Science.gov

Sample records for sub-band transient detection

  1. A Multiple-Channel Sub-Band Transient Detection System

    SciTech Connect

    David A. Smith

    1998-11-01

    We have developed a unique multiple-channel sub-band transient detection system to record transient electromagnetic signals in carrier-dominated radio environments; the system has been used to make unique observations of weak, transient HF signals. The detection system has made these observations possible through improved sensitivity compared to conventional broadband transient detection systems; the sensitivity improvement is estimated to be at least 20 dB. The increase in sensitivity has been achieved through subdivision of the band of interest (an 18 MHz tunable bandwidth) into eight sub-band independent detection channels, each with a 400 kHz bandwidth and its own criteria. The system generates a system trigger signal when a predetermined number of channels (typically five) trigger within a predetermined window of time (typically 100 ~s). Events are recorded with a broadband data acquisition system sampling at 50 or 100 Msample/s, so despite the fact that the detection system operates on portions of the signal confined to narrow bands, data acquisition is broadband. Between May and September of 1994, the system was used to detect and record over six thousand transient events in the frequency band from 3 to 30 MHz. Approximately 500 of the events have been characterized as paired bursts of radio noise with individual durations of 2 to 10 ps and separations between the bursts of 5 to 160 ps. The paired transients are typically 5 to 40 dB brighter than the background electromagnetic spectrum between carrier signals. We have termed these events SubIonospheric Pulse Pairs (SIPPS) and presently have no explanation as to their source. Our observations of SIPPS resemble observations of TransIonospheric Pulse Pairs (TIPPs) recorded by the Blackboard instrument on the ALEXIS satellite; the source of TIPP events is also unknown. Most of the recorded SIPP events do not exhibit frequency dispersion, implying propagation along a line-of-sight (groundwave) path; but seven of

  2. Impurity Sub-Band in Heavily Cu-Doped InAs Nanocrystal Quantum Dots Detected by Ultrafast Transient Absorption.

    PubMed

    Yang, Chunfan; Faust, Adam; Amit, Yorai; Gdor, Itay; Banin, Uri; Ruhman, Sanford

    2016-05-19

    The effect of Cu impurities on the absorption cross section, the rate of hot exction thermalization, and on exciton recombination processes in InAs quantum dots was studied by femtosecond transient absorption. Our findings reveal dynamic spectral effects of an emergent impurity sub-band near the bottom of the conduction band. Previously hypothesized to explain static photophysical properties of this system, its presence is shown to shorten hot carrier relaxation. Partial redistribution of interband oscillator strength to sub-band levels reduces the band edge bleach per exciton progressively with the degree of doping, even though the total linear absorption cross section at the band edge remains unchanged. In contrast, no doping effects were detected on absorption cross sections high in the conduction band, as expected due to the relatively high density of sates of the undoped QDs. PMID:26720008

  3. Efficient snoring and breathing detection based on sub-band spectral statistics.

    PubMed

    Sun, Xiang; Kim, Jin Young; Won, Yonggwan; Kim, Jung-Ja; Kim, Kyung-Ah

    2015-01-01

    Snoring, a common symptom in the general population may indicate the presence of obstructive sleep apnea (OSA). In order to detect snoring events in sleep sound recordings, a novel method was proposed in this paper. The proposed method operates by analyzing the acoustic characteristics of the snoring sounds. Based on these acoustic properties, the feature vectors are obtained using the mean and standard deviation of the sub-band spectral energy. A support vector machine is then applied to perform the frame-based classification procedure. This method was demonstrated experimentally to be effective for snoring detection. The database for detection included full-night audio recordings from four individuals who acknowledged having snoring habits. The performance of the proposed method was evaluated by classifying different events (snoring, breathing and silence) from the sleep sound recordings and comparing the classification against ground truth. The proposed algorithm was able to achieve an accuracy of 99.61% for detecting snoring events, 99.16% for breathing, and 99.55% for silence. PMID:26406075

  4. Detection and classification of Breast Cancer in Wavelet Sub-bands of Fractal Segmented Cancerous Zones

    PubMed Central

    Shirazinodeh, Alireza; Noubari, Hossein Ahmadi; Rabbani, Hossein; Dehnavi, Alireza Mehri

    2015-01-01

    Recent studies on wavelet transform and fractal modeling applied on mammograms for the detection of cancerous tissues indicate that microcalcifications and masses can be utilized for the study of the morphology and diagnosis of cancerous cases. It is shown that the use of fractal modeling, as applied to a given image, can clearly discern cancerous zones from noncancerous areas. In this paper, for fractal modeling, the original image is first segmented into appropriate fractal boxes followed by identifying the fractal dimension of each windowed section using a computationally efficient two-dimensional box-counting algorithm. Furthermore, using appropriate wavelet sub-bands and image Reconstruction based on modified wavelet coefficients, it is shown that it is possible to arrive at enhanced features for detection of cancerous zones. In this paper, we have attempted to benefit from the advantages of both fractals and wavelets by introducing a new algorithm. By using a new algorithm named F1W2, the original image is first segmented into appropriate fractal boxes, and the fractal dimension of each windowed section is extracted. Following from that, by applying a maximum level threshold on fractal dimensions matrix, the best-segmented boxes are selected. In the next step, the segmented Cancerous zones which are candidates are then decomposed by utilizing standard orthogonal wavelet transform and db2 wavelet in three different resolution levels, and after nullifying wavelet coefficients of the image at the first scale and low frequency band of the third scale, the modified reconstructed image is successfully utilized for detection of breast cancer regions by applying an appropriate threshold. For detection of cancerous zones, our simulations indicate the accuracy of 90.9% for masses and 88.99% for microcalcifications detection results using the F1W2 method. For classification of detected mictocalcification into benign and malignant cases, eight features are identified and

  5. Detection and classification of Breast Cancer in Wavelet Sub-bands of Fractal Segmented Cancerous Zones.

    PubMed

    Shirazinodeh, Alireza; Noubari, Hossein Ahmadi; Rabbani, Hossein; Dehnavi, Alireza Mehri

    2015-01-01

    Recent studies on wavelet transform and fractal modeling applied on mammograms for the detection of cancerous tissues indicate that microcalcifications and masses can be utilized for the study of the morphology and diagnosis of cancerous cases. It is shown that the use of fractal modeling, as applied to a given image, can clearly discern cancerous zones from noncancerous areas. In this paper, for fractal modeling, the original image is first segmented into appropriate fractal boxes followed by identifying the fractal dimension of each windowed section using a computationally efficient two-dimensional box-counting algorithm. Furthermore, using appropriate wavelet sub-bands and image Reconstruction based on modified wavelet coefficients, it is shown that it is possible to arrive at enhanced features for detection of cancerous zones. In this paper, we have attempted to benefit from the advantages of both fractals and wavelets by introducing a new algorithm. By using a new algorithm named F1W2, the original image is first segmented into appropriate fractal boxes, and the fractal dimension of each windowed section is extracted. Following from that, by applying a maximum level threshold on fractal dimensions matrix, the best-segmented boxes are selected. In the next step, the segmented Cancerous zones which are candidates are then decomposed by utilizing standard orthogonal wavelet transform and db2 wavelet in three different resolution levels, and after nullifying wavelet coefficients of the image at the first scale and low frequency band of the third scale, the modified reconstructed image is successfully utilized for detection of breast cancer regions by applying an appropriate threshold. For detection of cancerous zones, our simulations indicate the accuracy of 90.9% for masses and 88.99% for microcalcifications detection results using the F1W2 method. For classification of detected mictocalcification into benign and malignant cases, eight features are identified and

  6. ON DETECTING TRANSIENT PHENOMENA

    SciTech Connect

    Belanger, G.

    2013-08-10

    Transient phenomena are interesting and potentially highly revealing of details about the processes under observation and study that could otherwise go unnoticed. It is therefore important to maximize the sensitivity of the method used to identify such events. In this article, we present a general procedure based on the use of the likelihood function for identifying transients which is particularly suited for real-time applications because it requires no grouping or pre-processing of the data. The method makes use of all the information that is available in the data throughout the statistical decision-making process, and is suitable for a wide range of applications. Here we consider those most common in astrophysics, which involve searching for transient sources, events or features in images, time series, energy spectra, and power spectra, and demonstrate the use of the method in the case of a weak X-ray flare in a time series and a short-lived quasi-periodic oscillation in a power spectrum. We derive a fit statistic that is ideal for fitting arbitrarily shaped models to a power density distribution, which is of general interest in all applications involving periodogram analysis.

  7. Detection of transient fluorine atoms

    NASA Astrophysics Data System (ADS)

    Loge, Gary W.; Nereson, Norris; Fry, Herbert A.

    1987-09-01

    A KrF laser with a fluence of 50 mJ/cm2 was used to photolyze either uranium hexafluoride or molecular fluorine, yielding a transient number density of fluorine atoms. The rise and decay of the atomic fluorine density was observed by transient absorption of a 25-μm Pb-salt diode laser. To prevent the diode laser wavelength from drifting out of resonance with the atomic fluorine line, part of the beam was split off and sent through a microwave discharge fluorine atom cell. This allowed a wavelength modulation-feedback technique to be used to lock the diode laser wavelength onto the atomic line. The remaining diode laser beam was made collinear with the excimer laser beam using a LiF window with a 45° angle of incidence to reflect the infrared beam while transmitting most of the uv beam. Using this setup along with a transient digitizer to average between 100 and 200 transient absorption profiles, fluorine atom number densities on the order of 1014 cm-3 in a 1.7 m pathlength were detected. The signal observed were about a factor of two less than expected from known photolysis and atomic fluorine absorption cross-sections.

  8. Gaia transient detection efficiency: hunting for nuclear transients

    NASA Astrophysics Data System (ADS)

    Blagorodnova, N.; Van Velzen, S.; Harrison, D. L.; Koposov, S.; Mattila, S.; Campbell, H.; Walton, N. A.; Wyrzykowski, Ł.

    2016-01-01

    We present a study of the detectability of transient events associated with galaxies for the Gaia European Space Agency astrometric mission. We simulated the on-board detections, and on-ground processing for a mock galaxy catalogue to establish the properties required for the discovery of transient events by Gaia, specifically tidal disruption events (TDEs) and supernovae (SNe). Transients may either be discovered by the on-board detection of a new source or by the brightening of a previously known source. We show that Gaia transients can be identified as new detections on-board for offsets from the host galaxy nucleus of 0.1-0.5 arcsec, depending on magnitude and scanning angle. The Gaia detection system shows no significant loss of SNe at close radial distances to the nucleus. We used the detection efficiencies to predict the number of transients events discovered by Gaia. For a limiting magnitude of 19, we expect around 1300 SNe per year: 65 per cent SN Ia, 28 per cent SN II and 7 per cent SN Ibc, and ˜20 TDEs per year.

  9. Sub-band/transform compression of video sequences

    NASA Technical Reports Server (NTRS)

    Sauer, Ken; Bauer, Peter

    1992-01-01

    The progress on compression of video sequences is discussed. The overall goal of the research was the development of data compression algorithms for high-definition television (HDTV) sequences, but most of our research is general enough to be applicable to much more general problems. We have concentrated on coding algorithms based on both sub-band and transform approaches. Two very fundamental issues arise in designing a sub-band coder. First, the form of the signal decomposition must be chosen to yield band-pass images with characteristics favorable to efficient coding. A second basic consideration, whether coding is to be done in two or three dimensions, is the form of the coders to be applied to each sub-band. Computational simplicity is of essence. We review the first portion of the year, during which we improved and extended some of the previous grant period's results. The pyramid nonrectangular sub-band coder limited to intra-frame application is discussed. Perhaps the most critical component of the sub-band structure is the design of bandsplitting filters. We apply very simple recursive filters, which operate at alternating levels on rectangularly sampled, and quincunx sampled images. We will also cover the techniques we have studied for the coding of the resulting bandpass signals. We discuss adaptive three-dimensional coding which takes advantage of the detection algorithm developed last year. To this point, all the work on this project has been done without the benefit of motion compensation (MC). Motion compensation is included in many proposed codecs, but adds significant computational burden and hardware expense. We have sought to find a lower-cost alternative featuring a simple adaptation to motion in the form of the codec. In sequences of high spatial detail and zooming or panning, it appears that MC will likely be necessary for the proposed quality and bit rates.

  10. Concurrent detection of transient faults in microprocessors

    SciTech Connect

    Khan, M.Z.

    1989-01-01

    A large number of errors in digital systems are due to the presence of transient faults. This is especially true of microprocessor-based systems working in a radiation environment that experience transient faults due to single event upsets. These upsets cause a temporary change in the state of the system without any permanent damage. Because of their random and non-recurring nature, transient faults are difficult to detect and isolate, hence they become a source of major concern, especially in critical real-time application areas. Concurrent detection of these errors is necessary for real-time operation. Most existing fault tolerance schemes either use redundancy to mask effects of transient faults or monitor the system for abnormal operations and then perform recovery operation. Although very effective, redundancy schemes incur substantial overhead that makes them unsuitable for small systems. Most monitoring schemes, on the other hand, only detect control flow errors. A new approach called Concurrent Processor Monitoring for on-line detection of transient faults is proposed that attempts to achieve higher error coverage with small error detection latency. The concept of the execution profile of an instruction is defined and is used for detecting control flow and execution errors. To implement this scheme, a watchdog processor is designed for monitoring operations of the main processor. The effectiveness of this technique is demonstrated through computer simulations.

  11. Detection of Radio Transients from Supernovae

    NASA Astrophysics Data System (ADS)

    Schmitt, Christian

    2011-05-01

    A core-collapse supernova (SN) would produce an expanding shell of charged particles which interact with the surrounding magnetic field of the progenitor star producing a transient radio pulse. Approximately one supernova event per century is expected in a galaxy. The radio waves emitted are detectable by a new generation of low-frequency radio telescope arrays. We present details of an ongoing search for such events by the Eight-meter-wavelength Transient Array (ETA) and the Long Wavelength Array (LWA).

  12. Detectability levels for central induction transient soundings

    USGS Publications Warehouse

    Fitterman, David V.

    1989-01-01

    Using sounding curves based upon geologic models for a survey site, the latest measurement time for central induction transient soundings can be estimated for a given transmitter moment. Detectability limits are plotted on the apparent resistivity-time plots. Sounding points at earlier times than the limit are detectable, while those at later times are not. This procedure can be used during survey design to determine if features of the sounding necessary to the resolution of the geologic problem are detectable. Field measurements have shown that the method adequately predicts the latest measurement time.

  13. Detecting Thermal Cloaks via Transient Effects.

    PubMed

    Sklan, Sophia R; Bai, Xue; Li, Baowen; Zhang, Xiang

    2016-01-01

    Recent research on the development of a thermal cloak has concentrated on engineering an inhomogeneous thermal conductivity and an approximate, homogeneous volumetric heat capacity. While the perfect cloak of inhomogeneous κ and inhomogeneous ρcp is known to be exact (no signals scattering and only mean values penetrating to the cloak's interior), the sensitivity of diffusive cloaks to defects and approximations has not been analyzed. We analytically demonstrate that these approximate cloaks are detectable. Although they work as perfect cloaks in the steady-state, their transient (time-dependent) response is imperfect and a small amount of heat is scattered. This is sufficient to determine the presence of a cloak and any heat source it contains, but the material composition hidden within the cloak is not detectable in practice. To demonstrate the feasibility of this technique, we constructed a cloak with similar approximation and directly detected its presence using these transient temperature deviations outside the cloak. Due to limitations in the range of experimentally accessible volumetric specific heats, our detection scheme should allow us to find any realizable cloak, assuming a sufficiently large temperature difference. PMID:27605153

  14. Detecting Thermal Cloaks via Transient Effects

    PubMed Central

    Sklan, Sophia R.; Bai, Xue; Li, Baowen; Zhang, Xiang

    2016-01-01

    Recent research on the development of a thermal cloak has concentrated on engineering an inhomogeneous thermal conductivity and an approximate, homogeneous volumetric heat capacity. While the perfect cloak of inhomogeneous κ and inhomogeneous ρcp is known to be exact (no signals scattering and only mean values penetrating to the cloak’s interior), the sensitivity of diffusive cloaks to defects and approximations has not been analyzed. We analytically demonstrate that these approximate cloaks are detectable. Although they work as perfect cloaks in the steady-state, their transient (time-dependent) response is imperfect and a small amount of heat is scattered. This is sufficient to determine the presence of a cloak and any heat source it contains, but the material composition hidden within the cloak is not detectable in practice. To demonstrate the feasibility of this technique, we constructed a cloak with similar approximation and directly detected its presence using these transient temperature deviations outside the cloak. Due to limitations in the range of experimentally accessible volumetric specific heats, our detection scheme should allow us to find any realizable cloak, assuming a sufficiently large temperature difference. PMID:27605153

  15. Noise Reduction using Frequency Sub-Band Adaptive Spectral Subtraction

    NASA Technical Reports Server (NTRS)

    Kozel, David

    2000-01-01

    A frequency sub-band based adaptive spectral subtraction algorithm is developed to remove noise from noise-corrupted speech signals. A single microphone is used to obtain both the noise-corrupted speech and the estimate of the statistics of the noise. The statistics of the noise are estimated during time frames that do not contain speech. These statistics are used to determine if future time frames contain speech. During speech time frames, the algorithm determines which frequency sub-bands contain useful speech information and which frequency sub-bands contain only noise. The frequency sub-bands, which contain only noise, are subtracted off at a larger proportion so the noise does not compete with the speech information. Simulation results are presented.

  16. The SCEC geodetic transient detection validation exercise

    USGS Publications Warehouse

    Lohman, Rowena B.; Murray, Jessica R.

    2013-01-01

    Over the past decade the number and size of continuously operating Global Positioning System (GPS) networks has grown substantially worldwide. A steadily increasing volume of freely available GPS measurements, combined with the application of new approaches for mining these data for signals of interest, has led to the identification of a large and diverse collection of time‐varying Earth processes. One phenomenon that has been observed is transient fault slip (also termed slow slip events or silent earthquakes) occurring over time spans of days to years (e.g., Linde et al., 1996; Hirose et al., 1999; Dragert et al., 2001; Miller et al., 2002; Kostoglodov et al., 2003; Douglas et al., 2005; Shelly et al., 2006; Ide et al., 2007; Lohman and McGuire, 2007; Schwartz and Rokosky, 2007; Szeliga et al., 2008). Such events have been widely observed in subduction zones but are also found in other tectonic settings (Linde et al., 1996; Cervelli et al., 2002; Murray and Segall, 2005; Lohman and McGuire, 2007; Montgomery‐Brown et al., 2009; Shelly, 2010; and references therein). Although retrospective study of slow‐slip events using geodetic observations is driving the formulation of new models for fault‐zone behavior and constitutive laws (e.g., Lapusta et al., 2000; Liu and Rice, 2007; Lapusta and Liu, 2009; Segall and Bradley, 2012a), much of the research on near‐real‐time detection and characterization of anomalous behaviors along fault zones has focused solely on the use of seismic tremor (e.g., Rogers and Dragert, 2003; Shelly et al., 2006; Ito et al., 2007).

  17. Computationally efficient sub-band coding of ECG signals.

    PubMed

    Husøy, J H; Gjerde, T

    1996-03-01

    A data compression technique is presented for the compression of discrete time electrocardiogram (ECG) signals. The compression system is based on sub-band coding, a technique traditionally used for compressing speech and images. The sub-band coder employs quadrature mirror filter banks (QMF) with up to 32 critically sampled sub-bands. Both finite impulse response (FIR) and the more computationally efficient infinite impulse response (IIR) filter banks are considered as candidates in a complete ECG coding system. The sub-bands are threshold, quantized using uniform quantizers and run-length coded. The output of the run-length coder is further compressed by a Huffman coder. Extensive simulations indicate that 16 sub-bands are a suitable choice for this application. Furthermore, IIR filter banks are preferable due to their superiority in terms of computational efficiency. We conclude that the present scheme, which is suitable for real time implementation on a PC, can provide compression ratios between 5 and 15 without loss of clinical information. PMID:8673319

  18. Detecting Strain Transients in the Salton Trough (Invited)

    NASA Astrophysics Data System (ADS)

    McGuire, J. J.; Segall, P.; Herring, T.

    2009-12-01

    The Salton Trough region routinely experiences fault creep transients with time-scales of days to weeks, and previous studies have documented a temporal relationship between these aseimsic transients and earthquake swarms. The Plate Boundary Observatory has greatly increased the density of continuous geodetic data available in the Salton Trough, and we are analyzing this dataset to detect time periods when aseismic transients occurred in the Salton Trough. We are searching the daily GPS solutions for the time period from 2005-2009 for transients using Kalman Filter based detection algorithm called the Network Strain Filter [Ohtani, McGuire, and Segall, 2009]. The NSF solves for estimates of the secular velocity field and a time-vary transient displacement field that are expanded in basis functions. We utilize two dimensional wavelets as the basis functions. Spatial smoothing of the transient and secular velocity field are achieved by weighting the prior covariance matrix elements based on the scale of the individual wavelet basis. Site specific colored noise (seasonal terms, etc) is estimated as an random walk for each component. The vast majority of the Salton Trough GPS records are well explained by a combination of secular velocity and seasonal terms. However, we do find two spatially coherent transient episodes visible at multiple stations in the GPS data. The largest occurs near the southern extension of the Superstition Hills fault (Weinert Fault) during the second half of 2007. About 1 cm of extra motion to the northwest is observed at station P494, P496, and P497. The time scale of this transient is a few months. A second, smaller more abrupt transient is observed at stations P500 and P744 at the time of the February 2008 earthquake swarm at Cerro Prieto. We are investigating whether these two transients can be explained by slip on the Superstition Hills and Imperial faults respectively.

  19. Real-Time Detection of Optical Transients with RAPTOR

    NASA Astrophysics Data System (ADS)

    Borozdin, Konstantin N.; Brumby, Steven P.; Galassi, Mark C.; McGowan, Katherine; Starr, Daniel; Vestrand, Thomas; White, Robert; Wozniak, Przemek; Wren, James A.

    2002-12-01

    Fast variability of optical objects is an interesting though poorly explored subject in modern astronomy. Real-time data processing and identification of transient celestial events in the images is very important for such study as it allows rapid follow-up with more sensitive instruments. We discuss an approach which we have developed for the RAPTOR project, a pioneering closed-loop system combining real-time transient detection with rapid follow-up. RAPTOR's data processing pipeline is able to identify and localize an optical transient within seconds after the observation. The testing we performed so far have been confirming the effectiveness of our method for the optical transient detection. The software pipeline we have developed for RAPTOR can easily be applied to the data from other experiments.

  20. ALL TRANSIENTS, ALL THE TIME: REAL-TIME RADIO TRANSIENT DETECTION WITH INTERFEROMETRIC CLOSURE QUANTITIES

    SciTech Connect

    Law, Casey J.; Bower, Geoffrey C.

    2012-04-20

    We demonstrate a new technique for detecting radio transients based on interferometric closure quantities. The technique uses the bispectrum, the product of visibilities around a closed loop of baselines of an interferometer. The bispectrum is calibration independent, resistant to interference, and computationally efficient, so it can be built into correlators for real-time transient detection. Our technique could find celestial transients anywhere in the field of view and localize them to arcsecond precision. At the Karl G. Jansky Very Large Array (VLA), such a system would have a high survey speed and a 5{sigma} sensitivity of 38 mJy on 10 ms timescales with 1 GHz of bandwidth. The ability to localize dispersed millisecond pulses to arcsecond precision in large volumes of interferometer data has several unique science applications. Localizing individual pulses from Galactic pulsars will help find X-ray counterparts that define their physical properties, while finding host galaxies of extragalactic transients will measure the electron density of the intergalactic medium with a single dispersed pulse. Exoplanets and active stars have distinct millisecond variability that can be used to identify them and probe their magnetospheres. We use millisecond timescale visibilities from the Allen Telescope Array and VLA to show that the bispectrum can detect dispersed pulses and reject local interference. The computational and data efficiency of the bispectrum will help find transients on a range of timescales with next-generation radio interferometers.

  1. Sub-band processing for grating lobe disambiguation in sparse arrays

    NASA Astrophysics Data System (ADS)

    Hersey, Ryan K.; Culpepper, Edwin

    2014-06-01

    Combined synthetic aperture radar (SAR) and ground moving target indication (GMTI) radar modes simultaneously generate SAR and GMTI products from the same radar data. This hybrid mode provides the benefit of combined imaging and moving target displays as well as improved target recognition. However, the differing system, antenna, and waveform requirements between SAR and GMTI modes make implementing the hybrid mode challenging. The Air Force Research Laboratory (AFRL) Gotcha radar has collected wide-bandwidth, multi-channel data that can be used for both SAR and GMTI applications. The spatial channels on the Gotcha array are sparsely separated, which causes spatial grating lobes during the digital beamforming process. Grating lobes have little impact on SAR, which typically uses a single spatial channel. However, grating lobes have a large impact on GMTI, where spatial channels are used to mitigate clutter and estimate the target angle of arrival (AOA). The AOA ambiguity has a significant impact in the Gotcha data, where detections from the sidelobes and skirts of the mainlobe wrap back into the main scene causing a significant number of false alarms. This paper presents a sub-banding method to disambiguate grating lobes in the GMTI processing. This method divides the wideband SAR data into multiple frequency sub-bands. Since each sub-band has a different center frequency, the grating lobes for each sub-band appear at different angles. The method uses this variation to disambiguate target returns and places them at the correct angle of arrival (AOA). Results are presented using AFRL Gotcha radar data.

  2. Detection of Fast Transients with Radio Interferometric Arrays

    NASA Astrophysics Data System (ADS)

    Bhat, N. D. R.; Chengalur, J. N.; Cox, P. J.; Gupta, Y.; Prasad, J.; Roy, J.; Bailes, M.; Burke-Spolaor, S.; Kudale, S. S.; van Straten, W.

    2013-05-01

    Next-generation radio arrays, including the Square Kilometre Array (SKA) and its pathfinders, will open up new avenues for exciting transient science at radio wavelengths. Their innovative designs, comprising a large number of small elements, pose several challenges in digital processing and optimal observing strategies. The Giant Metre-wave Radio Telescope (GMRT) presents an excellent test-bed for developing and validating suitable observing modes and strategies for transient experiments with future arrays. Here we describe the first phase of the ongoing development of a transient detection system for GMRT that is planned to eventually function in a commensal mode with other observing programs. It capitalizes on the GMRT's interferometric and sub-array capabilities, and the versatility of a new software backend. We outline considerations in the plan and design of transient exploration programs with interferometric arrays, and describe a pilot survey that was undertaken to aid in the development of algorithms and associated analysis software. This survey was conducted at 325 and 610 MHz, and covered 360 deg2 of the sky with short dwell times. It provides large volumes of real data that can be used to test the efficacies of various algorithms and observing strategies applicable for transient detection. We present examples that illustrate the methodologies of detecting short-duration transients, including the use of sub-arrays for higher resilience to spurious events of terrestrial origin, localization of candidate events via imaging, and the use of a phased array for improved signal detection and confirmation. In addition to demonstrating applications of interferometric arrays for fast transient exploration, our efforts mark important steps in the roadmap toward SKA-era science.

  3. DETECTION OF FAST TRANSIENTS WITH RADIO INTERFEROMETRIC ARRAYS

    SciTech Connect

    Bhat, N. D. R.; Chengalur, J. N.; Gupta, Y.; Prasad, J.; Roy, J.; Kudale, S. S.; Cox, P. J.; Bailes, M.; Burke-Spolaor, S.; Van Straten, W.

    2013-05-01

    Next-generation radio arrays, including the Square Kilometre Array (SKA) and its pathfinders, will open up new avenues for exciting transient science at radio wavelengths. Their innovative designs, comprising a large number of small elements, pose several challenges in digital processing and optimal observing strategies. The Giant Metre-wave Radio Telescope (GMRT) presents an excellent test-bed for developing and validating suitable observing modes and strategies for transient experiments with future arrays. Here we describe the first phase of the ongoing development of a transient detection system for GMRT that is planned to eventually function in a commensal mode with other observing programs. It capitalizes on the GMRT's interferometric and sub-array capabilities, and the versatility of a new software backend. We outline considerations in the plan and design of transient exploration programs with interferometric arrays, and describe a pilot survey that was undertaken to aid in the development of algorithms and associated analysis software. This survey was conducted at 325 and 610 MHz, and covered 360 deg{sup 2} of the sky with short dwell times. It provides large volumes of real data that can be used to test the efficacies of various algorithms and observing strategies applicable for transient detection. We present examples that illustrate the methodologies of detecting short-duration transients, including the use of sub-arrays for higher resilience to spurious events of terrestrial origin, localization of candidate events via imaging, and the use of a phased array for improved signal detection and confirmation. In addition to demonstrating applications of interferometric arrays for fast transient exploration, our efforts mark important steps in the roadmap toward SKA-era science.

  4. Distributed control system for rapid astronomical transient detection

    NASA Astrophysics Data System (ADS)

    Wren, James A.; Borozdin, Konstantin N.; Brumby, Steven P.; Casperson, Donald E.; Galassi, Mark C.; McGowan, Katherine; Starr, Daniel; Vestrand, W. T.; White, Robert; Wozniak, Przemek

    2002-11-01

    The Rapid Telescope for Optical Response (RAPTOR) program consists of a network of robotic telescopes dedicated to the search for fast optical transients. The pilot project is composed of three observatories separated by approximately 38 kilometers located near Los Alamos, New Mexico. Each of these observatories is composed of a telescope, mount, enclosure, and weather station, all operating robotically to perform individual or coordinated transient searches. The telescopes employ rapidly slewing mounts capable of slewing a 250 pound load 180 degrees in under 2 seconds with arcsecond precision. Each telescope consists of wide-field cameras for transient detection and a narrow-field camera with greater resolution and sensitivity. The telescopes work together by employing a closed-loop system for transient detection and follow-up. Using the combined data from simultaneous observations, transient alerts are generated and distributed via the Internet. Each RAPTOR telescope also has the capability of rapidly responding to external transient alerts received over the Internet from a variety of ground-based and satellite sources. Each observatory may be controlled directly, remotely, or robotically while providing state-of-health and observational results to the client and the other RAPTOR observatories. We discuss the design and implementation of the spatially distributed RAPTOR system.

  5. An Improved Network Strain Filter for Detecting Transient Deformation Signals

    NASA Astrophysics Data System (ADS)

    Ohtani, R.; McGuire, J.; Segall, P.

    2008-12-01

    We have developed a tool to detect transient signals such as aseismic fault slip and magmatic intrusion automatically from large-scale (principally GPS) geodetic arrays, referred to as a Network Strain Filter (NSF). The NSF is capable of detecting transient signals in large data sets which may be difficult to identify by visual inspection of individual time series. The underlying principle is to exploit the spatially coherent nature of tectonic signals. The NSF models GPS displacement time series as a sum of contributions from tectonic transients, steady motion due to secular deformation, site-specific local benchmark motion, reference frame errors, and white noise. Transient deformation is represented by a spatial wavelet basis with time varying coefficients estimated using Kalman filtering techniques. A "hyperparameter" is also estimated to constrain the amount of temporal smoothness of the tectonic deformation. As station distribution is irregular and wavelets have local support (non-zero only over a localized domain), the design matrix is generally ill-conditioned. We investigate two strategies for regularizing the problem. The first is explicit spatial smoothing of the transient deformation. The second is to simply exclude wavelet bases that don't span some minimum number of stations. In this case, the smallest wavelet scale is determined such that the residual variance is consistent with the a priori errors of the data. Similarly the degree of spatial smoothing is determined by a priori knowledge of the data errors. To test the performance of the NSF, we carried out numerical tests using the southern California Integrated GPS Network (SCIGN) station distribution with synthetic transients of variable signal to noise ratio. We tested a six-year-long time series with a slow slip event with a duration of three years. Due to the long duration of the transient event, the contributions from secular motion and benchmark wobble make it difficult to identify the

  6. Real-time detection of optical transients with RAPTOR

    SciTech Connect

    Borozdin, K. N.; Brumby, Steven P.; Galassi, M. C.; McGowan, K. E.; Starr, D. L.; Vestrand, W. T.; White, R. R.; Wozniak, P. R.; Wren, J.

    2002-01-01

    Fast variability of optical objects is an interesting though poorly explored subject in modern astronomy. Real-time data processing and identification of transient, celestial events in the images is very important, for such study as it allows rapid follow-up with more sensitive instruments, We discuss an approach which we have chosen for the RAPTOR project which is a pioneering close-loop system combining real-time transient detection with rapid follow-up. Our data processing pipeline is able to identify and localize an optical transient within seconds after the observation. We describe the challenges we met, solutions we found and some results obtained in our search for fast optical transients. The software pipeline we have developed for RAPTOR can easily be applied to the data from other experiments.

  7. Ensembles of detectors for online detection of transient changes

    NASA Astrophysics Data System (ADS)

    Artemov, Alexey; Burnaev, Evgeny

    2015-12-01

    Classical change-point detection procedures assume a change-point model to be known and a change consisting in establishing a new observations regime, i.e. the change lasts infinitely long. These modeling assumptions contradicts applied problems statements. Therefore, even theoretically optimal statistics in practice very often fail when detecting transient changes online. In this work in order to overcome limitations of classical change-point detection procedures we consider approaches to constructing ensembles of change-point detectors, i.e. algorithms that use many detectors to reliably identify a change-point. We propose a learning paradigm and specific implementations of ensembles for change detection of short-term (transient) changes in observed time series. We demonstrate by means of numerical experiments that the performance of an ensemble is superior to that of the conventional change-point detection procedures.

  8. Sub-band structure engineering for advanced CMOS channels

    NASA Astrophysics Data System (ADS)

    Takagi, Shin-ichi; Mizuno, T.; Tezuka, T.; Sugiyama, N.; Nakaharai, S.; Numata, T.; Koga, J.; Uchida, K.

    2005-05-01

    This paper reviews our recent studies of novel CMOS channels based on the concept of sub-band structure engineering. This device design concept can be realized as strained-Si channel MOSFETs, ultra-thin SOI MOSFETs and Ge-on-Insulator (GOI) MOSFETs. An important factor for the electron mobility enhancement is the introduction of larger sub-band energy splitting between the 2- and 4-fold valleys on a (1 0 0) surface, which can be obtained in strained-Si and ultra-thin body channels. The electrical properties of strained-Si MOSFETs are summarized with an emphasis on strained-SOI structures. Also, the importance of the precise control of ultra-thin SOI thickness is pointed out from the experimental results of the SOI thickness dependence of mobility. Furthermore, it is shown that the increase in the sub-band energy splitting can also be effective in obtaining higher current drive of n-channel MOSFETs under ballistic transport regime. This suggests that the current drive enhancement based on MOS channel engineering utilizing strain and ultra-thin body structures can be extended to ultra-short channel MOSFETs dominated by ballistic transport.

  9. Automated transient detection in the STEREO Heliospheric Imagers.

    NASA Astrophysics Data System (ADS)

    Barnard, Luke; Scott, Chris; Owens, Mat; Lockwood, Mike; Tucker-Hood, Kim; Davies, Jackie

    2014-05-01

    Since the launch of the twin STEREO satellites, the heliospheric imagers (HI) have been used, with good results, in tracking transients of solar origin, such as Coronal Mass Ejections (CMEs), out far into the heliosphere. A frequently used approach is to build a "J-map", in which multiple elongation profiles along a constant position angle are stacked in time, building an image in which radially propagating transients form curved tracks in the J-map. From this the time-elongation profile of a solar transient can be manually identified. This is a time consuming and laborious process, and the results are subjective, depending on the skill and expertise of the investigator. Therefore, it is desirable to develop an automated algorithm for the detection and tracking of the transient features observed in HI data. This is to some extent previously covered ground, as similar problems have been encountered in the analysis of coronagraph data and have led to the development of products such as CACtus etc. We present the results of our investigation into the automated detection of solar transients observed in J-maps formed from HI data. We use edge and line detection methods to identify transients in the J-maps, and then use kinematic models of the solar transient propagation (such as the fixed-phi and harmonic mean geometric models) to estimate the solar transients properties, such as transient speed and propagation direction, from the time-elongation profile. The effectiveness of this process is assessed by comparison of our results with a set of manually identified CMEs, extracted and analysed by the Solar Storm Watch Project. Solar Storm Watch is a citizen science project in which solar transients are identified in J-maps formed from HI data and tracked multiple times by different users. This allows the calculation of a consensus time-elongation profile for each event, and therefore does not suffer from the potential subjectivity of an individual researcher tracking an

  10. Ground tests of instruments for the detection of transients

    NASA Astrophysics Data System (ADS)

    Vasilev, E. M.; Vedrenne, G.; Gernet, E. D.; Diachkov, A. V.; Zabiiakin, G. I.; Zenchenko, V. M.; Kuznetsov, A. V.; Niel, M.; Novikov, B. S.; Hurley, K.

    The goals, sequence, and results of ground tests are presented for the Sneg-2MP (Prognoz 6 and 7) and Sneg-2MZ (Venera 11 and 12) instruments designed for the detection of gamma-ray transients. Particular attention is given to autonomous tests, tests with a spacecraft simulator, noise-immunity tests, complex tests, and the computer processing of test results.

  11. Adaptive window-length detection of underwater transients using wavelets.

    PubMed

    Carevic, Dragana

    2005-05-01

    This paper describes a detection method that adapts to unknown characteristics of the underlying transient signal, such as location, length, and time-frequency content. It applies a set of embedded detectors tuned to a number of signal partitions. The detectors are based on the wavelet theory, whereby two different techniques are examined, one using local Fourier transform and the other using discrete wavelet transform. The detection statistics are computed so as to enable prewhitening of unknown colored noise and to allow for a constant false-alarm rate detection. An adapted segmentation of the signal is next obtained with a goal of finding the largest detection statistics within each segment of the partition. The detectors are tested using several underwater acoustic transient signals buried in ambient sea noise. PMID:15957761

  12. Aerostat acoustic payload for transient and helicopter detection

    NASA Astrophysics Data System (ADS)

    Scanlon, Michael; Reiff, Christian; Solomon, Latasha

    2007-04-01

    The Army Research Laboratory (ARL) has conducted experiments using acoustic sensor arrays suspended below tethered aerostats to detect and localize transient signals from mortars, artillery, and small arms fire. The airborne acoustic sensor array calculates an azimuth and elevation to the originating transient, and immediately cues a collocated imager to capture the remaining activity at the site of the acoustic transient. This single array's vector solution defines a ground-intersect region or grid coordinate for threat reporting. Unattended ground sensor (UGS) systems can augment aerostat arrays by providing additional solution vectors from several ground-based acoustic arrays to perform a 3D triangulation on a source location. The aerostat array's advantage over ground systems is that it is not as affected by diffraction and reflection from man-made structures, trees, or terrain, and has direct line-of-sight to most events.

  13. Multiple-Beam Detection of Fast Transient Radio Sources

    NASA Technical Reports Server (NTRS)

    Thompson, David R.; Wagstaff, Kiri L.; Majid, Walid A.

    2011-01-01

    A method has been designed for using multiple independent stations to discriminate fast transient radio sources from local anomalies, such as antenna noise or radio frequency interference (RFI). This can improve the sensitivity of incoherent detection for geographically separated stations such as the very long baseline array (VLBA), the future square kilometer array (SKA), or any other coincident observations by multiple separated receivers. The transients are short, broadband pulses of radio energy, often just a few milliseconds long, emitted by a variety of exotic astronomical phenomena. They generally represent rare, high-energy events making them of great scientific value. For RFI-robust adaptive detection of transients, using multiple stations, a family of algorithms has been developed. The technique exploits the fact that the separated stations constitute statistically independent samples of the target. This can be used to adaptively ignore RFI events for superior sensitivity. If the antenna signals are independent and identically distributed (IID), then RFI events are simply outlier data points that can be removed through robust estimation such as a trimmed or Winsorized estimator. The alternative "trimmed" estimator is considered, which excises the strongest n signals from the list of short-beamed intensities. Because local RFI is independent at each antenna, this interference is unlikely to occur at many antennas on the same step. Trimming the strongest signals provides robustness to RFI that can theoretically outperform even the detection performance of the same number of antennas at a single site. This algorithm requires sorting the signals at each time step and dispersion measure, an operation that is computationally tractable for existing array sizes. An alternative uses the various stations to form an ensemble estimate of the conditional density function (CDF) evaluated at each time step. Both methods outperform standard detection strategies on a test

  14. EUV sources and transients detected by the ALEXIS Satellite

    SciTech Connect

    Roussel-Dupre, D.; Pfafman, T.; Bloch, J.; Theiler, J.

    1996-12-31

    Because ALEXIS is a spinning satellite, it is an ideal platform with which to study the time variability of the EUV cosmos. The main thrusts of this effort are to (1) detect EUV sources at known and unknown locations, (2) provide notification of transients in near real time to enable immediate follow-up from other observatories, and (3) create a time history of observed sources for comparison with previously published catalogs to aid in determining long duration variability from EUV sources.

  15. Physical calibration of instruments for the detection of transients

    NASA Astrophysics Data System (ADS)

    Vedrenne, G.; Zenchenko, V. M.; Kuznetsov, A. V.; Niel, M.; Hurley, K.; Chambon, G.; Estulin, I. V.

    The present study describes the ground calibration of the Sneg-2MP (Prognoz 6) and Sneg-2MZ (Venera 11 and 12) instruments for the detection of gamma-ray transients. The basic calibration characteristics are examined including the precision of the time scale of the instrument and the determination of the energy spectrum of events. The construction of the matrix of transition to the electron spectrum is considered along with the calculation of the photon spectrum.

  16. Incipient Transient Detection in Reactor Systems: Experimental and Theoretical Investigation

    SciTech Connect

    Lefteri H. Tsoukalas; S.T. Revankar; X Wang; R. Sattuluri

    2005-09-27

    The main goal of this research was to develop a method for detecting reactor system transients at the earliest possible time through a comprehensive experimental, testing and benchmarking program. This approach holds strong promise for developing new diagnostic technologies that are non-intrusive, generic and highly portable across different systems. It will help in the design of new generation nuclear power reactors, which utilize passive safety systems with a reliable and non-intrusive multiphase flow diagnostic system to monitor the function of the passive safety systems. The main objective of this research was to develop an improved fuzzy logic based detection method based on a comprehensive experimental testing program to detect reactor transients at the earliest possible time, practically at their birth moment. A fuzzy logic and neural network based transient identification methodology and implemented in a computer code called PROTREN was considered in this research and was compared with SPRT (Sequentially Probability Ratio Testing) decision and Bayesian inference. The project involved experiment, theoretical modeling and a thermal-hydraulic code assessment. It involved graduate and undergraduate students participation providing them with exposure and training in advanced reactor concepts and safety systems. In this final report, main tasks performed during the project period are summarized and the selected results are presented. Detailed descriptions for the tasks and the results are presented in previous yearly reports (Revankar et al 2003 and Revankar et al 2004).

  17. Multiscale Transient Signal Detection: Localizing Transients in Geodetic Data Through Wavelet Transforms and Sparse Estimation Techniques

    NASA Astrophysics Data System (ADS)

    Riel, B.; Simons, M.; Agram, P.

    2012-12-01

    Transients are a class of deformation signals on the Earth's surface that can be described as non-periodic accumulation of strain in the crust. Over seismically and volcanically active regions, these signals are often challenging to detect due to noise and other modes of deformation. Geodetic datasets that provide precise measurements of surface displacement over wide areas are ideal for exploiting both the spatial and temporal coherence of transient signals. We present an extension to the Multiscale InSAR Time Series (MInTS) approach for analyzing geodetic data by combining the localization benefits of wavelet transforms (localizing signals in space) with sparse optimization techniques (localizing signals in time). Our time parameterization approach allows us to reduce geodetic time series to sparse, compressible signals with very few non-zero coefficients corresponding to transient events. We first demonstrate the temporal transient detection by analyzing GPS data over the Long Valley caldera in California and along the San Andreas fault near Parkfield, CA. For Long Valley, we are able to resolve the documented 2002-2003 uplift event with greater temporal precision. Similarly for Parkfield, we model the postseismic deformation by specific integrated basis splines characterized by timescales that are largely consistent with postseismic relaxation times. We then apply our method to ERS and Envisat InSAR datasets consisting of over 200 interferograms for Long Valley and over 100 interferograms for Parkfield. The wavelet transforms reduce the impact of spatially correlated atmospheric noise common in InSAR data since the wavelet coefficients themselves are essentially uncorrelated. The spatial density and extended temporal coverage of the InSAR data allows us to effectively localize ground deformation events in both space and time with greater precision than has been previously accomplished.

  18. Optimization of Survey Strategies for Detecting Slow Radio Transients

    NASA Astrophysics Data System (ADS)

    Macquart, Jean-Pierre

    We investigate the optimal tradeoff between sensitivity and field of view in surveys for slow radio transients using the event detection rate as the survey metric. This tradeoff bears implications for the design of surveys conducted with upcoming widefield radio interferometers, such as the ASKAP VAST survey and the MeerKAT TRAPUM survey. We investigate (i) a survey in which the events are distributed homogeneously throughout a volume centred on the Earth, (ii) a survey in which the events are homogeneously distributed, but are only detectable beyond a certain minimum distance, and (iii) a survey in which all the events occur at an identical distance, as is appropriate for a targetted survey of a particular field which subtends N point telescope pointings. For a survey of fixed duration, T obs, we determine the optimal tradeoff between number of telescope pointings, N, and integration time per field. We consider a population in which the event luminosity distribution follows a power law with index - α, and t slew is the slewing time between fields or, for a drift scan, the time taken for the telescope drift by one beamwidth. Several orders of magnitude improvement in detection rate is possible by optimization of the survey parameters. The optimal value of N for case (i) is N max ~ T obs/4t slew, while for case (iii) we find N max = (L max/L 0)2[(3 - α)/2]2/(α - 1), where L max is the maximum luminosity of a transient event and L 0 is the minimum luminosity event detectable in an integration of duration T obs. (The instance N max > N point in (iii) implies re-observation of fields over the survey area, except when the duration of transient events exceeds that between re-observations of the same field, where N max = N point applies instead.) We consider the balance in survey optimization between telescope field of view, Ω, and sensitivity, characterised by the minimum detectable flux density, S 0. For homogeneously distributed events (i), the detection rate

  19. Data-adaptive detection of transient deformation in geodetic networks

    NASA Astrophysics Data System (ADS)

    Walwer, Damian; Calais, Eric; Ghil, Michael

    2016-03-01

    The recent development of dense and continuously operating Global Navigation Satellite System (GNSS) networks worldwide has led to a significant increase in geodetic data sets that sometimes capture transient-deformation signals. It is challenging, however, to extract such transients of geophysical origin from the background noise inherent to GNSS time series and, even more so, to separate them from other signals, such as seasonal redistributions of geophysical fluid mass loads. In addition, because of the very large number of continuously recording GNSS stations now available, it has become impossible to systematically inspect each time series and visually compare them at all neighboring sites. Here we show that Multichannel Singular Spectrum Analysis (M-SSA), a method derived from the analysis of dynamical systems, can be used to extract transient deformations, seasonal oscillations, and background noise present in GNSS time series. M-SSA is a multivariate, nonparametric, statistical method that simultaneously exploits the spatial and temporal correlations of geophysical fields. The method allows for the extraction of common modes of variability, such as trends with nonconstant slopes and oscillations shared across time series, without a priori hypotheses about their spatiotemporal structure or their noise characteristics. We illustrate this method using synthetic examples and show applications to actual GPS data from Alaska to detect seasonal signals and microdeformation at the Akutan active volcano. The geophysically coherent spatiotemporal patterns of uplift and subsidence thus detected are compared to the results of an idealized model of such processes in the presence of a magma chamber source.

  20. Focal Ca2+ transient detection in smooth muscle.

    PubMed

    Young, John S; Amos, Robert J; Brain, Keith L

    2009-01-01

    Ca2+ imaging of smooth muscle provides insight into cellular mechanisms that may not result in changes of membrane potential, such as the release of Ca2+ from internal stores, and allows multiple cells to be monitored simultaneously to assess, for example, coupling in syncytial tissue. Subcellular Ca2+ transients are common in smooth muscle, yet are difficult to measure accurately because of the problems caused by their stochastic occurrence, over an often wide field of view, in an organ that it prone to contract. To overcome this problem, we've developed a series of imaging protocols and analysis routines to acquire and then analyse, in an automated fashion, the frequency, location and amplitude of such events. While this approach may be applied in other contexts, our own work involves the detection of local purinergic Ca2+ transients for locating transmitter release with submicron resolution. ATP is released as a cotransmitter from autonomic nerves, where it binds to P2X1 receptors on the smooth muscle of the detrusor and vas deferens. Ca2+ enters the smooth muscle, resulting in purinergic neuroeffector Ca2+ transients (NCTs). The focal Ca2+ transients allow the optical monitoring of neurotransmitter release in a manner that has many advantages over electrophysiology. Apart from the greatly improved spatial resolution, optical recording has the additional advantage of allowing the recording of transmitter release from many distinguishable sites simultaneously. Furthermore, the optical plane of focus is easier to maintain or correct during long recording series than is the repositioning of an intracellular sharp microelectrode. In summary, a method for imaging of Ca2+ fluorescence is outlined which details the preparation of tissue, and the acquisition and analysis of data. We outline the use of several scripts for the analysis of such Ca2+ transients. PMID:19564842

  1. Data-Adaptive Detection of Transient Deformation in GNSS Networks

    NASA Astrophysics Data System (ADS)

    Walwer, Damian; Calais, Eric; Ghil, Michael

    2015-04-01

    Transient deformation of the Earth surface are now commonly measured by dense and continuously operating GNSS networks. Such transients are however challenging to extract from the backgroung noise inherent to GNSS time series and to unravel from other geophysical signals such as seasonal oscillations caused by mass variations of the atmosphere, ocean and the hydrological reservoirs. In addition, because of the very large number of GNSS stations now available, it has become impossible to systematically inspect each time series and visually compare them at all neighboring sites. The issue is then to efficiently comb through large amounts of GNSS data to extract signals of geophysical importance. Here we show that the Multichannel Singular Spectrum Analysis (M-SSA), a method derived from the analysis of dynamical systems, can be used to automatically extract transient deformation, seasonal oscillations, and noise present in GNSS time series. The M-SSA is a multivariate non-parametric statistical method which exploit simultaneously the spatial and temporal correlations of geophysical fields. It consists in estimating Spatio-Temporal Empirical Orthogonal functions (ST-EOFs) onto which the GNSS time series can be projected and represented. It allows for the extraction of common modes of variability such as non-linear trends and oscillations shared across time series. Contrary to other methods that first clean the data assuming some a priori stochastic structure then search for transients using a library of a priori functions, the M-SSA allows for the extraction of transients without a priori hypothesis about their spatio-temporal structure or the noise characteristics of the time series. We illustrate our results using synthetic examples and show applications examples of the M-SSA to real data in Alaska and southern California to detect seasonal signals and micro-inflation/subsidence events.

  2. Direct Hydrocarbon Detection Using Multi-channel Transient Electromagnetics

    NASA Astrophysics Data System (ADS)

    Hobbs, B. A.; Ziolkowski, A. M.; Wright, D. A.

    We present a transient electromagnetic method for the detection of hydrocarbons and for monitoring their movement within a reservoir. Replacement of brine by gas or oil can cause a change in electrical resistivity of a porous rock of as much as 4 orders of magnitude. Seismic methods on the other hand are generally poor at detecting fluid content because the fluid content of a media has only a slight effect on its acoustic impedance. The data presented in this paper were collected as part of two Multi-channel Transient ElectroMagnetic (MTEM) surveys carried out in 1994 and 1996 over an underground gas storage reservoir at St. Illiers la Ville in France. The reservoir is a 30% porosity sandstone anticline about 30m thick at a depth of around 700m. In the summer gas is pumped in and the gas-water contact falls; in the winter gas is extracted and the gas- water contact rises. The position of the contact is known from constant monitoring at over 40 wells. The surveys had two objectives: first, to attempt to detect the reservoir directly from the data; second, to detect the movement of the gas water contact be- tween the 2 survey times. A recent breakthrough in the understanding of the system has allowed both these objectives to be achieved.

  3. Invisibility's Flicker: Detecting Thermal Cloaks via Transient Effects

    NASA Astrophysics Data System (ADS)

    Sklan, Sophia; Bai, Xue; Li, Baowen; Zhang, Xiang

    2015-03-01

    Recent research on the development of a thermal cloak has concentrated on engineering an inhomogeneous thermal conductivity and homogeneous volumetric heat capacity. While the perfect cloak of inhomogeneous κ and ρcp is known to be exact (no signals scattering or penetrating to the cloak's interior), no such analysis has been considered for this case. Using analytic, computational, and experimental techniques, we demonstrate that these approximate cloaks are detectable. Although they work as perfect cloaks in the steady-state, their transient (time-dependent) response is imperfect and a detectable amount of heat is scattered. This is sufficient to determine the presence of a cloak and any heat source it contains, but the material composition hidden within the cloak is not detectable in practice. Support provided by NSF GRF Grant No. 1122374.

  4. Compiler-Assisted Detection of Transient Memory Errors

    SciTech Connect

    Tavarageri, Sanket; Krishnamoorthy, Sriram; Sadayappan, Ponnuswamy

    2014-06-09

    The probability of bit flips in hardware memory systems is projected to increase significantly as memory systems continue to scale in size and complexity. Effective hardware-based error detection and correction requires that the complete data path, involving all parts of the memory system, be protected with sufficient redundancy. First, this may be costly to employ on commodity computing platforms and second, even on high-end systems, protection against multi-bit errors may be lacking. Therefore, augmenting hardware error detection schemes with software techniques is of consider- able interest. In this paper, we consider software-level mechanisms to comprehensively detect transient memory faults. We develop novel compile-time algorithms to instrument application programs with checksum computation codes so as to detect memory errors. Unlike prior approaches that employ checksums on computational and architectural state, our scheme verifies every data access and works by tracking variables as they are produced and consumed. Experimental evaluation demonstrates that the proposed comprehensive error detection solution is viable as a completely software-only scheme. We also demonstrate that with limited hardware support, overheads of error detection can be further reduced.

  5. The FORTE receiver and sub-band triggering unit

    SciTech Connect

    Enemark, D.C.; Shipley, M.E.

    1994-08-01

    The FORTE payload receiver and trigger unit represent a significant advance over the currently flying BLACKBEARD payload aboard the ALEXIS satellite. Not only is the polarization sensitive antenna array massive compared to the BLACKBEARD monopole, but the event triggering scheme is completely different. Electromagnetic pulses (EWs) are dispersed when they pass through the ionosphere creating a chirped frequency signal which can be helpful in discriminating between natural and man-made signals. Payloads designed to digitize and store the RF signatures of these signals must include sophisticated triggering circuitry to select events of interest and prevent false alarms from wasting the available memory storage resources. The FORTE wideband receiver tunes from 20 to 320 MHz with eight sub-band trigger channels distributed across the 20 MHz IF bandwidth. The conditions which must be satisfied to generate an event trigger are processor controlled. Early testing of the prototype indicates an ability to reliably trigger on chirped RF signals several dB below the noise level. FORTE is scheduled to be launched with a Pegasus XL vehicle in late 1995.

  6. Fast Transient Detection as a Prototypical ``Big Data'' Problem

    NASA Astrophysics Data System (ADS)

    Jones, Dayton L.; Wagstaff, Kiri; Thompson, David; D'Addario, Larry; Navarro, Robert; Mattmann, Chris; Majid, Walid; Rebbapragada, Umaa; Lazio, Joseph; Preston, Robert

    2012-04-01

    The detection of fast (< 1 second) transient signals requires a challenging balance between the need to examine vast quantities of high time-resolution data and the impracticality of storing all the data for later analysis. This is the epitome of a ``big data'' issue-far more data will be produced by next generation-astronomy facilities than can be analyzed, distributed, or archived using traditional methods. JPL is developing technologies to deal with ``big data'' problems from initial data generation through real-time data triage algorithms to large-scale data archiving and mining. Although most current work is focused on the needs of large radio arrays, the technologies involved are widely applicable in other areas.

  7. Detection and diagnosis of abnormal transients in nuclear power plants

    SciTech Connect

    Lee, J.C.; Rank, P.J.; Hawkes, E.; Wehe, D.K. . Dept. of Nuclear Engineering); Reifman, J. )

    1991-01-01

    This document describes a simulation-based algorithm that combines fuzzy logic with macroscopic conservation equations to diagnose multiple-failure events subject to uncertainties in transient data. Clusters of single-failure data points of similar characteristics are obtained through a pattern recognition algorithm and the cluster centers are combined in the space of macroscopic inventory derivatives to generate multiple-failure cluster centers. A fuzzy membership function is used to represent the likelihood of a data point belonging to a cluster, and failure estimates are obtained through solution of a fuzzy matrix equation. The algorithm has been successful in detecting simulated malfunctions in the pressurizer of a pressurized water reactor. 11 refs., 9 figs., 1 tab.

  8. Detection of linear impermeable barriers by transient pressure analysis

    SciTech Connect

    Martinez-Romero, N.; Cinco-Ley, H.

    1983-05-01

    This work presents a new simple method to detect a linear impermeable barrier by analysis of transient pressure data. This technique is based on the desuperposition method (negative superposition) discussed by some authors and considers the calculation the pressure change caused by the presence of the barrier. The pressure change is analyzed to estimate the distance between the well and the barrier by using the type curve matching technique. Type curves are provided for both drawdown and build tests. The advantage of the technique presented in this work is that pressure data can be analyzed even if the second semilog straight line, whose slope is twice the slope of the first semilog straight line, is not reached. Examples of application are discussed for illustration.

  9. Detecting EUV transients in near real time with ALEXIS

    SciTech Connect

    Roussel-Dupre`, D.; Bloch, J.J.; Theiler, J.; Pfafman, T.; Beauchesne, B.

    1995-12-31

    The Array of Low Energy X-ray Imaging Sensors (ALEXIS) experiment consists of a mini-satellite containing six wide angle EUV/ultrasoft X-ray telescopes (Priedhorsky et al. 1989, and Bloch et al. 1994). Its scientific objective is to map out the sky in three narrow ({Delta}E/E {approx} 5%) bandpasses around 66, 71, and 93 eV. During each 50 second satellite rotation period the six telescopes, each with a 30{degrees} field, of:view and a spatial resolution of 0.25{degrees}, scan most of the antisolar hemisphere of the sky. The project is a collaborative effort between Los Alamos National Laboratory, Sandia National Laboratory, and the University of California-Berkeley Space Sciences Laboratory. It is controlled entirely from a small ground station located at Los Alamos. The mission was launched on a Pegasus Air Launched Vehicle on April 25, 1993. An incident at launch delayed our ability to properly analyze the data until November of 1994. In January of 1995, we brought on line automated software to routinely carry out the transient search. After the data is downlinked from the satellite, the software processes and transforms it into sky maps that are automatically searched for new sources. The software then sends the results of these searches by e-mail to the science team within two hours of the downlink. This system has successfully detected the Cataclysmic Variables VW Hyi, U Gem and AR UMa in outburst, and has detected at least two unidentified short duration EUV transients (Roussel-Dupre et al 1995, Roussel-Dupre 1995).

  10. Detection of distributed damage in concrete using transient stress waves

    NASA Astrophysics Data System (ADS)

    Kesner, Keith; Sansalone, Mary; Poston, Randall W.

    1998-03-01

    Distributed damage mechanisms, such as delayed ettringite formation (DEF) and alkali-silica reactivity (ASR) can cause cracking and premature deterioration of concrete structures. The focus of the authors' research has been to determine whether transient stress waves can be used for assessing the amount of damage present in plate-like concrete sections. Results obtained from numerical, laboratory, and field studies are presented. Finite element analyses were performed to study the effects caused by distributed damage on propagation stress waves. Laboratory studies involved the use of accelerated damage specimens for performing tests for detecting changes in physical properties over time, impact-echo tests, and neutron radiography to quantify the amount of cracking present in a specimen. A correlation was made between damage predictions obtained from impact-echo signals and the actual amount of cracking as determined from radiographs. A field study on concrete box beams suffering deterioration caused by distributed damage mechanisms was performed to demonstrate the feasibility of the methods for quantifying damage in actual concrete members. These studies demonstrated that impact-echo signals can be used to detect and quantify the amount of distributed damage in concrete sections. Guidelines for determining the amount of damage using impact-echo signals are presented. For the first time, engineers have a tool for assessing the amount of damage in concrete structures with distributed cracking.

  11. Cell imaging by transient fluorescence detected infrared microscopy

    NASA Astrophysics Data System (ADS)

    Ohmori, Tsutomu; Sakai, Makoto; Ishihara, Miya; Kikuchi, Makoto; Fujii, Masaaki

    2008-02-01

    Transient fluorescence detected infrared (TFD-IR) microscopy was developed to overcome the diffraction limit of infrared (IR) light without a near-field system. This microscopic technique is based on TFD-IR spectroscopy, which converts information on IR absorption to fluorescence intensity by further electronic excitation of vibrationally excited molecules by a probing UV/visible light. Roots of Arabidopsis thaliana and living A549 cells with fluorescent dyes were chosen as samples. In the measurements using the TFD-IR microscope, tunable IR picosecond laser pulses were used in the wavelength range from 2700 to 3700 nm, corresponding to CH, NH, and OH stretching modes. Fluorescence images of the root cells of A. thaliana by the TFD-IR scheme were obtained with super-resolution compared with the resolution of conventional IR microscopy. The resolution is estimated to be less than 2.6 μm by fitting of a gaussian function. However, the TFD-IR images were dominated mainly by the fluorescent dyes because they were almost the same as a conventional fluorescence image. To investigate other contributions hidden by that of fluorescent dyes, we plotted the fluorescence intensity in several 5 μm squares at various IR wavelengths, called a TFD-IR spectrum. For root cells of A. thaliana, the TFD-IR spectra show shapes similar to those of a conventional IR absorption spectrum of the fluorescent dye. Therefore, the TFD-IR images are not due to the cellular components. For an A549 cell, the TFD-IR spectra were different from a conventional IR absorption spectrum of fluorescent dyes in the wavelength region shorter than 3100 nm. We speculate that the spectral difference is due to the cellular components, possibly assigned to the combination band related to amino groups of cellular components bonded covalently to the fluorescent dyes.

  12. Robust Filtering of Artifacts in Difference Imaging for Rapid Transients Detection

    NASA Astrophysics Data System (ADS)

    Klencki, J.; Wyrzykowski, Ł.; Kostrzewa-Rutkowska, Z.; Udalski, A.

    2016-01-01

    Real-time analysis and classification of observational data collected within synoptic sky surveys is a huge challenge due to constant growth of data volumes. Machine learning techniques are often applied in order to perform this task automatically. The current bottleneck of transients detection in most surveys is the process of filtering numerous artifacts from candidate detection. We present a new method for automated artifact filtering based on hierarchical unsupervised classifier employing Self-Organizing Maps (SOMs). The system accepts 97% of real transients and removes 97.5% of artifacts when tested on the OGLE-IV Transient Detection System. The improvement of the artifacts filtering allows for single-frame-based detection of transients within OGLE-IV, which now alerts on transient discoveries in less than 15 minutes from the image acquisition.

  13. Formation of a protected sub-band for conduction in quantum point contacts under extreme biasing

    NASA Astrophysics Data System (ADS)

    Lee, J.; Han, J. E.; Xiao, S.; Song, J.; Reno, J. L.; Bird, J. P.

    2014-02-01

    Managing energy dissipation is critical to the scaling of current microelectronics and to the development of novel devices that use quantum coherence to achieve enhanced functionality. To this end, strategies are needed to tailor the electron-phonon interaction, which is the dominant mechanism for cooling non-equilibrium (`hot') carriers. In experiments aimed at controlling the quantum state, this interaction causes decoherence that fundamentally disrupts device operation. Here, we show a contrasting behaviour, in which strong electron-phonon scattering can instead be used to generate a robust mode for electrical conduction in GaAs quantum point contacts, driven into extreme non-equilibrium by nanosecond voltage pulses. When the amplitude of these pulses is much larger than all other relevant energy scales, strong electron-phonon scattering induces an attraction between electrons in the quantum-point-contact channel, which leads to the spontaneous formation of a narrow current filament and to a renormalization of the electronic states responsible for transport. The lowest of these states coalesce to form a sub-band separated from all others by an energy gap larger than the source voltage. Evidence for this renormalization is provided by a suppression of heating-related signatures in the transient conductance, which becomes pinned near 2e2/h (e, electron charge; h, Planck constant) for a broad range of source and gate voltages. This collective non-equilibrium mode is observed over a wide range of temperature (4.2-300 K) and may provide an effective means to manage electron-phonon scattering in nanoscale devices.

  14. The nature of the longest transients detected by Swift

    NASA Astrophysics Data System (ADS)

    Starling, Rhaana

    2012-10-01

    We propose rapid XMM-Newton observations of the next exceptionally long Swift BAT triggered transient, in order to understand the nature of these anomalous systems. XMM is able to disentangle the complex spectra and track the evolution of early thermal emission at times when the sources become too faint for similar analysis with Swift XRT. These events are reshaping our view of the transient high energy Universe, and may be the first examples of Ic supernova shock breakout and rare stellar mergers. Yet to firmly establish their origins we must probe the central engines with deeper X-ray spectral coverage.

  15. Design and implementation of a hybrid sub-band acoustic echo canceller (AEC)

    NASA Astrophysics Data System (ADS)

    Bai, Mingsian R.; Yang, Cheng-Ken; Hur, Ker-Nan

    2009-04-01

    An efficient method is presented for implementing an acoustic echo canceller (AEC) that makes use of hybrid sub-band approach. The hybrid system is comprised of a fixed processor and an adaptive filter in each sub-band. The AEC aims at reducing the echo resulting from the acoustic feedback in loudspeaker-enclosure-microphone (LEM) systems such as teleconferencing and hands-free systems. In order to cancel the acoustical echo efficiently, various processing architectures including fixed filters, hybrid processors, and sub-band structure are investigated. A double-talk detector is incorporated into the proposed AEC to prevent the adaptive filter from diverging in double-talk situations. A de-correlation filter is also used alongside sub-band processing in order to enhance the performance and efficiency of AEC. All algorithms are implemented and verified on the platform of a fixed-point digital signal processor (DSP). The AECs are evaluated in terms of cancellation performance and computation complexity. In addition, listening tests are conducted to assess the subjective performance of the AECs. From the results, the proposed hybrid sub-band AEC was found to be the most effective among all methods in terms of echo reduction and timbral quality.

  16. Workshop targets development of geodetic transient detection methods: 2009 SCEC Annual Meeting: Workshop on transient anomalous strain detection; Palm Springs, California, 12-13 September 2009

    USGS Publications Warehouse

    Murray-Moraleda, Jessica R.; Lohman, Rowena

    2010-01-01

    The Southern California Earthquake Center (SCEC) is a community of researchers at institutions worldwide working to improve understanding of earthquakes and mitigate earthquake risk. One of SCEC's priority objectives is to “develop a geodetic network processing system that will detect anomalous strain transients.” Given the growing number of continuously recording geodetic networks consisting of hundreds of stations, an automated means for systematically searching data for transient signals, especially in near real time, is critical for network operations, hazard monitoring, and event response. The SCEC Transient Detection Test Exercise began in 2008 to foster an active community of researchers working on this problem, explore promising methods, and combine effective approaches in novel ways. A workshop was held in California to assess what has been learned thus far and discuss areas of focus as the project moves forward.

  17. Detecting Gravitation-Wave Transients at 5 σ : A Hierarchical Approach

    NASA Astrophysics Data System (ADS)

    Thrane, Eric; Coughlin, Michael

    2015-10-01

    As second-generation gravitational-wave detectors prepare to analyze data at unprecedented sensitivity, there is great interest in searches for unmodeled transients, commonly called bursts. Significant effort has yielded a variety of techniques to identify and characterize such transient signals, and many of these methods have been applied to produce astrophysical results using data from first-generation detectors. However, the computational cost of background estimation remains a challenging problem; it is difficult to claim a 5 σ detection with reasonable computational resources without paying for efficiency with reduced sensitivity. We demonstrate a hierarchical approach to gravitational-wave transient detection, focusing on long-lived signals, which can be used to detect transients with significance in excess of 5 σ using modest computational resources. In particular, we show how previously developed seedless clustering techniques can be applied to large data sets to identify high-significance candidates without having to trade sensitivity for speed.

  18. Detecting Gravitational-Wave Transients at 5σ: A Hierarchical Approach.

    PubMed

    Thrane, Eric; Coughlin, Michael

    2015-10-30

    As second-generation gravitational-wave detectors prepare to analyze data at unprecedented sensitivity, there is great interest in searches for unmodeled transients, commonly called bursts. Significant effort has yielded a variety of techniques to identify and characterize such transient signals, and many of these methods have been applied to produce astrophysical results using data from first-generation detectors. However, the computational cost of background estimation remains a challenging problem; it is difficult to claim a 5σ detection with reasonable computational resources without paying for efficiency with reduced sensitivity. We demonstrate a hierarchical approach to gravitational-wave transient detection, focusing on long-lived signals, which can be used to detect transients with significance in excess of 5σ using modest computational resources. In particular, we show how previously developed seedless clustering techniques can be applied to large data sets to identify high-significance candidates without having to trade sensitivity for speed. PMID:26565452

  19. Research on power-law acoustic transient signal detection based on wavelet transform

    NASA Astrophysics Data System (ADS)

    Han, Jian-hui; Yang, Ri-jie; Wang, Wei

    2007-11-01

    Aiming at the characteristics of acoustic transient signal emitted from antisubmarine weapon which is being dropped into water (torpedo, aerial sonobuoy and rocket assisted depth charge etc.), such as short duration, low SNR, abruptness and instability, based on traditional power-law detector, a new method to detect acoustic transient signal is proposed. Firstly wavelet transform is used to de-noise signal, removes random spectrum components and improves SNR. Then Power- Law detector is adopted to detect transient signal. The simulation results show the method can effectively extract envelop characteristic of transient signal on the condition of low SNR. The performance of WT-Power-Law markedly outgoes that of traditional Power-Law detection method.

  20. Video detection and analysis techniques of transient astronomical phenomena

    NASA Technical Reports Server (NTRS)

    Clifton, K. S.; Reese, R., Jr.; Davis, C. W.

    1979-01-01

    Low-light-level television systems have been utilized to gain information on meteors, aurorae, and other faint, transient astronomical phenomena. Such phenomena change not only their position as a function of time, but also their photometric and spectral characteristics in as little as 1/60 second, thus requiring unique methods of analysis. Data observed with television systems and recorded on video tape have been analyzed with a system utilizing both analog and digital techniques. Both off-the-shelf equipment and inhouse developments are used to isolate sequences of moving images and to store them in a form suitable for photometric and spectral reduction. Current emphasis of the analysis effort is directed at the measurement of the first-order emission lines of meteor spectra, the results of which will yield important compositional information concerning the nature of the impinging meteoroid.

  1. Transient signal detection using the empirical mode decomposition

    NASA Astrophysics Data System (ADS)

    Larsen, Michael L.; Ridgway, Jeffrey; Waldman, Cye H.; Gabbay, Michael; Buntzen, Rodney R.; Battista, Brad

    2004-10-01

    In this paper, we report on efforts to develop signal processing methods appropriate for the detection of man-made electromagnetic signals in the nonlinear and nonstationary underwater electromagnetic noise environment of the littoral. Using recent advances in time series analysis methods [Huang et al., 1998], we present new techniques for detection and compare their effectiveness with conventional signal processing methods, using experimental data from recent field experiments. These techniques are based on an empirical mode decomposition which is used to isolate signals to be detected from noise without a priori assumptions. The decomposition generates a physically motivated basis for the data.

  2. Transient Elastography in Clinical Detection of Liver Cirrhosis: A Systematic Review and Meta-analysis

    PubMed Central

    Geng, Xiao-Xia; Huang, Ren-Gang; Lin, Jian-Mei; Jiang, Nan; Yang, Xing-Xiang

    2016-01-01

    Background/Aims: Transient elastography is a noninvasive method for measuring liver fibrosis. This meta-analysis assesses the diagnostic performance of transient elastography of detecting liver cirrhosis in patients with liver disease. Patients and Methods: We searched MEDLINE, Cochrane, EMBASE databases until Jan 31, 2015, using the following search terms: elastography and liver cirrhosis. Included studies assessed patients with a diagnosis of liver cirrhosis, with an index test of transient elastography, and with the reference standard being a histopathological exam by liver biopsy. Sensitivity analysis and assessment of risk of bias and publication bias were performed. Results: Fifty-seven studies were included in the meta-analysis with a total of 10,504 patients. The pooled estimate for the sensitivity of transient elastography for detecting liver fibrosis was 81% and the specificity was 88%. The imputed diagnostic odds ratio (DOR) was 26.08 and the area under the receiver-operating characteristic (AUROC) curve was 0.931. Conclusion: Our findings indicate that transient elastography shows good sensitivity, specificity and a high accuracy for detecting liver cirrhosis. Transient elastography can be used as an additional method for the clinical diagnosis of liver fibrosis and cirrhosis. PMID:27488324

  3. Data-Adaptive Detection of Transient Deformation in GNSS Networks

    NASA Astrophysics Data System (ADS)

    Calais, E.; Walwer, D.; Ghil, M.

    2014-12-01

    Dense Global Navigation Satellite System (GNSS) networks have recently been developed in actively deforming regions and elsewhere. Their operation is leading to a rapidly increasing amount of data, and position time series are now routinely provided by several high-quality services. These networks often capture transient-deformation features of geophysical origin that are difficult to separate from the background noise or from seasonal residuals in the time series. In addition, because of the very large number of stations now available, it has become impossible to systematically inspect each time series and visually compare them at all neighboring sites. In order to overcome these limitations, we adapt Multichannel Singular Spectrum Analysis (M-SSA), a method derived from the analysis of dynamical systems, to the spatial and temporal analysis of GNSS position time series in dense networks. We show that this data-adaptive method — previously applied to climate, bio-medical and macro-economic indicators — allows us to extract spatio-temporal features of geophysical interest from GPS time series without a priori knowledge of the system's dynamics or of the data set's noise characteristics. We illustrate our results with examples from seasonal signals in Alaska and from micro-inflation/deflation episodes at an Aleutian-arc volcano.

  4. PERFORMANCE OF A NOVEL FAST TRANSIENTS DETECTION SYSTEM

    SciTech Connect

    Clarke, Nathan

    2013-03-01

    We investigate the signal-to-noise ratio (S/N) of a new incoherent dedispersion algorithm optimized for FPGA-based architectures intended for deployment on the Australian SKA Pathfinder and other Square Kilometre Array precursors for fast transients surveys. Unlike conventional CPU- and GPU-optimized incoherent dedispersion algorithms, this algorithm has the freedom to maximize the S/N by way of programmable dispersion profiles that enable the inclusion of different numbers of time samples per spectral channel. This allows, for example, more samples to be summed at lower frequencies where intra-channel dispersion smearing is larger, or it could even be used to optimize the dedispersion sum for steep spectrum sources. Our analysis takes into account the intrinsic pulse width, scatter broadening, spectral index and dispersion measure of the signal, and the system's frequency range, spectral and temporal resolution, and number of trial dedispersions. We show that the system achieves better than 80% of the optimal S/N where the temporal resolution and the intra-channel smearing time are smaller than a quarter of the average width of the pulse across the system's frequency band (after including scatter smearing). Coarse temporal resolutions suffer a {Delta}t {sup -1/2} decay in S/N, and coarse spectral resolutions cause a {Delta}{nu}{sup -1/2} decay in S/N, where {Delta}t and {Delta}{nu} are the temporal and spectral resolutions of the system, respectively. We show how the system's S/N compares with that of matched filter and boxcar filter detectors. We further present a new algorithm for selecting trial dispersion measures for a survey that maintains a given minimum S/N performance across a range of dispersion measures.

  5. Possible Orphan Transient Detection at PGC143111 galaxy by MASTER

    NASA Astrophysics Data System (ADS)

    Popova, E.; Lipunov, V.; Gorbovskoy, E.; Lopez, R. Rebolo; Serra-Ricart, M.; Israelian, G.; Lodieu, N.; Suarez-Andres, L.; Kornilov, V.; Tiurina, N.; Balanutsa, P.; Samus, N.; Gress, O.; Budnev, N.; Ivanov, K.; Buckley, D.; Potter, S.; Knyazev, A.; Kotze, M.; Tlatov, A.; Senik, V.; Dormidontov, D.; Krushinskiy, V.; Sergienko, Yu.; Gabovich, A.; Yurkov, V.

    2015-10-01

    MASTER-IAC auto-detection system ( Lipunov et al., Advances in Astronomy, MASTER Global Robotic Net, 2010 ) discovered OT source at (RA, Dec) = 00h 00m 08.72s -33d 41m 56.5s on 2015-10-13.98017 UT. The OT unfiltered magnitude is 17.6m (the limit is 19.9m).

  6. Detecting transient signals in geodetic time series using sparse estimation techniques

    NASA Astrophysics Data System (ADS)

    Riel, Bryan; Simons, Mark; Agram, Piyush; Zhan, Zhongwhen

    2014-06-01

    We present a new method for automatically detecting transient deformation signals from geodetic time series. We cast the detection problem as a least squares procedure where the design matrix corresponds to a highly overcomplete, nonorthogonal dictionary of displacement functions in time that resemble transient signals of various timescales. The addition of a sparsity-inducing regularization term to the cost function limits the total number of dictionary elements needed to reconstruct the signal. Sparsity-inducing regularization enhances interpretability of the resultant time-dependent model by localizing the dominant timescales and onset times of the transient signals. Transient detection can then be performed using convex optimization software where detection sensitivity is dependent on the strength of the applied sparsity-inducing regularization. To assess uncertainties associated with estimation of the dictionary coefficients, we compare solutions with those found through a Bayesian inference approach to sample the full model space for each dictionary element. In addition to providing uncertainty bounds on the coefficients and confirming the optimization results, Bayesian sampling reveals trade-offs between dictionary elements that have nearly equal probability in modeling a transient signal. Thus, we can rigorously assess the probabilities of the occurrence of transient signals and their characteristic temporal evolution. The detection algorithm is applied on several synthetic time series and real observed GPS time series for the Cascadia region. For the latter data set, we incorporate a spatial weighting scheme that self-adjusts to the local network density and filters for spatially coherent signals. The weighting allows for the automatic detection of repeating slow slip events.

  7. Spectrally resolved detection in transient-reflectivity measurements of coherent optical phonons in diamond

    NASA Astrophysics Data System (ADS)

    Nakamura, Kazutaka G.; Ohya, Kazuma; Takahashi, Hiroshi; Tsuruta, Tetsuya; Sasaki, Hiroya; Uozumi, Shin-ichi; Norimatsu, Katsura; Kitajima, Masahiro; Shikano, Yutaka; Kayanuma, Yosuke

    2016-07-01

    Coherent optical phonons in bulk solid systems play a crucial role in understanding and designing light-matter interactions and can be detected by the transient-reflectivity measurement. In this paper, we demonstrate spectrally resolved detection of coherent optical phonons in diamond from ultrashort infrared pump-probe measurements using optical bandpass filters. We show that this enhances the sensitivity approximately 35 times in measuring the coherent oscillations in the transient reflectivity compared with the commonly used spectrally integrated measurement. To explain this observation, we discuss its mechanism.

  8. Wavelet-based detection of transients in biological signals

    NASA Astrophysics Data System (ADS)

    Mzaik, Tahsin; Jagadeesh, Jogikal M.

    1994-10-01

    This paper presents two multiresolution algorithms for detection and separation of mixed signals using the wavelet transform. The first algorithm allows one to design a mother wavelet and its associated wavelet grid that guarantees the separation of signal components if information about the expected minimum signal time and frequency separation of the individual components is known. The second algorithm expands this idea to design two mother wavelets which are then combined to achieve the required separation otherwise impossible with a single wavelet. Potential applications include many biological signals such as ECG, EKG, and retinal signals.

  9. Prompt Earthquake Detection based on Transient Gravity Signals.

    NASA Astrophysics Data System (ADS)

    Juhel, K.; Montagner, J. P.; Barsuglia, M.; Ampuero, J. P.; Chassande-Mottin, E.; Harms, J.; Whiting, B. F.; Bernard, P.; Clevede, E.; Lognonne, P. H.

    2015-12-01

    The deformation caused by an earthquake induces changes in the Earth's gravitational field known as coseismic gravity changes, especially during mega-earthquakes. So far, only static gravity changes have been detected, considerably after the end of the rupture. Since gravity changes propagate at the speed of light, a dynamic gravity signal is produced everywhere on Earth during the rupture, even before the arrival of seismic waves. Here we confirm the evidence of this prompt gravity signal. We have analyzed, with a statistical blind method, the data recorded during the 2011 Mw 9.0 Tohoku-oki earthquake by a superconducting gravimeter in the underground Kamioka observatory, about 500 km away from the earthquake centroid. We find that a gravity signal is present before the P wave arrival, with a statistical significance of more than 99%. The signal amplitude is a fraction of μGal, consistent in sign and order-of-magnitude with theoretical predictions. A similar analysis is being conducted on data recorded by the broadband seismometers of the japanese network Fnet. Numerical simulations based on normal-mode method and an analytical model of dynamic gravity signals are used to compute synthetic seismograms, and thus characterize the prompt gravity signal. The robust detection of this prompt gravity signal with instruments more immune to the background seismic noise could, in principle, open new directions in earthquake seismology and overcome limitations of current earthquake early-warning systems imposed by the propagation speed of seismic waves.

  10. Swift UVOT UVW1 filter detection of a transient in the M 31 central area

    NASA Astrophysics Data System (ADS)

    Pietsch, W.; Henze, M.; Haberl, F.; Burwitz, V.

    2010-12-01

    Analyzing Swift UVOT UVW1 filter (181-321nm) observations of the central area of M 31 we detected a new bright transient at RA = 00h42m31.60s, Dec =+41d09'51.5" (J2000, accuracy of 0.5"), which is 144" west and 377" south of the core of M 31. Light curve information is given in the table below. Many UV transients in M 31 have been identified with optical novae in M 31. There is no report of a recent detection of an optical nova or a historical nova (see http://www.mpe.mpg.de/~m31novae/opt/m31/M31_table.html) for the position of the transient.

  11. Electronic Band Structure and Sub-band-gap Absorption of Nitrogen Hyperdoped Silicon

    PubMed Central

    Zhu, Zhen; Shao, Hezhu; Dong, Xiao; Li, Ning; Ning, Bo-Yuan; Ning, Xi-Jing; Zhao, Li; Zhuang, Jun

    2015-01-01

    We investigated the atomic geometry, electronic band structure, and optical absorption of nitrogen hyperdoped silicon based on first-principles calculations. The results show that all the paired nitrogen defects we studied do not introduce intermediate band, while most of single nitrogen defects can introduce intermediate band in the gap. Considering the stability of the single defects and the rapid resolidification following the laser melting process in our sample preparation method, we conclude that the substitutional nitrogen defect, whose fraction was tiny and could be neglected before, should have considerable fraction in the hyperdoped silicon and results in the visible sub-band-gap absorption as observed in the experiment. Furthermore, our calculations show that the substitutional nitrogen defect has good stability, which could be one of the reasons why the sub-band-gap absorptance remains almost unchanged after annealing. PMID:26012369

  12. DETECTION RATES FOR SURVEYS FOR FAST TRANSIENTS WITH NEXT GENERATION RADIO ARRAYS

    SciTech Connect

    Macquart, Jean-Pierre

    2011-06-10

    We relate the underlying properties of a population of fast radio-emitting transient events to its expected detection rate in a survey of finite sensitivity. The distribution of the distances of the detected events is determined in terms of the population luminosity distribution and survey parameters, for both extragalactic and Galactic populations. The detection rate as a function of Galactic position is examined to identify regions that optimize survey efficiency in a survey whose field of view is limited. The impact of temporal smearing caused by scattering in the interstellar medium has a large and direction-dependent bearing on the detection of impulsive signals, and we present a model for the effects of scattering on the detection rate. We show that the detection rate scales as {Omega}S{sup -3/2+{delta}}{sub 0}, where {Omega} is the field of view, S{sub 0} is the minimum detectable flux density, and 0 < {delta} {<=} 3/2 for a survey of Galactic transients in which interstellar scattering or the finite volume of the Galaxy is important. We derive formal conditions on the optimal survey strategy to adopt under different circumstances for fast transient surveys on next generation large-element, wide-field arrays, such as ASKAP, LOFAR, the MWA, and the SKA, and show how interstellar scattering and the finite spatial extent of a Galactic population modify the choice of optimal strategy.

  13. INTEGRAL detection of a hard X-ray transient in NGC 6440

    NASA Astrophysics Data System (ADS)

    Kuulkers, E.; Bozzo, E.; Bazzano, A.; Beckmann, V.; Bird, T.; Bodaghee, A.; Chenevez, J.; Del Santo, M.; Domingo, A.; Jonker, P.; Kretschmar, P.; Paizis, A.; Pottschmidt, K.; Markwardt, C.; Sanchez-Fernandez, C.; Wijnands, R.

    2015-02-01

    During INTEGRAL Galactic bulge monitoring (e.g., ATel #438) observations performed on UT 2015 February 17 at 12.53-16:45, IBIS/ISGRI detected renewed activity at hard X-rays from a transient within the Globular Cluster NGC 6440.

  14. Parallel contact detection algorithm for transient solid dynamics simulations using PRONTO3D

    SciTech Connect

    Attaway, S.W.; Hendrickson, B.A.; Plimpton, S.J.

    1996-09-01

    An efficient, scalable, parallel algorithm for treating material surface contacts in solid mechanics finite element programs has been implemented in a modular way for MIMD parallel computers. The serial contact detection algorithm that was developed previously for the transient dynamics finite element code PRONTO3D has been extended for use in parallel computation by devising a dynamic (adaptive) processor load balancing scheme.

  15. Semi-Supervised Novelty Detection with Adaptive Eigenbases, and Application to Radio Transients

    NASA Technical Reports Server (NTRS)

    Thompson, David R.; Majid, Walid A.; Reed, Colorado J.; Wagstaff, Kiri L.

    2011-01-01

    We present a semi-supervised online method for novelty detection and evaluate its performance for radio astronomy time series data. Our approach uses adaptive eigenbases to combine 1) prior knowledge about uninteresting signals with 2) online estimation of the current data properties to enable highly sensitive and precise detection of novel signals. We apply the method to the problem of detecting fast transient radio anomalies and compare it to current alternative algorithms. Tests based on observations from the Parkes Multibeam Survey show both effective detection of interesting rare events and robustness to known false alarm anomalies.

  16. An analog cell to detect single event transients in voltage references

    NASA Astrophysics Data System (ADS)

    Franco, F. J.; Palomar, C.; Izquierdo, J. G.; Agapito, J. A.

    2015-01-01

    A reliable voltage reference is mandatory in mixed-signal systems. However, this family of components can undergo very long single event transients when operating in radiation environments such as space and nuclear facilities due to the impact of heavy ions. The purpose of the present paper is to demonstrate how a simple cell can be used to detect these transients. The cell was implemented with typical COTS components and its behavior was verified by SPICE simulations and in a laser facility. Different applications of the cell are explored as well.

  17. Inferential statistics for transient signal detection in radio astronomy phased arrays

    NASA Astrophysics Data System (ADS)

    Schmid, Natalia A.; Prestage, Richard M.; Alkhweldi, Marwan

    2015-05-01

    In this paper we develop two statistical rules for the purpose of detecting pulsars and transients using signals from phased array feeds installed on a radio telescope in place of a traditional horn receiver. We assume a known response of the antenna arrays and known coupling among array elements. We briefly summarize a set of pre-processing steps applied to raw array data prior to signal detection and then derive two detection statistics assuming two models for the unknown radio source astronomical signal: (1) the signal is deterministic and (2) the signal is a random process. The performance of both detectors is analyzed using both real and simulated data.

  18. An image sensor capable of detecting nano-ampere transient signals with strong background illumination

    SciTech Connect

    Chu, D.D.; Dixon, D.A.; Thelen, D.C. Jr.

    1995-10-01

    A readout detector integrated circuit (IC) has been developed which is capable of detecting nano-ampere photo-current signals of interest in a high (micro-ampere) background illumination or DC noise level (SNR=92dB). The readout detector sensor IC processes transient signals of interest from a separate photodiode array chip. Low noise signal conditioning, filtering, and signal thresholding implement smart sensor detection of only ``active pixels.`` This detector circuit can also be used to perform signal conditioning for other sensor applications that require detection of very small signals in a high background noise environment.

  19. X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu.

    PubMed

    Kukreja, R; Bonetti, S; Chen, Z; Backes, D; Acremann, Y; Katine, J A; Kent, A D; Dürr, H A; Ohldag, H; Stöhr, J

    2015-08-28

    We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3×10^{-5}μ_{B} on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott's two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4×10^{-3}μ_{B} per atom. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow. PMID:26371670

  20. X-ray Detection of Transient Magnetic Moments Induced by a Spin Current in Cu

    NASA Astrophysics Data System (ADS)

    Kukreja, R.; Bonetti, S.; Chen, Z.; Backes, D.; Acremann, Y.; Katine, J. A.; Kent, A. D.; Dürr, H. A.; Ohldag, H.; Stöhr, J.

    2015-08-01

    We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3 ×10-5μB on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott's two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4 ×10-3μB per atom. This reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.

  1. X-ray detection of transient magnetic moments induced by a spin current in Cu

    SciTech Connect

    Kukreja, R.; Bonetti, S.; Chen, Z.; Backes, D.; Acremann, Y.; Katine, J.; Kent, A. D.; Durr, H. A.; Ohldag, H.; Stohr, J.

    2015-08-24

    We have used a MHz lock-in x-ray spectromicroscopy technique to directly detect changes in magnetic moment of Cu due to spin injection from an adjacent Co layer. The elemental and chemical specificity of x rays allows us to distinguish two spin current induced effects. We detect the creation of transient magnetic moments of 3×10–5μB on Cu atoms within the bulk of the 28 nm thick Cu film due to spin accumulation. The moment value is compared to predictions by Mott’s two current model. We also observe that the hybridization induced existing magnetic moments at the Cu interface atoms are transiently increased by about 10% or 4×10–3μB per atom. As a result, this reveals the dominance of spin-torque alignment over Joule heat induced disorder of the interfacial Cu moments during current flow.

  2. Real-time calibration of the AARTFAAC array for transient detection

    NASA Astrophysics Data System (ADS)

    Prasad, P.; Wijnholds, S. J.; Huizinga, F.; Wijers, R. A. M. J.

    2014-08-01

    The search for transient phenomena at low radio frequencies is now coming of age with the development of radio sky monitors with a large field of view, which are made feasible by new developments in calibration algorithms and computing. However, accurate calibration of such arrays is challenging, especially within the latency requirements of near real-time transient monitors, and is the main cause of limiting their sensitivities. This paper describes a strategy for real-time, wide-field direction-dependent calibration of the Amsterdam-ASTRON Radio Transients Facility and Analysis Center (AARTFAAC) array, which is a sensitive, continuously available all-sky monitor based on the LOw Frequency ARray (LOFAR). The monitor operates in a zenith pointing, snapshot imaging mode for image plane detection of bright radio transients. We show that a tracking calibration approach with solution propagation satisfies our latency, computing, and calibration accuracy constraints. We characterize the instrument and verify the calibration strategy under a variety of observing conditions. This brings out several phenomena, which can bias the calibration. The real-time nature of the application further imposes strict latency and computational constraints. We find that although ionosphere-induced phase errors present a major impediment to accurate calibration, these can be corrected in the direction of the brightest few sources to significantly improve image quality. Our real-time calibration pipeline implementation processes a single spectral channel of a snapshot observation in ~0.2 s on test hardware, which is well within its latency budget. Autonomously calibrating and imaging one second snapshots, our approach leads to a typical image noise of ~10 Jy for a ~90 kHz channel, reaching dynamic ranges of ~2000:1. We also show that difference imaging allows thermal-noise limited transient detection, despite the instrument being confusion-noise limited.

  3. Improving solar cell efficiencies by up-conversion of sub-band-gap light

    NASA Astrophysics Data System (ADS)

    Trupke, T.; Green, M. A.; Würfel, P.

    2002-10-01

    A system for solar energy conversion using the up-conversion of sub-band-gap photons to increase the maximum efficiency of a single-junction conventional, bifacial solar cell is discussed. An up-converter is located behind a solar cell and absorbs transmitted sub-band-gap photons via sequential ground state absorption/excited state absorption processes in a three-level system. This generates an excited state in the up-converter from which photons are emitted which are subsequently absorbed in the solar cell and generate electron-hole pairs. The solar energy conversion efficiency of this system in the radiative limit is calculated for different cell geometries and different illumination conditions using a detailed balance model. It is shown that in contrast to an impurity photovoltaic solar cell the conditions of photon selectivity and of complete absorption of high-energy photons can be met simultaneously in this system by restricting the widths of the bands in the up-converter. The upper limit of the energy conversion efficiency of the system is found to be 63.2% for concentrated sunlight and 47.6% for nonconcentrated sunlight.

  4. DETECTION OF FAST RADIO TRANSIENTS WITH MULTIPLE STATIONS: A CASE STUDY USING THE VERY LONG BASELINE ARRAY

    SciTech Connect

    Thompson, David R.; Wagstaff, Kiri L.; Majid, Walid A.; Brisken, Walter F.; Deller, Adam T.; Tingay, Steven J.; Wayth, Randall B.

    2011-07-10

    Recent investigations reveal an important new class of transient radio phenomena that occur on submillisecond timescales. Often, transient surveys' data volumes are too large to archive exhaustively. Instead, an online automatic system must excise impulsive interference and detect candidate events in real time. This work presents a case study using data from multiple geographically distributed stations to perform simultaneous interference excision and transient detection. We present several algorithms that incorporate dedispersed data from multiple sites, and report experiments with a commensal real-time transient detection system on the Very Long Baseline Array. We test the system using observations of pulsar B0329+54. The multiple-station algorithms enhanced sensitivity for detection of individual pulses. These strategies could improve detection performance for a future generation of geographically distributed arrays such as the Australian Square Kilometre Array Pathfinder and the Square Kilometre Array.

  5. Detection of Fast Radio Transients with Multiple Stations: A Case Study Using the Very Long Baseline Array

    NASA Astrophysics Data System (ADS)

    Thompson, David R.; Wagstaff, Kiri L.; Brisken, Walter F.; Deller, Adam T.; Majid, Walid A.; Tingay, Steven J.; Wayth, Randall B.

    2011-07-01

    Recent investigations reveal an important new class of transient radio phenomena that occur on submillisecond timescales. Often, transient surveys' data volumes are too large to archive exhaustively. Instead, an online automatic system must excise impulsive interference and detect candidate events in real time. This work presents a case study using data from multiple geographically distributed stations to perform simultaneous interference excision and transient detection. We present several algorithms that incorporate dedispersed data from multiple sites, and report experiments with a commensal real-time transient detection system on the Very Long Baseline Array. We test the system using observations of pulsar B0329+54. The multiple-station algorithms enhanced sensitivity for detection of individual pulses. These strategies could improve detection performance for a future generation of geographically distributed arrays such as the Australian Square Kilometre Array Pathfinder and the Square Kilometre Array.

  6. Detection and characterization of transient forcing episodes affecting earthquake activity in the Aleutian Arc system

    NASA Astrophysics Data System (ADS)

    Reverso, T.; Marsan, D.; Helmstetter, A.

    2015-02-01

    Crustal, slow deformation transients can be caused by fluid or magmatic intrusions, and by slow slip on faults. They can affect earthquake dynamics, if they occur close to or within seismically active zones. We here further develop, and test, a statistical method for detecting and characterizing seismicity anomalies that is only based on earthquake occurrence times and locations. We make use of this method to analyze the 2004-2013 seismicity at mc = 3.5 in the Aleutian subduction system, to find six statistically significant anomalies, with typical 1 day duration and 30 to 50 km size, that are likely related to slow deformation transients. They tend to be located in zones characterized by intermediate seismic coupling, and to mark the termination of past large to mega-thrust earthquakes. These anomalies account for a non-negligible (9%) part of the total activity, proving that non-stationary aseismic loading plays an important role in the dynamics of crustal deformation.

  7. Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques

    NASA Astrophysics Data System (ADS)

    Limaye, Mukta V.; Chen, S. C.; Lee, C. Y.; Chen, L. Y.; Singh, Shashi B.; Shao, Y. C.; Wang, Y. F.; Hsieh, S. H.; Hsueh, H. C.; Chiou, J. W.; Chen, C. H.; Jang, L. Y.; Cheng, C. L.; Pong, W. F.; Hu, Y. F.

    2015-06-01

    The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2- (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2- species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2-, n > 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples.

  8. Chromatic dispersion mitigation in long-haul fiber-optic communication networks by sub-band partitioning.

    PubMed

    Malekiha, Mahdi; Tselniker, Igor; Plant, David V

    2015-12-14

    We propose and experimentally demonstrate a novel sub-band multiplexed data architecture for chromatic dispersion (CD) mitigation. We have demonstrated 32 GBaud multi-sub-band (MSB) dual-polarization (DP) 16QAM transmission over 2400 km. Using this approach, the transmitted signal bandwidth is divided into multiple narrow-bandwidth sub-bands, each operating at a lower baud rate. Within each sub-band bandwidth, the CD frequency response can be approximated as a linear-phase band-pass filter, which can be considered as an analog delay that does not require compensation. Therefore, the resulting receiver digital signal processing (DSP) is simplified due to the removal of the CD compensation equalizer. In addition, this leads to efficient parallelization of DSP tasks by deploying multiple independent sub-band processors running at a lower clock rate. The proposed system reduces receiver computational complexity and offers 1 dB higher Kerr-nonlinearity tolerance and 2% extended transmission reach in comparison to the conventional single carrier systems. PMID:26699054

  9. Excitation, Ionization, and Desorption: How Sub-band gap Photons Modify the Structure of Oxide Nanoparticles

    SciTech Connect

    Trevisanutto, P. E.; Sushko, Petr V.; Beck, Kenneth M.; Joly, Alan G.; Hess, Wayne P.; Shluger, Alexander L.

    2009-01-29

    Nanoparticles of wide-band-gap materials MgO and CaO, subjected to low-intensity ultraviolet irradiation with 266 nm (4.66 eV) photons, emit hyperthermal oxygen atoms with kinetic energies up to ~ 0.4 eV. We use ab initio embedded cluster methods to study theoretically a variety of elementary photoinduced processes at both ideal and defect-containing surfaces of these nanoparticles and develop a mechanism for the desorption process. The proposed mechanism includes multiple local photoexcitations resulting in sequential formation of localized excitons, their ionization, and further excitations. It is suggested that judicious choice of sub-band-gap photon energies can be used to selectively modify surfaces of nanomaterials.

  10. Study of sub band gap absorption of Sn doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Rani, Mamta; Tripathi, S. K.

    2014-04-01

    The nanocrystalline thin films of Sn doped CdSe at different dopants concentration are prepared by thermal evaporation technique on glass substrate at room temperature. The effect of Sn doping on the optical properties of CdSe has been studied. A decrease in band gap value is observed with increase in Sn concentration. Constant photocurrent method (CPM) is used to study the absorption coefficient in the sub band gap region. Urbach energy has been obtained from CPM spectra which are found to increase with amount of Sn dopants. The refractive index data calculated from transmittance is used for the identification of oscillator strength and oscillator energy using single oscillator model which is found to be 7.7 and 2.12 eV, 6.7 and 2.5 eV for CdSe:Sn 1% and CdSe:Sn 5% respectively.

  11. Study of sub band gap absorption of Sn doped CdSe thin films

    SciTech Connect

    Kaur, Jagdish; Rani, Mamta; Tripathi, S. K.

    2014-04-24

    The nanocrystalline thin films of Sn doped CdSe at different dopants concentration are prepared by thermal evaporation technique on glass substrate at room temperature. The effect of Sn doping on the optical properties of CdSe has been studied. A decrease in band gap value is observed with increase in Sn concentration. Constant photocurrent method (CPM) is used to study the absorption coefficient in the sub band gap region. Urbach energy has been obtained from CPM spectra which are found to increase with amount of Sn dopants. The refractive index data calculated from transmittance is used for the identification of oscillator strength and oscillator energy using single oscillator model which is found to be 7.7 and 2.12 eV, 6.7 and 2.5 eV for CdSe:Sn 1% and CdSe:Sn 5% respectively.

  12. Transient dynamics simulations: Parallel algorithms for contact detection and smoothed particle hydrodynamics

    SciTech Connect

    Hendrickson, B.; Plimpton, S.; Attaway, S.; Swegle, J.

    1996-09-01

    Transient dynamics simulations are commonly used to model phenomena such as car crashes, underwater explosions, and the response of shipping containers to high-speed impacts. Physical objects in such a simulation are typically represented by Lagrangian meshes because the meshes can move and deform with the objects as they undergo stress. Fluids (gasoline, water) or fluid-like materials (earth) in the simulation can be modeled using the techniques of smoothed particle hydrodynamics. Implementing a hybrid mesh/particle model on a massively parallel computer poses several difficult challenges. One challenge is to simultaneously parallelize and load-balance both the mesh and particle portions of the computation. A second challenge is to efficiently detect the contacts that occur within the deforming mesh and between mesh elements and particles as the simulation proceeds. These contacts impart forces to the mesh elements and particles which must be computed at each timestep to accurately capture the physics of interest. In this paper we describe new parallel algorithms for smoothed particle hydrodynamics and contact detection which turn out to have several key features in common. Additionally, we describe how to join the new algorithms with traditional parallel finite element techniques to create an integrated particle/mesh transient dynamics simulation. Our approach to this problem differs from previous work in that we use three different parallel decompositions, a static one for the finite element analysis and dynamic ones for particles and for contact detection. We have implemented our ideas in a parallel version of the transient dynamics code PRONTO-3D and present results for the code running on a large Intel Paragon.

  13. Method for detecting moment connection fracture using high-frequency transients in recorded accelerations

    USGS Publications Warehouse

    Rodgers, J.E.; Elebi, M.

    2011-01-01

    The 1994 Northridge earthquake caused brittle fractures in steel moment frame building connections, despite causing little visible building damage in most cases. Future strong earthquakes are likely to cause similar damage to the many un-retrofitted pre-Northridge buildings in the western US and elsewhere. Without obvious permanent building deformation, costly intrusive inspections are currently the only way to determine if major fracture damage that compromises building safety has occurred. Building instrumentation has the potential to provide engineers and owners with timely information on fracture occurrence. Structural dynamics theory predicts and scale model experiments have demonstrated that sudden, large changes in structure properties caused by moment connection fractures will cause transient dynamic response. A method is proposed for detecting the building-wide level of connection fracture damage, based on observing high-frequency, fracture-induced transient dynamic responses in strong motion accelerograms. High-frequency transients are short (<1 s), sudden-onset waveforms with frequency content above 25 Hz that are visually apparent in recorded accelerations. Strong motion data and damage information from intrusive inspections collected from 24 sparsely instrumented buildings following the 1994 Northridge earthquake are used to evaluate the proposed method. The method's overall success rate for this data set is 67%, but this rate varies significantly with damage level. The method performs reasonably well in detecting significant fracture damage and in identifying cases with no damage, but fails in cases with few fractures. Combining the method with other damage indicators and removing records with excessive noise improves the ability to detect the level of damage. ?? 2010 Elsevier B.V. All rights reserved.

  14. Modified variance ratio for objective detection of transient evoked potentials in bottlenose dolphins (Tursiops truncatus).

    PubMed

    Finneran, James J

    2008-12-01

    Evoked potential studies have often relied on one or more human observers to visually assess the averaged waveforms and decide if a response is present. Although simple and easy to implement, response detection strategies based on human observers are inherently subjective and depend on the observers' experience and biases. To avoid these shortcomings, some recent marine animal studies utilizing auditory steady-state responses have applied frequency-domain, statistically based objective detection methods; however, statistically based objective methods have not yet been applied to marine animal tests involving transient evoked responses, which are normally analyzed in the time domain. The present study applied a modified version of the variance ratio F(SP) to determine the presence or absence of evoked responses in two bottlenose dolphins (Tursiops truncatus) stimulated with tone pips. The appropriate degrees of freedom for the statistical tests were empirically determined in four dolphins. The modified variance ratio was found to be a useful tool and to provide an objective statistical approach for the detection of transient evoked potentials. PMID:19206829

  15. MASTER Detection of an Optical Transient in the Error Box of GRB 150128

    NASA Astrophysics Data System (ADS)

    Shumkov, V.; Denisenko, D.; Lipunov, V.; Gorbovskoy, E.; Balanutsa, P.; Kornilov, V.; Tiurina, N.; Kuznetsov, A.; Vladimirov, V.; Ivanov, K.; Gres, O.; Yazev, S.; Budnev, N.; Poleshchuk, V.; Konstantinov, E.; Tlatov, A.; Dormidontov, D.; Senik, V.; Yurkov, A. Parkhomenko V.; Sergienko, Y.; Gabovich, A.; Krushinsky, V.; Zalozhnih, I.; Popov, A.; Bourdanov, A.; Buckley, D.; Potter, S.; Kniazev, A.; Kotze, M.; Shurpakov, S.

    2015-01-01

    MASTER OT J180153.15+254323.5 - optical transient in the error box of GRB 150128 During the inspection of the error box of a long (more than 60 sec) multi-peak gamma-ray burst GRB 150128 (Fermi trigger 444164357, INTEGRAL SPI-ACS trigger 6874) MASTER-Tunka auto-detection system discovered OT source at (RA, Dec) = 18h 01m 53.15s +25d 43m 23.5s on 2015-01-28.91546 UT (O.

  16. MAXI/GSC detects an X-ray transient MAXI J1409-619

    NASA Astrophysics Data System (ADS)

    Yamaoka, K.; Nakahira, S.; Negoro, H.; Kawai, N.; Uzawa, A.; Yamazaki, K.; Matsumura, T.; Tsuboi, Y.; Kawasaki, K.; Ueno, S.; Tomida, H.; Kohama, M.; Ishikawa, M.; Mihara, T.; Sugizaki, M.; Serino, M.; Nakagawa, Y. E.; Yamamoto, T.; Sootome, T.; Matsuoka, M.; Morii, M.; Sugimori, K.; Usui, R.; Yoshida, A.; Tsunemi, H.; Kimura, M.; Nakajima, M.; Ozawa, H.; Suwa, F.; Ueda, Y.; Isobe, N.; Eguchi, S.; Hiroi, K.; Daikyuji, A.; Maxi Team

    2010-10-01

    The MAXI/GSC has detected a faint X-ray transient source at a position: (R.A., Dec) = (212.26, -61.95) = (14h09m02s.4, -61d57m00s.0) (J2000) with a statistical error of about 0.2 degrees. The systematic error is smaller because the position is calibrated using nearby bright sources 4U 1323-60 and 4U 1254-69. The 4-10 keV flux reached a peak at 41 +/- 7 mCrab on October 17, then decreased to 29 +/- 7 mCrab on October 18.

  17. Development of a transient expression assay for detecting environmental oestrogens in zebrafish and medaka embryos

    PubMed Central

    2012-01-01

    Background Oestrogenic contaminants are widespread in the aquatic environment and have been shown to induce adverse effects in both wildlife (most notably in fish) and humans, raising international concern. Available detecting and testing systems are limited in their capacity to elucidate oestrogen signalling pathways and physiological impacts. Here we developed a transient expression assay to investigate the effects of oestrogenic chemicals in fish early life stages and to identify target organs for oestrogenic effects. To enhance the response sensitivity to oestrogen, we adopted the use of multiple tandem oestrogen responsive elements (EREc38) in a Tol2 transposon mediated Gal4ff-UAS system. The plasmid constructed (pTol2_ERE-TATA-Gal4ff), contains three copies of oestrogen response elements (3ERE) that on exposure to oestrogen induces expression of Gal4ff which this in turn binds Gal4-responsive Upstream Activated Sequence (UAS) elements, driving the expression of a second reporter gene, EGFP (Enhanced Green Fluorescent Protein). Results The response of our construct to oestrogen exposure in zebrafish embryos was examined using a transient expression assay. The two plasmids were injected into 1–2 cell staged zebrafish embryos, and the embryos were exposed to various oestrogens including the natural steroid oestrogen 17ß-oestradiol (E2), the synthetic oestrogen 17α- ethinyloestradiol (EE2), and the relatively weak environmental oestrogen nonylphenol (NP), and GFP expression was examined in the subsequent embryos using fluorescent microscopy. There was no GFP expression detected in unexposed embryos, but specific and mosaic expression of GFP was detected in the liver, heart, somite muscle and some other tissue cells for exposures to steroid oestrogen treatments (EE2; 10 ng/L, E2; 100 ng/L, after 72 h exposures). For the NP exposures, GFP expression was observed at 10 μg NP/L after 72 h (100 μg NP/L was toxic to the fish). We also demonstrate that

  18. Swift/XRT detection of another active X-ray transient close to Sgr A*

    NASA Astrophysics Data System (ADS)

    Degenaar, N.; Reynolds, M. T.; Wijnands, R.; Miller, J. M.; Kennea, J. A.; Ponti, G.; Haggard, D.; Gehrels, N.

    2016-06-01

    Daily monitoring observations of the Galactic center performed with the Swift/XRT (Degenaar et al. 2015) have revealed activity of a new X-ray transient located ~10" South of Sgr A*. This object is clearly detected during three consecutive ~0.9 ks PC mode observations performed on 2016 May 28 and 30, and June 1. The 0.3-10 keV count rate has risen from ~2E-2 to ~0.1 counts/s between those observations.

  19. Transient absorption spectroscopy detection of sensitized delayed fluorescence in chiral benzophenone/naphthalene systems

    NASA Astrophysics Data System (ADS)

    Bonancía, Paula; Jiménez, M. Consuelo; Miranda, Miguel A.

    2011-10-01

    Transient absorption spectroscopy has proven to be a powerful tool to investigate the formation and decay of excited singlet states upon triplet-triplet annihilation, following T-T energy transfer from a selectively excited sensitizer. Thus, upon selective excitation of benzophenone (BZP) by laser flash photolysis (LFP) at λ = 355 nm in the presence of naphthalene (NPT), a negative band centered at 340 nm has been detected, with growth and decay in the microsecond timescale. It has been assigned to the P-type NPT delayed-fluorescence. In the case of chiral BZP/NPT systems, stereodifferentiation has been observed in the kinetics of the involved photophysical processes.

  20. Thermally induced effect on sub-band gap absorption in Ag doped CdSe thin films

    NASA Astrophysics Data System (ADS)

    Kaur, Jagdish; Sharma, Kriti; Bharti, Shivani; Tripathi, S. K.

    2015-05-01

    Thin films of Ag doped CdSe have been prepared by thermal evaporation using inert gas condensation (IGC) method taking Argon as inert gas. The prepared thin films are annealed at 363 K for one hour. The sub-band gap absorption spectra in the as deposited and annealed thin films have been studied using constant photocurrent method (CPM). The absorption coefficient in the sub-band gap region is described by an Urbach tail in both as deposited and annealed thin films. The value of Urbach energy and number density of trap states have been calculated from the absorption coefficient in the sub-band gap region which have been found to increase after annealing treatment indicating increase in disorderness in the lattice. The energy distribution of the occupied density of states below Fermi level has also been studied using derivative procedure of absorption coefficient.

  1. A parallel algorithm for transient solid dynamics simulations with contact detection

    SciTech Connect

    Attaway, S.; Hendrickson, B.; Plimpton, S.; Gardner, D.; Vaughan, C.; Heinstein, M.; Peery, J.

    1996-06-01

    Solid dynamics simulations with Lagrangian finite elements are used to model a wide variety of problems, such as the calculation of impact damage to shipping containers for nuclear waste and the analysis of vehicular crashes. Using parallel computers for these simulations has been hindered by the difficulty of searching efficiently for material surface contacts in parallel. A new parallel algorithm for calculation of arbitrary material contacts in finite element simulations has been developed and implemented in the PRONTO3D transient solid dynamics code. This paper will explore some of the issues involved in developing efficient, portable, parallel finite element models for nonlinear transient solid dynamics simulations. The contact-detection problem poses interesting challenges for efficient implementation of a solid dynamics simulation on a parallel computer. The finite element mesh is typically partitioned so that each processor owns a localized region of the finite element mesh. This mesh partitioning is optimal for the finite element portion of the calculation since each processor must communicate only with the few connected neighboring processors that share boundaries with the decomposed mesh. However, contacts can occur between surfaces that may be owned by any two arbitrary processors. Hence, a global search across all processors is required at every time step to search for these contacts. Load-imbalance can become a problem since the finite element decomposition divides the volumetric mesh evenly across processors but typically leaves the surface elements unevenly distributed. In practice, these complications have been limiting factors in the performance and scalability of transient solid dynamics on massively parallel computers. In this paper the authors present a new parallel algorithm for contact detection that overcomes many of these limitations.

  2. Transient electrically detected magnetic resonance spectroscopy applied to organic solar cells

    SciTech Connect

    Kraffert, Felix; Steyrleuthner, Robert; Meier, Christoph; Bittl, Robert; Behrends, Jan

    2015-07-27

    The influence of light-induced paramagnetic states on the photocurrent generated by polymer:fullerene solar cells is studied using spin-sensitive techniques in combination with laser-flash excitation. For this purpose, we developed a setup that allows for simultaneous detection of transient electron paramagnetic resonance as well as transient electrically detected magnetic resonance (trEDMR) signals from fully processed and encapsulated solar cells. Combining both techniques provides a direct link between photoinduced triplet excitons, charge transfer states, and free charge carriers as well as their influence on the photocurrent generated by organic photovoltaic devices. Our results obtained from solar cells based on poly(3-hexylthiophene) as electron donor and a fullerene-based electron acceptor show that the resonant signals observed in low-temperature (T = 80 K) trEDMR spectra can be attributed to positive polarons in the polymer as well as negative polarons in the fullerene phase, indicating that both centers are involved in spin-dependent processes that directly influence the photocurrent.

  3. Potentialities of steady-state and transient thermography in breast tumour depth detection: A numerical study.

    PubMed

    Amri, Amina; Pulko, Susan Helen; Wilkinson, Anthony James

    2016-01-01

    Breast thermography still has inherent limitations that prevent it from being fully accepted as a breast screening modality in medicine. The main challenges of breast thermography are to reduce false positive results and to increase the sensitivity of a thermogram. Further, it is still difficult to obtain information about tumour parameters such as metabolic heat, tumour depth and diameter from a thermogram. However, infrared technology and image processing have advanced significantly and recent clinical studies have shown increased sensitivity of thermography in cancer diagnosis. The aim of this paper is to study numerically the possibilities of extracting information about the tumour depth from steady state thermography and transient thermography after cold stress with no need to use any specific inversion technique. Both methods are based on the numerical solution of Pennes bioheat equation for a simple three-dimensional breast model. The effectiveness of two approaches used for depth detection from steady state thermography is assessed. The effect of breast density on the steady state thermal contrast has also been studied. The use of a cold stress test and the recording of transient contrasts during rewarming were found to be potentially suitable for tumour depth detection during the rewarming process. Sensitivity to parameters such as cold stress temperature and cooling time is investigated using the numerical model and simulation results reveal two prominent depth-related characteristic times which do not strongly depend on the temperature of the cold stress or on the cooling period. PMID:26522612

  4. Electrochemical Detection of Transient Cobalt Hydride Intermediates of Electrocatalytic Hydrogen Production.

    PubMed

    Wiedner, Eric S; Bullock, R Morris

    2016-07-01

    A large variety of molecular cobalt complexes are used as electrocatalysts for H2 production, but the key cobalt hydride intermediates are frequently difficult to detect and characterize due to their high reactivity. We report that a combination of variable scan rate cyclic voltammetry and foot-of-the-wave analysis (FOWA) can be used to detect transient Co(III)H and Co(II)H intermediates of electrocatalytic H2 production by [Co(II)(P(tBu)2N(Ph)2)(CH3CN)3](2+) and Co(II)(dmgBF2)2(CH3CN)2. In both cases, reduction of a transient catalytic intermediate occurs at a potential that coincides with the Co(II/I) couple. Each reduction displays quasireversible electron-transfer kinetics, consistent with reduction of a Co(III)H intermediate to Co(II)H, which is then protonated by acid to generate H2. A bridge-protonated Co(I) species was ruled out as a catalytic intermediate for Co(II)(dmgBF2)2(CH3CN)2 from voltammograms recorded at 1000 psi of H2. Density functional theory was used to calculate Co(III)-H and Co(II)-H bond strengths for both catalysts. Despite having very different ligands, the cobalt hydrides of both catalysts possess nearly identical heterolytic and homolytic Co-H bond strengths for the Co(III)H and Co(II)H intermediates. PMID:27300721

  5. Discrimination of steady state and transient state of dither extremum seeking control via sinusoidal detection

    NASA Astrophysics Data System (ADS)

    Mu, Baojie; Li, Yaoyu; Seem, John E.

    2016-08-01

    A major class of extremum seeking control (ESC) is based on the use of periodic dither perturbation of plant input for extracting the gradient information. Presence of the dither input into the steady state operation is undesirable in practice due to the possible excessive wear of actuators. It is thus beneficial to stop the dithering action after the ESC reaches its steady state. In this paper, we propose a method for automatically discriminating between the steady state and the transient state modes of extremum seeking control process using the sinusoidal detection techniques. Some design guidelines are proposed for the parameter selection of the relevant sinusoidal detection scheme. The proposed scheme is validated with simulation study on dynamic virtual plant of two building HVAC systems.

  6. Detection of transient synchrony across oscillating receptors by the central electrosensory system of mormyrid fish

    PubMed Central

    Vélez, Alejandro; Carlson, Bruce A

    2016-01-01

    Recently, we reported evidence for a novel mechanism of peripheral sensory coding based on oscillatory synchrony. Spontaneously oscillating electroreceptors in weakly electric fish (Mormyridae) respond to electrosensory stimuli with a phase reset that results in transient synchrony across the receptor population (Baker et al., 2015). Here, we asked whether the central electrosensory system actually detects the occurrence of synchronous oscillations among receptors. We found that electrosensory stimulation elicited evoked potentials in the midbrain exterolateral nucleus at a short latency following receptor synchronization. Frequency tuning in the midbrain resembled peripheral frequency tuning, which matches the intrinsic oscillation frequencies of the receptors. These frequencies are lower than those in individual conspecific signals, and instead match those found in collective signals produced by groups of conspecifics. Our results provide further support for a novel mechanism for sensory coding based on the detection of oscillatory synchrony among peripheral receptors. DOI: http://dx.doi.org/10.7554/eLife.16851.001 PMID:27328322

  7. Using GPS to Rapidly Detect and Model Earthquakes and Transient Deformation Events

    NASA Astrophysics Data System (ADS)

    Crowell, Brendan W.

    The rapid modeling and detection of earthquakes and transient deformation is a problem of extreme societal importance for earthquake early warning and rapid hazard response. To date, GPS data is not used in earthquake early warning or rapid source modeling even in Japan or California where the most extensive geophysical networks exist. This dissertation focuses on creating algorithms for automated modeling of earthquakes and transient slip events using GPS data in the western United States and Japan. First, I focus on the creation and use of high-rate GPS and combined seismogeodetic data for applications in earthquake early warning and rapid slip inversions. Leveraging data from earthquakes in Japan and southern California, I demonstrate that an accurate magnitude estimate can be made within seconds using P wave displacement scaling, and that a heterogeneous static slip model can be generated within 2-3 minutes. The preliminary source characterization is sufficiently robust to independently confirm the extent of fault slip used for rapid assessment of strong ground motions and improved tsunami warning in subduction zone environments. Secondly, I investigate the automated detection of transient slow slip events in Cascadia using daily positional estimates from GPS. Proper geodetic characterization of transient deformation is necessary for studies of regional interseismic, coseismic and postseismic tectonics, and miscalculations can affect our understanding of the regional stress field. I utilize the relative strength index (RSI) from financial forecasting to create a complete record of slow slip from continuous GPS stations in the Cascadia subduction zone between 1996 and 2012. I create a complete history of slow slip across the Cascadia subduction zone, fully characterizing the timing, progression, and magnitude of events. Finally, using a combination of continuous and campaign GPS measurements, I characterize the amount of extension, shear and subsidence in the

  8. Far-field infrared super-resolution microscopy using picosecond time-resolved transient fluorescence detected IR spectroscopy

    NASA Astrophysics Data System (ADS)

    Sakai, Makoto; Kawashima, Yasutake; Takeda, Akihiro; Ohmori, Tsutomu; Fujii, Masaaki

    2007-05-01

    A new far-field infrared super-resolution microscopy combining laser fluorescence microscope and picosecond time-resolved transient fluorescence detected IR (TFD-IR) spectroscopy is proposed. TFD-IR spectroscopy is a kind of IR-visible/UV double resonance spectroscopy, and detects IR transitions by the transient fluorescence due to electronic transition originating from vibrationally excited level populated by IR light. IR images of rhodamine-6G solution and of fluorescent beads were clearly observed by monitoring the transient fluorescence. Super-resolution twice higher than the diffraction limit for IR light was achieved. The IR spectrum due to the transient fluorescence was also measured from spatial domains smaller than the diffraction limit.

  9. Noninvasive Measurement of Transient Change in Viscoelasticity Due to Flow-Mediated Dilation Using Automated Detection of Arterial Wall Boundaries

    NASA Astrophysics Data System (ADS)

    Ikeshita, Kazuki; Hasegawa, Hideyuki; Kanai, Hiroshi

    2011-07-01

    We measured the stress-strain relationship of the radial arterial wall during a heartbeat noninvasively. In our previous study, the viscoelasticity of the intima-media region was estimated from the stress-strain relationship, and the transient change in viscoelasticity due to flow-mediated dilation (FMD) was estimated. In this estimation, it is necessary to detect the lumen-intima boundary (LIB) and the media-adventitia boundary (MAB). To decrease the operator dependence, in the present study, a method is proposed for automatic and objective boundary detection based on template matching between the measured and adaptive model ultrasonic signals. Using this method, arterial wall boundaries were appropriately detected in in vivo experiments. Furthermore, the transient change in viscoelasticity estimated from the stress-strain relationship was similar to that obtained manually. These results show the feasibility of the proposed method for automatic boundary detection enabling an objective and appropriate analysis of the transient change in viscoelasticity due to FMD.

  10. 47 CFR 15.323 - Specific requirements for devices operating in the 1920-1930 MHz sub-band.

    Code of Federal Regulations, 2011 CFR

    2011-10-01

    ... 47 Telecommunication 1 2011-10-01 2011-10-01 false Specific requirements for devices operating in the 1920-1930 MHz sub-band. 15.323 Section 15.323 Telecommunication FEDERAL COMMUNICATIONS COMMISSION GENERAL RADIO FREQUENCY DEVICES Unlicensed Personal Communications Service Devices § 15.323 Specific requirements for devices operating in the...

  11. When visual transients impair tactile change detection: a novel case of crossmodal change blindness?

    PubMed

    Gallace, Alberto; Auvray, Malika; Tan, Hong Z; Spence, Charles

    2006-05-01

    The inability of people to detect changes between consecutively presented visual displays, when separated by a blank screen or distractor, is known as "change blindness". This phenomenon has recently been reported to occur within the auditory and tactile modalities as well. To date, however, only distractors presented within the same sensory modality as the change have been demonstrated to produce change blindness. In the present experiment, we studied whether tactile change blindness might also be elicited by the presentation of a visual mask. Participants made same versus different judgments regarding two successively presented displays composed of two to three vibrotactile stimuli. While change detection performance was near-perfect when the two displays were presented one directly after the other, participants failed to detect many of the changes between the tactile displays when they were separated by an empty temporal interval. Critically, performance deteriorated still further when the presentation of a local (i.e., a mudsplash) or global visual transient coincided with the onset of the second tactile pattern. Analysis of the results using signal detection theory revealed that this crossmodal effect reflected a genuine perceptual impairment. PMID:16480821

  12. Possible Detection of Volcanic Activity on Europa: Analysis of An Optical Transient Event

    NASA Astrophysics Data System (ADS)

    de La Fuente Marcos, R.; Nissar, A.

    2002-06-01

    Europa's low crater density suggests that geological activity has continued to the present epoch, leading to the possibility that current resurfacing events might be detectable. CCD observations were carried out with a ST-6 camera at the 0.5 m Mons Cassegrain telescope (Izaña Observatory, Tenerife,Canary Islands, Spain) during the night between 2 3 October 1999. Our images show a transient bright feature on the Galilean satellite. These images are analyzed here with the purpose of understanding the nature of the transient phenomena as it could be the result of explosive venting on the surface of the Jovian satellite. By comparison, we use NASA Infrared Telescope Facility images of two Io hot spots taken on12 October 1990. Although we mainly restrict our discussion on apossible eruptive nature of the observed spots, we also consider other alternative mechanisms able to produce bright events. In particular, an interaction between charged material being ejected from Europa and the Jovian magnetosphere cannot be entirely ruled out. If confirmed, this result would lend support for the existence of active resurfacing in Europa.

  13. Understanding of sub-band gap absorption of femtosecond-laser sulfur hyperdoped silicon using synchrotron-based techniques

    PubMed Central

    Limaye, Mukta V.; Chen, S. C.; Lee, C. Y.; Chen, L. Y.; Singh, Shashi B.; Shao, Y. C.; Wang, Y. F.; Hsieh, S. H.; Hsueh, H. C.; Chiou, J. W.; Chen, C. H.; Jang, L. Y.; Cheng, C. L.; Pong, W. F.; Hu, Y. F.

    2015-01-01

    The correlation between sub-band gap absorption and the chemical states and electronic and atomic structures of S-hyperdoped Si have been extensively studied, using synchrotron-based x-ray photoelectron spectroscopy (XPS), x-ray absorption near-edge spectroscopy (XANES), extended x-ray absorption fine structure (EXAFS), valence-band photoemission spectroscopy (VB-PES) and first-principles calculation. S 2p XPS spectra reveal that the S-hyperdoped Si with the greatest (~87%) sub-band gap absorption contains the highest concentration of S2− (monosulfide) species. Annealing S-hyperdoped Si reduces the sub-band gap absorptance and the concentration of S2− species, but significantly increases the concentration of larger S clusters [polysulfides (Sn2−, n > 2)]. The Si K-edge XANES spectra show that S hyperdoping in Si increases (decreased) the occupied (unoccupied) electronic density of states at/above the conduction-band-minimum. VB-PES spectra evidently reveal that the S-dopants not only form an impurity band deep within the band gap, giving rise to the sub-band gap absorption, but also cause the insulator-to-metal transition in S-hyperdoped Si samples. Based on the experimental results and the calculations by density functional theory, the chemical state of the S species and the formation of the S-dopant states in the band gap of Si are critical in determining the sub-band gap absorptance of hyperdoped Si samples. PMID:26098075

  14. Transient power supply voltage (v{sub DDT}) analysis for detecting IC defects

    SciTech Connect

    Cole, E.I. Jr.; Soden, J.M.; Beegle, R.W.

    1997-04-01

    Transient power supply voltage (V{sub DDT}) analysis is a new testing technique demonstrated as a powerful alternative and complement to I{sub DDQ} testing. V{sub DDT} takes advantage of the limited response time of a voltage supply to the changing power demands of an IC during operation. Changes in the V{sub DD} response time are used to detect increases in power demand with resolutions of 100 nA at 100 kHz, 1 {mu}A at 1 MHz, and 2.5 {mu}A at 1.5 MHz. These current sensitivities have been shown for ICs with quiescent currents < 0.1 {mu}A and > 300 {mu}A. The V{sub DDT} signal acquisition protocols, frequency versus sensitivity tradeoffs, hardware considerations and limitations, data examples, and areas for future research are described.

  15. Visible-super-resolution infrared microscopy using saturated transient fluorescence detected infrared spectroscopy

    NASA Astrophysics Data System (ADS)

    Bokor, Nándor; Inoue, Keiichi; Kogure, Satoshi; Fujii, Masaaki; Sakai, Makoto

    2010-02-01

    A scanning visible-super-resolution microscope based on the saturation behaviour of transient fluorescence detected infrared (TFD-IR) spectroscopy is proposed. A Gaussian IR beam, a Gaussian visible beam and a Laguerre-Gaussian (LG) visible beam are used to obtain two separate two-color excitation fluorescence (2CF) images of the sample. The final image is obtained as the difference between the two recorded images. If the peak intensity of the LG beam is high enough to induce saturation in the fluorescence signal, the image can, in principle, have unlimited spatial resolution. A ˜3-fold improvement in transverse resolution over the visible diffraction limit (and far exceeding the IR diffraction limit) is easily achievable in present experimental setups.

  16. Real-time detection of transient cardiac ischemic episodes from ECG signals.

    PubMed

    Dranca, L; Goñi, A; Illarramendi, A

    2009-09-01

    We propose a new algorithm to detect and classify transient cardiac ischemia episodes, designed with the goal of providing a real-time execution without penalizing the classifier accuracy much. The algorithm is based on a novel mixture of time-domain analysis and machine learning techniques, specifically bagging of decision trees, and it has been developed using a well-recognized and freely distributed database, namely the long-term ST database. The ST episode detection sensitivity/positive predictivity using the annotation protocol A for this database is 68.26%/74.91%. The sensitivity result increases until 93.97% for the most dangerous episodes in terms of duration and magnitude (annotated according to protocol C). The test of the algorithm over the freely distributed part of the European Society of Cardiology database has shown results of sensitivity and positive predictivity of 83.33% and 77.31%, respectively. Those results are close to the results obtained by related works that present approaches to detect ischemia episodes off-line, which is remarkable if we take into account that in our real-time approach, less information is available during the classification process. PMID:19696464

  17. The Corralitos Observatory program for the detection of lunar transient phenomena

    NASA Technical Reports Server (NTRS)

    Hynek, J. A.; Dunlap, J. R.; Hendry, E. M.

    1976-01-01

    This is a final report on the establishment, observing procedures, and observational results of a survey program for the detection of lunar transient phenomena (LTP's) by electro-optical image conversion means. For survey, a unique detection system with an image orthicon was used as the primary element in conjunction with a 24-in. f/20 Cassegrainian telescope. Observations in three spectral ranges, with 6,466 man-hours of observing, were actually performed during the period from October 27, 1965, to April 26, 1972. Within this entire period, no color or feature change within the detection capabilities of the instrumentation was observed, either independently or in follow up of amateur LTP reports, with the exception of one general bluing and several localized bluings (probably ascribable to the effects of the terrestrial atmosphere) that were observed solely by the Corralitos system. A table is presented indicating amateur and professional reports of LTP's and the results of efforts to confirm these reports through the Corralitos system.

  18. LOFAR MSSS: detection of a low-frequency radio transient in 400 h of monitoring of the North Celestial Pole

    NASA Astrophysics Data System (ADS)

    Stewart, A. J.; Fender, R. P.; Broderick, J. W.; Hassall, T. E.; Muñoz-Darias, T.; Rowlinson, A.; Swinbank, J. D.; Staley, T. D.; Molenaar, G. J.; Scheers, B.; Grobler, T. L.; Pietka, M.; Heald, G.; McKean, J. P.; Bell, M. E.; Bonafede, A.; Breton, R. P.; Carbone, D.; Cendes, Y.; Clarke, A. O.; Corbel, S.; de Gasperin, F.; Eislöffel, J.; Falcke, H.; Ferrari, C.; Grießmeier, J.-M.; Hardcastle, M. J.; Heesen, V.; Hessels, J. W. T.; Horneffer, A.; Iacobelli, M.; Jonker, P.; Karastergiou, A.; Kokotanekov, G.; Kondratiev, V. I.; Kuniyoshi, M.; Law, C. J.; van Leeuwen, J.; Markoff, S.; Miller-Jones, J. C. A.; Mulcahy, D.; Orru, E.; Pandey-Pommier, M.; Pratley, L.; Rol, E.; Röttgering, H. J. A.; Scaife, A. M. M.; Shulevski, A.; Sobey, C. A.; Stappers, B. W.; Tasse, C.; van der Horst, A. J.; van Velzen, S.; van Weeren, R. J.; Wijers, R. A. M. J.; Wijnands, R.; Wise, M.; Zarka, P.; Alexov, A.; Anderson, J.; Asgekar, A.; Avruch, I. M.; Bentum, M. J.; Bernardi, G.; Best, P.; Breitling, F.; Brüggen, M.; Butcher, H. R.; Ciardi, B.; Conway, J. E.; Corstanje, A.; de Geus, E.; Deller, A.; Duscha, S.; Frieswijk, W.; Garrett, M. A.; Gunst, A. W.; van Haarlem, M. P.; Hoeft, M.; Hörandel, J.; Juette, E.; Kuper, G.; Loose, M.; Maat, P.; McFadden, R.; McKay-Bukowski, D.; Moldon, J.; Munk, H.; Norden, M. J.; Paas, H.; Polatidis, A. G.; Schwarz, D.; Sluman, J.; Smirnov, O.; Steinmetz, M.; Thoudam, S.; Toribio, M. C.; Vermeulen, R.; Vocks, C.; Wijnholds, S. J.; Wucknitz, O.; Yatawatta, S.

    2016-03-01

    We present the results of a four-month campaign searching for low-frequency radio transients near the North Celestial Pole with the Low-Frequency Array (LOFAR), as part of the Multifrequency Snapshot Sky Survey (MSSS). The data were recorded between 2011 December and 2012 April and comprised 2149 11-min snapshots, each covering 175 deg2. We have found one convincing candidate astrophysical transient, with a duration of a few minutes and a flux density at 60 MHz of 15-25 Jy. The transient does not repeat and has no obvious optical or high-energy counterpart, as a result of which its nature is unclear. The detection of this event implies a transient rate at 60 MHz of 3.9^{+14.7}_{-3.7}× 10^{-4} d-1 deg-2, and a transient surface density of 1.5 × 10-5 deg-2, at a 7.9-Jy limiting flux density and ˜10-min time-scale. The campaign data were also searched for transients at a range of other time-scales, from 0.5 to 297 min, which allowed us to place a range of limits on transient rates at 60 MHz as a function of observation duration.

  19. Extragalactic Synchrotron Transients in the Era of Wide-field Radio Surveys. I. Detection Rates and Light Curve Characteristics

    NASA Astrophysics Data System (ADS)

    Metzger, Brian D.; Williams, P. K. G.; Berger, Edo

    2015-06-01

    The impending era of wide-field radio surveys has the potential to revolutionize our understanding of astrophysical transients. Here we evaluate the prospects of a wide range of planned and hypothetical radio surveys using the properties and volumetric rates of known and hypothetical classes of extragalactic synchrotron radio transients (e.g., on-axis and off-axis gamma-ray bursts (GRBs), supernovae, tidal disruption events, compact object mergers). Utilizing these sources and physically motivated considerations we assess the allowed phase space of radio luminosity and peak timescale for extragalactic transients. We also include for the first time effects such as redshift evolution of the rates, K-corrections, and non-Euclidean luminosity distance, which affect the detection rates of the most sensitive surveys. The number of detected events is calculated by means of a Monte Carlo method, using the various survey properties (depth, cadence, area) and realistic detection criteria that include a cut on the minimum variability of the transients during the survey and an assessment of host galaxy contamination. We find that near-term GHz frequency surveys (ASKAP/VAST, Very Large Array Sky Survey) will detect few events: ≲ 30-50 on- and off-axis long GRBs (LGRBs) and off-axis tidal disruption events, and ∼ 50-100 neutron star binary mergers if ∼ 0.5% of the mergers result in a stable millisecond magnetar. Low-frequency surveys (e.g., LOFAR) are unlikely to detect any transients, while a hypothetical large-scale mm survey may detect ∼40 on-axis LGRBs. On the other hand, we find that SKA1 surveys at ∼ 0.1-1 GHz have the potential to uncover thousands of transients, mainly on-axis and off-axis LGRBs, on-axis short GRBs, off-axis TDEs, and neutron star binary mergers with magnetar remnants.

  20. Transient Grating Spectroscopy in Magnetic Thin Films: Simultaneous Detection of Elastic and Magnetic Dynamics

    PubMed Central

    Janušonis, J.; Jansma, T.; Chang, C. L.; Liu, Q.; Gatilova, A.; Lomonosov, A. M.; Shalagatskyi, V.; Pezeril, T.; Temnov, V. V.; Tobey, R. I.

    2016-01-01

    Surface magnetoelastic waves are coupled elastic and magnetic excitations that propagate along the surface of a magnetic material. Ultrafast optical techniques allow for a non-contact excitation and detection scheme while providing the ability to measure both elastic and magnetic components individually. Here we describe a simple setup suitable for excitation and time resolved measurements of high frequency magnetoelastic waves, which is based on the transient grating technique. The elastic dynamics are measured by diffracting a probe laser pulse from the long-wavelength spatially periodic structural deformation. Simultaneously, a magnetooptical measurement, either Faraday or Kerr effect, is sensitive to the out-of-plane magnetization component. The correspondence in the response of the two channels probes the resonant interaction between the two degrees of freedom and reveals their intimate coupling. Unraveling the observed dynamics requires a detailed understanding of the spatio-temporal evolution of temperature, magnetization and thermo-elastic strain in the ferromagnet. Numerical solution of thermal diffusion in two dimensions provides the basis on which to understand the sensitivity in the magnetooptic detection. PMID:27377262

  1. Transient Grating Spectroscopy in Magnetic Thin Films: Simultaneous Detection of Elastic and Magnetic Dynamics.

    PubMed

    Janušonis, J; Jansma, T; Chang, C L; Liu, Q; Gatilova, A; Lomonosov, A M; Shalagatskyi, V; Pezeril, T; Temnov, V V; Tobey, R I

    2016-01-01

    Surface magnetoelastic waves are coupled elastic and magnetic excitations that propagate along the surface of a magnetic material. Ultrafast optical techniques allow for a non-contact excitation and detection scheme while providing the ability to measure both elastic and magnetic components individually. Here we describe a simple setup suitable for excitation and time resolved measurements of high frequency magnetoelastic waves, which is based on the transient grating technique. The elastic dynamics are measured by diffracting a probe laser pulse from the long-wavelength spatially periodic structural deformation. Simultaneously, a magnetooptical measurement, either Faraday or Kerr effect, is sensitive to the out-of-plane magnetization component. The correspondence in the response of the two channels probes the resonant interaction between the two degrees of freedom and reveals their intimate coupling. Unraveling the observed dynamics requires a detailed understanding of the spatio-temporal evolution of temperature, magnetization and thermo-elastic strain in the ferromagnet. Numerical solution of thermal diffusion in two dimensions provides the basis on which to understand the sensitivity in the magnetooptic detection. PMID:27377262

  2. Leak detection in medium density polyethylene (MDPE) pipe using pressure transient method

    NASA Astrophysics Data System (ADS)

    Amin, M. M.; Ghazali, M. F.; PiRemli, M. A.; Hamat, A. M. A.; Adnan, N. F.

    2015-12-01

    Water is an essential part of commodity for a daily life usage for an average person, from personal uses such as residential or commercial consumers to industries utilization. This study emphasizes on detection of leaking in medium density polyethylene (MDPE) pipe using pressure transient method. This type of pipe is used to analyze the position of the leakage in the pipeline by using Ensemble Empirical Mode Decomposition Method (EEMD) with signal masking. Water hammer would induce an impulse throughout the pipeline that caused the system turns into a surge of water wave. Thus, solenoid valve is used to create a water hammer through the pipelines. The data from the pressure sensor is collected using DASYLab software. The data analysis of the pressure signal will be decomposed into a series of wave composition using EEMD signal masking method in matrix laboratory (MATLAB) software. The series of decomposition of signals is then carefully selected which reflected intrinsic mode function (IMF). These IMFs will be displayed by using a mathematical algorithm, known as Hilbert transform (HT) spectrum. The IMF signal was analysed to capture the differences. The analyzed data is compared with the actual measurement of the leakage in term of percentage error. The error recorded is below than 1% and it is proved that this method highly reliable and accurate for leak detection.

  3. Noninvasive methods, including transient elastography, for the detection of liver disease in adults with cystic fibrosis

    PubMed Central

    Sadler, Matthew D; Crotty, Pam; Fatovich, Linda; Wilson, Stephanie; Rabin, Harvey R; Myers, Robert P

    2015-01-01

    BACKGROUND: Liver disease is the third leading cause of mortality in patients with cystic fibrosis (CF). However, detection of CF-associated liver disease (CFLD) is challenging. OBJECTIVE: To evaluate the diagnostic performance of noninvasive methods for the detection of CFLD with a focus on transient elastography (TE). METHODS: Patients at the Adult CF Clinic of Calgary and Southern Alberta (n=127) underwent liver stiffness measurement (LSM) by TE using the FibroScan (FS, Ecosens, France) M probe; aspartate amino-transferase to platelet ratio index (APRI) and FibroTest (FT) scores were also calculated. The diagnostic performance of these tools for the detection of CFLD (defined as two or more the following criteria: abnormal liver biochemistry, hepatomegaly or sonographic abnormalities other than steatosis) were compared using the area under ROC curves. RESULTS: Forty-seven percent of the cohort was male. The median age was 27 years (interquartile range [IQR] 22 to 37 years) and body mass index 21 kg/m2 (IQR 19 kg/m2 to 23 kg/m2); 25% of patients were on ursodeoxycholic acid and 12% had undergone lung transplantation. The prevalence of CFLD was 14% (n=18). FS was successful in all patients; one (0.8%) patient had poorly reliable results (IQR/M >30% and LSM ≥7.1kPa). Compared with patients without CFLD (n=109), individuals with CFLD had higher median LSM according to FS (3.9 kPa [IQR 3.4 to 4.9 kPa] versus 6.4 kPa [IQR 4.4 to 8.0 kPa]), APRI (0.24 [IQR 0.17 to 0.31] versus 0.50 [IQR 0.22 to 1.18]) and FT scores (0.08 [IQR 0.05 to 1.5] versus 0.18 [IQR 0.11 to 0.35]; all P<0.05). Area under ROC curve for FS, APRI and FT for the detection of CFLD were 0.78 (95% CI 0.65 to 0.92), 0.72 (95% CI 0.56 to 0.87) and 0.76 (95% CI 0.62 to 0.90) (P not significant). At a threshold of >5.2 kPa, the sensitivity, specificity, positive and negative predictive values of LSM according to FS for detecting CFLD were 67%, 83%, 40% and 94%, respectively. CONCLUSIONS: FS, APRI and FT

  4. Swift/BAT detects an outburst from an X-ray transient in the globular cluster Terzan 5

    NASA Astrophysics Data System (ADS)

    Altamirano, D.; Krimm, H. A.; Patruno, A.; Bahramian, A.; Heinke, C. O.; Wijnands, R.; Degenaar, N.

    2015-03-01

    A rate increase from the direction of Terzan 5 was detected in the BAT hard X-ray transient monitor starting on 2015 March 13 (MJD 57094). The flux has been rising and has reached 0.007 +/- 0.001 ct s^-1 cm^-2 (~30 mCrab; 15-50 keV) on 2015 March 16.

  5. Frequency Shift and Sub-band Effect in Pair-Production Process Under Adiabatic Closing the External Field

    NASA Astrophysics Data System (ADS)

    Song, Xinfang; Wang, Wenyuan; Fu, Libin

    2016-09-01

    Oscillating electric field is chosen to investigate the electron-positron pair production process by using a quantum kinetic theory and the effective mass model [Phys. Rev. Lett. 112, 050402 (2014)]. The particle yield exhibits a characteristic oscillatory structure which is related to the multi-photon thresholds. The true peak positions are typically slightly above the naive threshold estimate, which is defined as frequency shift. During the numerical calculations, we find the frequency shift can be affected by the system parameters under adiabatic closing the external field, it is worthwhile to study in detail. In this paper, we investigate the frequency shift and the sub-band effect in electron-positron pair production with oscillating electric field. First, a quantum kinetic theory and the effective mass are presented to obtain the frequency shift, the results are fitted very well. And we find the frequency shift and the sub-band effect can be influenced by pulse duration, photon number, and strength of the external field. The frequency shift becomes evident as increases of photon number and the external field strength. The sub-band width is relatively lower at longer pulse duration, higher photon number region, and weaker external field. The results shown in the paper are helpful for understanding multi-photon pair production process in the strong field.

  6. Frequency Shift and Sub-band Effect in Pair-Production Process Under Adiabatic Closing the External Field

    NASA Astrophysics Data System (ADS)

    Song, Xinfang; Wang, Wenyuan; Fu, Libin

    2016-04-01

    Oscillating electric field is chosen to investigate the electron-positron pair production process by using a quantum kinetic theory and the effective mass model [Phys. Rev. Lett. 112, 050402 (2014)]. The particle yield exhibits a characteristic oscillatory structure which is related to the multi-photon thresholds. The true peak positions are typically slightly above the naive threshold estimate, which is defined as frequency shift. During the numerical calculations, we find the frequency shift can be affected by the system parameters under adiabatic closing the external field, it is worthwhile to study in detail. In this paper, we investigate the frequency shift and the sub-band effect in electron-positron pair production with oscillating electric field. First, a quantum kinetic theory and the effective mass are presented to obtain the frequency shift, the results are fitted very well. And we find the frequency shift and the sub-band effect can be influenced by pulse duration, photon number, and strength of the external field. The frequency shift becomes evident as increases of photon number and the external field strength. The sub-band width is relatively lower at longer pulse duration, higher photon number region, and weaker external field. The results shown in the paper are helpful for understanding multi-photon pair production process in the strong field.

  7. Transient Elastography with Serum Hepatitis B Surface Antigen Enhances Liver Fibrosis Detection

    PubMed Central

    Dai, Tianyi; Si, Jia; Hao, Meina; Li, Cheng; Liu, Xia; Li, Jie; Ma, Anlin

    2016-01-01

    Background The aim of this study was to explore transient elastography (TE) with quantitative hepatitis B surface antigen (qHBsAg) for detecting advanced hepatic fibrosis. Material/Methods This was a single-center prospective real-life analysis of 111 treatment-naïve chronic hepatitis B (CHB) patients enrolled into the Establishment of Non-invasive Diagnosis Criteria and Model of Hepatitis B Virus-related Cirrhosis Study. Results There were significant correlations between TE, qHBsAg, and fibrosis. Both qHBsAg and TE were identified as independent predictors for advanced fibrosis. In receiver operating characteristic curve (ROC) analysis, TEqHBsAg (combination of TE and qHBsAg) resulted in the highest area under the receiver-operator curve (AUC) (0.912), mainly due to increased specificity. Using the optimal cut-off, TEqHBsAg provided a sensitivity of 86.7%, and increased specificity from 78.7% to 85.1%. Conclusions Combining TE with qHBsAg enhances specificity in identifying advanced fibrosis in treatment-naïve CHB patients. PMID:27526179

  8. Transient dynamic phenotypes as criteria for model discrimination: fold-change detection in Rhodobacter sphaeroides chemotaxis.

    PubMed

    Hamadeh, Abdullah; Ingalls, Brian; Sontag, Eduardo

    2013-03-01

    The chemotaxis pathway of the bacterium Rhodobacter sphaeroides shares many similarities with that of Escherichia coli. It exhibits robust adaptation and has several homologues of the latter's chemotaxis proteins. Recent theoretical results have correctly predicted that the E. coli output behaviour is unchanged under scaling of its ligand input signal; this property is known as fold-change detection (FCD). In the light of recent experimental results suggesting that R. sphaeroides may also show FCD, we present theoretical assumptions on the R. sphaeroides chemosensory dynamics that can be shown to yield FCD behaviour. Furthermore, it is shown that these assumptions make FCD a property of this system that is robust to structural and parametric variations in the chemotaxis pathway, in agreement with experimental results. We construct and examine models of the full chemotaxis pathway that satisfy these assumptions and reproduce experimental time-series data from earlier studies. We then propose experiments in which models satisfying our theoretical assumptions predict robust FCD behaviour where earlier models do not. In this way, we illustrate how transient dynamic phenotypes such as FCD can be used for the purposes of discriminating between models that reproduce the same experimental time-series data. PMID:23293140

  9. Transient Cataluminescence on Flowerlike MgO for Discrimination and Detection of Volatile Organic Compounds.

    PubMed

    Xu, Honglin; Li, Qiuyan; Zhang, Lichun; Zeng, Binrong; Deng, Dongyan; Lv, Yi

    2016-08-16

    Methodologies for simple and rapid identification of gas compounds are needed in the fields of environmental and security. Here, a new and simple method for the discrimination of gas compounds was designed through an interesting transient cataluminescence (TRCTL) phenomenon on the highly efficient MgO materials. The flowerlike MgO with high CTL activity was controllably synthesized via a facile and time-saving aqueous precipitation route and characterized by scanning electron microscopy, powder X-ray diffractometry, high-resolution transmission electron microscopy, and N2 adsorption measurements, etc. With flowerlike MgO working as the sensing material, the newly developed CTL gas sensor exhibited highly active, ultrafast, and characteristic responses toward many analytes; the TRCTL curves thus were obtained and 10 VOCs have been successfully identified. Parallel experimental results show that the controllable synthesis of flowerlike MgO can greatly enhance the discrimination capacities for VOCs. Further, the TRCTL of CHCl3 and C2H5OC2H5 were taken as typical examples to illustrate the possible sensing mechanism, which could contribute to explaining processes of catalytic oxidations. We expect this novel TRCTL concept will be of practical importance for applications including gas detection, gas discrimination, and research of chemical kinetics processes. PMID:27417505

  10. Attosecond transient absorption probing of electronic superpositions of bound states in neon. Detection of quantum beats

    DOE PAGESBeta

    Beck, Annelise R; Bernhardt, Birgitta; Warrick, Erika R.; Wu, Mengxi; Chen, Shaohao; Gaarde, Mette B.; Schafer, Kenneth J.; Neumark, Daniel M.; Leone, Stephen R.

    2014-11-07

    Electronic wavepackets composed of multiple bound excited states of atomic neon lying between 19.6 and 21.5 eV are launched using an isolated attosecond pulse. Individual quantum beats of the wavepacket are detected by perturbing the induced polarization of the medium with a time-delayed few-femtosecond near-infrared (NIR) pulse via coupling the individual states to multiple neighboring levels. All of the initially excited states are monitored simultaneously in the attosecond transient absorption spectrum, revealing Lorentzian to Fano lineshape spectral changes as well as quantum beats. The most prominent beating of the several that were observed was in the spin–orbit split 3d absorptionmore » features, which has a 40 femtosecond period that corresponds to the spin–orbit splitting of 0.1 eV. The few-level models and multilevel calculations confirm that the observed magnitude of oscillation depends strongly on the spectral bandwidth and tuning of the NIR pulse and on the location of possible coupling states.« less

  11. Attosecond transient absorption probing of electronic superpositions of bound states in neon. Detection of quantum beats

    SciTech Connect

    Beck, Annelise R; Bernhardt, Birgitta; Warrick, Erika R.; Wu, Mengxi; Chen, Shaohao; Gaarde, Mette B.; Schafer, Kenneth J.; Neumark, Daniel M.; Leone, Stephen R.

    2014-11-07

    Electronic wavepackets composed of multiple bound excited states of atomic neon lying between 19.6 and 21.5 eV are launched using an isolated attosecond pulse. Individual quantum beats of the wavepacket are detected by perturbing the induced polarization of the medium with a time-delayed few-femtosecond near-infrared (NIR) pulse via coupling the individual states to multiple neighboring levels. All of the initially excited states are monitored simultaneously in the attosecond transient absorption spectrum, revealing Lorentzian to Fano lineshape spectral changes as well as quantum beats. The most prominent beating of the several that were observed was in the spin–orbit split 3d absorption features, which has a 40 femtosecond period that corresponds to the spin–orbit splitting of 0.1 eV. The few-level models and multilevel calculations confirm that the observed magnitude of oscillation depends strongly on the spectral bandwidth and tuning of the NIR pulse and on the location of possible coupling states.

  12. The transducer vibratory profile effects on the detection of the transient ultrasonic field scattered by a rigid point reflector.

    PubMed

    Khelladi, Hassina; Djelouah, Hakim

    2010-04-01

    In this study a generalized approach, based on the impulse response technique, is developed to evaluate the transient ultrasonic field scattered by a rigid point reflector and detected by a planar circular transducer characterized by a non-uniform vibratory profile. For this purpose, several analytical functions are used to represent the non-uniform vibration amplitude of the transducer. All these functions have maximum amplitude at the transducer's center and decrease monotonically away from axis. The amplitude variation of these functions has a direct effect on the shape of the average pressure detected by the transducer. Some numerical results are presented to illustrate the effects of a non-uniformly vibrating source on the detected transient pressure. The results show the relative importance of the edge wave modifications in the case of source having non-uniform vibration amplitude distribution. PMID:19906391

  13. Sub-band transport mechanism and switching properties for resistive switching nonvolatile memories with structure of silver/aluminum oxide/p-type silicon

    SciTech Connect

    Liu, Yanhong; Li, La; Wang, Song; Gao, Ping; Pan, Lujun; Zhang, Jialiang; Zhou, Peng; Li, Jinhua; Weng, Zhankun

    2015-02-09

    In this paper, we discuss a model of sub-band in resistive switching nonvolatile memories with a structure of silver/aluminum oxide/p-type silicon (Ag/Al{sub x}O{sub y}/p-Si), in which the sub-band is formed by overlapping of wave functions of electron-occupied oxygen vacancies in Al{sub x}O{sub y} layer deposited by atomic layer deposition technology. The switching processes exhibit the characteristics of the bipolarity, discreteness, and no need of forming process, all of which are discussed deeply based on the model of sub-band. The relationships between the SET voltages and distribution of trap levels are analyzed qualitatively. The semiconductor-like behaviors of ON-state resistance affirm the sub-band transport mechanism instead of the metal filament mechanism.

  14. Transient and sustained BOLD signal time courses affect the detection of emotion-related brain activation in fMRI.

    PubMed

    Paret, Christian; Kluetsch, Rosemarie; Ruf, Matthias; Demirakca, Traute; Kalisch, Raffael; Schmahl, Christian; Ende, Gabriele

    2014-12-01

    A tremendous amount of effort has been dedicated to unravel the functional neuroanatomy of the processing and regulation of emotion, resulting in a well-described picture of limbic, para-limbic and prefrontal regions involved. Studies applying functional magnetic resonance imaging (fMRI) often use the block-wise presentation of stimuli with affective content, and conventionally model brain activation as a function of stimulus or task duration. However, there is increasing evidence that regional brain responses may not always translate to task duration and rather show stimulus onset-related transient time courses. We assume that brain regions showing transient responses cannot be detected in block designs using a conventional fMRI analysis approach. At the same time, the probability of detecting these regions with conventional analyses may be increased when shorter stimulus timing or a more intense stimulation during a block is used. In a within-subject fMRI study, we presented aversive pictures to 20 healthy subjects and investigated the effect of experimental design (i.e. event-related and block design) on the detection of brain activation in limbic and para-limbic regions of interest of emotion processing. In addition to conventional modeling of sustained activation during blocks of stimulus presentation, we included a second response function into the general linear model (GLM), suited to detect transient time courses at block onset. In the conventional analysis, several regions like the amygdala, thalamus and periaqueductal gray were activated irrespective of design. However, we found a positive BOLD response in the anterior insula (AI) in event-related but not in block-design analyses. GLM analyses suggest that this difference may result from a transient response pattern which cannot be captured by the conventional fMRI analysis approach. Our results indicate that regions with a transient response profile like the AI can be missed in block designs if analyses

  15. Membrane-proximal calcium transients in stimulated neutrophils detected by total internal reflection fluorescence.

    PubMed Central

    Omann, G M; Axelrod, D

    1996-01-01

    A novel fluorescence microscope/laser optical system was developed to measure fast transients of membrane-proximal versus bulk cytoplasmic intracellular calcium levels in cells labeled with a fluorescent calcium indicator. The method is based on the rapid chopping of illumination of the cells between optical configurations for epifluorescence, which excites predominantly the bulk intracellular region, and total internal reflection fluorescence, which excites only the region within approximately 100 nm of the cell-substrate contact. This method was applied to Fluo-3-loaded neutrophils that were activated by the chemoattractant N-formyl-met-leu-phe. Chemoattractant-activated cells showed 1) transient increases in both membrane-proximal and bulk cytosolic Ca2+ that peaked simultaneously; 2) a larger fractional change (20-60%) in membrane-proximal Ca2+ relative to bulk cytosolic Ca2+ that peaked at a time when the main Ca2+ transient was decreasing in both regions and that persisted well after the main transient was over. This method should be applicable to a wide variety of cell types and fluorescent ion indicators in which membrane-proximal ionic transients may be different from those deeper within the cytosol. Images FIGURE 1 FIGURE 2 PMID:8913625

  16. Detection of weak transient signals based on wavelet packet transform and manifold learning for rolling element bearing fault diagnosis

    NASA Astrophysics Data System (ADS)

    Wang, Yi; Xu, Guanghua; Liang, Lin; Jiang, Kuosheng

    2015-03-01

    The kurtogram-based methods have been proved powerful and practical to detect and characterize transient components in a signal. The basic idea of the kurtogram-based methods is to use the kurtosis as a measure to discover the presence of transient impulse components and to indicate the frequency band where these occur. However, the performance of the kurtogram-based methods is poor due to the low signal-to-noise ratio. As the weak transient signal with a wide spread frequency band can be easily masked by noise. Besides, selecting signal just in one frequency band will leave out some transient features. Aiming at these shortcomings, different frequency bands signal fusion is adopted in this paper. Considering that manifold learning aims at discovering the nonlinear intrinsic structure which embedded in high dimensional data, this paper proposes a waveform feature manifold (WFM) method to extract the weak signature from waveform feature space which obtained by binary wavelet packet transform. Minimum permutation entropy is used to select the optimal parameter in a manifold learning algorithm. A simulated bearing fault signal and two real bearing fault signals are used to validate the improved performance of the proposed method through the comparison with the kurtogram-based methods. The results show that the proposed method outperforms the kurtogram-based methods and is effective in weak signature extraction.

  17. Excited-state transient of vanadyl uroporphyrin I detected by resonance Raman spectroscopy

    SciTech Connect

    Alden, R.G.; Sparks, L.D.; Ondrias, M.R. ); Crawford, B.A.; Shelnutt, J.A. )

    1990-02-22

    Transient Raman spectroscopy has been used to investigate excited states of vanadyl uroporphyrin I (VOUroP) in both monomeric and dimeric forms. Uroporphyrins are water-soluble porphyrins with propionic and acetic acid groups substituted at the {beta}-pyrrole carbon positions. Monomeric VOUroP in aqueous solution is known to be six-coordinate with a ligand trans to the oxo ligand. Upon dimerization, the sixth ligand site is inaccessible, and a five-coordinate species is observed. At high laser fluence, an excited-state transient is formed in the monomeric species. Raman spectra of this species are most consistent with an {sup 2}A{sub 1u} (a{sub 1u}({pi}) {yields} d{sub xy}) charge-transfer state. In contrast, dimeric VOUroP shows little evidence of an excited state in the transient Raman spectra during a 10-ns laser pulse.

  18. The experimental detection of spectral diffusion by the saturation transient method

    NASA Astrophysics Data System (ADS)

    Boscaino, R.; Gelardi, F. M.; Mantegna, R. N.

    The effect of spectral diffusion (SD) on the saturation properties of an inhomogeneous spin system has been experimentally investigated by examining the saturation transient regime of a sample of DPPH diluted in polystyrene ( c ˜ 2 × 10 18 cm -3) at T = 4.2 K. In agreement with the theoretical results obtained in our previous paper, two different regimes can be singled out in the experimental curves of the saturation transient response, at short and at long times, respectively. The agreement between theoretical and experimental results is quantitative as regards the dependence of the saturation transient curves on the microwave field strength. The comparison allows determination of the value of the characteristic time Td of the SD as 20 ± 5 μs.

  19. Tissue differentiation using laser-induced shock waves by detection of acoustic transients through an optical wave-guide

    NASA Astrophysics Data System (ADS)

    Tschepe, Johannes; Ahrens, Thomas; Helfmann, Juergen; Mueller, Gerhard J.; Gapontsev, Valentin P.

    1993-05-01

    Some physical phenomena which occur during the fragmentation of calculi by laser induced optical break down are presented. With in vitro experiments it could be shown that the energy of the laser induced plasma and of the cavitation bubble (induced by the plasma) depends by the nature of the tissue. The laser induced plasma and the cavitation bubble generate shock waves. These sound waves are transferred via the laser fiber and detected with a piezo- electrical sensor at the proximal end. The acoustic signal contains information on the potential energy of the bubble, which depends on the energy of the plasma. The possibility of measuring the energy dependent acoustic transients allows to distinguish between hard and soft tissue and by this it is suitable for controlling the laser lithotripsy process. The transmission of acoustic transients through silica glass fibers is investigated by theoretical calculations. It shows the feasibility of silica glass fibers as an acoustic wave guide.

  20. Analysis of Fundus Fluorescein Angiogram Based on the Hessian Matrix of Directional Curvelet Sub-bands and Distance Regularized Level Set Evolution.

    PubMed

    Soltanipour, Asieh; Sadri, Saeed; Rabbani, Hossein; Akhlaghi, Mohammad Reza

    2015-01-01

    This paper presents a new procedure for automatic extraction of the blood vessels and optic disk (OD) in fundus fluorescein angiogram (FFA). In order to extract blood vessel centerlines, the algorithm of vessel extraction starts with the analysis of directional images resulting from sub-bands of fast discrete curvelet transform (FDCT) in the similar directions and different scales. For this purpose, each directional image is processed by using information of the first order derivative and eigenvalues obtained from the Hessian matrix. The final vessel segmentation is obtained using a simple region growing algorithm iteratively, which merges centerline images with the contents of images resulting from modified top-hat transform followed by bit plane slicing. After extracting blood vessels from FFA image, candidates regions for OD are enhanced by removing blood vessels from the FFA image, using multi-structure elements morphology, and modification of FDCT coefficients. Then, canny edge detector and Hough transform are applied to the reconstructed image to extract the boundary of candidate regions. At the next step, the information of the main arc of the retinal vessels surrounding the OD region is used to extract the actual location of the OD. Finally, the OD boundary is detected by applying distance regularized level set evolution. The proposed method was tested on the FFA images from angiography unit of Isfahan Feiz Hospital, containing 70 FFA images from different diabetic retinopathy stages. The experimental results show the accuracy more than 93% for vessel segmentation and more than 87% for OD boundary extraction. PMID:26284170

  1. Long gravitational-wave transients and associated detection strategies for a network of terrestrial interferometers

    SciTech Connect

    Thrane, Eric; Kandhasamy, Shivaraj; Dorsher, Steven; Mandic, Vuk; Prestegard, Tanner; Ott, Christian D.; Anderson, Warren G.; Christensen, Nelson L.; Coughlin, Michael W.; Giampanis, Stefanos; Mytidis, Antonis; Whiting, Bernard; Raffai, Peter

    2011-04-15

    Searches for gravitational waves (GWs) traditionally focus on persistent sources (e.g., pulsars or the stochastic background) or on transients sources (e.g., compact binary inspirals or core-collapse supernovae), which last for time scales of milliseconds to seconds. We explore the possibility of long GW transients with unknown waveforms lasting from many seconds to weeks. We propose a novel analysis technique to bridge the gap between short O(s)''burst'' analyses and persistent stochastic analyses. Our technique utilizes frequency-time maps of GW strain cross power between two spatially separated terrestrial GW detectors. The application of our cross power statistic to searches for GW transients is framed as a pattern recognition problem, and we discuss several pattern-recognition techniques. We demonstrate these techniques by recovering simulated GW signals in simulated detector noise. We also recover environmental noise artifacts, thereby demonstrating a novel technique for the identification of such artifacts in GW interferometers. We compare the efficiency of this framework to other techniques such as matched filtering.

  2. Reversible hippocampal lesions detected on magnetic resonance imaging in two cases of transient selective amnesia for simple machine operation.

    PubMed

    Yamaoka, Yumiko; Bandoh, Mitsuaki; Kawai, Kensuke

    2016-08-01

    We report two extremely rare cases involving the development of transient selective retrograde amnesia for simple machine operation lasting for several hours. A 61-year-old male taxi driver suddenly became unable to operate a taximeter, and a 66-year-old female janitor suddenly became unable to use a fax machine. They could precisely recount their episodes to others both during and after the attacks, and their memories during their attacks corresponded to the memory of the witness and the medical records of the doctor, respectively. Therefore, it appears that these individuals remained alert and did not develop anterograde amnesia during their attacks. On day 4, they underwent high-resolution magnetic resonance imaging (MRI), and diffusion-weighted MRI with 2-mm section thickness revealed small high-intensity signal lesions in the left hippocampal cornu ammonis area 1 (CA1) region. However, these lesions disappeared during the chronic phase. This is the first report describing lesions detected by MRI in patients with transient selective amnesia without anterograde amnesia. Reversible damage to the hippocampal CA1 region may cause transient selective amnesia by impairing the retrieval of relevant memories. PMID:27367337

  3. A steady-state Kalman predictor-based filtering strategy for non-overlapping sub-band spectral estimation.

    PubMed

    Li, Zenghui; Xu, Bin; Yang, Jian; Song, Jianshe

    2015-01-01

    This paper focuses on suppressing spectral overlap for sub-band spectral estimation, with which we can greatly decrease the computational complexity of existing spectral estimation algorithms, such as nonlinear least squares spectral analysis and non-quadratic regularized sparse representation. Firstly, our study shows that the nominal ability of the high-order analysis filter to suppress spectral overlap is greatly weakened when filtering a finite-length sequence, because many meaningless zeros are used as samples in convolution operations. Next, an extrapolation-based filtering strategy is proposed to produce a series of estimates as the substitutions of the zeros and to recover the suppression ability. Meanwhile, a steady-state Kalman predictor is applied to perform a linearly-optimal extrapolation. Finally, several typical methods for spectral analysis are applied to demonstrate the effectiveness of the proposed strategy. PMID:25609038

  4. Computing approximate blocking probability of inverse multiplexing and sub-band conversion in the flexible-grid optical networks

    NASA Astrophysics Data System (ADS)

    Gu, Yamei; You, Shanhong

    2016-07-01

    With the rapid growth of data rate, the optical network is evolving from fixed-grid to flexible-grid to provide spectrum-efficient and scalable transport of 100 Gb/s services and beyond. Also, the deployment of wavelength converter in the existing network can increase the flexibility of routing and wavelength allocation (RWA) and improve blocking performance of the optical networks. In this paper, we present a methodology for computing approximate blocking probabilities of the provision of multiclass services in the flexible-grid optical networks with sub-band spectrum conversion and inverse multiplexing respectively. Numerical calculation results based on the model are compared to the simulation results for the different cases. It is shown that the calculation results match well with the simulation results for the flexible-grid optical networks at different scenarios.

  5. A Steady-State Kalman Predictor-Based Filtering Strategy for Non-Overlapping Sub-Band Spectral Estimation

    PubMed Central

    Li, Zenghui; Xu, Bin; Yang, Jian; Song, Jianshe

    2015-01-01

    This paper focuses on suppressing spectral overlap for sub-band spectral estimation, with which we can greatly decrease the computational complexity of existing spectral estimation algorithms, such as nonlinear least squares spectral analysis and non-quadratic regularized sparse representation. Firstly, our study shows that the nominal ability of the high-order analysis filter to suppress spectral overlap is greatly weakened when filtering a finite-length sequence, because many meaningless zeros are used as samples in convolution operations. Next, an extrapolation-based filtering strategy is proposed to produce a series of estimates as the substitutions of the zeros and to recover the suppression ability. Meanwhile, a steady-state Kalman predictor is applied to perform a linearly-optimal extrapolation. Finally, several typical methods for spectral analysis are applied to demonstrate the effectiveness of the proposed strategy. PMID:25609038

  6. Spitzer mid-IR detection of optical transient in NGC 3344 and candidate progenitor

    NASA Astrophysics Data System (ADS)

    Prieto, J. L.

    2012-10-01

    We report on analysis of archival Spitzer data of the recent optical transient discovered and reported in the CBAT TOCP by M. Tsuboi at RA = 10:43:34.05 and DEC = +24:53:29.0 in the nearby galaxy NGC 3344 at 6.4 Mpc (from Virgo-corrected recession velocity via NED). The host galaxy has been observed with Spitzer IRAC (Apr. 2004 and Jul. 2012) and MIPS (Jan. 2008) instruments by different programs: 69 (PI: Fazio), 40204 (PI: Kennicutt), and 80025 (PI: van Zee).

  7. Delamination detection in foam core composite structures using transient flexural wavefields

    NASA Astrophysics Data System (ADS)

    Lamboul, B.; Osmont, D.

    2016-03-01

    This paper investigates a health monitoring technique for foam sandwich structures based on flexural wavefields imaged by Laser Doppler vibrometry. A study of calibrated artificial defect responses in harmonic regime demonstrates that the use of a low frequency regime (below 30 kHz) makes it possible to excite defects in their first flexural resonance modes. The analysis performed in harmonic regime is used to interpret signature patterns obtained with accumulated energy maps from transient wavefield recordings. The potential of the technique is demonstrated on a real impact-induced defect. The robustness of the method relatively to the excitation center frequency selection and to the presence of wave reverberation is demonstrated.

  8. Electron Traps Detected in p-type GaAsN Using Deep Level Transient Spectroscopy

    SciTech Connect

    Johnston, S.; Kurtz, S.; Friedman, D.; Ptak, A.; Ahrenkiel, R.; Crandall, R.

    2005-01-01

    The GaAsN alloy can have a band gap as small as 1.0 eV when the nitrogen composition is about 2%. Indium can also be added to the alloy to increase lattice matching to GaAs and Ge. These properties are advantageous for developing a highly-efficient, multi-junction solar cell. However, poor GaAsN cell properties, such as low open-circuit voltage, have led to inadequate performance. Deep-level transient spectroscopy of p-type GaAsN has identified an electron trap having an activation energy near 0.2 eV and a trap density of at least 1016 cm-3. This trap level appears with the addition of small amounts of nitrogen to GaAs, which also corresponds to an increased drop in open-circuit voltage.

  9. An Algorithm for Real-Time Optimal Photocurrent Estimation Including Transient Detection for Resource-Constrained Imaging Applications

    NASA Astrophysics Data System (ADS)

    Zemcov, Michael; Crill, Brendan; Ryan, Matthew; Staniszewski, Zak

    2016-06-01

    Mega-pixel charge-integrating detectors are common in near-IR imaging applications. Optimal signal-to-noise ratio estimates of the photocurrents, which are particularly important in the low-signal regime, are produced by fitting linear models to sequential reads of the charge on the detector. Algorithms that solve this problem have a long history, but can be computationally intensive. Furthermore, the cosmic ray background is appreciable for these detectors in Earth orbit, particularly above the Earth’s magnetic poles and the South Atlantic Anomaly, and on-board reduction routines must be capable of flagging affected pixels. In this paper, we present an algorithm that generates optimal photocurrent estimates and flags random transient charge generation from cosmic rays, and is specifically designed to fit on a computationally restricted platform. We take as a case study the Spectro-Photometer for the History of the Universe, Epoch of Reionization, and Ices Explorer (SPHEREx), a NASA Small Explorer astrophysics experiment concept, and show that the algorithm can easily fit in the resource-constrained environment of such a restricted platform. Detailed simulations of the input astrophysical signals and detector array performance are used to characterize the fitting routines in the presence of complex noise properties and charge transients. We use both Hubble Space Telescope Wide Field Camera-3 and Wide-field Infrared Survey Explorer to develop an empirical understanding of the susceptibility of near-IR detectors in low earth orbit and build a model for realistic cosmic ray energy spectra and rates. We show that our algorithm generates an unbiased estimate of the true photocurrent that is identical to that from a standard line fitting package, and characterize the rate, energy, and timing of both detected and undetected transient events. This algorithm has significant potential for imaging with charge-integrating detectors in astrophysics, earth science, and remote

  10. Construction of a High Temporal-spectral Resolution Spectrometer for Detection of Fast Transients from Observations of the Sun at 1.4 GHz.

    NASA Astrophysics Data System (ADS)

    Casillas-Perez, G. A.; Jeyakumar, S.; Perez-Enriquez, R.

    2014-12-01

    Transients explosive events with time durations from nanoseconds to several hours, are observed in the Sun at high energy bands such as gamma ray and xray. In the radio band, several types of radio bursts are commonly detected from the ground. A few observations of the Sun in the past have also detected a new class of fast transients which are known to have short-live electromagnetic emissions with durations less than 100 ms. The mechanisms that produce such fast transiets remain unclear. Observations of such fast transients over a wide bandwidth is necessary to uderstand the underlying physical process that produce such fast transients. Due to their very large flux densities, fast radio transients can be observed at high time resolution using small antennas in combination with digital signal processing techniques. In this work we report the progress of an spectrometer that is currently in construction at the Observatorio de la Luz of the Universidad de Guanajuato. The instrument which will have the purpose of detecting solar fast radio transients, involves the use of digital devices such as FPGA and ADC cards, in addition with a receiver with high temporal-spectral resolution centered at 1.4 GHz and a pair of 2.3 m satellite dish.

  11. Time-resolved detection of stimulus/task-related networks, via clustering of transient intersubject synchronization.

    PubMed

    Bordier, Cécile; Macaluso, Emiliano

    2015-09-01

    Several methods are available for the identification of functional networks of brain areas using functional magnetic resonance imaging (fMRI) time-series. These typically assume a fixed relationship between the signal of the areas belonging to the same network during the entire time-series (e.g., positive correlation between the areas belonging to the same network), or require a priori information about when this relationship may change (task-dependent changes of connectivity). We present a fully data-driven method that identifies transient network configurations that are triggered by the external input and that, therefore, include only regions involved in stimulus/task processing. Intersubject synchronization with short sliding time-windows was used to identify if/when any area showed stimulus/task-related responses. Next, a first clustering step grouped together areas that became engaged concurrently and repetitively during the time-series (stimulus/task-related networks). Finally, for each network, a second clustering step grouped together all the time-windows with the same BOLD signal. The final output consists of a set of network configurations that show stimulus/task-related activity at specific time-points during the fMRI time-series. We label these configurations: "brain modes" (bModes). The method was validated using simulated datasets and a real fMRI experiment with multiple tasks and conditions. Future applications include the investigation of brain functions using complex and naturalistic stimuli. PMID:26095530

  12. Transient-based analysis for the detection of broken damper bars in synchronous motors

    NASA Astrophysics Data System (ADS)

    Antonino-Daviu, J. A.; Climente-Alarcón, V.; Pons-Llinares, J.; Puche, R.; Pineda-Sánchez, M.

    2013-01-01

    Synchronous generators and motors constitute critical elements in power generation plants and certain industrial facilities. Damper bars are crucial components of most of these synchronous machines. They enable, among other functions, the direct-on-line starting of these machines, just as if they were asynchronous. Some recent cases, reported by several authors, have demonstrated that eventual failure of damper bars is possible, mainly due to the currents and stresses rising during their operation. In this context, the development of reliable techniques able to diagnose possible damper breakages has attracted significant interest within the fault diagnosis area. The present paper proposes the application of a novel transient-based methodology to diagnose broken damper bars in synchronous motors. This methodology was previously assessed with success in industrial induction motors with diverse sizes. The approach relies on the analysis of the stator startup current demanded by the machine during a direct-on-line starting. To this end, suitable time-frequency decomposition tools are used. In this particular work, the Discrete Wavelet Transform (DWT) is proposed, due to its simplicity, low computational requirements and easy interpretation of its results. Simulation and experimental results obtained with laboratory synchronous machines confirm the validity of the approach for condition monitoring of such windings.

  13. On the sub-band gap optical absorption in heat treated cadmium sulphide thin film deposited on glass by chemical bath deposition technique

    SciTech Connect

    Chattopadhyay, P.; Karim, B.; Guha Roy, S.

    2013-12-28

    The sub-band gap optical absorption in chemical bath deposited cadmium sulphide thin films annealed at different temperatures has been critically analyzed with special reference to Urbach relation. It has been found that the absorption co-efficient of the material in the sub-band gap region is nearly constant up to a certain critical value of the photon energy. However, as the photon energy exceeds the critical value, the absorption coefficient increases exponentially indicating the dominance of Urbach rule. The absorption coefficients in the constant absorption region and the Urbach region have been found to be sensitive to annealing temperature. A critical examination of the temperature dependence of the absorption coefficient indicates two different kinds of optical transitions to be operative in the sub-band gap region. After a careful analyses of SEM images, energy dispersive x-ray spectra, and the dc current-voltage characteristics, we conclude that the absorption spectra in the sub-band gap domain is possibly associated with optical transition processes involving deep levels and the grain boundary states of the material.

  14. Swift/XRT detects renewed activity of the Galactic center X-ray transient Swift J174535.5-285921

    NASA Astrophysics Data System (ADS)

    Degenaar, N.; Wijnands, R.; Reynolds, M. T.; Miller, J. M.; Kennea, J. A.

    2016-07-01

    Our daily Swift/XRT monitoring observations of the Galactic center (Degenaar et al. 2015) have revealed activity of a transient X-ray source located ~1.4' to the north-east of Sgr A*. An excess of photons was first seen during a 0.9-ks PC mode observation performed on 2016 July 7. The object remains to be detected in subsequent observations performed on July 8,9, and 10. To obtain a position for the newly active X-ray source, we use the four PC-mode observations obtained between July 7 and 10 (amounting to 3.5 ks of exposure time) and utilize the online XRT data products tool (Evans et al. 2007, 2009).

  15. MAXI/GSC detection of brightening of a transient LMXB 4U 1608-522

    NASA Astrophysics Data System (ADS)

    Morii, Mikio

    2010-03-01

    MAXI/GSC detected an X-ray brightening of the LMXB 4U 1608-522. The source flux has increased since the beginning of March 2, and reached about 20 mCrab in the 4 - 10 keV band on 2010 March 3 (MJD 55258). By combining this result with the detection of an X-ray burst by SuperAGILE (Atel #2461), we suggest that this source has entered into an active state. The multi-wavelength follow-up observations are encouraged.

  16. DETECTION OF A TRANSIENT X-RAY ABSORPTION LINE INTRINSIC TO THE BL LACERTAE OBJECT H 2356-309

    SciTech Connect

    Fang Taotao; Buote, David A.; Humphrey, Philip J.; Canizares, Claude R.

    2011-04-10

    Since the launch of the Einstein X-ray Observatory in the 1970s, a number of broad absorption features have been reported in the X-ray spectra of BL Lac objects. These features are often interpreted as arising from high-velocity outflows intrinsic to the BL Lac object, therefore providing important information about the inner environment around the central engine. However, such absorption features have not been observed more recently with high-resolution X-ray telescopes such as Chandra and XMM-Newton. In this paper, we report the detection of a transient X-ray absorption feature intrinsic to the BL Lac object H 2356-309 with the Chandra X-ray Telescope. This BL Lac object was observed during XMM-Newton cycle 7 and Chandra cycles 8 and 10, as part of our campaign to investigate X-ray absorption produced by the warm-hot intergalactic medium residing in the foreground large-scale superstructure. During one of the 80 ks Chandra cycle 10 observations, a transient absorption feature was detected at 3.3{sigma} (or 99.9% confidence level, accounting for the number of 'trials), which we identify as the O VIII K{alpha} line produced by an absorber intrinsic to the BL Lac object. None of the other 11 observations showed this line. We constrain the ionization parameter (25 {approx}< {Xi} {approx}< 40) and temperature (10{sup 5} K

  17. Detection of defects in laser powder deposition (LPD) components by pulsed laser transient thermography

    NASA Astrophysics Data System (ADS)

    Santospirito, S. P.; Słyk, Kamil; Luo, Bin; Łopatka, Rafał; Gilmour, Oliver; Rudlin, John

    2013-05-01

    Detection of defects in Laser Powder Deposition (LPD) produced components has been achieved by laser thermography. An automatic in-process NDT defect detection software system has been developed for the analysis of laser thermography to automatically detect, reliably measure and then sentence defects in individual beads of LPD components. A deposition path profile definition has been introduced so all laser powder deposition beads can be modeled, and the inspection system has been developed to automatically generate an optimized inspection plan in which sampling images follow the deposition track, and automatically control and communicate with robot-arms, the source laser and cameras to implement image acquisition. Algorithms were developed so that the defect sizes can be correctly evaluated and these have been confirmed using test samples. Individual inspection images can also be stitched together for a single bead, a layer of beads or multiple layers of beads so that defects can be mapped through the additive process. A mathematical model was built up to analyze and evaluate the movement of heat throughout the inspection bead. Inspection processes were developed and positional and temporal gradient algorithms have been used to measure the flaw sizes. Defect analysis is then performed to determine if the defect(s) can be further classified (crack, lack of fusion, porosity) and the sentencing engine then compares the most significant defect or group of defects against the acceptance criteria - independent of human decisions. Testing on manufactured defects from the EC funded INTRAPID project has successful detected and correctly sentenced all samples.

  18. Detection of the new rotating radio transient pulsar PSR J2225+35

    NASA Astrophysics Data System (ADS)

    Shitov, Yu. P.; Kuzmin, A. D.; Dumskii, D. V.; Losovsky, B. Ya.

    2009-06-01

    We have detected the new pulsar PSR J2225+35, which displays the properties of the new class of radio sources “Rotating Radio Transients” (RRATs). RRATs are distinguished by isolated bursts of radio emission and long quiet periods. Throughout 45 observations with a total duration of about 3 hr, only two bursts of radio emission lasting a total of about 10 min were detected in two observations. The temporal and frequency delay of the pulses corresponds to the dispersion measure DM = 51.8 pc/cm3 and the distance d = 3.05 kpc. The period of the pulses is P = 0.94 s. The emission is polarized, with the rotation measure being RM = 49.8 rad/m2.

  19. Detecting water in aviation honeycomb structures by using transient infrared thermographic NDT

    NASA Astrophysics Data System (ADS)

    Vavilov, Vladimir P.; Klimov, Alexey G.; Nesteruk, Dmitry; Shiryaev, Vladimir V.

    2003-04-01

    A lot of structural key elements of many modern civilian and military airplanes, such as flaps, keel, etc., are made of honeycomb structures. Honeycombs involve a combination of some materials including aluminum, Nomex, glass and graphite epoxy composites. During exploitation, atmosphere water could penetrate these structures due to possible imperfections in various junctions, and, thus, deteriorate airplane durability. In Russia, water in honeycombs is typically detected by using the X ray and ultrasonic technique. However, the X ray equipment is hardly accepted by commercial airlines because of the safety reason, and the point-by-point ultrasonic inspection is low-productive. Since 2002, we develop the IR thermographic method of detecting water by thermally stimulating aviation panels under test. Unlike the technique accepted by Airbus Industry, Inc., that uses 'a warm blanket', we use a powerful optical heater assembled with an IR camera into a single set. The first stage of research included modeling the detection process and optimizing the experimental procedure. As a result, we have demonstrated that, due to the high heat capacity of water, a temperature signal over moist areas evolves in time during a relatively long period that relaxes the requirements to the test protocol. Thus, even aluminum panels can be thermally stimulated during few seconds with a delay time being also in a few second range. A similar protocol can be applied to the inspection of composite honeycombs where the image quality resembles that obtained by X rays. The paper will describe all stages of the research starting from modeling and finishing with the preliminary experimental results obtained in situ on civilian airplanes.

  20. Unfolding of Proteins and Long Transient Conformations Detected by Single Nanopore Recording

    NASA Astrophysics Data System (ADS)

    Oukhaled, G.; Mathé, J.; Biance, A.-L.; Bacri, L.; Betton, J.-M.; Lairez, D.; Pelta, J.; Auvray, L.

    2007-04-01

    We study the electrophoretic blockades due to entries of partially unfolded proteins into a nanopore as a function of the concentration of the denaturing agent. Short and long pore blockades are observed by electrical detection. Short blockades are due to the passage of completely unfolded proteins, their frequency increases as the concentration of the denaturing agent increases, following a sigmoidal denaturation curve. Long blockades reveal partially folded conformations. Their duration increases as the proteins are more folded. The observation of a Vogel-Fulcher law suggests a glassy behavior.

  1. Highly sensitive transient isotachophoresis sample stacking coupling with capillary electrophoresis-amperometric detection for analysis of doping substances.

    PubMed

    Zheng, Lihui; Zhang, Lan; Tong, Ping; Zheng, Xinyu; Chi, Yuwu; Chen, Guonan

    2010-06-15

    A simple and effective method of capillary electrophoresis-amperometric detection (CE-AD) coupled with transient isotachophoresis (tITP) was developed for the trace determination of doping substances. Compared with the conventional capillary electrophoresis method, the maximum enhancement factor in terms of peak heights was up to 5500-fold when the tITP technique was adopted. Under the optimum conditions, the detection limit (S/N=3) for methylephedrine (MDP), celiprolol (CEL), sotalol (SOT) and indapamide (IDP) were 4.2 x 10(-14), 6.3 x 10(-13), 5.8 x 10(-14) and 9.5 x 10(-13)molL(-1), respectively. The RSDs of four analytes were 1.0-2.3% for migration time and 2.6-3.8% for peak current, respectively. The proposed method was successfully applied to determine the contents of SOT and IDP in real urine sample, and the excretion curve of IDP within 48h was also investigated. The recoveries of the four doping in urine ranged from 90.0 to 102%. PMID:20441897

  2. Wide field x-ray telescopes: Detecting x-ray transients/afterglows related to GRBs

    SciTech Connect

    Hudec, Rene; Pina, Ladislav; Inneman, Adolf; Gorenstein, Paul

    1998-05-16

    The recent discovery of X-ray afterglows of GRBs opens the possibility of analyses of GRBs by their X-ray detections. However, imaging X-ray telescopes in current use mostly have limited fields of view. Alternative X-ray optics geometries achieving very large fields of view have been theoretically suggested in the 70's but not constructed and used so far. We review the geometries and basic properties of the wide-field X-ray optical systems based on one- and two-dimensional lobster-eye geometry and suggest technologies for their development and construction. First results of the development of double replicated X-ray reflecting flats for use in one-dimensional X-ray optics of lobster-eye type are presented and discussed. The optimum strategy for locating GRBs upon their X-ray counterparts is also presented and discussed.

  3. Calcium transients in isolated amphibian skeletal muscle fibres: detection with aequorin.

    PubMed Central

    Blinks, J R; Rüdel, R; Taylor, S R

    1978-01-01

    1. Single twitch muscle fibres isolated from frogs and toads were microinjected with the Ca2+-sensitive bioluminescent protein aequorin. The fibres contracted normally and emitted flashes of light (aequorin responses) in response to stimulation for many hours thereafter. 2. No luminescence was detected from healthy fibres at rest. 3. The aequorin diffused from the site of injection at a rate consistent with a diffusion coefficient of 5 x 10(-8) cm2/sec. 4. During trains of isometric contractions there was a progressive reduction in both the amplitude and the rate of decline of the aequorin response, an observation consistent with the theory that Ca is redistributed from sites of release to sites of sequestration under such circumstances. 5. In isometric tetani light emission continued to rise long after the plateau of force had been achieved. This and the fact that the amplitude of the tetanic aequorin response increased steeply with increasing stimulus frequency suggest that in tetani the sarcoplasmic [Ca2+] may normally be above the level required to saturate the contractile apparatus. 6. Both in twitches and in tetani the amplitude of the aequorin response increased slightly and then decreased substantially as the fibre was stretched progressively beyond slack length. 7. In potassium contractures the luminescent and mechanical responses first became detectable at about the same [K+], but for equivalent force luminescence was less intense than in twitches. The aequorin response was biphasic in solutions of high [K+]. 8. Exposure of the fibre to Ca2+-free solutions had no influence on either the mechanical or the luminescent responses in twitches. In Ca2+-free solutions tetanic aequorin responses tended not to be maintained as well as normally, suggesting that intracellular Ca stores do become somewhat depleted. 9. In twitches the amplitude of the aequorin response probably reflects the amount of Ca2+ liberated into the cytoplasm rather than a [Ca2+] in

  4. Fermi/GBM Detection of Transient Enhanced Emission from SGR J1550-5418

    NASA Astrophysics Data System (ADS)

    Kaneko, Yuku; Gogus, Ersin; Kouveliotou, Chryssa; Granot, Jonathan; Ramirez-Ruiz, Enrico; van der Horst, Alexander J.; Watts, Anna L.; Finger, Mark H.; Gehrels, Neil; Pe'Er, Asaf; van der Klis, Michiel; von Kienlin, Andreas; Wachter, Stefanie; Wilson-Hodge, Colleen A.; Woods, Peter M.

    On 2009 January 22, SGR J1550-5418 (previously known as AXP 1E 1547.0-5408) went into a very active bursting episode, and Fermi/GBM detected ˜450 bursts from this source on this day alone. Within the GBM data at the onset of this intense bursting period, we identified underlying enhanced persistent emission with coherent pulsation. We present the detailed timing and spectral analysis of the enhanced emission, which revealed intriguing properties: (i) clear pulsations up to ˜110 keV at the spin period of the neutron star, (ii) spectra requiring a blackbody component with a temperature of ˜17 keV in addition to a power law, and (iii) pulsed fraction that is strongly energy dependent and peaks in 50-74 keV. The estimated area of the blackbody emitting region is very small: ˜0.4 km2 (roughly a few ×10-5 of the neutron star surface area), which may correspond to the size of magnetically-confined hot plasma in the twisted magnetic field near the star's surface.

  5. Time-Lapse Monitoring for Detection of Transient Stress Changes in Geysers Geothermal Field

    NASA Astrophysics Data System (ADS)

    Taira, T.

    2011-12-01

    Temporal changes in the properties of seismic structures are indicators of stress changes at depth, providing a means of continually monitoring the state of stress at seismogenic depth. At the Geysers geothermal field, we investigate stress-induced structural changes by making use of continuous seismic data at high sampling rates from dense seismic networks operated by LBNL and USGS. Our principal focus is on the imaging of time-varying properties of the seismic noise wavefield. Following Bensen et al. (2007) and Brenguier et al. (2008), we analyzed data from August to December 2006, spanning the time of the 20 October 2006 Mw 4.6 Geysers earthquake. A reference Green's function was computed for each station pair by stacking the daily cross-correlations for the entire 5-month period. The changes in seismic structure were determined by measuring time delays between the reference Green's function and 30-day stacks of cross-correlation functions in the frequency range from 0.1 to 0.9 Hz. Our preliminary result shows a change in cross-correlation function immediately after the 2006 Mw 4.6 Geysers earthquake, indicating that the delay time was increased by 0.08 s. We infer the increased delay time to be a change in seismic velocity structure due to a fluid redistribution around the fault resulting from a combination of both post-seismic stress relaxation and fault-zone damage induced by the Mw 4.6 earthquake. The preliminary seismic moment tensor analysis indicates a non double-couple component (40% explosive isotropic component) in the source process of the Mw 4.6 Geysers earthquake, which could also indicate a migration of fluid flow accompanying this Geysers event. Following Peng and Zhao (2009), we have additionally been identifying undetected early aftershocks with a cross-correlation based approach. We use waveforms from 200 Geysers earthquakes detected by the Northern California Seismic Network System during a 2-day period spanning the 2006 Geysers earthquake as

  6. Discriminative Common Spatial Pattern Sub-bands Weighting Based on Distinction Sensitive Learning Vector Quantization Method in Motor Imagery Based Brain-computer Interface

    PubMed Central

    Jamaloo, Fatemeh; Mikaeili, Mohammad

    2015-01-01

    Common spatial pattern (CSP) is a method commonly used to enhance the effects of event-related desynchronization and event-related synchronization present in multichannel electroencephalogram-based brain-computer interface (BCI) systems. In the present study, a novel CSP sub-band feature selection has been proposed based on the discriminative information of the features. Besides, a distinction sensitive learning vector quantization based weighting of the selected features has been considered. Finally, after the classification of the weighted features using a support vector machine classifier, the performance of the suggested method has been compared with the existing methods based on frequency band selection, on the same BCI competitions datasets. The results show that the proposed method yields superior results on “ay” subject dataset compared against existing approaches such as sub-band CSP, filter bank CSP (FBCSP), discriminative FBCSP, and sliding window discriminative CSP. PMID:26284171

  7. The Use of Overlapped Sub-Bands in Multi-Band, Multi-SNR, Multi-Path Recognition of Noisy Word Utterances

    NASA Astrophysics Data System (ADS)

    Tsuboi, Yutaka; Ihara, Takehiro; Takagi, Kazuyuki; Ozeki, Kazuhiko

    A solution to the problem of improving robustness to noise in automatic speech recognition is presented in the framework of multi-band, multi-SNR, and multi-path approaches. In our word recognizer, the whole frequency band is divided into seven-overlapped subbands, and then sub-band noisy phoneme HMMs are trained on speech data mixed with the filtered white Gaussian noise at multiple SNRs. The acoustic model of a word is built as a set of concatenations of clean and noisy sub-band phoneme HMMs arranged in parallel. A Viterbi decoder allows a search path to transit to another SNR condition at a phoneme boundary. The recognition scores of the sub-bands are then recombined to give the score for a word. Experiments show that the overlapped seven-band system yields the best performance under nonstationary ambient noises. It is also shown that the use of filtered white Gaussian noise is advantageous for training noisy phoneme HMMs.

  8. Robust algorithmic detection of the developed cardiac pathologies and emerging or transient abnormalities from short periods of RR data

    NASA Astrophysics Data System (ADS)

    Gavrishchaka, Valeriy V.; Senyukova, Olga

    2011-06-01

    Numerous research efforts and clinical testing have confirmed validity of heart rate variability (HRV) analysis as one of the cardiac diagnostics modalities. The majority of HRV analysis tools currently used in practice are based on linear indicators. Methods from nonlinear dynamics (NLD) provide more natural modeling framework for adaptive biological systems with multiple feedback loops. Compared to linear indicators, many NLD-based measures are much less sensitive to data artifacts and non-stationarity. However, majority of NLD measures require long time series for stable calculation. Similar restrictions also apply for linear indicators. Such requirements could drastically limit practical usability of HRV analysis in many applications, including express diagnostics, early indication of subtle directional changes during personalization of medical treatment, and robust detection of emerging or transient abnormalities. Recently we have illustrated that these challenges could be overcome by using classification framework based on boosting-like ensemble learning techniques that are capable of discovering robust meta-indicators from existing HRV measures and other incomplete empirical knowledge. In this paper we demonstrate universality of such meta-indicators and discuss operational details of their practical usage. Using such pathology examples as congestive heart failure (CHF) and arrhythmias, we show that classifiers trained on short RR segments (down to several minutes) could achieve reasonable classification accuracy (˜80-85% and higher). These indicators calculated from longer RR segments could be applicable for accurate diagnostics with classification accuracy approaching 100%. In addition, it is feasible to discover single "normal-abnormal" meta-classifier capable of detecting multiple abnormalities.

  9. REAL-TIME DETECTION AND RAPID MULTIWAVELENGTH FOLLOW-UP OBSERVATIONS OF A HIGHLY SUBLUMINOUS TYPE II-P SUPERNOVA FROM THE PALOMAR TRANSIENT FACTORY SURVEY

    SciTech Connect

    Gal-Yam, Avishay; Arcavi, Iair; Green, Yoav; Yaron, Ofer; Ben-Ami, Sagi; Xu Dong; Sternberg, Assaf; Kasliwal, Mansi M.; Quimby, Robert M.; Kulkarni, Shrinivas R.; Ofek, Eran O.; Walters, Richard; Nugent, Peter E.; Poznanski, Dovi; Bloom, Joshua S.; Cenko, S. Bradley; Filippenko, Alexei V.; Li Weidong; Silverman, Jeffrey M.; Walker, Emma S.

    2011-08-01

    The Palomar Transient Factory (PTF) is an optical wide-field variability survey carried out using a camera with a 7.8 deg{sup 2} field of view mounted on the 48 inch Oschin Schmidt telescope at Palomar Observatory. One of the key goals of this survey is to conduct high-cadence monitoring of the sky in order to detect optical transient sources shortly after they occur. Here, we describe the real-time capabilities of the PTF and our related rapid multiwavelength follow-up programs, extending from the radio to the {gamma}-ray bands. We present as a case study observations of the optical transient PTF10vdl (SN 2010id), revealed to be a very young core-collapse (Type II-P) supernova having a remarkably low luminosity. Our results demonstrate that the PTF now provides for optical transients the real-time discovery and rapid-response follow-up capabilities previously reserved only for high-energy transients like gamma-ray bursts.

  10. XMM-NEWTON DETECTION OF A TRANSIENT X-RAY SOURCE IN THE VICINITY OF V838 MONOCEROTIS

    SciTech Connect

    Antonini, Fabio; Montez, Rodolfo; Kastner, Joel H.; Bond, Howard E.; Soker, Noam; Behar, Ehud; Tylenda, Romuald; Starrfield, Sumner

    2010-07-10

    We report the XMM-Newton/EPIC detection in 2008 March of a luminous (L{sub X} {approx} 10{sup 32-33} erg s{sup -1}), variable X-ray source in the vicinity (within {approx}6'') of the enigmatic star V838 Mon, which underwent a spectacular outburst in early 2002. Spectral modeling of the XMM-Newton X-ray source indicates the presence of two plasma components with characteristic temperatures of T{sub X} {approx} 2 x 10{sup 6} K and {approx}1.5 x 10{sup 7} K, attenuated by an absorbing column (N{sub H} {approx} 4 x 10{sup 21} cm{sup -2}) that is consistent with the visual extinction measured toward V838 Mon (A{sub V} {approx} 2). No such luminous source was detected in the immediate vicinity of V838 Mon in Chandra/ACIS-S observations obtained about one year after outburst or, most recently, in 2010 January. The two XMM -Newton source spectral components appear to be marginally spatially resolved, with the spatial centroid of the hard component lying closer to (within {approx}2'' of) the position of V838 Mon than the broadband source or the soft source component; however, if there are two sources at or near V838 Mon, the Chandra nondetections would imply that both of them are variable. An alternative is that there is a single variable source, and that the apparent spatial separation may actually be due to photon-counting statistics or is perhaps instrumental in origin. We consider constraints placed by the X-ray detection and nondetections on a stellar merger model for the 2002 V838 Mon outburst, in which the spun-up merger product drives a powerful magnetic dynamo. Alternatively, the transient behavior of the X-ray source could indicate that the X-rays arose as a consequence of an interaction between V838 Mon's ejecta and its early-type (B3 V) companion.

  11. An in vivo detection system for transient and low‐abundant protein interactions and their kinetics in budding yeast

    PubMed Central

    Brezovich, Andrea; Schuschnig, Martina; Ammerer, Gustav

    2015-01-01

    Abstract Methylation tracking (M‐Track) is a protein‐proximity assay in Saccharomyces cerevisiae, allowing the detection of transient protein–protein interactions in living cells. The bait protein is fused to a histone lysine methyl transferase and the prey protein to a methylation acceptor peptide derived from histone 3. Upon interaction, the histone 3 fragment is stably methylated on lysine 9 and can be detected by methylation‐specific antibodies. Since methylation marking is irreversible in budding yeast and only takes place in living cells, the occurrence of artifacts during cell lysate preparation is greatly reduced, leading to a more accurate representation of native interactions. So far, this method has been limited to highly abundant or overexpressed proteins. However, many proteins of interest are low‐abundant, and overexpression of proteins may interfere with their function, leading to an artificial situation. Here we report the generation of a toolbox including a novel cleavage‐enrichment system for the analysis of very low‐abundant proteins at their native expression levels. In addition, we developed a system for the parallel analysis of two prey proteins in a single cell, as well as an inducible methylation system. The inducible system allows precise control over the time during which the interaction is detected and can be used to determine interaction kinetics. Furthermore, we generated a set of constructs facilitating the cloning‐free genomic tagging of proteins at their endogenous locus by homologous recombination, and their expression from centromeric plasmids. GenBank submissions: pCK900; KM407502, pCK901; KM407503, pCK902; KM407504, pCK903; KM407505, pCK904; KM407506, pCK905; KM407507, pCK906; KM407508, pCK907; KM407509, pCK908; KM407510, pCK909; KM407511, pCK910; KM407512, pCK911; KM407513. © 2015 The Authors. Yeast published by John Wiley & Sons Ltd. PMID:25582094

  12. Transient Monoplegia as a Result of Unilateral Femoral Artery Ischemia Detected by Multimodal Intraoperative Neuromonitoring in Posterior Scoliosis Surgery

    PubMed Central

    Pankowski, Rafal; Roclawski, Marek; Dziegiel, Krzysztof; Ceynowa, Marcin; Mikulicz, Marcin; Mazurek, Tomasz; Kloc, Wojciech

    2016-01-01

    Abstract This is to report a case of 16-year-old girl with transient right lower limb monoplegia as a result of femoral artery ischemia detected by multimodal intraoperative spinal cord neuromonitoring (MISNM) during posterior correction surgery of adolescent idiopathic scoliosis. A patient with a marfanoid body habitus and LENKE IA type scoliosis with the right thoracic curve of 48° of Cobb angle was admitted for posterior spinal fusion from Th6 to L2. After selective pedicle screws instrumentation and corrective maneuvers motor evoked potentials (MEP) began to decrease with no concomitant changes in somato-sensory evoked potentials recordings. The instrumentation was released first partially than completely with rod removal but the patient demonstrated constantly increasing serious neurological motor deficit of the whole right lower limb. Every technical cause of the MEP changes was eliminated and during the wake-up test the right foot was found to be pale and cold with no popliteal and dorsalis pedis pulses palpable. The patient was repositioned and the pelvic pad was placed more cranially. Instantly, the pulse and color returned to the patient's foot. Following MEP recordings showed gradual return of motor function up to the baseline at the end of the surgery, whereas somato-sensory evoked potentials were within normal range through the whole procedure. This case emphasizes the importance of the proper pelvic pad positioning during the complex spine surgeries performed in prone position of the patient. A few cases of neurological complications have been described which were the result of vascular occlusion after prolonged pressure in the inguinal area during posterior scoliosis surgery when the patient was in prone position. If incorrectly interpreted, they would have a significant impact on the course of scoliosis surgery. PMID:26871822

  13. Fermi LAT detection of a new high-energy transient gamma-ray source Fermi J0751-5136

    NASA Astrophysics Data System (ADS)

    Kocevski, D.; Buson, S.

    2016-08-01

    During the week from 18 July through 25 July, 2016, the Large Area Telescope (LAT), one of the two instruments on the Fermi Gamma-ray Space Telescope, observed gamma-ray activity from a previously unidentified transient source.

  14. Experimental demonstration of low-complexity fiber chromatic dispersion mitigation for reduced guard-interval OFDM coherent optical communication systems based on digital spectrum sub-band multiplexing.

    PubMed

    Malekiha, Mahdi; Tselniker, Igor; Nazarathy, Moshe; Tolmachev, Alex; Plant, David V

    2015-10-01

    We experimentally demonstrate a novel digital signal processing (DSP) structure for reduced guard-interval (RGI) OFDM coherent optical systems. The proposed concept is based on digitally slicing optical channel bandwidth into multiple spectrally disjoint sub-bands which are then processed in parallel. Each low bandwidth sub-band has a smaller delay-spread compared to a full-band signal. This enables compensation of both chromatic dispersion (CD) and polarization mode dispersion using a simple timing and one-tap-per-symbol frequency domain equalizer with a small cyclic prefix overhead. In terms of the DSP architecture, this allows for a highly efficient parallelization of DSP tasks performed over the received signal samples by deploying multiple processors running at a lower clock rate. It should be noted that this parallelization is performed in the frequency domain and it allows for flexible optical transceiver schemes. In addition, the resulting optical receiver is simplified due to the removal of the CD compensation equalizer compared to conventional RGI-OFDM systems. In this paper we experimentally demonstrate digital sub-banding of optical bandwidth. We test the system performance for different modulation formats (QPSK, 16QAM and 32QAM) over various transmission distances and optical launch powers using a 1.5% CP overhead in all scenarios. We also compare the proposed RGI-OFDM architecture performance against common single carrier modulation formats. At the same total data rate and signal bandwidth both systems have similar performance and transmission reach whereas the proposed method allows for a significant reduction of computational complexity due to removal of CD pre/post compensation equalizer. PMID:26480077

  15. Sub-band gap photo-enhanced secondary electron emission from high-purity single-crystal chemical-vapor-deposited diamond

    NASA Astrophysics Data System (ADS)

    Yater, J. E.; Shaw, J. L.; Pate, B. B.; Feygelson, T. I.

    2016-02-01

    Secondary-electron-emission (SEE) current measured from high-purity, single-crystal (100) chemical-vapor-deposited diamond is found to increase when sub-band gap (3.06 eV) photons are incident on the hydrogenated surface. Although the light does not produce photoemission directly, the SEE current increases by more than a factor of 2 before saturating with increasing laser power. In energy distribution curves (EDCs), the emission peak shows a corresponding increase in intensity with increasing laser power. However, the emission-onset energy in the EDCs remains constant, indicating that the bands are pinned at the surface. On the other hand, changes are observed on the high-energy side of the distribution as the laser power increases, with a well-defined shoulder becoming more pronounced. From an analysis of this feature in the EDCs, it is deduced that upward band bending is present in the near-surface region during the SEE measurements and this band bending suppresses the SEE yield. However, sub-band gap photon illumination reduces the band bending and thereby increases the SEE current. Because the bands are pinned at the surface, we conclude that the changes in the band levels occur below the surface in the electron transport region. Sample heating produces similar effects as observed with sub-band gap photon illumination, namely, an increase in SEE current and a reduction in band bending. However, the upward band bending is not fully removed by either increasing laser power or temperature, and a minimum band bending of ˜0.8 eV is established in both cases. The sub-band gap photo-excitation mechanism is under further investigation, although it appears likely at present that defect or gap states play a role in the photo-enhanced SEE process. In the meantime, the study demonstrates the ability of visible light to modify the electronic properties of diamond and enhance the emission capabilities, which may have potential impact for diamond-based vacuum electron

  16. Fast transient analysis and first-stage collision-induced dissociation with the flowing atmospheric-pressure afterglow ionization source to improve analyte detection and identification.

    PubMed

    Shelley, Jacob T; Hieftje, Gary M

    2010-04-01

    The recent development of ambient desorption/ionization mass spectrometry (ADI-MS) has enabled fast, simple analysis of many different sample types. The ADI-MS sources have numerous advantages, including little or no required sample pre-treatment, simple mass spectra, and direct analysis of solids and liquids. However, problems of competitive ionization and limited fragmentation require sample-constituent separation, high mass accuracy, and/or tandem mass spectrometry (MS/MS) to detect, identify, and quantify unknown analytes. To maintain the inherent high throughput of ADI-MS, it is essential for the ion source/mass analyzer combination to measure fast transient signals and provide structural information. In the current study, the flowing atmospheric-pressure afterglow (FAPA) ionization source is coupled with a time-of-flight mass spectrometer (TOF-MS) to analyze fast transient signals (<500 ms FWHM). It was found that gas chromatography (GC) coupled with the FAPA source resulted in a reproducible (<5% RSD) and sensitive (detection limits of <6 fmol for a mixture of herbicides) system with analysis times of ca. 5 min. Introducing analytes to the FAPA in a transient was also shown to significantly reduce matrix effects caused by competitive ionization by minimizing the number and amount of constituents introduced into the ionization source. Additionally, MS/MS with FAPA-TOF-MS, enabling analyte identification, was performed via first-stage collision-induced dissociation (CID). Lastly, molecular and structural information was obtained across a fast transient peak by modulating the conditions that caused the first-stage CID. PMID:20349535

  17. MAXI/GSC detection of a new soft X-ray transient MAXI J0758-456

    NASA Astrophysics Data System (ADS)

    Nakagawa, Y. E.; Negoro, H.; Ueno, S.; Tomida, H.; Nakahira, S.; Ishikawa, M.; Sugawara, Y.; Mihara, T.; Sugizaki, M.; Serino, M.; Shidatsu, M.; Iwakiri, W.; Sugimoto, J.; Takagi, T.; Matsuoka, M.; Kawai, N.; Isobe, N.; Sugita, S.; Yoshii, T.; Tachibana, Y.; Ono, Y.; Fujiwara, T.; Yoshida, A.; Sakamoto, T.; Kawakubo, Y.; Nakajima, M.

    2016-04-01

    The MAXI/GSC nova-alert system triggered on a bright uncatalogued X-ray transient source at 15:05:06 UT on 2016 April 24. Preliminary analysis shows the source position at around (R.A., Dec) = (119.58 deg, -45.63 deg) with an typical error of 0.5 deg. A more precise position may be given through the MAXI mailing list.

  18. Gamma ray transients

    NASA Technical Reports Server (NTRS)

    Cline, Thomas L.

    1987-01-01

    The discovery of cosmic gamma ray bursts was made with systems designed at Los Alamos Laboratory for the detection of nuclear explosions beyond the atmosphere. HELIOS-2 was the first gamma ray burst instrument launched; its initial results in 1976, seemed to deepen the mystery around gamma ray transients. Interplanetary spacecraft data were reviewed in terms of explaining the behavior and source of the transients.

  19. Silanones and silanethiones from the reactions of transient silylenes with oxiranes and thiiranes in solution. The direct detection of diphenylsilanethione.

    PubMed

    Kostina, Svetlana S; Leigh, William J

    2011-03-30

    The transient silylenes SiMe(2) and SiPh(2) react with cyclohexene oxide (CHO), propylene oxide (PrO), and propylene sulfide (PrS) in hydrocarbon solvents to form products consistent with the formation of the corresponding transient silanones and silanethiones, respectively. Laser flash photolysis studies show that these reactions proceed via multistep sequences involving the intermediacy of the corresponding silylene-oxirane or -thiirane complexes, which are formed with rate constants close to the diffusion limit in all cases and exhibit UV absorption spectra similar to those of the corresponding complexes with the nonreactive O- and S-donors, tetrahydrofuran and tetrahydrothiophene. The SiMe(2)-PrO and SiPh(2)-PrO complexes both exhibit lifetimes of ca. 300 ns, and are longer-lived than the corresponding complexes with CHO, which are both in the range of 230-240 ns. On the other hand, the silylene-PrS complexes are considerably shorter-lived and vary with silyl substituent; the SiMe(2)-PrS complex decays with the excitation laser pulse (i.e., τ ≤ 25 ns), while the SiPh(2)-PrS complex exhibits τ = 48 ± 3 ns. The decay of the SiPh(2)-PrS complex affords a long-lived transient product exhibiting λ(max) ≈ 275 nm, which has been assigned to diphenylsilanethione (Ph(2)Si═S) on the basis of its second order decay kinetics and absolute rate constants for reaction with methanol, tert-butanol, acetic acid, and n-butyl amine, for which values in the range of 1.4 × 10(8) to 3.2 × 10(9) M(-1) s(-1) are reported. The experimental rate constants for decay of the SiMe(2)-epoxide and -PrS complexes indicate free energy barriers (ΔG(‡)) of ca. 8.5 and ≤7.1 kcal mol(-1) for the rate-determining steps leading to dimethylsilanone and -silanethione, respectively, which are compared to the results of DFT (B3LYP/6-311+G(d,p)) calculations of the reactions of SiH(2) and SiMe(2) with oxirane and thiirane. The calculations predict a stepwise C-O cleavage mechanism

  20. Detection of X-Ray Pulsations from the Be/X-Ray Transient A 0535+26 During a Disc Loss Phase of the Primary

    NASA Technical Reports Server (NTRS)

    Negueruela, Ignacio; Reig, Pablo; Finger, Mark H.; Roche, Paul

    1999-01-01

    Using the RossiXTE experiment, we detect weak X-ray emission from the recurrent Be/X-ray transient A 0535+26 at a time when the optical counterpart V725 Tau displayed H.alpha in absorption, indicating the absence of a circumstellar disc. The X-ray radiation is strongly modulated at the 103.5-s pulse period of the neutron star, confirming that it originates from A 0535+26. The source is weaker than in previous quiescence detections by two orders of magnitude and should be in the centrifugal inhibition regime. We show that the X-ray luminosity cannot be due to accretion on to the magnetosphere of the neutron star. Therefore this detection represents a new state of the accreting pulsar. We speculate that the X-ray emission can be due to some matter leaking through the magnetospheric barrier or thermal radiation from the neutron star surface due to crustal heating. The detection of the X-ray source in the inhibition regime implies a reduced density in the outflow from the Be companion during its disc-less phase.

  1. Transient performance

    NASA Astrophysics Data System (ADS)

    Curnock, Barry

    Gas turbine engine transient behavior, that which is concerned with the changes in engine parameters during acceleration or decceleration of an engine from one steady state point to a different steady state point, is considered. An engine can also experience cyclic aerodynamic phenomena which occur at a nominally steady condition; examples are compressor rotator stall and intake or afterburner buzz. The following are discussed: certification requirements; mechanism of acceleration; compressor working lines and surge; and some important factors (pressure level, moment of inertia, heat soakage, clearances, measurement of transients, thrust reversal, and transient maneuvers which involve significant changes to the shaft speeds of the engine). A set of graphics illustrating transient performance is presented.

  2. 10 micron detection of the hard X-ray transient GRO J0422+32: Free-free emission from an X-ray-driven accretion disk wind?

    NASA Technical Reports Server (NTRS)

    Paradijs, Van J.; Telesco, C. M.; Kouveliotou, C.; Fishman, G. J.

    1994-01-01

    We report the detection of 10 micrometer emission from the transient low-mass X-ray binary (LMXB) and optical nova GRO J0422+32 near the maximum of its outburst. We discuss this result in terms of (1) a 'standard' model according to which low-energy radiation of LMXB is caused by reprocessing of X-rays in an accretion disk; (2) emission from a cool secondary star; (3) emission from dust grains heated by the transient X-rays, and (4) free-free emission from an X-ray-driven wind from the accretion disk. Only the fourth alternative provides a viable explanation for the observed 10 micrometer emission, with a mass-loss rate in the disk wind that may be substantially higher than the rate of accretion onto the compact star. The presence of such a wind may have a profound effect on the evolution of the binary, and contribute to the solution of the 'birthrate problem' of millisecond ratio pulsars.

  3. Monitoring radiation belt particle precipitation - automatic detection of enhanced transient ionisation in the lower plasmasphere using subionospheric narrow band VLF signals

    NASA Astrophysics Data System (ADS)

    Steinbach, P.; Lichtenberger, J.; Ferencz, Cs.

    2009-04-01

    Signals of naval VLF transmitters, propagating long distances along the Earth-ionosphere waveguide (EIWG) have been widely applied as effective tools for monitoring transient ionization at mesospheric altitudes. Perturbations in recorded amplitude and/or phase data series of stable frequency signals may refer to the effect of transient enhanced ionization in the EIWG, due to e.g. loss-cone precipitation of trapped energetic electrons (Carpenter et al., 1984, Dowden and Adams, 1990), burst of solar plasma particles (Clilverd et al., 2001). The contribution of precipitating particles are thought to be substantial in certain Sun-to-Earth energy flow processes in the upper atmosphere (Rodger et al., 2005). Narrow band VLF measuring network has been set up, developed and operated in Hungary, running in the last decade almost continuously, dedicated to monitor ionization enhancement regions along numerous transmitter-receiver paths. This setup is based on Omnipal and Ultra-MSK equipment, logging amplitude and phase data of received signals, sampled at frequencies of selected VLF transmitters. Signal trajectories, selected for recording represent proper configuration to survey transient ionization caused by energetic particles in the sub-polar region, such as effect of scattered particles of the inner radiation belt. Reprocessing of the mass archived recordings has been started using a newly developed signal processing code, detecting and classifying different sort of perturbations automatically on narrow band VLF series. Occurrence rates, daily and seasonal variation, statistics of transient ionization enhancements, their geographic distribution within the surveyed range and time period, and correlation with intense geomagnetic and/or Solar event is yielded by this analysis. References: Carpenter, D.L., Inan, U.S., Trimpi, M.L., Helliwell, R.A., and Katsufrakis, J.P.: Perturbations of subionospheric LF and MF signals due to whistler-induced electron precipitation burst

  4. Evaluation of near-infrared tunable diode lasers for detection of transient emissions from a rotary kiln.

    SciTech Connect

    Shaddix, Christopher R.; Ottesen, David K.; Allendorf, Sarah W.; Miller, C. Andy; Lemieux, Paul M.

    2003-12-01

    Near-infrared tunable diode lasers (TDLs) were evaluated for their suitability as fast-response combustion performance indicators during tests at the U.S. Environmental Protection Agency's pilot-scale Rotary Kiln Incinerator Simulator (RKIS) facility. Transient emissions (i.e., 'puffs') of various magnitudes and duration were generated by injecting a mixture of toluene and methylene chloride into the rotary kiln, through use of a computer-controlled liquid gun or by ram-loading containers of the waste surrogate adsorbed onto corncob. Two wavelength-modulated TDLs that span carbon monoxide (CO) and methane absorption lines at 1.57 and 1.65 pm, respectively, provided information on these species as well as total laser transmittance (an indicator of soot loading). Fiber-optic cables transmitted the laser light from the remotely situated TDLs to two line-of-sight measurement locations. In addition, the TDLs were used with a multi-pass optical cell to perform more sensitive extractive measurements. Over the optical pathlength available in this facility, in situ measurements of methane down to a concentration of {approx} 100 ppm were demonstrated during non-sooty conditions. CO could not be reliably quantified in situ, even at concentrations as high as 0.7%, due to the combination of weak absorption line strength and interfering water and carbon-dioxide hot-bands. The soot produced during the toluene/methylene chloride puffs typically attenuated over 90% of the TDL laser beam, preventing effective in situ TDL measurements during the puffs. In contrast, the extractive TDL measurements demonstrated good accuracy and sensitivity for both methane and CO under all reactor conditions. Furthermore, the in situ laser transmittance profiles during the puffs provided new insights into the composition of the puffs as a function of puff magnitude and residence time.

  5. The LOFAR Transients Pipeline

    NASA Astrophysics Data System (ADS)

    Swinbank, John D.; Staley, Tim D.; Molenaar, Gijs J.; Rol, Evert; Rowlinson, Antonia; Scheers, Bart; Spreeuw, Hanno; Bell, Martin E.; Broderick, Jess W.; Carbone, Dario; Garsden, Hugh; van der Horst, Alexander J.; Law, Casey J.; Wise, Michael; Breton, Rene P.; Cendes, Yvette; Corbel, Stéphane; Eislöffel, Jochen; Falcke, Heino; Fender, Rob; Grießmeier, Jean-Mathias; Hessels, Jason W. T.; Stappers, Benjamin W.; Stewart, Adam J.; Wijers, Ralph A. M. J.; Wijnands, Rudy; Zarka, Philippe

    2015-06-01

    Current and future astronomical survey facilities provide a remarkably rich opportunity for transient astronomy, combining unprecedented fields of view with high sensitivity and the ability to access previously unexplored wavelength regimes. This is particularly true of LOFAR, a recently-commissioned, low-frequency radio interferometer, based in the Netherlands and with stations across Europe. The identification of and response to transients is one of LOFAR's key science goals. However, the large data volumes which LOFAR produces, combined with the scientific requirement for rapid response, make automation essential. To support this, we have developed the LOFAR Transients Pipeline, or TraP. The TraP ingests multi-frequency image data from LOFAR or other instruments and searches it for transients and variables, providing automatic alerts of significant detections and populating a lightcurve database for further analysis by astronomers. Here, we discuss the scientific goals of the TraP and how it has been designed to meet them. We describe its implementation, including both the algorithms adopted to maximize performance as well as the development methodology used to ensure it is robust and reliable, particularly in the presence of artefacts typical of radio astronomy imaging. Finally, we report on a series of tests of the pipeline carried out using simulated LOFAR observations with a known population of transients.

  6. Transient isotachophoresis-capillary zone electrophoresis with contactless conductivity and ultraviolet detection for the analysis of paralytic shellfish toxins in mussel samples.

    PubMed

    Abdul Keyon, Aemi S; Guijt, Rosanne M; Bolch, Christopher J S; Breadmore, Michael C

    2014-10-17

    The accumulation of paralytic shellfish toxins (PSTs) in contaminated shellfish is a serious health risk making early detection important to improve shellfish safety and biotoxin management. Capillary electrophoresis (CE) has been proven as a high resolution separation technique compatible with miniaturization, making it an attractive choice in the development of portable instrumentation for early, on-site detection of PSTs. In this work, capillary zone electrophoresis (CZE) with capacitively coupled contactless conductivity detector (C(4)D) and UV detection were examined with counter-flow transient isotachophoresis (tITP) to improve the sensitivity and deal with the high conductivity sample matrix. The high sodium concentration in the sample was used as the leading ion while l-alanine was used as the terminating electrolyte (TE) and background electrolyte (BGE) in which the toxins were separated. Careful optimization of the injected sample volume and duration of the counter-flow resulted in limit of detections (LODs) ranging from 74.2 to 1020 ng/mL for tITP-CZE-C(4)D and 141 to 461 ng/mL for tITP-CZE-UV, an 8-97 fold reduction compared to conventional CZE. The LODs were adequate for the analysis of PSTs in shellfish samples close to the regulatory limit. Intra-day and inter-day repeatability values (percentage relative standard deviation, n=3) of tITP-CZE-C(4)D and tITP-CZE-UV methods for both migration time and peak height were in the range of 0.82-11% and 0.76-10%, respectively. The developed method was applied to the analysis of a contaminated mussel sample and validated against an Association of Official Analytical Chemists (AOAC)-approved method for PSTs analysis by high performance liquid chromatography (HPLC) with fluorescence detection (FLD) after pre-column oxidation of the sample. The method presented has potential for incorporation in to field-deployable devices for the early detection of PSTs on-site. PMID:25223612

  7. Voxelwise lp-ntPET for detecting localized, transient dopamine release of unknown timing: Sensitivity Analysis and Application to Cigarette Smoking in the PET Scanner

    PubMed Central

    Kim, Su Jin; Sullivan, Jenna M; Wang, Shuo; Cosgrove, Kelly P; Morris, Evan D

    2014-01-01

    The “linear parametric neurotransmitter PET” (lp-ntPET) model estimates time variation in endogenous neurotransmitter levels from dynamic PET data. The pattern of dopamine (DA) change over time may be an important element of the brain's response to addictive substances such as cigarettes or alcohol. We have extended the lp-ntPET model from the original region of interest (ROI) - based implementation to be able to apply the model at the voxel level. The resulting endpoint is a dynamic image, or movie, of transient neurotransmitter changes. Simulations were performed to select threshold values to reduce the false positive rate when applied to real 11C-raclopride PET data. We tested the new voxelwise method on simulated data, and finally, we applied it to 11C-raclopride PET data of subjects smoking cigarettes in the PET scanner. In simulation, the temporal precision of neurotransmitter response was shown to be similar to that of ROI-based lp-ntPET (standard deviation ∼ 3 min). False positive rates for the voxelwise method were well controlled by combining a statistical threshold (the F-test) with a new spatial (cluster-size) thresholding operation. Sensitivity of detection for the new algorithm was greater than 80% for the case of short-lived DA changes that occur in subregions of the striatum as might be the case with cigarette smoking. Finally, in 11C-raclopride PET data, DA movies reveal for the first time that different temporal patterns of the DA response to smoking may exist in different subregions of the striatum. These spatiotemporal patterns of neurotransmitter change created by voxelwise lp-ntPET may serve as novel biomarkers for addiction and/or treatment efficacy. PMID:24700424

  8. Transient Monoplegia as a Result of Unilateral Femoral Artery Ischemia Detected by Multimodal Intraoperative Neuromonitoring in Posterior Scoliosis Surgery: A Case Report.

    PubMed

    Pankowski, Rafal; Roclawski, Marek; Dziegiel, Krzysztof; Ceynowa, Marcin; Mikulicz, Marcin; Mazurek, Tomasz; Kloc, Wojciech

    2016-02-01

    This is to report a case of 16-year-old girl with transient right lower limb monoplegia as a result of femoral artery ischemia detected by multimodal intraoperative spinal cord neuromonitoring (MISNM) during posterior correction surgery of adolescent idiopathic scoliosis.A patient with a marfanoid body habitus and LENKE IA type scoliosis with the right thoracic curve of 48° of Cobb angle was admitted for posterior spinal fusion from Th6 to L2. After selective pedicle screws instrumentation and corrective maneuvers motor evoked potentials (MEP) began to decrease with no concomitant changes in somato-sensory evoked potentials recordings.The instrumentation was released first partially than completely with rod removal but the patient demonstrated constantly increasing serious neurological motor deficit of the whole right lower limb. Every technical cause of the MEP changes was eliminated and during the wake-up test the right foot was found to be pale and cold with no popliteal and dorsalis pedis pulses palpable. The patient was repositioned and the pelvic pad was placed more cranially. Instantly, the pulse and color returned to the patient's foot. Following MEP recordings showed gradual return of motor function up to the baseline at the end of the surgery, whereas somato-sensory evoked potentials were within normal range through the whole procedure.This case emphasizes the importance of the proper pelvic pad positioning during the complex spine surgeries performed in prone position of the patient. A few cases of neurological complications have been described which were the result of vascular occlusion after prolonged pressure in the inguinal area during posterior scoliosis surgery when the patient was in prone position. If incorrectly interpreted, they would have a significant impact on the course of scoliosis surgery. PMID:26871822

  9. Evaluation of Transient Elastography, Acoustic Radiation Force Impulse Imaging (ARFI), and Enhanced Liver Function (ELF) Score for Detection of Fibrosis in Morbidly Obese Patients

    PubMed Central

    Karlas, Thomas; Dietrich, Arne; Peter, Veronica; Wittekind, Christian; Lichtinghagen, Ralf; Garnov, Nikita; Linder, Nicolas; Schaudinn, Alexander; Busse, Harald; Prettin, Christiane; Keim, Volker; Tröltzsch, Michael; Schütz, Tatjana; Wiegand, Johannes

    2015-01-01

    Background Liver fibrosis induced by non-alcoholic fatty liver disease causes peri-interventional complications in morbidly obese patients. We determined the performance of transient elastography (TE), acoustic radiation force impulse (ARFI) imaging, and enhanced liver fibrosis (ELF) score for fibrosis detection in bariatric patients. Patients and Methods 41 patients (median BMI 47 kg/m2) underwent 14-day low-energy diets to improve conditions prior to bariatric surgery (day 0). TE (M and XL probe), ARFI, and ELF score were performed on days -15 and -1 and compared with intraoperative liver biopsies (NAS staging). Results Valid TE and ARFI results at day -15 and -1 were obtained in 49%/88% and 51%/90% of cases, respectively. High skin-to-liver-capsule distances correlated with invalid TE measurements. Fibrosis of liver biopsies was staged as F1 and F3 in n = 40 and n = 1 individuals. However, variations (median/range at d-15/-1) of TE (4.6/2.6–75 and 6.7/2.9–21.3 kPa) and ARFI (2.1/0.7–3.7 and 2.0/0.7–3.8 m/s) were high and associated with overestimation of fibrosis. The ELF score correctly classified 87.5% of patients. Conclusion In bariatric patients, performance of TE and ARFI was poor and did not improve after weight loss. The ELF score correctly classified the majority of cases and should be further evaluated. PMID:26528818

  10. Current status of the Explosive Transient Camera. [automated sky survey instument sensitive to optical transients

    NASA Technical Reports Server (NTRS)

    Vanderspek, Roland; Doty, John P.; Ricker, George R.

    1992-01-01

    The current configuration and performance of the Explosive Transient Camera (ETC), a wide-field sky monitor capable of detecting short-timescale optical transients, are briefly reviewed, as are plans for future improvements. The primary objective of the ETC is to detect an optical transient that is spatially and temporally coincident with a gamma-ray burster. However, the ETC is sensitive to all sources of short-timescale optical transients and will conduct a systematic survey of the night sky for all optical transients. Results of preliminary observations of the night sky conducted since January 1991 are summarized, and long-term variability searches with the ETC are discussed.

  11. Transient Faults in Computer Systems

    NASA Technical Reports Server (NTRS)

    Masson, Gerald M.

    1993-01-01

    A powerful technique particularly appropriate for the detection of errors caused by transient faults in computer systems was developed. The technique can be implemented in either software or hardware; the research conducted thus far primarily considered software implementations. The error detection technique developed has the distinct advantage of having provably complete coverage of all errors caused by transient faults that affect the output produced by the execution of a program. In other words, the technique does not have to be tuned to a particular error model to enhance error coverage. Also, the correctness of the technique can be formally verified. The technique uses time and software redundancy. The foundation for an effective, low-overhead, software-based certification trail approach to real-time error detection resulting from transient fault phenomena was developed.

  12. Discovery and Classification of Transients from CRTS-II

    NASA Astrophysics Data System (ADS)

    Drake, A. J.; Djorgovski, S. G.; Mahabal, A. A.; Graham, M. J.; Stern, D.; Catelan, M.; Christensen, E.; Larson, S. M.

    2016-08-01

    Following on from the Catalina Real-time Transient Survey (CRTS), the CRTS-II project has begun to search for transients and highly variable sources. As with CRTS, all detections will be made public immediately following discovery.

  13. Workshop on Radio Transients

    NASA Astrophysics Data System (ADS)

    Croft, Steve; Gaensler, Bryan

    2012-04-01

    abstract-type="normal">SummaryWe are entering a new era in the study of variable and transient radio sources. This workshop discussed the instruments and the strategies employed to study those sources, how they are identified and classified, how results from different surveys can be compared, and how radio observations tie in with those at other wavelengths. The emphasis was on learning what common ground there is between the plethora of on-going projects, how methods and code can be shared, and how best practices regarding survey strategy could be adopted. The workshop featured the four topics below. Each topic commenced with a fairly brief introductory talk, which then developed into discussion. By way of preparation, participants had been invited to upload and discuss one slide per topic to a wiki ahead of the workshop. 1. Telescopes, instrumentation and survey strategy. New radio facilities and on-going projects (including upgrades) are both studying the variability of the radio sky, and searching for transients. The discussion first centred on the status of those facilities, and on projects with a time-domain focus, both ongoing and planned, before turning to factors driving choices of instrumentation, such as phased array versus single pixel feeds, the field of view, spatial and time resolution, frequency and bandwidth, depth, area, and cadence of the surveys. 2. Detection, pipelines, and classification. The workshop debated (a) the factors that influence decisions to study variability in the (u,v) plane, in images, or in catalogues, (b) whether, and how much, pipeline code could potentially be shared between one project and another, and which software packages are best for different approaches, (c) how data are stored and later accessed, and (d) how transients and variables are defined and classified. 3. Statistics, interpretation, and synthesis. It then discussed how (i) the choice of facility and strategy and (ii) detection and classification schemes

  14. Transient Observations with LSST

    NASA Astrophysics Data System (ADS)

    Walkowicz, Lucianne

    2010-12-01

    In the coming decade, LSST';s combination of all-sky coverage, consistent long-term monitoring, and flexible criteria for event identification will revolutionize studies of a wide variety of astrophysical phenomena. The umbrella of time domain science with LSST encompasses objects both familiar and exotic, from classical variables within our Galaxy to explosive cosmological events. LSST will make localization for gravity wave events possible, identify counterparts to GRBs and X-ray flashes, and discover new supernovae. Increased sample sizes of known-but-rare observational phenomena will quantify their distributions for the first time, thus challenging existing theory. Perhaps most excitingly, LSST will provide the opportunity to sample previously untouched regions of parameter space, where transient events are expected on theoretical grounds, but have not yet been observed. LSST will generate "alerts" within 60 seconds of detecting a new transient, permitting the community t o follow up unusual events in greater detail. Here, I highlight some of the scientific opportunities LSST will provide, as well as the challenges we face and opportunities for community involvement.

  15. The Rapid Transient Surveyor

    NASA Astrophysics Data System (ADS)

    Baranec, Christoph; Tonry, John; Wright, Shelley; Tully, R. Brent; Lu, Jessica R.; Takamiya, Marianne Y.; Hunter, Lisa

    2016-01-01

    confirm redshifts of the host galaxies. This unique combination of automated detection and characterization of astrophysical transients during a sustained observing campaign will yield the necessary statistics to precisely map dark matter in the local universe.

  16. Femtosecond Heterodyne Transient Grating Studies of Nonradiative Decay of the S2 (11Bu+) State of Peridinin: Detection and Spectroscopic Assignment of an Sx Intermediate State

    NASA Astrophysics Data System (ADS)

    Ghosh, Soumen; Bishop, Michael M.; Roscioli, Jerome D.; Lafountain, Amy M.; Frank, Harry A.; Beck, Warren F.

    Femtosecond heterodyne transient grating spectroscopy was employed to investigate the nonradiative relaxation dynamics of peridinin from the S2 state to the S1 (21Ag-) state in methanol. A global target analysis indicates that S2 decays in 12 fs to populate an intermediate state, Sx. The absorption and dispersion components of the transient grating signal exhibit a response that is very similar to that of β-carotene in benzonitrile solution. Numerical simulation of the experimental data indicates that the excited state absorption transition from Sx has a larger oscillator strength than that of S1, which rules out an assignment of Sx to a vibrationally excited S1 state. The lifetime of Sx is found to be strongly dependent on the polar solvation timescale. This result indicates that nonradiative decay from Sx to S1 involves large-amplitude torsional motions and a concomitant formation of intramolecular charge transfer character. The present work provides the first evidence that peridinin has an ultrashort S2 lifetime owing to the onset of torsional motions and shows that the Sx acts as an active state for excitation energy transfer to chlorophyll in light-harvesting proteins. Work supported by the Photosynthetic Systems program of U.S. Department of Energy under Award Number DE-SC0010847.

  17. Optical transient monitor

    NASA Astrophysics Data System (ADS)

    Bernas, Martin; Páta, Petr; Hudec, René; Soldán, Jan; Rezek, Tomáš; Castro-Tirado, Alberto J.

    1998-05-01

    Although there are several optical GRB follow-up systems in operation and/or in development, some of them with a very short response time, they will never be able to provide true simultaneous (no delay) and pre-burst optical data for GRBs. We report on the development and tests of a monitoring experiment expected to be put into test operation in 1998. The system should detect Optical Transients down to mag 6-7 (few seconds duration assumed) over a wide field of view. The system is based on the double CCD wide-field cameras ST8. For the real time evaluation of the signal from both cameras, two TMS 320C40 processors are used. Using two channels differing in spectral sensitivity and processing of temporal sequence of images allows us to eliminate man-made objects and defects of the CCD electronics. The system is controlled by a standard PC computer.

  18. Transient tachypnea - newborn

    MedlinePlus

    TTN; Wet lungs - newborns; Retained fetal lung fluid; Transient RDS; Prolonged transition; Neonatal - transient tachypnea ... As the baby grows in the womb, the lungs make a special fluid. This fluid fills the ...

  19. Transient drainage summary report

    SciTech Connect

    1996-09-01

    This report summarizes the history of transient drainage issues on the Uranium Mill Tailings Remedial Action (UMTRA) Project. It defines and describes the UMTRA Project disposal cell transient drainage process and chronicles UMTRA Project treatment of the transient drainage phenomenon. Section 4.0 includes a conceptual cross section of each UMTRA Project disposal site and summarizes design and construction information, the ground water protection strategy, and the potential for transient drainage.

  20. Detecting of transient vibration signatures using an improved fast spatial-spectral ensemble kurtosis kurtogram and its applications to mechanical signature analysis of short duration data from rotating machinery

    NASA Astrophysics Data System (ADS)

    Chen, BinQiang; Zhang, ZhouSuo; Zi, YanYang; He, ZhengJia; Sun, Chuang

    2013-10-01

    Detecting transient vibration signatures is of vital importance for vibration-based condition monitoring and fault detection of the rotating machinery. However, raw mechanical signals collected by vibration sensors are generally mixtures of physical vibrations of the multiple mechanical components installed in the examined machinery. Fault-generated incipient vibration signatures masked by interfering contents are difficult to be identified. The fast kurtogram (FK) is a concise and smart gadget for characterizing these vibration features. The multi-rate filter-bank (MRFB) and the spectral kurtosis (SK) indicator of the FK are less powerful when strong interfering vibration contents exist, especially when the FK are applied to vibration signals of short duration. It is encountered that the impulsive interfering contents not authentically induced by mechanical faults complicate the optimal analyzing process and lead to incorrect choosing of the optimal analysis subband, therefore the original FK may leave out the essential fault signatures. To enhance the analyzing performance of FK for industrial applications, an improved version of fast kurtogram, named as "fast spatial-spectral ensemble kurtosis kurtogram", is presented. In the proposed technique, discrete quasi-analytic wavelet tight frame (QAWTF) expansion methods are incorporated as the detection filters. The QAWTF, constructed based on dual tree complex wavelet transform, possesses better vibration transient signature extracting ability and enhanced time-frequency localizability compared with conventional wavelet packet transforms (WPTs). Moreover, in the constructed QAWTF, a non-dyadic ensemble wavelet subband generating strategy is put forward to produce extra wavelet subbands that are capable of identifying fault features located in transition-band of WPT. On the other hand, an enhanced signal impulsiveness evaluating indicator, named "spatial-spectral ensemble kurtosis" (SSEK), is put forward and utilized

  1. Computed Tomography Imaging Spectrometer (CTIS) with 2D Reflective Grating for Ultraviolet to Long-Wave Infrared Detection Especially Useful for Surveying Transient Events

    NASA Technical Reports Server (NTRS)

    Wilson, Daniel W. (Inventor); Maker, Paul D. (Inventor); Muller, Richard E. (Inventor); Mouroulis, Pantazis Z. (Inventor)

    2003-01-01

    The optical system of this invention is an unique type of imaging spectrometer, i.e. an instrument that can determine the spectra of all points in a two-dimensional scene. The general type of imaging spectrometer under which this invention falls has been termed a computed-tomography imaging spectrometer (CTIS). CTIS's have the ability to perform spectral imaging of scenes containing rapidly moving objects or evolving features, hereafter referred to as transient scenes. This invention, a reflective CTIS with an unique two-dimensional reflective grating, can operate in any wavelength band from the ultraviolet through long-wave infrared. Although this spectrometer is especially useful for events it is also for investigation of some slow moving phenomena as in the life sciences.

  2. Computed tomography imaging spectrometer (CTIS) with 2D reflective grating for ultraviolet to long-wave infrared detection especially useful for surveying transient events

    NASA Technical Reports Server (NTRS)

    Wilson, Daniel W. (Inventor); Maker, Paul D. (Inventor); Muller, Richard E. (Inventor); Mouroulis, Pantazis Z. (Inventor)

    2003-01-01

    The optical system of this invention is an unique type of imaging spectrometer, i.e. an instrument that can determine the spectra of all points in a two-dimensional scene. The general type of imaging spectrometer under which this invention falls has been termed a computed-tomography imaging spectrometer (CTIS). CTIS's have the ability to perform spectral imaging of scenes containing rapidly moving objects or evolving features, hereafter referred to as transient scenes. This invention, a reflective CTIS with an unique two-dimensional reflective grating, can operate in any wavelength band from the ultraviolet through long-wave infrared. Although this spectrometer is especially useful for rapidly occurring events it is also useful for investigation of some slow moving phenomena as in the life sciences.

  3. Studies of Transient Meteor Activity

    NASA Technical Reports Server (NTRS)

    Jenniskens, Peter M. M.

    2002-01-01

    Meteoroids bombard Earth's atmosphere daily, but occasionally meteor rates increase to unusual high levels when Earth crosses the relatively fresh ejecta of comets. These transient events in meteor activity provide clues about the whereabouts of Earth-threatening long-period comets, the mechanisms of large-grain dust ejection from comets, and the particle composition and size distribution of the cometary ejecta. Observations of these transient events provide important insight in natural processes that determine the large grain dust environment of comets, in natural phenomena that were prevalent during the time of the origin of life, and in processes that determine the hazard of civilizations to large impacts and of man-made satellites to the periodic blizzard of small meteoroids. In this proposal, three tasks form a coherent program aimed at elucidating various aspects of meteor outbursts, with special reference to planetary astronomy and astrobiology. Task 1 was a ground-based effort to observe periods of transient meteor activity. This includes: (1) stereoscopic imaging of meteors during transient meteor events for measurements of particle size distribution, meteoroid orbital dispersions and fluxes; and (2) technical support for Global-MS-Net, a network of amateur-operated automatic counting stations for meteor reflections from commercial VHF radio and TV broadcasting stations, keeping a 24h vigil on the level of meteor activity for the detection of new meteor streams. Task 2 consisted of ground-based and satellite born spectroscopic observations of meteors and meteor trains during transient meteor events for measurements of elemental composition, the presence of organic matter in the meteoroids, and products generated by the interaction of the meteoroid with the atmosphere. Task 3 was an airborne effort to explore the 2000 Leonid meteor outbursts, which are anticipated to be the most significant of transient meteor activity events in the remainder of the

  4. Resonance Raman spectra of transient species of a respiration enzyme detected with an artificial cardiovascular system and Raman/absorption simultaneous measurement system

    NASA Astrophysics Data System (ADS)

    Kitagawa, Teizo; Ogura, Takashi

    1991-05-01

    Developments of our techniques for detecting resonance Ranian spectra of reaction intermediates of cytochroxne oxidase are suiainarized. It is demonstrated that combination of a device for Ranian/absorption simultaneous ineasurenient system with an artificial cardiovascular system enabled us to detect the FeO2 and Fe" O stretching vibrations for intermediates and thus to conclude that compounds A and B have the Fe''1-02 and Fe hexnes respectively. 1.

  5. Femtosecond Heterodyne Transient Grating Detection of Conformational Dynamics in the S0 (11Ag-) State of Carotenoids After Nonradiative Decay of the S2 (11Bu+) State

    NASA Astrophysics Data System (ADS)

    Roscioli, Jerome D.; Ghosh, Soumen; Bishop, Michael M.; Lafountain, Amy M.; Frank, Harry A.; Beck, Warren F.

    Transient grating spectroscopy was used to study the dynamics of nonradiative decay of the S1 (21Ag-) state in ß-carotene and peridinin after optical preparation of the S2) state. The kinetics of the recovery of the absorption and dispersion components of the third-order signal exhibit significantly different time constants. For β-carotene in benzonitrile, the absorption and dispersion recovery time constants are 11.6 and 10.2 ps. For peridinin in methanol, the time constants are 9.9 and 7.4 ps. These results indicate that the initial product of the decay of the S1 state is a conformationally displaced structure. The decay rate for the S1 state and the conformational relaxation rate are both slowed in peridinin as the polarity of the solvent decreases; in ethyl acetate, the conformational relaxation time constant is 45 ps, which rules out a dominant contribution from vibrational cooling. These results indicate that the S1 state develops intramolecular charge transfer character owing to distortions along torsional and out-of-plane coordinates, with a pyramidal structure favored as the most stable conformation. Recovery of the photoselected ground state conformation involves a reverse charge-transfer event followed by relaxation to a planar structure. Work supported by Photosynthetic Systems Program of the U.S. Department of Energy under Grant DE-SC0010847.

  6. Transient ischemic attack presenting in an elderly patient with transient ophthalmic manifestations

    PubMed Central

    Jain, Sparshi; Saxena, Tishu; Singh, Sweta; Singh, Nidhi

    2016-01-01

    Transient ischemic attack (TIA) is a transient neurological deficit of cerebrovascular origin without infarction which may last only for a short period and can have varying presentations. We report a case of 58-year-old male with presenting features of sudden onset transient vertical diplopia and transient rotatory nystagmus which self-resolved within 12 h. Patient had no history of any systemic illness. On investigating, hematological investigations and neuroimaging could not explain these sudden and transient findings. A TIA could possibly explain these sudden and transient ocular findings in our patient. This case report aims to highlight the importance of TIA for ophthalmologists. We must not ignore these findings as these could be warning signs of an impending stroke which may or may not be detected on neuroimaging. Thus, early recognition, primary prevention strategies, and timely intervention are needed. PMID:27433041

  7. Radio transients: an antediluvian review

    NASA Astrophysics Data System (ADS)

    Fender, R. P.; Bell, M. E.

    2011-09-01

    We are at the dawn of a new golden age for radio astronomy, with a new generation of facilities under construction and the global community focused on the Square Kilometre Array as its goal for the next decade. These new facilities offer orders of magnitude improvements in survey speed compared to existing radio telescopes and arrays. Furthermore, the study of transient and variable radio sources, and what they can tell us about the extremes of astrophysics as well as the state of the diffuse intervening media, have been embraced as key science projects for these new facilities. In this paper we review the studies of the populations of radio transients made to date, largely based upon archival surveys. Many of these radio transients and variables have been found in the image plane, and their astrophysical origin remains unclear. We take this population and combine it with sensitivity estimates for the next generation arrays to demonstrate that in the coming decade we may find ourselves detecting 10^5 image plane radio transients per year, providing a vast and rich field of research and an almost limitless set of targets for multi-wavelength follow up.

  8. Direct targeting of risk factors significantly increases the detection of liver cirrhosis in primary care: a cross-sectional diagnostic study utilising transient elastography

    PubMed Central

    Harman, David J; Ryder, Stephen D; James, Martin W; Jelpke, Matthew; Ottey, Dominic S; Wilkes, Emilie A; Card, Timothy R; Aithal, Guruprasad P; Guha, Indra Neil

    2015-01-01

    Objectives To assess the feasibility of a novel diagnostic algorithm targeting patients with risk factors for chronic liver disease in a community setting. Design Prospective cross-sectional study. Setting Two primary care practices (adult patient population 10 479) in Nottingham, UK. Participants Adult patients (aged 18 years or over) fulfilling one or more selected risk factors for developing chronic liver disease: (1) hazardous alcohol use, (2) type 2 diabetes or (3) persistently elevated alanine aminotransferase (ALT) liver function enzyme with negative serology. Interventions A serial biomarker algorithm, using a simple blood-based marker (aspartate aminotransferase:ALT ratio for hazardous alcohol users, BARD score for other risk groups) and subsequently liver stiffness measurement using transient elastography (TE). Main outcome measures Diagnosis of clinically significant liver disease (defined as liver stiffness ≥8 kPa); definitive diagnosis of liver cirrhosis. Results We identified 920 patients with the defined risk factors of whom 504 patients agreed to undergo investigation. A normal blood biomarker was found in 62 patients (12.3%) who required no further investigation. Subsequently, 378 patients agreed to undergo TE, of whom 98 (26.8% of valid scans) had elevated liver stiffness. Importantly, 71/98 (72.4%) patients with elevated liver stiffness had normal liver enzymes and would be missed by traditional investigation algorithms. We identified 11 new patients with definite cirrhosis, representing a 140% increase in the number of diagnosed cases in this population. Conclusions A non-invasive liver investigation algorithm based in a community setting is feasible to implement. Targeting risk factors using a non-invasive biomarker approach identified a substantial number of patients with previously undetected cirrhosis. Trial registration number The diagnostic algorithm utilised for this study can be found on clinicaltrials.gov (NCT02037867), and is

  9. Optical & NIR Transient Surveys

    NASA Astrophysics Data System (ADS)

    Cross, Nicholas J. G.; Djorgovski, S. G.

    2012-04-01

    A workshop on Optical & Near Infrared Transients took place during the first afternoon of the Symposium. It ran for two sessions. The first was given over to talks about various current optical and near-infrared transient surveys, focussing on the Vista surveys, the Catalina Real-Time Transient Survey, Pan-STARRS, Gaia, TAOS and TAOS2. The second session was a panel-led discussion about coordinating multi-wavelength surveys and associated follow-ups.

  10. MAXI/GSC detection of a short X-ray transient MAXI J1714-130 / XRF 150912 and Swift non-detection in XRT follow-up observations

    NASA Astrophysics Data System (ADS)

    Nakajima, M.; Negoro, H.; Mihara, T.; Kennea, J. A.; Arimoto, M.; Ueno, S.; Tomida, H.; Nakahira, S.; Kimura, M.; Ishikawa, M.; Nakagawa, Y. E.; Sugizaki, M.; Serino, M.; Shidatsu, M.; Sugimoto, J.; Takagi, T.; Matsuoka, M.; Kawai, N.; Yoshii, T.; Tachibana, Y.; Ono, Y.; Fujiwara, T.; Yoshida, A.; Sakamoto, T.; Kawakubo, Y.; Ohtsuki, H.; Tsunemi, H.; Imatani, R.; Tanaka, K.; Masumitsu, T.; Ueda, Y.; Kawamuro, T.; Hori, T.; Tsuboi, Y.; Kanetou, S.; Yamauchi, M.; Itoh, D.; Yamaoka, K.: Morii, M.

    2015-09-01

    The MAXI/GSC nova alert system triggered an uncatalogued faint X-ray transient source at UT 2015-09-12 21:03:00 (MJD 57277.8771). Assuming that the source flux was constant over the transit, we obtain the source position at (R.A., Dec) = (258.585 deg, -13.060 deg) = (17 14 20, -13 03 36) (J2000) with a statistical 90% C.L. elliptical error region with long and short radii of 0.41 deg and 0.35 deg, respectively.

  11. (Nitro)Iron(III) Porphyrins. EPR Detection of a Transient Low-Spin Iron(III) Complex and Structural Characterization of an O Atom Transfer Product.

    PubMed

    Munro, Orde Q.; Scheidt, W. Robert

    1998-05-01

    The reaction of BF(3).OEt(2) with the bis(nitro) complex of iron(III) picket-fence porphyrin, [K(18C6)(OH(2))][Fe(TpivPP)(NO(2))(2)], leads to the formation of a transient porphyrin intermediate, assigned on the basis of its rhombic low-spin EPR spectrum as the five-coordinate N-bound mono(nitro) iron(III) derivative, [Fe(TpivPP)(NO(2))]. This species is reactive and readily undergoes oxygen atom transfer to form [Fe(III)(TpivPP)(NO(3))] and [Fe(II)(TpivPP)(NO)]. The reactions have been followed by EPR and IR spectroscopy. [Fe(TpivPP)(NO(2))] has a rhombic EPR spectrum (g = 2.60, 2.35, and 1.75) in chlorobenzene and CH(2)Cl(2) and is spectroscopically distinct from the bis(nitro) starting material (g = 2.70, 2.50, and 1.57). Oxidation of the nitrosyl species to [Fe(TpivPP)(NO(3))] proceeds via an intermediate assigned as [Fe(TpivPP)(NO(2))] on the basis of its EPR spectrum. The crystal structure of one of the reaction products, [Fe(TpivPP)(NO(3))], has been determined. The nitrate ion of [Fe(TpivPP)(NO(3))] is bound to the iron(III) ion in a "symmetric" bidentate fashion within the ligand-binding pocket of the porphyrin pickets. Individual Fe-O distances are 2.123(3) and 2.226(3) Å. The dihedral angle between the plane of the nitrate ion and the closest N(p)-Fe-N(p) plane is 10.0 degrees. The Fe-N(p) bonds (and trans N(p)-Fe-N(p) angles) perpendicular and parallel to the plane of the axial ligand average to 2.060(5) Å (154.84(9) degrees ) and 2.083(3) Å (146.14(9) degrees ), respectively. Crystal data for [Fe(TpivPP)(NO(3))]: a = 23.530(2) Å, b = 10.0822(5) Å, c = 48.748(3) Å, beta = 92.145(5) degrees, monoclinic, space group I2/a, V = 11556.4(14) Å(3), Z = 8, FeN(9)O(7)C(64)H(64), 8798 observed data, R(1) = 0.0606, wR(2) = 0.1313, all observations at 127(2) K. PMID:11670389

  12. Exploring the transient sky: from surveys to simulations

    NASA Astrophysics Data System (ADS)

    Carbone, Dario

    2016-01-01

    The transient sky is very important to study the dynamics of the Universe on human timescales. Transient sources are seen in every band of the electromagnetic spectrum, from low radio frequencies to gamma-ray energies, and produced by nearby flare stars to cosmological gamma-ray bursts.We have performed a transient survey of four different fields with the LOw Frequency Array (LOFAR) at 150 MHz. LOFAR is a new generation radio interferometer which is observing at very low radio frequencies, a so far relatively unexplored frequency domain for transient searches. No credible transients were detected in our survey, but we were able to set stringent upper limits on the transient surface density using three new statistical methods. We also calculated the transient surface density as a function of the timescale of the transients, and established that the upper limits we can set vary up to two orders of magnitude for different timescales.We have explored the complex relation between flux density, timescale and transient surface density, and developed a simulation method to calculate the transient rate as a function of both the flux and the duration of transients for different shapes of their lightcurves and for a given observing strategy. This method is independent of the nature of transient sources, and the instrument or the frequency of the observations. Therefore, this provides a tool for transient surveys carried out by current and future observatories across the electromagnetic spectrum.

  13. Perception of acoustic transients

    NASA Astrophysics Data System (ADS)

    Howard, J. H., Jr.

    1984-01-01

    The research investigates the role of knowledge based or top-down processing in the perception of nonlinguistic, transient signals. The experiments address issues in transient pattern classification, target observation, attentional focusing, auditory induction, and computer based performance aids. The theoretical significance and naval relevance of the research is considered.

  14. Transient Phenomena: Opportunities for New Discoveries

    NASA Astrophysics Data System (ADS)

    Lazio, T. Joseph W.

    Known classes of radio wavelength transients range from the nearby (stellar flares and radio pulsars) to the distant Universe (γ-ray burst afterglows). Hypothesized classes of radio transients include analogs of known objects, such as extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, such as prompt emission from γ-ray bursts, evaporating black holes and transmitters from other civilizations. Time domain astronomy has been recognized internationally as a means of addressing key scientific questions in astronomy and physics, and pathfinders and Precursors to the Square Kilometre Array (SKA) are beginning to offer a combination of wider fields of view and more wavelength agility than has been possible in the past. These improvements will continue when the SKA itself becomes operational. I illustrate the range of transient phenomena and discuss how the detection and study of radio transients will improve immensely.

  15. Transient Phenomena: Opportunities for New Discoveries

    NASA Technical Reports Server (NTRS)

    Lazio, T. Joseph W.

    2010-01-01

    Known classes of radio wavelength transients range from the nearby (stellar flares and radio pulsars) to the distant Universe (gamma-ray burst afterglows). Hypothesized classes of radio transients include analogs of known objects, such as extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, such as prompt emission from gamma-ray bursts, evaporating black holes and transmitters from other civilizations. Time domain astronomy has been recognized internationally as a means of addressing key scientific questions in astronomy and physics, and pathfinders and Precursors to the Square Kilometre Array (SKA) are beginning to offer a combination of wider fields of view and more wavelength agility than has been possible in the past. These improvements will continue when the SKA itself becomes operational. I illustrate the range of transient phenomena and discuss how the detection and study of radio transients will improve immensely.

  16. High-energy transients.

    PubMed

    Gehrels, Neil; Cannizzo, John K

    2013-06-13

    We present an overview of high-energy transients in astrophysics, highlighting important advances over the past 50 years. We begin with early discoveries of γ-ray transients, and then delve into physical details associated with a variety of phenomena. We discuss some of the unexpected transients found by Fermi and Swift, many of which are not easily classifiable or in some way challenge conventional wisdom. These objects are important insofar as they underscore the necessity of future, more detailed studies. PMID:23630376

  17. Transient nucleation in glasses

    NASA Technical Reports Server (NTRS)

    Kelton, K. F.

    1991-01-01

    Nucleation rates in condensed systems are frequently not at their steady state values. Such time dependent (or transient) nucleation is most clearly observed in devitrification studies of metallic and silicate glasses. The origin of transient nucleation and its role in the formation and stability of desired phases and microstructures are discussed. Numerical models of nucleation in isothermal and nonisothermal situations, based on the coupled differential equations describing cluster evolution within the classical theory, are presented. The importance of transient nucleation in glass formation and crystallization is discussed.

  18. Transient fault behavior in a microprocessor: A case study

    NASA Technical Reports Server (NTRS)

    Duba, Patrick

    1989-01-01

    An experimental analysis is described which studies the susceptibility of a microprocessor based jet engine controller to upsets caused by current and voltage transients. A design automation environment which allows the run time injection of transients and the tracing from their impact device to the pin level is described. The resulting error data are categorized by the charge levels of the injected transients by location and by their potential to cause logic upsets, latched errors, and pin errors. The results show a 3 picoCouloumb threshold, below which the transients have little impact. An Arithmetic and Logic Unit transient is most likely to result in logic upsets and pin errors (i.e., impact the external environment). The transients in the countdown unit are potentially serious since they can result in latched errors, thus causing latent faults. Suggestions to protect the processor against these errors, by incorporating internal error detection and transient suppression techniques, are also made.

  19. Radio Counterparts to SXR Transients

    NASA Astrophysics Data System (ADS)

    Gary, D. E.

    1999-12-01

    By now several studies have been done on small-scale brightenings seen at radio, UV, EUV, and soft X-ray wavelengths. These are to be reviewed by Kundu in these proceedings. In this talk we concentrate on the radio counterpart of a particular type of brightening---the soft X-ray transient brightenings of Shimizu. These brightenings are associated with active regions, and a study of radio counterparts by White et al. (1995) using Nobeyama data found an excellent correspondence between the 17 GHz and SXR brightenings, both spatially and temporally. However, this study found that both the SXR and microwave emissions could be satisfactorily explained as purely thermal emission, and a search of BATSE hard X-ray data showed no nonthermal counterpart. White et al. (1995) were forced to conclude that the events may be different from flares. A more sensitive search for nonthermal emission was needed, in particular using lower frequency microwaves where the influence of nonthermal electrons would be more easily detected. Gary, Hartl and Shimizu (1997) found 34 SXR transient brightenings over a 10-day period in May 1992, for which OVRO (1-18 GHz) total power data were available. A comparison of the data showed a number of clear nonthermal signatures. In addition, one of the events was seen in the lowest energy (6-9.3 keV) channel of the BATSE SPEC detector, suggesting a connection between the microflares discovered in hard X-rays by Lin et al. (1984). The evidence that SXR transient brightenings are microflares is reviewed in this talk. We also attempt to place other small-scale brightenings in context with regard to SXR transient brightenings and microflares.

  20. High energy transients

    NASA Technical Reports Server (NTRS)

    Woosley, S. E.

    1984-01-01

    A meeting was convened on the campus of the University of California at Santa Cruz during the two-week interval July 11 through July 22, 1983. Roughly 100 participants were chosen so as to give broad representation to all aspects of high energy transients. Ten morning review sessions were held in which invited speakers discussed the current status of observations and theory of the above subjects. Afternoon workshops were also held, usually more than one per day, to informally review various technical aspects of transients, confront shortcomings in theoretical models, and to propose productive courses for future research. Special attention was also given to the instrumentation used to study high energy transient and the characteristics and goals of a dedicated space mission to study transients in the next decade were determined. A listing of articles written by various members of the workshop is included.

  1. Searching for Low-Frequency Radio Transients from Supernovae

    NASA Astrophysics Data System (ADS)

    Tsai-Wei, Jr.; Cutchin, Sean; Kothari, Manthan; Schmitt, Christian; Kavic, Michael; Simonetti, John

    2011-10-01

    Supernovae events may be accompanied by prompt emission of a low-frequency electromagnetic transient. These transient events are created by the interaction of a shock wave of charged particles created by SN core-collapse with a stars ambient magnetic field. Such events can be detected in low-frequency radio array. Here we discuss an ongoing search for such events using two radio arrays: the Long Wavelength Array (LWA) and Eight-meter-wavelength Transient Array (ETA).

  2. Laser-induced transient grating setup with continuously tunable period

    SciTech Connect

    Vega-Flick, A.; Eliason, J. K.; Maznev, A. A.; Nelson, K. A.; Khanolkar, A.; Abi Ghanem, M.; Boechler, N.; Alvarado-Gil, J. J.

    2015-12-15

    We present a modification of the laser-induced transient grating setup enabling continuous tuning of the transient grating period. The fine control of the period is accomplished by varying the angle of the diffraction grating used to split excitation and probe beams. The setup has been tested by measuring dispersion of bulk and surface acoustic waves in both transmission and reflection geometries. The presented modification is fully compatible with optical heterodyne detection and can be easily implemented in any transient grating setup.

  3. Apparatus Characterizes Transient Voltages in Real Time

    NASA Technical Reports Server (NTRS)

    Medelius, Pedro

    2005-01-01

    The figure shows a prototype of a relatively inexpensive electronic monitoring apparatus that measures and records selected parameters of lightning-induced transient voltages on communication and power cables. The selected parameters, listed below, are those most relevant to the ability of lightning-induced transients to damage electronic equipment. This apparatus bridges a gap between some traditional transient-voltage recorders that record complete waveforms and other traditional transient-voltage recorders that record only peak values: By recording the most relevant parameters and only those parameters this apparatus yields more useful information than does a traditional peak-value (only) recorder while imposing much smaller data-storage and data-transmission burdens than does a traditional complete-waveform recorder. Also, relative to a complete-waveform recorder, this apparatus is more reliable and can be built at lower cost because it contains fewer electronic components. The transients generated by sources other than lightning tend to have frequency components well below 1 MHz. Most commercial transient recorders can detect and record such transients, but cannot respond rapidly enough for recording lightning-induced transient voltage peaks, which can rise from 10 to 90 percent of maximum amplitude in a fraction of a microsecond. Moreover, commercial transient recorders cannot rearm themselves rapidly enough to respond to the multiple transients that occur within milliseconds of each other on some lightning strikes. One transient recorder, designed for Kennedy Space Center earlier [ Fast Transient-Voltage Recorder (KSC- 11991), NASA Tech Briefs, Vol. 23, No. 10, page 6a (October 1999)], is capable of sampling transient voltages at peak values up to 50 V in four channels at a rate of 20 MHz. That recorder contains a trigger circuit that continuously compares the amplitudes of the signals on four channels to a preset triggering threshold. When a trigger signal

  4. Transient Tsunamis in Lakes

    NASA Astrophysics Data System (ADS)

    Couston, L.; Mei, C.; Alam, M.

    2013-12-01

    A large number of lakes are surrounded by steep and unstable mountains with slopes prone to failure. As a result, landslides are likely to occur and impact water sitting in closed reservoirs. These rare geological phenomena pose serious threats to dam reservoirs and nearshore facilities because they can generate unexpectedly large tsunami waves. In fact, the tallest wave experienced by contemporary humans occurred because of a landslide in the narrow bay of Lituya in 1958, and five years later, a deadly landslide tsunami overtopped Lake Vajont's dam, flooding and damaging villages along the lakefront and in the Piave valley. If unstable slopes and potential slides are detected ahead of time, inundation maps can be drawn to help people know the risks, and mitigate the destructive power of the ensuing waves. These maps give the maximum wave runup height along the lake's vertical and sloping boundaries, and can be obtained by numerical simulations. Keeping track of the moving shorelines along beaches is challenging in classical Eulerian formulations because the horizontal extent of the fluid domain can change over time. As a result, assuming a solid slide and nonbreaking waves, here we develop a nonlinear shallow-water model equation in the Lagrangian framework to address the problem of transient landslide-tsunamis. In this manner, the shorelines' three-dimensional motion is part of the solution. The model equation is hyperbolic and can be solved numerically by finite differences. Here, a 4th order Runge-Kutta method and a compact finite-difference scheme are implemented to integrate in time and spatially discretize the forced shallow-water equation in Lagrangian coordinates. The formulation is applied to different lake and slide geometries to better understand the effects of the lake's finite lengths and slide's forcing mechanism on the generated wavefield. Specifically, for a slide moving down a plane beach, we show that edge-waves trapped by the shoreline and free

  5. Transient Alerts in LSST

    NASA Astrophysics Data System (ADS)

    Kantor, J.

    During LSST observing, transient events will be detected and alerts generated at the LSST Archive Center at NCSA in Champaign-Illinois. As a very high rate of alerts is expected, approaching ˜ 10 million per night, we plan for VOEvent-compliant Distributor/Brokers (http://voevent.org) to be the primary end-points of the full LSST alert streams. End users will then use these Distributor/Brokers to classify and filter events on the stream for those fitting their science goals. These Distributor/Brokers are envisioned to be operated as a community service by third parties who will have signed MOUs with LSST. The exact identification of Distributor/Brokers to receive alerts will be determined as LSST approaches full operations and may change over time, but it is in our interest to identify and coordinate with them as early as possible. LSST will also operate a limited Distributor/Broker with a filtering capability at the Archive Center, to allow alerts to be sent directly to a limited number of entities that for some reason need to have a more direct connection to LSST. This might include, for example, observatories with significant follow-up capabilities whose observing may temporarily be more directly tied to LSST observing. It will let astronomers create simple filters that limit what alerts are ultimately forwarded to them. These user defined filters will be possible to specify using an SQL-like declarative language, or short snippets of (likely Python) code. We emphasize that this LSST-provided capability will be limited, and is not intended to satisfy the wide variety of use cases that a full-fledged public Event Distributor/Broker could. End users will not be able to subscribe to full, unfiltered, alert streams coming directly from LSST. In this session, we will discuss anticipated LSST data rates, and capabilities for alert processing and distribution/brokering. We will clarify what the LSST Observatory will provide versus what we anticipate will be a

  6. Ischemia detection by electrocardiogram in wavelet domain using entropy measure

    PubMed Central

    Rabbani, Hossein; Mahjoob, Mohammad Parsa; Farahabadi, Eiman; Farahabadi, Amin; Dehnavi, Alireza Mehri

    2011-01-01

    BACKGROUND: Ischemic heart disease is one of the common fatal diseases in advanced countries. Because signal perturbation in healthy people is less than signal perturbation in patients, entropy measure can be used as an appropriate feature for ischemia detection. METHODS: Four entropy-based methods comprising of using electrocardiogram (ECG) signal directly, wavelet sub-bands of ECG signals, extracted ST segments and reconstructed signal from time-frequency feature of ST segments in wavelet domain were investigated to distinguish between ECG signal of healthy individuals and patients. We used exercise treadmill test as a gold standard, with a sample of 40 patients who had ischemic signs based on initial diagnosis of medical practitioner. RESULTS: The suggested technique in wavelet domain resulted in the highest discrepancy between healthy individuals and patients in comparison to other methods. Specificity and sensitivity of this method were 95% and 94% respectively. CONCLUSIONS: The method based on wavelet sub-bands outperformed the others. PMID:22973350

  7. The Transient Universe

    NASA Astrophysics Data System (ADS)

    Shappee, Benjamin John

    When one looks at the night sky, one usually gets the impression of a static and constant universe. Quite apart from appearances, the sky is teeming with violent, variable, and transient events that shape our universe. These capricious objects are not only penetrating probes into physical conditions too extreme for earthbound laboratories, but they are also useful tools to measure the universe. In this dissertation, I investigate the observational and theoretical properties of three classes of transient/variable objects: thermonuclear supernovae, Cepheid variable stars, and active galactic nuclei.

  8. Transient Uncoupling Induces Synchronization.

    PubMed

    Schröder, Malte; Mannattil, Manu; Dutta, Debabrata; Chakraborty, Sagar; Timme, Marc

    2015-07-31

    Finding conditions that support synchronization is a fertile and active area of research with applications across multiple disciplines. Here we present and analyze a scheme for synchronizing chaotic dynamical systems by transiently uncoupling them. Specifically, systems coupled only in a fraction of their state space may synchronize even if fully coupled they do not. While for many standard systems coupling strengths need to be bounded to ensure synchrony, transient uncoupling removes this bound and thus enables synchronization in an infinite range of effective coupling strengths. The presented coupling scheme therefore opens up the possibility to induce synchrony in (biological or technical) systems whose parameters are fixed and cannot be modified continuously. PMID:26274420

  9. Transient Uncoupling Induces Synchronization

    NASA Astrophysics Data System (ADS)

    Schröder, Malte; Mannattil, Manu; Dutta, Debabrata; Chakraborty, Sagar; Timme, Marc

    2015-07-01

    Finding conditions that support synchronization is a fertile and active area of research with applications across multiple disciplines. Here we present and analyze a scheme for synchronizing chaotic dynamical systems by transiently uncoupling them. Specifically, systems coupled only in a fraction of their state space may synchronize even if fully coupled they do not. While for many standard systems coupling strengths need to be bounded to ensure synchrony, transient uncoupling removes this bound and thus enables synchronization in an infinite range of effective coupling strengths. The presented coupling scheme therefore opens up the possibility to induce synchrony in (biological or technical) systems whose parameters are fixed and cannot be modified continuously.

  10. Transient astronomy with the Gaia satellite.

    PubMed

    Hodgkin, Simon T; Wyrzykowski, Łukasz; Blagorodnova, Nadejda; Koposov, Sergey

    2013-06-13

    Gaia is a cornerstone European Space Agency astrometry space mission and a successor to the Hipparcos mission. Gaia will observe the whole sky for 5 years, providing a serendipitous opportunity for the discovery of large numbers of transient and anomalous events, e.g. supernovae, novae and microlensing events, gamma-ray burst afterglows, fallback supernovae, as well as theoretical or unexpected phenomena. In this paper, we discuss our preparations to use Gaia to search for transients at optical wavelengths, and briefly describe the early detection, classification and prompt publication of anomalous sources. PMID:23630374

  11. Intermittent/transient fault phenomena in digital systems

    NASA Technical Reports Server (NTRS)

    Masson, G. M.

    1977-01-01

    An overview of the intermittent/transient (IT) fault study is presented. An interval survivability evaluation of digital systems for IT faults is discussed along with a method for detecting and diagnosing IT faults in digital systems.

  12. Rotor transient analysis

    NASA Technical Reports Server (NTRS)

    Allaire, P. E.; Choy, K. C.; Gunter, E. J.

    1980-01-01

    Undamped modes approximate dynamic behavior of rotors and bearings. Application of modal analysis to uncouple equations of motion simplifies stability, steady-state unbalance response, and transient response analysis of system; nonlinear stability is predicted from calculated frequency spectra. Analysis provides designers with complete information without involving large-scale computational costs. Programs are written in FORTRAN IV for use on CDC 6600 computer.

  13. Measuring Transient Memory Load

    ERIC Educational Resources Information Center

    Wanner, Eric; Shiner, Sandra

    1976-01-01

    Two experiments are reported in which subjects performed simple mental arithmetic problems which were presented visually in a sequential fashion. At some point in the presentation of each problem, the sequential display was interrupted and a memory task introduced. The purpose was to validate a measure of transient memory load. (Author/RM)

  14. Ultrafast transient absorption measurements of heme proteins

    NASA Astrophysics Data System (ADS)

    Ye, Xiong; Demidov, Andrey; Wang, Wei; Christian, James; Champion, Paul

    1998-03-01

    Transient absorption spectra reveal the dynamics and intermediate states of the heme active site after ligand photodissociation, which helps clarify the physical process of ligand dissociation and geminate recombination. To measure the transient absorption spectra, we apply a femtosecond pump-probe technique with frequency resolved detection using a multichannel diode array. The femtosecond pulse output from a regenerative laser amplifier system is split in two; one beam pumps the optical parametric amplifier to produce a tunable wavelength pump pulse, the other beam generates a white light continuum that is varied in time with respect to pump pulse and probe the transient absorbance of the sample. We make a comparative study of myoglobin with different ligands, mutants and pH conditions.

  15. Radio wavelength transients: Current and emerging prospects

    NASA Astrophysics Data System (ADS)

    Lazio, J.

    2008-03-01

    Known classes of radio wavelength transients range from the nearby stellar flares and radio pulsars to the distant Universe γ-ray burst afterglows. Hypothesized classes of radio transients include analogs of known objects, e.g., extrasolar planets emitting Jovian-like radio bursts and giant-pulse emitting pulsars in other galaxies, to the exotic, prompt emission from γ-ray bursts, evaporating black holes, and transmitters from other civilizations. A number of instruments and facilities are either under construction or in early observational stages and are slated to become available in the next few years. With a combination of wide fields of view and wavelength agility, the detection and study of radio transients will improve immensely.

  16. Turbofan compressor dynamics during afterburner transients

    NASA Technical Reports Server (NTRS)

    Kurkov, A. P.

    1976-01-01

    The effects of afterburner light-off and shut-down transients on the compressor stability are investigated. The reported experimental results are based on detailed high response pressure and temperature measurements on the TF30-P-3 turbofan engine. The tests were performed in an altitude test chamber simulating high altitude engine operation. It is shown that during both types of transients, flow breaks down in the forward part of the fan bypass duct. At a sufficiently low engine inlet pressure this resulted in a compressor stall. Complete flow breakdown within the compressor was preceded by a rotating stall. At some locations in the compressor, rotating stall cells initially extended only through part of the blade span. For the shutdown transient the time between first and last detected occurrence of rotating stall is related to the flow Reynolds number. An attempt was made to deduce the number and speed of propagation of rotating stall cells.

  17. Turbofan compressor dynamics during afterburner transients

    NASA Technical Reports Server (NTRS)

    Kurkov, A. P.

    1975-01-01

    The effects of afterburner light-off and shut-down transients on the compressor stability are investigated. The reported experimental results are based on detailed high-response pressure and temperature measurements on the TF30-P-3 turbofan engine. The tests were performed in an altitude test chamber simulating high-altitude engine operation. It is shown that during both types of transients, flow breaks down in the forward part of the fan-bypass duct. At a sufficiently low engine inlet pressure this resulted in a compressor stall. Complete flow breakdown within the compressor was preceded by a rotating stall. At some locations in the compressor, rotating stall cells initially extended only through part of the blade span. For the shut-down transient the time between first and last detected occurrence of rotating stall is related to the flow Reynolds number. An attempt was made to deduce the number and speed of propagation of rotating stall cells.

  18. Turbofan compressor dynamics during afterburner transients

    NASA Technical Reports Server (NTRS)

    Kurkov, A. P.

    1975-01-01

    The effects of afterburner light-off and shut-down transients on compressor stability were investigated. Experimental results are based on detailed high-response pressure and temperature measurements on the Tf30-p-3 turbofan engine. The tests were performed in an altitude test chamber simulating high-altitude engine operation. It is shown that during both types of transients, flow breaks down in the forward part of the fan-bypass duct. At a sufficiently low engine inlet pressure this resulted in a compressor stall. Complete flow breakdown within the compressor was preceded by a rotating stall. At some locations in the compressor, rotating stall cells initially extended only through part of the blade span. For the shutdown transient, the time between first and last detected occurrence of rotating stall is related to the flow Reynolds number. An attempt was made to deduce the number and speed of propagation of rotating stall cells.

  19. Interpreting signals from astrophysical transient experiments

    PubMed Central

    O’Brien, Paul T.; Smartt, Stephen J.

    2013-01-01

    Time-domain astronomy has come of age with astronomers now able to monitor the sky at high cadence, both across the electromagnetic spectrum and using neutrinos and gravitational waves. The advent of new observing facilities permits new science, but the ever-increasing throughput of facilities demands efficient communication of coincident detections and better subsequent coordination among the scientific community so as to turn detections into scientific discoveries. To discuss the revolution occurring in our ability to monitor the Universe and the challenges it brings, on 25–26 April 2012, a group of scientists from observational and theoretical teams studying transients met with representatives of the major international transient observing facilities at the Kavli Royal Society International Centre, UK. This immediately followed the Royal Society Discussion Meeting ‘New windows on transients across the Universe’ held in London. Here, we present a summary of the Kavli meeting at which the participants discussed the science goals common to the transient astronomy community and analysed how to better meet the challenges ahead as ever more powerful observational facilities come on stream. PMID:23630383

  20. Interpreting signals from astrophysical transient experiments.

    PubMed

    O'Brien, Paul T; Smartt, Stephen J

    2013-06-13

    Time-domain astronomy has come of age with astronomers now able to monitor the sky at high cadence, both across the electromagnetic spectrum and using neutrinos and gravitational waves. The advent of new observing facilities permits new science, but the ever-increasing throughput of facilities demands efficient communication of coincident detections and better subsequent coordination among the scientific community so as to turn detections into scientific discoveries. To discuss the revolution occurring in our ability to monitor the Universe and the challenges it brings, on 25-26 April 2012, a group of scientists from observational and theoretical teams studying transients met with representatives of the major international transient observing facilities at the Kavli Royal Society International Centre, UK. This immediately followed the Royal Society Discussion Meeting 'New windows on transients across the Universe' held in London. Here, we present a summary of the Kavli meeting at which the participants discussed the science goals common to the transient astronomy community and analysed how to better meet the challenges ahead as ever more powerful observational facilities come on stream. PMID:23630383

  1. The VAO Transient Facility

    NASA Astrophysics Data System (ADS)

    Graham, Matthew J.; Djorgovski, S. G.; Drake, Andrew; Mahabal, Ashish; Williams, Roy; Seaman, Rob

    2012-04-01

    The time-domain community wants robust and reliable tools to enable the production of, and subscription to, community-endorsed event notification packets (VOEvent). The Virtual Astronomical Observatory (VAO) Transient Facility (VTF) is being designed to be the premier brokering service for the community, both collecting and disseminating observations about time-critical astronomical transients but also supporting annotations and the application of intelligent machine-learning to those observations. Two types of activity associated with the facility can therefore be distinguished: core infrastructure, and user services. We review the prior art in both areas, and describe the planned capabilities of the VTF. In particular, we focus on scalability and quality-of-service issues required by the next generation of sky surveys such as LSST and SKA.

  2. Transient neonatal zinc deficiency.

    PubMed

    Krieger, I; Alpern, B E; Cunnane, S C

    1986-06-01

    We report an infant who developed clinical manifestations of zinc deficiency during the first month of life although the diet was adequate for zinc and no other causes could be ascertained. The diagnosis was confirmed by low plasma-zinc concentrations and a positive response to zinc treatment. The fatty acid profile of plasma phospholipids was typical of zinc deficiency (ie, arachidonic acid was markedly decreased). The transient nature of this disorder was evident when no relapse occurred after cessation of zinc therapy and plasma-zinc and arachidonic acid concentrations remained normal. Several explanations for the development of transient neonatal zinc deficiency are offered. The observation demonstrates that occasional infants may have requirements for zinc that are beyond the intakes of the conventional RDA. PMID:3717070

  3. Transient infrared emission spectroscopy

    SciTech Connect

    Jones, R.W.; McClelland, J.F.

    1989-04-01

    Transient infrared emission spectroscopy (TIRES) is a new method that produces analytically useful emission spectra from optically thick, solid samples by greatly reducing self-absorption of emitted radiation. The method reduces self-absorption by creating a thin, short-lived, heated layer at the sample surface and collecting the transient emission from this layer. The technique requires no sample preparation and may be applied to both moving and stationary samples. The single-ended, noncontact TIRES measurement geometry is ideal for on-line and other remote-sensing applications. TIRES spectra acquired via a Fourier transform infrared spectrometer on moving samples of coal, plastic, and paint are presented and compared to photoacoustic absorption spectra of these materials. The TIRES and photoacoustic results are in close agreement as predicted by Kirchhoff's law.

  4. Reactor System Transient Code.

    Energy Science and Technology Software Center (ESTSC)

    1999-07-14

    RELAP3B describes the behavior of water-cooled nuclear reactors during postulated accidents or power transients, such as large reactivity excursions, coolant losses or pump failures. The program calculates flows, mass and energy inventories, pressures, temperatures, and steam qualities along with variables associated with reactor power, reactor heat transfer, or control systems. Its versatility allows one to describe simple hydraulic systems as well as complex reactor systems.

  5. Two Transients discovered by PSST

    NASA Astrophysics Data System (ADS)

    Smith, K. W.; Wright, D.; Smartt, S. J.; Young, D. R.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Primak, N.; Schultz, A.; Gibson, B.; Magnier, E.; Waters, C.; Tonry, J.; Wainscoat, R. J.; Foley, R. J.; Jha, S. W.; Rest, A.; Scolnic, D.

    2016-08-01

    Two transients have been discovered as part of the Pan-STARRS Survey for Transients (PSST). Information on all objects discovered by the Pan-STARRS Survey for Transients is available at http://star.pst.qub.ac.uk/ps1threepi/ (see Huber et al. ATel #7153).

  6. Bright Transients discovered by PSST

    NASA Astrophysics Data System (ADS)

    Smith, K. W.; Wright, D.; Smartt, S. J.; Young, D. R.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Primak, N.; Schultz, A.; Gibson, B.; Magnier, E.; Waters, C.; Tonry, J.; Wainscoat, R. J.; Foley, R. J.; Jha, S. W.; Rest, A.; Scolnic, D.

    2016-08-01

    Six bright transients have been discovered as part of the Pan-STARRS Survey for Transients (PSST). Information on all objects discovered by the Pan-STARRS Survey for Transients is available at http://star.pst.qub.ac.uk/ps1threepi/ (see Huber et al. ATel #7153).

  7. Bright Transients discovered by PSST

    NASA Astrophysics Data System (ADS)

    Smith, K. W.; Wright, D.; Smartt, S. J.; Huber, M.; Chambers, K. C.; Flewelling, H.; Willman, M.; Primak, N.; Schultz, A.; Gibson, B.; Magnier, E.; Waters, C.; Tonry, J.; Wainscoat, R. J.; Denneau, L.; Stalder, B.; Heinze, A.; Sherstyuk, A.; Foley, R. J.; Jha, S. W.; Rest, A.; Scolnic, D.

    2016-04-01

    Seven bright transients have been discovered as part of the Pan-STARRS Survey for Transients (PSST). Information on all objects discovered by the Pan-STARRS Survey for Transients is available at http://star.pst.qub.ac.uk/ps1threepi/ (see Huber et al. ATel #7153).

  8. Advanced PFBC transient analysis

    SciTech Connect

    White, J.S.; Bonk, D.L.

    1997-05-01

    Transient modeling and analysis of advanced Pressurized Fluidized Bed Combustion (PFBC) systems is a research area that is currently under investigation by the US Department of Energy`s Federal Energy Technology Center (FETC). The object of the effort is to identify key operating parameters that affect plant performance and then quantify the basic response of major sub-systems to changes in operating conditions. PC-TRAX{trademark}, a commercially available dynamic software program, was chosen and applied in this modeling and analysis effort. This paper describes the development of a series of TRAX-based transient models of advanced PFBC power plants. These power plants burn coal or other suitable fuel in a PFBC, and the high temperature flue gas supports low-Btu fuel gas or natural gas combustion in a gas turbine topping combustor. When it is utilized, the low-Btu fuel gas is produced in a bubbling bed carbonizer. High temperature, high pressure combustion products exiting the topping combustor are expanded in a modified gas turbine to generate electrical power. Waste heat from the system is used to raise and superheat steam for a reheat steam turbine bottoming cycle that generates additional electrical power. Basic control/instrumentation models were developed and modeled in PC-TRAX and used to investigate off-design plant performance. System performance for various transient conditions and control philosophies was studied.

  9. The Palomar Transient Factory: System Overview, Performance, and First Results

    NASA Astrophysics Data System (ADS)

    Law, Nicholas M.; Kulkarni, Shrinivas R.; Dekany, Richard G.; Ofek, Eran O.; Quimby, Robert M.; Nugent, Peter E.; Surace, Jason; Grillmair, Carl C.; Bloom, Joshua S.; Kasliwal, Mansi M.; Bildsten, Lars; Brown, Tim; Cenko, S. Bradley; Ciardi, David; Croner, Ernest; Djorgovski, S. George; van Eyken, Julian; Filippenko, Alexei V.; Fox, Derek B.; Gal-Yam, Avishay; Hale, David; Hamam, Nouhad; Helou, George; Henning, John; Howell, D. Andrew; Jacobsen, Janet; Laher, Russ; Mattingly, Sean; McKenna, Dan; Pickles, Andrew; Poznanski, Dovi; Rahmer, Gustavo; Rau, Arne; Rosing, Wayne; Shara, Michael; Smith, Roger; Starr, Dan; Sullivan, Mark; Velur, Viswa; Walters, Richard; Zolkower, Jeff

    2009-12-01

    The Palomar Transient Factory (PTF) is a fully-automated, wide-field survey aimed at a systematic exploration of the optical transient sky. The transient survey is performed using a new 8.1 square degree camera installed on the 48 inch Samuel Oschin telescope at Palomar Observatory; colors and light curves for detected transients are obtained with the automated Palomar 60 inch telescope. PTF uses 80% of the 1.2 m and 50% of the 1.5 m telescope time. With an exposure of 60 s the survey reaches a depth of mg' ≈ 21.3 and mR ≈ 20.6 (5σ, median seeing). Four major experiments are planned for the five-year project: (1) a 5 day cadence supernova search; (2) a rapid transient search with cadences between 90 s and 1 day (3) a search for eclipsing binaries and transiting planets in Orion; and (4) a 3π sr deep H-alpha survey. PTF provides automatic, real-time transient classification and follow-up, as well as a database including every source detected in each frame. This paper summarizes the PTF project, including several months of on-sky performance tests of the new survey camera, the observing plans, and the data reduction strategy. We conclude by detailing the first 51 PTF optical transient detections, found in commissioning data.

  10. Transient infrared thermography for damage evaluation in aerospace composites

    NASA Astrophysics Data System (ADS)

    Pawar, S.; Peters, K.

    2010-04-01

    In this paper we investigate the performance of defect detection using long duration transient thermography for woven composite laminates subjected to low-velocity impacts. Two types of defects are studied: inclusions represented by foam tabs inserted into the laminate during fabrication and barely visible impact damage due to low-velocity impacts. These defects represent the expected damage states that are necessary for inspection during the service life of a woven composite aircraft component. The long duration transient thermography is demonstrated to successfully detect the embedded inclusions, with a dimension to depth ratio detection capability of approximately 3. It is also demonstrated that the detection of low velocity impact damage with the transient thermography is less successful due to uneven emissivity of the surface. Therefore, processing of the image using a self referencing algorithm is performed which improves the damage detection clarity.