signal processing

    NASA Astrophysics Data System (ADS)

    Wada, Osamu

    2004-11-01

    Future bandwidth demand in optical communication and signal processing systems will soon exceed 100 Gb s-1 as is commonly forecasted from a throughput experience curve for communication systems. However, such systems cannot be realized without introducing ultrafast, all-optical devices, since existing optoelectronic and electronic devices and integrated circuits would not be able to function at a bit rate exceeding 100 Gb s-1, because of the speed limit intrinsic to conventional semiconductor materials and devices. All-optical devices based on completely new principles, not being restricted by properties of existing materials and device principles, must be developed for the realization of ultrafast communication and signal processing systems. This paper reviews requirements of ultrafast all-optical devices and recent progress in ultrafast light sources and all-optical switches based on either novel device principles or ultrafast phenomena in novel materials such as quantum-confined nanostructures. Recent developments described here include mode-locked lasers and a variety of all-optical switches based on different phenomena including Mach-Zehnder interferometer structures, spin relaxation, intersubband transition, and ultrafast absorption recovery in organic thin films and semiconductor quantum dots. Some of the recent developments have already shown capability of basic functions such as ultrafast pulse generation and signal processing at the bit rate of 500 Gb s-1 to 1 Tb s-1. Technical challenges expected for the future are discussed in view of their applications in real systems.

  5. Altered Functional Connectivity Following an Inflammatory White Matter Injury in the Newborn Rat: A High Spatial and Temporal Resolution Intrinsic Optical Imaging Study.

    PubMed

    Guevara, Edgar; Pierre, Wyston C; Tessier, Camille; Akakpo, Luis; Londono, Irène; Lesage, Frédéric; Lodygensky, Gregory A

    2017-01-01

    Very preterm newborns have an increased risk of developing an inflammatory cerebral white matter injury that may lead to severe neuro-cognitive impairment. In this study we performed functional connectivity (fc) analysis using resting-state optical imaging of intrinsic signals (rs-OIS) to assess the impact of inflammation on resting-state networks (RSN) in a pre-clinical model of perinatal inflammatory brain injury. Lipopolysaccharide (LPS) or saline injections were administered in postnatal day (P3) rat pups and optical imaging of intrinsic signals were obtained 3 weeks later. (rs-OIS) fc seed-based analysis including spatial extent were performed. A support vector machine (SVM) was then used to classify rat pups in two categories using fc measures and an artificial neural network (ANN) was implemented to predict lesion size from those same fc measures. A significant decrease in the spatial extent of fc statistical maps was observed in the injured group, across contrasts and seeds ((*)p = 0.0452 for HbO2 and (**)p = 0.0036 for HbR). Both machine learning techniques were applied successfully, yielding 92% accuracy in group classification and a significant correlation r = 0.9431 in fractional lesion volume prediction ((**)p = 0.0020). Our results suggest that fc is altered in the injured newborn brain, showing the long-standing effect of inflammation.

  6. An Intrinsic Fiber-Optic Sensor for Structure Lightning Current Measurement

    NASA Technical Reports Server (NTRS)

    Nguyen, Truong X.; Ely, Jay J.; Szatkowski, George N.; Mata, Carlos T.; Mata, Angel. G.; Snyder, Gary P.

    2014-01-01

    An intrinsic optical-fiber sensor based on Faraday Effect is developed that is highly suitable for measuring lightning current on aircraft, towers and complex structures. Originally developed specifically for aircraft installations, it is light-weight, non-conducting, structure conforming, and is immune to electromagnetic interference, hysteresis and saturation. It can measure total current down to DC. When used on lightning towers, the sensor can help validate other sensors and lightning detection network measurements. Faraday Effect causes light polarization to rotate when the fiber is exposed to a magnetic field in the direction of light propagation. Thus, the magnetic field strength can be determined from the light polarization change. By forming closed fiber loops and applying Ampere's law, measuring the total light rotation yields the total current enclosed. A broadband, dual-detector, reflective polarimetric scheme allows measurement of both DC component and AC waveforms with a 60 dB dynamic range. Two systems were built that are similar in design but with slightly different sensitivities. The 1310nm laser system can measure 300 A - 300 kA, and has a 15m long sensing fiber. It was used in laboratory testing, including measuring current on an aluminum structure simulating an aircraft fuselage or a lightning tower. High current capabilities were demonstrated up to 200 kA at a lightning test facility. The 1550nm laser system can measure 400 A - 400 kA and has a 25m fiber length. Used in field measurements, excellent results were achieved in the summer of 2012 measuring rocket-triggered lightning at the International Center for Lightning Research and Testing (ICLRT), Camp Blanding, Florida. In both systems increased sensitivity can be achieved with multiple fiber loops. The fiber optic sensor provides many unique capabilities not currently possible with traditional sensors. It represents an important new tool for lightning current measurement where low weight

  7. Manifestation of intrinsic defects in optical properties of self-organized opal photonic crystals

    PubMed

    Vlasov; Astratov; Baryshev; Kaplyanskii; Karimov; Limonov

    2000-05-01

    Self-organized synthetic opals possessing a face centered cubic (fcc) lattice are promising for fabrication of a three-dimensional photonic crystal with a full photonic band gap in the visible. The fundamental limiting factor of this method is the large concentration of lattice defects and, especially, planar stacking faults, which are intrinsic to self-assembling growth of colloidal crystal. We have studied the influence of various types of defects on photonic band structure of synthetic opals by means of optical transmission, reflection and diffraction along different crystallographic directions. We found that in carefully chosen samples the stacking probability alpha can be as high as 0.8-0.9 revealing the strong preference of fcc packing sequence over the hexagonal close-packed (hcp). It is shown that scattering on plane stacking faults located perpendicular to the direction of growth results in a strong anisotropy of diffraction pattern as well as in appearance of a pronounced doublet structure in transmission and reflection spectra taken from the directions other than the direction of growth. This doublet is a direct manifestation of the coexistence of two crystallographic phases--pure fcc and strongly faulted. As a result the inhomogeneously broadened stop-bands overlap over a considerable amount of phase space. The latter, however, does not mean the depletion of the photonic density of states since large disordering results in filling of the partial gaps with both localized and extended states.

  8. Intrinsic Optical Activity and Environmental Perturbations: Solvation Effects in Chiral Building Blocks

    NASA Astrophysics Data System (ADS)

    Lemler, Paul M.; Vaccaro, Patrick

    2016-06-01

    The non-resonant interaction of electromagnetic radiation with an isotropic ensemble of chiral molecules, which causes the incident state of linear polarization to undergo a signed rotation, long has served as a metric for gauging the enantiomeric purity of asymmetric syntheses. While the underlying phenomenon of circular birefringence (CB) typically is probed in the condensed phase, recent advances in ultrasensitive circular-differential detection schemes, as exemplified by the techniques of Cavity Ring-Down Polarimetry (CRDP), have permitted the first quantitative analyses of such processes to be performed in rarefied media. Efforts to extend vapor-phase investigations of CB to new families of chiral substrates will be discussed, with particular emphasis directed towards the elucidation of intrinsic (e.g., solvent-free) properties and their mediation by environmental perturbations (e.g., solvation). Specific species targeted by this work will include the stereoselective building blocks phenylpropylene oxide and α-methylbenzyl amine, both of which exhibit pronounced solvent-dependent changes in measured optical activity. The nature of chiroptical response in different environments will be highlighted, with quantum-chemical calculations serving to unravel the structural and electronic provenance of observed behavior.

  9. Advances in white-light optical signal processing

    NASA Technical Reports Server (NTRS)

    Yu, F. T. S.

    1984-01-01

    A technique that permits signal processing operations which can be carried out by white light source is described. The method performs signal processing that obeys the concept of coherent light rather than incoherent optics. Since the white light source contains all the color wavelengths of the visible light, the technique is very suitable for color signal processing.

  10. Transmission of RF Signals Over Optical Fiber for Avionics Applications

    NASA Technical Reports Server (NTRS)

    Slaveski, Filip; Sluss, James, Jr.; Atiquzzaman, Mohammed; Hung, Nguyen; Ngo, Duc

    2002-01-01

    During flight, aircraft avionics transmit and receive RF signals to/from antennas over coaxial cables. As the density and complexity of onboard avionics increases, the electromagnetic interference (EM) environment degrades proportionately, leading to decreasing signal-to-noise ratios (SNRs) and potential safety concerns. The coaxial cables are inherently lossy, limiting the RF signal bandwidth while adding considerable weight. To overcome these limitations, we have investigated a fiber optic communications link for aircraft that utilizes wavelength division multiplexing (WDM) to support the simultaneous transmission of multiple signals (including RF) over a single optical fiber. Optical fiber has many advantages over coaxial cable, particularly lower loss, greater bandwidth, and immunity to EM. In this paper, we demonstrate that WDM can be successfully used to transmit multiple RF signals over a single optical fiber with no appreciable signal degradation. We investigate the transmission of FM and AM analog modulated signals, as well as FSK digital modulated signals, over a fiber optic link (FOL) employing WDM. We present measurements of power loss, delay, SNR, carrier-to-noise ratio (CNR), total harmonic distortion (THD), and bit error rate (BER). Our experimental results indicate that WDM is a fiber optic technology suitable for avionics applications.

  11. Nonlinear Real-Time Optical Signal Processing

    DTIC Science & Technology

    1990-09-01

    pattern recognition. Additional work concerns the relationship of parallel computation paradigms to optical computing and halftone screen techniques...paradigms to optical computing and halftone screen techniques for implementing general nonlinear functions. 3\\ 2 Research Progress This section...Vol. 23, No. 8, pp. 34-57, 1986. 2.4 Nonlinear Optical Processing with Halftones : Degradation and Compen- sation Models This paper is concerned with

  12. Integrated Optic Signal Processors for Wideband Radar Systems.

    DTIC Science & Technology

    1980-05-01

    tion of AO signal processors using integrated optic techniques constitutes one of the most important on-going R and D activities.(1 2 14) The major...Bragg Deflectors and Applications," Invited Papaer, Pro- ceedings of the Society of Photo- Optical Instrumentation Engineers, 90, Acousto - Optics , pp. 69...C S TSAI DASG 6-C-0 2 UNCLASSIFIED 14L JEW EhEmhmhmhEE -Eu----.om 3~6 It1L25 I 1.4~IN . MICROCOPY RI SOtUlION ILSI CHARI INTEGRATED OPTIC SIGNAL

  13. System and Method for Multi-Wavelength Optical Signal Detection

    NASA Technical Reports Server (NTRS)

    McGlone, Thomas D. (Inventor)

    2017-01-01

    The system and method for multi-wavelength optical signal detection enables the detection of optical signal levels significantly below those processed at the discrete circuit level by the use of mixed-signal processing methods implemented with integrated circuit technologies. The present invention is configured to detect and process small signals, which enables the reduction of the optical power required to stimulate detection networks, and lowers the required laser power to make specific measurements. The present invention provides an adaptation of active pixel networks combined with mixed-signal processing methods to provide an integer representation of the received signal as an output. The present invention also provides multi-wavelength laser detection circuits for use in various systems, such as a differential absorption light detection and ranging system.

  14. Optical frequency upconversion technique for transmission of wireless MIMO-type signals over optical fiber.

    PubMed

    Shaddad, R Q; Mohammad, A B; Al-Gailani, S A; Al-Hetar, A M

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength.

  15. Optical Frequency Upconversion Technique for Transmission of Wireless MIMO-Type Signals over Optical Fiber

    PubMed Central

    Shaddad, R. Q.; Mohammad, A. B.; Al-Gailani, S. A.; Al-Hetar, A. M.

    2014-01-01

    The optical fiber is well adapted to pass multiple wireless signals having different carrier frequencies by using radio-over-fiber (ROF) technique. However, multiple wireless signals which have the same carrier frequency cannot propagate over a single optical fiber, such as wireless multi-input multi-output (MIMO) signals feeding multiple antennas in the fiber wireless (FiWi) system. A novel optical frequency upconversion (OFU) technique is proposed to solve this problem. In this paper, the novel OFU approach is used to transmit three wireless MIMO signals over a 20 km standard single mode fiber (SMF). The OFU technique exploits one optical source to produce multiple wavelengths by delivering it to a LiNbO3 external optical modulator. The wireless MIMO signals are then modulated by LiNbO3 optical intensity modulators separately using the generated optical carriers from the OFU process. These modulators use the optical single-sideband with carrier (OSSB+C) modulation scheme to optimize the system performance against the fiber dispersion effect. Each wireless MIMO signal is with a 2.4 GHz or 5 GHz carrier frequency, 1 Gb/s data rate, and 16-quadrature amplitude modulation (QAM). The crosstalk between the wireless MIMO signals is highly suppressed, since each wireless MIMO signal is carried on a specific optical wavelength. PMID:24772009

  16. Adaptive adjustment of reference constellation for demodulating 16QAM signal with intrinsic distortion due to imperfect modulation.

    PubMed

    Inoue, Takashi; Namiki, Shu

    2013-12-02

    We find that an adaptive equalizer and a phase-locked loop operating with decision-directed mode exhibit degraded performances when they are used in a digital coherent receiver to demodulate a 16QAM signal with intrinsically distorted constellation, and that the degradation is more significant for the dual-polarization case. We then propose a scheme to correctly demodulate such a distorted 16QAM signal, where the reference constellation and the threshold for the decision are adaptively adjusted such that they fit to the distorted ones. We experimentally confirm the improved performance of the proposed scheme over the conventional one for single-and dual-polarization 16QAM signals with distortion. We also investigate the applicable range of the proposed scheme for the degree of distortion of the signal.

  17. Growth of Third-Harmonic Signal in Optical Glass Fibre

    DTIC Science & Technology

    1990-01-01

    harmonic signal In optical glass fibres , illuminated vith 10kV peak pover pulses from A NdYAG lasers has been observed. Broadband fluores.enc from the third...J’T. Al-0002 GROWTH OF THIFRO-HARMVONIC SIGNAL IN OPTICAL GLASS FIORE Irdexim tems 0,rkl f. N motwvij p~ .G For mo i fibres the Sit signal strtd g0r...Amorphous nature of glass ) but with time, as the fibre is illuminated with inltense laser light at 4 w1O6pm, the S1t signal 3rows. What is believed to

  18. A tale of two carenes: intrinsic optical activity and large-amplitude nuclear displacement.

    PubMed

    Lahiri, Priyanka; Wiberg, Kenneth B; Vaccaro, Patrick H

    2012-09-27

    The specific rotation for two isomeric members of the terpene family, (S)-(+)-2-carene and (S)-(+)-3-carene, has been investigated under complementary solvated and isolated conditions, where the latter vapor-phase work has been performed at excitation wavelengths of 355 and 633 nm by means of ultrasensitive cavity ring-down polarimetry (CRDP). Linear-response computations of dispersive optical activity built upon analogous density-functional (B3LYP/aug-cc-pVTZ) and coupled-cluster (CCSD/aug-cc-pVDZ) levels of theory have been enlisted to unravel the structural and electronic origins of observed behavior. The six-membered portion of the bicyclic skeleton in the nominally rigid 3-carene system is predicted to be near-planar in nature, with calculated and measured rotatory powers for the isolated (gas-phase) species shown to be in excellent agreement. In contrast, the inherent flexibility of 2-carene gives rise to two quasidegenerate conformations that are interconnected by a large-amplitude ring-puckering motion and exhibit antagonistic chiroptical properties. Various approaches to simulate the intrinsic response evoked from a thermally equilibrated ensemble of gaseous (S)-(+)-2-carene molecules have been considered, including implicit averaging over independent conformers and explicit (albeit restricted) averaging over nuclear degrees of freedom. A polarizable continuum model for implicit solvation was found to describe solvent-dependent trends reasonably well in the case of (S)-(+)-2-carene, but failed to reproduce the specific-rotation patterns emerging from polarimetric studies of (S)-(+)-3-carene.

  19. Optical signal processing - Fourier transforms and convolution/correlation

    NASA Astrophysics Data System (ADS)

    Rhodes, William T.

    The application of Fourier techniques and linear-systems theory to the analysis and synthesis of optical systems is described in a theoretical review, and Fourier-based optical signal-processing methods are considered. Topics examined include monochromatic wave fields and their phasor representation, wave propagation, Fourier-transform and spectrum analysis with a spherical lens, coherent and incoherent imaging and spatial filtering, and a channelized spectrum analyzer (using both spherical and cylindrical lenses) for multiple one-dimensional input signals.

  20. Selection of the intrinsic polarization properties of animal optical materials creates enhanced structural reflectivity and camouflage

    PubMed Central

    Feller, Kathryn D.; Jordan, Thomas M.

    2017-01-01

    Many animals use structural coloration to create bright and conspicuous visual signals. Selection of the size and shape of the optical structures animals use defines both the colour and intensity of the light reflected. The material used to create these reflectors is also important; however, animals are restricted to a limited number of materials: commonly chitin, guanine and the protein, reflectin. In this work we highlight that a particular set of material properties can also be under selection in order to increase the optical functionality of structural reflectors. Specifically, polarization properties, such as birefringence (the difference between the refractive indices of a material) and chirality (which relates to molecular asymmetry) are both under selection to create enhanced structural reflectivity. We demonstrate that the structural coloration of the gold beetle Chrysina resplendens and silvery reflective sides of the Atlantic herring, Clupea harengus are two examples of this phenomenon. Importantly, these polarization properties are not selected to control the polarization of the reflected light as a source of visual information per se. Instead, by creating higher levels of reflectivity than are otherwise possible, such internal polarization properties improve intensity-matching camouflage. This article is part of the themed issue ‘Animal coloration: production, perception, function and application’. PMID:28533453

  1. System and method for linearly amplifying optical analog signals by backward Raman scattering

    DOEpatents

    Lin, Cheng-Heui

    1988-07-05

    A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

  2. System and method for linearly amplifying optical analog signals by backward Raman scattering

    DOEpatents

    Lin, Cheng-Heui

    1988-01-01

    A system for linearly amplifying an optical analog signal by backward stimulated Raman scattering comprises a laser source for generating a pump pulse; and an optic fiber having two opposed apertures, a first aperture for receiving the pump pulse and a second aperture for receiving the optical analog signal, wherein the optical analog signal is linearly amplified to an amplified optical analog signal.

  3. Targeted Labeling of Neurons in a Specific Functional Micro-domain of the Neocortex by Combining Intrinsic Signal and Two-photon Imaging

    PubMed Central

    O'Herron, Philip; Shen, Zhiming; Lu, Zhongyang; Schramm, Adrien E.; Levy, Manuel; Kara, Prakash

    2012-01-01

    In the primary visual cortex of non-rodent mammals, neurons are clustered according to their preference for stimulus features such as orientation1-4, direction5-7, ocular dominance8,9 and binocular disparity9. Orientation selectivity is the most widely studied feature and a continuous map with a quasi-periodic layout for preferred orientation is present across the entire primary visual cortex10,11. Integrating the synaptic, cellular and network contributions that lead to stimulus selective responses in these functional maps requires the hybridization of imaging techniques that span sub-micron to millimeter spatial scales. With conventional intrinsic signal optical imaging, the overall layout of functional maps across the entire surface of the visual cortex can be determined12. The development of in vivo two-photon microscopy using calcium sensitive dyes enables one to determine the synaptic input arriving at individual dendritic spines13 or record activity simultaneously from hundreds of individual neuronal cell bodies6,14. Consequently, combining intrinsic signal imaging with the sub-micron spatial resolution of two-photon microscopy offers the possibility of determining exactly which dendritic segments and cells contribute to the micro-domain of any functional map in the neocortex. Here we demonstrate a high-yield method for rapidly obtaining a cortical orientation map and targeting a specific micro-domain in this functional map for labeling neurons with fluorescent dyes in a non-rodent mammal. With the same microscope used for two-photon imaging, we first generate an orientation map using intrinsic signal optical imaging. Then we show how to target a micro-domain of interest using a micropipette loaded with dye to either label a population of neuronal cell bodies or label a single neuron such that dendrites, spines and axons are visible in vivo. Our refinements over previous methods facilitate an examination of neuronal structure-function relationships with sub

  4. Why optics students should take digital signal processing courses and why digital signal processing students should take optics courses

    NASA Astrophysics Data System (ADS)

    Cathey, W. Thomas, Jr.

    2000-06-01

    This paper is based on the claim that future major contributions in the field of imaging systems will be made by those who have a background in both optics and digital signal processing. As the introduction of Fourier transforms and linear systems theory to optics had a major impact on the design of hybrid optical/digital imaging systems, the introduction of digital signal processing into optics programs will have a major impact. Examples are given of new hybrid imaging systems that have unique performance. By jointly designing the optics and the signal processing in a digital camera, a new paradigm arises where aberration balancing takes into consideration not only the number of surfaces and indices of refraction, but also the processing capability.

  5. Optical logic and signal processing using a semiconductor laser diode-based optical bistability device

    NASA Astrophysics Data System (ADS)

    Zhang, Yuancheng; Song, Qian; He, Shaowei

    1995-02-01

    Using an optical fibre-coupled semiconductor laser diode OBD with output feedback pumping operation in 5 modes (differential gain, bistability, zero-bias, inverted differential gain, and inverted bistability) has been realized respectively, and 5 elementary optical logic functions (AND, OR, NOT, NAND, and NOR) and some optical signal processing such as limiting, reshaping, and triggering have been implemented.

  6. Concentric core optical fiber with multiple-mode signal transmission

    DOEpatents

    Muhs, J.D.

    1997-05-06

    A concentric core optical fiber provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single-mode or multimode inner optical fiber defined by a core and a cladding of a lower index of refraction than the core and an outer optical fiber defined by additional cladding concentrically disposed around the cladding and of an index of refraction lower than the first mentioned cladding whereby the latter functions as the core of the outer optical fiber. By employing such an optical fiber construction with a single-mode inner core or optical fiber, highly sensitive interferometric and stable less sensitive amplitude based sensors can be placed along the same length of a concentric core optical fiber. Also, by employing the concentric core optical fiber secure telecommunications can be achieved via the inner optical fiber since an intrusion of the concentric optical fiber will first cause a variation in the light being transmitted through the outer optical fiber and this variation of light being used to trigger a suitable alarm indicative of the intrusion. 3 figs.

  7. Concentric core optical fiber with multiple-mode signal transmission

    DOEpatents

    Muhs, Jeffrey D.

    1997-01-01

    A concentric core optical fiber provides for the simultaneous but independent transmission of signals over a single optical fiber. The concentric optical fiber is constructed of a single-mode or multimode inner optical fiber defined by a core and a cladding of a lower index of refraction than the core and an outer optical fiber defined by additional cladding concentrically disposed around the cladding and of an index of refraction lower than the first mentioned cladding whereby the latter functions as the core of the outer optical fiber. By employing such an optical fiber construction with a single-mode inner core or optical fiber, highly sensitive interferometric and stable less sensitive amplitude based sensors can be placed along the same length of a concentric core optical fiber. Also, by employing the concentric core optical fiber secure telecommunications can be achieved via the inner optical fiber since an intrusion of the concentric optical fiber will first cause a variation in the light being transmitted through the outer optical fiber and this variation of light being used to trigger a suitable alarm indicative of the intrusion.

  8. Industrial Applications Of Optical Signal Processing I

    NASA Astrophysics Data System (ADS)

    Javidi, Bahram

    1988-04-01

    Optical technology has emerged as a viable solution to the growing demand to increase the throughput of high speed processors and computers. Although higher speed and denser integrated circuits are being developed, it appears that faster switching speeds in digital circuits will not provide an adequate solution to the bottleneck problem of computing systems for such tasks as real-time distortion-invariant pattern recognition and associative memory. Even supercomputers using new computing architectures and subnanosecond gate delays do not have sufficient speed for such real-time operations. Optical systems offer the advantages of inherent parallelism and high speed with superior interconnection capability, which allow for the processing of millions of simultaneous operations. The lack of electromagnetic interference in optics is ideally suited for neural network based proces-sors, which require a high degree of interconnectivity and global communications properties. Analog optical computers are particularly attractive for the processing of large stochastic data, while the more precise digital computers break down when confronted with such random problems. The immunity to electromagnetic interference can also be used advantageously in VLSI interconnections technology and board-to-board communications to reduce the pinout problem and to improve flexibility and performance. For these reasons, optical technology has become a major research and development effort at many industrial, government, and university laboratories both nationally and internationally.

  9. Nonlinear optical polymers for electro-optic signal processing

    NASA Technical Reports Server (NTRS)

    Lindsay, Geoffrey A.

    1991-01-01

    Photonics is an emerging technology, slated for rapid growth in communications systems, sensors, imagers, and computers. Its growth is driven by the need for speed, reliability, and low cost. New nonlinear polymeric materials will be a key technology in the new wave of photonics devices. Electron-conjubated polymeric materials offer large electro-optic figures of merit, ease of processing into films and fibers, ruggedness, low cost, and a plethora of design options. Several new broad classes of second-order nonlinear optical polymers were developed at the Navy's Michelson Laboratory at China Lake, California. Polar alignment in thin film waveguides was achieved by electric-field poling and Langmuir-Blodgett processing. Our polymers have high softening temperatures and good aging properties. While most of the films can be photobleached with ultraviolet (UV) light, some have excellent stability in the 500-1600 nm range, and UV stability in the 290-310 nm range. The optical nonlinear response of these polymers is subpicosecond. Electro-optic switches, frequency doublers, light modulators, and optical data storage media are some of the device applications anticipated for these polymers.

  10. Optical signal acquisition and processing in future accelerator diagnostics

    SciTech Connect

    Jackson, G.P. ); Elliott, A. )

    1992-01-01

    Beam detectors such as striplines and wall current monitors rely on matched electrical networks to transmit and process beam information. Frequency bandwidth, noise immunity, reflections, and signal to noise ratio are considerations that require compromises limiting the quality of the measurement. Recent advances in fiber optics related technologies have made it possible to acquire and process beam signals in the optical domain. This paper describes recent developments in the application of these technologies to accelerator beam diagnostics. The design and construction of an optical notch filter used for a stochastic cooling system is used as an example. Conceptual ideas for future beam detectors are also presented.

  11. Optical signal acquisition and processing in future accelerator diagnostics

    SciTech Connect

    Jackson, G.P.; Elliott, A.

    1992-12-31

    Beam detectors such as striplines and wall current monitors rely on matched electrical networks to transmit and process beam information. Frequency bandwidth, noise immunity, reflections, and signal to noise ratio are considerations that require compromises limiting the quality of the measurement. Recent advances in fiber optics related technologies have made it possible to acquire and process beam signals in the optical domain. This paper describes recent developments in the application of these technologies to accelerator beam diagnostics. The design and construction of an optical notch filter used for a stochastic cooling system is used as an example. Conceptual ideas for future beam detectors are also presented.

  12. An in-plane magnetic chiral dichroism approach for measurement of intrinsic magnetic signals using transmitted electrons.

    PubMed

    Song, Dongsheng; Tavabi, Amir H; Li, Zi-An; Kovács, András; Rusz, Ján; Huang, Wenting; Richter, Gunther; Dunin-Borkowski, Rafal E; Zhu, Jing

    2017-05-15

    Electron energy-loss magnetic chiral dichroism is a powerful technique that allows the local magnetic properties of materials to be measured quantitatively with close-to-atomic spatial resolution and element specificity in the transmission electron microscope. Until now, the technique has been restricted to measurements of the magnetic circular dichroism signal in the electron beam direction. However, the intrinsic magnetization directions of thin samples are often oriented in the specimen plane, especially when they are examined in magnetic-field-free conditions in the transmission electron microscope. Here, we introduce an approach that allows in-plane magnetic signals to be measured using electron magnetic chiral dichroism by selecting a specific diffraction geometry. We compare experimental results recorded from a cobalt nanoplate with simulations to demonstrate that an electron magnetic chiral dichroism signal originating from in-plane magnetization can be detected successfully.

  13. An in-plane magnetic chiral dichroism approach for measurement of intrinsic magnetic signals using transmitted electrons

    PubMed Central

    Song, Dongsheng; Tavabi, Amir H.; Li, Zi-An; Kovács, András; Rusz, Ján; Huang, Wenting; Richter, Gunther; Dunin-Borkowski, Rafal E.; Zhu, Jing

    2017-01-01

    Electron energy-loss magnetic chiral dichroism is a powerful technique that allows the local magnetic properties of materials to be measured quantitatively with close-to-atomic spatial resolution and element specificity in the transmission electron microscope. Until now, the technique has been restricted to measurements of the magnetic circular dichroism signal in the electron beam direction. However, the intrinsic magnetization directions of thin samples are often oriented in the specimen plane, especially when they are examined in magnetic-field-free conditions in the transmission electron microscope. Here, we introduce an approach that allows in-plane magnetic signals to be measured using electron magnetic chiral dichroism by selecting a specific diffraction geometry. We compare experimental results recorded from a cobalt nanoplate with simulations to demonstrate that an electron magnetic chiral dichroism signal originating from in-plane magnetization can be detected successfully. PMID:28504267

  14. Reconfigurable high-speed optical signal processing and high-capacity optical transmitter

    NASA Astrophysics Data System (ADS)

    Chitgarha, Mohammad Reza

    The field of optics and photonics enables several technologies including communication, bioimaging, spectroscopy, Ladars, microwave photonics and data processing [1-139]. The ability to use and manipulate large amounts of data is transforming many vital areas of society. The high capacity that optics brought to communications might also bring advantages to increase performance in signal processing by using a novel all-optical implementation of a tapped-delay-line, a fundamental building block for digital signal processing. This all-optical alternative provides real-time processing of amplitude- and phase-encoded optical fields, such that the overall potential speed-up is 10-100 fold faster than individual electronic processors with 5 GHz clock speeds. It can also enhance the optical data generation and transmission techniques by using different optical nonlinear processes to achieve higher baud rate data with more complex modulation format. Here, we demonstrate a reconfigurable high- speed optical tapped-delay-line, enabling several fundamental real-time signal processing functions such as equalization, correlation and discrete Fourier transform. Using nonlinear optics and dispersive elements, continuous tunability in time, amplitude and phase of the tapped-delay-line can be achieved at high speed. We also demonstrate a reconfigurable optical generation of higher-order modulation formats including pulse-amplitude-modulation (PAM) signals and quadrature-amplitude-modulation (QAM) signals [140-195].

  15. Sampling impairments influence over stealthy fiber-optic signal decryption

    NASA Astrophysics Data System (ADS)

    Yeminy, Tomer; Sadot, Dan; Zalevsky, Zeev

    2013-03-01

    Recently we have proposed a method for temporal and spectral stealthy fiber-optic communications. In this technique the signal is spread in the time domain below the noise level and the power spectral density of the signal is spread beneath the noise level in the frequency domain. The power spectral density of the signal is reconstructed by means of sampling which results in coherent addition of the encrypted signal spectral replicas. Hence, the sampling quality plays a major role in the ability to successfully decrypt the received covert signal. In this paper, we mathematically and numerically analyze the effect of sampling impairments over the decryption performance.

  16. Nonlinear real-time optical signal processing

    NASA Astrophysics Data System (ADS)

    Sawchuk, A. A.; Jenkins, B. J.

    1986-07-01

    During the period 1 July 1984 - 30 June 1985, the research under Grant AFOSR-84-0181 has concentrated on four major areas. First, work has continued on an experimental sequential optical binary parallel architecture that is constructed from an array of binary optical switching elements (NOR gates) with interconnections done by a computer-generated hologram. We are examining new binary array SLM's, high efficiency, high space-bandwidth product (SBWP) interconnection holograms, and compact reflection versions of the general architecture with the intent of building a larger demonstration system with great capabilities. Next, we have studied improved methods of providing the interconnections in these systems by the use of hybrid digital/analog (facet) holograms. We have examined analytical techniques for mapping circuit diagrams into gate locations and hologram arrays, and optimization procedures to determine the minimum set of necessary space-invariant basis functions and minimum set of space-variant indexing holograms. Another area of study has been the evaluation of devices and materials for high speed optical switching and bistability. Switching energies of 1 to 10 pJ and response times of 10 ns have been experimentally demonstrated at the University of Arizona for devices consisting of an array of Fabry-Perot cavities filled with a nonlinear material. We have begun to use the specifications of these devices and other high speed switching technologies in order to determine better designs and fundamental limits of the binary optical computing architectures under consideration.

  17. Method for enhancing signals transmitted over optical fibers

    DOEpatents

    Ogle, James W.; Lyons, Peter B.

    1983-01-01

    A method for spectral equalization of high frequency spectrally broadband signals transmitted through an optical fiber. The broadband signal input is first dispersed by a grating. Narrow spectral components are collected into an array of equalizing fibers. The fibers serve as optical delay lines compensating for material dispersion of each spectral component during transmission. The relative lengths of the individual equalizing fibers are selected to compensate for such prior dispersion. The output of the equalizing fibers couple the spectrally equalized light onto a suitable detector for subsequent electronic processing of the enhanced broadband signal.

  18. Method for enhancing signals transmitted over optical fibers

    DOEpatents

    Ogle, J.W.; Lyons, P.B.

    1981-02-11

    A method for spectral equalization of high frequency spectrally broadband signals transmitted through an optical fiber is disclosed. The broadband signal input is first dispersed by a grating. Narrow spectral components are collected into an array of equalizing fibers. The fibers serve as optical delay lines compensating for material dispersion of each spectral component during transmission. The relative lengths of the individual equalizing fibers are selected to compensate for such prior dispersion. The output of the equalizing fibers couple the spectrally equalized light onto a suitable detector for subsequent electronic processing of the enhanced broadband signal.

  19. Nonlinear fiber applications for ultrafast all-optical signal processing

    NASA Astrophysics Data System (ADS)

    Kravtsov, Konstantin

    In the present dissertation different aspects of all-optical signal processing, enabled by the use of nonlinear fibers, are studied. In particular, we focus on applications of a novel heavily GeO2-doped (HD) nonlinear fiber, that appears to be superior to many other types of nonlinear fibers because of its high nonlinearity and suitability for the use in nonlinear optical loop mirrors (NOLMs). Different functions, such as all-optical switching, thresholding, and wavelength conversion, are demonstrated with the HD fibers in the NOLM configuration. These basic functions are later used for realization of ultrafast time-domain demultiplexers, clock recovery, detectors of short pulses in stealth communications, and primitive elements for analog computations. Another important technology that benefits from the use of nonlinear fiber-based signal processing is optical code-division multiple access (CDMA). It is shown in both theory and experiment that all-optical thresholding is a unique way of improving existing detection methods for optical CDMA. Also, it is the way of implementation of true asynchronous optical spread-spectrum networks, which allows full realization of optical CDMA potential. Some aspects of quantum signal processing and manipulation of quantum states are also studied in this work. It is shown that propagation and collisions of Thirring solitons lead to a substantial squeezing of quantum states, which may find applications for generation of squeezed light.

  20. Ultrasound imaging using all-optical power and signal transfer in catheters (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Pekar, Martin; van der Mark, Martin B.

    2017-02-01

    Smart medical catheters face a connectivity challenge. An example is found in ultrasound imaging where the supply of power at the distal end and the signal transmission requires many thin and fragile wires in order to keep the catheter thin and flexible and this leads to a relatively high cost of production. We have built a fully functional benchtop demonstrator that is immediately scalable to catheter dimensions, in which all electrical wires are replaced by just two optical fibers. We show signal transfer of synthetic aperture ultrasound images as well as photovoltaic conversion to supply all electronics. The absence of conductors provides excellent galvanic isolation as well as RF and MRI compatibility and the simple design utilizing off the shelf components holds a promise of cost effectiveness all of which may help translation of these advanced devices into the clinic. We show photovoltaic conversion of 405 nm light to 45 V and 1.8 V by two blue LEDs as well as 200 MHz broad-band signal transfer using modulated 850 nm VCSEL light. Synthetic aperture ultrasound images are acquired at a frequency of 12 MHz with a collapse-mode capacitive-micromachined ultrasonic transducer. Bandwidth, noise level and dynamic range are nearly identical as shown in comparison of the images acquired with the optical link and its electrical equivalent. In conclusion, we have successfully demonstrated low-cost and scalable optical signal and power transmission for an ultrasound imaging system enjoying intrinsic RF / MRI compatibility and galvanic isolation.

  1. Region-specific regulation of voltage-gated intrinsic currents in the developing optic tectum of the Xenopus tadpole.

    PubMed

    Hamodi, Ali S; Pratt, Kara G

    2014-10-01

    Across the rostrocaudal (RC) axis of the Xenopus tadpole optic tectum exists a developmental gradient. This gradient has served as a useful model to study many aspects of synapse and dendrite maturation. To compliment these studies, we characterized how the intrinsic excitability, the ease in which a neuron can fire action potentials, might also be changing across the same axis. Whole-cell recordings from tectal neurons at different points along the RC axis revealed a graded increase in intrinsic excitability: compared with neurons at the caudal end of the tectum, neurons at the rostral end fired more action potentials in response to current injection and expressed greater peak Na⁺ and K⁺ currents, the major intrinsic currents in these neurons that underlie the action potential. We also observed, along the same axis and in the same direction, a previously described increase in the amount of synaptic drive received by individual neurons (Wu GY, Malinow R, Cline HT. Science 274: 972-976, 1996). Thus as synaptic activity ramps up across the RC axis, so does intrinsic excitability. The reduction of overall circuit activity induced a compensatory scaling up of peak Na⁺ and K⁺ currents only in the caudal portion of the tectum, suggesting a region-specific, compensatory form of plasticity.

  2. Clock recovery from 40 Gbps optical signal with optical phase-locked loop based on a terahertz optical asymmetric demultiplexer

    NASA Astrophysics Data System (ADS)

    Jhon, Young Min; Ki, Ho Jin; Kim, Sun Ho

    2003-05-01

    10 GHz clock recovery from 40 Gbps optical time-division-multiplexed (OTDM) signal pulses is experimentally demonstrated using optical phase lock loop based on a terahertz optical asymmetric demultiplexer (TOAD) with a local-reference-oscillator-free electronic feedback circuit. The clock pulse that was used as the control pulse had energy of 800 fJ and the SNR of the time-extracted 10 GHz RF signal to the side components was larger than 40 dB.

  3. Striatal intrinsic reinforcement signals during recognition memory: relationship to response bias and dysregulation in schizophrenia.

    PubMed

    Wolf, Daniel H; Gerraty, Raphaelt; Satterthwaite, Theodore D; Loughead, James; Campellone, Timothy; Elliott, Mark A; Turetsky, Bruce I; Gur, Ruben C; Gur, Raquel E

    2011-01-01

    Ventral striatum (VS) is a critical brain region for reinforcement learning and motivation, and VS hypofunction is implicated in psychiatric disorders including schizophrenia. Providing rewards or performance feedback has been shown to activate VS. Intrinsically motivated subjects performing challenging cognitive tasks are likely to engage reinforcement circuitry even in the absence of external feedback or incentives. However, such intrinsic reinforcement responses have received little attention, have not been examined in relation to behavioral performance, and have not been evaluated for impairment in neuropsychiatric disorders such as schizophrenia. Here we used fMRI to examine a challenging "old" vs. "new" visual recognition task in healthy subjects and patients with schizophrenia. Targets were unique fractal stimuli previously presented as salient distractors in a visual oddball task, producing incidental memory encoding. Based on the prediction error theory of reinforcement learning, we hypothesized that correct target recognition would activate VS in controls, and that this activation would be greater in subjects with lower expectation of responding correctly as indexed by a more conservative response bias. We also predicted these effects would be reduced in patients with schizophrenia. Consistent with these predictions, controls activated VS and other reinforcement processing regions during correct recognition, with greater VS activation in those with a more conservative response bias. Patients did not show either effect, with significant group differences suggesting hyporesponsivity in patients to internally generated feedback. These findings highlight the importance of accounting for intrinsic motivation and reward when studying cognitive tasks, and add to growing evidence of reward circuit dysfunction in schizophrenia that may impact cognition and function.

  4. Striatal intrinsic reinforcement signals during recognition memory: relationship to response bias and dysregulation in schizophrenia

    PubMed Central

    Wolf, Daniel H.; Gerraty, RaphaelT.; Satterthwaite, Theodore D.; Loughead, James; Campellone, Timothy; Elliott, Mark A.; Turetsky, Bruce I.; Gur, Ruben C.; Gur, Raquel E.

    2011-01-01

    Ventral striatum (VS) is a critical brain region for reinforcement learning and motivation, and VS hypofunction is implicated in psychiatric disorders including schizophrenia. Providing rewards or performance feedback has been shown to activate VS. Intrinsically motivated subjects performing challenging cognitive tasks are likely to engage reinforcement circuitry even in the absence of external feedback or incentives. However, such intrinsic reinforcement responses have received little attention, have not been examined in relation to behavioral performance, and have not been evaluated for impairment in neuropsychiatric disorders such as schizophrenia. Here we used fMRI to examine a challenging “old” vs. “new” visual recognition task in healthy subjects and patients with schizophrenia. Targets were unique fractal stimuli previously presented as salient distractors in a visual oddball task, producing incidental memory encoding. Based on the prediction error theory of reinforcement learning, we hypothesized that correct target recognition would activate VS in controls, and that this activation would be greater in subjects with lower expectation of responding correctly as indexed by a more conservative response bias. We also predicted these effects would be reduced in patients with schizophrenia. Consistent with these predictions, controls activated VS and other reinforcement processing regions during correct recognition, with greater VS activation in those with a more conservative response bias. Patients did not show either effect, with significant group differences suggesting hyporesponsivity in patients to internally generated feedback. These findings highlight the importance of accounting for intrinsic motivation and reward when studying cognitive tasks, and add to growing evidence of reward circuit dysfunction in schizophrenia that may impact cognition and function. PMID:22355285

  5. Hybrid integrated optic modules for real-time signal processing

    NASA Technical Reports Server (NTRS)

    Tsai, C. S.

    1984-01-01

    The most recent progress on four relatively new hybrid integrated optic device modules in LiNbO3 waveguides and one in YIG/GGG waveguide that are currently being studied are discussed. The five hybrid modules include a time-integrating acoustooptic correlator, a channel waveguide acoustooptic frequency shifter/modulator, an electrooptic channel waveguide total internal reflection moculator/switch, an electrooptic analog-to-digital converter using a Fabry-Perot modulator array, and a noncollinear magnetooptic modulator using magnetostatic surface waves. All of these devices possess the desirable characteristics of very large bandwidth (GHz or higher), very small substrate size along the optical path (typically 1.5 cm or less), single-mode optical propagation, and low drive power requirement. The devices utilize either acoustooptic, electrooptic or magnetooptic effects in planar or channel waveguides and, therefore, act as efficient interface devices between a light wave and temporal signals. Major areas of application lie in wideband multichannel optical real-time signal processing and communications. Some of the specific applications include spectral analysis and correlation of radio frequency (RF) signals, fiber-optic sensing, optical computing and multiport switching/routing, and analog-to-digital conversion of wide RF signals.

  6. Hybrid integrated optic modules for real-time signal processing

    NASA Astrophysics Data System (ADS)

    Tsai, C. S.

    1984-03-01

    The most recent progress on four relatively new hybrid integrated optic device modules in LiNbO3 waveguides and one in YIG/GGG waveguide that are currently being studied are discussed. The five hybrid modules include a time-integrating acoustooptic correlator, a channel waveguide acoustooptic frequency shifter/modulator, an electrooptic channel waveguide total internal reflection moculator/switch, an electrooptic analog-to-digital converter using a Fabry-Perot modulator array, and a noncollinear magnetooptic modulator using magnetostatic surface waves. All of these devices possess the desirable characteristics of very large bandwidth (GHz or higher), very small substrate size along the optical path (typically 1.5 cm or less), single-mode optical propagation, and low drive power requirement. The devices utilize either acoustooptic, electrooptic or magnetooptic effects in planar or channel waveguides and, therefore, act as efficient interface devices between a light wave and temporal signals. Major areas of application lie in wideband multichannel optical real-time signal processing and communications. Some of the specific applications include spectral analysis and correlation of radio frequency (RF) signals, fiber-optic sensing, optical computing and multiport switching/routing, and analog-to-digital conversion of wide RF signals.

  7. Hybrid integrated optic modules for real-time signal processing

    NASA Technical Reports Server (NTRS)

    Tsai, C. S.

    1984-01-01

    The most recent progress on four relatively new hybrid integrated optic device modules in LiNbO3 waveguides and one in YIG/GGG waveguide that are currently being studied are discussed. The five hybrid modules include a time-integrating acoustooptic correlator, a channel waveguide acoustooptic frequency shifter/modulator, an electrooptic channel waveguide total internal reflection moculator/switch, an electrooptic analog-to-digital converter using a Fabry-Perot modulator array, and a noncollinear magnetooptic modulator using magnetostatic surface waves. All of these devices possess the desirable characteristics of very large bandwidth (GHz or higher), very small substrate size along the optical path (typically 1.5 cm or less), single-mode optical propagation, and low drive power requirement. The devices utilize either acoustooptic, electrooptic or magnetooptic effects in planar or channel waveguides and, therefore, act as efficient interface devices between a light wave and temporal signals. Major areas of application lie in wideband multichannel optical real-time signal processing and communications. Some of the specific applications include spectral analysis and correlation of radio frequency (RF) signals, fiber-optic sensing, optical computing and multiport switching/routing, and analog-to-digital conversion of wide RF signals.

  8. Light at the end of the channel: optical manipulation of intrinsic neuronal excitability with chemical photoswitches

    PubMed Central

    Mourot, Alexandre; Tochitsky, Ivan; Kramer, Richard H.

    2013-01-01

    Ion channels are transmembrane proteins that control the movement of ions across the cell membrane. They are the molecular machines that make neurons excitable by enabling the initiation and propagation of action potentials (APs). Rapid signaling within and between neurons requires complex molecular processes that couple the sensing of membrane voltage or neurotransmitter release to the fast opening and closing of the ion channel gate. Malfunction of an ion channel's sensing or gating module can have disastrous pathological consequences. However, linking molecular changes to the modulation of neural circuits and ultimately to a physiological or pathological state is not a straightforward task. It requires precise and sophisticated methods of controlling the function of ion channels in their native environment. To address this issue we have developed new photochemical tools that enable the remote control of neuronal ion channels with light. Due to its optical nature, our approach permits the manipulation of the nervous system with high spatial, temporal and molecular precision that will help us understand the link between ion channel function and physiology. In addition, this strategy may also be used in the clinic for the direct treatment of some neuronal disorders. PMID:23518818

  9. Optical switches for remote and noninvasive control of cell signaling.

    PubMed

    Gorostiza, Pau; Isacoff, Ehud Y

    2008-10-17

    Although the identity and interactions of signaling proteins have been studied in great detail, the complexity of signaling networks cannot be fully understood without elucidating the timing and location of activity of individual proteins. To do this, one needs a means for detecting and controlling specific signaling events. An attractive approach is to use light, both to report on and control signaling proteins in cells, because light can probe cells in real time with minimal damage. Although optical detection of signaling events has been successful for some time, the development of the means for optical control has accelerated only recently. Of particular interest is the development of chemically engineered proteins that are directly sensitive to light.

  10. Demonstration of optical steganography transmission using temporal phase coded optical signals with spectral notch filtering.

    PubMed

    Hong, Xuezhi; Wang, Dawei; Xu, Lei; He, Sailing

    2010-06-07

    A novel approach is proposed and experimentally demonstrated for optical steganography transmission in WDM networks using temporal phase coded optical signals with spectral notch filtering. A temporal phase coded stealth channel is temporally and spectrally overlaid onto a public WDM channel. Direct detection of the public channel is achieved in the presence of the stealth channel. The interference from the public channel is suppressed by spectral notching before the detection of the optical stealth signal. The approach is shown to have good compatibility and robustness to the existing WDM network for optical steganography transmission.

  11. Phase-locked Optical Signal Recovery

    DTIC Science & Technology

    2009-01-01

    combiner and modulator were all integrated into a single monolithic device. §§ If required, a polariser could be used to filter out the modulated ...implementation. The second scheme is based on heterodyne detection, with the heterodyne frequency chosen to be remote from data modulation interference. In...this approach, the incoming signal passes through a modulator , where it is sinusoidally intensity modulated at microwave frequency by the offset

  12. Phase-locked Optical Signal Recovery

    DTIC Science & Technology

    2009-01-01

    splitter, combiner and modulator were all integrated into a single monolithic device. §§ If required, a polariser could be used to filter out the...implementation. The second scheme is based on heterodyne detection, with the heterodyne frequency chosen to be remote from data modulation interference. In...this approach, the incoming signal passes through a modulator , where it is sinusoidally intensity modulated at microwave frequency by the offset

  13. Fiber optic signal collection system for primary flight control applications

    NASA Astrophysics Data System (ADS)

    Harper, Sandy L.

    1994-10-01

    The FOPMN is a fiber-optic signal collection system for primary flight control applications. An avionics bay protected electro-optic interface unit transmits light down fiber optic cable to an optical sensor housed in the harsh environment of a hydraulic actuator. The interface unit also receives the sensor's reflected pattern and calculates independent positions from the multiplexed signals. This paper discusses the FOPMN method for fiber-optically sensing and multiplexing two channels of position of a TEF actuator's main ram cylinder. Currently installed in NASA Dryden's SRA F/A-18, the FOPMN has accumulated approximately 15 hours of flight time. A performance comparison is made between the FOPMN positions and the flight control computer's feedback mechanism (the actuator LVDTs). Included is a discussion of some of the lessons learned as a result of testing the FOPMN in the lab and in flight. The FOPMN is well on its way to proving itself as a robust fiber optic system with the ability to multiplex numerous optical sensors for primary flight control. The success of the FOPMN leads to the second phase of the project--optical loop closure. Our goal for this phase is to have four FOPMN sensor channels on the main ram and/or the main control valve of the actuator to serve as the quad redundant feedback mechanism for flight control.

  14. Down-Regulation of AKT Signalling by Ursolic Acid Induces Intrinsic Apoptosis and Sensitization to Doxorubicin in Soft Tissue Sarcoma

    PubMed Central

    Villar, Victor Hugo; Vögler, Oliver; Barceló, Francisca; Martín-Broto, Javier; Martínez-Serra, Jordi; Ruiz-Gutiérrez, Valentina; Alemany, Regina

    2016-01-01

    Several important biological activities have been attributed to the pentacyclic triterpene ursolic acid (UA), being its antitumoral effect extensively studied in human adenocarcinomas. In this work, we focused on the efficacy and molecular mechanisms involved in the antitumoral effects of UA, as single agent or combined with doxorubicin (DXR), in human soft tissue sarcoma cells. UA (5–50 μM) strongly inhibited (up to 80%) the viability of STS cells at 24 h and its proliferation in soft agar, with higher concentrations increasing apoptotic death up to 30%. UA treatment (6–9 h) strongly blocked the survival AKT/GSK3β/β-catenin signalling pathway, which led to a concomitant reduction of the anti-apoptotic proteins c-Myc and p21, altogether resulting in the activation of intrinsic apoptosis. Interestingly, UA at low concentrations (10–15 μM) enhanced the antitumoral effects of DXR by up to 2-fold, while in parallel inhibiting DXR-induced AKT activation and p21 expression, two proteins implicated in antitumoral drug resistance and cell survival. In conclusion, UA is able to induce intrinsic apoptosis in human STS cells and also to sensitize these cells to DXR by blocking the AKT signalling pathway. Therefore, UA may have beneficial effects, if used as nutraceutical adjuvant during standard chemotherapy treatment of STS. PMID:27219337

  15. Cooperation of intrinsic and extrinsic signals in the elaboration of regional identity in the posterior cerebral cortex.

    PubMed

    Nothias, F; Fishell, G; Ruiz i Altaba, A

    1998-04-09

    Understanding the compartmentalization of the neocortex (isocortex) of the mammalian brain into functional areas is a challenging problem [1-3] . Unlike pattern formation in the spinal cord and hindbrain, it does not involve the specification of distinct cells types: distinct areas differ in their patterns of connectivity and cytoarchitecture. It has been suggested that signals intrinsic to the neocortical neuroepithelium specify regional fate [3]. Alternatively, spatial patterning might be imposed by extrinsic cues such as thalamocortical projections [4-6]. Recent results highlight the ability of early precursor cells of the telencephalic neuroepithelium to 'remember' their spatial position from times before thalamic innervation [7,8] [9-12]. An influence from the thalamus, however, cannot be ruled out as there is a precise invasion of the correct cortical areas by the corresponding projections [13,14]. Furthermore, cortical neuronal progenitors have been proposed to adopt new connection patterns after transplantation [6,7], as well as when the thalamic input is rerouted [15,16]. Here, we describe the transient expression of the homeobox gene Otx2 in the posterior, prospective visual, neocortex and use it to analyze the establishment of posterior cortical fate. The results suggest that whereas intrinsic cortical information is sufficient to specify regional fate, extrinsic signals from the thalamus are involved in the expansion or maintenance of the population of cells expressing Otx2 but not in regionalization.

  16. Signal restoration in intensity-modulated optical OFDM access systems.

    PubMed

    Vanin, Evgeny

    2011-11-15

    It is well known that deliberate signal clipping in an intensity-modulated (IM) laser transmitter helps to overcome the optical orthogonal frequency division multiplexing (OFDM) system performance limitation that is related to the signal high peak-to-average power ratio. The amplitude of a clipped OFDM signal has to be optimized in order to minimize the optical power that is required to achieve a specified system performance. However, the signal clipping introduces nonlinear distortion (so-called clipping noise) and leads to a system performance penalty. In this Letter, the performance of the IM optical OFDM system with digital baseband clipping distortion in the transmitter and clipping noise compensation by means of signal restoration in the digital signal processing unit of the system receiver is analytically evaluated. It is demonstrated that the system bit-error ratio can be reduced by more than an order of magnitude, from 10(-3) to 3.5×10(-5), by applying only the first iteration of the signal restoration algorithm proposed in this Letter. The results of the analytical analysis are verified with brute-force numerical simulations based on direct error counting.

  17. The Potential of Brittle Star Extracted Polysaccharide in Promoting Apoptosis via Intrinsic Signaling Pathway.

    PubMed

    Baharara, Javad; Amini, Elaheh

    2015-01-01

    Anti-cancer potential of marine natural products such as polysaccharides represented therapeutic potential in oncological researches. In this study, total polysaccharide from brittle star [Ophiocoma erinaceus (O. erinaceus)] was extracted and chemopreventive efficacy of Persian Gulf brittle star polysaccharide was investigated in HeLa human cervical cancer cells. To extract polysaccharide, dried brittle stars were ground and extracted mechanically. Then, detection of polysaccharide was performed by phenol sulfuric acid, Ultra Violet (UV)-sulfuric acid method and FTIR. The anti proliferative activity of isolated polysaccharide was examined by MTT assay and evaluation of cell death was done through morphological cell changes; Propodium Iodide staining, fluorescence microscopy and caspase-3, -9 enzymatic measurements. To assess its underlying mechanism, expression of Bax, Bcl-2 was evaluated. The polysaccharide detection methods demonstrated isolation of crude polysaccharide from Persian Gulf brittle star. The results revealed that O. erinaceus polysaccharide suppressed the proliferation of HeLa cells in a dose and time dependent manner. Morphological observation of DAPI and Acridine Orange/Propodium Iodide staining was documented by typical characteristics of apoptotic cell death. Flow cytometry analyses exhibited the accumulation of treated cells in sub-G1 region. Additionally, polysaccharide extracted induced intrinsic apoptosis via up-regulation of caspase-3, caspase-9 and Bax along with down-regulation of Bcl-2 in HeLa cells. Taken together, the apoptosis inducing effect of brittle star polysaccharide via intrinsic pathway confirmed the anti tumor potential of marine polysaccharide. Therefore, these findings proposed new insight into anti cancer properties of brittle star polysaccharide as a promising agent in cervical cancer treatment.

  18. The Potential of Brittle Star Extracted Polysaccharide in Promoting Apoptosis via Intrinsic Signaling Pathway

    PubMed Central

    Baharara, Javad; Amini, Elaheh

    2015-01-01

    Background: Anti-cancer potential of marine natural products such as polysaccharides represented therapeutic potential in oncological researches. In this study, total polysaccharide from brittle star [Ophiocoma erinaceus (O. erinaceus)] was extracted and chemopreventive efficacy of Persian Gulf brittle star polysaccharide was investigated in HeLa human cervical cancer cells. Methods: To extract polysaccharide, dried brittle stars were ground and extracted mechanically. Then, detection of polysaccharide was performed by phenol sulfuric acid, Ultra Violet (UV)-sulfuric acid method and FTIR. The anti proliferative activity of isolated polysaccharide was examined by MTT assay and evaluation of cell death was done through morphological cell changes; Propodium Iodide staining, fluorescence microscopy and caspase-3, -9 enzymatic measurements. To assess its underlying mechanism, expression of Bax, Bcl-2 was evaluated. Results: The polysaccharide detection methods demonstrated isolation of crude polysaccharide from Persian Gulf brittle star. The results revealed that O. erinaceus polysaccharide suppressed the proliferation of HeLa cells in a dose and time dependent manner. Morphological observation of DAPI and Acridine Orange/Propodium Iodide staining was documented by typical characteristics of apoptotic cell death. Flow cytometry analyses exhibited the accumulation of treated cells in sub-G1 region. Additionally, polysaccharide extracted induced intrinsic apoptosis via up-regulation of caspase-3, caspase-9 and Bax along with down-regulation of Bcl-2 in HeLa cells. Conclusion: Taken together, the apoptosis inducing effect of brittle star polysaccharide via intrinsic pathway confirmed the anti tumor potential of marine polysaccharide. Therefore, these findings proposed new insight into anti cancer properties of brittle star polysaccharide as a promising agent in cervical cancer treatment. PMID:26605009

  19. Silicon technology compatible photonic molecules for compact optical signal processing

    SciTech Connect

    Barea, Luis A. M. Vallini, Felipe; Jarschel, Paulo F.; Frateschi, Newton C.

    2013-11-11

    Photonic molecules (PMs) based on multiple inner coupled microring resonators allow to surpass the fundamental constraint between the total quality factor (Q{sub T}), free spectral range (FSR), and resonator size. In this work, we use a PM that presents doublets and triplets resonance splitting, all with high Q{sub T}. We demonstrate the use of the doublet splitting for 34.2 GHz signal extraction by filtering the sidebands of a modulated optical signal. We also demonstrate that very compact optical modulators operating 2.75 times beyond its resonator linewidth limit may be obtained using the PM triplet splitting, with separation of ∼55 GHz.

  20. Advanced Integrated Optical Signal Processing Components.

    NASA Astrophysics Data System (ADS)

    Rastani, Kasra

    This research was aimed at the development of advanced integrated optical components suitable for devices capable of processing multi-dimensional inputs. In such processors, densely packed waveguide arrays with low crosstalk are needed to provide dissection of the information that has been partially processed. Waveguide arrays also expand the information in the plane of the processor while maintaining its coherence. Rib waveguide arrays with low loss, high mode confinement and highly uniform surface quality (660 elements, 8 μm wide, 1 μm high, and 1 cm long with 2 mu m separations) were fabricated on LiNbO _3 substrates through the ion beam milling technique. A novel feature of the multi-dimensional IO processor architecture proposed herein is the implementation of large area uniform outcoupling (with low to moderate outcoupling efficiencies) from rib waveguide arrays in order to access the third dimension of the processor structure. As a means of outcoupling, uniform surface gratings (2 μm and 4 μm grating periods, 0.05 μm high and 1 mm long) with low outcoupling efficiencies (of approximately 2-18%/mm) were fabricated on the nonuniform surface of the rib waveguide arrays. As a practical technique of modulating the low outcoupling efficiencies of the surface gratings, it was proposed to alter the period of the grating as a function of position along each waveguide. Large aperture (2.5 mm) integrated lenses with short positive focal lengths (1.2-2.5 cm) were developed through a modification of the titanium-indiffused proton exchanged (TIPE) technique. Such integrated lenses were fabricated by increasing the refractive index of the slab waveguides by the TIPE process while maintaining the refractive index of the lenses at the lower level of Ti:LiNbO _3 waveguide. By means of curvature reversal of the integrated lenses, positive focal length lenses have been fabricated while providing high mode confinement for the slab waveguide. The above elements performed as

  1. Digital signal processing for fiber-optic thermometers

    SciTech Connect

    Fernicola, V.; Crovini, L.

    1994-12-31

    A digital signal processing scheme for measurement of exponentially-decaying signals, such as those found in fluorescence, lifetime-based, fiber-optic sensors, is proposed. The instrument uses a modified digital phase-sensitive-detection technique with the phase locked to a fixed value and the modulation period tracking the measured lifetime. Typical resolution of the system is 0.05% for slow decay (>500 {mu}s) and 0.1% for fast decay.

  2. Signal simulation and signal processing for multiple reference optical coherence tomography

    NASA Astrophysics Data System (ADS)

    Neuhaus, Kai; Subhash, Hrebesh; Dsouza, Roshan; Hogan, Josh; Wilson, Carol; Leahy, Martin

    2015-03-01

    The generation of a synthetic MR-OCT signal is presented and compared to a real acquired signal. Multiple reference optical coherence tomography (MR-OCT) is a novel time-domain interferometric system. The MR-OCT principle is adding a partial mirror to extend the axial scan range, which effectively extends the scan depth for imaging. The actuation of the scan mirror required for time-domain OCT, was demonstrated to operate with a low cost miniature voice coil, such as a speaker extracted from a smartphone or CD/DVD pick-up system. Building a compact and cost-effective optical imaging system will enable affordable medical diagnosis at low-resource setting applications. The partial mirror recirculates multiple reflections (orders) into the interferometric system and the increase of optical path delay does increase the beat frequency of the interference signal. The synthesis of such an interference signal using a numerical method is described in this manuscript.

  3. BPSK optical mm-wave signal generation by septupling frequency via a single optical phase modulator

    NASA Astrophysics Data System (ADS)

    Wu, Peng; Ma, Jianxin

    2016-09-01

    In this paper, we have proposed a novel and simple scheme to generate the BPSK optical millimeter wave (MMW) signal with frequency septupling by using an optical phase modulator (PM) and a wavelength selective switch (WSS). In this scheme, the PM is driven by a radio frequency (RF) BPSK signal at the optimized modulation index of 4.89 to assure the 4th and 3rd-order sidebands have equal amplitudes. An wavelength selective switch (WSS) is used to abstract the -4th and +3rd-order sidebands from the spectrum generated by RF BPSK signal modulating the lightwave to form the BPSK optical MMW signal with frequency septupling the driving RF signal. In these two tones, only the +3rd-order sideband bears the BPSK signal while the -4th-order sideband is unmodulated since the phase information is canceled by the even times multiplication of the phase of BPSK signal. The MMW signal can avoid the pulse walk-off effect and the amplitude fading effect caused by the fiber chromatic dispersion. By adjusting the modulation index to assure the two tones have equal amplitude, the generated optical MMW signal has the maximal opto-electrical conversion efficiency and good transmission performance.

  4. Studies of beam expansion and distributed Bragg reflector lasers for fiber optics and optical signal processing

    NASA Astrophysics Data System (ADS)

    Garmire, E. M.

    1981-03-01

    Separate studies were performed on beam expansion and on distributed Bragg Reflector (DBR) lasers preliminary to monolithic integration on GaAs substrates. These components are proposed for use in optical signal processing, for fiber optic sources and for high brightness lasers.

  5. Visible light communications using predistortion signal to enhance the response of passive optical receiver

    NASA Astrophysics Data System (ADS)

    Liu, Yang; Chen, Hung-Yu; Liang, Kevin; Wei, Liang-Yu; Chow, Chi-Wai; Yeh, Chien-Hung

    2016-01-01

    Traditional visible light communication (VLC) uses positive-intrinsic-negative photodiode (PD) or avalanche PD as the optical receivers (Rx). We demonstrate using a solar cell as the VLC Rx. The solar cell is flexible and low cost and converts the optical signal into an electrical signal directly without the need of external power supply. In addition to acting as the VLC passive Rx, the converted electrical signal from the solar cell can charge up the battery of the Rx nodes. Hence, the proposed scheme can be a promising candidate for the future Internet of Things network. However, a solar cell acting as a VLC Rx is very challenging, since the response of the solar cell is limited. Here, we propose and demonstrate using predistortion to significantly enhance the solar cell Rx response for the first time up to the authors' knowledge. Experimental results show that the response of the solar cell Rx is significantly enhanced; and the original 2-kHz detection bandwidth of the solar cell can be enhanced by 250 times for receiving 500-kbit/s VLC signal at a transmission distance of 1 m. The operation principle, the generated voltage by the solar cell, and the maximum data rates achieved at different transmission distances are also studied.

  6. STIM1 Regulates Somatic Ca(2+) Signals and Intrinsic Firing Properties of Cerebellar Purkinje Neurons.

    PubMed

    Ryu, Changhyeon; Jang, Dong Cheol; Jung, Dayoon; Kim, Yong Gyu; Shim, Hyun Geun; Ryu, Hyun-Hee; Lee, Yong-Seok; Linden, David J; Worley, Paul F; Kim, Sang Jeong

    2017-09-13

    Control of Ca(2+) flux between the cytosol and intracellular Ca(2+) stores is essential for maintaining normal cellular function. It has been well established in both neuronal and non-neuronal cells that stromal interaction molecule 1 (STIM1) initiates and regulates refilling Ca(2+) into the ER. Here, we describe a novel, additional role for STIM1, the regulation of free cytosolic Ca(2+), and the consequent control of spike firing in neurons. Among central neurons, cerebellar Purkinje neurons express the highest level of STIM1, and they fire continuously in the absence of stimulation, making somatic Ca(2+) homeostasis of particular importance. By using Purkinje neuron-specific STIM1 knock-out (STIM1(PKO)) male mice, we found that the deletion of STIM1 delayed clearance of cytosolic Ca(2+) in the soma during ongoing neuronal firing. Deletion of STIM1 also reduced the Purkinje neuronal excitability and impaired intrinsic plasticity without affecting long-term synaptic plasticity. In vestibulo-ocular reflex learning, STIM1(PKO) male mice showed severe deficits in memory consolidation, whereas they were normal in memory acquisition. Our results suggest that STIM1 is critically involved in the regulation of the neuronal excitability and the intrinsic plasticity of the Purkinje neurons as well as cerebellar memory consolidation.SIGNIFICANCE STATEMENT Stromal interaction molecule 1 (STIM1), which regulates the refilling of ER Ca(2+), has been investigated in several systems including the CNS. In addition to a previous study showing that STIM1 regulates dendritic ER Ca(2+) refilling and mGluR1-mediated synaptic transmission, we provide compelling evidence describing a novel role of STIM1 in spike firing Purkinje neurons. We found that STIM1 regulates cytosolic Ca(2+) clearance of the soma during spike firing, and the interruption of this cytosolic Ca(2+) clearing disrupts neuronal excitability and cerebellar memory consolidation. Our results provide new insights into

  7. Spectroscopic imaging for detection of ischemic injury in rat kidneys by use of changes in intrinsic optical properties

    NASA Astrophysics Data System (ADS)

    Michalopoulou, Andromachi P.; Fitzgerald, Jason T.; Troppmann, Christoph; Demos, Stavros G.

    2005-04-01

    It is currently impossible to consistently predict kidney graft viability and function before and after transplantation. We explored optical spectroscopy to assess the degree of ischemic damage in kidney tissue. Tunable UV laser excitation was used to record autofluorescence images, at different spectral ranges, of injured and contralateral control rat kidneys to reveal the excitation conditions that offered optimal contrast. Autofluorescence and near-infrared cross-polarized light-scattering imaging were both used to monitor changes in intensity and spectral characteristics, as a function of exposure time to ischemic injury. These two modalities provided different temporal behaviors, arguably arising from two different mechanisms providing direct correlation of intrinsic optical signatures to ischemic injury time.

  8. Coupled-wave analysis of vector holograms. 3. Effects of intrinsic distribution of optical axis in anisotropic media.

    PubMed

    Sasaki, Tomoyuki; Miura, Kenta; Hanaizumi, Osamu; Ono, Hiroshi

    2011-12-20

    We investigated theoretically the interference of two counterpropagating polarized light beams in optically anisotropic media whose optical axis is in the film plane and is gradually rotated around the thickness direction. Results indicated that pure polarization modulation without intensity variation is obtained in the inhomogeneous media when the total angle of the rotation is much smaller than the total retardation. Reflective anisotropic gratings recorded by the polarization modulation were formulated as the perturbation of the dielectric tensor, and diffraction properties were studied using coupled-wave analysis (CWA) and a numerical method. By assuming that the period of the intrinsic distribution is substantially larger than that of the induced one, we demonstrated that CWA estimates the diffraction efficiency and the polarization state of the diffracted light with high accuracy.

  9. Activation of intrinsic apoptotic signaling pathway in cancer cells by Cymbopogon citratus polysaccharide fractions.

    PubMed

    Thangam, Ramar; Sathuvan, Malairaj; Poongodi, Arasu; Suresh, Veeraperumal; Pazhanichamy, Kalailingam; Sivasubramanian, Srinivasan; Kanipandian, Nagarajan; Ganesan, Nalini; Rengasamy, Ramasamy; Thirumurugan, Ramasamy; Kannan, Soundarapandian

    2014-07-17

    Essential oils of Cymbopogon citratus were already reported to have wide ranging medical and industrial applications. However, information on polysaccharides from the plant and their anticancer activities are limited. In the present study, polysaccharides from C. citratus were extracted and fractionated by anion exchange and gel filtration chromatography. Two different polysaccharide fractions such as F1 and F2 were obtained, and these fractions were found to have distinct acidic polysaccharides as characterized by their molecular weight and sugar content. NMR spectral analysis revealed the presence of (1→4) linked b-d-Xylofuranose moiety in these polysaccharides. Using these polysaccharide fractions F1 and F2, anti-inflammatory and anticancer activities were evaluated against cancer cells in vitro and the mechanism of action of the polysaccharides in inducing apoptosis in cancer cells via intrinsic pathway was also proposed. Two different reproductive cancer cells such as Siha and LNCap were employed for in vitro studies on cytotoxicity, induction of apoptosis and apoptotic DNA fragmentation, changes in mitochondrial membrane potential, and profiles of gene and protein expression in response to treatment of cells by the polysaccharide fractions. These polysaccharide fractions exhibited potential cytotoxic and apoptotic effects on carcinoma cells, and they induced apoptosis in these cells through the events of up-regulation of caspase 3, down-regulation of bcl-2 family genes followed by cytochrome c release. Copyright © 2014 Elsevier Ltd. All rights reserved.

  10. Jak/Stat Signaling Stimulates Zebrafish Optic Nerve Regeneration and Overcomes the Inhibitory Actions of Socs3 and Sfpq

    PubMed Central

    Elsaeidi, Fairouz; Bemben, Michael A.; Zhao, Xiao-Feng

    2014-01-01

    The regenerative failure of mammalian optic axons is partly mediated by Socs3-dependent inhibition of Jak/Stat signaling (Smith et al., 2009, 2011). Whether Jak/Stat signaling is part of the normal regenerative response observed in animals that exhibit an intrinsic capacity for optic nerve regeneration, such as zebrafish, remains unknown. Nor is it known whether the repression of regenerative inhibitors, such as Socs3, contributes to the robust regenerative response of zebrafish to optic nerve damage. Here we report that Jak/Stat signaling stimulates optic nerve regeneration in zebrafish. We found that IL-6 family cytokines, acting via Gp130-coupled receptors, stimulate Jak/Stat3 signaling in retinal ganglion cells after optic nerve injury. Among these cytokines, we found that CNTF, IL-11, and Clcf1/Crlf1a can stimulate optic axon regrowth. Surprisingly, optic nerve injury stimulated the expression of Socs3 and Sfpq (splicing factor, proline/glutamine rich) that attenuate optic nerve regeneration. These proteins were induced in a Jak/Stat-dependent manner, stimulated each other's expression and suppressed the expression of regeneration-associated genes. In vivo, the injury-dependent induction of Socs3 and Sfpq inhibits optic nerve regeneration but does not block it. We identified a robust induction of multiple cytokine genes in zebrafish retinal ganglion cells that may contribute to their ability to overcome these inhibitory factors. These studies not only identified mechanisms underlying optic nerve regeneration in fish but also suggest new molecular targets for enhancing optic nerve regeneration in mammals. PMID:24523552

  11. Optical signal processing using photonic reservoir computing

    NASA Astrophysics Data System (ADS)

    Salehi, Mohammad Reza; Dehyadegari, Louiza

    2014-10-01

    As a new approach to recognition and classification problems, photonic reservoir computing has such advantages as parallel information processing, power efficient and high speed. In this paper, a photonic structure has been proposed for reservoir computing which is investigated using a simple, yet, non-partial noisy time series prediction task. This study includes the application of a suitable topology with self-feedbacks in a network of SOA's - which lends the system a strong memory - and leads to adjusting adequate parameters resulting in perfect recognition accuracy (100%) for noise-free time series, which shows a 3% improvement over previous results. For the classification of noisy time series, the rate of accuracy showed a 4% increase and amounted to 96%. Furthermore, an analytical approach was suggested to solve rate equations which led to a substantial decrease in the simulation time, which is an important parameter in classification of large signals such as speech recognition, and better results came up compared with previous works.

  12. Probing the effect of intrinsic defects and dopants on the structural evolution and optical properties of ZnO nanocrystallites

    SciTech Connect

    Panda, N. R.; Sahu, D.; Acharya, B. S.; Nayak, P.

    2015-06-24

    Role of intrinsic defects and external impurities in modifying the structural and optical properties of ZnO nanostructures has been studied and discussed. ZnO nanocrystallites doped with B, N and S elements have been prepared by ultrasound assisted wet chemical method. Structural evolution of ZnO in presence of dopant ions has been studied by XRD and electron microscopic measurements. Elemental analysis like XPS has been carried out to ascertain the dopant configuration. A variation in crystallographic parameters and microstructure is found to be observed as impurity is incorporated into ZnO. This has been explained on the basis of the substitution of dopant at Zn{sup 2+} and O{sup −} sites rearranging the lattice. Optical absorption measurements and PL studies reflect a change in band gap of ZnO by impurity adsorption. Most of the cases, the band gap is found to be broadened which has been explained in the line of Moss-Burstein effect. The excitonic emission in ZnO is observed to blue shift supporting the above results and the defect emissions also get modified in terms of position and intensity. New PL bands observed have been assigned to the transitions related to the defect states present in the band gap of ZnO along with intrinsic defects.

  13. MiRNA-34 intrinsically links p53 tumor suppressor and Wnt signaling.

    PubMed

    Cha, Yong Hoon; Kim, Nam Hee; Park, Changbum; Lee, Inhan; Kim, Hyun Sil; Yook, Jong In

    2012-04-01

    Though tumor suppressor p53 and the canonical Wnt cascade have been extensively studied for the last 30 years, due to their important physiological roles, the two signaling pathways have been largely considered independent. Recently, the miR-34 family was found to directly link p53 and Wnt, revealing the tight connection between loss of tumor suppressor function and activation of oncogenic signaling. These observations demonstrate that miR-34, known to be directly downstream of p53, targets a set of highly conserved sites in the UTR of Wnt and EMT genes, specifically WNT1, WNT3, LRP6, AXIN2, β-catenin, LEF1 and Snail, resulting in suppression of TCF/LEF transcriptional activity and the EMT program. The loss of p53 function increases Wnt activities and promotes the Snail-dependent EMT program at multiple levels in a miR-34/UTR-specific manner. The TCF/LEF transcriptional signature was closely associated with functionality of p53 and miR-34 in clinical samples, suggesting the pervasive impact of miR-34 loss on the oncogenic pathway in human cancer. Here, we review recent findings on ceRNA in light of novel data to elucidate the physiological relevance of the p53-miR-34-Wnt network, which encompasses sets of genes and directions of signaling. As loss of wt-p53 or hyperactivation of Wnt is critical in maintaining cancer stem cell properties and in establishing the metastatic program, these observations indicate a mechanism of miR-mediated quasi-sufficiency which connects tumor suppressor and oncogenic signaling pathways, supporting a continuum model of human cancer.

  14. Atmospheric Chemistry Special Feature: Effect of intrinsic organic carbon on the optical properties of fresh diesel soot

    NASA Astrophysics Data System (ADS)

    Adler, Gabriella; Abo Riziq, Ali; Erlick, Carynelisa; Rudich, Yinon

    2010-04-01

    This study focuses on the retrieval of the normalized mass absorption cross section (MAC) of soot using theoretical calculations that incorporate new measurements of the optical properties of organic carbon (OC) intrinsic to fresh diesel soot. Intrinsic OC was extracted by water and an organic solvent, and the complex refractive index of the extracted OC was derived at 532 and 355-nm wavelengths using cavity ring-down aerosol spectrometry. The extracted OC was found to absorb weakly in the visible wavelengths and moderately at blue wavelengths. The mass ratio of OC and elemental carbon (EC) in the collected particles was evaluated using a thermo-optical method. The measured EC/OC ratio in the soot exhibited substantial variability from measurement to measurement, ranging between 2 and 5. To test the sensitivity of the MAC to this variability, three different EC/OC ratios (2∶1, 1∶1, and 1∶2) were chosen as representative. Particle size and spherule morphology were estimated using scanning electron microscopy, and the soot was found to be primarily in the form of aggregates with a dominant aggregate diameter mode in the range 200-250 nm. The measured refractive index of the extracted OC was used with a variety of theoretical models to calculate the MAC of internally mixed diesel soot at 532 and 355 nm. We conclude that Rayleigh-Debye-Gans theory on clusters of coated spherules and T-matrix of a solid EC spheroid coated by intrinsic OC are both consistent with previous measurements; however, Rayleigh-Debye-Gans theory provides a more realistic physical model for the calculation

  15. Multiplexed interferometric fiber-optic sensors with digital signal processing.

    PubMed

    Sadkowski, R; Lee, C E; Taylor, H F

    1995-09-01

    A microcontroller-based digital signal processing system developed for use with fiber-optic sensors for measuring pressure in internal combustion engines is described. A single distributed feedback laser source provides optical power for four interferometric sensors. The laser current is repetitively modulated so that its optical frequency is nearly a linear function of time over most of a cycle. The interferometer phase shift is proportional to the elapsed time from the initiation of a sawtooth until the sensor output signal level crosses a threshold value proportional to the laser output power. This elapsed time, assumed to vary linearly with the combustion chamber pressure, is determined by the use of a digital timer-counter. The system has been used with fiber Fabry-Perot interferometer transducers for in-cylinder pressure measurement on a four-cylinder gasoline-powered engine.

  16. The Role of Adaptive Photorefractive Power Limiting on Acousto-Optic Radio Frequency (RF) Signal Excision

    DTIC Science & Technology

    2001-12-01

    Adaptive RF interference reduction for broadband communication systems continues to be problematic. The acousto - optic RF signal excision system...novel photorefractive optical power limiting device to achieve adaptive notch filtering, and multi- channel acousto - optic deflection to achieve angle...of-arrival signal discrimination at the notch filter. This dissertation describes basic principles of acousto - optic RF signal excision, including

  17. Secure optical telecommunications using chaos in wavelength for signal transmission

    NASA Astrophysics Data System (ADS)

    Goedgebuer, Jean-Pierre; Larger, Laurent

    1997-12-01

    Secure communications based on chaos have been investigated for some years, especially in the area of radio frequency transmissions. Signal decoding and decoding is then generally achieved using a RF carrier whose amplitude fluctuates chaotically. Recent advances have also been reported in the field of optical telecommunications. Optical chaos produced by random fluctuations of laser power is the sued to encrypt signals. However most of the system reported so far are plagued by their low flexibility which makes difficult the key to be changed easily. We report experiments in which chaos in wavelength, rather than in power, is advantageously used to encrypt signals. The latter are encrypted as chaotic fluctuations of the wavelength of a tunable semiconductor laser driven by a generator of chaos. Decoding makes use of another generator of chaos operating as a local oscillator synchronized on the first one. The first results are reported in the wavelength range of 1550 nm.

  18. Secure optical telecommunications using chaos in wavelength for signal transmissions

    NASA Astrophysics Data System (ADS)

    Goedgebuer, Jean-Pierre; Larger, Laurent; Rhodes, William T.

    1999-07-01

    Severe communications based on chaos have been investigated for some years, especially in the area of radiofrequency transmissions. Signal decoding and decoding is then generally achieved using a RF carrier whose amplitude fluctuates chaotically. Recent advances have also been reported in the field of optical telecommunications. Optical chaos produced by random fluctuations of laser power is then used to encrypt signals. However most of the systems reported so far are plagued by their low flexibility which makes difficult the key to be changed easily. We report experiments in which chaos in wavelength, rather than in power, is advantageously used to encrypt signals. The latter are encrypted as chaotic fluctuations of the wavelength of a tunable semiconductor laser driven by a generator of chaos. Decoding makes use of another generator of chaos operating as a local oscillator synchronized on the first one. The first results are reported in the wavelength range of 1550 nm.

  19. Regulation of Na+ excretion and arterial blood pressure by purinergic signalling intrinsic to the distal nephron: consequences and mechanisms.

    PubMed

    Mironova, E; Boiko, N; Bugaj, V; Kucher, V; Stockand, J D

    2015-01-01

    Discretionary control of Na(+) excretion is a key component of the regulation of arterial blood pressure in mammals. Sodium excretion is fine-tuned in the aldosterone-sensitive distal nephron by the activity of the epithelial Na(+) channel (ENaC). Here, ENaC functions as a final effector of the renin-angiotensin-aldosterone system (RAAS) during negative feedback control of blood pressure. Mutations affecting ENaC activity and abnormal regulation of this channel affect blood pressure through pathological changes to Na(+) excretion. Recent evidence demonstrates that powerful signalling pathways function in parallel with the RAAS to modulate ENaC activity and blood pressure. An inclusive paradigm is emerging with respect to regulation of blood pressure where ENaC serves as a critical point of convergence for several important signalling systems that affect renal Na(+) excretion. A robust inhibitory purinergic signalling system intrinsic to the distal nephron dynamically regulates ENaC through paracrine ATP signalling via the metabotropic P2Y2 purinergic receptor to properly match urinary Na(+) excretion to dietary Na(+) intake. This enables blood pressure to be maintained within a normal range despite broad changes in dietary Na(+) consumption. Loss of purinergic inhibition of ENaC increases blood pressure by causing inappropriate Na(+) excretion. In contrast, stimulation of the P2Y2 receptor promotes natriuresis and a decrease in blood pressure. Such observations identify purinergic signalling in the distal nephron as possibly causative, when dysfunctional, for certain forms of elevated blood pressure, and as a possible therapeutic target for the treatment of elevated blood pressure particularly that associated with salt sensitivity. © 2014 Scandinavian Physiological Society. Published by John Wiley & Sons Ltd.

  20. Proposal of Novel Optical Burst Signal Receiver for ONU in Optical Switched Access Network

    NASA Astrophysics Data System (ADS)

    Ueda, Hiromi; Hamasaki, Keita; Kuriyama, Takashi; Tsuboi, Toshinori; Kasai, Hiroyuki

    To realize economical optical burst signal receivers for the Optical Network Unit (ONU) of the Ethernet Optical Switched Access Network (E-OSAN), we previously implemented optical burst receivers with AC-coupling and DC-coupling using off-the-shelf components, and showed that the former offers better performance. This paper proposes a new optical burst signal receiver that uses the transfer function, Gn(s) =1-Hn(s), where Hn(s) denotes a Bessel filter transfer function of order n. We also present a method for designing the proposed receiver and clarify that it has better performance than the conventional AC-coupling one. We then present an LCR circuit synthesis of Gn(s), which is necessary to actually implement a burst receiver based on the proposal.

  1. Signal to noise ratio of free space homodyne coherent optical communication after adaptive optics compensation

    NASA Astrophysics Data System (ADS)

    Huang, Jian; Mei, Haiping; Deng, Ke; Kang, Li; Zhu, Wenyue; Yao, Zhoushi

    2015-12-01

    Designing and evaluating the adaptive optics system for coherent optical communication link through atmosphere requires to distinguish the effects of the residual wavefront and disturbed amplitude to the signal to noise ratio. Based on the new definition of coherent efficiency, a formula of signal to noise ratio for describing the performance of coherent optical communication link after wavefront compensation is derived in the form of amplitude non-uniformity and wavefront error separated. A beam quality metric is deduced mathematically to evaluate the effect of disturbed amplitude to the signal to noise ratio. Experimental results show that the amplitude fluctuation on the receiver aperture may reduce the signal to noise ratio about 24% on average when Fried coherent length r0=16 cm.

  2. Applications of electro-optic gratings in integrated optical signal processing devices

    NASA Technical Reports Server (NTRS)

    Verber, C. M.

    1981-01-01

    A variety of applications of electro-optically induced Bragg gratings in integrated optical signal processing and computation devices are shown. The gratings are easy to fabricate, operate efficiently on relatively low voltages and have design principles which are well known and reliable. The component allows a rapid and efficient interaction with an optical wave in a planar electro-optic waveguide. The operation of such gratings and their use as intensity modulators, spatial light modulators, and components in correlators and in a variety of computational units is described.

  3. Bacteriorhodopsin films for optical signal processing and data storage

    NASA Technical Reports Server (NTRS)

    Walkup, John F. (Principal Investigator); Mehrl, David J. (Principal Investigator)

    1996-01-01

    This report summarizes the research results obtained on NASA Ames Grant NAG 2-878 entitled 'Investigations of Bacteriorhodopsin Films for Optical Signal Processing and Data Storage.' Specifically we performed research, at Texas Tech University, on applications of Bacteriorhodopisin film to both (1) dynamic spatial filtering and (2) holographic data storage. In addition, measurements of the noise properties of an acousto-optical matrix-vestor multiplier built for NASA Ames by Photonic Systems Inc. were performed at NASA Ames' Photonics Laboratory. This research resulted in two papers presented at major optical data processing conferences and a journal paper which is to appear in APPLIED OPTICS. A new proposal for additional BR research has recently been submitted to NASA Ames Research Center.

  4. Analysis of intrinsic coupling loss in multi-step index optical fibres.

    PubMed

    Aldabaldetreku, Gotzon; Durana, Gaizka; Zubia, Joseba; Arrue, Jon; Jiménez, Felipe; Mateo, Javier

    2005-05-02

    The main goal of the present paper is to provide a comprehensive analysis of the intrinsic coupling loss for multi-step index (MSI) fibres and compare it with those obtained for step- and graded-index fibres. We investigate the effects of tolerances to each waveguide parameter typical in standard manufacturing processes by carrying out several simulations using the ray-tracing method. The results obtained will serve us to identify the most critical waveguide variations to which fibre manufactures will have to pay closer attention to achieve lower coupling losses.

  5. Interchangeability of Caenorhabditis elegans DSL proteins and intrinsic signalling activity of their extracellular domains in vivo.

    PubMed

    Fitzgerald, K; Greenwald, I

    1995-12-01

    Ligands of the Delta/Serrate/lag-2 (DSL) family and their receptors, members of the lin-12/Notch family, mediate cell-cell interactions that specify cell fate in invertebrates and vertebrates. In C. elegans, two DSL genes, lag-2 and apx-1, influence different cell fate decisions during development. Here we show that APX-1 can fully substitute for LAG-2 when expressed under the control of lag-2 regulatory sequences. In addition, we demonstrate that truncated forms lacking the transmembrane and intracellular domains of both LAG-2 and APX-1 can also substitute for endogenous lag-2 activity. Moreover, we provide evidence that these truncated forms are secreted and able to activate LIN-12 and GLP-1 ectopically. Finally, we show that expression of a secreted DSL domain alone may enhance endogenous LAG-2 signalling. Our data suggest ways that activated forms of DSL ligands in other systems may be created.

  6. Intrinsic cellular signaling mechanisms determine the sensitivity of cancer cells to virus-induced apoptosis

    PubMed Central

    Wang, Yunfei; Li, Dawei; Luo, Jian; Tian, Guimei; Zhao, Lisa Y.; Liao, Daiqing

    2016-01-01

    Cancer cells of epithelial and mesenchymal phenotypes exhibit different sensitivities to apoptosis stimuli, but the mechanisms underlying this phenomenon remain partly understood. We constructed a novel recombinant adenovirus expressing Ad12 E1A (Ad-E1A12) that can strongly induce apoptosis. Ad-E1A12 infection of epithelial cancer cells displayed dramatic detachment and apoptosis, whereas cancer cells of mesenchymal phenotypes with metastatic propensity were markedly more resistant to this virus. Notably, forced detachment of epithelial cells did not further sensitize them to Ad-E1A12-induced apoptosis, suggesting that cell detachment is a consequence rather than the cause of Ad-E1A12-induced apoptosis. Ad-E1A12 increased phosphorylation of AKT1 and ribosomal protein S6 through independent mechanisms in different cell types. Ad-E1A12–induced AKT1 phosphorylation was PI3K-dependent in epithelial cancer cells, and mTOR-dependent in mesenchymal cancer cells. Epithelial cancer cells upon Ad-E1A12-induced detachment could not sustain AKT activation due to AKT1 degradation, but AKT1 activation was maintained in mesenchymal cancer cells. Expression of epithelial cell-restricted miR-200 family in mesenchymal cells limited mTOR signaling and sensitized them to Ad-E1A12-induced cell killing. Thus, epithelial cancer cells rely on the canonical PI3K-AKT signaling pathway for survival, while mesenchymal cancer cells deploy the PI3K-independent mTORC2-AKT axis in response to strong death stimuli. PMID:27849011

  7. Signal processing for an optical wide band data transmission system

    NASA Astrophysics Data System (ADS)

    Nakamura, M.; Leskovar, B.; Turko, B. T.

    1987-07-01

    The signal processing for an optical wide band transmission system using gallium arsenide (GaAs) digital integrated circuits and optical fibers has been investigated. Multiplexing, coding, synchronization, demultiplexing, and error checking at 780 Mbit/s data rates are described. Data storage in memory for linking to a computer is also considered. The design uses available GaAs and silicon components. The reliability of GaAs components is discussed as well as the layout and thermal considerations required for a high speed system.

  8. SERODS optical data storage with parallel signal transfer

    DOEpatents

    Vo-Dinh, Tuan

    2003-06-24

    Surface-enhanced Raman optical data storage (SERODS) systems having increased reading and writing speeds, that is, increased data transfer rates, are disclosed. In the various SERODS read and write systems, the surface-enhanced Raman scattering (SERS) data is written and read using a two-dimensional process called parallel signal transfer (PST). The various embodiments utilize laser light beam excitation of the SERODS medium, optical filtering, beam imaging, and two-dimensional light detection. Two- and three-dimensional SERODS media are utilized. The SERODS write systems employ either a different laser or a different level of laser power.

  9. SERODS optical data storage with parallel signal transfer

    DOEpatents

    Vo-Dinh, Tuan

    2003-09-02

    Surface-enhanced Raman optical data storage (SERODS) systems having increased reading and writing speeds, that is, increased data transfer rates, are disclosed. In the various SERODS read and write systems, the surface-enhanced Raman scattering (SERS) data is written and read using a two-dimensional process called parallel signal transfer (PST). The various embodiments utilize laser light beam excitation of the SERODS medium, optical filtering, beam imaging, and two-dimensional light detection. Two- and three-dimensional SERODS media are utilized. The SERODS write systems employ either a different laser or a different level of laser power.

  10. All-optical processing of optical-network signals using distributed feedback amplifiers

    NASA Astrophysics Data System (ADS)

    Maywar, Drew Nelson

    2001-06-01

    We study the nonlinear response and signal-processing capabilities of distributed feedback semiconductor optical amplifiers, and seek to advance their application to optical communication networks. Bistability occurring for optical signals tuned near a Bragg resonance is useful for switching and memory applications, but traditionally exhibits a limited wavelength range. We relax this constraint by varying the grating pitch along the length of the distributed feedback amplifier. A transfer-matrix method is developed for simulating this improvement, and for studying changes in the shape of the hysteresis curve throughout this wavelength range. We predict a new hysteresis-curve shape on reflection, and show how the grating-pitch variation can suppress or enhance this shape. Optical memory based on bistability is useful for sequential signal-processing applications, but previous control techniques operate with wavelengths only in the vicinity of the bistable-signal wavelength. We propose, model, and demonstrate control techniques via auxiliary optical signals that exhibit a very wide wavelength range. Set and reset signals vary the refractive index in opposite ways and shift the upward- and downward- switching thresholds, respectively, of the hysteresis curve through the holding-beam input power, which is kept constant. We develop a numerical model and an experimental system to investigate the performance of the all-optical flip-flop pertaining to speed, power, polarization, and response to back-to-back `set' pulses. We propose and numerically simulate a sequential processing application to fiberoptic networks-data format conversion from high-speed, return-to-zero signals to low-speed, non- return-to-zero signals. We demonstrate data-wavelength conversion to a signal wavelength of 1547 nm (in the vicinity of the Bragg wavelength) from initial data signals at 1306 nm, 1466 nm, and 1560 nm. This research demonstrates that cross- phase-modulation-based conversion using

  11. All-optical quantum random bit generation from intrinsically binary phase of parametric oscillators.

    PubMed

    Marandi, Alireza; Leindecker, Nick C; Vodopyanov, Konstantin L; Byer, Robert L

    2012-08-13

    We demonstrate a novel all-optical quantum random number generator (RNG) based on above-threshold binary phase state selection in a degenerate optical parametric oscillator (OPO). Photodetection is not a part of the random process, and no post processing is required for the generated bit sequence. We show that the outcome is statistically random with 99% confidence, and verify that the randomness is due to the phase of initiating photons generated through spontaneous parametric down conversion of the pump, with negligible contribution of classical noise sources. With the use of micro- and nanoscale OPO resonators, this technique offers a promise for simple, robust, and high-speed on-chip all-optical quantum RNGs.

  12. Intrinsic low pass filtering improves signal-to-noise ratio in critical-point flexure biosensors

    SciTech Connect

    Jain, Ankit; Alam, Muhammad Ashraful

    2014-08-25

    A flexure biosensor consists of a suspended beam and a fixed bottom electrode. The adsorption of the target biomolecules on the beam changes its stiffness and results in change of beam's deflection. It is now well established that the sensitivity of sensor is maximized close to the pull-in instability point, where effective stiffness of the beam vanishes. The question: “Do the signal-to-noise ratio (SNR) and the limit-of-detection (LOD) also improve close to the instability point?”, however remains unanswered. In this article, we systematically analyze the noise response to evaluate SNR and establish LOD of critical-point flexure sensors. We find that a flexure sensor acts like an effective low pass filter close to the instability point due to its relatively small resonance frequency, and rejects high frequency noise, leading to improved SNR and LOD. We believe that our conclusions should establish the uniqueness and the technological relevance of critical-point biosensors.

  13. Multiphoton microscopy using intrinsic signals for pharmacological studies in unstained cardiac and vascular tissue

    NASA Astrophysics Data System (ADS)

    Beaurepaire, Emmanuel; Boulesteix, Thierry; Pena, Ana-Maria; Pages, Nicole; Senni, Karim; Godeau, Gaston; Sauviat, Martin-Pierre; Schanne-Klein, Marie-Claire

    2005-03-01

    We report two novel applications of multiphoton microscopy for pharmacological studies of unstained cardiovascular tissue. First, we show that second harmonic generation (SHG) microscopy of unstained cardiac myocytes can be used to determine the sarcomere length with sub-resolution accuracy, owing to the remarkable contrast of the SHG signal originating from myosin filaments. A measurement precision of 20 nm is achieved, taking the sample variability into account. We used this technique to measure sarcomere contracture in the presence of saxitoxin, and results were in agreement with mechanical measurements of atrial tissue contracture. Second, we characterized multiphoton microscopy of intact unlabeled arteries. We performed simultaneous detection of two-photon-excited fluorescence (2PEF) from elastin laminae and SHG from collagen fibers upon 860 nm excitation. Combined 2PEF/SHG images provide a highly specific, micron scale description of the architecture of these two major components of the vessel wall. We used this methodology to study the effects of lindane (a pesticide) on the artery wall structure and evidenced structural alteration of the vessel morphology.

  14. Algorithmic processing of intrinsic signals in affixed transmission speckle analysis (ATSA) (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Ghijsen, Michael T.; Tromberg, Bruce J.

    2017-03-01

    Affixed Transmission Speckle Analysis (ATSA) is a method recently developed to measure blood flow that is based on laser speckle imaging miniaturized into a clip-on form factor the size of a pulse-oximeter. Measuring at a rate of 250 Hz, ATSA is capable or obtaining the cardiac waveform in blood flow data, referred to as the Speckle-Plethysmogram (SPG). ATSA is also capable of simultaneously measuring the Photoplethysmogram (PPG), a more conventional signal related to light intensity. In this work we present several novel algorithms for extracting physiologically relevant information from the combined SPG-PPG waveform data. First we show that there is a slight time-delay between the SPG and PPG that can be extracted computationally. Second, we present a set of frequency domain algorithms that measure harmonic content on pulse-by-pulse basis for both the SPG and PPG. Finally, we apply these algorithms to data obtained from a set of subjects including healthy controls and individuals with heightened cardiovascular risk. We hypothesize that the time-delay and frequency content are correlated with cardiovascular health; specifically with vascular stiffening.

  15. Signal-carrier interleaved optical OFDM for direct detection optical communication.

    PubMed

    Chen, Xi; Che, Di; Li, An; He, Jiayuan; Shieh, William

    2013-12-30

    We propose signal-carrier interleaved (SCI) optical OFDM for direct detected transmission systems. Such a scheme can be considered as a variation of self-coherent detection where the carrier and signal are supplied at the transmitter and extracted at the receiver for coherent-like detection. This provides high OSNR sensitivity while maintaining very low carrier-to-signal power ratio (CSR). Our experiment results show that with 0 dB CSR, 43.2 Gb/s 16 QAM OFDM signal can be successfully delivered over 80 km standard single mode fiber (SSMF) with 24 dB OSNR requirements at 7% FEC limit.

  16. Prediction of intrinsically disordered regions in proteins using signal processing methods: application to heat-shock proteins.

    PubMed

    Vojisavljevic, Vuk; Pirogova, Elena

    2016-12-01

    Heat-shock protein (HSP)-based immunotherapy is believed to be a promising area of development for cancer treatment as such therapy is characterized by a unique approach to every tumour. It was shown that by inhibition of HSPs it is possible to induce apoptotic cell death in cancer cells. Interestingly, there are a great number of disordered regions in proteins associated with cancer, cardiovascular and neurodegenerative diseases, signalling, and diabetes. HSPs and some specific enzymes were shown to have these disordered regions in their primary structures. The experimental studies of HSPs confirmed that their intrinsically disordered (ID) regions are of functional importance. These ID regions play crucial roles in regulating the specificity of interactions between dimer complexes and their interacting partners. Because HSPs are overexpressed in cancer, predicting the locations of ID regions and binding sites in these proteins will be important for developing novel cancer therapeutics. In our previous studies, signal processing methods have been successfully used for protein structure-function analysis (i.e. for determining functionally important amino acids and the locations of protein active sites). In this paper, we present and discuss a novel approach for predicting the locations of ID regions in the selected cancer-related HSPs.

  17. Using sum rules to guide experiential and theoretical studies of the intrinsic nonlinear-optical susceptibility of organic molecules

    NASA Astrophysics Data System (ADS)

    Zhou, Juefei

    This dissertation combines theoretical and experimental studies of organic molecules to understand light-matter interactions with the goal of making more efficient nonlinear-optical molecules. We use a finite element method to numerically calculate and optimize the nonlinear-optical susceptibilities of 1-dimensional molecules, which resulted in a new paradigm for fabricating molecules with better nonlinear properties. This approach was used as a guide by researchers to identify and characterize a record-high intrinsic hyperpolarizability. Using the results of a sum rule analysis, we propose a new method for modeling the nonlinear-optical spectra of molecules. We apply our theory to the two-photon absorption cross section of the Air Force dye called AF455, and find that it is consistent with our measurements. The properties of the first two excited states of AF455 determined with a combination of linear absorption spectroscopy and hyper-Rayleigh scattering measurements are sufficient to predict, within experimental uncertainty, the full two-photon absorption spectrum.

  18. Natural Optical Activity of Chiral Epoxides: the Influence of Structure and Environment on the Intrinsic Chiroptical Response

    NASA Astrophysics Data System (ADS)

    Lemler, Paul M.; Craft, Clayton L.; Vaccaro, Patrick

    2017-06-01

    Chiral epoxides built upon nominally rigid frameworks that incorporate aryl substituents have been shown to provide versatile backbones for asymmetric syntheses designed to generate novel pharmaceutical and catalytic agents. The ubiquity of these species has motivated the present studies of their intrinsic (solvent-free) circular birefringence (CB), the measurement of which serves as a benchmark for quantum-chemical predictions of non-resonant chiroptical behavior and as a beachhead for understanding the often-pronounced mediation of such properties by environmental perturbations (e.g., solvation). The optical rotatory dispersion (or wavelength-resolved CB) of (R)-styrene oxide (R-SO) and (S,S)-phenylpropylene oxide (S-PPO) have been interrogated under ambient solvated and isolated conditions, where the latter efforts exploited the ultrasensitive techniques of cavity ring-down polarimetry. Both of the targeted systems display marked solvation effects as evinced by changes the magnitude and (in the case of R-SO) the sign of the extracted specific optical rotation, with the anomalously large response evoked from S-PPO distinguishing it from other members of the epoxide family. Linear-response calculations of dispersive optical activity have been performed at both density-functional and coupled-cluster levels of theory to unravel the structural and electronic origins of experimental findings, thereby suggesting the possible involvement of hindered torsional motion along dihedral coordinates adjoining phenyl and epoxide moieties.

  19. High-speed optical coherence tomography signal processing on GPU

    NASA Astrophysics Data System (ADS)

    Li, Xiqi; Shi, Guohua; Zhang, Yudong

    2011-01-01

    The signal processing speed of spectral domain optical coherence tomography (SD-OCT) has become a bottleneck in many medical applications. Recently, a time-domain interpolation method was proposed. This method not only gets a better signal-to noise ratio (SNR) but also gets a faster signal processing time for the SD-OCT than the widely used zero-padding interpolation method. Furthermore, the re-sampled data is obtained by convoluting the acquired data and the coefficients in time domain. Thus, a lot of interpolations can be performed concurrently. So, this interpolation method is suitable for parallel computing. An ultra-high optical coherence tomography signal processing can be realized by using graphics processing unit (GPU) with computer unified device architecture (CUDA). This paper will introduce the signal processing steps of SD-OCT on GPU. An experiment is performed to acquire a frame SD-OCT data (400A-lines×2048 pixel per A-line) and real-time processed the data on GPU. The results show that it can be finished in 6.208 milliseconds, which is 37 times faster than that on Central Processing Unit (CPU).

  20. Optical beam deflection signal from a single microparticle

    NASA Astrophysics Data System (ADS)

    Wu, Jiaqi; Kitamori, Takehiko; Sawada, Tsuguo

    1990-07-01

    The optical beam deflection (OBD) method was applied to the measurement of a single microparticle, and the signal from one resin microparticle of 200-600 μm in diameter could be detected. Based on the frequency characteristics and size dependence of the OBD signal, this method was found to be more sensitive for a smaller particle, and more effective than the photoacoustic method. Theoretical considerations showed that these characteristics were attributable to the enhancement of the temperature field gradient due to the curvature of the microparticle.

  1. Intrinsic Differences in the Inner Jets of High and Low Optically Polarized Radio Quasars

    NASA Technical Reports Server (NTRS)

    Lister, M.; Smith, P.

    2000-01-01

    We have conducted a high-resolution polarization study with the VLBA at 22 and 43 GHz to look for differences in the parsec-scale magnetic field structures of 18 high- and low-optically polarized, compact radio-loud quasars (HPQs and LPRQs, respectively).

  2. Intrinsic artefacts in optical oxygen sensors--how reliable are our measurements?

    PubMed

    Lehner, Philipp; Staudinger, Christoph; Borisov, Sergey M; Regensburger, Johannes; Klimant, Ingo

    2015-03-02

    Optical oxygen sensing is of broad interest in many areas of research, such as medicine, food processing, and micro- and marine biology. The operation principle of optical oxygen sensors is well established and these sensors are routinely employed in lab and field experiments. Ultratrace oxygen sensors, which enable measurements in the sub-nanomolar region (dissolved oxygen), are becoming increasingly important. Such sensors prominently exhibit phenomena that complicate calibration and measurements. However, these phenomena are not constrained to ultratrace sensors; rather, these effects are inherent to the way optical oxygen sensors work and may influence any optical oxygen measurement when certain conditions are met. This scenario is especially true for applications that deal with high-excitation light intensities, such as microscopy and microfluidic applications. Herein, we present various effects that we could observe in our studies with ultratrace oxygen sensors and discuss the reasons for their appearance, the mechanism by which they influence measurements, and how to best reduce their impact. The phenomena discussed are oxygen photoconsumption in the sensor material; depletion of the dye ground state by high-excitation photon-flux values, which can compromise both intensity and ratiometric-based measurements; triplet-triplet annihilation; and singlet-oxygen accumulation, which affects measurements at very low oxygen concentrations. © 2015 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  3. Optical study on intrinsic exciton states in high-quality CH3NH3PbBr3 single crystals

    NASA Astrophysics Data System (ADS)

    Thu Ha Do, T.; Granados del Águila, A.; Cui, Chao; Xing, Jun; Ning, Zhijun; Xiong, Qihua

    2017-08-01

    Organolead halide perovskites have emerged as potential building blocks for photovoltaic and optoelectronic devices. Yet the underlying fundamental physics is not well understood. There is lack of agreement on the electronic band structures and binding energies of coupled electron-hole pairs (excitons), which drive the photophysical processes. In this work, we conducted temperature-dependent reflectance and photoluminescence experiments on high-quality CH3NH3PbBr3 single crystals. Two direct optical transitions corresponding to intrinsic free-excitons are clearly resolved, showing excellent consistence between the low-temperature (T =10 K) reflectance and photoluminescence spectra. Remarkably, the excitons have different binding energies and behave oppositely with temperature, suggesting distinctive origins. Moreover, the asymmetric photoluminescence profile is counterintuitively dominated by the high-energy exciton that is explained by a long relaxation time between levels and by the favorable generation rate of electron-hole pairs at the high-energy band. Our study opens access to the intrinsic properties of CH3NH3PbBr3 and sheds light to reconcile the large range of binding energies reported on these emergent direct band-gap semiconductors.

  4. Signal filtering algorithm for depth-selective diffuse optical topography

    NASA Astrophysics Data System (ADS)

    Fujii, M.; Nakayama, K.

    2009-03-01

    A compact filtered backprojection algorithm that suppresses the undesirable effects of skin circulation for near-infrared diffuse optical topography is proposed. Our approach centers around a depth-selective filtering algorithm that uses an inverse problem technique and extracts target signals from observation data contaminated by noise from a shallow region. The filtering algorithm is reduced to a compact matrix and is therefore easily incorporated into a real-time system. To demonstrate the validity of this method, we developed a demonstration prototype for depth-selective diffuse optical topography and performed both computer simulations and phantom experiments. The results show that the proposed method significantly suppresses the noise from the shallow region with a minimal degradation of the target signal.

  5. Toward optical signal processing using photonic reservoir computing.

    PubMed

    Vandoorne, Kristof; Dierckx, Wouter; Schrauwen, Benjamin; Verstraeten, David; Baets, Roel; Bienstman, Peter; Van Campenhout, Jan

    2008-07-21

    We propose photonic reservoir computing as a new approach to optical signal processing in the context of large scale pattern recognition problems. Photonic reservoir computing is a photonic implementation of the recently proposed reservoir computing concept, where the dynamics of a network of nonlinear elements are exploited to perform general signal processing tasks. In our proposed photonic implementation, we employ a network of coupled Semiconductor Optical Amplifiers (SOA) as the basic building blocks for the reservoir. Although they differ in many key respects from traditional software-based hyperbolic tangent reservoirs, we show using simulations that such a photonic reservoir can outperform traditional reservoirs on a benchmark classification task. Moreover, a photonic implementation offers the promise of massively parallel information processing with low power and high speed.

  6. Multi-functional optical signal processing using optical spectrum control circuit

    NASA Astrophysics Data System (ADS)

    Hayashi, Shuhei; Ikeda, Tatsuhiko; Mizuno, Takayuki; Takahashi, Hiroshi; Tsuda, Hiroyuki

    2015-02-01

    Processing ultra-fast optical signals without optical/electronic conversion is in demand and time-to-space conversion has been proposed as an effective solution. We have designed and fabricated an arrayed-waveguide grating (AWG) based optical spectrum control circuit (OSCC) using silica planar lightwave circuit (PLC) technology. This device is composed of an AWG, tunable phase shifters and a mirror. The principle of signal processing is to spatially decompose the signal's frequency components by using the AWG. Then, the phase of each frequency component is controlled by the tunable phase shifters. Finally, the light is reflected back to the AWG by the mirror and synthesized. Amplitude of each frequency component can be controlled by distributing the power to high diffraction order light. The spectral controlling range of the OSCC is 100 GHz and its resolution is 1.67 GHz. This paper describes equipping the OSCC with optical coded division multiplex (OCDM) encoder/decoder functionality. The encoding principle is to apply certain phase patterns to the signal's frequency components and intentionally disperse the signal. The decoding principle is also to apply certain phase patterns to the frequency components at the receiving side. If the applied phase pattern compensates the intentional dispersion, the waveform is regenerated, but if the pattern is not appropriate, the waveform remains dispersed. We also propose an arbitrary filter function by exploiting the OSCC's amplitude and phase control attributes. For example, a filtered optical signal transmitted through multiple optical nodes that use the wavelength multiplexer/demultiplexer can be equalized.

  7. Intrinsic reduction the depolarization loss in electro-optical Q-switched laser using a rectangular KD*P crystal

    NASA Astrophysics Data System (ADS)

    Yin, Xingliang; Jiang, Menghua; Sun, Zhe; Hui, Yongling; Lei, Hong; Li, Qiang

    2017-09-01

    We presented the first demonstration of a new structure KD*P crystal as electro-optic switch, in which the thermal depolarization loss was intrinsically reduced. The thermally induced birefringence and depolarization of both cylindrical and rectangular crystalline structure were simulated. The higher pulse energy or average power output was achieved in the diode pumped E-O Q-switched laser using a rectangular KD*P crystal. At the repetition rate of 100 Hz, the maximum average output power was 27.2 W at 145 A pump current, corresponding to the pulse energy was 272 mJ with pulse width of 65 ns and the beam quality of M2=20.4. Comparing the highest average power or corresponding single pulse energy, the laser with the rectangular KD*P crystal was two times of the laser with the traditional cylindrical KD*P crystal.

  8. Optical communication system performance with tracking error induced signal fading.

    NASA Technical Reports Server (NTRS)

    Tycz, M.; Fitzmaurice, M. W.; Premo, D. A.

    1973-01-01

    System performance is determined for an optical communication system using noncoherent detection in the presence of tracking error induced signal fading assuming (1) binary on-off modulation (OOK) with both fixed and adaptive threshold receivers, and (2) binary polarization modulation (BPM). BPM is shown to maintain its inherent 2- to 3-dB advantage over OOK when adaptive thresholding is used, and to have a substantially greater advantage when the OOK system is restricted to a fixed decision threshold.

  9. Electro-Optic Characterisation of Extremely Wide Bandwidth Electrical Signals

    DTIC Science & Technology

    1993-02-01

    In this report an ultrafast electro - optic sampling system suitable for applications such as device characterisation is described. The aperture time of the sampler is calculated to be about 290 fs, implying an attainable device bandwidth in excess of 300 GHz. The sampler was characterised using a test pulse with approximately 12 GHz of frequency content, and the results compared to those obtained from an 18 GHz digital sampling oscilloscope. Signal Processing, Bandwidth, Frequencies, Oscilloscopes.

  10. Optical communication system performance with tracking error induced signal fading.

    NASA Technical Reports Server (NTRS)

    Tycz, M.; Fitzmaurice, M. W.; Premo, D. A.

    1973-01-01

    System performance is determined for an optical communication system using noncoherent detection in the presence of tracking error induced signal fading assuming (1) binary on-off modulation (OOK) with both fixed and adaptive threshold receivers, and (2) binary polarization modulation (BPM). BPM is shown to maintain its inherent 2- to 3-dB advantage over OOK when adaptive thresholding is used, and to have a substantially greater advantage when the OOK system is restricted to a fixed decision threshold.

  11. Study of Photochromic Materials for Use in Optical Signal Processing.

    DTIC Science & Technology

    1987-11-01

    LDFP 07 C6 11. TITLE (kIclude Security Classification) STUDY OF PHOTOCHROMIC MATERIALS FOR USE IN OPZfCAL SIGNAL PROCESSING 12. PERSONAL AUTHOR(S) Dr...the feasibility of using photochromic materials for programmable spatial filters and optical data storage/ applications. Write and erase times...Mercuay Dithizonate 35 V. General Experimental Behavior of Photochromic Materials 39 VI. Kinetics of the Relaxation Reaction 44 VII. Dependence of the

  12. Embodiment of Learning in Electro-Optical Signal Processors.

    PubMed

    Hermans, Michiel; Antonik, Piotr; Haelterman, Marc; Massar, Serge

    2016-09-16

    Delay-coupled electro-optical systems have received much attention for their dynamical properties and their potential use in signal processing. In particular, it has recently been demonstrated, using the artificial intelligence algorithm known as reservoir computing, that photonic implementations of such systems solve complex tasks such as speech recognition. Here, we show how the backpropagation algorithm can be physically implemented on the same electro-optical delay-coupled architecture used for computation with only minor changes to the original design. We find that, compared to when the backpropagation algorithm is not used, the error rate of the resulting computing device, evaluated on three benchmark tasks, decreases considerably. This demonstrates that electro-optical analog computers can embody a large part of their own training process, allowing them to be applied to new, more difficult tasks.

  13. Embodiment of Learning in Electro-Optical Signal Processors

    NASA Astrophysics Data System (ADS)

    Hermans, Michiel; Antonik, Piotr; Haelterman, Marc; Massar, Serge

    2016-09-01

    Delay-coupled electro-optical systems have received much attention for their dynamical properties and their potential use in signal processing. In particular, it has recently been demonstrated, using the artificial intelligence algorithm known as reservoir computing, that photonic implementations of such systems solve complex tasks such as speech recognition. Here, we show how the backpropagation algorithm can be physically implemented on the same electro-optical delay-coupled architecture used for computation with only minor changes to the original design. We find that, compared to when the backpropagation algorithm is not used, the error rate of the resulting computing device, evaluated on three benchmark tasks, decreases considerably. This demonstrates that electro-optical analog computers can embody a large part of their own training process, allowing them to be applied to new, more difficult tasks.

  14. How Intrinsic Molecular Dynamics Control Intramolecular Communication in Signal Transducers and Activators of Transcription Factor STAT5

    PubMed Central

    Langenfeld, Florent; Guarracino, Yann; Arock, Michel; Trouvé, Alain; Tchertanov, Luba

    2015-01-01

    Signal Transducer and Activator of Transcription STAT5 is a key mediator of cell proliferation, differentiation and survival. While STAT5 activity is tightly regulated in normal cells, its constitutive activation directly contributes to oncogenesis and is associated with a broad range of hematological and solid tumor cancers. Therefore the development of compounds able to modulate pathogenic activation of this protein is a very challenging endeavor. A crucial step of drug design is the understanding of the protein conformational features and the definition of putative binding site(s) for such modulators. Currently, there is no structural data available for human STAT5 and our study is the first footprint towards the description of structure and dynamics of this protein. We investigated structural and dynamical features of the two STAT5 isoforms, STAT5a and STAT5b, taken into account their phosphorylation status. The study was based on the exploration of molecular dynamics simulations by different analytical methods. Despite the overall folding similarity of STAT5 proteins, the MD conformations display specific structural and dynamical features for each protein, indicating first, sequence-encoded structural properties and second, phosphorylation-induced effects which contribute to local and long-distance structural rearrangements interpreted as allosteric event. Further examination of the dynamical coupling between distant sites provides evidence for alternative profiles of the communication pathways inside and between the STAT5 domains. These results add a new insight to the understanding of the crucial role of intrinsic molecular dynamics in mediating intramolecular signaling in STAT5. Two pockets, localized in close proximity to the phosphotyrosine-binding site and adjacent to the channel for communication pathways across STAT5, may constitute valid targets to develop inhibitors able to modulate the function-related communication properties of this signaling

  15. Method and means for detecting optically transmitted signals and establishing optical interference pattern between electrodes

    DOEpatents

    Kostenbauder, Adnah G.

    1988-01-01

    A photodetector for detecting signal pulses transmitted in an optical carrier signal relies on the generation of electron-hole pairs and the diffusion of the generated electrons and holes to the electrodes on the surface of the semiconductor detector body for generating photovoltaic pulses. The detector utilizes the interference of optical waves for generating an electron-hole grating within the semiconductor body, and, by establishing an electron-hole pair maximum at one electrode and a minimum at the other electrode, a detectable voltaic pulse is generated across the electrode.

  16. Method and means for detecting optically transmitted signals and establishing optical interference pattern between electrodes

    DOEpatents

    Kostenbauder, A.G.

    1988-06-28

    A photodetector for detecting signal pulses transmitted in an optical carrier signal relies on the generation of electron-hole pairs and the diffusion of the generated electrons and holes to the electrodes on the surface of the semiconductor detector body for generating photovoltaic pulses. The detector utilizes the interference of optical waves for generating an electron-hole grating within the semiconductor body, and, by establishing an electron-hole pair maximum at one electrode and a minimum at the other electrode, a detectable voltaic pulse is generated across the electrode. 4 figs.

  17. Coherent optical array receiver for PPM signals under atmospheric turbulence

    NASA Astrophysics Data System (ADS)

    Munoz Fernandez, Michela

    The performance of a coherent free-space optical communications system operating in the presence of turbulence is investigated. Maximum Likelihood Detection techniques are employed to optimally detect Pulse Position Modulated signals with a focal-plane detector array and to reconstruct the turbulence-degraded signals. Laboratory equipment and experimental setup used to carry out these experiments at the Jet Propulsion Laboratory are described. The key components include two lasers operating at 1064 nm wavelength for use with coherent detection, a 16 element (4 X 4) InGaAs focal-plane detector array, and a data-acquisition and signal-processing assembly needed to sample and collect the data and analyze the results. The detected signals are combined using the least-mean-square (LMS) algorithm. In the first part of the experimental results we show convergence of the algorithm for experimentally obtained signal tones in the presence of atmospheric turbulence. The second part of the experimental results shows adaptive combining of experimentally obtained heterodyned pulse position modulated (PPM) signals with pulse-to-pulse coherence in the presence of simulated spatial distortions resembling atmospheric turbulence. The adaptively combined PPM signals are phased up via an LMS algorithm suitably optimized to operate with PPM in the presence of additive shot noise. A convergence analysis of the algorithm is presented, and results with both computer-simulated and experimentally obtained PPM signals are analyzed. The third part of the experimental results, in which the main goal of this thesis is achieved, includes an investigation of the performance of the Coherent Optical Receiver Experiment (CORE) at JPL. Bit Error Rate (BER) results are presented for single and multichannel optical receivers where quasi shot noise-limited performance is achieved under simulated turbulence conditions using noncoherent postdetection processing techniques. Theoretical BER expressions are

  18. Removal of pedestals and directional ambiguity of optical anemometer signals.

    PubMed

    Durst, F; Zaré, M

    1974-11-01

    Laser Doppler anemometry permits, in principle, the measurement of both magnitude and direction of components of a particle's velocity vector. Most exiting anemometers, however, permit measurements only with a directional ambiguity of 180 degrees , resulting in errors in certain flow fields. Available methods of eliminating the directional ambiguity of Laser Doppler anemometers are reviewed, covering frequency shifting of the incident and scattered light beams, the use of beams with different polarization properties, and employment of multicolor laser beams. The advantages and disadvantages of existing methods are summarized, and suggestions for alterations are made. Different techniques used to remove the pedestal of laser Doppler anemometer signals are also reviewed. Optical techniques should be employed in any advanced optical anemometer system to avoid dynamic range limitations by electronic bandpass filters. Suggestions are made for advanced optical anemometers employing multielement avalanche photodiodes that can be used for simultaneous measurements of two velocity components. These anemometers incorporate devices to sense the direction of the velocity components and to eliminate optically the pedestal of laser Doppler signals.

  19. Intrinsic carrier multiplication efficiency in bulk Si crystals evaluated by optical-pump/terahertz-probe spectroscopy

    SciTech Connect

    Yamashita, G.; Nagai, M. E-mail: ashida@mp.es.osaka-u.ac.jp; Ashida, M. E-mail: ashida@mp.es.osaka-u.ac.jp; Matsubara, E.; Kanemitsu, Y.

    2014-12-08

    We estimated the carrier multiplication efficiency in the most common solar-cell material, Si, by using optical-pump/terahertz-probe spectroscopy. Through close analysis of time-resolved data, we extracted the exact number of photoexcited carriers from the sheet carrier density 10 ps after photoexcitation, excluding the influences of spatial diffusion and surface recombination in the time domain. For incident photon energies greater than 4.0 eV, we observed enhanced internal quantum efficiency due to carrier multiplication. The evaluated value of internal quantum efficiency agrees well with the results of photocurrent measurements. This optical method allows us to estimate the carrier multiplication and surface recombination of carriers quantitatively, which are crucial for the design of the solar cells.

  20. Intrinsic optical conductivity of a {{\\rm{C}}}_{2v} symmetric topological insulator

    NASA Astrophysics Data System (ADS)

    Sengupta, Parijat; Matsubara, Masahiko; Bellotti, Enrico; Shi, Junxia

    2017-07-01

    In this work we analytically investigate the longitudinal optical conductivity of the {{{C}}}2v symmetric topological insulator. The conductivity expressions at T = 0 are derived using the Kubo formula and expressed as a function of the ratio of the Dresselhaus and Rashba parameters that characterize the low-energy Hamiltonian. We find that the longitudinal inter-band conductivity vanishes when Dresselhaus and Rashba parameters are equal in strength, also called the persistent spin helix state. The calculations are extended to obtain the frequency-dependent real and imaginary components of the optical conductivity for the topological Kondo insulator SmB6 which exhibits {{{C}}}2v symmetric and anisotropic Dirac cones hosting topological states at \\overline{X} point on the surface Brillouin zone.

  1. Electrically controlled nonlinear optical generation and signal processing in plasmonic metamaterials (Conference Presentation)

    NASA Astrophysics Data System (ADS)

    Cai, Wenshan

    2016-09-01

    Metamaterials have offered not only the unprecedented opportunity to generate unconventional electromagnetic properties that are not found in nature, but also the exciting potential to create customized nonlinear media with tailored high-order effects. Two particularly compelling directions of current interests are active metamaterials, where the optical properties can be purposely manipulated by external stimuli, and nonlinear metamaterials, which enable intensity-dependent frequency conversion of light. By exploring the interaction of these two directions, we leverage the electrical and optical functions simultaneously supported in nanostructured metals and demonstrate electrically-controlled nonlinear processes from photonic metamaterials. We show that a variety of nonlinear optical phenomena, including the wave mixing and the optical rectification, can be purposely modulated by applied voltage signals. In addition, electrically-induced and voltage-controlled nonlinear effects facilitate us to demonstrate the backward phase matching in a negative index material, a long standing prediction in nonlinear metamaterials. Other results to be covered in this talk include photon-drag effect in plasmonic metamaterials and ion-assisted nonlinear effects from metamaterials in electrolytes. Our results reveal a grand opportunity to exploit optical metamaterials as self-contained, dynamic electrooptic systems with intrinsically embedded electrical functions and optical nonlinearities. Reference: L. Kang, Y. Cui, S. Lan, S. P. Rodrigues, M. L. Brongersma, and W. Cai, Nature Communications, 5, 4680 (2014). S. P. Rodrigues and W.Cai, Nature Nanotechnology, 10, 387 (2015). S. Lan, L. Kang, D. T. Schoen, S. P. Rodrigues, Y. Cui, M. L. Brongersma, and W. Cai, Nature Materials, 14, 807 (2015).

  2. Coherent Detection of High-Rate Optical PPM Signals

    NASA Technical Reports Server (NTRS)

    Vilnrotter, Victor; Fernandez, Michela Munoz

    2006-01-01

    A method of coherent detection of high-rate pulse-position modulation (PPM) on a received laser beam has been conceived as a means of reducing the deleterious effects of noise and atmospheric turbulence in free-space optical communication using focal-plane detector array technologies. In comparison with a receiver based on direct detection of the intensity modulation of a PPM signal, a receiver based on the present method of coherent detection performs well at much higher background levels. In principle, the coherent-detection receiver can exhibit quantum-limited performance despite atmospheric turbulence. The key components of such a receiver include standard receiver optics, a laser that serves as a local oscillator, a focal-plane array of photodetectors, and a signal-processing and data-acquisition assembly needed to sample the focal-plane fields and reconstruct the pulsed signal prior to detection. The received PPM-modulated laser beam and the local-oscillator beam are focused onto the photodetector array, where they are mixed in the detection process. The two lasers are of the same or nearly the same frequency. If the two lasers are of different frequencies, then the coherent detection process is characterized as heterodyne and, using traditional heterodyne-detection terminology, the difference between the two laser frequencies is denoted the intermediate frequency (IF). If the two laser beams are of the same frequency and remain aligned in phase, then the coherent detection process is characterized as homodyne (essentially, heterodyne detection at zero IF). As a result of the inherent squaring operation of each photodetector, the output current includes an IF component that contains the signal modulation. The amplitude of the IF component is proportional to the product of the local-oscillator signal amplitude and the PPM signal amplitude. Hence, by using a sufficiently strong local-oscillator signal, one can make the PPM-modulated IF signal strong enough to

  3. Probing the intrinsic optical Bloch-mode emission from a 3D photonic crystal

    NASA Astrophysics Data System (ADS)

    Hsieh, Mei-Li; Bur, James A.; Du, Qingguo; John, Sajeev; Lin, Shawn-Yu

    2016-10-01

    We report experimental observation of intrinsic Bloch-mode emission from a 3D tungsten photonic crystal at low thermal excitation. After the successful removal of conventional metallic emission (normal emission), it is possible to make an accurate comparison of the Bloch-mode and the normal emission. For all biases, we found that the emission intensity of the Bloch-mode is higher than that of the normal emission. The Bloch-mode emission also exhibits a slower dependence on (\\hslash ω /{k}bT) than that of the normal emission. The observed higher emission intensity and a different T-dependence is attributed to Bloch-mode assisted emission where emitters have been located into a medium having local density of states different than the isotropic case. Furthermore, our finite-difference time-domain (FDTD) simulation shows the presence of localized spots at metal-air boundaries and corners, having intense electric field. The enhanced plasmonic field and local non-equilibrium could induce a strong thermally stimulated emission and may be the cause of our unusual observation.

  4. Causal evidence that intrinsic beta-frequency is relevant for enhanced signal propagation in the motor system as shown through rhythmic TMS

    PubMed Central

    Romei, Vincenzo; Bauer, Markus; Brooks, Joseph L.; Economides, Marcos; Penny, Will; Thut, Gregor; Driver, Jon; Bestmann, Sven

    2016-01-01

    Correlative evidence provides support for the idea that brain oscillations underpin neural computations. Recent work using rhythmic stimulation techniques in humans provide causal evidence but the interactions of these external signals with intrinsic rhythmicity remain unclear. Here, we show that sensorimotor cortex follows externally applied rhythmic TMS (rTMS) stimulation in the beta-band but that the elicited responses are strongest at the intrinsic individual beta peak frequency. While these entrainment effects are of short duration, even subthreshold rTMS pulses propagate through the network and elicit significant cortico-spinal coupling, particularly when stimulated at the individual beta-frequency. Our results show that externally enforced rhythmicity interacts with intrinsic brain rhythms such that the individual peak frequency determines the effect of rTMS. The observed downstream spinal effect at the resonance frequency provides evidence for the causal role of brain rhythms for signal propagation. PMID:26584867

  5. Applications of all optical signal processing for advanced optical modulation formats

    NASA Astrophysics Data System (ADS)

    Nuccio, Scott R.

    Increased data traffic demands, along with a continual push to minimize cost per bit, have recently motivated a paradigm shift away from traditional on-off keying (OOK) fiber transmission links towards systems utilizing more advanced modulation formats. In particular, modulation formats that utilize the phase of the optical signal, including differential phase shift keying (DPSK) and differential quadrature phase shift keying (DQPSK) along with polarization multiplexing (Pol-MUX), have recently emerged as the most popular means for transmitting information over long-haul and ultra-long haul fiber transmission systems. DPSK is motivated by an increase in receiver sensitivity compared to traditional OOK. DQPSK is motivated by a doubling of the spectral efficiency, along with increased tolerance to dispersion and nonlinear distortions. Coherent communications has also emerged as a primary means of transmitting and receiving optical data due to its support of formats that utilize both phase and amplitude to further increase the spectral efficiency (bits/sec/Hz) of the optical channel, including quadrature amplitude modulation (QAM). Polarization multiplexing of channels is a straight forward method to allow two channels to share the same wavelength by propagating on orthogonal polarization axis and is easily supported in coherent systems where the polarization tracking can be performed in the digital domain. Furthermore, the forthcoming IEEE 100 Gbit/s Ethernet Standard, 802.3ba, provides greater bandwidth, higher data rates, and supports a mixture of modulation formats. In particular, Pol-MUX (D)QPSK has grown in interest as the high spectral efficiency allows for 100 Gbit/s transmission while still occupying the current 50 GHz/channel allocation of current 10 Gbit/s OOK fiber systems. In this manner, 100 Gbit/s transfer speeds using current fiber links, amplifiers, and filters may be possible. In addition to advanced modulation formats, it is expected that optical

  6. Multichannel optical signal processing using sampled fiber Bragg gratings

    NASA Astrophysics Data System (ADS)

    Zhang, Guiju; Wang, Chinhua; Zhu, Xiaojun

    2008-12-01

    Sampled and linearly chirped fiber Bragg gratings provide multiple wavelength responses and linear group delays (constant dispersions) within each of the wavelength channels. We show that the sampled and chirped fiber Bragg gratings can be used to perform multiwavelength signal processing. In particular, we demonstrate, by numerical simulation, their use for performing real-time Fourier transform (RTFT) and for pulse repetition rate multiplication (PRRM) simultaneously over multiple wavelength channels. To present how the sampled fiber Bragg gratings perform the multichannel optical signal processing, a 9-channel sampled fiber grating with 100GHz channel spacing was designed and the effect of ripples in both amplitude and the group delay channel on the performance of the signal processing was examined and discussed.

  7. Soft demodulation to the optical pulse position modulated signals

    NASA Astrophysics Data System (ADS)

    Zhou, Tian-hua; Chen, Wei-biao

    2009-07-01

    The optical Pulse Position Modulation (PPM) is applied widely in Free Space Optical communication (FSO) with the low average power and the high peak power. The transmitted PPM information depends on the location of the coming optical pulse signals in fixed period. Both receiver and transmitter should been kept in time slot synchronization and frame synchronization in demodulation. Because the channel is very complex, the received optical pulse width will be stretched randomly. We design and realize one digital PPM modulation receiver with high sensitivity using the technology of PMT, A/D converter, and DSP. It is suitable to the total digital optical receiver with random time slots and random pulse width. The paper will mainly discuss the realization of the soft demodulation behind A/D converter. The key of PPM digital soft modulation is the establishment of the synchronization that involves the segment synchronization, the fame synchronization and the bit synchronization. The synchronization can be obtained by seeking for the frame head in data frames. Based on the estimation of received waveform characteristics, we adopt a matched filter without the best factors firstly. Thereafter, their errors will be self-adapted while finding the synchronization head. Considering the real-time need, we choose the reduced mode of maximum likelihood function judgment finally. In the experiments, results with high sensitivity and low bit error rate have been achieved.

  8. All-optical signal processing at 10 GHz using a photonic crystal molecule

    SciTech Connect

    Combrié, Sylvain; Lehoucq, Gaëlle; Junay, Alexandra; De Rossi, Alfredo; Malaguti, Stefania; Bellanca, Gaetano; Trillo, Stefano; Ménager, Loic; Peter Reithmaier, Johann

    2013-11-04

    We report on 10 GHz operation of an all-optical gate based on an Indium Phosphide Photonic Crystal Molecule. Wavelength conversion and all-optical mixing of microwave signals are demonstrated using the 2 mW output of a mode locked diode laser. The spectral separation of the optical pump and signal is crucial in suppressing optical cross-talk.

  9. Many-Body Effects on Optical Carrier Cooling in Intrinsic Semiconductors at Low Lattice Temperatures

    DTIC Science & Technology

    2008-07-11

    Fg, 78.40.Fy, 78.55.Cr I . INTRODUCTION It is well known that the optical properties of an atomic vapor are essentially determined by the properties...equal temperatures in the papers by Rupper et al.12 and by Sheik- Bahae et al.13 for both carriers and phonons cannot be applied to quasiequilibrium...2 + i 0 − 2e2 2 0 b 0 dk k2 rvck 21 − fek − fhk Eek + Ehk + i 02 − Eek + Ehk2 , 4 where 0 is the homogeneous

  10. Intrinsic exciton-state mixing and nonlinear optical properties in transition metal dichalcogenide monolayers

    NASA Astrophysics Data System (ADS)

    Glazov, M. M.; Golub, L. E.; Wang, G.; Marie, X.; Amand, T.; Urbaszek, B.

    2017-01-01

    Optical properties of transition metal dichalcogenides monolayers are controlled by Wannier-Mott excitons forming a series of 1 s ,2 s ,2 p ,... hydrogen-like states. We develop the theory of the excited excitonic states energy spectrum fine structure. We predict that p - and s -shell excitons are mixed due to the specific D3 h point symmetry of the transition metal dichalcogenide monolayers. Hence, both s - and p -shell excitons are active in both single- and two-photon processes, providing an efficient mechanism of second harmonic generation. The corresponding contribution to the nonlinear susceptibility is calculated.

  11. Simplified optical fiber RGB system in evaluating intrinsic quality of Sala mango

    NASA Astrophysics Data System (ADS)

    Yahaya, Ommi Kalsom Mardziah; Jafri, Mohd. Zubir Mat; Aziz, Azlan Abdul; Omar, Ahmad Fairuz

    2015-06-01

    This study presents an alternative approach for the nondestructive assessment of fruit quality parameters with the use of a simplified optical fiber red-green-blue system (OF-RGB). The optical sensor system presented in this work is designed to rapidly measure the firmness, acidity, and soluble solid content of an intact Sala mango on the basis of color properties. The system consists of three light-emitting diodes with peak emission at 635 (red), 525 (green), and 470 nm (blue), as well as a single photodetector capable of sensing visible light. The measurements were conducted using the reflectance technique. The analyses were conducted by comparing the results obtained through the proposed system with those measured using two commercial spectrometers, namely, QE65000 and FieldSpec 3. The developed RGB system showed satisfactory accuracy in the measurement of acidity (R2=0.795) and firmness (R2=0.761), but a relatively lower accuracy in the measurement of soluble solid content (R2=0.593) of intact mangoes. The results obtained through OF-RGB are comparable with those measured by QE65000 and FieldSpec 3. This system is a promising new technology with rapid response, easy operation, and low cost with potential applications in the nondestructive assessment of quality attributes.

  12. Intrinsic fiber optical gas sensor based on surface plasmon resonance spectroscopy

    NASA Astrophysics Data System (ADS)

    Niggemann, Matthias; Katerkamp, Andreas; Pellmann, Maria; Bolsmann, Peter; Reinbold, Joerg; Cammann, Karl

    1995-09-01

    A miniaturized fiber optical sensor based on surface plasmon resonance spectroscopy is investigated in view of the detection of organic solvent vapors, particularly tetrachloroethene. Surface plasmons are excited on a silver coated multimode fiber by polychromatic light, and the resonant excitation is detected as a resonant absorption band in the measured output spectrum. When the analyte is absorbed in a thin gas-sensitive polysiloxane film deposited on the silver layer the polymer film changes its thickness and its refractive index. These changes result in a wavelength shift of the resonant curve depending on the analyte gas concentration. Theoretical considerations about the sensing effect are made and resonance curves were computer-simulated. Based on this simulation the layout of all sensor parameters was optimized. The sensor shows an excellent response to tetrachloroethene with a response time of two seconds and high reporducibility. Using self-assembling monolayers on the silver surface a long-term stability of more than three months is obtained. The sensor shows low cross sensitivities less than 1% to other solvent vapors like aceton and ethanol, furthermore, the influence of humidity is very low. This miniaturized fiber optical sensor in combination with an easy-to-handle and non-sophisticated measuring and evaluation unit is excellently suitable for the remote sensing of special organic solvent vapors.

  13. Optical induction of muscle contraction at the tissue scale through intrinsic cellular amplifiers.

    PubMed

    Yoon, Jonghee; Choi, Myunghwan; Ku, Taeyun; Choi, Won Jong; Choi, Chulhee

    2014-08-01

    The smooth muscle cell is the principal component responsible for involuntary control of visceral organs, including vascular tonicity, secretion, and sphincter regulation. It is known that the neurotransmitters released from nerve endings increase the intracellular Ca(2+) level in smooth muscle cells followed by muscle contraction. We herein report that femtosecond laser pulses focused on the diffraction-limited volume can induce intracellular Ca(2+) increases in the irradiated smooth muscle cell without neurotransmitters, and locally increased intracellular Ca(2+) levels are amplified by calcium-induced calcium-releasing mechanisms through the ryanodine receptor, a Ca(2+) channel of the endoplasmic reticulum. The laser-induced Ca(2+) increases propagate to adjacent cells through gap junctions. Thus, ultrashort-pulsed lasers can induce smooth muscle contraction by controlling Ca(2+), even with optical stimulation of the diffraction-limited volume. This optical method, which leads to reversible and reproducible muscle contraction, can be used in research into muscle dynamics, neuromuscular disease treatment, and nanorobot control. Copyright © 2014 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

  14. Correlating optical damage threshold with intrinsic defect populations in fused silica as a function of heat treatment temperature

    SciTech Connect

    Shen, N.; Matthews, M. J.; Elhadj, S.; Miller, P. E.; Nelson, A. J.; Hamilton, J.

    2013-04-03

    Here, chemical vapor deposition (CVD) is used for the production of fused silica optics in high-power laser applications. However, relatively little is known about the ultraviolet laser damage threshold of CVD films and how they relate to intrinsic defects produced during deposition. We present here a study relating structural and electronic defects in CVD films to 355 nm pulsed-laser damage threshold as a function of post-deposition annealing temperature (THT). Plasma-enhanced CVD based on SiH4/N2O under oxygen-rich conditions was used to deposit 1.5, 3.1 and 6.4 µm thick films on etched SiO2 substrates. Rapid annealing was performed using a scanned CO2 laser beam up to THT ~ 2100 K. The films were then characterized using x-ray photoemission spectroscopy, Fourier transform infrared spectroscopy (FTIR) and photoluminescence spectroscopy. A gradual transition in the damage threshold of annealed films was observed for THT values up to 1600 K, correlating with a decrease in non-bridging silanol and oxygen deficient centres. An additional sharp transition in damage threshold also occurs at ~1850 K indicating substrate annealing. Based on our results, a mechanism for damage-related defect annealing is proposed, and the potential of using high-THT CVD SiO2 to mitigate optical damage is also discussed.

  15. Oxaliplatin-chitosan nanoparticles induced intrinsic apoptotic signaling pathway: a "smart" drug delivery system to breast cancer cell therapy.

    PubMed

    Vivek, Raju; Thangam, Ramar; Nipunbabu, Varukattu; Ponraj, Thondhi; Kannan, Soundarapandian

    2014-04-01

    This study was to investigate "smart" pH-responsive drug delivery system (DDS) based on chitosan nano-carrier for its potential intelligent controlled release and enhancing chemotherapeutic efficiency of Oxalipaltin. Oxaliplatin was loaded onto chitosan by forming complexes with degradable to construct nano-carrier as a DDS. Oxaliplatin was released from the DDS much more rapidly at pH 4.5 than at pH 7.4, which is a desirable characteristic for tumor-targeted drug delivery. Furthermore, the possible intrinsic apoptotic signaling pathway was explored by Western blot. It was found that expression of Bax, Bik, cytochrome C, caspase-9 and -3 was significantly up-regulated while the Bcl-2 and Survivin were inhibited in breast cancer MCF-7 cells. For instance, nanoparticles inducing apoptosis in caspase-dependent manner indicate that chitosan nanoparticles could act as an efficient DDS importing Oxalipaltin to target cancer cells. These approaches suggest that "smart" Oxaliplatin delivery strategy is a promising approach to cancer therapy. Copyright © 2014 Elsevier B.V. All rights reserved.

  16. Effects of Linker Length and Transient Secondary Structure Elements in the Intrinsically Disordered Notch RAM Region on Notch Signaling.

    PubMed

    Sherry, Kathryn P; Johnson, Scott E; Hatem, Christine L; Majumdar, Ananya; Barrick, Doug

    2015-11-06

    Formation of the bivalent interaction between the Notch intracellular domain (NICD) and the transcription factor CBF-1/RBP-j, Su(H), Lag-1 (CSL) is a key event in Notch signaling because it switches Notch-responsive genes from a repressed state to an activated state. Interaction of the intrinsically disordered RBP-j-associated molecule (RAM) region of NICD with CSL is thought to both disrupt binding of corepressor proteins to CSL and anchor NICD to CSL, promoting interaction of the ankyrin domain of NICD with CSL through an effective concentration mechanism. To quantify the role of disorder in the RAM linker region on the effective concentration enhancement of Notch transcriptional activation, we measured the effects of linker length variation on activation. The resulting activation profile has general features of a worm-like chain model for effective concentration. However, deviations from the model for short sequence deletions suggest that RAM contains sequence-specific structural elements that may be important for activation. Structural characterization of the RAM linker with sedimentation velocity analytical ultracentrifugation and NMR spectroscopy reveals that the linker is compact and contains three transient helices and two extended and dynamic regions. To test if these secondary structure elements are important for activation, we made sequence substitutions to change the secondary structure propensities of these elements and measured transcriptional activation of the resulting variants. Substitutions to two of these nonrandom elements (helix 2, extended region 1) have effects on activation, but these effects do not depend on the nature of the substituting residues. Thus, the primary sequences of these elements, but not their secondary structures, are influencing signaling. Copyright © 2015. Published by Elsevier Ltd.

  17. An Optical Tomography System Using a Digital Signal Processor.

    PubMed

    Rahim, Ruzairi Abdul; Thiam, Chiam Kok; Rahiman, Mohd Hafiz Fazalul

    2008-03-27

    The use of a personal computer together with a Data Acquisition System (DAQ) as the processing tool in optical tomography systems has been the norm ever since the beginning of process tomography. However, advancements in silicon fabrication technology allow nowadays the fabrication of powerful Digital Signal Processors (DSP) at a reasonable cost. This allows this technology to be used in an optical tomography system since data acquisition and processing can be performed within the DSP. Thus, the dependency on a personal computer and a DAQ to sample and process the external signals can be reduced or even eliminated. The DSP system was customized to control the data acquisition process of 16x16 optical sensor array, arranged in parallel beam projection. The data collected was used to reconstruct the cross sectional image of the pipeline conveyor. For image display purposes, the reconstructed image was sent to a personal computer via serial communication. This allows the use of a laptop to display the tomogram image besides performing any other offline analysis.

  18. Quasiparticle Representation of Coherent Nonlinear Optical Signals of Multiexcitons

    NASA Astrophysics Data System (ADS)

    Fingerhut, Benjamin; Bennet, Kochise; Roslyak, Oleksiy; Mukamel, Shaul

    2013-03-01

    Elementary excitations of many-Fermion systems can be described within the quasiparticle approach which is widely used in the calculation of transport and optical properties of metals, semiconductors, molecular aggregates and strongly correlated quantum materials. The excitations are then viewed as independent harmonic oscillators where the many-body interactions between the oscillators are mapped into anharmonicities. We present a Green's function approach based on coboson algebra for calculating nonlinear optical signals and apply it onwards the study of two and three exciton states. The method only requires the diagonalization of the single exciton manifold and avoids equations of motion of multi-exciton manifolds. Using coboson algebra many body effects are recast in terms of tetradic exciton-exciton interactions: Coulomb scattering and Pauli exchange. The physical space of Fermions is recovered by singular-value decomposition of the over-complete coboson basis set. The approach is used to calculate third and fifth order quantum coherence optical signals that directly probe correlations in two- and three exciton states and their projections on the two and single exciton manifold.

  19. An Optical Tomography System Using a Digital Signal Processor

    PubMed Central

    Rahim, Ruzairi Abdul; Thiam, Chiam Kok; Fazalul Rahiman, Mohd Hafiz

    2008-01-01

    The use of a personal computer together with a Data Acquisition System (DAQ) as the processing tool in optical tomography systems has been the norm ever since the beginning of process tomography. However, advancements in silicon fabrication technology allow nowadays the fabrication of powerful Digital Signal Processors (DSP) at a reasonable cost. This allows this technology to be used in an optical tomography system since data acquisition and processing can be performed within the DSP. Thus, the dependency on a personal computer and a DAQ to sample and process the external signals can be reduced or even eliminated. The DSP system was customized to control the data acquisition process of 16×16 optical sensor array, arranged in parallel beam projection. The data collected was used to reconstruct the cross sectional image of the pipeline conveyor. For image display purposes, the reconstructed image was sent to a personal computer via serial communication. This allows the use of a laptop to display the tomogram image besides performing any other offline analysis. PMID:27879811

  20. Coherent Terahertz Wireless Signal Transmission Using Advanced Optical Fiber Communication Technology

    NASA Astrophysics Data System (ADS)

    Kanno, Atsushi; Kuri, Toshiaki; Morohashi, Isao; Hosako, Iwao; Kawanishi, Tetsuya; Yoshida, Yuki; Kitayama, Ken-ichi

    2015-02-01

    Coherent terahertz signal transmission with multilevel modulation and demodulation is demonstrated using an optical sub-harmonic IQ mixer (SHIQM), which consists of optical components in advanced optical fiber communication technologies. An optical-frequency-comb-employed signal generator is capable of vector modulation as well as frequency tunability. Digital signal processing (DSP) adopted from the recently developed optical digital coherent communication can easily demodulate multi-level modulated terahertz signals by using electrical heterodyning for intermediate-frequency (IF) down conversion. This technique is applicable for mobile backhauling in the next-generation mobile communication technology directly connected to an optical fiber network as a high-speed wireless transmission link.

  1. A dual-detector optical receiver for PDM signals detection

    PubMed Central

    Chen, Guanyu; Yu, Yu; Zhang, Xinliang

    2016-01-01

    We propose and fabricate a silicon based dual-detector optical receiver, which consists of a two dimensional (2D) grating coupler (GC) and two separate germanium photodetectors (Ge PDs). The 2D GC performs polarization diversity, and thus demultiplexing and detection for polarization division multiplexed (PDM) signals can be achieved. Through a specific design with double-sides illumination, the space charge density can be reduced and the responsivity and saturation power can be improved significantly. The measured dark current, responsivity and bandwidth are 0.86 μA, 1.06 A/W and 36 GHz under 3 V reverse biased voltage, respectively. Both DC currents and eye diagrams are measured for the proposed device and the results validate its performance successfully. The power penalty between the single and dual polarized signals is about 1.9 dB under 10 and 20 Gb/s cases for both the two Ge PDs. The proposed direct detection (DD) for PDM signals with high speed, high responsivity and large saturation power is cost-effective and promising for short reach optical communication. PMID:27198501

  2. Nonlinear optical signals and spectroscopy with quantum light

    NASA Astrophysics Data System (ADS)

    Dorfman, Konstantin E.; Schlawin, Frank; Mukamel, Shaul

    2016-10-01

    Conventional nonlinear spectroscopy uses classical light to detect matter properties through the variation of its response with frequencies or time delays. Quantum light opens up new avenues for spectroscopy by utilizing parameters of the quantum state of light as novel control knobs and through the variation of photon statistics by coupling to matter. An intuitive diagrammatic approach is presented for calculating ultrafast spectroscopy signals induced by quantum light, focusing on applications involving entangled photons with nonclassical bandwidth properties—known as "time-energy entanglement." Nonlinear optical signals induced by quantized light fields are expressed using time-ordered multipoint correlation functions of superoperators in the joint field plus matter phase space. These are distinct from Glauber's photon counting formalism which uses normally ordered products of ordinary operators in the field space. One notable advantage for spectroscopy applications is that entangled-photon pairs are not subjected to the classical Fourier limitations on the joint temporal and spectral resolution. After a brief survey of properties of entangled-photon pairs relevant to their spectroscopic applications, different optical signals, and photon counting setups are discussed and illustrated for simple multilevel model systems.

  3. Magneto-optic readout signals and Malus law

    NASA Astrophysics Data System (ADS)

    Attaran-Kakhki, Ebrahim

    2006-09-01

    In recent years Magneto-optical techniques have been used extensively in memory systems, which allow high density recording and high speed access time. Usually In this method the light beam from a He-Ne laser is linearly polarized by a polarizer and passes or reflected from a magneto-optic recording medium thin layer. The polarized light will modulate and the plane of polarization is rotated. The rotated polarized light passes through an analyzer and focus on a photo-detector. The output of the photo-detector is measure as a photocurrent signal according to Malus law. In all measurement the Cosin Malus law is the base and accepted. But in our present work we found that in practice it is necessary to modify the signal or modify the Malus law. In other word some constant should be added to the Malus law. In this measurement we averaged about 5000 reading for signals in each point and then we have plotted out the Malus law. The measured values are compared between the theoretical and practical measurement.

  4. A dual-detector optical receiver for PDM signals detection

    NASA Astrophysics Data System (ADS)

    Chen, Guanyu; Yu, Yu; Zhang, Xinliang

    2016-05-01

    We propose and fabricate a silicon based dual-detector optical receiver, which consists of a two dimensional (2D) grating coupler (GC) and two separate germanium photodetectors (Ge PDs). The 2D GC performs polarization diversity, and thus demultiplexing and detection for polarization division multiplexed (PDM) signals can be achieved. Through a specific design with double-sides illumination, the space charge density can be reduced and the responsivity and saturation power can be improved significantly. The measured dark current, responsivity and bandwidth are 0.86 μA, 1.06 A/W and 36 GHz under 3 V reverse biased voltage, respectively. Both DC currents and eye diagrams are measured for the proposed device and the results validate its performance successfully. The power penalty between the single and dual polarized signals is about 1.9 dB under 10 and 20 Gb/s cases for both the two Ge PDs. The proposed direct detection (DD) for PDM signals with high speed, high responsivity and large saturation power is cost-effective and promising for short reach optical communication.

  5. Detection, Evaluation, and Optimization of Optical Signals Generated by Fiber Optic Bragg Gratings Under Dynamic Excitations

    NASA Technical Reports Server (NTRS)

    Adamovsky, Grigory; Lekki, John; Lock, James A.

    2002-01-01

    The dynamic response of a fiber optic Bragg grating to mechanical vibrations is examined both theoretically and experimentally. The theoretical expressions describing the consequences of changes in the grating's reflection spectrum are derived for partially coherent beams in an interferometer. The analysis is given in terms of the dominant wavelength, optical bandwidth, and optical path difference of the interfering signals. Changes in the reflection spectrum caused by a periodic stretching and compression of the grating were experimentally measured using an unbalanced Michelson interferometer, a Michelson interferometer with a non-zero optical path difference. The interferometer's sensitivity to changes in dominant wavelength of the interfering beams was measured as a function of interferometer unbalance and was compared to theoretical predictions. The theoretical analysis enables the user to determine the optimum performance for an unbalanced interferometer.

  6. Brillouin optical spectrum analyzer monitoring of subcarrier-multiplexed fiber-optic signals.

    PubMed

    Stern, Yonatan; Zhong, Kun; Schneider, Thomas; Ben-Ezra, Yossef; Zhang, Ru; Tur, Moshe; Zadok, Avi

    2013-09-01

    Optical spectral analysis of closely spaced, subcarrier multiplexed fiber-optic transmission is performed, based on stimulated Brillouin scattering (SBS). The Brillouin gain window of a single, continuous-wave pump is scanned across the spectral extent of the signal under test. The polarization pulling effect associated with SBS is employed to improve the rejection ratio of the analysis by an order of magnitude. Ten tones, spaced by only 10 MHz and each carrying random-sequence on-off keying data, are clearly resolved. The measurement identifies the absence of a single subcarrier, directly in the optical domain. The results are applicable to the monitoring of optical orthogonal frequency domain multiplexing and radio over fiber transmission.

  7. Electronic structure and optical properties of the intrinsically chiral 16-electron superatom complex [Au20(PP3)4](4+).

    PubMed

    Knoppe, Stefan; Lehtovaara, Lauri; Häkkinen, Hannu

    2014-06-12

    The recently solved crystal structure of the [Au20(PP3)4]Cl4 cluster (PP3: tris(2-(diphenylphophino)ethyl)phosphine) is examined using density functional theory (DFT). The Au20 core of the cluster is intrinsically chiral by the arrangement of the Au atoms. This is in contrast to the chirality of thiolate-protected gold clusters, in which the protecting Au-thiolate units are arranged in chiral patterns on achiral cores. We interpret the electronic structure of the [Au20(PP3)4]Cl4 cluster in terms of the superatom complex model. The 16-electron cluster cannot be interpreted as a dimer of 8-electron clusters (which are magic). Instead, a superatomic electron configuration of 1S(2) 1P(6) 1D(6) 2S(2) is found. The 2S band is strongly stabilized, and the 1D states are nondegenerate with a large gap. Ligand protection of the (Au20)(4+) core leads to a significant increase of the HL-gap and thus stabilization. We also tested a charge of +II, which would give rise to an 18-electron superatom complex. Our results indicate that the 16-electron cluster is indeed more stable. We also investigate the optical properties of the cluster. The experimental absorption spectrum is well-reproduced by time-dependent DFT. Prominent transitions are analyzed by time-dependent density-functional perturbation theory. The intrinsic chirality of the cluster is compared to that of Au38(SR)24. We observe that the chiral arrangement of the protecting Au-SR units in Au38(SR)24 has very strong influence on the strength of the CD spectra, whereas phosphine protection in the title compound does not.

  8. Optical microphone with fiber Bragg grating and signal processing techniques

    NASA Astrophysics Data System (ADS)

    Tosi, Daniele; Olivero, Massimo; Perrone, Guido

    2008-06-01

    In this paper, we discuss the realization of an optical microphone array using fiber Bragg gratings as sensing elements. The wavelength shift induced by acoustic waves perturbing the sensing Bragg grating is transduced into an intensity modulation. The interrogation unit is based on a fixed-wavelength laser source and - as receiver - a photodetector with proper amplification; the system has been implemented using devices for standard optical communications, achieving a low-cost interrogator. One of the advantages of the proposed approach is that no voltage-to-strain calibration is required for tracking dynamic shifts. The optical sensor is complemented by signal processing tools, including a data-dependent frequency estimator and adaptive filters, in order to improve the frequency-domain analysis and mitigate the effects of disturbances. Feasibility and performances of the optical system have been tested measuring the output of a loudspeaker. With this configuration, the sensor is capable of correctly detecting sounds up to 3 kHz, with a frequency response that exhibits a top sensitivity within the range 200-500 Hz; single-frequency input sounds inducing an axial strain higher than ~10nɛ are correctly detected. The repeatability range is ~0.1%. The sensor has also been applied for the detection of pulsed stimuli generated from a metronome.

  9. The Intersection of the Extrinsic Hedgehog and WNT/Wingless Signals with the Intrinsic Hox Code Underpins Branching Pattern and Tube Shape Diversity in the Drosophila Airways

    PubMed Central

    Matsuda, Ryo; Hosono, Chie; Saigo, Kaoru; Samakovlis, Christos

    2015-01-01

    The tubular networks of the Drosophila respiratory system and our vasculature show distinct branching patterns and tube shapes in different body regions. These local variations are crucial for organ function and organismal fitness. Organotypic patterns and tube geometries in branched networks are typically controlled by variations of extrinsic signaling but the impact of intrinsic factors on branch patterns and shapes is not well explored. Here, we show that the intersection of extrinsic hedgehog(hh) and WNT/wingless (wg) signaling with the tube-intrinsic Hox code of distinct segments specifies the tube pattern and shape of the Drosophila airways. In the cephalic part of the airways, hh signaling induces expression of the transcription factor (TF) knirps (kni) in the anterior dorsal trunk (DTa1). kni represses the expression of another TF spalt major (salm), making DTa1 a narrow and long tube. In DTa branches of more posterior metameres, Bithorax Complex (BX-C) Hox genes autonomously divert hh signaling from inducing kni, thereby allowing DTa branches to develop as salm-dependent thick and short tubes. Moreover, the differential expression of BX-C genes is partly responsible for the anterior-to-posterior gradual increase of the DT tube diameter through regulating the expression level of Salm, a transcriptional target of WNT/wg signaling. Thus, our results highlight how tube intrinsic differential competence can diversify tube morphology without changing availabilities of extrinsic factors. PMID:25615601

  10. Polarization sensitive optical coherence tomography of melanin provides intrinsic contrast based on depolarization

    PubMed Central

    Baumann, Bernhard; Baumann, Stefan O.; Konegger, Thomas; Pircher, Michael; Götzinger, Erich; Schlanitz, Ferdinand; Schütze, Christopher; Sattmann, Harald; Litschauer, Marco; Schmidt-Erfurth, Ursula; Hitzenberger, Christoph K.

    2012-01-01

    Polarization sensitive optical coherence tomography (PS-OCT) is a functional extension of OCT. In addition to imaging based on tissue reflectivity, PS-OCT also enables depth-resolved mapping of sample polarization properties such as phase-retardation, birefringent axis orientation, Stokes vectors, and degree of polarization uniformity (DOPU). In this study, PS-OCT was used to investigate the polarization properties of melanin. In-vitro measurements in samples with varying melanin concentrations revealed polarization scrambling, i.e. depolarization of backscattered light. Polarization scrambling in the PS-OCT images was more pronounced for higher melanin concentrations and correlated with the concentration of the melanin granules in the phantoms. Moreover, in-vivo PS-OCT was performed in the retinas of normal subjects and individuals with albinism. Unlike in the normal eye, polarization scrambling in the retinal pigment epithelium (RPE) was less pronounced or even not observable in PS-OCT images of albinos. These results indicate that the depolarizing appearance of pigmented structures like, for instance, the RPE is likely to be caused by the melanin granules contained in these cells. PMID:22808437

  11. Coinage Metal Superatomic Cores: Insights into Their Intrinsic Stability and Optical Properties from Relativistic DFT Calculations.

    PubMed

    Gam, Franck; Paez-Hernandez, Dayan; Arratia-Perez, Ramiro; Liu, C W; Kahlal, Samia; Saillard, Jean-Yves; Muñoz-Castro, Alvaro

    2017-08-22

    Coinage-metal atomically precise nanoclusters are made of a well-defined metallic core embedded in a ligand-protecting outer shell. Whereas gold derivatives are particularly well documented, examples of silver nanoclusters are somewhat limited and copper species remain particularly scare. Our DFT relativistic calculations on superatomic metallic cores indicate that copper species are almost as stable as gold clusters and more stable than their silver counterparts. Thus, for silver superatomic cores, the role of the stabilizing ligands is more crucial in the stabilization of the overall structure, in comparison to copper and gold. Hence, the chemistry of the earlier counterparts of gold, especially copper, should grow quickly with at least characterizations of species related to that found in the heavier elements in the triad, which requires tackling synthetic challenges. Time-dependent (TD)-DFT calculations show that with an increase of the cluster core nuclearity, the absorption bands are redshifted, allowing us to differentiate between the clusters types. Moreover, the optical properties of the silver cores are fairly different from that of their Cu and Au relatives. © 2017 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim.

  12. A Random Walk into Optical Signal Processing and Integrated Optofluidics

    NASA Astrophysics Data System (ADS)

    Baylor, Martha-Elizabeth

    2013-04-01

    As a young child, I knew that I wanted to be a paleontologist. My parents, both artists, did their best to encourage me in my quest to dig for dinosaurs. However, decisions during my late high school and early college years serendipitously shifted my path so that I ended up pursuing a career in applied physics. In particular, my career path has been centered in optics with an emphasis on holography and signal processing. This talk will discuss my research in the areas of opto-electronic blind source separation and holographic photopolymers as well as the non-linear path that has gotten me to this point.

  13. Optical amplification and optical filter based signal processing for cost and energy efficient spatial multiplexing.

    PubMed

    Krummrich, Peter M

    2011-08-15

    Spatial division multiplexing has been proposed as an option for further capacity increase of transmission fibers. Application of this concept is attractive only, if cost and energy efficient implementations can be found. In this work, optical amplification and optical filter based signal processing concepts are investigated. Deployment of multi mode fibers as the waveguide type for erbium doped fiber amplifiers potentially offers cost and energy efficiency advantages compared to using multi core fibers in preamplifier as well as booster stages. Additional advantages can be gained from optimization of the amplifier module design. Together with transponder design optimizations, they can increase the attractiveness of inverse spatial multiplexing, which is proposed as an intermediate step. Signal processing based on adaptive passive optical filters offers an alternative approach for the separation of channels at the receiver which have experienced mode coupling along the link. With this optical filter based approach, fiber capacity can potentially be increased faster and more energy efficiently than with solutions relying solely on electronic signal processing.

  14. A Statistical Analysis of the Output Signals of an Acousto-Optic Spectrum Analyzer for CW (Continuous-Wave) Signals

    DTIC Science & Technology

    1988-10-01

    A statistical analysis on the output signals of an acousto - optic spectrum analyzer (AOSA) is performed for the case when the input signal is a...processing, Electronic warfare, Radar countermeasures, Acousto - optic , Spectrum analyzer, Statistical analysis, Detection, Estimation, Canada, Modelling.

  15. Symbol rate identification for auxiliary amplitude modulation optical signal

    NASA Astrophysics Data System (ADS)

    Wei, Junyu; Dong, Zhi; Huang, Zhiping; Zhang, Yimeng

    2016-09-01

    In this paper, we creatively propose and demonstrate a method for symbol rate identification (SRI) of auxiliary amplitude modulation (AAM) optical signal based on asynchronous delay-tap sampling (ADTS) and average magnitude difference function (AMDF). The method can accurately estimate symbol rate and has large transmission impairments tolerance. Furthermore, it can be realized in the digital signal processor (DSP) with low logical resources because of multiplication-free. In order to improve the accuracy of SRI, the peak to valley ratio (PTVR) of AMDF is introduced into our method for blind chromatic dispersion (CD) compensation. The results of the numerical simulations show that the overall maximum SRI error is smaller 0.079% for return-to-zero (RZ) on-off keying (OOK), RZ differential phase-shift keying (DPSK), RZ differential quadrature phase-shift keying (DQPSK) and RZ 16-ary quadrature amplitude modulation (QAM) with 50% duty cycles.

  16. Optical modulation techniques for analog signal processing and CMOS compatible electro-optic modulation

    NASA Astrophysics Data System (ADS)

    Gill, Douglas M.; Rasras, Mahmoud; Tu, Kun-Yii; Chen, Young-Kai; White, Alice E.; Patel, Sanjay S.; Carothers, Daniel; Pomerene, Andrew; Kamocsai, Robert; Beattie, James; Kopa, Anthony; Apsel, Alyssa; Beals, Mark; Mitchel, Jurgen; Liu, Jifeng; Kimerling, Lionel C.

    2008-02-01

    Integrating electronic and photonic functions onto a single silicon-based chip using techniques compatible with mass-production CMOS electronics will enable new design paradigms for existing system architectures and open new opportunities for electro-optic applications with the potential to dramatically change the management, cost, footprint, weight, and power consumption of today's communication systems. While broadband analog system applications represent a smaller volume market than that for digital data transmission, there are significant deployments of analog electro-optic systems for commercial and military applications. Broadband linear modulation is a critical building block in optical analog signal processing and also could have significant applications in digital communication systems. Recently, broadband electro-optic modulators on a silicon platform have been demonstrated based on the plasma dispersion effect. The use of the plasma dispersion effect within a CMOS compatible waveguide creates new challenges and opportunities for analog signal processing since the index and propagation loss change within the waveguide during modulation. We will review the current status of silicon-based electrooptic modulators and also linearization techniques for optical modulation.

  17. Demonstration of the frequency modulation of optical signals with a high frequency deviation parameter

    SciTech Connect

    Shamray, A V; Kozlov, A S; Il'ichev, I V; Petrov, M P

    2008-03-31

    A new type of an integrated optical modulator for the frequency coding of optical signals is developed and fabricated. The modulator operation is based on the original technology of the electric control of a Bragg grating. The frequency modulation of an optical signal with the frequency deviation of 25 GHz is demonstrated experimentally. The modular was used to transfer the ASCII code through an optical fibre. (optical communication)

  18. Is the zona pellucida an intrinsic source of signals activating maternal recognition of the developing mammalian embryo?

    PubMed

    Fujiwara, Hiroshi; Araki, Yoshihiko; Toshimori, Kiyotaka

    2009-07-01

    Mammalian mothers undergoing embryo implantation must specifically recognize the developing embryo in a species-restricted manner. We previously observed that immune cells derived from early pregnant mice could promote endometrial differentiation and embryo implantation in blastocyst-transferred pseudopregnant mice. Although the precise mechanism remains unknown, it is suggested that the maternal immune system undergoes functional changes after recognizing developing embryos from the very early stages of pregnancy. Since it is physically impossible for immune cells to directly interact with the developing embryo while it is surrounded by the zona pellucida (ZP), it is speculated that the embryo produces certain embryo- and species-specific soluble factor(s) in the oviduct before hatching. As a candidate for this factor, we have paid attention to the ZP that is normally protected from immunological attack during oogenesis in the ovarian follicle. ZP-specific glycoproteins are known to play important roles in the species- and oocyte-specific binding of sperm, and the ZP can also be considered an abundant store of oocyte- and species-specific glycoproteins. In contrast to unfertilized oocytes, developing embryos may degrade the ZP starting just after fertilization and proceeding until hatching using enzymes that are released from cortical granules or produced by the developing embryo. Accordingly, the developing embryo might provide ZP-degradation products including oligosaccharide chains to the immune system from the very early stages. Taken together, we propose here a novel hypothesis that these ZP-derivatives can act as an intrinsic signal from the developing embryo for maternal recognition by the immune system.

  19. Membrane binding mode of intrinsically disordered cytoplasmic domains of T cell receptor signaling subunits depends on lipid composition

    SciTech Connect

    Sigalov, Alexander B.; Hendricks, Gregory M.

    2009-11-13

    Intrinsically disordered cytoplasmic domains of T cell receptor (TCR) signaling subunits including {zeta}{sub cyt} and CD3{epsilon}{sub cyt} all contain one or more copies of an immunoreceptor tyrosine-based activation motif (ITAM), tyrosine residues of which are phosphorylated upon receptor triggering. Membrane binding-induced helical folding of {zeta}{sub cyt} and CD3{epsilon}{sub cyt} ITAMs is thought to control TCR activation. However, the question whether or not lipid binding of {zeta}{sub cyt} and CD3{epsilon}{sub cyt} is necessarily accompanied by a folding transition of ITAMs remains open. In this study, we investigate whether the membrane binding mechanisms of {zeta}{sub cyt} and CD3{epsilon}{sub cyt} depend on the membrane model used. Circular dichroic and fluorescence data indicate that binding of {zeta}{sub cyt} and CD3{epsilon}{sub cyt} to detergent micelles and unstable vesicles is accompanied by a disorder-to-order transition, whereas upon binding to stable vesicles these proteins remain unfolded. Using electron microscopy and dynamic light scattering, we show that upon protein binding, unstable vesicles fuse and rupture. In contrast, stable vesicles remain intact under these conditions. This suggests different membrane binding modes for {zeta}{sub cyt} and CD3{epsilon}{sub cyt} depending on the bilayer stability: (1) coupled binding and folding, and (2) binding without folding. These findings explain the long-standing puzzle in the literature and highlight the importance of the choice of an appropriate membrane model for protein-lipid interactions studies.

  20. Discussion on the Modelling and Processing of Signals fom an Acousto-Optic Spectrum Analyzer.

    DTIC Science & Technology

    1987-06-01

    AD-AIBS 639 DISCUSSION ON THE MODELLING AND PROCESSIN OF SIGNALS 1/1 FOR RN ACOUSTO - OPTIC SPECTRUM ANALYZER(U)G DFENCE RESERCH ESTABGLISHMENT OTTANA...8217’~ AV - I National DefenseI Defence nationale DISCUSSION ON THE MODELLING AND PROCESSING OF SIGNALS FROM AN ACOUSTO - OPTIC SPECTRUM ANALYZER by Guy...signals generated by an Acousto - Optic Spectrum Analyzer (AOSA). It also shows how this calculation can be related to pulse modu- lated signals. In its

  1. Simple signal-to-signal beat interference cancellation receiver based on balanced detection for a single-sideband optical OFDM signal with a reduced guard band.

    PubMed

    Ma, Jianxin

    2013-11-01

    A simple signal-to-signal beat interference cancellation receiver based on balanced detection (ICRBD) with an interleaver, a 2×2 three-decibel optical coupler, and a balanced photodiode pair is proposed for a single-sideband optical orthogonal frequency division multiplexing (SSB-OOFDM) signal with a reduced guard band (GB). Simulation demonstration of the ICRBD for a 40 Gbit/s 16-QAM SSB-OOFDM signal with a reduced GB was achieved successfully.

  2. Phase resolved digital signal processing in optical coherence tomography

    NASA Astrophysics Data System (ADS)

    de Boer, Johannes F.; Tripathi, Renu; Park, Boris H.; Nassif, Nader

    2002-06-01

    We present phase resolved digital signal processing techniques for Optical Coherence Tomography to correct for the non Gaussian shape of source spectra and for Group Delay Dispersion (GDD). A broadband source centered at 820 nm was synthesized by combining the spectra of two superluminescent diodes to improve axial image resolution in an optical coherence tomography (OCT) system. Spectral shaping was used to reduce the side lobes (ringing) in the axial point spread function due to the non-Gaussian shape of the spectra. Images of onion cells taken with each individual source and the combined sources, respectively, show the improved resolution and quality enhancement in a turbid biological sample. An OCT system operating at 1310 nm was used to demonstrate that the broadening effect of group delay dispersion (GDD) on the coherence function could be eliminated completely by introducing a quadratic phase shift in the Fourier domain of the interferometric signal. The technique is demonstrated by images of human skin grafts with group delay dispersion mismatch between sample and reference arm before and after digital processing.

  3. Intrinsic Optical Activity and Conformational Flexibility: New Insights on the Role of Ring Morphology from Cyclic Amines

    NASA Astrophysics Data System (ADS)

    Craft, Clayton L.; Lemler, Paul M.; Vaccaro, Patrick

    2017-06-01

    Electronic circular birefringence (ECB), which causes rotation of the linear-polarization state for non-resonant light traversing an isotropic sample of chiral molecules, long has served as a robust means for assessing enantiomeric purity, but quantitative studies of this important property historically have been restricted to condensed phases where environmental effects (e.g., solvent-solute interactions or crystal-packing forces) can alter the magnitude and even the sign of the intrinsic behavior. As part of a continuing effort to elucidate the structural and electronic origins of such chiroptical phenomena, the dependence of optical rotatory dispersion (or wavelength-resolved ECB) on ring morphology has been explored for two saturated monocyclic amines, (R)-2-methylpyrrolidine and (S)-2-methylpiperidine. To assess the putative role of extrinsic perturbations, ambient measurements of specific optical rotation were performed under both solvated and isolated conditions, where the latter gas-phase work involved use of ultrasensitive cavity ring-down polarimetry. Each of the targeted compounds support active conformational degrees of freedom in the form of large-amplitude puckering motion of the heterocyclic ring combined with internal rotation of methyl substituents, with the antagonistic chiroptical properties exhibited by the resulting conformers combining to yield the overall response observed from a thermally equilibrated ensemble of molecules. Experimental ECB findings will be contrasted with those reported previously for ketones built upon comparable carbocyclic frameworks, and interpreted, in part, by reference to electronic-structure and linear-response calculations performed at various levels of quantum-chemical theory.

  4. Time-domain model of quantum-dot semiconductor optical amplifiers for wideband optical signals.

    PubMed

    Puris, D; Schmidt-Langhorst, C; Lüdge, K; Majer, N; Schöll, E; Petermann, K

    2012-11-19

    We present a novel theoretical time-domain model for a quantum dot semiconductor optical amplifier, that allows to simulate subpicosecond pulse propagation including power-based and phase-based effects. Static results including amplified spontaneous emission spectra, continuous wave amplification, and four-wave mixing experiments in addition to dynamic pump-probe simulations are presented for different injection currents. The model uses digital filters to describe the frequency dependent gain and microscopically calculated carrier-carrier scattering rates for the interband carrier dynamics. It can be used to calculate the propagation of multiple signals with different wavelengths or one wideband signal with high bitrate.

  5. On the Contribution of Curl-Free Current Patterns to the Ultimate Intrinsic Signal-to-Noise Ratio at Ultra-High Field Strength.

    PubMed

    Pfrommer, Andreas; Henning, Anke

    2017-02-10

    The ultimate intrinsic signal-to-noise ratio (SNR) is a coil independent performance measure to compare different receive coil designs. To evaluate this benchmark in a sample, a complete electromagnetic basis set is required. The basis set can be obtained by curl-free and divergence-free surface current distributions, which excite linearly independent solutions to Maxwell's equations. In this work, we quantitatively investigate the contribution of curl-free current patterns to the ultimate intrinsic SNR in a spherical head-sized model at 9.4 T. Therefore, we compare the ultimate intrinsic SNR obtained with having only curl-free or divergence-free current patterns, with the ultimate intrinsic SNR obtained from a combination of curl-free and divergence-free current patterns. The influence of parallel imaging is studied for various acceleration factors. Moreover results for different field strengths (1.5 T up to 11.7 T) are presented at specific voxel positions and acceleration factors. The full-wave electromagnetic problem is analytically solved using dyadic Green's functions. We show, that at ultra-high field strength (B0 ⩾7T) a combination of curl-free and divergence-free current patterns is required to achieve the best possible SNR at any position in a spherical head-sized model. On 1.5- and 3T platforms, divergence-free current patterns are sufficient to cover more than 90% of the ultimate intrinsic SNR.

  6. Use of Fiber Optic Interconnects for Signal Integrity

    NASA Astrophysics Data System (ADS)

    Phal, Yamuna D.; Phal, Deovrat D.

    2016-05-01

    Signal integrity (SI) is always a concern when it comes to high-speed data transmission. Even in space, there is a need for high-speed data transmission such as in the communication systems, monitoring various sub- systems and for other on-board experiments and applications.From Electromagneticperspective, using fiber-optic interconnect is highly recommended to avoid interference issues. This field has been explored for quite some time now, but mostly limited to applications that are on earth. Using these interconnects for harsh and extreme environments i.e. in space, requires reliability and ruggedness of interconnects and the system.This study suggests methods for optical fiber based communication systems for internal unit communication, communication within various instruments, as well as inter-board communication. A conclusion in terms of what areas need to be explored for enabling high-speed data transmission for space applications would be discussed in details. This study also explores and compares the existing technologies in the fiber-optic interconnects for space applications.

  7. Fast optical signals in the peripheral nervous system

    NASA Astrophysics Data System (ADS)

    Tong, Yunjie; Martin, Jeffrey M.; Sassaroli, Angelo; Clervil, Patricia R.; Bergethon, Peter R.; Fantini, Sergio

    2006-07-01

    We present a study of the near-infrared optical response to electrical stimulation of peripheral nerves. The sural nerve of six healthy subjects between the ages of 22 and 41 was stimulated with transcutaneous electrical pulses in a region located approximately 10 cm above the ankle. A two-wavelength (690 and 830 nm) tissue spectrometer was used to probe the same sural nerve below the ankle. We measured optical changes that peaked 60 to 160 ms after the electrical stimulus. On the basis of the strong wavelength dependence of these fast optical signals, we argue that their origin is mostly from absorption rather than scattering. From these absorption changes, we obtain oxy- and deoxy-hemoglobin concentration changes that describe a rapid hemodynamic response to electrical nerve activation. In five out of six subjects, this hemodynamic response is an increase in total (oxy+deoxy) hemoglobin concentration, consistent with a fast vasodilation. Our findings support the hypothesis that the peripheral nervous system undergoes neurovascular coupling, even though more data is needed to prove such hypothesis.

  8. Digital signal processing techniques for coherent optical communication

    NASA Astrophysics Data System (ADS)

    Goldfarb, Gilad

    Coherent detection with subsequent digital signal processing (DSP) is developed, analyzed theoretically and numerically and experimentally demonstrated in various fiber-optic transmission scenarios. The use of DSP in conjunction with coherent detection unleashes the benefits of coherent detection which rely on the preservaton of full information of the incoming field. These benefits include high receiver sensitivity, the ability to achieve high spectral-efficiency and the use of advanced modulation formats. With the immense advancements in DSP speeds, many of the problems hindering the use of coherent detection in optical transmission systems have been eliminated. Most notably, DSP alleviates the need for hardware phase-locking and polarization tracking, which can now be achieved in the digital domain. The complexity previously associated with coherent detection is hence significantly diminished and coherent detection is once gain considered a feasible detection alternative. In this thesis, several aspects of coherent detection (with or without subsequent DSP) are addressed. Coherent detection is presented as a means to extend the dispersion limit of a duobinary signal using an analog decision-directed phase-lock loop. Analytical bit-error ratio estimation for quadrature phase-shift keying signals is derived. To validate the promise for high spectral efficiency, the orthogonal-wavelength-division multiplexing scheme is suggested. In this scheme the WDM channels are spaced at the symbol rate, thus achieving the spectral efficiency limit. Theory, simulation and experimental results demonstrate the feasibility of this approach. Infinite impulse response filtering is shown to be an efficient alternative to finite impulse response filtering for chromatic dispersion compensation. Theory, design considerations, simulation and experimental results relating to this topic are presented. Interaction between fiber dispersion and nonlinearity remains the last major challenge

  9. Fiber-optic delay-line stabilization of heterodyne optical signal generator and method using same

    NASA Technical Reports Server (NTRS)

    Logan, Ronald T. (Inventor)

    1997-01-01

    The present invention is a laser heterodyne frequency generator system with a stabilizer for use in the microwave and millimeter-wave frequency ranges utilizing a photonic mixer as a photonic phase detector in a stable optical fiber delay-line. Phase and frequency fluctuations of the heterodyne laser signal generators are stabilized at microwave and millimeter wave frequencies by a delay line system operating as a frequency discriminator. The present invention is free from amplifier and mixer 1/.function. noise at microwave and millimeter-wave frequencies that typically limit phase noise performance in electronic cavity stabilized electronic oscillators. Thus, 1/.function. noise due to conventional mixers is eliminated and stable optical heterodyne generation of electrical signals is achieved.

  10. Multidimensional optical signal processing using optical coherent transient spatial-spectral holography

    NASA Astrophysics Data System (ADS)

    Anderson, Kenneth Edward

    This thesis presents analysis and experimental demonstrations of several new optical signal processing architectures that are based on optical coherent transient (OCT) technology and investigates many system design issues that must be taken into account when building such systems. OCT materials have the potential to optically process both high bandwidth (>10 GHz) and high time-bandwidth (>106) signals with the ability to potentially store huge amounts of data (up to 1000's of TB/cm3 using spatial-temporal holography. Several OCT system architectures are proposed and discussed including: raster image correlators, scanners, RF spectrum analyzers, time integrating correlators, image sequence correlators, and dynamic optical switches. In addition, some of the first experimental demonstrations of multiple channel spatial-temporal signal processing using OCT materials are shown. Novel system architectures for performing chromatic, polarization mode, and modal dispersion compensation are discussed, analyzed, and initial experimental results are shown demonstrating chromatic dispersion compensation of up to 5 mus of dispersion. A new approach for multiplexing 100's of individual DWDM channels of information down one multimode fiber is proposed and analyzed. In addition, a high bandwidth adaptive phased array beam steering system is also proposed and investigated along with experimental results showing the first demonstration of simultaneous time delay and processing of information with OCT materials. Lastly, results are presented for several stabilized lasers systems that have been built throughout the course of this research. The techniques used for stabilizing these lasers systems included optical feedback from gratings and Fabry-Perot cavities and electronic feedback techniques using Pound-Drever-Hall frequency locking.

  11. Constructive functional principles and control objectives executed with the device for optical signal splitting and chirping

    NASA Astrophysics Data System (ADS)

    Vinogradova, Irina L.; Andrianova, Anna V.; Meshkov, Ivan K.; Sultanov, Albert Kh.; Abdrakhmanova, Guzel I.; Grakhova, Elizaveta P.; Ishmyarov, Arsen A.; Yantilina, Liliya Z.; Kutlieva, Gulnaz R.

    2017-04-01

    This paper describes functional principles of a device for optical signal splitting and chirping. The offered device is to fulfill functions of such optical signal distortions compensation within FOCL RoF as linear attenuation (LA) and chromatic dispersion (CD); and it should also split optical signals for its feeding to radio emitting components, compounding aerial array (AA), and control radio emitting antenna lobe. In the meantime the device for optical signal splitting and chirping can inject losses into transferred signal, though they should be within tolerant values for conventional FOCL components.

  12. Impaired endolysosomal function disrupts Notch signaling in optic nerve astrocytes

    PubMed Central

    Valapala, Mallika; Hose, Stacey; Gongora, Celine; Dong, Lijin; Wawrousek, Eric F.; Zigler, J. Samuel; Sinha, Debasish

    2013-01-01

    Astrocytes migrate from the optic nerve into the inner retina, forming a template upon which retinal vessels develop. In the Nuc1 rat, mutation in the gene encoding βA3/A1-crystallin disrupts both Notch signaling in astrocytes and formation of the astrocyte template. Here we show that loss of βA3/A1-crystallin in astrocytes does not impede Notch ligand binding or extracellular cleavages. However, it affects V-ATPase activity, thereby compromising acidification of the endolysosomal compartments, leading to reduced γ-secretase-mediated processing and release of the Notch intracellular domain (NICD). Lysosomal-mediated degradation of Notch is also impaired. These defects decrease the level of NICD in the nucleus, inhibiting expression of Notch target genes. Overexpression of βA3/A1-crystallin in those same astrocytes restored V-ATPase activity and normal endolysosomal acidification, thereby increasing the levels of γ-secretase to facilitate optimal Notch signaling. We postulate that βA3/A1-crystallin is essential for normal endolysosomal acidification, and thereby, normal activation of Notch signaling in astrocytes. PMID:23535650

  13. Demodulation features of different types of signals for fiber-optic sensors

    NASA Astrophysics Data System (ADS)

    Zhang, Yabin; Sun, Xintong; Cao, Jianian; Zhang, Chao

    2010-11-01

    The detection abilities of PGC scheme dealing with the single frequency signal are investigated, based on which, the frequency domain of the signal is analyzed. Based on the Bessel function theoretic, the mathematical model has been established to analyze the performance of interferometric fiber-optic sensor under the PGC demodulation scheme. The spectrums of interferometer output signals are analyzed when the input signal is single frequency signal and multifrequency signal. Simulation results show that the dynamic domain upper limit of fiber-optic sensor when it operates with the multi-frequency signal must be much smaller than that it operates the single frequency signal.

  14. Control of germline stem cell self-renewal and differentiation in the Drosophila ovary: concerted actions of niche signals and intrinsic factors.

    PubMed

    Xie, Ting

    2013-01-01

    In the Drosophila ovary, germline stem cells (GSCs) physically interact with their niche composed of terminal filament cells, cap cells, and possibly GSC-contacting escort cells (ECs). A GSC divides to generate a self-renewing stem cell that remains in the niche and a differentiating daughter that moves away from the niche. The GSC niche provides a bone morphogenetic protein (BMP) signal that maintains GSC self-renewal by preventing stem cell differentiation via repression of the differentiation-promoting gene bag of marbles (bam). In addition, it expresses E-cadherin, which mediates cell adhesion for anchoring GSCs in the niche, enabling continuous self-renewal. GSCs themselves also express different classes of intrinsic factors, including signal transducers, transcription factors, chromatin remodeling factors, translation regulators, and miRNAs, which control self-renewal by strengthening interactions with the niche and repressing various differentiation pathways. Differentiated GSC daughters, known as cystoblasts (CBs), also express distinct classes of intrinsic factors to inhibit self-renewal and promote germ cell differentiation. Surprisingly, GSC progeny are also dependent on their surrounding ECs for proper differentiation at least partly by preventing BMP from diffusing to the differentiated germ cell zone and by repressing ectopic BMP expression. Therefore, both GSC self-renewal and CB differentiation are controlled by collaborative actions of extrinsic signals and intrinsic factors.

  15. a Study of Signal Attenuation in Spooled Optical Fiber Cables

    NASA Astrophysics Data System (ADS)

    Ruffin, Paul B.

    Signal attenuation in precision-wound optical fibers has been investigated. A fiber winding apparatus was designed and built to produce precision-wound bobbins. Fiber winding tension dependence on excess loss was studied by winding a parabolic-index profile fiber onto a cylindrical spool under different winding tensions. An Optical Time Domain Reflectometer was used to perform layer-dependent, signal-loss measurements. Initial data indicated that the excess loss (extremely large) in a freshly wound bobbin continued to decrease over a period of several weeks. However, soaking the bobbins at the annealing temperature of the fiber-coating material caused an enormous reduction in excess loss. An analytical model was developed to correlate the data. Two signal loss mechanisms were identified, fiber axis bending and fiber core microdistortion at the fiber crossover sites. Computer programs were written to calculate the mode coupling coefficients and signal loss in a multimode fiber. The temperature dependence of excess loss was also investigated. Relying on the credibility of the heat-treatment process applied to bobbins to relieve the uneven stresses, it was determined that the fiber microbending at the crossover sites is the primary cause of excess loss. Microdistortion of the fiber core at the fiber crossovers becomes more severe as the lateral pressures are increased due to increased winding tension, increased number of wound layers, and decreased spool diameter. Fiber buckling due to the difference of the thermal expansion coefficient of the buffer coat and the fiber had a negligible effect on excess loss. However, it was found that the Young's Modulus increase and the lateral shrinkage of the buffer coat at low temperature were responsible for the temperature dependence of loss increase. Enhanced microbending of the fiber at the crossover sites was responsible for 30 and 42 percent of the excess loss at -30(DEGREES)C for 100 and 250 grams winding tension

  16. Fiber optic signal amplifier using thermoelectric power generation

    DOEpatents

    Hart, Mark M.

    1995-01-01

    A remote fiber optic signal amplifier for use as a repeater/amplifier, such as in transoceanic communications, powered by a Pu.sub.238 or Sr.sub.90 thermoelectric generator. The amplifier comprises a unit with connections on the receiving and sending sides of the communications system, and an erbium-doped fiber amplifier connecting each sending fiber to each receiving fiber. The thermoelectric generator, preferably a Pu.sub.238 or Sr.sub.90 thermoelectric generator delivers power to the amplifiers through a regulator. The heat exchange surfaces of the thermoelectric generator are made of materials resistant to corrosion and biological growth and are directly exposed to the outside, such as the ocean water in transoceanic communications.

  17. Fiber optic signal amplifier using thermoelectric power generation

    DOEpatents

    Hart, M.M.

    1993-01-01

    A remote fiber optic signal amplifier for use as a repeater/amplifier, such as in transoceanic communication, powered by a Pu{sub 238} or Sr{sub 90} thermoelectric generator. The amplifier comprises a unit with connections on the receiving and sending sides of the communications system, and an erbium-doped fiber amplifier connecting each sending fiber to each receiving fiber. The thermoelectric generator, preferably a Pu{sub 238} or Sr{sub 90} thermoelectric generator delivers power to the amplifiers through a regulator. The heat exchange surfaces of the thermoelectric generator are made of material resistant to corrosion and biological growth and are directly exposed to the outside, such as the ocean water in transoceanic communications.

  18. Fiber optic signal amplifier using thermoelectric power generation

    DOEpatents

    Hart, M.M.

    1995-04-18

    A remote fiber optic signal amplifier for use as a repeater/amplifier, such as in transoceanic communications, powered by a Pu{sub 238} or Sr{sub 90} thermoelectric generator. The amplifier comprises a unit with connections on the receiving and sending sides of the communications system, and an erbium-doped fiber amplifier connecting each sending fiber to each receiving fiber. The thermoelectric generator, preferably a Pu{sub 238} or Sr{sub 90} thermoelectric generator delivers power to the amplifiers through a regulator. The heat exchange surfaces of the thermoelectric generator are made of materials resistant to corrosion and biological growth and are directly exposed to the outside, such as the ocean water in transoceanic communications. 2 figs.

  19. Fiber optic signal distribution for phased array antennas

    NASA Astrophysics Data System (ADS)

    Mecherle, G. S.

    1992-03-01

    The use of a 32-GHz phased-array transmitting antenna with fiberoptic signal distribution is considered in the context of a Mars relay satellite for NASA's Space Exploration Initiative. The specifications of the proposed application are assessed with specific attention given to the EIRP requirement of 86 dBW and its ramifications on the phased array, antenna, and photonic architecture. A photonic performance analysis is conducted to study phase-noise and SNR degradations to determine whether phase-locked loop (PLL) complexity is required. SNR and phase noise are examined as a function of the number of optical splits, and the number is shown to be limited to 350. Use of the PLL allows one laser to support 650 elements - as opposed to 250 - showing that only a single laser diode is needed to support the array for the Mars transmitter.

  20. The Study of the Phase Characteristics of Bragg Cells for Acousto-Optic Signal Processing

    DTIC Science & Technology

    1998-01-01

    THE FINAL REPORT ON THE SPECIAL CONTRACT SPC-97-4025 The Study of the Phase Characteristics of Bragg Cells for Acousto - Optic Signal Processing...for Acousto - Optic Signal Processing Unclassified 5a. CONTRACT NUMBER F6170897W0095 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) Yurchenko...Characteristics of Bragg Cells for Acousto - Optic Signal Processing 5. FUNDING NUMBERS F6170897W0095 6. AUTHOR(S) Dr. Alexander Yurchenko 7. PERFORMING

  1. Impacts of Underwater Turbulence on Acoustical and Optical Signals and Their Linkage

    DTIC Science & Technology

    2013-02-12

    convected quantities like temperature in turbulence fluid," J. Fluid Mech. 5,113-133(1959). 26. J. W. Goodman , Introduction to Fourier Optics (Roberts...Turbulence on Acoustical and Optical Signals and Their Linkage 5a. CONTRACT NUMBER 5b. GRANT NUMBER 5c. PROGRAM ELEMENT NUMBER 0602782N 6...Acoustical and optical signal transmission underwater is of vital interest for both civilian and military applications. The range and signal to noise

  2. Signal digitizing system and method based on amplitude-to-time optical mapping

    DOEpatents

    Chou, Jason; Bennett, Corey V; Hernandez, Vince

    2015-01-13

    A signal digitizing system and method based on analog-to-time optical mapping, optically maps amplitude information of an analog signal of interest first into wavelength information using an amplitude tunable filter (ATF) to impress spectral changes induced by the amplitude of the analog signal onto a carrier signal, i.e. a train of optical pulses, and next from wavelength information to temporal information using a dispersive element so that temporal information representing the amplitude information is encoded in the time domain in the carrier signal. Optical-to-electrical conversion of the optical pulses into voltage waveforms and subsequently digitizing the voltage waveforms into a digital image enables the temporal information to be resolved and quantized in the time domain. The digital image may them be digital signal processed to digitally reconstruct the analog signal based on the temporal information with high fidelity.

  3. Acousto-Optic Processing of 2-D Signals Using Temporal and Spatial Integration.

    DTIC Science & Technology

    1986-04-29

    AD-AI?3 411 ACOUSTO - OPTIC PROCESSING OF 2-D SIGNALS USING TEMPORAL 1/ AND SPATIAL INTEGR..(U) CRLIFORNIA INST OF TECH PASADENA DEPT OF ELECTRICAL...LECTE 3 FINAL REORT4 Submitted to: Al FORCE OFFICE OF SCIENTIFIC RESEARCH Grant Number AFOSR-82-0128 :A of % ACOUSTO - OPTIC PROCISSING OF 2-D SIGNALS...Psaltis, Applied Optics, Vol. 21, No. 3, 1 February 1982. (3) " Acousto - Optic /CCD Image Processor, Demetri Psaltis, Eung Gi Paek and Santosh Venkatesh

  4. Laser Sources And Detectors For Guided Wave Optical Signal Processing

    NASA Astrophysics Data System (ADS)

    Meingailis, I.

    1980-12-01

    Significant advances have been made in the development of high-performance diode laser sources and photodiode detectors that will be essential for future optical signal processing systems. AIG aAs/G aAs diode lasers for 0.8 to 0.9 um wavelengths are now commercially available and GalnAsP/InP for 0.9 to 1.7µm should soon become available. Recent achievements include long lifetime lasers (>10,000 hours) in both materials systems, single longitudinal and transverse mode operation, high speed pulse modulation (1Gbit/sec), and mode-locked operation with <20 psec pulses. High performance avalanche photodiodes have been developed in Si for wavelengths up to 0.9 uM and modest-performance diodes in Ge up to 1.5 um. For wavelengths beyond 1 uM, III-V compounds, especially the GaInAsP/InP system, show promise for fast, highly sensitive diodes that could be integrated into optical waveguide circuits along with diode lasers.

  5. Effect of sputtering power on crystallinity, intrinsic defects, and optical and electrical properties of Al-doped ZnO transparent conducting thin films for optoelectronic devices

    NASA Astrophysics Data System (ADS)

    Hu, Yu Min; Li, Jung Yu; Chen, Nai Yun; Chen, Chih Yu; Han, Tai Chun; Yu, Chin Chung

    2017-02-01

    The crystallinity and intrinsic defects of transparent conducting oxide (TCO) films have a high impact on their optical and electrical properties and therefore on the performance of devices incorporating such films, including flat panel displays, electro-optical devices, and solar cells. The optical and electrical properties of TCO films can be modified by tailoring their deposition parameters, which makes proper understanding of these parameters crucial. Magnetron sputtering is the most adaptable method for preparing TCO films used in industrial applications. In this study, we investigate the direct and inter-property correlation effects of sputtering power (PW) on the crystallinity, intrinsic defects, and optical and electrical properties of Al-doped ZnO (AZO) TCO films. All of the films were preferentially c-axis-oriented with a wurtzite structure and had an average transmittance of over 80% in the visible wavelength region. Scanning electron microscopy images revealed significantly increased AZO film grain sizes for PW ≥ 150 W, which may lead to increased conductivity, carrier concentration, and optical band gaps but decreased carrier mobility and in-plane compressive stress in AZO films. Photoluminescence results showed that, with increasing PW, the near band edge emission gradually dominates the defect-related emissions in which zinc interstitial (Zni), oxygen vacancy (VO), and oxygen interstitial (Oi) are possibly responsible for emissions at 3.08, 2.8, and 2.0 eV, respectively. The presence of Zni- and Oi-related emissions at PW ≥ 150 W indicates a slight increase in the presence of Al atoms substituted at Zn sites (AlZn). The presence of Oi at PW ≥ 150 W was also confirmed by X-ray photoelectron spectroscopy results. These results clearly show that the crystallinity and intrinsic-defect type of AZO films, which dominate their optical and electrical properties, may be controlled by PW. This understanding may facilitate the development of TCO

  6. Iridescent flowers? Contribution of surface structures to optical signaling.

    PubMed

    van der Kooi, Casper J; Wilts, Bodo D; Leertouwer, Hein L; Staal, Marten; Elzenga, J Theo M; Stavenga, Doekele G

    2014-07-01

    The color of natural objects depends on how they are structured and pigmented. In flowers, both the surface structure of the petals and the pigments they contain determine coloration. The aim of the present study was to assess the contribution of structural coloration, including iridescence, to overall floral coloration. We studied the reflection characteristics of flower petals of various plant species with an imaging scatterometer, which allows direct visualization of the angle dependence of the reflected light in the hemisphere above the petal. To separate the light reflected by the flower surface from the light backscattered by the components inside (e.g. the vacuoles), we also investigated surface casts. A survey among angiosperms revealed three different types of floral surface structure, each with distinct reflections. Petals with a smooth and very flat surface had mirror-like reflections and petal surfaces with cones yielded diffuse reflections. Petals with striations yielded diffraction patterns when single cells were illuminated. The iridescent signal, however, vanished when illumination similar to that found in natural conditions was applied. Pigmentary rather than structural coloration determines the optical appearance of flowers. Therefore, the hypothesized signaling by flowers with striated surfaces to attract potential pollinators presently seems untenable. © 2014 The Authors. New Phytologist © 2014 New Phytologist Trust.

  7. Transmission of multiplexed video signals in multimode optical fiber systems

    NASA Technical Reports Server (NTRS)

    White, Preston, III

    1988-01-01

    Kennedy Space Center has the need for economical transmission of two multiplexed video signals along multimode fiberoptic systems. These systems must span unusual distances and must meet RS-250B short-haul standards after reception. Bandwidth is a major problem and studies of the installed fibers, available LEDs and PINFETs led to the choice of 100 MHz as the upper limit for the system bandwidth. Optical multiplexing and digital transmission were deemed inappropriate. Three electrical multiplexing schemes were chosen for further study. Each of the multiplexing schemes included an FM stage to help meet the stringent S/N specification. Both FM and AM frequency division multiplexing methods were investigated theoretically and these results were validated with laboratory tests. The novel application of quadrature amplitude multiplexing was also considered. Frequency division multiplexing of two wideband FM video signal appears the most promising scheme although this application requires high power highly linear LED transmitters. Futher studies are necessary to determine if LEDs of appropriate quality exist and to better quantify performance of QAM in this application.

  8. Transmission of multiplexed video signals in multimode optical fiber systems

    NASA Astrophysics Data System (ADS)

    White, Preston, III

    1988-10-01

    Kennedy Space Center has the need for economical transmission of two multiplexed video signals along multimode fiberoptic systems. These systems must span unusual distances and must meet RS-250B short-haul standards after reception. Bandwidth is a major problem and studies of the installed fibers, available LEDs and PINFETs led to the choice of 100 MHz as the upper limit for the system bandwidth. Optical multiplexing and digital transmission were deemed inappropriate. Three electrical multiplexing schemes were chosen for further study. Each of the multiplexing schemes included an FM stage to help meet the stringent S/N specification. Both FM and AM frequency division multiplexing methods were investigated theoretically and these results were validated with laboratory tests. The novel application of quadrature amplitude multiplexing was also considered. Frequency division multiplexing of two wideband FM video signal appears the most promising scheme although this application requires high power highly linear LED transmitters. Futher studies are necessary to determine if LEDs of appropriate quality exist and to better quantify performance of QAM in this application.

  9. Modulation Code and Signal Characteristics for Signal Waveform Modulation Optical Disc

    NASA Astrophysics Data System (ADS)

    Liu, Hailong; Pei, Jing; Pan, Longfa; Ni, Yi

    2010-08-01

    A high-efficient and novel varying-level multilevel run-length-limited modulation code is proposed for signal waveform modulation (SWM) optical discs. The proposed code is composed of a maximum transition run (MTR) code and a level modulation process. The MTR code is employed to realize high code rate and satisfy the requirements of channels. Level modulation is used to eliminate inappropriate codewords for SWM channels and determine the level numbers for different runs. The rate of the presented code is 7/8 bits/symbols, and the recording density parameter RBPF (recording bits per 400 nm) is 2.26, which is 50.7% more than that of a digital versatile disc (DVD). The realization of the proposed code in SWM discs and the corresponding signal characteristics are also shown. With the run-length detection and level detection solution, the bit error rate (BER) is less than 2×10-4, which is feasible for SWM multilevel optical discs.

  10. Coherent detection and digital signal processing for fiber optic communications

    NASA Astrophysics Data System (ADS)

    Ip, Ezra

    The drive towards higher spectral efficiency in optical fiber systems has generated renewed interest in coherent detection. We review different detection methods, including noncoherent, differentially coherent, and coherent detection, as well as hybrid detection methods. We compare the modulation methods that are enabled and their respective performances in a linear regime. An important system parameter is the number of degrees of freedom (DOF) utilized in transmission. Polarization-multiplexed quadrature-amplitude modulation maximizes spectral efficiency and power efficiency as it uses all four available DOF contained in the two field quadratures in the two polarizations. Dual-polarization homodyne or heterodyne downconversion are linear processes that can fully recover the received signal field in these four DOF. When downconverted signals are sampled at the Nyquist rate, compensation of transmission impairments can be performed using digital signal processing (DSP). Software based receivers benefit from the robustness of DSP, flexibility in design, and ease of adaptation to time-varying channels. Linear impairments, including chromatic dispersion (CD) and polarization-mode dispersion (PMD), can be compensated quasi-exactly using finite impulse response filters. In practical systems, sampling the received signal at 3/2 times the symbol rate is sufficient to enable an arbitrary amount of CD and PMD to be compensated for a sufficiently long equalizer whose tap length scales linearly with transmission distance. Depending on the transmitted constellation and the target bit error rate, the analog-to-digital converter (ADC) should have around 5 to 6 bits of resolution. Digital coherent receivers are naturally suited for the implementation of feedforward carrier recovery, which has superior linewidth tolerance than phase-locked loops, and does not suffer from feedback delay constraints. Differential bit encoding can be used to prevent catastrophic receiver failure due

  11. Ultra-high speed optical signal processing through third-order fiber nonlinearity (Invited Paper)

    NASA Astrophysics Data System (ADS)

    Kikuchi, Kazuro

    2005-04-01

    Third-order optical nonlinearity in optical fibers has many attractive applications to all-optical signal processing that will be employed in future large-capacity photonic networks. After reviewing the third-order nonlinear optical property of optical fibers, we describe our recent experimental results on all-optical signal processing functions such as wideband wavelength conversion, ultrafast gate switching, and ultrafast pulse reshaping. These functions are based on self-phase modulation (SPM), cross-phase modulation (XPM), and four-wave mixing (FWM) in nonlinear fibers.

  12. Precursory Acoustic Signals Detection in Rockfall Events by Means of Optical Fiber Sensors

    NASA Astrophysics Data System (ADS)

    Schenato, L.; Marcato, G.; Gruca, G.; Iannuzzi, D.; Palmieri, L.; Galtarossa, A.; Pasuto, A.

    2012-12-01

    -electric transducer (PZT) and results, while not yet conclusive, confirm that FOSs may represent a viable approach to AE detection for unstable rock masses monitoring; experimental results suggest also that FOSs could be intrinsically more sensitive to volumes waves, whereas PZT seems more sensitive to surface waves.; Signals (top row) and corresponding PSDs (bottom row) recorded by the two fiber optical sensors (FCS, fiber coil sensor; FTC, ferrule-top cantilever) and by a traditional high-sensitive piezo-electric sensor (PZT, piezo-electric transducer).

  13. Thermo-optic silica PLC devices for applications in high speed optical signal processing

    NASA Astrophysics Data System (ADS)

    Blanchetiere, Chantal; Callender, Claire L.; Jacob, Sarkis; Ledderhof, Christopher J.; Dumais, Patrick; Celo, Dritan; Chen, Lawrence R.; Samadi, Payman

    2011-08-01

    The optimization of a 2×2 silica-on-silicon Mach-Zehnder interferometer (MZI) thermo-optic switch is presented. The device consists of 2 multimode interference (MMI) couplers as splitter and combiner with metal heater strips for phase control. The switching characteristics of the devices have been examined in detail as a function of several parameters. The electrical power consumption of the switch has been reduced by a factor of 2 by etching trenches alongside the waveguide heaters located on the arms of the MZI, and the polarization dependent loss has been controlled and reduced through adjustment of top cladding properties. The effect on the response time of the switch of these design changes has been investigated. Detailed characterization of the devices will be presented, and trade-offs in optimization discussed. Incorporation of these device elements into increasingly complex components for new applications in optical signal processing will be demonstrated.

  14. Optical signal processing for enabling high-speed, highly spectrally efficient and high capacity optical systems

    NASA Astrophysics Data System (ADS)

    Fazal, Muhammad Irfan

    may be possible. Recently, interest has increased in exploring the spatial dimension of light to increase capacity, both in fiber as well as free-space communication channels. The orbital angular momentum (OAM) of light, carried by Laguerre-Gaussian (LG) beams have the interesting property that, in theory, an infinite number of OAMs can be transmitted; which due to its inherent orthogonality will not affect each other. Thus, in theory, one can increase the channel capacity arbitrarily. However, in practice, the device dimensions will reduce the number of OAMs used. In addition to advanced modulation formats, it is expected that optical signal processing may play a role in the future development of more efficient optical transmission systems. The hope is that performing signal processing in the optical domain may reduce optical-to-electronic conversion inefficiencies, eliminate bottlenecks and take advantage of the ultrahigh bandwidth inherent in optics. While 40 to 50 Gbit/s electronic components are the peak of commercial technology and 100 Gbit/s capable RF components are still in their infancy, optical signal processing of these high-speed data signals may provide a potential solution. Furthermore, any optical processing system or sub-system must be capable of handling the wide array of data formats and data rates that networks may employ. The work presented in this Ph.D. dissertation attempts at addressing the issue of optical processing for advanced optical modulation formats, and particularly explores the state of the art in increasing the capacity of an optical link by a combination of wavelength/phase/polarization/OAM dimensions of light. Spatial multiplexing and demultiplexing of both coherently and directly detected signals at the 100 Gbit/s Ethernet standard is addressed. The application of a continuously tunable all-optical delay for all-optical functionality like time-slot interchange at high data-rates is presented. Moreover the interplay of chirp

  15. Adaptive threshold adjustment for signal-distortion-free digital-coherent optical demodulation system.

    PubMed

    Chiba, Akito; Sakamoto, Takahide; Kawanishi, Tetsuya

    2008-12-22

    Optical quadrature amplitude modulation (QAM) attracts considerable attention in the enhancement of communications capacity, due to its high spectral efficiency. However, this modulation format is more sensitive to signal distortion than conventional formats, making it more difficult to create, transmit, and detect signals. In this paper, we propose an adaptive scheme for demodulation of the distorted optical signals with paying attention to use of DSP-technology. The scheme is based on the adjustment of the thresholds against the signal distortion. Successful demodulation of optical QAM signals is demonstrated with a sufficiently low bit-error rate.

  16. Dietary chlorophyllin inhibits the canonical NF-κB signaling pathway and induces intrinsic apoptosis in a hamster model of oral oncogenesis.

    PubMed

    Thiyagarajan, P; Senthil Murugan, R; Kavitha, K; Anitha, P; Prathiba, D; Nagini, S

    2012-03-01

    Chlorophyllin, a water-soluble, semi-synthetic derivative of the ubiquitous green pigment chlorophyll is shown to exert potent anticarcinogenic effects. In the present study, we investigated the chemopreventive effects of chlorophyllin on 7,12-dimethylbenz(a)anthracene (DMBA)-induced hamster buccal pouch (HBP) carcinogenesis by analyzing the expression of NF-κB family members and markers of intrinsic apoptosis. Dietary administration of chlorophyllin (4 mg/kg bw) suppressed the development of HBP carcinomas by inhibiting the canonical NF-κB signaling pathway by downregulating IKKβ, preventing the phosphorylation of IκB-α, and reducing the expression of nuclear NF-κB. Inactivation of NF-κB signaling by chlorophyllin was associated with the induction of intrinsic apoptosis as evidenced by modulation of Bcl-2 family proteins, enforced nuclear localization of survivin, upregulation of apoptogenic molecules, activation of caspases, and cleavage of PARP. The results of the present study demonstrate that chlorophyllin inhibits the development of DMBA-induced HBP carcinogenesis by targeting NF-κB and the intrinsic apoptotic pathway. Thus, dietary agents such as chlorophyllin that simultaneously target divergent pathways of cell survival and cell death are novel candidates for cancer chemoprevention.

  17. Spectral and spatial dependence of
diffuse optical signals in response to
peripheral nerve stimulation

    PubMed Central

    Chen, Debbie K.; Erb, M. Kelley; Tong, Yunjie; Yu, Yang; Sassaroli, Angelo; Bergethon, Peter R.; Fantini, Sergio

    2010-01-01

    Using non-invasive, near-infrared spectroscopy we have previously reported optical signals measured at or around peripheral nerves in response to their stimulation. Such optical signals featured amplitudes on the order of 0.1% and peaked about 100 ms after peripheral nerve stimulation in human subjects. Here, we report a study of the spatial and spectral dependence of the optical signals induced by stimulation of the human median and sural nerves, and observe that these optical signals are: (1) unlikely due to either dilation or constriction of blood vessels, (2) not associated with capillary bed hemoglobin, (3) likely due to blood vessel(s) displacement, and (4) unlikely due to fiber-skin optical coupling effects. We conclude that the most probable origin of the optical response to peripheral nerve stimulation is from displacement of blood vessels within the optically probed volume, as a result of muscle twitch in adjacent areas. PMID:21258519

  18. Detection of optical neuronal signals in the visual cortex using continuous wave near-infrared spectroscopy.

    PubMed

    Sun, Bailei; Zhang, Lei; Gong, Hui; Sun, Jinyan; Luo, Qingming

    2014-02-15

    Near-infrared spectroscopy (NIRS) measures slow hemodynamic signals noninvasively to indirectly infer the neuronal activity in the brain. However, it remains a controversy on whether this optical measurement technique can detect the optical neuronal signal, which reflects the optical changes directly associated with neuronal activity, within the visual cortex of human and non-human primates. By carefully reviewing the important factors in the detection of optical neuronal signals, we aim to investigate the feasibility of performing NIRS measurements of optical neuronal signals within the visual cortex in humans. To ensure a strong optical neuronal response, a full-field circular black and white reversing checkerboard stimulus was presented, and the reversal frequency was carefully chosen. We used a homemade continuous wave (CW) NIRS system with high detection sensitivity (of the order of 0.1 pW) to record a large area of the visual cortex (approximately 6 × 14 cm(2)). EEG was simultaneously acquired with the optical signal. Based on the mathematical morphology, we adapted the filter proposed by Gratton et al. to remove the influence of arterial pulsation and facilitate the detection and elimination of unknown artifacts from the data. We obtained reliable optical neuronal signals in 77% of the participants (10 out of 13). The amplitudes (latencies) of the obtained optical neuronal signals corresponding to the 785 and 850 nm wavelengths were 0.017 ± 0.003% (94.7 ± 8.4 ms) and 0.025 ± 0.006% (99.0 ± 7.7 ms), respectively. There were no significant differences between the latencies of the N75 component of the visual evoked potential (VEP) and optical neuronal signals at either wavelength. This is the first study to report optical neuronal signals within the visual cortex in the intact human brain using a CW NIRS system. These results indicate the feasibility of measuring noninvasive optical neuronal signals using a CW NIRS system with high detection sensitivity.

  19. Intrinsic MyD88-Akt1-mTOR Signaling Coordinates Disparate Tc17 and Tc1 Responses during Vaccine Immunity against Fungal Pneumonia.

    PubMed

    Nanjappa, Som Gowda; Hernández-Santos, Nydiaris; Galles, Kevin; Wüthrich, Marcel; Suresh, M; Klein, Bruce S

    2015-09-01

    Fungal infections have skyrocketed in immune-compromised patients lacking CD4+ T cells, underscoring the need for vaccine prevention. An understanding of the elements that promote vaccine immunity in this setting is essential. We previously demonstrated that vaccine-induced IL-17A+ CD8+ T cells (Tc17) are required for resistance against lethal fungal pneumonia in CD4+ T cell-deficient hosts, whereas the individual type I cytokines IFN-γ, TNF-α and GM-CSF, are dispensable. Here, we report that T cell-intrinsic MyD88 signals are crucial for these Tc17 cell responses and vaccine immunity against lethal fungal pneumonia in mice. In contrast, IFN-γ+ CD8+ cell (Tc1) responses are largely normal in the absence of intrinsic MyD88 signaling in CD8+ T cells. The poor accumulation of MyD88-deficient Tc17 cells was not linked to an early onset of contraction, nor to accelerated cell death or diminished expression of anti-apoptotic molecules Bcl-2 or Bcl-xL. Instead, intrinsic MyD88 was required to sustain the proliferation of Tc17 cells through the activation of mTOR via Akt1. Moreover, intrinsic IL-1R and TLR2, but not IL-18R, were required for MyD88 dependent Tc17 responses. Our data identify unappreciated targets for augmenting adaptive immunity against fungi. Our findings have implications for designing fungal vaccines and immune-based therapies in immune-compromised patients.

  20. Experimental evidence of signal-optical noise interferencelike effect in underwater amplitude-modulated laser optical radar systems.

    PubMed

    Bartolini, L; De Dominicis, L; Ferri de Collibus, M; Fornetti, G; Francucci, M; Guarneri, M; Nuvoli, M; Paglia, E; Ricci, R

    2008-11-15

    We report experimental evidence that in an amplitude-modulated laser optical radar system for underwater 3D imaging the observed contrast oscillations as a function of the modulation frequency originate from an interference-like effect between target signal VT and water backscattered radiation VW. The demonstration relies on the ability to perform a direct measurement of VW in a 25 m long test tank. The proposed data processing method enables one to remove the contribution of water backscattering from the detected signal and drastically reduce signal fluctuations due to the medium. Experiments also confirm the possibility to improve the signal to optical noise ratio and contrast by increasing the modulation frequency.

  1. Integrated Pointing and Signal Detector for Optical Receiver

    NASA Technical Reports Server (NTRS)

    Britcliffe, Michael; Hoppe, Daniel

    2005-01-01

    A design concept for the receiver portion of a proposed free-space optical-communication terminal calls for integration of its communication and pointing detectors. As explained below, this would entail a departure from prior designs, in which pointing and communication detectors have been separate. As used here, communication detector denotes a single high-speed photodetector used for reception of a laser beam that has been modulated to convey information, while pointing detector denotes an array of photodetectors (typically, a quad-cell detector or a charge-coupled device) used in sensing the pointing error (the error in the aim of a receiver telescope, relative to the laser-beam axis). The pointing detector of this or any free-space optical-communication receiver is necessary for proper acquisition and tracking of the received laser beam. The suitably processed output of the pointing detector is fed back to a fine-steering mirror to reduce any pointing error and thereby maintain optimum reception. Heretofore, it has been common practice to pass the incoming laser beam through a beam splitter that sends about 10 percent of the beam power to a pointing detector and the rest to a separate communication detector, as illustrated in the upper part of the figure. One disadvantage of this is that because only 10 percent of the received signal power is available for use by the pointing detector, the signal-to-noise ratio (SNR) at the pointing detector is lower than it otherwise would be. The performance of the pointing detector is correspondingly limited. Another disadvantage is that the alignment between the communication and pointing detectors is critical and must be ensured by means of a calibration procedure. According to the proposal, there would be no beam splitter. The communication and pointing detectors would be positioned coaxially in the same focal plane, as shown in the lower part of the figure: the communication detector would occupy the central part of the

  2. Mechanical signals at the base of a rat vibrissa: the effect of intrinsic vibrissa curvature and implications for tactile exploration

    PubMed Central

    Quist, Brian W.

    2012-01-01

    Rats actively tap and sweep their large mystacial vibrissae (whiskers) against objects to tactually explore their surroundings. When a vibrissa makes contact with an object, it bends, and this bending generates forces and bending moments at the vibrissa base. Researchers have only recently begun to quantify these mechanical variables. The present study quantifies the forces and bending moments at the vibrissa base with a quasi-static model of vibrissa deflection. The model was validated with experiments on real vibrissae. Initial simulations demonstrated that almost all vibrissa-object collisions during natural behavior will occur with the concave side of the vibrissa facing the object, and we therefore paid particular attention to the role of the vibrissa's intrinsic curvature in shaping the forces at the base. Both simulations and experiments showed that vibrissae with larger intrinsic curvatures will generate larger axial forces. Simulations also demonstrated that the range of forces and moments at the vibrissal base vary over approximately three orders of magnitude, depending on the location along the vibrissa at which object contact is made. Both simulations and experiments demonstrated that collisions in which the concave side of the vibrissa faces the object generate longer-duration contacts and larger net forces than collisions with the convex side. These results suggest that the orientation of the vibrissa's intrinsic curvature on the mystacial pad may increase forces during object contact and provide increased sensitivity to detailed surface features. PMID:22298834

  3. Imaging Odor-Evoked Activities in the Mouse Olfactory Bulb using Optical Reflectance and Autofluorescence Signals

    PubMed Central

    Chery, Romain; L'Heureux, Barbara; Bendahmane, Mounir; Renaud, Rémi; Martin, Claire; Pain, Frédéric; Gurden, Hirac

    2011-01-01

    In the brain, sensory stimulation activates distributed populations of neurons among functional modules which participate to the coding of the stimulus. Functional optical imaging techniques are advantageous to visualize the activation of these modules in sensory cortices with high spatial resolution. In this context, endogenous optical signals that arise from molecular mechanisms linked to neuroenergetics are valuable sources of contrast to record spatial maps of sensory stimuli over wide fields in the rodent brain. Here, we present two techniques based on changes of endogenous optical properties of the brain tissue during activation. First the intrinsic optical signals (IOS) are produced by a local alteration in red light reflectance due to: (i) absorption by changes in blood oxygenation level and blood volume (ii) photon scattering. The use of in vivo IOS to record spatial maps started in the mid 1980's with the observation of optical maps of whisker barrels in the rat and the orientation columns in the cat visual cortex1. IOS imaging of the surface of the rodent main olfactory bulb (OB) in response to odorants was later demonstrated by Larry Katz's group2. The second approach relies on flavoprotein autofluorescence signals (FAS) due to changes in the redox state of these mitochondrial metabolic intermediates. More precisely, the technique is based on the green fluorescence due to oxidized state of flavoproteins when the tissue is excited with blue light. Although such signals were probably among the first fluorescent molecules recorded for the study of brain activity by the pioneer studies of Britton Chances and colleagues3, it was not until recently that they have been used for mapping of brain activation in vivo. FAS imaging was first applied to the somatosensory cortex in rodents in response to hindpaw stimulation by Katsuei Shibuki's group4. The olfactory system is of central importance for the survival of the vast majority of living species because it

  4. Optical signal inverter of erbium-doped yttrium aluminum garnet with red shift of laser diodes.

    PubMed

    Maeda, Y

    1994-08-10

    An optical signal inverter was demonstrated in a simple structure that combined a laser diode with Er-doped YAG crystal. The optical signal inversion occurred at a response time of 7 ns and was caused by the decrease of transmission of Er:YAG against the red shift of the wavelength of the laser diode.

  5. Coherent (photon) vs incoherent (current) detection of multidimensional optical signals from single molecules in open junctions

    SciTech Connect

    Agarwalla, Bijay Kumar; Hua, Weijie; Zhang, Yu; Mukamel, Shaul; Harbola, Upendra

    2015-06-07

    The nonlinear optical response of a current-carrying single molecule coupled to two metal leads and driven by a sequence of impulsive optical pulses with controllable phases and time delays is calculated. Coherent (stimulated, heterodyne) detection of photons and incoherent detection of the optically induced current are compared. Using a diagrammatic Liouville space superoperator formalism, the signals are recast in terms of molecular correlation functions which are then expanded in the many-body molecular states. Two dimensional signals in benzene-1,4-dithiol molecule show cross peaks involving charged states. The correlation between optical and charge current signal is also observed.

  6. Mechanism for improving the signal-to-noise ratio in scanning optical microscopes

    NASA Astrophysics Data System (ADS)

    Milster, Tom D.; Walker, Edwin P.

    1996-08-01

    We demonstrate an improved signal-to-noise ratio in a scanning optical microscope used to read out information from a magneto-optical data storage layer. By placing a shading band in the return path of the optical system we can reduce noise by as much as 3 dB in certain spatial frequency ranges. The signal-to-noise ratio improvement arises from differences in the signal and noise distributions in the pupil of the optical system. Although the experimental results are shown only in one dimension, the concept is applicable to two-dimensional scanning of low-contrast samples.

  7. Enhanced correlation of received power-signal fluctuations in bidirectional optical links

    NASA Astrophysics Data System (ADS)

    Minet, Jean; Vorontsov, Mikhail A.; Polnau, Ernst; Dolfi, Daniel

    2013-02-01

    A study of the correlation between the power signals received at both ends of bidirectional free-space optical links is presented. By use of the quasi-optical approximation, we show that an ideal (theoretically 100%) power-signal correlation can be achieved in optical links with specially designed monostatic transceivers based on single-mode fiber collimators. The theoretical prediction of enhanced correlation is supported both by experiments conducted over a 7 km atmospheric path and wave optics numerical analysis of the corresponding bidirectional optical link. In the numerical simulations, we also compare correlation properties of received power signals for different atmospheric conditions and for optical links with monostatic and bistatic geometries based on single-mode fiber collimator and on power-in-the-bucket transceiver types. Applications of the observed phenomena for signal fading mitigation and turbulence-enhanced communication link security in free-space laser communication links are discussed.

  8. Altered intrinsic regional spontaneous brain activity in patients with optic neuritis: a resting-state functional magnetic resonance imaging study

    PubMed Central

    Shao, Yi; Cai, Feng-Qin; Zhong, Yu-Lin; Huang, Xin; Zhang, Ying; Hu, Pei-Hong; Pei, Chong-Gang; Zhou, Fu-Qing; Zeng, Xian-Jun

    2015-01-01

    Objective To investigate the underlying regional homogeneity (ReHo) in brain-activity deficit in patients with optic neuritis (ON) and its relationship with behavioral performance. Materials and methods In total, twelve patients with ON (four males and eight females) and twelve (four males and eight females) age-, sex-, and education-matched healthy controls underwent resting-state functional magnetic resonance imaging scans. The ReHo method was used to assess the local features of spontaneous brain activity. Correlation analysis was used to explore the relationship between the observed mean ReHo values of the different brain areas and the visual evoked potential (VEP) in patients with ON. Results Compared with the healthy controls, patients with ON showed lower ReHo in the left cerebellum, posterior lobe, left middle temporal gyrus, right insula, right superior temporal gyrus, left middle frontal gyrus, bilateral anterior cingulate cortex, left superior frontal gyrus, right superior frontal gyrus, and right precentral gyrus, and higher ReHo in the cluster of the left fusiform gyrus and right inferior parietal lobule. Meanwhile, we found that the VEP amplitude of the right eye in patients with ON showed a positive correlation with the ReHo signal value of the left cerebellum posterior lobe (r=0.701, P=0.011), the right superior frontal gyrus (r=0.731, P=0.007), and the left fusiform gyrus (r=0.644, P=0.024). We also found that the VEP latency of the right eye in ON showed a positive correlation with the ReHo signal value of the right insula (r=0.595, P=0.041). Conclusion ON may involve dysfunction in the default-mode network, which may reflect the underlying pathologic mechanism. PMID:26715848

  9. Effect of macular edema on optical coherence tomography signal strength.

    PubMed

    Hosseini, Hamid; Razeghinejad, Mohammad Reza; Nowroozizadeh, Sarah; Jafari, Peyman; Ashraf, Hossein

    2010-01-01

    The purpose of this study was to examine the effect of macular edema (ME) on Stratus optical coherence tomography (OCT) (Stratus OCT, Carl Zeiss Meditec, Dublin, CA) signal strength (SS). Part 1: Macular OCT was performed in 57 eyes with ME, at 2 different time points with different degrees of ME. The relationships between SS change and change in center point thickness and total macular volume in two scans were examined. Part 2: In 54 eyes with ME, Stratus OCT examinations with macular thickness mapping and retinal nerve fiber layer analysis protocols were performed. The paired values of SS obtained with two scan protocols were compared. The relationship between SS difference between two test protocols with center point thickness and total macular volume was evaluated. Part 1: There was a significant correlation between SS change and the change in center point thickness and total macular volume in 2 consecutive scans. Part 2: Maximum SS obtained during macular OCT examination was significantly less than that obtained during retinal nerve fiber layer OCT. Significant correlations were observed between the difference in SS obtained in two scan protocols and center point thickness as well as total macular volume. Macular edema decreases macular OCT SS. In patients with ME, SS obtained during macular OCT examination was significantly lower than that obtained during retinal nerve fiber layer OCT examination.

  10. Propolis cinnamic acid derivatives induce apoptosis through both extrinsic and intrinsic apoptosis signaling pathways and modulate of miRNA expression.

    PubMed

    Kumazaki, Minami; Shinohara, Haruka; Taniguchi, Kohei; Yamada, Nami; Ohta, Shozo; Ichihara, Kenji; Akao, Yukihiro

    2014-01-01

    Propolis cinnamic acid derivatives have a number of biological activities including anti-oxidant and anti-cancer ones. In this study, we aimed to elucidate the mechanism of the anti-cancer activity of 3 representative propolis cinnamic acid derivatives, i.e., Artepilin C, Baccharin and Drupanin in human colon cancer cell lines. Our study demonstrated that these compounds had a potent apoptosis-inductive effect even on drug-resistant colon cancer cells. Combination treatment of human colon cancer DLD-1 cells with 2 of these compounds, each at its IC20 concentration, induced apoptosis by stimulating both intrinsic and extrinsic apoptosis signaling pathways. Especially, Baccharin plus Drupanin exhibited a synergistic growth-inhibitory effect by strengthening both intrinsic and extrinsic apoptotic signaling transduction through TRAIL/DR4/5 and/or FasL/Fas death-signaling loops and by increasing the expression level of miR-143, resulting in decreased expression levels of the target gene MAPK/Erk5 and its downstream target c-Myc. These data suggest that the supplemental intake of these compounds found in propolis has enormous significance with respect to cancer prevention.

  11. Studies of beam expansion and distributed Bragg reflector lasers for fiber optics and optical signal processing. Interim report

    SciTech Connect

    Garmire, E.M.

    1981-03-03

    Separate studies were performed on beam expansion and on Distributed Bragg Reflector (DBR) lasers preliminary to monolithic integration on GaAs substrates. These components are proposed for use in optical signal processing, for fiber optic sources and for high-brightness lasers.

  12. Acousto-Optic Interaction in Surface Acoustic Waves and Its Application to Real Time Signal Processing.

    DTIC Science & Technology

    1977-12-30

    ACOUSTO - OPTIC INTERACTION IN SURFACE ACOUSTIC WAVES AND ITS APP--ETC(U) DEC 77 0 SCHUMER, P DAS NOOOIJ -75-C-0772 NCLASSIFIED MA-ONR-30 Nt.EE E’h...CHART NAT*NAL BUREAU OF STANDARDS 1-63- ACOUSTO - OPTIC INTERACTION IN SURFACE ACOUSTIC WAVES AND ITS APPLICATION TO REAL TIME SIGNAL PROCESSING By 00 D... Acousto - optics , Integrated optics, Optical Signal Processing. 20. AbSKTRACT (Continue an reverse side it neceary and idewnt& by block mum ber) The

  13. Optical encryption/decryption of 8PSK signal using FWM-based modified XOR.

    PubMed

    Zhang, Min; Cui, Yue; Zhan, Yueying; Zhang, Zhiguo; Chen, Xue

    2015-09-01

    A scheme for optical encryption/decryption of an eight-phase-shift keying (8PSK) signal is proposed, and this scheme applies modified optical XOR gates based on four-wave mixing (FWM) in a semiconductor optical amplifier (SOA). Theoretical analyses and simulations are conducted. Both the performance and the parameter design of a 40-Gbit/s all-optical encryption/decryption system under various key parameters are studied. The results are useful for designing optical encryption/decryption for complex modulated signals.

  14. Classification of Acousto-Optic Correlation Signatures of Spread Spectrum Signals Using Artificial Neural Networks

    DTIC Science & Technology

    1989-12-01

    Ohio ’aPw iorlipuab muo i 0I2, AFIT/GE/ENG/89D-10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION SIGNATURES OF SPREAD SPECTRUM SIGNALS USING ARTIFICIAL...ENG/89D- 10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION SIGNATURES OF SPREAD SPECTRUM SIGNALS USING ARTIFICIAL NEURAL NETWORKS THESIS John W. DeBerry...Captain, USAF AFIT/GE/ENG/89D- 10 Approved for public release; distribution unlimited. AFIT/GE/ENG/89D-10 CLASSIFICATION OF ACOUSTO - OPTIC CORRELATION

  15. 2-D Acousto-Optic Signal Processors for Simultaneous Spectrum Analysis and Direction Finding

    DTIC Science & Technology

    1990-11-01

    National Dfense Defence nationale 2-D ACOUSTO - OPTIC SIGNAL PROCESSORS FOR SIMULTANEOUS SPECTRUM ANALYSIS 00 AND DIRECTION FINDING (U) by NM Jim P.Y...Wr pdft .1w I0~1111191 3 05089 National DIfense Defence nationale 2-D ACOUSTO - OPTIC SIGNAL PROCESSORS FOR SIMULTANEOUS SPECTRUM ANALYSIS AND DIRECTION...Processing, J.T. Tippet et al., Eds., Chapter 38, pp. 715-748, MIT Press, Cambridge 1965. [6] A.E. Spezio," Acousto - optics for Electronic Warfare

  16. Propagation of 2.5 Gb/s Asynchronous, Concurrent, Optical CDMA Signals Through a 214 Kilometer Fiber Optic Link

    SciTech Connect

    Mendez, A.J.; Feng, H.X.C.; Heritage, J.P.; Morookian, J.; Gagliardi, R.M.

    2000-03-16

    The propagation of optical Code Division Multiple Access (CDMA) signals was studied by computer simulation. Group velocity dispersion produces the worst impairment. With dispersion management, the decoder successfully recovers the signals, even in the presence of severe multi-access interference.

  17. Harnessing mode-selective nonlinear optics for on-chip multi-channel all-optical signal processing

    NASA Astrophysics Data System (ADS)

    Ma, Ming; Chen, Lawrence R.

    2016-11-01

    All-optical signal processing based on nonlinear optical effects allows for the realization of important functions in telecommunications including wavelength conversion, optical multiplexing/demultiplexing, Fourier transformation, and regeneration, amongst others, on ultrafast time scales to support high data rate transmission. In integrated photonic subsystems, the majority of all-optical signal processing systems demonstrated to date typically process only a single channel at a time or perform a single processing function, which imposes a serious limitation on the functionality of integrated solutions. Here, we demonstrate how nonlinear optical effects can be harnessed in a mode-selective manner to perform simultaneous multi-channel (two) and multi-functional optical signal processing (i.e., regenerative wavelength conversion) in an integrated silicon photonic device. This approach, which can be scaled to a higher number of channels, opens up a new degree of freedom for performing a broad range of multi-channel nonlinear optical signal processing functions using a single integrated photonic device.

  18. Optical sampling of ultrahigh bitrate signals using highly nonlinear chalcogenide planar waveguides or tapered fibers

    NASA Astrophysics Data System (ADS)

    Van Erps, Jürgen; Luan, Feng; Pelusi, Mark D.; Mägi, Eric; Iredale, Tim; Madden, Steve; Choi, Duk Yong; Bulla, Douglas A.; Luther-Davies, Barry; Thienpont, Hugo; Eggleton, Benjamin J.

    2010-06-01

    As the bit rates of optical networks increase, the ability of accurate monitoring of optical waveforms has become increasingly important. In recent years, optical sampling has emerged as a technique to perform time-resolved measurements of optical data signals at high data rates with a bandwidth that cannot be reached by conventional photodetectors and oscilloscopes. In an optical sampling system, the optical signal is sampled in the optical domain by a nonlinear optical sampling gate before the resulting samples are converted to an electrical signal. This avoids the need for high bandwidth electronics if the optical sampling gate is operated with a modest repetition frequency. In this paper, we present an optical sampling system using the optical Kerr effect in a highly nonlinear chalcogenide device, enabling combined capability for femtosecond resolution and broadband signal wavelength tunability. A temporal resolution 450-fs is achieved using four-wave mixing (FWM) in dispersion-engineered chalcogenide waveguides: on one hand a 7-cm long planar waveguide (integrated on a photonic chip) and on the other hand a 5-cm long tapered fiber. The use of a short length, dispersion-shifted waveguide with ultrahigh nonlinearity (10000/W/km) enables high-resolution optical sampling without the detrimental effect of chromatic dispersion on the temporal distortion of the signal and sampling pulses, as well as their phase mismatch (which in turn would degrade the FWM efficiency and the sensitivity of the measurement). Using these chalcogenide devices, we successfully monitor a 640-Gb/s optical time-division multiplexing (OTDM) datastream, showcasing its potential for monitoring of signals at bitrates approaching and beyond Tb/s. We compare the advantages and disadvantages of both approaches and discuss fundamental limitations as well as potential improvements.

  19. Silver-Overgrowth-Induced Changes in Intrinsic Optical Properties of Gold Nanorods: From Noninvasive Monitoring of Growth Kinetics to Tailoring Internal Mirror Charges.

    PubMed

    Tebbe, Moritz; Kuttner, Christian; Mayer, Martin; Maennel, Max; Pazos-Perez, Nicolas; König, Tobias A F; Fery, Andreas

    2015-04-30

    We investigate the effect of surfactant-mediated, asymmetric silver overgrowth of gold nanorods on their intrinsic optical properties. From concentration-dependent experiments, we established a close correlation of the extinction in the UV/vis/NIR frequency range and the morphological transition from gold nanorods to Au@Ag cuboids. Based on this correlation, a generic methodology for in situ monitoring of the evolution of the cuboid morphology was developed and applied in time-dependent experiments. We find that growth rates are sensitive to the substitution of the surfactant headgroup by comparison of benzylhexadecyldimethylammonium chloride (BDAC) with hexadecyltrimethylammonium chloride (CTAC). The time-dependent overgrowth in BDAC proceeds about 1 order of magnitude slower than in CTAC, which allows for higher control during silver overgrowth. Furthermore, silver overgrowth results in a qualitatively novel optical feature: Upon excitation inside the overlap region of the interband transition of gold and intraband of silver, the gold core acts as a retarding element. The much higher damping of the gold core compared to the silver shell in Au@Ag cuboids induces mirror charges at the core/shell interface as shown by electromagnetic simulations. Full control over the kinetic growth process consequently allows for precise tailoring of the resonance wavelengths of both modes. Tailored and asymmetric silver-overgrown gold nanorods are of particular interest for large-scale fabrication of nanoparticles with intrinsic metamaterial properties. These building blocks could furthermore find application in optical sensor technology, light harvesting, and information technology.

  20. Silver-Overgrowth-Induced Changes in Intrinsic Optical Properties of Gold Nanorods: From Noninvasive Monitoring of Growth Kinetics to Tailoring Internal Mirror Charges

    PubMed Central

    2015-01-01

    We investigate the effect of surfactant-mediated, asymmetric silver overgrowth of gold nanorods on their intrinsic optical properties. From concentration-dependent experiments, we established a close correlation of the extinction in the UV/vis/NIR frequency range and the morphological transition from gold nanorods to Au@Ag cuboids. Based on this correlation, a generic methodology for in situ monitoring of the evolution of the cuboid morphology was developed and applied in time-dependent experiments. We find that growth rates are sensitive to the substitution of the surfactant headgroup by comparison of benzylhexadecyldimethylammonium chloride (BDAC) with hexadecyltrimethylammonium chloride (CTAC). The time-dependent overgrowth in BDAC proceeds about 1 order of magnitude slower than in CTAC, which allows for higher control during silver overgrowth. Furthermore, silver overgrowth results in a qualitatively novel optical feature: Upon excitation inside the overlap region of the interband transition of gold and intraband of silver, the gold core acts as a retarding element. The much higher damping of the gold core compared to the silver shell in Au@Ag cuboids induces mirror charges at the core/shell interface as shown by electromagnetic simulations. Full control over the kinetic growth process consequently allows for precise tailoring of the resonance wavelengths of both modes. Tailored and asymmetric silver-overgrown gold nanorods are of particular interest for large-scale fabrication of nanoparticles with intrinsic metamaterial properties. These building blocks could furthermore find application in optical sensor technology, light harvesting, and information technology. PMID:26113885

  1. Real-time digital signal processing for live electro-optic imaging.

    PubMed

    Sasagawa, Kiyotaka; Kanno, Atsushi; Tsuchiya, Masahiro

    2009-08-31

    We present an imaging system that enables real-time magnitude and phase detection of modulated signals and its application to a Live Electro-optic Imaging (LEI) system, which realizes instantaneous visualization of RF electric fields. The real-time acquisition of magnitude and phase images of a modulated optical signal at 5 kHz is demonstrated by imaging with a Si-based high-speed CMOS image sensor and real-time signal processing with a digital signal processor. In the LEI system, RF electric fields are probed with light via an electro-optic crystal plate and downconverted to an intermediate frequency by parallel optical heterodyning, which can be detected with the image sensor. The artifacts caused by the optics and the image sensor characteristics are corrected by image processing. As examples, we demonstrate real-time visualization of electric fields from RF circuits.

  2. High-Speed Characterizatin of Optical Telecommunication Signals

    SciTech Connect

    Dorrer, C.

    2007-05-17

    Optical telecommunication systems constantly evolve toward higher bit rates, requiring the modulation and detection of higher-bandwidth optical waves. Commercial systems operating at 40 Gb/s are now available and research and development efforts are targeting higher bit rates for which optical pulses with picosecond-range duration are used. Chromatic dispersion, nonlinearities and amplified spontaneous emission from optical amplifiers are sources of transmission impairments that must be characterized and mitigated. Advanced modulation formats rely on the modulation of not only the amplitude of an optical wave (e.g., on/off keying), but also its phase (e.g., phase-shift keying) in order to optimize the transmission capabilities. The importance of the characterization of the properties of optical sources and components and the specificities of the optical telecommunication environment with respect to ultrafast optics are emphasized. Various diagnostics measuring the electric field of optical sources in the telecommunication environment are described. Sampling diagnostics capable of measuring eye diagrams and constellation diagrams of high-bit-rate, data-encoded sources are presented. Various optical pulse characterization techniques that meet the sensitivity requirements imposed by the telecommunication environment are also described.

  3. Intrinsic Properties of immunoglobulin IgG1 Isotype-Switched B Cell Receptors Promote Microclustering and the Initiation of Signaling

    PubMed Central

    Liu, Wanli; Meckel, Tobias; Tolar, Pavel; Sohn, Hae Won; Pierce, Susan K.

    2010-01-01

    Summary Memory B cells express high affinity, immunoglobulin B cell receptors (IgG-BCRs) that enhance B cell responses giving rise to the rapid production of high affinity, IgG antibodies. Despite the central role of IgG-BCRs in memory responses, the mechanisms by which the IgG-BCRs function to enhance B cell responses are not fully understood. Using high-resolution live-cell imaging we showed that independent of affinity, IgG1-BCRs dramatically enhanced the earliest BCR-intrinsic events that followed within seconds of B cells’ encounter with membrane bound antigen including BCR oligomerization and BCR microcluster growth, leading to Syk kinase recruitment and calcium responses. The enhancement of these early events was dependent on a membrane proximal region of the IgG1 cytoplasmic tail not previously appreciated to play a role in IgG1-BCR signaling. Thus, intrinsic properties of the IgG1-BCR enhance early antigen-driven events that ultimately translate into heightened signaling. PMID:20620943

  4. Signal-to-Noise Ratio Enhancement Based on Empirical Mode Decomposition in Phase-Sensitive Optical Time Domain Reflectometry Systems.

    PubMed

    Qin, Zengguang; Chen, Hui; Chang, Jun

    2017-08-14

    We propose a novel denoising method based on empirical mode decomposition (EMD) to improve the signal-to-noise ratio (SNR) for vibration sensing in phase-sensitive optical time domain reflectometry (φ-OTDR) systems. Raw Rayleigh backscattering traces are decomposed into a series of intrinsic mode functions (IMFs) and a residual component using an EMD algorithm. High frequency noise is eliminated by removing several IMFs at the position without vibration selected by the Pearson correlation coefficient (PCC). When the pulse width is 50 ns, the SNR of location information for the vibration events of 100 Hz and 1.2 kHz is increased to as high as 42.52 dB and 39.58 dB, respectively, with a 2 km sensing fiber, which demonstrates the excellent performance of this new method.

  5. Effect on measurement accuracy of transillumination using sawtooth-shaped-function optical signal

    NASA Astrophysics Data System (ADS)

    Yang, Xue; Hu, Yajia; Li, Gang; Lin, Ling

    2016-11-01

    There exist lots of difficulties in optical transillumination of biological tissues, especially, low-level-light detection and low gray-scale resolution could reduce recognition accuracy of differences in tissue. Aiming at the problems, this paper proposes a method for optical transillumination using sawtooth-shaped-function optical signal and frame accumulation technology to explore the spatial information of heterogeneity in the tissue. Sawtooth-shaped-function optical signal combined with frame accumulation technology is applied to realize the low-level-light image detection, where frame accumulation technology improves the signal-to-noise ratio and detection sensitivity, and sawtooth-shaped-function signal improves gray-scale resolution. The results of the experiment applied on the flat-shaped phantom demonstrated that, compared with the constant intensity optical signal, the application of the sawtooth-shaped-function optical signal effectively improved the gray-scale resolution, thus improved the extraction accuracy on positional feature pixels of heterogeneity. In addition, the sawtooth-shaped-function optical signal reduces the light radiation per unit time and per unit area. Therefore, the proposed illuminated way is more suitable for the imaging of biological tissue.

  6. Using the optical-klystron effect to increase and measure the intrinsic beam energy spread in free-electron-laser facilities

    NASA Astrophysics Data System (ADS)

    Prat, Eduard; Ferrari, Eugenio; Reiche, Sven; Schietinger, Thomas

    2017-04-01

    We present a setup based on the optical klystron concept, consisting of two undulator modules separated by a magnetic chicane, that addresses two issues in free-electron-laser (FEL) facilities. On the one hand, it allows increasing the intrinsic energy spread of the beam at the source, which is useful to counteract the harmful microbunching instability. This represents an alternative method to the more conventional laser heater with the main advantage that no laser system is required. On the other hand, the setup can be used to reconstruct the initial beam energy spread, whose typical values in FEL injectors around 1 keV are very difficult to measure with standard procedures.

  7. Simulation of the coherent MDM transmission using principal modes of the optical fiber as signal carriers

    NASA Astrophysics Data System (ADS)

    Lyubopytov, Vladimir S.; Zakirov, Robert A.; Vinogradova, Irina L.; Sultanov, Albert K.

    2015-03-01

    In this paper we demonstrate computer simulation results obtained for the coherent mode division multiplexed (MDM) 5x5 QPSK transmission using principal modes (PMs) of the stepped-index few-mode fiber (FMF) as a basis of independent signal carriers. The output signal recovering and the fiber propagation matrix determination are considered to be carried out in optical domain by means of reconfigurable multibranch diffractive optical elements (DOEs). Both the cases of Gaussian and Nyquist raised-cosine pulse shaping are considered for optical signal modulation. The simulation results show, that the transmission in the basis of PMs in strong coupling regime allows the reliability of the coherent MDM system to be fundamentally improved. As a result, utilization of the optical signal processing for MDM transmission could minimize substantially the DSP circuit complexity required for the real-time recovering of the transmitted signal.

  8. Direct-detection optical communication with color coded pulse position modulation signaling

    NASA Technical Reports Server (NTRS)

    Davidson, F.

    1985-01-01

    The performance characteristics of a direct-detection optical communication system which is based on a laser transmitter which produces single light pulses at selected nonoverlapping optical center frequencies are discussed. The signal format, called color coded pulse position modulation (CCPPM), uses more of the total available response bandwidth characteristics of the photodetector than does ordinary PPM signaling. The advantages of CCPPM signaling are obtained at the expense of an increased optical bandwidth of the transmitted signal and a more complicated transmitter and receiver structure. When the signal format is used in conjunction with block length Reed-Solomon codes, high data rates and reliable high-speed optical communications under conditions of optimal energy efficiency are obtained.

  9. Direct-detection optical communication with color coded pulse position modulation signaling

    NASA Technical Reports Server (NTRS)

    Davidson, F.

    1985-01-01

    The performance characteristics of a direct-detection optical communication system which is based on a laser transmitter which produces single light pulses at selected nonoverlapping optical center frequencies are discussed. The signal format, called color coded pulse position modulation (CCPPM), uses more of the total available response bandwidth characteristics of the photodetector than does ordinary PPM signaling. The advantages of CCPPM signaling are obtained at the expense of an increased optical bandwidth of the transmitted signal and a more complicated transmitter and receiver structure. When the signal format is used in conjunction with block length Reed-Solomon codes, high data rates and reliable high-speed optical communications under conditions of optimal energy efficiency are obtained.

  10. A Multi-Functional Planar Lightwave Circuit for Optical Signal Processing Applications

    NASA Astrophysics Data System (ADS)

    Samadi, Payman

    Ultrafast optical signal processing is now a necessary tool in several domains of science and technology such as high-speed telecommunication, biomedicine, microscopy and radar systems. Optical arbitrary waveform generation is an optical signal processing function which has applications in optical telecommunication networks, sampling, and photonically-assisted RF waveform generation. Furthermore, performing optical signal processing in photonic integrated circuits is crucial for system integration and overcoming the speed limitations in electrical to optical conversion. In this thesis, we introduce a silica-based planar lightwave circuit which performs several optical signal processing functions. We start by reviewing the material system used to fabricate the device. We justify the choice of the material for our application and explain the fabrication process and the experiments to characterize the device. Then we introduce the fundamental theory of our device which is based on pulse repetition rate multiplication (PRRM) and shaping. We review the theory of direct time-domain approach to perform the PRRM and shaping. Experiments to measure the impulse response of the device, perform PRRM and polarization dependence characterization is shown as well. Three main applications of our device is presented next. First we use the PLC device with non-linear optics to generate multiple pulse trains at different wavelengths and different repetition rates. Second, we use the fundamental of the previous application to perform demultiplexing of optical time division multiplexed signals. Our approach is flexible in a sense that it can demultiplex any tributary channel of lower rate data, also it works for both amplitude and phase modulated data. Finally, using the second generation of our PLC device, we photonically generate radio frequency waveforms. We are able to generate various pulse shapes which are generally hard to generate using electronics at frequencies up to 80 GHz

  11. High-Voltage Current Transformers With Optical Signal Transmission

    NASA Astrophysics Data System (ADS)

    Malewski, Ryszard

    1981-02-01

    Existing prototype optical current transformers are reviewed and their design as well as their functional characteristics are analyzed in the light of the practical requirements dictated by operating conditions in an extra-high-voltage (EHV) switchyard. A perspective of the development of a new magneto-optic current transformer is explored. The feasibility of such apparatus depends on technological progress in manufacturing mono-mode optical fibers which will not depolarize the transmitted light.

  12. Quality Monitoring of Infrared Optics Using Ultrasound Signals

    NASA Astrophysics Data System (ADS)

    Neumeier, Benedikt; Schmitt-Landsiedel, Doris

    During laser processing with beam powers in the multi-kilowatt range a fraction of the emission is absorbed in optical elements, leading to thermal loading on the optics. This temperature rise of the optics results in thermal lensing, impairing the power density at the processing location. In a number of niche applications, the CO2 laser still is preferred over solid-state lasers due to its unrivaled features in processing materials like fused silica, glasses, wood, ceramics or plastics. Applying existing techniques to monitor the temperature of CO2 laser optics using pyrometers prove to be unreliable due to the transmissivity in the infrared of the optical materials used. The object of this study is experimental identification of temperature increase of ZnSe optics during use for processing in a laser cutting machine, and development of a method utilizing ultrasound to measure the temperature of the infrared optics. The method enables the testing of the absorption properties of infrared optics as well as solid-state laser optics.

  13. Power-efficient method for IM-DD optical transmission of multiple OFDM signals.

    PubMed

    Effenberger, Frank; Liu, Xiang

    2015-05-18

    We propose a power-efficient method for transmitting multiple frequency-division multiplexed (FDM) orthogonal frequency-division multiplexing (OFDM) signals in intensity-modulation direct-detection (IM-DD) optical systems. This method is based on quadratic soft clipping in combination with odd-only channel mapping. We show, both analytically and experimentally, that the proposed approach is capable of improving the power efficiency by about 3 dB as compared to conventional FDM OFDM signals under practical bias conditions, making it a viable solution in applications such as optical fiber-wireless integrated systems where both IM-DD optical transmission and OFDM signaling are important.

  14. Simple all-optical FFT scheme enabling Tbit/s real-time signal processing.

    PubMed

    Hillerkuss, D; Winter, M; Teschke, M; Marculescu, A; Li, J; Sigurdsson, G; Worms, K; Ben Ezra, S; Narkiss, N; Freude, W; Leuthold, J

    2010-04-26

    A practical scheme to perform the fast Fourier transform in the optical domain is introduced. Optical real-time FFT signal processing is performed at speeds far beyond the limits of electronic digital processing, and with negligible energy consumption. To illustrate the power of the method we demonstrate an optical 400 Gbit/s OFDM receiver. It performs an optical real-time FFT on the consolidated OFDM data stream, thereby demultiplexing the signal into lower bit rate subcarrier tributaries, which can then be processed electronically.

  15. Chromatic dispersion and polarization mode dispersion insensitive optical signal to noise ratio monitoring based on electronic variable optical attenuators and optical bandpass filter

    NASA Astrophysics Data System (ADS)

    Chang, Junde; Liu, Bo; Zhang, Lijia; Xin, Xiangjun; Zhang, Qi; Tian, Qinghua; Tian, Feng; Yin, Xiaoli; Rao, Lan; Wang, Yongjun

    2016-10-01

    In this paper, an optical signal to noise ratio (OSNR) monitoring method based on radio frequency (RF) power of two signals in parallel connection. The test optical signal was split equally into two signals in parallel connection. One removed out-of-band noise by optical bandpass filter, the other kept output power constant by electronic variable optical attenuators (EVOA) with power-locking control loop. One radio frequency power of the two signals treated by different ways increased with the increase of OSNR when the two signals are at the same place. The other decreased. The difference of radio frequency power of the two signals at the same place was used to monitor OSNR. The simulation results showed that the proposed technique can implement OSNR monitoring between 2dB and 30dB for 40Gb/s NRZDQPSK optical signal. Monitoring error was within 1.5dB and the proposed technique was insensitive to chromatic dispersion (CD) and polarization mode dispersion (PMD).

  16. Signal Coherence Recovery Using Acousto-Optic Fourier Transform Architectures

    DTIC Science & Technology

    1990-06-14

    processing of data in ground- and space-based applications. We have implemented a prototype one-dimensional time-integrating acousto - optic (AO) Fourier...theory of optimum coherence recovery (CR) applicable in computation-limited environments. We have demonstrated direct acousto - optic implementation of CR

  17. Enhanced optical spin current injection in the hexagonal lattice with intrinsic and Rashba spin-orbit interactions

    NASA Astrophysics Data System (ADS)

    Zou, Jianfei; Tang, Chunmei; Zhang, Aimei

    2017-04-01

    We study the photo-induced spin current injection in a hexagonal lattice with both intrinsic and Rashba spin-orbit interactions which is irradiated by a polarized light beam. It is found that the spin current injection rate could be enhanced as the graphene lattice is in the topological insulator state. Furthermore, the spin current injection rate could be remarkably modulated by the degree of polarization of light and its frequency.

  18. Removal Of Surface Deposits And Intrinsic Stains Of Teeth With Fiber Optics Of Nd-YAG Laser

    NASA Astrophysics Data System (ADS)

    Marioka, Toshio; Maseda, Yusaku; Oho, Takahiko

    1987-03-01

    An impact of the Q-switched Nd-YAG laser caused bleaching of stains and removal of deposits and pit & fissure contents of teeth. No chalky spots or craters were found microscopically on the enamel surface after irradiation. These results strongly suggested the clinical applicability of Q-switched Nd-YAG laser in removing dental deposits, intrinsic pigmentation of enamel, and pit and fissure contents of molar.

  19. The MUSCLES Treasury Survey: Intrinsic Lyα Profile Reconstructions and UV, X-ray, and Optical Correlations of Low-mass Exoplanet Host Stars

    NASA Astrophysics Data System (ADS)

    Youngblood, Allison; France, Kevin; Parke Loyd, R. O.

    2016-01-01

    UV stellar radiation can significantly impact planetary atmospheres through heating and photochemistry, even regulating production of potential biomarkers. Cool stars emit the majority of their UV radiation in the form of emission lines, and the incident UV radiation on close-in habitable-zone planets is significant. Lyα (1215.67 Å) dominates the 912 - 3200 Å spectrum of cool stars, but strong absorption from the interstellar medium (ISM) makes direct observations of the intrinsic Lyα emission of even nearby stars challenging. The MUSCLES Hubble Space Telescope Treasury Survey (Measurements of the Ultraviolet Spectral Characteristics of Low-mass Exoplanetary Systems) has completed observations of 7 M and 4 K stars hosting exoplanets (d < 22 pc) with simultaneous X-ray and ground-based optical spectroscopy for many of the targets. We have reconstructed the intrinsic Lyα profiles using an MCMC technique and used the results to estimate the extreme ultraviolet (100 - 911 Å) spectrum. We also present empirical relations between chromospheric UV and optical lines, e.g., Lyα, Mg II, Ca II H & K, and Hα, for use when direct UV observations of low-mass exoplanet host stars are not possible. The spectra presented here will be made publicly available through MAST to support exoplanet atmosphere modeling.

  20. Influence of intrinsic signals and environmental cues on the endocrine control of feeding in fish: potential application in aquaculture.

    PubMed

    Volkoff, Hélène; Hoskins, Leah J; Tuziak, Sarah M

    2010-07-01

    Optimization of food consumption and ultimately growth are major concerns for aquaculture. In fish, food intake is regulated by several hormones produced by both brain and peripheral tissues. Changes in feeding behavior and appetite usually occur through the modulation of the gene expression and/or action of these appetite-regulating hormones and can be due not only to variations in intrinsic factors such as nutritional/metabolic or reproductive status, but also to changes in environmental factors, such as temperature and photoperiod. In addition, the gene expression and/or plasma levels of appetite-regulating hormones might also display daily as well as circannual (seasonal) rhythms. Despite recent advances, our current understanding of the regulation of feeding in fish is still limited. We give here a brief overview of our current knowledge of the endocrine regulation of feeding in fish and describe how a better understanding of appetite-related hormones in fish might lead to the development of sustainable aquaculture.

  1. Noise reduction and signal-to-noise ratio improvement of atomic magnetometers with optical gradiometer configurations.

    PubMed

    Kamada, Keigo; Ito, Yosuke; Ichihara, Sunao; Mizutani, Natsuhiko; Kobayashi, Tetsuo

    2015-03-09

    In the field of biomagnetic measurement, optically-pumped atomic magnetometers (OPAMs) have attracted significant attention. With the improvement of signal response and the reduction of sensor noise, the sensitivity of OPAMs is limited mainly by environmental magnetic noise. To reduce this magnetic noise, we developed the optical gradiometer, in which the differential output of two distinct measurement areas inside a glass cell was obtained directly via the magneto-optical rotation of one probe beam. When operating in appropriate conditions, the sensitivity was improved by the differential measurement of the optical gradiometer. In addition, measurements of the pseudo-magnetic noise and signal showed the improvement of the signal-to-noise ratio. These results demonstrate the feasibility of our optical gradiometer as an efficient method for reducing the magnetic noise.

  2. Photonic integrated circuit for all-optical millimeter-wave signal generation

    SciTech Connect

    Vawter, G.A.; Mar, A.; Zolper, J.; Hietala, V.

    1997-03-01

    Generation of millimeter-wave electronic signals and power is required for high-frequency communication links, RADAR, remote sensing and other applications. However, in the 30 to 300 GHz mm-wave regime, signal sources are bulky and inefficient. All-optical generation of mm-wave signals promises to improve efficiency to as much as 30 to 50 percent with output power as high as 100 mW. All of this may be achieved while taking advantage of the benefits of monolithic integration to reduce the overall size to that of a single semiconductor chip only a fraction of a square centimeter in size. This report summarizes the development of the first monolithically integrated all-optical mm-wave signal generator ever built. The design integrates a mode-locked semiconductor ring diode laser with an optical amplifier and high-speed photodetector into a single optical integrated circuit. Frequency generation is demonstrated at 30, 60 and 90 Ghz.

  3. Optical radio-photonic channel for transmission of a coherent narrowband analog signal

    NASA Astrophysics Data System (ADS)

    Zhuk, D. I.; Denisyuk, I. Yu.; Fokina, M. I.

    2015-10-01

    The channel of an optical transmission line of coherent narrowband analog signal consisting of a continuous-wave laser, an electro-optic modulator, and a vector phase rotator based on electrically controlled fiber-optical 1 × 2 splitter and fixed delay lines is analyzed. The scheme is constructed from commercially available components used in digital optical communication systems. The applicability of components for analog and small-signal circuits is determined. Variation of radio signal phase in the range from 0° to 170° for radio signal frequencies between 1 and 2 GHz is demonstrated experimentally. It is shown that phase variation is a linear function of frequency in this range.

  4. System and method for ultrafast optical signal detecting via a synchronously coupled anamorphic light pulse encoded laterally

    DOEpatents

    Heebner, John E [Livermore, CA

    2010-08-03

    In one general embodiment, a method for ultrafast optical signal detecting is provided. In operation, a first optical input signal is propagated through a first wave guiding layer of a waveguide. Additionally, a second optical input signal is propagated through a second wave guiding layer of the waveguide. Furthermore, an optical control signal is applied to a top of the waveguide, the optical control signal being oriented diagonally relative to the top of the waveguide such that the application is used to influence at least a portion of the first optical input signal propagating through the first wave guiding layer of the waveguide. In addition, the first and the second optical input signals output from the waveguide are combined. Further, the combined optical signals output from the waveguide are detected. In another general embodiment, a system for ultrafast optical signal recording is provided comprising a waveguide including a plurality of wave guiding layers, an optical control source positioned to propagate an optical control signal towards the waveguide in a diagonal orientation relative to a top of the waveguide, at least one optical input source positioned to input an optical input signal into at least a first and a second wave guiding layer of the waveguide, and a detector for detecting at least one interference pattern output from the waveguide, where at least one of the interference patterns results from a combination of the optical input signals input into the first and the second wave guiding layer. Furthermore, propagation of the optical control signal is used to influence at least a portion of the optical input signal propagating through the first wave guiding layer of the waveguide.

  5. Applying of digital signal processing to optical equisignal zone system

    NASA Astrophysics Data System (ADS)

    Maraev, Anton A.; Timofeev, Aleksandr N.; Gusarov, Vadim F.

    2015-05-01

    In this work we are trying to assess the application of array detectors and digital information processing to the system with the optical equisignal zone as a new method of evaluating of optical equisignal zone position. Peculiarities of optical equisignal zone formation are described. The algorithm of evaluation of optical equisignal zone position is applied to processing on the array detector. This algorithm enables to evaluate as lateral displacement as turning angles of the receiver relative to the projector. Interrelation of parameters of the projector and the receiver is considered. According to described principles an experimental set was made and then characterized. The accuracy of position evaluation of the equisignal zone is shown dependent of the size of the equivalent entrance pupil at processing.

  6. Micro-Structured Materials for Generation of Coherent Light and Optical Signal Processing

    DTIC Science & Technology

    2008-12-22

    within a laser linewidth of 1 GHz (matched to the doppler broadened bandwidth of the sodium layer) to provide enough return light to the wavefront...AND SUBTITLE Micro-Structured Materials for Generation of Coherent Light And Optical Signal Processing 5a. CONTRACT NUMBER 5b. GRANT NUMBER...2008 3. TITLE OF PROPOSAL: Micro-Structured Matenals for Generation of Coherent Light And Optical Signal Processing 4. LIST OF MANUSCRIPTS

  7. Meiotic failure in cyclin A1-deficient mouse spermatocytes triggers apoptosis through intrinsic and extrinsic signaling pathways and 14-3-3 proteins

    PubMed Central

    Panigrahi, Sunil K.; Manterola, Marcia; Wolgemuth, Debra J.

    2017-01-01

    Cyclin A1 (Ccna1), a member of the mammalian A type cyclins, is most abundantly expressed in spermatocytes and is essential for spermatogenesis in the mouse. Ccna1- deficient spermatocytes arrest at late meiotic prophase and undergo apoptosis. To further delineate the mechanisms and key factors involved in this process, we have examined changes in expression of genes involved in both intrinsic and extrinsic signaling pathways that trigger apoptosis in the mutant spermatocytes. Our results show that both pathways are involved, and that the factors involved in the intrinsic pathway were expressed earlier than those involved in the extrinsic pathway. We have also begun to identify in vivo Ccna1-interacting proteins, using an unbiased biochemical approach, and identified 14-3-3, a key regulator of apoptosis, as a Ccna1-interacting protein. Expression levels of 14-3-3 proteins remain unchanged between wild type and mutant testes but there were differences in the subcellular distribution. In wild type control, 14-3-3 is detected in both cytosolic and nuclear fractions whereas it is restricted to the cytoplasm in mutant testes. This differential distribution of 14-3-3 may contribute to the induction of apoptosis in Ccna1-deficient spermatocytes. These results provide insight into the apoptotic mechanisms and pathways that are triggered when progression through the meiotic cell cycle is defective in male gametogenesis. PMID:28301569

  8. Thermally tuneable optical modulator adapted for differential signaling

    DOEpatents

    Zortman, William A.

    2016-01-12

    An apparatus for optical modulation is provided. The apparatus includes a modulator structure and a heater structure. The modulator structure comprises a ring or disk optical resonator having a closed curvilinear periphery and a pair of oppositely doped semiconductor regions within and/or adjacent to the optical resonator and conformed to modify the optical length of the optical resonator upon application of a bias voltage. The heater structure comprises a relatively resistive annulus of semiconductor material enclosed between an inner disk and an outer annulus of relatively conductive semiconductor material. The inner disk and the outer annulus are adapted as contact regions for a heater activation current. The heater structure is situated within the periphery of the optical resonator such that in operation, at least a portion of the resonator is heated by radial conductive heat flow from the heater structure. The apparatus further includes a substantially annular isolation region of dielectric or relatively resistive semiconductor material interposed between the heater structure and the modulator structure. The isolation region is effective to electrically isolate the bias voltage from the heater activation current.

  9. Fasudil alleviates traumatic optic neuropathy by inhibiting Rho signaling pathway

    PubMed Central

    Yu, Jianglong; Lan, Shiying; Wang, Ruijia; Maier, Aba; Luan, Xinping

    2015-01-01

    Objectives: The present study is to investigate the pathological changes in rabbits with traumatic optic neuropathy (TON), as well as the effect of fasudil on the lesions. Methods: A total of 144 New Zealand rabbits were successfully established as TON models. Twelve hours after surgery, the rabbits in control, dexamethasone, and fasudil groups were administrated with saline, dexamethasone, and fasudil via ear veins, respectively. Then, retinas of the rabbits were obtained at 72 h and on days 7, 14 and 21 after surgery. The pathological changes in retina and optic nerves were observed by hematoxylin and eosin staining and transmission electron microscopy. The expression levels of Rho-associated genes were measured using quantitative real-time polymerase chain reaction. Results: In control group, the axons were swelling, and mitochondria showed vacuolation after optic nerve crush. Mitochondria were swelled slightly in dexamethasone group. By contrast, nerves in fasudil group were repaired. Retinal ganglion cells in control group were reduced significantly due to optic nerve crush. The loss of retinal ganglion cells was alleviated in fasudil group. Quantitative real-time polymerase chain reaction showed that the expression of Rho-associated genes were down-regulated. Conclusions: The present study demonstrates that fasudil inhibits the apoptosis of retinal ganglion cells and ameliorates damages of optic nerves in traumatic optic neuropathy. PMID:26550269

  10. Experimental study of the use of multiband acousto-optic filters for spectral encoding / decoding the optical signals

    NASA Astrophysics Data System (ADS)

    Proklov, V. V.; Byshevski-Konopko, O. A.; Filatov, A. L.; Lugovskoi, A. V.; Pisarevsky, Yu V.

    2016-08-01

    A prototype of the acousto-optic (AO) decoder of optical signals is created on the base of the multiband AO filter. The joint work of the decoder with the developed previously AO coder has been verified experimentally. The main qualitative and quantitate characteristics of the spectral coding and decoding by Walsh sequences of the industrial LED radiation in the near infrared range are investigated. It is shown, that in the proposed data transmission system realization Signal-to-Interference Ratio (SIR) is not less than 13 dB.

  11. Signal Propagation Characteristics in Polyimide Optical Wave-guide with Micro-Mirrors for Optical Multichip Module

    NASA Astrophysics Data System (ADS)

    Kuwana, Yasuhiro; Hirose, Akinori; Kurino, Hiroyuki; Koyanagi, Mitsumasa

    1999-04-01

    In order to develop key technologies for a multichip module with optical interconnection, a test module using polyimide opticalwaveguides (POWs) with micro-mirrors and a photodiode array wassuccessfully fabricated.Through the fabrication of this test module, we developed such basic technologies as POW formation, vertical optical coupling withmicro-mirrors buried in POWs, chip bonding with copper bumps, and so on.The signal propagation in POWs was characterized by the detection of vertical output signals at micro-mirrors. From these characteristics,the transmission loss caused by passing a mirror was evaluated to be 0.16 dB.

  12. Applications of signal multiplexing in fiber optic-based acoustic and seismic sensors

    NASA Astrophysics Data System (ADS)

    Costley, R. D.; Folks, William R.; Kirkendall, Clay K.; Galan-Comas, Gustavo; Smith, Eric W.; Parker, Michael W.; Hathaway, Kent K.

    2016-05-01

    Fiber optic systems are deployed in a variety of settings as strain sensors to locate small disturbances along the length of the optical fiber cable, which is often tens of kilometers long. This technology has the advantages of low cost and design simplicity, as the sensor is its own source of telemetry and may be easily repaired or replaced. One of the limitations of current technology is noise from optical backscatter events in the fiber resulting in a degraded signal in individual spatial zones leading to signal fading. Detection within these zones along the length of the fiber is then obscured. Signal multiplexing may be used to increase sensitivity and signal-to-noise ratio and reduce signal fading. In such an architecture, multiple channels are multiplexed together and transmitted along the fiber. In this article, we report on results from two different systems that were tested using such techniques. Results are then compared with a single channel system.

  13. Optical signal processing of spatially distributed sensor data in smart structures

    NASA Technical Reports Server (NTRS)

    Bennett, K. D.; Claus, R. O.; Murphy, K. A.; Goette, A. M.

    1989-01-01

    Smart structures which contain dense two- or three-dimensional arrays of attached or embedded sensor elements inherently require signal multiplexing and processing capabilities to permit good spatial data resolution as well as the adequately short calculation times demanded by real time active feedback actuator drive circuitry. This paper reports the implementation of an in-line optical signal processor and its application in a structural sensing system which incorporates multiple discrete optical fiber sensor elements. The signal processor consists of an array of optical fiber couplers having tailored s-parameters and arranged to allow gray code amplitude scaling of sensor inputs. The use of this signal processor in systems designed to indicate the location of distributed strain and damage in composite materials, as well as to quantitatively characterize that damage, is described. Extension of similar signal processing methods to more complicated smart materials and structures applications are discussed.

  14. Photoelectric Hybrid Optical Bistable Device Using Fibre Bragg Gratings with Two Feed Signals

    NASA Astrophysics Data System (ADS)

    Ye, Hong-An; Zhang, Xin-Ming; Zhu, Yong

    2004-05-01

    A photoelectric hybrid optical bistable device (OBD) is investigated by using fibre Bragg gratings as a light-intensity modulator. A new operation with two feed signals is proposed, and with this method the output characteristic of the OBD is remarkably improved. The potential application of such a device in optic stabilizer for fibre laser is also briefly discussed.

  15. Thin-Film Guided-Wave Devices for Integrated/Fiber Optic Signal Processing and Communications

    DTIC Science & Technology

    1983-04-22

    Acousto - Optic Irag Deflector Using a Tilted Finger Chirp Transducer," Ing 3. Quantum Electron., Vol. Q-15, 1166-1170 (October 1979). b. K.Y. Liao, C.L...t .R~ (o..........*. .c... . I.-,vW d *. Integrated and Guided-Wave Optics , Multichannel Communication and Signal Processing, using Tilted Finger... optical waveguide in the (001) plane of a GaAs substrate with the SAW propagating in the 100> direction. A paper in connection with topic # 2 was

  16. Universal Michelson Gires-Tournois interferometer optical interleaver based on digital signal processing.

    PubMed

    Zhang, Juan; Yang, Xiaowei

    2010-03-01

    Optical interleavers based on Michelson Gires-Tournois interferometer (MGTI) with arbitrary cascaded reflectors for symmetrical or asymmetrical periodic frequency response with arbitrary duty cycles are defined as universal MGTI optical interleaver (UMGTIOI). It can significantly enhance flexibility and applicability of optical networks. A novel and simple method based on digital signal processing is proposed for the design of UMGTIOI. Different kinds of design examples are given to confirm effectiveness of the method.

  17. Marine guanidine alkaloids crambescidins inhibit tumor growth and activate intrinsic apoptotic signaling inducing tumor regression in a colorectal carcinoma zebrafish xenograft model

    PubMed Central

    Roel, María; Rubiolo, Juan A.; Guerra-Varela, Jorge; Silva, Siguara B. L.; Thomas, Olivier P.; Cabezas-Sainz, Pablo; Sánchez, Laura; López, Rafael; Botana, Luis M.

    2016-01-01

    The marine environment constitutes an extraordinary resource for the discovery of new therapeutic agents. In the present manuscript we studied the effect of 3 different sponge derived guanidine alkaloids, crambescidine-816, -830, and -800. We show that these compounds strongly inhibit tumor cell proliferation by down-regulating cyclin-dependent kinases 2/6 and cyclins D/A expression while up-regulating the cell cyclin-dependent kinase inhibitors -2A, -2D and -1A. We also show that these guanidine compounds disrupt tumor cell adhesion and cytoskeletal integrity promoting the activation of the intrinsic apoptotic signaling, resulting in loss of mitochondrial membrane potential and concomitant caspase-3 cleavage and activation. The crambescidin 816 anti-tumor effect was fnally assayed in a zebrafish xenotransplantation model confirming its potent antitumor activity against colorectal carcinoma in vivo. Considering these results crambescidins could represent promising natural anticancer agents and therapeutic tools. PMID:27825113

  18. Marine guanidine alkaloids crambescidins inhibit tumor growth and activate intrinsic apoptotic signaling inducing tumor regression in a colorectal carcinoma zebrafish xenograft model.

    PubMed

    Roel, María; Rubiolo, Juan A; Guerra-Varela, Jorge; Silva, Siguara B L; Thomas, Olivier P; Cabezas-Sainz, Pablo; Sánchez, Laura; López, Rafael; Botana, Luis M

    2016-12-13

    The marine environment constitutes an extraordinary resource for the discovery of new therapeutic agents. In the present manuscript we studied the effect of 3 different sponge derived guanidine alkaloids, crambescidine-816, -830, and -800. We show that these compounds strongly inhibit tumor cell proliferation by down-regulating cyclin-dependent kinases 2/6 and cyclins D/A expression while up-regulating the cell cyclin-dependent kinase inhibitors -2A, -2D and -1A. We also show that these guanidine compounds disrupt tumor cell adhesion and cytoskeletal integrity promoting the activation of the intrinsic apoptotic signaling, resulting in loss of mitochondrial membrane potential and concomitant caspase-3 cleavage and activation. The crambescidin 816 anti-tumor effect was fnally assayed in a zebrafish xenotransplantation model confirming its potent antitumor activity against colorectal carcinoma in vivo.Considering these results crambescidins could represent promising natural anticancer agents and therapeutic tools.

  19. From the intrinsic properties to the functional role of a neuron phenotype: an example from electric fish during signal trade-off.

    PubMed

    Nogueira, Javier; Caputi, Angel A

    2013-07-01

    This review deals with the question: what is the relationship between the properties of a neuron and the role that the neuron plays within a given neural circuit? Answering this kind of question requires collecting evidence from multiple neuron phenotypes and comparing the role of each type in circuits that perform well-defined computational tasks. The focus here is on the spherical neurons in the electrosensory lobe of the electric fish Gymnotus omarorum. They belong to the one-spike-onset phenotype expressed at the early stages of signal processing in various sensory modalities and diverse taxa. First, we refer to the one-spike neuron intrinsic properties, their foundation on a low-threshold K(+) conductance, and the potential roles of this phenotype in different circuits within a comparative framework. Second, we present a brief description of the active electric sense of weakly electric fish and the particularities of spherical one-spike-onset neurons in the electrosensory lobe of G. omarorum. Third, we introduce one of the specific tasks in which these neurons are involved: the trade-off between self- and allo-generated signals. Fourth, we discuss recent evidence indicating a still-undescribed role for the one-spike phenotype. This role deals with the blockage of the pathway after being activated by the self-generated electric organ discharge and how this blockage favors self-generated electrosensory information in the context of allo-generated interference. Based on comparative analysis we conclude that one-spike-onset neurons may play several functional roles in animal sensory behavior. There are specific adaptations of the neuron's 'response function' to the circuit and task. Conversely, the way in which a task is accomplished depends on the intrinsic properties of the neurons involved. In short, the role of a neuron within a circuit depends on the neuron and its functional context.

  20. On-Board Fiber-Optic Network Architectures for Radar and Avionics Signal Distribution

    NASA Technical Reports Server (NTRS)

    Alam, Mohammad F.; Atiquzzaman, Mohammed; Duncan, Bradley B.; Nguyen, Hung; Kunath, Richard

    2000-01-01

    Continued progress in both civil and military avionics applications is overstressing the capabilities of existing radio-frequency (RF) communication networks based on coaxial cables on board modem aircrafts. Future avionics systems will require high-bandwidth on- board communication links that are lightweight, immune to electromagnetic interference, and highly reliable. Fiber optic communication technology can meet all these challenges in a cost-effective manner. Recently, digital fiber-optic communication systems, where a fiber-optic network acts like a local area network (LAN) for digital data communications, have become a topic of extensive research and development. Although a fiber-optic system can be designed to transport radio-frequency (RF) signals, the digital fiber-optic systems under development today are not capable of transporting microwave and millimeter-wave RF signals used in radar and avionics systems on board an aircraft. Recent advances in fiber optic technology, especially wavelength division multiplexing (WDM), has opened a number of possibilities for designing on-board fiber optic networks, including all-optical networks for radar and avionics RF signal distribution. In this paper, we investigate a number of different novel approaches for fiber-optic transmission of on-board VHF and UHF RF signals using commercial off-the-shelf (COTS) components. The relative merits and demerits of each architecture are discussed, and the suitability of each architecture for particular applications is pointed out. All-optical approaches show better performance than other traditional approaches in terms of signal-to-noise ratio, power consumption, and weight requirements.

  1. Optical fiber sensors and signal processing for intelligent structure monitoring

    NASA Technical Reports Server (NTRS)

    Rogowski, Robert; Claus, R. O.; Lindner, D. K.; Thomas, Daniel; Cox, Dave

    1988-01-01

    The analytic and experimental performance of optical fiber sensors for the control of vibration of large aerospace and other structures are investigated. In particular, model domain optical fiber sensor systems, are being studied due to their apparent potential as distributed, low mass sensors of vibration over appropriate ranges of both low frequency and low amplitude displacements. Progress during the past three months is outlined. Progress since September is divided into work in the areas of experimental hardware development, analytical analysis, control design and sensor development. During the next six months, tests of a prototype closed-loop control system for a beam are planned which will demonstrate the solution of several optical fiber instrumentation device problems, the performance of the control system theory which incorporates the model of the modal domain sensor, and the potential for distributed control which this sensor approach offers.

  2. Experimental investigation of chirp properties induced by signal amplification in quantum-dot semiconductor optical amplifiers.

    PubMed

    Matsuura, Motoharu; Ohta, Hiroaki; Seki, Ryota

    2015-03-15

    We experimentally show the dynamic frequency chirp properties induced by signal amplification in a quantum-dot semiconductor optical amplifier (QD-SOA) for the first time. We also compare the red and blue chirp peak values and temporal chirp changes while changing the gain and injected signal powers of the QD-SOA with those of a common SOA.

  3. Secure communications of CAP-4 and OOK signals over MMF based on electro-optic chaos.

    PubMed

    Ai, Jianzhou; Wang, Lulu; Wang, Jian

    2017-09-15

    Chaos-based secure communication can provide a high level of privacy in data transmission. Here, we experimentally demonstrate secure signal transmission over two kinds of multimode fiber (MMF) based on electro-optic intensity chaos. High-quality synchronization is achieved in an electro-optic feedback configuration. Both 5  Gbit/s carrier-less amplitude/phase (CAP-4) modulation and 10  Gbit/s on-off key (OOK) signals are recovered efficiently in electro-optic chaos-based communication systems. Degradations of chaos synchronization and communication system due to mismatch of various hardware keys are also discussed.

  4. Paired SSB optical OFDM channels for high spectral efficient signal transmission over DWDM networks

    NASA Astrophysics Data System (ADS)

    Chicharro, Francisco I.; Ortega, Beatriz; Mora, José

    2016-07-01

    A new high spectral efficient SSB-OOFDM DWDM transmission system has been experimentally demonstrated. The proposed transmitter employs paired optical channels consisting of two SSB modulated OFDM signals using opposite sidebands in order to allow an efficient use of the spectrum with optical carriers separation under 10 GHz. Moreover, different paired channels are multiplexed into the 25 GHz grid DWDM fiber transmission link. Optical carrier spacing of 8.75 GHz in paired channels has been demonstrated allowing 40.8 Gb/s signal transmission rate over a 25 GHz paired channel bandwidth.

  5. Detection of optical circulator crosstalk based on signal modulation

    NASA Astrophysics Data System (ADS)

    Shao, Qiu-feng; Zhang, Qian; Yang, Rui; Zhang, Heng

    2014-12-01

    A novel method based on piezoelectric transducer (PZT) modulation for detecting the crosstalk of optical circulator has been demonstrated. In the experiment, the lightwave emitted from a low-noise single-frequency laser passed through the circulator, reflected on the surface of the PZT, and returned to the circulator again. The PZT can modulate the frequency of the lightwave reflected on it due to the Doppler effect. Then the crosstalk of the circulator is obtained by measuring the induced optical difference frequency based on a difference-frequency detection technology. The results show that this method is very effective in detecting weak crosstalk of circulator.

  6. Hematocrit dependence of flow signal in optical coherence tomography angiography

    PubMed Central

    Yang, Jianlong; Su, Johnny; Wang, Jie; Men, Silu; Jia, Yali; Huang, David; Liu, Gangjun

    2017-01-01

    The hematocrit dependence of flow signal (split-spectrum amplitude decorrelation angiography-SSADA decorrelation value) was investigated in this paper. Based on the normalized field temporal correlation function and concentration dependent particle scattering properties, the relationship between hematocrit and flow signal was analytically derived. Experimental verification of the relationship was performed with custom-designed microfluidic chips and human blood with 45%, 40% and 32% hematocrit. It was found that, in large flow channels and blood vessels, the normal hematocrit is near the decorrelation saturation point and therefore a change in hematocrit has little effect on the SSADA decorrelation value (flow signal). However, in narrow channels in the capillary size range, the effective hematocrit (adjusted for the overlap between OCT beam and channel) is in the range of 6.7-9.5% and therefore variation in hematocrit does significantly affect the flow signal. PMID:28270984

  7. Low-frequency analog signal distribution on digital photonic networks by optical delta-sigma modulation

    NASA Astrophysics Data System (ADS)

    Kanno, Atsushi; Kawanishi, Tetsuya

    2013-12-01

    We propose a delta-sigma modulation scheme for low- and medium-frequency signal transmission in a digital photonic network system. A 10-Gb/s-class optical transceiver with a delta-sigma modulator utilized as a high-speed analog-to-digital converter (ADC) provides a binary optical signal. On the signal reception side, a low-cost and slow-speed photonic receiver directly converts the binary signal into an analog signal at frequencies from several hundreds of kilohertz several tens of megahertz. Further, by using a clock and data recovery circuit at the receiver to reduce jitters, the single-sideband phase noise of the generated signals can be significantly reduced.

  8. Photoacoustic correlation signal-to-noise ratio enhancement by coherent averaging and optical waveform optimization.

    PubMed

    Telenkov, Sergey A; Alwi, Rudolf; Mandelis, Andreas

    2013-10-01

    Photoacoustic (PA) imaging of biological tissues using laser diodes instead of conventional Q-switched pulsed systems provides an attractive alternative for biomedical applications. However, the relatively low energy of laser diodes operating in the pulsed regime, results in generation of very weak acoustic waves, and low signal-to-noise ratio (SNR) of the detected signals. This problem can be addressed if optical excitation is modulated using custom waveforms and correlation processing is employed to increase SNR through signal compression. This work investigates the effect of the parameters of the modulation waveform on the resulting correlation signal and offers a practical means for optimizing PA signal detection. The advantage of coherent signal averaging is demonstrated using theoretical analysis and a numerical model of PA generation. It was shown that an additional 5-10 dB of SNR can be gained through waveform engineering by adjusting the parameters and profile of optical modulation waveforms.

  9. Secure chaotic transmission of electrocardiography signals with acousto-optic modulation under profiled beam propagation.

    PubMed

    Almehmadi, Fares S; Chatterjee, Monish R

    2015-01-10

    Electrocardiography (ECG) signals are used for both medical purposes and identifying individuals. It is often necessary to encrypt this highly sensitive information before it is transmitted over any channel. A closed-loop acousto-optic hybrid device acting as a chaotic modulator is applied to ECG signals to achieve this encryption. Recently improved modeling of this approach using profiled optical beams has shown it to be very sensitive to key parameters that characterize the encryption and decryption process, exhibiting its potential for secure transmission of analog and digital signals. Here the encryption and decryption is demonstrated for ECG signals, both analog and digital versions, illustrating strong encryption without significant distortion. Performance analysis pertinent to both analog and digital transmission of the ECG waveform is also carried out using output signal-to-noise, signal-to-distortion, and bit-error-rate measures relative to the key parameters and presence of channel noise in the system.

  10. All-Optical Demultiplexing of WLAN and Cellular CDMA Radio Signals

    NASA Astrophysics Data System (ADS)

    Kosek, Hatice; He, Yifeng; Gu, Xijia; Fernando, Xavier N.

    2007-06-01

    Subcarrier multiplexed transmission of multimedia radio signals over fiber is often done to deliver broadband services cost effectively. These signals need to be demultiplexed, preferably in the optical domain, to avoid loss and noise due to optical-to- electrical conversion. However, it is challenging to optically isolate signals at subgigahertz range due to the need for very narrow optical bandpass filters with high selectivity and low insertion loss and distortion. We developed such a novel subpicometer all-optical bandpass filter by creating a resonance cavity using two closely matched fiber Bragg gratings. This filter has a bandwidth of 120 MHz at -3 dB, 360 MHz at -10 dB, and 1.5 GHz at -20 dB. Experimental results show that this filter optically separates two RF signals spaced as close as 50 MHz without significant distortion. This paper analytically and experimentally investigates the scenario when this filter was used with 2.4-GHz (wireless local area network) and 900-MHz (cellular wireless) radio signals. The bit-error rate of the underlying baseband data is related to the linearity and isolation of the filter.

  11. Efficient orientational averaging of nonlinear optical signals in multi-chromophore systems

    NASA Astrophysics Data System (ADS)

    Gelin, Maxim F.; Borrelli, Raffaele; Domcke, Wolfgang

    2017-07-01

    The simulation of nonlinear optical signals measured in isotropic media requires averaging over the orientations of the chromophores. Herein, we discuss the evaluation of orientationally averaged four-wave-mixing, six-wave-mixing, etc., signals in terms of contracted transition dipole moment operators, which were introduced earlier for the orientational averaging of linear absorption signals. We demonstrate that the contracted transition dipole moment operators substantially facilitate the orientational averaging of nonlinear signals in multi-chromophore systems. We consider both the perturbative evaluation of signals (through nonlinear response functions) as well as the nonperturbative evaluation (through the numerical calculation of the nonlinear polarization of driven systems).

  12. The canonical intrinsic mitochondrial death pathway has a non-apoptotic role in signaling lens cell differentiation.

    PubMed

    Weber, Gregory F; Menko, A Sue

    2005-06-10

    The mitochondrial cell death pathway is known for its role in signaling apoptosis. Here, we describe a novel function for the mitochondrial cell death pathway in signaling initiation of differentiation in the developing lens. Most remarkably, we induced lens cell differentiation by short-term exposure of lens epithelial cells to the apoptogen staurosporine. Activation of apoptosis-related pathways induced lens epithelial cells to express differentiation-specific markers and to undergo morphogenetic changes that led to formation of the lens-like structures known as lentoids. The fact that multiple stages of differentiation are expressed at a single stage of development in the embryonic lens made it possible to precisely determine the timing of expression of proteins associated with the apoptotic pathway. We discovered that there was high expression in the lens equatorial epithelium (the region of the lens in which differentiation is initiated) of pro-apoptotic molecules such as Bax and Bcl-x(S) and release of cytochrome c from mitochondria. Furthermore, we found significant caspase-3-like activity in the equatorial epithelium, yet this activity was far lower than that associated with lens cell apoptosis. These apoptotic pathways are likely regulated by the concurrent expression of prosurvival molecules, including Bcl-2 and Bcl-x(L); phosphorylation of Bad; and high expression of inhibitor of apoptosis proteins chicken IAP1, IAP3, and survivin. This finding suggests that prosurvival pathways allow pro-apoptotic molecules to function as molecular switches in the differentiation process without tipping the balance toward apoptosis. We call this process apoptosis-related Bcl-2- and caspase-dependent (ABC) differentiation.

  13. Cloud Optical Depth Retrievals from Solar Background "signal" of Micropulse Lidars

    NASA Technical Reports Server (NTRS)

    Chiu, J. Christine; Marshak, A.; Wiscombe, W.; Valencia, S.; Welton, E. J.

    2007-01-01

    Pulsed lidars are commonly used to retrieve vertical distributions of cloud and aerosol layers. It is widely believed that lidar cloud retrievals (other than cloud base altitude) are limited to optically thin clouds. Here we demonstrate that lidars can retrieve optical depths of thick clouds using solar background light as a signal, rather than (as now) merely a noise to be subtracted. Validations against other instruments show that retrieved cloud optical depths agree within 10-15% for overcast stratus and broken clouds. In fact, for broken cloud situations one can retrieve not only the aerosol properties in clear-sky periods using lidar signals, but also the optical depth of thick clouds in cloudy periods using solar background signals. This indicates that, in general, it may be possible to retrieve both aerosol and cloud properties using a single lidar. Thus, lidar observations have great untapped potential to study interactions between clouds and aerosols.

  14. The optical crossbar switch for signal routeing on board communication satellites

    NASA Astrophysics Data System (ADS)

    Baister, G. C.; Gatenby, P. V.; Aldridge, N.; Stace, C.; White, H.

    1994-04-01

    A switch matrix operating on baseband or microwave signals is a critical element of communications satellites employing multiple beam antennas and on-board switching. Optical switching by spatial light modulators (SLMs) offers a means of implementing large and highly flexible switch arrays capable of routeing signals at baseband or microwave frequencies. This approach offers potential mass, power and size advantages compared to alternative technologies. This paper reviews the essential features of optical crossbar switch architectures based on SLMs and discusses options for the lasers, ALMs, interface optics and photodetectors. Proof-of-concept demonstrators for optical crossbar switches operating on both baseband and microwave signals are described. Finally, an outline design for a compact switch module is described and the critical component developments needed to realize this are identified.

  15. Theoretical and Experimental Study of Optical Coherence Tomography (OCT) Signals Using an Analytical Transport Model

    SciTech Connect

    Vazquez Villa, A.; Delgado Atencio, J. A.; Vazquez y Montiel, S.; Cunill Rodriguez, M.; Martinez Rodriguez, A. E.; Ramos, J. Castro; Villanueva, A.

    2010-12-07

    Optical coherence tomography (OCT) is a non-invasive low coherent interferometric technique that provides cross-sectional images of turbid media. OCT is based on the classical Michelson interferometer where the mirror of the reference arm is oscillating and the signal arm contains a biological sample. In this work, we analyzed theoretically the heterodyne optical signal adopting the so called extended Huygens-Fresnel principle (EHFP). We use simulated OCT images with known optical properties to test an algorithm developed by ourselves to recover the scattering coefficient and we recovered the scattering coefficient with a relative error less than 5% for noisy signals. In addition, we applied this algorithm to OCT images from phantoms of known optical properties; in this case curves were indistinguishable. A revision of the validity of the analytical model applied to our system should be done.

  16. The LSR/2 Optically Coupled Signal Transmission Link.

    DTIC Science & Technology

    1979-12-01

    OPTICAL SCI DIV ATTN DYR, R&D DIV WASHINGTON, DC 20375 ATTN XO, DIR TEST ARNOLD AIR FORCE STATION, TN 37389 COMMANDER NAVAL SEA SYSTEMS COMMAND HQ DIRECTOR...AIRCRAFT COMPANY SCIENCE APPLICATIONS, INC. ATTN R. BLAIR ATTN P. MILLER MALIBU CANYON ROAD 1257 TASMAN DRIVE MALIBU, CA 90265 SUNNYVALE, CA 94086 24

  17. Quantum issues in optical communication. [noise reduction in signal reception

    NASA Technical Reports Server (NTRS)

    Kennedy, R. S.

    1973-01-01

    Various approaches to the problem of controlling quantum noise, the dominant noise in an optical communications system, are discussed. It is shown that, no matter which way the problem is approached, there always remain uncertainties. These uncertainties exist because, to date, only very few communication problems have been solved in their full quantum form.

  18. Alignment signal extraction of the optically degenerate RSE interferometer using the wave front sensing technique

    NASA Astrophysics Data System (ADS)

    Sato, S.; Kawamura, S.

    2008-07-01

    The alignment sensing and control scheme of the resonant sideband extraction interferometer is still an unsettled issue for the next-generation gravitational wave antennas. The issue is that it is difficult to extract separate error signals for all 12 angular degrees of freedom, which is mainly arising from the complexity of the optical system and cavity 'degeneracy'. We have suggested a new sensing scheme giving reasonably separated signals which is fully compatible with the length sensing scheme. The key of this idea is to resolve the 'degeneracy' of the optical cavities. By choosing an appropriate Gouy phase for the degenerate cavities, alignment error signals with much less admixtures can be extracted.

  19. Influence of Injection Molding Process on the Local Fluctuations of Magneto-Optical Signals

    NASA Astrophysics Data System (ADS)

    Umezawa, Tomokazu; Horiguchi, Toru; Tomie, Takashi

    2001-01-01

    The local fluctuations of magneto-optical (MO) signals were investigated in the vicinity of the preformat pits of polycarbonate (PC) substrates fabricated under different injection molding conditions and also using stampers which had different shapes of grooves and preformat pits. A strong correlation was observed between the substrate birefringence and the fluctuation of the MO signal. The rate-of-change of the fluctuations, as the phase shift of the optical head was varied, was attributed to the shapes of preformat pits and grooves. The fluctuation of the MO signal could be controlled by varying the injection molding conditions and the shapes of preformat pits and grooves.

  20. An analog modulation and demodulation method employing LVDT signal conditioner for fiber-optic interferometric sensors

    NASA Astrophysics Data System (ADS)

    Zhou, Kejiang; Rao, Qi; Zhang, Minjie; Hu, Keke; Ruan, Yefeng

    2017-09-01

    An analog method to modulate and demodulate fiber-optic interferometric sensors employing a linear variable differential transformer signal conditioner to generate sine modulation wave and demodulate phase-modulated signal from the photodetector’s output is presented in this letter. No external lock-in amplifiers or digital components are used in this design. All the necessary components for signal processing are integrated in a single analog electronic microchip AD698, which reduces the system’s complexity significantly. After implementation on an interferometric fiber-optic gyroscope as an example, this method demonstrates a bias stability of 0.063 deg h-1 (i.e. 0.220 µrad).

  1. High Speed All Optical Nyquist Signal Generation and Full-band Coherent Detection

    PubMed Central

    Zhang, Junwen; Yu, Jianjun; Fang, Yuan; Chi, Nan

    2014-01-01

    Spectrum efficient data transmission is of key interest for high capacity optical communication systems considering the limited available bandwidth. Transmission of the high speed signal with higher-order modulation formats within the Nyquist bandwidth using coherent detection brings attractive performance advantages. However, high speed Nyquist signal generation with high order modulation formats is challenging. Electrical Nyquist pulse generation is restricted by the limited sampling rate and processor capacities of digital-to-analog convertor devices, while the optical Nyquist signals can provide a much higher symbol rate using time domain multiplexing method. However, most optical Nyquist signals are based on direct detection with simple modulation formats. Here we report the first experimental demonstration of high speed all optical Nyquist signal generation based on Sinc-shaped pulse generation and time-division multiplexing with high level modulation format and full-band coherent detection. Our experiments demonstrate a highly flexible and compatible all optical high speed Nyquist signal generation and detection scheme for future fiber communication systems. PMID:25142269

  2. Optical techniques for signal distribution and control in advanced radar and communication systems

    NASA Astrophysics Data System (ADS)

    Forrest, J. R.

    1985-03-01

    It is concluded that optical techniques offer some advantages for signal distribution and control in advanced radar and communication systems. They are clearly ideal for transporting microwave signals over considerable distances, as in remote positioning of radar receivers, provided high dynamic range is not required and an enclosed transmission path is essential. They are an elegant means of distributing low level r.f. or i.f. signals around an active phased array where these signals are of relatively constant amplitude (as in mixer local oscillator applications). However, there is currently a rather restrictive limit on the size of distribution network possible. Optical techniques are obviously suitable for distributing digital control signals to phased array modules and confer considerable immunity to interference. They are less suitable for high dynamic range signals, such as the received radar returns, either at r.f. or when downcovered to i.f. Future developments in coherent optics or in fast optical A/D technology could, however, influence this conclusion. Currently, the optimum applications for optical techniques appear to be i.f. beamformers for multibeam communication satellite systems and in calibration/monitoring systems for phased arrays.

  3. Coherent Detection of Optical Quadrature Phase-Shift Keying Signals With Carrier Phase Estimation

    NASA Astrophysics Data System (ADS)

    Ly-Gagnon, Dany-Sebastien; Tsukamoto, Satoshi; Katoh, Kazuhiro; Kikuchi, Kazuro

    2006-01-01

    This paper describes a coherent optical receiver for demodulating optical quadrature phase-shift keying (QPSK) signals. At the receiver, a phase-diversity homodyne detection scheme is employed without locking the phase of the local oscillator (LO). To handle the carrier phase drift, the carrier phase is estimated with digital signal processing (DSP) on the homodyne-detected signal. Such a scheme presents the following major advantages over the conventional optical differential detection. First, its bit error rate (BER) performance is better than that of differential detection. This higher sensitivity can extend the reach of unrepeated transmission systems and reduce crosstalk between multiwavelength channels. Second, the optoelectronic conversion process is linear, so that the whole optical signal information can be postprocessed in the electrical domain. Third, this scheme is applicable to multilevel modulation formats such as M-array PSK and quadrature amplitude modulation (QAM). The performance of the receiver is evaluated through various simulations and experiments. As a result, an unrepeated transmission over 210 km with a 20-Gb/s optical QPSK signal is achieved. Moreover, in wavelength-division multiplexing (WDM) environment, coherent detection allows the filtering of a desired wavelength channel to reside entirely in the electrical domain, taking advantage of the sharp cutoff characteristics of electrical filters. The experiments show the feasibility to transmit polarization-multiplexed 40-Gb/s QPSK signals over 200 km with channel spacing of 16 GHz, leading to a spectral efficiency as high as 2.5 b/s/Hz.

  4. Canonical Wnt/β-catenin signalling is essential for optic cup formation.

    PubMed

    Hägglund, Anna-Carin; Berghard, Anna; Carlsson, Leif

    2013-01-01

    A multitude of signalling pathways are involved in the process of forming an eye. Here we demonstrate that β-catenin is essential for eye development as inactivation of β-catenin prior to cellular specification in the optic vesicle caused anophthalmia in mice. By achieving this early and tissue-specific β-catenin inactivation we find that retinal pigment epithelium (RPE) commitment was blocked and eye development was arrested prior to optic cup formation due to a loss of canonical Wnt signalling in the dorsal optic vesicle. Thus, these results show that Wnt/β-catenin signalling is required earlier and play a more central role in eye development than previous studies have indicated. In our genetic model system a few RPE cells could escape β-catenin inactivation leading to the formation of a small optic rudiment. The optic rudiment contained several neural retinal cell classes surrounded by an RPE. Unlike the RPE cells, the neural retinal cells could be β-catenin-negative revealing that differentiation of the neural retinal cell classes is β-catenin-independent. Moreover, although dorsoventral patterning is initiated in the mutant optic vesicle, the neural retinal cells in the optic rudiment displayed almost exclusively ventral identity. Thus, β-catenin is required for optic cup formation, commitment to RPE cells and maintenance of dorsal identity of the retina.

  5. RF frequency sextupling via an optical two-tone signal generated from two modulation lightwaves from one Mach-Zehnder optical modulator.

    PubMed

    Chiba, Akito; Akamatsu, Yosuke; Takada, Kazumasa

    2015-10-05

    An optical two-tone (OTT) signal is generated with a wide frequency separation, based on the suppression of ± 1st-order optical sidebands without using optical band-rejection filtering. By combining two orthogonally polarized lightwaves modulated with different modulation indices, each optical sideband constituting the combined lightwave has a different polarization. Some of these optical sidebands can be suppressed using a polarizer. By using a single Mach-Zehnder optical modulator to achieve two optical modulations, an OTT signal with a 60-GHz frequency-separation was successfully generated with 32-dB suppression of undesired ± 1st-order optical sidebands. An rf signal was also obtained from the OTT signal.

  6. A Correlation Between Intrinsic Brightness and Average Decay Rate of Swift UVOT GRB Optical/UV Light Curves

    NASA Technical Reports Server (NTRS)

    Oates, S. R.; Page, M. J.; De Pasquale, M.; Schady, P.; Breeveld, A. A.; Holland, S. T.; Kuin, N. P. M.; Marshall, F. E.

    2012-01-01

    We examine a sample of 48 Swift/UVOT long Gamma-ray Burst light curves and find a correlation between the logarithmic luminosity at 200s and average decay rate determined from 200s onwards, with a Spearman rank coefficient of -0.58 at a significance of 99.998% (4.2 sigma ). We discuss the causes of the log L200s - alpha (greater than) 200s correlation, finding it to be an intrinsic property of long GRBs, and not resulting from the selection criteria. We find two ways to produce the correlation. One possibility is that there is some property of the central engine, outflow or external medium that affects the rate of energy release so that the bright afterglows release their energy more quickly and decay faster than the fainter afterglows. Alternatively, the correlation may be produced by variation of the observers viewing angle, with observers at large viewing angles observing fainter and slower decaying light curves.

  7. About the effects of polarising optics on lidar signals and the Δ90 calibration

    NASA Astrophysics Data System (ADS)

    Freudenthaler, Volker

    2016-08-01

    This paper provides a model for assessing the effects of polarising optics on the signals of typical lidar systems, which is based on the description of the individual optical elements of the lidar and of the state of polarisation of the light by means of the Müller-Stokes formalism. General analytical equations are derived for the dependence of the lidar signals on polarisation parameters, for the linear depolarisation ratio, and for the signals of different polarisation calibration setups. The equations can also be used for the calculation of systematic errors caused by nonideal optical elements, their rotational misalignment, and by non-ideal laser polarisation. We present the description of the lidar signals including the polarisation calibration in a closed form, which can be applied for a large variety of lidar systems.

  8. Signal-quality consideration for dynamic connection provisioning in all-optical wavelength-routed networks

    NASA Astrophysics Data System (ADS)

    Huang, Yurong R.; Wen, Wushao; Heritage, Jonathan P.; Mukherjee, Biswanath

    2003-10-01

    We investigate new connection-provisioning algorithms to efficiently provide signal-quality-guaranteed connections in an all-optical WDM mesh network. In the all-optical network, signal degradations incurred by non-ideal transmission medium accumulate along a lightpath. When the signal degradation reaches a certain level, the connection is not usable and is blocked due to transmission impairments in the physical layer. To ensure high service quality of provisioned connections, it is essential to develop intelligent routing and wavelength assignment (RWA) algorithms which can combat the effects of impairments when setting up a connection. For this purpose, we propose two impairment-aware RWA algorithms, namely impairment-aware best-path (IABP) algorithm and impairment-aware first-fit (IAFF) algorithm. The optical signal-to-noise raito (OSNR) requirement and polarization mode dispersion (PMD) effect are used as signal-quality constraints to avoid setting up a connection with unacceptable quality due to the effects of transmission impairments. With the signal-quality consideration, as compared to algorithms that are not impairment aware in a realistic optical network, our proposed impairment-aware algorithms efficiently provide signal-quality-guaranteed connection while significantly reducing connection-blocking probability, better utilizing network resources, and having a reasonable computational requirement. Also, the effect of channel bit rate is studied in this paper.

  9. Dispersion tolerance of Miller signal in optical domain

    NASA Astrophysics Data System (ADS)

    Metya, Sanjeev Kumar; Janyani, Vijay; Modani, Shri Gopal

    2011-12-01

    An optical Miller coding scheme is proposed with the help of high speed electrical logic gates. With both Miller and Manchester being from the same family of code, i.e., 1B/2B, the former has less electrical spectrum compared with that of Manchester coding and thereby demonstrates a relatively higher tolerance against fiber dispersion within a certain range of distance. The applicability of this code in optical communication has not been explored adequately by the researchers until now, despite its advantages. Here we have investigated the dispersion tolerance of this code and found it to be nearly 1.2 times that of Manchester coding. The dispersion tolerance of Miller code obtained is from -306.4 to +263.9 ps/nm at 1 dB power penalty.

  10. Determination of critical diameters for intrinsic carrier diffusion-length of GaN nanorods with cryo-scanning near-field optical microscopy

    PubMed Central

    Chen, Y. T.; Karlsson, K. F.; Birch, J.; Holtz, P. O.

    2016-01-01

    Direct measurements of carrier diffusion in GaN nanorods with a designed InGaN/GaN layer-in-a-wire structure by scanning near-field optical microscopy (SNOM) were performed at liquid-helium temperatures of 10 K. Without an applied voltage, intrinsic diffusion lengths of photo-excited carriers were measured as the diameters of the nanorods differ from 50 to 800 nm. The critical diameter of nanorods for carrier diffusion is concluded as 170 nm with a statistical approach. Photoluminescence spectra were acquired for different positions of the SNOM tip on the nanorod, corresponding to the origins of the well-defined luminescence peaks, each being related to recombination-centers. The phenomenon originated from surface oxide by direct comparison of two nanorods with similar diameters in a single map has been observed and investigated. PMID:26876009

  11. Optical feedback signal for ultrashort laser pulse ablation of tissue

    SciTech Connect

    Kim, B.-M.; Feit, M.D.; Rubenchik, A.M.; Mammini, B.M.; Da Silva, L.B.

    1997-07-01

    An optical feedback system for controlled precise tissue ablation is discussed. Our setup includes an ultrashort pulse laser (USPL), and a diagnostic system using analysis of either tissue fluorescence or plasma emission luminescence. Current research is focused on discriminating hard and soft tissues such as bone and spinal cord during surgery using either technique. Our experimental observations exhibit considerable spectroscopic contrast between hard and soft tissue, and both techniques offer promise for a practical diagnostic system.

  12. Joint digital signal processing for superchannel coherent optical communication systems.

    PubMed

    Liu, Cheng; Pan, Jie; Detwiler, Thomas; Stark, Andrew; Hsueh, Yu-Ting; Chang, Gee-Kung; Ralph, Stephen E

    2013-04-08

    Ultra-high-speed optical communication systems which can support ≥ 1Tb/s per channel transmission will soon be required to meet the increasing capacity demand. However, 1Tb/s over a single carrier requires either or both a high-level modulation format (i.e. 1024QAM) and a high baud rate. Alternatively, grouping a number of tightly spaced "sub-carriers" to form a terabit superchannel increases channel capacity while minimizing the need for high-level modulation formats and high baud rate, which may allow existing formats, baud rate and components to be exploited. In ideal Nyquist-WDM superchannel systems, optical subcarriers with rectangular spectra are tightly packed at a channel spacing equal to the baud rate, thus achieving the Nyquist bandwidth limit. However, in practical Nyquist-WDM systems, precise electrical or optical control of channel spectra is required to avoid strong inter-channel interference (ICI). Here, we propose and demonstrate a new "super receiver" architecture for practical Nyquist-WDM systems, which jointly detects and demodulates multiple channels simultaneously and mitigates the penalties associated with the limitations of generating ideal Nyquist-WDM spectra. Our receiver-side solution relaxes the filter requirements imposed on the transmitter. Two joint DSP algorithms are developed for linear ICI cancellation and joint carrier-phase recovery. Improved system performance is observed with both experimental and simulation data. Performance analysis under different system configurations is conducted to demonstrate the feasibility and robustness of the proposed joint DSP algorithms.

  13. A method to remove residual signals in fibre optic luminescence dosimeters

    NASA Astrophysics Data System (ADS)

    Lee, J. J.; Liu, P. Z. Y.; McKenzie, D. R.; Suchowerska, N.

    2013-03-01

    Whenever a fibre optic is used to convey a light signal through a radiation field, it is likely that an unwanted background signal will arise from Cerenkov or fluorescent light which will contaminate the signal. In luminescence dosimetry of high energy beams, when a fibre optic is used to convey the signal from the radiation field to the detector, Cerenkov light is the dominant contributor to the background signal and must be corrected for. In this work, a novel method is demonstrated to separate the signal from the unwanted background. A remotely operated shutter is used to block the signal, allowing the residual background in the fibre optic to be quantified. This background is subtracted from the total measurement acquired in a subsequent irradiation, enabling the luminescence signal to be extracted. Two types of shutter mechanism are considered: an electro-mechanical device to intercept the light path and an LCD device to block the light by cross-polarization. Both shutters were characterized and incorporated into a fibre optic dosimetry system used to measure the radiation dose produced by external beam radiation linear accelerators. The dosimeter using each of the shutters in turn was exposed to a 6 MV photon beam to determine their performance, including the measurement of field size dependent output factors. The mechanical shutter determined the output factors to within 0.29% of those measured with an ionization chamber, whereas the LCD shutter gave results that deviated by up to 2.4%. The switching precision of both shutters was good with standard deviations of less than 0.25% and both were able to completely block the light signal when closed. The use of shutters could therefore be applied to any fibre optic based system to quantify and remove a reproducible background arising from any source including ambient, fluorescent and Cerenkov light.

  14. Cellular signaling protective against noise-induced hearing loss – A role for novel intrinsic cochlear signaling involving corticotropin-releasing factor?

    PubMed

    Vetter, Douglas E

    2015-09-01

    Hearing loss afflicts approximately 15% of the world's population, and crosses all socioeconomic boundaries. While great strides have been made in understanding the genetic components of syndromic and non-syndromic hearing loss, understanding of the mechanisms underlying noise-induced hearing loss (NIHL) have come much more slowly. NIHL is not simply a mechanism by which older individuals loose their hearing. Significantly, the incidence of NIHL is increasing, and is now involving ever younger populations. This may predict future increased occurrences of hearing loss. Current research has shown that even short-term exposures to loud sounds generating what was previously considered temporary hearing loss, actually produces an almost immediate and permanent loss of specific populations of auditory nerve fibers. Additionally, recurrent exposures to intense sound may hasten age-related hearing loss. While NIHL is a significant medical concern, to date, few compounds have delivered significant protection, arguing that new targets need to be identified. In this commentary, we will explore cellular signaling processes taking place in the cochlea believed to be involved in protection against hearing loss, and highlight new data suggestive of novel signaling not previously recognized as occurring in the cochlea, that is perhaps protective of hearing. This includes a recently described local hypothalamic-pituitary-adrenal axis (HPA)-like signaling system fully contained in the cochlea. This system may represent a local cellular stress-response system based on stress hormone release similar to the systemic HPA axis. Its discovery may hold hope for new drug therapies that can be delivered directly to the cochlea, circumventing systemic side effects.

  15. Generation of optical OFDM signals using 21.4 GS/s real time digital signal processing.

    PubMed

    Benlachtar, Yannis; Watts, Philip M; Bouziane, Rachid; Milder, Peter; Rangaraj, Deepak; Cartolano, Anthony; Koutsoyannis, Robert; Hoe, James C; Püschel, Markus; Glick, Madeleine; Killey, Robert I

    2009-09-28

    We demonstrate a field programmable gate array (FPGA) based optical orthogonal frequency division multiplexing (OFDM) transmitter implementing real time digital signal processing at a sample rate of 21.4 GS/s. The QPSK-OFDM signal is generated using an 8 bit, 128 point inverse fast Fourier transform (IFFT) core, performing one transform per clock cycle at a clock speed of 167.2 MHz and can be deployed with either a direct-detection or a coherent receiver. The hardware design and the main digital signal processing functions are described, and we show that the main performance limitation is due to the low (4-bit) resolution of the digital-to-analog converter (DAC) and the 8-bit resolution of the IFFT core used. We analyze the back-to-back performance of the transmitter generating an 8.36 Gb/s optical single sideband (SSB) OFDM signal using digital up-conversion, suitable for direct-detection. Additionally, we use the device to transmit 8.36 Gb/s SSB OFDM signals over 200 km of uncompensated standard single mode fiber achieving an overall BER<10(-3).

  16. Optical domain demultiplexing of subcarrier multiplexed cellular and wireless LAN radio signals

    NASA Astrophysics Data System (ADS)

    Fernando, Xavier; Kosek, Hatice; He, Yifeng; Gu, Xijia

    2005-09-01

    Subcarrier multiplexed transmission of cellular (900 MHz), personal communications systems (1.8 GHz) and wireless LAN (2.4 GHz) over the fiber has interesting applications. These multi channel radio over fiber links can connect enhanced wireless hot-spots that will support high speed wireless LAN services or low speed cellular services to different customers from the same antenna. Optical pre-filtering of SCM signals allows the use of inexpensive photodetector and increases network flexibility with fiber based optical filters. However, realizing optical demultiplexing at such low frequencies necessitates optical filters with high selectivity and low insertion loss. In this paper, we implemented a fiber wireless access system, where demultiplexing of subcarrier multiplexed cellular and WLAN signals was demonstrated in optical domain using a sub-picometer bandpass filter. Our novel fiber Bragg grating based bandpass filter has a bandwidth of 120 MHz at -3dB, 360 MHz at -10 dB and 1.5 GHz at -20 dB respectively. We experimentally verified that this filter could adequately isolate signals at as low as 900 MHz from 2.4 GHz. Experimental results show that the designed all optical demultiplexer provides about 25 dB isolation between 900 MHz and 2.4 GHz radio signals.

  17. Transformation of randomly modulated optical signals along a dispersive single-mode fiber-optical waveguide

    SciTech Connect

    Belanov, A.S.; Polukhin, A.T.

    1995-02-01

    Compact relationships for describing the transformation of the correlation function of uniform optical noises along a dispersive single-mode fiber-optical waveguide (SFW) are obtained. As an example of the dispersion-induced distortions in the SFW, an important practical case of optical waves with a regular phase modulation at the SFW input or in one of its parts is considered. 2 refs.

  18. Studies of Beam Expansion and Distributed Bragg Reflector Lasers for Fiber Optics and Optical Signal Processing.

    DTIC Science & Technology

    1981-03-03

    block number) Separate studies were performed on beam expansion and on Distributed Bragg Reflector ( DBR ) lasers preliminary to monolithic integration on...Reflector ( DBR ) laser is a light source compatible with monolithic integrated optics. In the DBR laser one or both cleaved endfaces of a typical double...cleave as a laser cavity mirror. The DBR laser can be used as an integrated optics light source for integrated optical circuits. In this report we

  19. UWB doublet signal generation and modulation based on DFB laser under optical pulses injection

    NASA Astrophysics Data System (ADS)

    Chen, Dalei; Wang, Rong; Xiang, Peng; Pu, Tao; Fang, Tao; Zhou, Hua; Zhao, Jiyong; Huang, Long; Zhu, Huatao; Wang, Peng

    2016-05-01

    In this paper, a novel scheme to generate ultra-wideband (UWB) doublet signals based on the cross-gain modulation (XGM) effect in the DFB lasers is proposed and experimentally demonstrated, the modulation and transmission of the generated UWB doublet signals are also researched. In the proposed system, a gain-switched laser (GSL) is used as a master laser (ML) and the optical pulses from the ML are optically injected into two paralleled DFB lasers, which are used as slave lasers (SL). Then the outputs from the SLs are detected by a balanced photodiode (BPD) to generate the Bi-phased UWB signals. By properly setting the system parameters, UWB signals with various modulation formats such as on-off keying (OOK), pulse amplitude modulation (PAM) as well as the phase-shift keying (PSK) can be generated. In addition, fiber transmission of the modulated UWB signals is also experimentally investigated.

  20. Analog CMOS design for optical coherence tomography signal detection and processing.

    PubMed

    Xu, Wei; Mathine, David L; Barton, Jennifer K

    2008-02-01

    A CMOS circuit was designed and fabricated for optical coherence tomography (OCT) signal detection and processing. The circuit includes a photoreceiver, differential gain stage and lock-in amplifier based demodulator. The photoreceiver consists of a CMOS photodetector and low noise differential transimpedance amplifier which converts the optical interference signal into a voltage. The differential gain stage further amplifies the signal. The in-phase and quadrature channels of the lock-in amplifier each include an analog mixer and switched-capacitor low-pass filter with an external mixer reference signal. The interferogram envelope and phase can be extracted with this configuration, enabling Doppler OCT measurements. A sensitivity of -80 dB is achieved with faithful reproduction of the interferometric signal envelope. A sample image of finger tip is presented.

  1. Application of a fluorescence intensity ratio technique for the intrinsic determination of pH using an optical fiber sensor

    NASA Astrophysics Data System (ADS)

    Thotath, Bhadra; Nguyen, T. Hien; Zhang, Weiwei; Wren, Stephen P.; Baxter, Gregory W.; Sun, Tong; Collins, Stephen F.; Grattan, Kenneth T. V.

    2015-09-01

    An intensity ratio technique has been used for characterizing fluorescence spectra from novel coumarin dyes for pH sensing, in the range of 0.5 - 6, providing results that are independent of possible fluctuations in the intensity of the excitation source, deterioration of the indicator and changes in optical coupling. The arrangement was determined to have a sensitivity of 25% per unit pH change (at a pH of 4).

  2. Development of linear and nonlinear components for integrated optical signal processing

    NASA Astrophysics Data System (ADS)

    Tseng, Shuo-Yen

    Optical processors have potentially a major advantage over electronic processors because of their tremendous bandwidth. Massive parallelism is another inherent advantage of optical processors. However, it is traditionally demonstrated with free space components and seldom used for integrated optical signal processing. In this thesis, we consider spatial domain signal processing in guided wave structures, which brings a new dimension to the existing serial signal processing architecture and takes advantage of the parallelism in optics. A novel class of devices using holograms in multimode channel waveguides is developed in this work. Linear optical signal processing using multimode waveguide holograms (MWHs) is analyzed. We focus on discrete unitary transformations to take advantage of the discrete nature of modes in multimode waveguides. We prove that arbitrary unitary transformations can be performed using holograms in multimode waveguides. A model using the wide-angle beam propagation method (WA-BPM) is developed to simulate the devices and shows good agreement with the theory. The design principle of MWH devices is introduced. Based on the design principle, BPM models are used to design several devices including a mode-order converter, a Hadamard transformer, and an optical pattern generator/correlator. Optical pattern generators are fabricated to verify the theory and the model. Also, the bandwidth and fabrication tolerance of MWH devices are also analyzed. Also, we examine the nonlinear optical switches which allow the integration of MWHs into modern optical communication networks. A simple optical setup using an imaged 2-D phase grating is developed for characterization of the complex third-order nonlinearity chi(3) to identify suitable nonlinear materials for integrated optical switches. This technique provides a reliable way to characterize chi(3) as new materials are constantly being developed. Finally, we demonstrate the concept of optical switching using

  3. Orthogonal optical label swapping and novel BER algorithm for 8PSK signal

    NASA Astrophysics Data System (ADS)

    Tang, Chanjuan; Tao, Li; Li, Rongling; Fang, Wuliang; Zou, Shumin; Chi, Nan

    2011-12-01

    For the first time, we propose a novel BER estimation algorithm for 8PSK signal, the idea of which is also applicable to other multi-dimensional and multi-level modulation formats. And a 2 × 4 orthogonal optical label swapping based on 120Gb/s 8PSK payload and 78Mb/s ASK label by using optical switching devices is demonstrated. Through numerical simulations under different circumstances, we get some orthogonal label switching network's characteristics by analyzing the receiver BER utilizing the new BER algorithm, such as that different combination of label will have a different impact on the transmission performance of the packets. In addition, by changing the receiver optical power, transmitter optical power and optical power launched into the fiber, we get the system's receiver sensitivity, the optimum transmitter power and optimum optical power injected into the fiber, which will be a reference for the actual systems' design.

  4. Temperature dependence of signal loss in precision-wound optical fiber

    NASA Astrophysics Data System (ADS)

    Ruffin, Paul B.; Sung, C. C.

    The thermal characteristics of excess signal loss in unjacketed multimode optical fibers are examined experimentally and theoretically. An unjacketed optical fiber is repeatedly wound under several different tensions and excess optical loss is measured at various temperatures using an Optical Time Domain Reflectometer. It is found that excess optical loss increases below 0 C. The fiber buckling model, used in the thermal analysis of jacketed fibers, is considered for the theoretical evaluation of fiber buckling caused by the mismatch of thermal expansion coefficients between the fiber and coating. The mode coupling theory is used to analyze microbending of the fiber caused by lateral shrinkage of the coating and Young's modulus increase at low temperature in the presence of initial fiber imperfections. A comparison of the data and theoretical results indicates that imperfections at the crossovers are the prime contributor to excess loss at low temperature. Results of the data show that excess optical loss at low temperature increases with winding tension.

  5. Predicting Intrinsic mid-IR to optical flux ratios for galaxies of different types using Spectral Synthesis Models of Composite Stellar Populations

    NASA Astrophysics Data System (ADS)

    Kim, Duho; Jansen, Rolf A.; Windhorst, Rogier A.

    2016-01-01

    We analyze the intrinsic flux ratios of simple and composite stellar populations for various visible--near-infrared filters with respect to ˜3.5μm (L-band), and their dependence on metallicity, star-formation history, and effective mean age. This study is motivated by the fact that light from galaxies is reddened and attenuated by dust via scattering and absorption, where different sightlines across the face of a galaxy suffer various amounts of extinction. Ignoring the effects of this extinction could lead one to infer lower stellar mass, and SFR, or higher metallicity. Tamura et al. (2009) developed an approximate method, dubbed the "βV" method, which corrects for dust-extinction on a pixel-by-pixel basis, by comparing the observed flux ratio and empirical estimate of the intrinsic flux ratio of optical and ˜3.5μm broadband data. Here, we aim to validate and test the limits of the βV method for various filters spanning the visible through near-infrared wavelength range. Through extensive modeling, we test their assumptions for the intrinsic flux ratios for a wide variety of simple and composite stellar populations. We build spectral energy distributions (SEDs) of simple stellar populations (SSPs), by adopting Starburst99 and BC03 models for young (<9Myr) and old (>100Myr) stellar populations, respectively, and linear combinations of these for intermediate ages. We then construct composite stellar population (CSP) SEDs by combining SSP SEDs for various realistic star-formation histories (SFHs). We convolve filter response curves of visible--near-infrared filters for HST imaging surveys and mid-infrared filters in current (WISE, Spitzer/IRAC) and near-future use (JWST/NIRCam) with each model SED, to obtain intrinsic flux ratios (βλ,0). We find that βNIR,0 is only varying slightly as a function of metallicity but is insensitive to SFH or redshift (z≤2). We also find a narrow range of βV,0 (0.7+0.05-0.08) for early Hubble type galaxies (E and S0) using

  6. The non-continuous optical signal identification and data storage on the case of atmospheric disturbances

    NASA Astrophysics Data System (ADS)

    Yu, Si-yuan; Liu, Yong-kai; Ma, Jing; Tan, Li-ying

    2013-08-01

    In the link of satellite to ground laser communication, light signals received by ground terminal receivers are susceptible to interference due to the impact of atmospheric turbulence, and it will result in the degradation of communication quality or even interruption. In this situation, the conventional communication detection device would not be able to analyze the link performance. Thus, it is necessary to develop a set of non-continuous optical signal recognition and storage devices which could work under adverse atmospheric conditions and do the online analysis of the impact of atmospheric on the link of satellite to ground laser. Since the interruption of the optical signal will cause the logical disorders of the high data rate storage system, which uses the CDR output clock as the system clock, general storage device cannot meet the demand of effective storage for communication. In this paper, the usage of FPGA optical signal recovered clock frequency discriminator identified the impact of non-continuous communication signal of atmospheric disturbances effectively. Through the optimization of the system hardware design and software control, we achieved the identification and storage of the laser communication optical signal data while the factor of atmospheric scintillation varying from 0 to 1.5 and the communication data rate being 600Mbps.

  7. Analog signal acquisition from computer optical disk drives for quantitative chemical sensing.

    PubMed

    Potyrailo, Radislav A; Morris, William G; Leach, Andrew M; Sivavec, Timothy M; Wisnudel, Marc B; Boyette, Scott

    2006-08-15

    Optoelectronic consumer products that are widely employed in the office and home attract attention for optical sensor applications due to (1) their cost advantage over analytical instruments produced only in small quantities, (2) robustness in operation due to the detailed manufacturability improvements, and (3) ease of operation. We demonstrate here a new approach for quantitative chemical/biochemical sensing when analog signals are acquired from conventional optical disk drives, and these signals are used for quantitative detection of optical changes of sensor films deposited on conventional CD and DVD optical disks. Because we do not alter manufacturing process of optical disks, any disk can be employed for deposition and readout of sensor films. The optical disk drives also perform their original function of reading and writing digital content to optical media because no optical modifications are introduced to obtain the analog signal. Such a sensor platform is quite universal and can be applied for chemical and biological quantitative detection, as well as for monitoring of changes of physical properties of regions deposited onto a CD or DVD (e.g., during combinatorial screening of materials). As a model example, we demonstrate the concept using chemical detection of ionic species such as Ca2+ in liquids (e.g., blood, urine, or water). Colorimetric calcium-sensitive sensor films were deposited onto a DVD, exposed to water with different concentrations of Ca2+, and quantified in the optical disk drive. The developed lab-on-DVD system demonstrated a 5 ppm detection limit of Ca2+ determinations, similar or slightly better than that achieved using a conventional fiber-optic portable spectrometer. This detection limit corresponded to a 0.023 absorbance unit resolution, as determined by the measurement of the same colorimetric films with a portable spectrometer. Determinations of Ca2+ unknowns using the lab-on-DVD system demonstrated +/-5 ppm accuracy and 2

  8. Vector radio-frequency optical signal generation based on one directly modulated laser

    NASA Astrophysics Data System (ADS)

    Wang, Yanyi; Xiao, Jiangnan; Chi, Nan; Yu, Jianjun

    2016-10-01

    We proposed single-sideband (SSB) quadrature phase-shift keying (QPSK) vector radio-frequency optical signal generation enabled by a single directly modulated laser without precoding technology, which can reduce the system cost and tolerate fiber dispersion. Based on our proposed scheme, we experimentally demonstrated 8-Gbaud SSB QPSK signals generation at 10 GHz, and the generated signals are transmitted over 50-km single-mode fiber without power penalty. Our experimental results show that an equal power SSB signal can tolerate fiber dispersion and have the highest receiver sensitivity.

  9. INTRINSIC SHAPE OF STAR-FORMING BzK GALAXIES. II. REST-FRAME ULTRAVIOLET AND OPTICAL STRUCTURES IN GOODS-SOUTH AND SXDS

    SciTech Connect

    Yuma, Suraphong; Ohta, Kouji; Yabe, Kiyoto

    2012-12-10

    We study the statistical intrinsic shape of star-forming BzK galaxies (sBzK galaxies) at z {approx} 2 in both rest-frame UV and rest-frame optical wavelengths. The sBzK galaxies are selected down to K{sub AB} = 24.0 mag in the GOODS-S and Subaru-XMM Deep Survey (SXDS) fields, where high-resolution images from the Hubble Space Telescope are publicly available. Of all 1028 galaxies in GOODS-S, 57% (583) show a single component in the Advanced Camera for Surveys/F850LP image. As Wide Field Camera (WFC3)/F160W images cover only part of GOODS-S and SXDS, 724/1028 and 2500/29835 sBzK galaxies in GOODS-S and SXDS, respectively, have WFC3 coverage. Of the sBzK galaxies in the WFC3/F160W images, 86% (626) and 82% (2044) appear as a single component in the GOODS-S and SXDS, respectively. A larger fraction of single-component objects in the F850LP images represents multiple star-forming regions in galaxies, while they are not so obvious in the F160W image which appears smoother. Most of the single-component sBzK galaxies show Sersic indices of n = 0.5-2.5, in agreement with those of local disk galaxies. Their effective radii are 1.0-3.0 kpc and 1.5-4.0 kpc in F850LP and F160W images, respectively, regardless of the observed fields. The stellar surface mass density of the sBzK galaxies is also comparable to that of the local disk galaxies. However, the intrinsic shape of sBzK galaxies is not a round disk as seen in the local disk galaxies. By comparing apparent axial ratio (b/a) distributions of the sBzK galaxies with those of local disk galaxies by assuming tri-axial model with axes A > B > C, we found that their intrinsic face-on B/A ratios peak at B/A = 0.70 and B/A = 0.77-0.79 in the rest-frame UV and optical, respectively, and are statistically more bar-like than those of the local disk galaxies. The intrinsic edge-on C/A ratios in both rest-frame UV and optical wavelengths peak at 0.26, which is slightly larger than those of the local disk galaxies. Possible origins of

  10. Equalizer design for clock recovery based on multi-level optical disk using signal waveform modulation

    NASA Astrophysics Data System (ADS)

    Shao, Meng; Pei, Jing; Yang, Bo

    2013-12-01

    With smaller pits and lands in multi-level optical disks using signal waveform modulation than those in DVD disks, the ISI and nonlinear attenuation of the read-out signal become more serious. One ordinary way is using an equalizer at sample rate 1/T, we proposed one method of designing the equalizer in fixed sample rate with digital interpolation. According to the analysis of the multi-level optical disk channel, we get the target frequency-response cure and implement it with seven order FIR filter. From the result of the read out experiment with multi-level optical disk, the clock of the RF signal could be recovered with the proposed equalizer.

  11. Optical encryption with protection against Dirac delta and plain signal attacks.

    PubMed

    Falaggis, Konstantinos; Ramírez Andrade, Ana Hiza; Gaxiola Luna, José Gabriel; Ojeda, Carina Gutierrez; Porras-Aguilar, Rosario

    2016-10-15

    This Letter proposes an optical encryption technique that disguises the information with modular arithmetic concepts and time-varying noise components that are unknown to the receiver. Optical encryption systems that use these techniques produce a nondeterministic system response, as well as noise like image data that can easily be generated with ordinary spatial light modulators. The principle of this technique is demonstrated for the double random phase encoding (DRPE) method. The conventional DRPE method has major vulnerabilities for Dirac signal and plain signal attacks, making them impractical for secure encryption. It is shown that the proposed encryption technique provides a robustness against these types of attacks, allowing optical DRPE to be employed in secure encryptions. Moreover, applications of this Letter are not limited to DRPE alone but can also be adopted by other optical encryption techniques such as fractional Fourier transform and Fresnel-transform-based techniques.

  12. Research on signal demodulation technology of Mach-Zehnder optical fiber sensor vibration system

    NASA Astrophysics Data System (ADS)

    Liu, Juncheng; Cheng, Pengshen; Hu, Tong

    2017-08-01

    Mach-Zehnder (M-Z) interferometer is frequently used in optical fiber vibration system. And signal demodulation technology plays an important role in the signal processing of M-Z optical fiber vibration system. In order to accurately get the phase information of the vibration signals, the signal demodulation technique based on M-Z interference principle is studied. In this paper, by analyzing the principles of 3 × 3 fiber coupler homodyne demodulation method and phase-generating carrier (PGC) technology, the advantages and disadvantages of the two demodulation methods for different vibration signal are presented. Then the method of judging signal strength is proposed. The correlation between the demodulation effects and strength of the perturbation signals is analyzed. Finally, the simulation experiments are carried out to compare the demodulation effects of the two demodulation methods, the results demonstrate that PGC demodulation technology has great advantages in weak signals, and the 3 × 3 fiber coupler is more suitable for strong signals.

  13. Kalman filtering to suppress spurious signals in Adaptive Optics control

    SciTech Connect

    Poyneer, L; Veran, J P

    2010-03-29

    In many scenarios, an Adaptive Optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.

  14. Kalman filtering to suppress spurious signals in adaptive optics control.

    PubMed

    Poyneer, Lisa A; Véran, Jean-Pierre

    2010-11-01

    In many scenarios, an adaptive optics (AO) control system operates in the presence of temporally non-white noise. We use a Kalman filter with a state space formulation that allows suppression of this colored noise, hence improving residual error over the case where the noise is assumed to be white. We demonstrate the effectiveness of this new filter in the case of the estimated Gemini Planet Imager tip-tilt environment, where there are both common-path and non-common-path vibrations. We discuss how this same framework can also be used to suppress spatial aliasing during predictive wavefront control assuming frozen flow in a low-order AO system without a spatially filtered wavefront sensor, and present experimental measurements from Altair that clearly reveal these aliased components.

  15. Advanced Silicon Microring Resonator Devices for Optical Signal Processing

    NASA Astrophysics Data System (ADS)

    Masilamani, Ashok Prabhu

    Chip level optical interconnects has gained momentum with recent demonstrations of silicon-on-insulator (SOI) based photonic modules such as lasers, modulators, wavelength division multiplexing (WDM) filters, etc. A fundamental building block that has enabled many of these silicon photonic modules is the compact, high Q factor microring resonator cavity. However, most of these demonstrations have WDM processing components based on simple add-drop filters that cannot realize the dense WDM systems required for the chip level interconnects. Dense WDM filters have stringent spectral shape requirements such as flat-top filter passband, steep band transition etc. Optical filters that can meet these specifications involve precise placement of the poles and zeros of the filter transfer function. Realization of such filters requires the use of multiple coupled microring resonators arranged in complex coupling topologies. In this thesis we have proposed and demonstrated new multiple coupled resonator topologies based on compact microring resonators in SOI material system. First we explored novel microring architectures which resulted in the proposal of two new coupled microring architectures, namely, the general 2D microring array topology and the general cascaded microring network topology. We also developed the synthesis procedures for these two microring architectures. The second part of this thesis focussed on the demonstration of the proposed architectures in the SOI material system. To accomplish this, a fabrication process for SOI was developed at the UofA Nanofab facility. Using this process, ultra-compact single microring filters with microring radii as small as 1mum were demonstrated. Higher order filter demonstration with multiple microrings necessitated post-fabrication microring resonance tuning. We developed additional fabrication steps to install micro heaters on top of the microrings to thermally tune its resonance. Subsequently, a thermally tuned fourth

  16. Quantum analysis of the nondegenerate optical parametric oscillator with injected signal

    SciTech Connect

    Coutinho dos Santos, B.; Dechoum, K.; Khoury, A.Z.; Silva, L.F. da; Olsen, M.K.

    2005-09-15

    In this paper we study the nondegenerate optical parametric oscillator with injected signal, both analytically and numerically. We develop a perturbation approach which allows us to find approximate analytical solutions, starting from the full equations of motion in the positive-P representation. We demonstrate the regimes of validity of our approximations via comparison with the full stochastic results. We find that, with reasonably low levels of injected signal, the system allows for demonstrations of quantum entanglement and the Einstein-Podolsky-Rosen paradox. In contrast to the normal optical parametric oscillator operating below threshold, these features are demonstrated with relatively intense fields.

  17. Stabilization of Phase of a Sinusoidal Signal Transmitted Over Optical Fiber

    NASA Technical Reports Server (NTRS)

    DAddario, Larry R.; Trink, Joseph T.

    2010-01-01

    In the process of connecting widely distributed antennas into a coherent array, it is necessary to synchronize the timing of signals at the various locations. This can be accomplished by distributing a common reference signal from a central source, usually over optical fiber. A high-frequency (RF or microwave) tone is a good choice for the reference. One difficulty is that the effective length of the optical fiber changes with temperature and mechanical stress, leading to phase instability in the received tone. This innovation provides a new way to stabilize the phase of the received tone, in spite of variations in the electrical length of the fiber. Stabilization is accomplished by two-way transmission in which part of the received signal is returned to the transmitting end over an identical fiber. The returned signal is detected and used to close an electrical servo loop whose effect is to keep constant the phase of the tone at the receiving end.

  18. Estimating respiratory rate from FBG optical sensors by using signal quality measurement.

    PubMed

    Yongwei Zhu; Maniyeri, Jayachandran; Fook, Victor Foo Siang; Haihong Zhang

    2015-08-01

    Non-intrusiveness is one of the advantages of in-bed optical sensor device for monitoring vital signs, including heart rate and respiratory rate. Estimating respiratory rate reliably using such sensors, however, is challenging, due to body movement, signal variation according to different subjects or body positions, etc. This paper presents a method for reliable respiratory rate estimation for FBG optical sensors by introducing signal quality estimation. The method estimates the quality of the signal waveform by detecting regularly repetitive patterns using proposed spectrum and cepstrum analysis. Multiple window sizes are used to cater for a wide range of target respiratory rates. Furthermore, the readings of multiple sensors are fused to derive a final respiratory rate. Experiments with 12 subjects and 2 body positions were conducted using polysomnography belt signal as groundtruth. The results demonstrated the effectiveness of the method.

  19. Detection of radio-frequency modulated optical signals by two and three terminal microwave devices

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Simons, R. N.; Wojtczuk, S.

    1987-01-01

    An interdigitated photoconductor (two terminal device) on GaAlAs/GaAs heterostructure was fabricated and tested by an electro-optical sampling technique. Further, the photoresponse of GaAlAs/GaAs HEMT (three terminal device) was obtained by illuminating the device with an optical signal modulated up to 8 GHz. Gain-bandwidth product, response time, and noise properties of photoconductor and HEMT devices were obtained. Monolithic integration of these photodetectors with GaAs microwave devices for optically controlled phased array antenna applications is discussed.

  20. Detection of radio-frequency modulated optical signals by two and three terminal microwave devices

    NASA Technical Reports Server (NTRS)

    Bhasin, K. B.; Simons, R. N.; Wojtczuk, S.

    1987-01-01

    An interdigitated photoconductor (two terminal device) on GaAlAs/GaAs heterostructure was fabricated and tested by an electro-optical sampling technique. Further, the photoresponse of GaAlAs/GaAs HEMT (three terminal device) was obtained by illuminating the device with an optical signal modulated up to 8 GHz. Gain-bandwidth product, response time, and noise properties of photoconductor and HEMT devices were obtained. Monolithic integration of these photodetectors with GaAs microwave devices for optically controlled phased array antenna applications is discussed.